CDS Restorative Flashcards
Treatment options for missing teeth
Leave space
Replace the teeth (denture, implant, bridge)
Close space through orthodontics
Why treat tooth loss? (4)
Aesthetics
Function - chewing
Speech
Health of other teeth (tilting, overeruption etc.)
Why is overeruption problematic?
The root surface becomes exposed, which is more sensitive and more susceptible to caries
Dental implants
False titanium roots surgically screwed into alveolar bone, left to heal then restored on top with bridge/crown
What is a bridge?
A prosthesis which replaces missing tooth or teeth and is attached to one or more natural teeth (or implants)
Can also be called a fixed partial denture
Limitation of bridgework compared with dentures
Bridgework does not usually replace soft tissue and bone, can include a little false gingivae
Types of bridgework
Adhesive
Conventional
Adhesive vs conventional bridgework
Adhesive - held on with wings on the palatal surface of teeth
Conventional - retained using crowns
Indications for bridgework
Function and stability
Appearance
Speech
Psychological - those reluctant to have removeable prostheses
Systemic disease - epilepsy
Cooperative patient - good OH, no active disease
Local indications for bridgework
Big teeth
Heavily restored teeth (for conventional)
Favourable abutment angulations
Favourable occlusion - not too heavy
Contraindications for bridgework
Uncooperative pt
Medical history of allergy to materials used
Poor OH
High caries rate
Periodontal disease
Large pulps (for conventional)
Local contraindications for bridgework
High possibility of future tooth loss within the arch
Poor prognosis of abutment teeth
Length of span too big
Ridge form and tissue loss
Tilting and rotation of teeth
Degree of restoration - how much tooth will be left after preparation
PA status
Bone loss
Abutment
A tooth which serves as an attachment for a bridge
Pontic
Artificial tooth which is suspended from the abutment teeth/tooth
Retainers (in bridgework)
The extracoronal and intracoronal restorations that are connected to the pontic and cemented to the prepared abutment teeth
What are connectors in bridgework?
Component which connects the pontic to retainers
Edentulous span
Space between the natural teeth that is to be filled by a bridge or partial denture
Saddle
Area of the edentulous ridge over which the pontic will lie
Pier
Abutment teeth which stand in between and support two pontics, each pontic being attached to a further abutment tooth
What is a unit in a bridge?
A retainer, pontic or a pier
Fixed-fixed bridge
Has a retainer at either side of the pontic (can be adhesive or conventional), joined by rigid connectors
Cantilever bridge
Retainer on one side of the pontic only (adhesive or conventional)
Names for resin bonded bridgework
Adhesive bridgework
Resin retained bridgework
Minimal preparation bridgework
Maryland bridgework
Resin bonded fixed partial denture
Metal used for adhesive bridgework wings
Cobalt chrome, nickel or chromium
Advantages of resin bonded bridgework
Minimal or no preparation
No anaesthetic needed
Less costly
Less clinical time
Can be used as provisional restorations (eg in children with hypodontia, as implants can’t be provided until finished growing)
If they fail, usually less destructive than alternatives
Disadvantages of resin bonded bridgework 6
Rigorous clinical technique, due to being resin retained, moisture control very important
Metal shine through
Chipping porcelain
Can debond
Occlusal interferences
No trial period possible
Indications for resin bonded bridgework
Young teeth (less destructive)
Good enamel quality - for bonding
Large abutment teeth surface area
Minimal occlusal load
Good for single tooth replacement
Simplify partial denture design
Contraindications for resin bonded bridgework
Insufficient or poor quality enamel
Long spans
Excess soft or hard tissue loss
Heavy occlusal contacts
Bruxists
Poorly aligned, tilted or spaced teeth
Contact sports?
Treatment planning for resin bonded bridgework
History - establish habits eg bruxism
Examination - clinical, dynamic occlusal relationships should be examined as well as stationary, periodontal health, radiographic examination
Study models - mounted on semi adjustable articulator and facebow registration, consider diagnostic wax up
Consider abutment teeth, occlusion and aesthetics
Patient cooperation and OH are important
Occlusal considerations for resin bonded bridgework
Bruxists, some don’t know - look for signs of attrition
Consider opposing dentition, contact points, over-eruption
Look at dynamic and stationary occlusal relationship clinically and on mounted study models
Direct resin bonded bridgework
Done chairside, there and then
Very useful in emergency situations, if a tooth requires immediate extraction or has been lost traumatically
Can be done using the patient’s tooth, acrylic denture pontic, polycarbonate crown or cellulose matrix filled with composite
How to treat a non restorable root fracture, with direct resin bonded bridgework
Extract tooth
Cut root off crown
Remove pulp and fill hole with composite
Etch contact points to adjacent teeth
Bond and put in situ
Apply small amounts of composite to the contact points
TEMPORARY solution until pt can have implant, denture or indirect bridgework
What is the difference between direct and indirect bridgework?
Direct - done chairside, there and then
Indirect - prostheses made in lab, requires impressions to be taken and lab work
Can require no, minimal or heavy preparation
Limitations of resin bonded bridgework
Need generous coverage on the palatal or lingual surface of abutment teeth - greater surface area of enamel covered = greater bond strength
Need good quality enamel for good bond
Should be kept supragingival, ideally 0.5mm
Care must be taken with coverage at incisal edge considering enamel translucency and shine through
Most common type of resin bonded bridge design anteriorly
Generally cantilever
Most common type of resin bonded bridge design posteriorly
Fixed-fixed
What are the issues with fixed-fixed resin bonded bridges in the anterior region?
One of the wings will often debond, ultimately resulting in caries underneath
Divergent guidance pathways - occlusal forces are directed down each anterior tooth in a different way due to the shape of the anterior arch
What are the considerations of existing restorations in abutment teeth for resin bonded bridgework?
Ideally sound enamel is needed to bond to
Bonding to composite can be ok, however consider replacing with newer composite or roughening the old one with slow speed
Amalgam will cause a compromised bond to chemically cured composite cement, consider replacing
Minimal preparation for cantilever resin bonded bridgework
Occlusal contact reduction (slight) especially if very heavy contact on abutment tooth
Cingulum undercut removal only, helps with path of insertion
Chamfer margin 0.5mm supragingivally
Mechanical retention of resin bonded bridgework
Rest seats/cingulum rests
Proximal grooves
Supra-gingival chamfer finish line ~0.5mm
Heavier preparation for cantilever design resin bonded bridgework
0.5mm reduction of entire surface
Cingulum rest
+/- proximal grooves
Chamfer margin (0.5mm supragingival)
Thickness of bridgework metal retainer wing
~0.7mm
Most likely time frame for failure of resin bonded bridgework
First 2 years, 5 year survival and 10 year survival stats very similar
Superfloss
Useful tool for cleaning under bridge pontics
Thinner and thicker parts
What should be used to cement resin retained bridgework?
Dual cure composite resin luting cement
Example Panavia21
Ideal size relationship between pontic and abutment tooth
Ideally pontic is smaller than abutment tooth
Cementation of resin bonded bridgework
Try in by holding with finger
Can request locating cleat on retainer, to check appearance and occlusion
Small bit of composite can be used but then requires cleaned off the surface, may require sandblasting again
Sandblasting
Used on fit surface of bridge retainer - cobalt chrome or nickel-chromium alloy has aluminium oxide particles of 50 micron thickness blasted at the surface
Roughens surface for increased bond strength
What kind of preparation is used for posterior resin bonded bridgework?
Often none
When required, occlusal rests ~2mm deep, 180 wraparound with chamfer finish line 0.5mm supragingivally, and occasionally proximal grooves
Temporisation for resin bonded bridgework
Direct bridgework
RPD
Essex retainer
If prep remains within enamel, no real need for temporary, sensitive toothpaste/duraphat or a thin layer of dentine bonding agent can help with sensitivity
When is it appropriate to use a longer span bridge such as 3-3 in the anterior region?
Not much occlusal contact such as class II incisor relationship
Advantages of conventional fixed-fixed bridgework
Robust design
Maximum retention and strength
Abutment teeth splinted together - good in cases of stable perio where still mobile
Can use longer spans
Lab construction is straightforward
Disadvantages of fixed-fixed conventional bridge designs
Preparation can be difficult - common path of insertion required
Removal of tooth tissue causes danger to pulp
If preparation is over tapered, retention is reduced
Problems when alignment of abutment teeth not parallel
Ideal taper for fixed-fixed conventional bridgework preparation
5-7 degrees
Cantilever conventional bridge advantages
More conservative tooth prep than fixed-fixed
Lab construction straightforward
No need to ensure multiple tooth preparations are parallel
Cantilever conventional bridgework design disadvantages
Only for short span (one tooth)
Rigid to avoid distortion - more prone to fracture
Mesial cantilever preferred (pontic more anterior)
What is the purpose of a fixed moveable bridge?
Solution for fixed-fixed designs where the abutment teeth are not aligned parallel to each other
What is a fixed moveable bridge?
Bridge comes in two components, pontic and one retainer with a dovetail in one path of insertion, then another crown for the other abutment tooth, with a slot. The two components have different paths of insertion but slot together.
Advantages of fixed-moveable bridges
Preparations don’t require common path of insertion, allowing more conservative tooth preparation
Each preparation is designed to be retentive independent of each other
Allows minor tooth movement
Can be cemented in two parts
Disadvantages of fixed moveable bridges
Limits length of span
Lab construction more complicated, can take longer
Possible difficulty in cleaning beneath moveable joint, as they are slotted not cemented together
Cant construct provisional bridge, could maybe do two provisional crowns on abutments and an essex retainer
Spring cantilever bridge
One pontic added to the end of a metal arm that runs across the palate to a rigid connector on the palatal side of a retainer. This was designed to try to conserve anterior tooth tissue. No longer used.
Advantages of spring cantilever bridge
Useful if spacing between upper anteriors present, where adjacent teeth are unrestored, and a posterior tooth would provide a suitable abutment, i.e. already has a crown or large restoration
Disadvantages of spring cantilever bridge
Can only be used to replace upper incisors
Difficult to clean beneath palatal connector
May irritate palatal mucosa
Difficult to control movement of pontic due to springiness of metal arm and displacement of palatal soft tissues
Abutment evaluation
Must be able to withstand the forces previously directed to the missing teeth
Supporting tissues should be healthy and free of inflammation
Crown to root ratio - length of tooth coronal to alveolar crest to length of rooth embedded in bone - optimum 2:3, minimum 1:1
Alternatives to bridges
Leave space
Denture
Implants
Why is it important to plan for retrievability when tx planning bridges?
Every restoration fails eventually
Clinical examination in bridge tx planning
History - presenting complaint, MH, SH, PDH
Clinical exam intra and extra oral - soft tissue, perio, caries, risk assessment, occlusion, parafunction
Abutment evaluation - sensibility testing, remaining tooth structure, radiographs
Important considerations in abutment evaluation
Sensibility testing
Remaining tooth structure
Radiographs
Healthy pulp or good RCT
PA health
Perio
Occlusal examination for bridgework tx planning
Examine intraorally and using study casts - facebow mounted on a semi adjustable articulator
Incisal classification, canine guidance vs group function
Consider overerupted opposing teeth
Parafunction?
Will bridge interfere with occlusion?
Considerations of radiographs of abutment teeth
Root configuration
Angulation/rotation of abutment
Periodontal health
Intra-oral exam considerations of abutment teeth
Surface area for bonding and quality of enamel
Risk of pulpal damage
Quality of endodontics - consider re-RCT
Remaining tooth structure - is there enough? Consider build up
Core - remove and rebuild
Bridge design process
Select abutment teeth - judge longevity of adjacent teeth
Select retainer - no prep, minimal prep, regular prep for RBB or full crown prep for conventional
Select pontic and connector
Plan the occlusion
Prescribe material
Pontic function
Restore appearance
Stabilise occlusion
Improve masticatory function
Factors influencing cleansability of pontic
Should always be smooth with highly polished or glazed surface
Surface should not harbour join of metal and porcelain
Embrasure space smooth and cleansable
Why is span relevant to thickness of bridge?
Longer the span, greater the thickness required to withstand occlusal forces
Occlusal surfaces of pontic
Should resemble those of the tooth it is replacing, narrower if possible to enable cleaning, should have sufficient occlusal contact
Approximal surface of pontic
Connector strength ideally 2x2mm
Embrasure space for cleansability
Wash through pontic
Also called sanitary or hygienic pontic
Makes no contact with soft tissue, functional rather than aesthetic, consider in lower molar area
Dome shaped pontic
Also called torpedo or bullet shaped
Useful in lower incisor, premolar and upper molar regions, acceptable aesthetically if occlusal 2/3 of buccal surface is visible, less suitable if gingival 1/3 is visible
Modified ridge lap
Buccal surface looks as tooth like as possible, but lingual surface is cut away, can have problems with food packing on lingual surface, but is quite easily cleaned
Ridge lap/full saddle
Greatest contact with soft tissue, may cause temporary blanching, good for not allowing food packing
Only for pts with good OH, care should be taken not to displace soft tissue
Ovate pontic
Good for good OH pts, best aesthetics
Gingivae mould into a divot
Sometimes need to initially prescribe an essex retainer with an ovate pontic in it
All metal options as materials for conventional bridgework
Gold - Great function, poor aesthetics
Nickel/cobalt chromium - cheaper
Stainless steel
Zirconia vs lithium disilicate for conventional bridgework materials
Zirconia is very strong, less aesthetic
Lithium disilicate is less strong, more aesthetic
Ceromeric material for conventional bridgework
Porcelain combined with composite
Not used much any more
Belleglass, vectris, targis
Where are metal materials most useful for conventional bridgework and why?
Lower posterior region
Lots of occlusal forces and lower aesthetic demand
Most common material used for conventional bridgework crowns
Metal ceramic
Compromise of strength and aesthetics
Benefit of materials becoming stronger, with regards to conventional bridgework tooth preparation
The preparation no longer needs to be as destructive as it once was
What can implant retained bridges be useful for?
Longer spans
Sequence of providing bridgework BEFORE tooth prep
Mounted study models
Consider diagnostic wax up and custom impression tray
Request lab to construct a vacuum formed stent - allows checking of reduction during tooth prep and allows construction of a temp bridge
Select shade before tooth prep and have lab made stent made or make pre-operative putty impression for provisional bridge
Order of tooth prep
Occlusal/incisal reduction
Separation of teeth
Aim for parallelism of tapered surface of each prep e.g. for 13 12 11
Mesial 11 then mesial 13
Distal 11 then distal 13
Labial 11 then labial 13
How to ensure parallelism of prep in the mouth
Direct vision with one eye closed
Large mouth mirror for posteriors
Use probe like a lab surveyor
What to do if unsure of parallelism of tooth prep
Quick impression
Pour model
Use lab surveyor
Retentive features that can be added to crown prep
Slots or grooves
When to consider adding retentive features to crown prep
Short clinical crown height
Overtapered
Sequence of providing bridgework after tooth prep
Confirm parallelism
Construct provisional bridge if using one
Make impression and occlusal registration
Temporary cement the provisional bridge
Demo cleaning with superfloss
Write/draw lab prescription, including pontic shape, shape, abutment teeth etc
Final bridge cementation
Cement for all metal conventional bridgework
Aquacem (GI luting cement)
RelyX luting (RMGI luting cement)
Cement for metal ceramic conventional bridgework
Aquacem (GI luting cement)
RelyX (RMGI luting cement)
Cement for adhesive resin bonded bridgework
Panavia 21
Cement for all ceramic conventional bridgework
NEXUS kit
What makes Panavia 21 a good cement for resin bonded bridgework?
It is an anaerobic dual cure resin cement with 10-MDP which helps tooth stick to metal
Are mesial or distal cantilevers preferred and why?
Mesial cantilevers preferred
Occlusal forces contact distally first, so if pontic is distal to cantilever retainer, this can mean that it is more likely to debond
When are distal cantilevers considered?
Shortened dental arch
Unopposed
Opposed by denture
Tooth surface loss types
Caries
Trauma
Developmental problems
Tooth wear
Physiological tooth wear
Normal wear associated with normal function and age
20-38um per annum
Pathological tooth wear
When the remaining tooth structure or pulpal health is compromised or the rate of tooth wear is in excess of what would be expected for the pts age
Also considered pathological if the pt experiences a masticatory or aesthetic deficit
Causes of tooth wear
Attrition
Erosion
Abrasion
Abfraction
Attrition
The physiological wearing away of tooth structure as a result of tooth to tooth contact
Which surfaces are affected by attrition?
Occlusal and incisal
Early appearance of attrition
Polished facet on a cusp or slight flattening of incisal edge
Appearance of attrition over time
Reduction in cusp height and flattening of occlusal inclined planes
Shortening of the clinical crown of the incisor and caning teeth
How does attrition affect restorations?
They show the same wear as tooth structure
Is attrition linked to parafunctional habits?
Almost always
Abrasion
The physical wear of tooth substance through an abnormal mechanical process independent of occlusion. It involves a foreign object or substance repeatedly contacting the tooth
Appearance of abrasion
Site and pattern of tooth loss is related to the abrasive element
Most common on labial/buccal surfaces, cervical on canine and premolar teeth
V shaped or rounded lesions
Sharp margin at enamel edges where dentine is worn away preferentially
Can manifest as notching of incisal edges
Most common cause of abrasion of cervical region of premolars and canines
Toothbrushing
Erosion
The loss of tooth surface by a chemical process that does not involve bacterial action
Caused by chronic exposure of teeth to acidic substances - intrinsic or extrinsic
Most common pathological tooth wear type
Erosion
Early stages erosion appearance
Enamel is affected, loss of surface detail, surfaces become flat and smooth
Erosion appearance after progression
Typically bilateral concave lesions without chalky appearance of bacterial acid decalcification
Dentine later exposed
Preferential wear of dentine leads to cupping
Increased translucency of incisal edges, can appear dark
What determines position and severity of erosion lesions?
Source, type and frequency of acid exposure
Effect of erosion on restorations
Amalgam and composite restorations stand proud of the tooth
Abfraction
Loss of hard tissue from eccentric occlusal forces, leading to compressive and tensile stresses at the cervical fulcrum areas of the tooth
Pathological loss of tooth substance at the cervical margin
Cause of abfraction
Biomechanical loading forces result in flexure and failure of the enamel and dentine at a location away from the loading
Disruption of the ordered crystalline structure of the enamel and dentine by cyclic fatigue
Crack in tooth substance cause tooth substance to chip out
Appearance of abfraction
V shaped tooth loss where the tooth is under tension, classically sharp rim at the amelo-cemental junction
Why is it important to determine the cause of tooth wear?
To help with prevention
Do males or females suffer more tooth wear?
Males (70% vs 60%)
History for tooth wear cases
Determine chief complaint - functional, aesthetic, pain?
MH
PDH
SH
How can taking a medical history help with tooth wear cases?
Can often give insight into the aetiology of wear, particularly erosion
- Medications with low pH
- Dry mouth
- Eating disorders
- Heartburn
- Alcoholism
- GORD
- Hiatus hernia
- Rumination
- Pregnancy
- Reflux
Why is social history relevant in tooth wear cases?
Lifestyle stress - bruxism
Occupational details - abrasive habits
Alcohol consumption
Diet analysis
Habits
Sports
Soft tissue indications of bruxism
Buccal keratosis
Lingual scalloping
Smith and Knight wear indices 0
No loss of enamel surface characteristics
Smith and Knight wear indices 1
Loss of enamel surface characteristics
Smith and Knight wear indices 2
Buccal, lingual and occlusal loss of enamel, exposing dentine for less than one third of the surface
Incisal loss of enamel
Minimal dentine exposure
Smith and Knight wear indices 3
Buccal, lingual and occlusal loss of enamel, exposing dentine for more than one third of the surface
Incisal loss of enamel
Substantial dentine exposure
Smith and Knight wear indices 4
Buccal, lingual and occlusal complete loss of enamel, pulpal exposure or exposure of secondary dentine
Incisal pulp exposure or exposure of secondary dentine
Bewe Basic erosive wear examination scores
0 No erosive wear
1 Initial loss of surface texture
2 Distinct defect, hard tissue loss <50% of surface
3 Hard tissue loss >50% of surface area
Risk level of BEWE cumulative scores of all sextants
None - less than or equal to 2
Low - between 3 and 8
Medium - between 9 and 13
High - 14+
Special tests that could be involved in tooth wear tx planning
Sensibility testing
Radiographs
Articulated study models
Intra-oral photos
Salivary analysis
Diagnostic wax up
Diet analysis
Which surface is recorded to give a BEWE score?
Most severely affected surface in a sextant
Immediate treatment phase for tooth wear
Deal with pain - desensitising agents, fluorides, bonding agents, GIC coverage of exposed dentine
Pulp extripation if wear has compromised pulp health
Smooth sharp edges - prevent trauma to soft tissues
Extraction - pain from unrestorable/non-functional tooth
TMJ pain
Initial treatment stage in tooth wear tx planning
Stabilise existing dentition
Deal with caries
Deal with perio
Oro-mucosal
Wear is important but treat the whole pt and whole mouth
Once you have a diagnosis and have identified the primary causative factor, institute a preventative regime, no point treating an ongoing problem
Wear indices examples
BEWE
Smith and Knight
Prevention of abrasion
Remove foreign object involved in causing the wear
Change toothpaste, alter toothbrushing habits, change habits such as nail biting or pen chewing
For toothbrushing abrasion use RMGIC (first choice), GIC, flowable composite or composite restorations placed with no tooth prep
Why are restorations useful for prevention of toothbrushing abrasion?
Patient wears through the restoration rather than tooth
Which material should be used for preventative restoration of toothbrushing abrasion lesions?
Ideally RMGIC as it has best survival rate
Can use GIC, composite or flowable
Composite may look better but higher modulus may compromise retention
Balance aesthetics and retention
Prevention of attrition
Generally more difficult to address as usually related to a parafunctional habit
CBT or hypnosis can be useful to reduce parafunction as a stress response
Splints - wear away instead of teeth, may break habit, soft ones can be used as a diagnostic aid
Which type of wear is unsuitable to be treated with a splint?
Erosion
Soft vs hard splint for attrition prevention
Soft - diagnostic device to show where wears faster
Hard - more robust and can be used longer term
Michigan splint
Popular hard splint providing ideal occlusion with even centric stops, has canine rise which provides disclussion in eccentric mandibular movements - canine guidance
Unsuitable patients for the Dahl technique
Active perio
TMJ problems
Post orthodontics
Bisphosphonates
If implants present
If existing conventional bridges
Most suitable pattern of wear for Dahl technique
Localised anterior
What material is most often used for the Dahl technique and why?
Composite
Better aesthetics, better compliance, easier to adjust, can be immediate definitive treatment
Which patient group has a faster rate of effect of the Dahl technique?
Younger
If no movement in ______ the Dahl technique is not going to work
6 months
Dahl technique
Method of gaining space in cases of localised tooth wear
(Originally using a removable CoCr anterior bite plane)
Palatal surfaces covered, allowing occlusion on raised cingulum, resulting in posterior disclusion and increase in OVD of 2-3mm
Occlusal contacts only on anteriors
Over 3-6 months you gain space between anteriors, anteriors intrude and posteriors erupt
Results in space between upper and lower anteriors for restoration without occlusal reduction
Surgical crown lengthening as treatment for wear
Exposes more of the crown for retention of final restoration
Repositioning of gingivae apically generally with removal of bone
Sensitivity
Still need occlusal reduction
Prevention of erosion
Even when erosion is not the best fit diagnosis for a toothwear case, it is likely to be part of the problem so should be considered in all cases
Dependent on the source of acid - intrinsic or extrinsic
Desensitising agents for symptomatic relief
Fluoride
Diet management
Habit changes
Control xerostomia
Anorexia/bulimia treatment
Control GORD, reflux, hiatus hernia
Discuss drugs with GMP
Proton pump rebound
If pt has taken PPIs for several months + it is possible that they may have rebound acid secretion and symptoms may get worse for up to two weeks when PPIs are stopped
This can easily be misinterpreted as a need for ongoing therapy
Prevention of abfraction
Assess occlusion on affected teeth - consider occlusal equilibration
Fill cavities with a low modulus restorative material - RMGIC and flowable
Passive management of toothwear
Prevention and monitoring
Should be the first part of any treatment of wear
Most patients will be in this phase for at least 6 months
For many patients this is all that is required
Active Management of tooth wear
Intervention threshold - when to progress to active management
Simple restorative intervention - covering exposed dentine, filling cupped defects in molars and incisors
The requirements for more extensive definitive restoration are not always clear - wear that leads to further complications, aesthetics beyond patient acceptability, leaving intervention may require more complex tx
The goal of active management of tooth wear
Preservation of remaining tooth structure
Pragmatic improvement in aesthetics
Functioning occlusion and stability
Active management of maxillary anterior tooth wear depends on 5 factors
Pattern of the tooth wear
Inter occlusal space
Space required for the restorations being planned
Quality and quantity of remaining tooth tissue, particularly enamel
Aesthetic demands of the patient
Categorisation of maxillary incisor wear
Tooth wear limited to the palatal surfaces only
Tooth wear involving the palatal and incisal edges with reduced clinical crown height
Tooth wear limited to labial surfaces
Types of maxillary anterior tooth wear cases where there is adequate inter-incisal space
If teeth wear rapidly and there is not time for alveolar compensation
Where there is an AOB
Where there is an increased overjet - in these cases there can be available space for restorations with no change in OVD
Which cases of maxillary anterior tooth wear are easiest to treat?
Thos with adequate inter-incisal space for restorations with no change in OVD
Why is there no increase in freeway space in most tooth wear cases?
There is compensation for the loss of tooth substance by dento-alveolar bone growth
Benefits and disadvantages of compensation for the loss of tooth substance by dento-alveolar bone growth
Maintains masticatory efficiency BUT leaves no space for restorations
Disadvantages of traditional method of tooth preparation to create space for traditional restorations in cases of tooth wear
Little tooth tissue to begin with
Poor retention due to short axial walls
Good chance of pulpal damage due to short clinical crowns
New materials offer a better, more conservative approach in these cases
Ways to make space for restorations in tooth wear cases
Increase OVD - multiple posterior extra-coronal restorations, reorganised approach, can be complex, destructive, expensive
Occlusal reorganisation from ICP to RCP - complicated, can be destructive, specialist treatment
Surgical crown lengthening - doesn’t really create more space
Elective RCT and post crowns - very destructive
Conventional orthodontics - lengthy treatment
Contraindications in anterior tooth wear for composite build up
Short roots (increasing crown to root ratio could cause orthodontic movement)
Reduced periodontal support due to periodontal disease
Lack of remaining enamel reduces the success rate significantly due to bond strength of composite to enamel
Composite bonding to minimally worn teeth with damage limited to palatal surface
Can be done with a high degree of confidence
First choice treatment in most anterior tooth wear cases
Composite bonding - non invasive
Ring of confidence
Remaining ring of enamel on worn tooth surfaces which has a very positive influence on retention of composite bonding
Is lower or upper anterior toothwear more difficult to treat?
Lower
Less enamel, smaller bonding area, more difficult moisture control
Composite bonding technique for lower anterior tooth wear
Possible to improve aesthetics but do not increase OVD
Do them before uppers
Same techniques as uppers
Wrap composite over and onto lingual surface
Treatment for cupping defects on posterior teeth
Fill with composite to protect dentine from erosion
Canine guidance in localised posterior tooth wear
Restorative care can be aimed at providing sufficient canine guidance to ensure posterior disclusion during lateral and protrusive movement
Composite resin added to the palatal of upper canines
Simple, effective and reversible technique, freehand or with diagnostic wax and template
Methods of composite build up
Direct build up with putty matrix
Clear vacuum formed matrix
Composite build up using putty matrix method
Alginate imps
Cast imps
Wax up build up on the cast
Take putty matrix of built up cast
Use matrix as template when placing composite build ups
Vacuum formed matrix method for composite build up
Alginate impression
Wax up on cast impression
Impression of this, cast in stone
Vacuum formed clear plastic matrix formed on this
Cut to size and use as mould for build up
Success of composite build ups for anterior tooth wear
Generally good pt satisfaction
Posterior occlusion normally re-achieved
Seldom TMJ problems
No detrimental effect on pulp health
No worsening of periodontal condition
Longevity of composite build ups for anterior tooth wear
Viable medium term option
Requires repair and maintenance
Maxillary restorations last better
No definitive figures, around 70% over 10 years
If they fail they can be replaced or repaired and no tooth destruction occurred during their placement
Why does maxillary composite bonding last longer than mandibular?
Increased bonding area, lower occlusal load, although tongue and saliva protect lowers
Information for pts on composite bonding for anterior tooth wear
Your front teeth will receive tooth coloured fillings to cover the exposed and worn tooth surface, preventing more wear
No, or minimal drilling, maybe LA
Add to tooth, no removal of tooth
Improved appearance should be possible
Bite will feel strange and might lisp or bite your tongue for a few days, chewing can be difficult
Only front teeth will meet, back ones will come together over 3-6 months
It is likely that posterior crowns, bridges or dentures will need replaced
Potential for debonding, replacement causes no damage
Maintenance will be required and will not be free forever
Categorisation of generalised toothwear
Excessive wear with loss of OVD
Excessive wear without loss of OVD but with available space
Excessive wear without loss of OVD and with no space available
Ideal first treatment option in generalised tooth wear
Adhesive approach first if possible
These can be used to asses the pts tolerance of a new occlusal scheme as a medium term restoration
If conventional preps are required later, these adhesive additions may form the bulk of the removed material, preserving tooth structure
Treatment of generalised excessive tooth wear with loss of OVD
Easiest but also least common
A splint can be used to assess the pts tolerance of the new face height - may not be necessary if adhesive approach used you can go straight in
Ideally half the OVD increase maxillary and half mandibular
Often a mixture of adhesive and conventional is required
Dentures may be required to provide posterior support at the new OVD
Treatment of generalised excessive tooth wear without loss of OVD, with available space
More complicated than loss of OVD to treat
Can involve occlusal reorganisation
A splint should be considered as an increase in occlusal face height is necessary
Most pt accommodate the increase
Restoration of anterior and posterior teeth then carried out at the new face height
If possible should involve minimal prep adhesive restorations
Treatment of generalised excessive tooth wear without loss of OVD, with no space available
Most severe and difficult to treat
Specialist opinion before treating
Attempt to increase OVD with splints or dentures if lack of posterior support
Crown lengthening surgery
Elective endodontics - destructive and post and cores do not go together with attrition
Ortho
Overdentures can be an option for these pts
Crown lengthening
Used to increase coronal tooth substance available
May result in black triangles between teeth where ID papilla is further down
Can lead to unfavourable crown to root ratio increasing chance of loosening or tooth movement if tooth loaded subsequently
Often post op sensitivity
Any subsequent conventional crown prep will be further down the root - problem if the tooth has a significant coronal-cervical taper, greater chance of pulpal damage
Overdentures
Preserve tooth substance and bone for support of denture when teeth are so worn down that restoration is impossible
Can be bulky for pt
Difficulties with keeping teeth and gingivae healthy underneath prosthesis
Record keeping of tooth wear cases
Where wear has been present for some time and not progressing, it is sufficient in most cases to record that it has been recognised, pointed out to pt and is being monitored
Advice must be recorded
If pt is not compliant, reluctant or unwilling to follow recommended course of action this must be recorded
Surface treatments such as topical fluoride must be recorded - important to record if pt complied with repeat applications
Discussions on consent must be recorded - pt must understand the proposed treatment, including passive prevention, as well as their part and how it is integral to a favourable outcome, must understand consequences of not following advice
Discussions on temporary treatment and this being explained, as well as the reason for not providing definitive at that time
Any referral documentation
Shortened dental arch
Kayser 1981
A dentition where most posterior teeth are missing
Satisfactory oral function without use of RPD
Priority given to maintaining an anterior and premolar dentition in one or both jaws
In the right circumstances, non replacement of posterior missing teeth can provide a stable and acceptable dentition
How many occlusal units are required for sufficient adaptive capacity to SDA?
3-5
What is an occlusal unit?
A pair of occluding premolars = one unit
A pair of occluding molars = two units
1992 WHO treatment goal for oral health
The retention, throughout life of a functional, aesthetic, natural dentition of not less than 20 teeth and not requiring recourse to prostheses
Indications for SDA appraoch
Missing posterior teeth with 3-5 occluding units available
Sufficient occlusal contacts to provide a large enough occlusal table
Favourable prognosis for remaining anterior and premolar teeth
Patient not motivated to pursue complex restorative plan
Limited financial resources for dental care
This strategy will only work long term if the remaining natural dentition can be preserved for the remainder of the lifetime of the patient
Contraindications for SDA approach
If there is a poor prognosis for remaining dentition
Untreated or advanced perio
Pre existing TMJDS
Signs of pathological tooth wear
The patient has significant malocclusion (severe class II or III)
Restore complete dental arch vs restore SDA
28 teeth, more complicated treatment at high cost, treatment results may be better
20-24 teeth, less complicated lower cost treatment, treatment results may be worse?
Considerations when tx planning SDA
Does pt have problems chewing?
Does pt have appearance concerns?
Does pt have discomfort such as traumatising gingivae?
Is there any evidence of occlusal instability as a result of the missing teeth?
Extra oral exam when considering pt for SDA
TMJ - click, crepitus, deviation, pain
Hypertrophy
Check skeletal relationship
Intra-oral exam when considering a pt for SDA approach
Check for signs of bruxism such as buccal keratosis, scalloping, trauma, wear facets, fractured restorations
Periodontal assessment
Occlusal assessment
Teeth of poor prognosis
Why are patient’s with a severe malocclusion unsuitable for SDA?
Not sufficient occlusal contact
Perio patient being considered for SDA
A course of non-surgical periodontal management should be planned if active disease
Therapy aimed at stabilising the periodontal condition of all remaining teeth
Evaluate response
Must be able to maintain perio health
What are the consequences of SDA approach in a patient with unstable perio?
Drifting of periodontally compromised teeth under occlusal load
Loss of alveolar bone leading to a compromised denture bearing area in the long term
Loss of space (neutral zone) for denture teeth in the long term
Consequences of distal tooth migration in SDA
Increases anterior load
Increases number and intensity of anterior occlusal contacts
Increased interdental spacing
This is exacerbated by inadequate perio support
Why is progressive tooth wear a contra-indication for SDA?
The long term threat this poses to survival of teeth
Gradual loss of occluding contacts and occlusal stability
Occlusal stability
The stability of tooth positioning relative to its spatial relationship in the occluding dental arches
or
The absence of the tendency for teeth to migrate other than the normal
Determining factors of occlusal stability
Periodontal support
Number of teeth in the arches
Interdental spacing
Occlusal contacts
Tooth wear
Typical effects in SDA of one or more teeth missing from arch
Tooth mobility
Tooth migration
Supra-eruption of unopposed teeth
Effects of distal tooth migration in SDA
Increased anterior load, in turn increasing the number and intensity of anterior occlusal contacts as well as the interdental spacing
Exacerbated when unopposed teeth and lone standing teeth have inadequate perio support
5 requirements of occlusal stability
Stable contacts on all teeth of equal intensity in centric relation
Anterior guidance in harmony with the envelope of function
Disclusion of all posterior teeth during mandibular protrusive movement
Disclusion of all posterior teeth on the non-working side during mandibular lateral movement
Disclusion of posterior teeth on the working side during mandibular lateral movement
Manifestations of traumatic occlusion
Fracture of restorations and/or teeth
Tooth mobility
Dental pain not explained by infection
Tooth wear
A traumatic occlusion may also be a contributing factor to TMJDS
TMD considerations for SDA approach
Does the pt have existing TMJDS?
Is this associated with tooth wear?
Loss of posterior support may be contributing to TMD
Replacement of missing teeth and correction of occlusal derangement may reduce TMD symptoms
Little evidence to support increased TMD problems with SDA
Extending SDA with resin bonded bridgework
Distal cantilever
Max one unit on each side of the arch
Light contact on cantilevered pontics in ICP
Minimal contact in excursive movements
Heavy contacts may lead to failure
Extending SDA with RPD
Bilateral free end saddle
RPI design
Consider with CU
Non-compliance
Conventional bridgework to extend SDA
Distal cantilever
One unit max on each side of arch
Light contact on cantilevered pontics in ICP
Minimal contact in excursive movements
Heavy contacts may lead to failure
Consider RPD
Implants to extend SDA
Single tooth in molar/premolar region with cantilever bridge
17 year old patient congenitally missing 22 and 23
Treatment options for filling the space
RBB
Removeable retainer with pontics
Implants
Assuming no relevant medical history, suggest 3 general factors to be considered before referring 17 year old with congenitally absent 22 and 23 for implants
Oral hygiene
Cost
Smoking
Amount of bone available
Perio history
That the patient understands what is likely to be included and is willing to comply
Three local factors assess for implant treatment planning
Width of alveolar bone
Space available between adjacent teeth
Bone height
Local perio
Smile line
Soft tissue adequacy
Gingival biotype
Plaque control
Three potential complications that you would warn patients about when consenting them for an implant retained bridge to replace 23 and 22 (congenitally missing)
Peri-implantitis or implant mucositis
Implant failure
Screw fracture
Crown or porcelain chip or fracture
Recession
Need for replacement
Tooth wear from the opposing dentition
Attrition
Tooth wear from acid
Erosion
Most common type of abrasion
Toothbrush abrasion
Tooth wear from a foreign object
Abrasion
Importance of aetiology in tooth wear
Allows attempt to reduce further wear
Plan for problems, contingencies and failure
Allows you and pt to be realistic
Identifies wider medical and wellbeing issues and allows signpositng
Prognostic indicator
Enhances consent process
Aids clinical diagnosis and treatment planning
What is meant by physiological tooth wear?
Normal amount of wear for the patients age
Modifying factors of attrition
Lack of posterior teeth
Occlusion - deep OB or edge to edge
Restorations
Erosion and abrasion
Stress and anxiety
Examples of occlusion that could make attrition worse
Deep OB - lower incisors
Edge to edge - localised wear
Common features of a bruxist
Significant wear throughout dentition
Repeated restoration failure
Root fractures
Often onset in early adulthood
Progressive
Lack of posterior support on attrition, and what can be done?
Often more rapidly progressive
Advise pts to wear a RPD
Very abrasive restorative material
Porcelain, especially if unglazed/unpolished
What evidence could be present of parafunction without obvious tooth wear?
Multiple cusp fractures on heavily restored teeth
Multiple cracks around restorations
Root fractures in unrestored teeth
Soft tissue trauma
Modifying factors of erosion
Lifestyle
Multiple factors
Amount and frequency
Level of control
Psychosocial
Intrinsic modifying factors of erosion
Eating disorders
GORD
Other medical conditions
Extrinsic modifying factors of erosion
Carbonated drinks
Sports drinks
Alcoholic acidic drinks
Citrus drinks
Acidic fruits
Acidic sweets
Pickles
Drugs - methamphetamines
Common features of carbonated drink intake
Incisal erosion on upper central
Cupping on lower molars
Palatal erosion on upper incisors
Sensitivity
Interproximal caries and buccal white spot/brown spot caries
Common features of eating disorders
Palatal erosion on upper teeth
Polished restorations - esp amalgam
Erosion around restorations
Sensitivity
Caries
Altered taste sometimes
Halitosis sometimes
Soft tissue changes
Abrasive behaviours
Toothbrush abrasion
Oral self harm (less common)
Tongue studs
Occupational
Unusual habits
Issues to consider in cases of toothbrush abrasion
Localised or generalised
Frequency and duration
Bristle and toothpaste abrasiveness
Electric v manual
Part of a combination wear problem eg eating disorder?
Part of a stress/anxiety related problem?
How can the effect of combination aetiology on rate of tooth wear progression be described?
Synergistic
Common combinations of tooth wear types
Erosion (extrinsic and intrinsic) attrition and abrasion
Erosion (extrinsic) and attrition
Erosion (intrinsic and extrinsic) and attrition
Common situations in which combination erosion (intrinsic and extrinsic), attrition and abrasion presents
Alcoholism and drug abuse
Eating disorder
Common situation in which combination extrinsic erosion and attrition may occur
Bruxist with a poor diet
Common case where erosion (intrinsic and extrinsic) and attrition combination wear may occur
Bruxist with poor diet and GORD
What type of tooth wear would you expect in alcoholism and drug abuse?
Erosion (intrinsic and extrinsic), attrition and abrasion
What type of tooth wear would you expect in a bruxist with a poor diet?
Erosion (extrinsic) and attrition
What type of tooth wear would you expect from a bruxist with a poor diet and GORD?
Erosion (intrinsic and extrinsic) and attrition
How to manage tooth wear with unknown aetiology?
Communicate a guarded prognosis
Difficult circumstances that may be uncovered during history for tooth wear
ED
Mental health issues
Abuse/harm/addiction
Vulnerable adult/child
Examination of tooth wear
Comprehensive
Use of indices ?
Try relate findings to aetiology
Remember tooth wear patients also have caries and perio disease
Tooth wear indices
BEWE - erosion
Smith and Knight
What does knowing aetiology of tooth wear allow you to do?
Make an individualised preventative plan
Reinforce the key messages
Signpost and refer to other health and social care
Review the aetiology control before definitive plan
Common preventative advice for tooth wear
Fluoride - high dose tp, alcohol free mw
Diet modification - frequency and quantity, method of delivery, elimination and addition
Remineralisation - tooth mousse
Tooth mousse disadvantage
Expensive
Possible interventions to control tooth wear aetiology
Toothbrushing instruction
Splint therapy
Signposting - CBT or hypnotherapy
Refer - GMP, psychiatrist, social services
What is the result of rehabilitating people with uncontrolled or partially controlled aetiology of tooth wear?
High failure rates
What can you see - Translucent central incisor edge, cupping defects cervical third central incisors labial aspect (looks like erosion), caries 22m, 26 large cracking amalgam, wear into dentine U3-3, combination attrition and erosion? L6s occlusal enamel lost, wear on premolars and anteriors through to dentine, tongue stud
What will you ask - fizzy drinks, symptoms - sensitivity, history of sensitivity, medical history - acid reflux, ED
Why do patients have a lack of posterior support?
Denture intolerance
Denture refusal
Supervised neglect
Why should complete dentures be avoided where possible in bruxists?
Bruxism does not stop, so
- Fractured dentures
- Ridge resorption
- Pain and ulceration under complete denture
(complete overdentures can be ok)
Overdenture
Any removeable prosthesis that rests on one or more remaining natural teeth, the roots of natural teeth and/or dental implants
Advantages of overdentures
Correction of occlusion and aesthetics
Support
Tooth wear management
Preservation of ridge form
Proprioception - keeping PDL
Denture retention
Can be used with precision attachments
Avoids extractions - MRONJ and ORN risk
Psychological benefits -still have natural teeth
Useful in elderly patients on polypharmacy
Eases transition to edentulism
Disadvantages of overdentures
Need for good oral hygiene
Increased caries and perio risk
Care homes - poor OH
Denture fracture - thinner acrylic
Discomfort/infection of roots
Medical history
Potentially more traumatic extractions of roots than whole teeth
Care of overdentures
Good oral hygiene
Fluoride toothpaste application to roots
Regular examination and radiographs of the roots
Denture hygiene particularly important
Benefit of transitional denture use in tooth wear cases
Can be used to increase OVD in cases of poor posterior support to create space for restorations
How are transitional dentures used in tooth wear cases with poor posterior support?
Transitional denture which increases OVD worn for a few months, if pt copes with transitional dentures AND increased OVD
1. Get rid of impossible teeth
2. Crowns with rest seats and undercuts
3. Definitive dentures with same OVD as transitional
Why are dentures in bruxists a problem?
High occlusal forces
Bruxists and CoCr dentures, and how can you manage this?
Teeth will fall off the saddle areas
Co/Cr backing so teeth occlude with metal
(must do wax trial before CoCr made)
What can be used to simplify small saddle areas?
Bridgework
When does conforming to the occlusion in a tooth wear case work best?
In a stable occlusion, with sufficient index teeth
(Ensure your prosthesis/restoration does not alter the occlusion)
When would you choose to change the occlusion in a tooth wear case?
Occlusion is unstable and there is a lack of sufficient index teeth
Usually more challenging to record occlusion
Decision on how much to increase OVD
Composite vs crowns for rehabilitation of tooth wear and changing OVD
Crowns are more destructive to tooth tissue and have a higher rate of failure
Planning tooth wear rehabilitation
Impressions and facebow
Mounted articulated casts on semi adjustable articulator (+/- surveying if making a denture)
High quality interocclusal record
Diagnostic wax ups
Stents - mock up - temporaries (if indirect)
Temporary (transitional) dentures
Clinical photographs
(radiographs)
Dahl type composite buildups
For severe anterior tooth wear
Upper 3-3 built up with composite to disclude the posteriors
Over a course of months the posteriors with over erupt and come back into occlusion
First line indirect restorations
Generally consider adhesive minimally invasive dentistry first
How much tooth structure needs to be remaining for fixed indirect restorations in tooth wear?
Usually 50% tooth structure remaining above gingival margin
Tooth preparation for indirects in tooth wear
Usually very difficult due to lack of occluso-gingival height
Lack of occlusal space
Severely compromised tooth
Possible modification techniques for tooth preparations in tooth wear cases
Materials
Grooves
Inlays
Ferrule
Parallel preps
Margins and occluding surfaces
Cores
Electrosurgery
Surgical crown lengthening
Materials considerations for indirects in tooth wear
Metal is more ductile, porcelain more brittle BUT consider aesthetics
Metal on biting surfaces wherever possible
What is the purpose of inlay preps and grooves within crown preps in tooth wear?
Enhance resistance form and retention by reduction in radius of rotation
What is the Dental Practicality Index for?
Assessing restorability of teeth
What are parallel preps used for?
Improve retention
What is electrosurgery and what is it used for?
electric current is precisely applied to the soft tissues by electrodes to obtain cutting of tissues
Can be used to cut back gingivae in order to ensure accuracy of an impression for a crown
Consideration of metal ceramic crowns in tooth wear cases
Metal palatal surfaces - teeth should occlude with metal because there is not sufficient space
Metal preparation margin shape
Chamfer
Porcelain preparation margin shape
Shoulder
What is the purpose of curves in a tooth prep when using porcelain?
To not increase crack propagation through porcelain, and porcelain splitting off metal
In posterior MCC preps, are metal or porcelain margins preferable and why?
Less destructive, further away from the pulp
Chamfer finish helps retention
What is a last resort to create sufficient retentive crown preps in tooth wear cases?
Surgical crown lengthening
How long does it take for gingival margin to stabilise following crown lengthening surgery?
Around 3 months
What is the benefit of making narrow occlusal surfaces in pontics?
Avoids shear forces in lateral excursions
Why might you put more implants in a bruxist to replace the same number of teeth?
To spread the load
Why is dental demolition so common in tooth wear?
Lots of failure - many teeth involved are heavily restored, with very small occluso-gingival height and subject to high occlusal loads e.g. in bruxists
Necessary considerations before dental demolition
Be clear on benefits - health appearance or both
Be clear on risks - health appearance or both
Clarity and honesty about longevity and cycles of replacement
Adequate dental health risk assessment
Can you achieve health and aesthetic objectives
Balance risks v benefits
Appropriate information provision
Valid consent
Learn to say no and to refer
Operator safety in demolition
Visor for eye protection ESSENTIAL - porcelain fragments etc
Consider surgical glove wear and appropriate handling - potential sharp metal edges/failed posts
Patient safety during restoration demolition
Eye protection
Airway protection - dental dam, or tie floss around long span bridges if dam not possible
Comfort - suction
Fractured instrument and post perforating canal
Bridge
Two poorly root filled teeth
Apical radiolucencies
Silver points
What to use for porcelain cutting?
Coarse diamond
What to use for metal cutting?
Gold cutting bur
Basic technique for dental demolition of bridgework
Porcelain - coarse diamond
Metal - gold cutting bur
Cut the whole way up the buccal surface then use chisel to remove bridge
High volume suction for porcelain fragments
May have to cut onto occlusal or palatal if wont break off
May need to section horizontally
Zirconia - very hard to cut through
What can you used to dissolve GP in re root treatment?
Eucalyptus oil
Turpentine
Failing dentition
A dentition where deteriorating teeth, restorations or oral health or a combination of issues means a loss of adequate basic oral functions such as mastication and acceptable aesthetics is inevitable if untreated
Prevention of failure of tooth wear rehabilitation
Basic oral health messages
Individualised oral hygiene instruction
Individualised dietary advice
Individualised fluoride regime
Individualised habit advice and management
Information provision and documentation in records
Referral to other health and social care professionals
Assess response to preventative and oral health measures before embarking on advanced treatment
SPIKES for giving bad news
Set up the interview - mental and physical preparation
Perception - assess what the patient knows about the medical situation
Invitation - ask how much they want to know
Knowledge - give the medical facts
Emotion - respond to patients emotions
Strategy and summary - negotiate a concrete follow-up step
Keys to managing failure
Comprehensive history and exam
Thorough planning
Seek advice if needed
Prevention
Avoid overambitious treatment
Effective communication
Decision making and treatment planning around basic principles
Keep plans simple
Have an effective maintenance strategy and regularly reassess the situation
What is the main difference between the dental operator and dental nurse chairs?
Dental nurse chair has a ring to provide support and stability for the feet, allowing the nurse to sit higher and see over potential obstructions
What position should operator sit in?
Neutral or balanced - back upright
Feet on the floor
Thighs roughly parallel with the floor
Approx 90 degree angle at hip and knee
Shoulders relaxed
Move with the chair, do not bend, twist or stoop
Description of poor operator seating position
Not using back support
Stooping forward
Rounded shoulders
Feet balancing on the legs of the chair
DANGEROUS and UNSTABLE
How should dental nurse be seated?
Using back support
Straight back with relaxed shoulders
Thighs parallel to the floor
Feet supported by the ring providing stability
Hip should be parallel with patients shoulder
How much higher should dental nurse be positioned than operator?
2-4 inches higher
This enables them to see over obstructions
What is the operating zone for a right handed operator?
7-11 o clock
What is the static zone in operator positioning?
11-2
This area is across the top of the patients face so should be kept clear
What is the nurses zone with a right handed operator?
2-4
What is the transfer zone in positioning of operator and nurse?
4-7
Instruments and medicaments are passed in this area which is across the patients chest
When is indirect aspiration useful?
Access for the aspirator is limited or the aspirator obscures the view of the operator
Where is direct aspiration carried out?
Adjacent to the tooth/teeth being treated
Aspirator is best placed slightly distal to the toth to remove water/debris
Bevel should be adjacent to the tooth being treated
Remember to removed any excess fluid and debris gathering at the back but do NOT go over the centre of the tongue to access this area
Example of when indirect aspiration is required?
When working in the upper anterior region palatal aspect
most suitable material for a partial coverage (3/4) crown
Gold type III alloy
An acceptable range of taper for a crown preparation is
7-15 degrees
Why is it important not to encroach on the biologic width of the gingival attachment complex?
To avoid acceleration of irreversible periodontal tissue damage and recession
Name 4 principal considerations of a crown prep
Use of an atraumatic preparation technique
Optimal retention and resistance form
Control of the path of insertion
Conservation of tooth tissue
When to provide extra coronal restorations
To protect weakened tooth structure
To improve or restore aesthetics
For use as a retainer for fixed bridgework
When indicated by the design for an RPD
To restore tooth function - occlusion
How might a crown be involved in RPD design?
Rest seats
Clasps
Guide planes
6 principles of tooth preparation
Preservation of tooth structure
Retention and resistance
Structural durability
Marginal integrity
Preservation of the periodontium
Aesthetic considerations
Why do we aim to preserve tooth structure in crown prep?
To avoid weakening the tooth structure unnecessarily
To avoid damage to the pulp
Results of under preparation for a crown
Poor aesthetics
Over built crown with periodontal and occlusal consequences
Results of over preparation in crown prep
Pulp and tooth strength being compromised
Retention (crowns)
Prevents removal of the restoration along the path of insertion or the long axis of the tooth prep
Resistance (crowns)
Prevents dislodgement of the restoration by forces directed in an apical or oblique direction and prevents any movement of the restoration under occlusal forces
Influencing factors on retention and resistance of an indirect
Taper
Length of walls
Extra means of retention such as grooves or slots
Path of insertion
Ideal taper for crown prep
Ideal inclination of opposing walls 6 degrees
What is the effect of length of crown prep walls on retention?
Longer walls help prevent tipping displacement
Path of insertion (crowns)
Imaginary line along which the restoration will be placed onto or removed from the prep
Set before the preparation is begun and all the features of the prep must coincide with that line
Effect of path of insertion on retention
Retention is improved by limiting the number of paths of insertion
How is structural durability achieved in crown prep
Restoration must contain a bulk of material that is adequate to withstand the forces of occlusion
Achieved through
- Occlusal reduction
- Functional cusp bevel
- Axial reduction
What is shown here?
Crown prep with functional cusp bevel
Name each of the margin finish line configurations
Knife edge
Bevel
Chamfer
Shoulder
Bevelled shoulder
What type of crown margin is shown here?
Chamfer
What type of crown margin is shown here?
Shoulder
Ideal crown prep margins
Smooth and fully exposed to cleansing action
Placed where the dentist can finish them and the patient can clean them
Placed at gingival margin wherever possible
Biological width
Distance established from the junctional epithelium and connective tissue attachment to the root surface of a tooth
Acts as a natural seal protecting the tooth from infections and diseases
Average biological width
2.04mm
Factors influencing material chose for crown
Aesthetics
Destructive prep
Destructive to opposing teeth
(bruxists?)
Metal crowns axial reduction
0.5mm
Full veneer axial reduction
0.5mm
Gold crown axial reduction
0.5mm
Porcelain crown axial reduction
1mm
MCC axial reduction
1.3mm
All ceramic crown axial reduction
1.5mm
Occlusal reduction for metal crowns
Functional cusps 1.5mm
Non functional cusps 0.5mm
Occlusal reduction for gold crowns
1.5mm functional cusps
0.5mm non functional cusps
Occlusal reduction for porcelain crowns
1.5mm functional cusps
1mm non functional cusps
Occlusal reduction for MCC
1.8mm functional cusps
1.3mm non functional cusps
Occlusal reduction for all ceramic crowns
Functional cusps 2mm
Non functional cusps 1.5mm
Finish line for metal crowns
Chamfer 0.5mm
Finish line for porcelain crowns
Shoulder 1mm
Finish line for metal ceramic crowns
0.5mm chamfer where only metal required
1.3mm shoulder where both metal (0.4mm) and porcelain (0.9mm)
Finish line for all ceramic crowns
Chamfer 1-1.5mm
6 stages in crown prep
Occlusal reduction
Separation
Buccal reduction
Palatal or lingual reduction
Shoulder and chamfer finish
Check occlusal surface and clearance
How is occlusal reduction in MCC prep done?
Retain some occlusal morphology - cusps and marginal ridges
Use diamond tapered fissure bur, round or rugby ball shape bur
How is separation in crown prep done?
Use long tapered diamond bur with 5-10 degree taper
Interproximal margin follows gingival contour
How is buccal reduction for MCC done?
Use diamond tapered shoulder bur for first reduction plane
Fissure bur 2nd reduction plane - avoid buccal pulp horn
How is palatal/lingual reduction done for MCC prep?
1 plane for posteriors
Follow palatal contour for anteriors
Use diamond chamfer bur
How to do shoulder and chamfer finish for MCC prep?
Tungsten carbide tapered shoulder bur or fine diamond parallel should bur
Finish palatal chamfer margins to remove any lips of dentine
What is the most common reason for lab techs being unable to construct a crown?
Insufficient occlusal clearance
How is pcclusal clearance of a crown prep checked?
In ICP and in excursive movements
What is failure in Endo?
Presence of clinical signs/symptoms
Enlargement of existing periradicular lesion
Development of a new periradicular
Persistence of periradicular radiolucent lesion associated with a tooth that had RCT at least 4 years previously
What are the tx options for failed endo?
Monitor
Orthograde retreatment
Periradicular surgery
Extract +/- prosthesis
What influences the txp for a failed RCT?
Clinical factors
Patient factors
Indications for non surgical root canal retreatment
Intra radicular infection
New complex restoration with technically poor RCT
Loss of coronal seal
Principles of re root treatment
Remove restorative
Assess restorability
Remove all root filling
Assess anatomy
Refine/modify preparation
Complete treatment as with new case
How are insoluble resins removed in reRCT?
Ultrasonics
How to remove GP for re RCT?
Handfiles +/- solvent
Reciproc
Solvent for GP
Chloroform
Eucalyptus oil
What size of reciproc for reRCT?
R25 for narrow canals
R40 for medium
R50 for large canals
Why is it important to use solvent when removing GP for reRCT?
Results in much cleaner dentinal tubules
Name top-bottom
Bite fork
Transfer jig assembly
Reference plane locator
Earbow
What is the anterior reference point when recording a facebow transfer?
Approximate position of the infraorbital foramen
43mm apical to anterior incisal edge (ideally 12)
How to use bite fork?
With bite reg paste or rigid wax
When do you not conform to the original OVD?
Increase in vertical height is needed to make space for restorations
Tooth/teeth significantly out of position ie overerupted, tilted or rotated
A significant change in appearance is wanted
There is a history of occlusally related failure or fracture of restorations
Clinical stages of indirect restorations
Prep
Temporise
Impressions and registration
Cementation
How does tooth preparation affect the tooth?
Compromises aesthetics
Degrades tooth function - occlusal reduction, destabilises occlusion
Due to occlusal and interproximal reduction - sensitivity (exposed dentine), compromised coronal seal in RCT teeth
Purpose of provisional extra coronal restoration
Aesthetics
Stabilise occlusion
Prevent sensitivity from exposed dentine
Protect coronal seal of RCT teeth
Prevent microleakage/bacterial leakage
What are the consequences of poorly fitting and contoured provisional extra coronal restorations
Patient is unable to clean - caries and gingival inflammation
Poor moisture control
Gingival overgrowth
Desirable characteristics of provisional extra coronal restoration materials
Non irritant - to pulp or PDL
Low temp rise during setting
Dimensionally stable
Adequate working time and setting time
Adequate strength and wear resistance
Good aesthetics
Types of provisional restoration
Custom formed - bespoke, preferable, can be technically demanding
Preformed - standard shapes and sizes, adjust to fit chairside
What are custom resin provisional crowns made of?
Chemically cured bis-acrylic composite resin - protemp
Why should you make a temporary crown before impressions for the definitive restoration are taken?
To check that the prep is satisfactory
- Undercuts
- Sufficient reduction
Preformed provisional crowns types
Polycarbonate
Clear plastic crown forms - filled with composite
Aluminium
Stainless steel
What are the problems with preformed provisional crowns?
Unlikely to fit accurately - cervically, occlusally, interdentally
Large bank of crowns needed to accommodate variation - expensive
When are preformed provisional crowns particularly useful?
When no impression is taken before tooth prep e.g. trauma
Fixed pros
The area of prosthodontics focused on permanently attached dental prostheses
Such dental restorations are also referred to as indirect restorations
Veneers
Onlays and inlays
Crowns
Bridgework
Particularly important part of extra oral examination for txp in fixed pros?
Smile line
What parts of the occlusion is it important to examine when tx planning for fixed pros?
Incisor relationship
Excursions of the mandible
Canine guidance/group function
Why place veneers?
Improve aesthetics
Change teeth shape and/or contour
Correct peg laterals
Reduce or close proximal spaces and diastemas
Align labial surfaces of instanding teeth
What is the Gurel technique
Minimal prep for veneers
Wax up
Stend
Intra-oral mock up
Preparation into mock up (can use depth cut burs)
When not to use veneers?
Poor OH
High caries rate
Interproximal caries and/or unsound restorations
Gingival recession
Root exposure
High lip lines
If extensive prep needed (>50% of surface area no longer in enamel)
Labially positioned, severely rotated, overlapping
Extensive TSL/insufficient bonding area
Heavy occlusal contacts
Severe discolouration
Why restore teeth with inlays and onlays?
Toot wear cases - increaseOVD
Fractured cusps
Restoration of RCT tooth - onlays provide cuspal coverage
Replace failed direct restorations
Minor bridge retainers (not recommended
Why not use onlays or inlays?
Active caries or perio
Time - tooth prep and lab fabrication required
Cost
Why restore teeth with crowns?
To protect weakened tooth structure
To improve or restore aesthetics
For use as a retainer for fixed bridgework
When indicated by RPD design
To restore tooth function - eg restore in OVD
Why not restore teeth with crowns?
Active caries/perio
More conservative options available
Lack of tooth tissue for prep
Unable to provide post and core
Unfavourable occlusion
Why replace missing teeth?
Aesthetics
Occlusal stability - prevent tilting and overeruption of adjacent/opposing teeth
Function - mastication, speech
Periodontal splinting
Restoring OVD
Patient preference
Why not replace teeth with bridgework?
Damage to tooth and pulp
Secondary caries
Effect on the periodontium
Cost
Failure
Assessment of the RCT tooth
Coronal seal - restoration/crown - leakage/caries?
Amount of remaining tooth structure
Is the tooth restorable?
Can you isolate tooth with rubber dam?
Swelling
Sinus
TTP
Buccal sulcus - ttpalpation?
Mobility
Increased pocketing - perio and root fractures
Radiographic assessment of an RCT
Root filling - length, obturation quality, voids
Unfilled/missed canals
Shape of canal
Patency - fractured instruments, posts, sclerosis
Bone support
Crown to root ratio (1:1.5)
Pathology - PA radiolucency, healing, resorption, perforations
Potential problems with restoring RCTed teeth
Amount of remaining tooth structure - externally and internally
Lack of ferrule
Wide post holes
Endo complications - fractured instruments, perforations, short/extruded root fillings
Teeth more brittle after RCT
Coronal microleakage
Coronal microleakage
Ingress of oral microorganisms into the root canal system
Cause of RCT failure
Root filled teeth unrestored for 3months + should generally be re-root treated
Trim GP to ACJ and place RMGI over pulp floor and root canal openings
Lining should not be too thick, allowing remainder of pulp chamber for retention and restoration
When would you use a cast post and core?
No ferrule
What is a post/core?
Gains intraradicular support for a definitive restoration
Core provides retention for crown
Post retains the core
Posts do NOT strengthen or reinforce teeth
Prep of the root canal for a post weakens tooth
Why avoid posts in mandibular incisors?
Thin/tapering/narrow mesiodistal roots
How much root canal filling should be left when placing a post?
4-5mm apically
Width of a post
No more than 1/3rd of root width at narrowest point and 1mm of remaining circumferential coronal dentine
How much alveolar bone support should you have for a post?
At least half of post length into the root in bone
What is a ferrule?
A dentine collar - encirclement of 1-2mm of vertical axial tooth structure within walls of a crown
Helps prevent tooth fracture
(orthodontic extrusion or crown lengthening may be necessary to achieve this)
Characteristics of the ideal post
Parallel sides
Non threaded
Cement retained
Why are parallel sides better than tapered in a post?
Avoids wedging
More retentive
Why is non threaded better than threaded for posts?
Incorporates less stress to remaining tooth than threaded
Why used cement retained posts?
Less retentive than threaded but cement acts as a buffer between masticatory forces and post/tooth
Advantages of prefabricated posts
Only 1 visit required
No impressions and lab visit required
Chairside core build up
Immediate preparation of core
Large selection of designs and materials
What are these and name each one?
Post designs
Tapered smooth
Tapered serrated
Tapered threaded
Parallel smooth
Parallel serrated
Parallel threaded
Post materials
Metals - cast gold, SS, brass, titaniu,
Ceramics - alumina, zirconia
Fibre - glass, quartz, carbon
Properties of metal posts
Poor aesthetics
Root fracture risk
Corrosion
Nickel sensitivity
Radiopaque
Ceramic post material properties
High flexural strength and fracture toughness
Favourable aesthetics
Difficult retrievability
Root fracture common
Fibre post characteristics
Flexible
Similar qualities to dentine and bond to dentine with DBAs
Aesthetic
Retrievable
Radiolucent
Advantages of tapered prefab posts
Conservative
High strength
High stiffness
Disadvantages of tapered prefab posts
Less retentive than parallel or threaded
Recommended use of tapered prefab posts
Small circular canals
Precautions with tapered prefab posts
Avoid excessively flared canals
Advantages of parallel prefab posts
Good retention
High strength
Comprehensive system
Disadvantages of parallel prefab posts
Precious metal post expensive
Corrosion of SS
Less conservative
Recommended use of parallel prefab posts
Small circular canals
Precaution with parallel prefab posts
Take care during prep
Advantages of threaded posts
High retention
Disadvantage of threaded posts
Stresses generated in canal may cause fracture
Recommended use of threaded posts
Only when max retention is essential
Precaution with threaded post
Take care to avoid fracture during seating
Advantages of a custom cast post and core
High strength
Better than prefab
Disadvantages of custom cast post and core
Less stiff than wrought
Multiple appts
Complex
When are custom cast post and core recommended?
Elliptical or flared canals (non circular or extreme taper)
Precaution when using a custom cast post and core
Care to remove nodules before insertion
What type of restoration would provide cuspal protection and what are the benefits of this?
Crown or onlay
Coronal seal
Prevention of fracture
What is a core build up?
The internal part of the tooth is built up with restorative material to replace the lost tooth tissue
The core is prepared
It provides retention and resistance for definitive restorations
Core materials
Composite - most common
Amalgam
Glass ionomer
Composite as a core material
Good aesthetics
Bonds to tooth structure
Technique sensitive - moisture control required
Used with fibre posts
Amalgam as a core material
Tend to avoid as retention required
Poor aesthetics
Core cannot be prepared straightaway needs 24 hr to set
Avoid pinned amaglams
Glass ionomer as a core material
Not really used as it absorbs water and core expands in size
Nayyar core
Root treatment removed from the root canals
Amalgam packed into the canals and tooth built up
This provides retention for the amalgam
Cannot be prepared for 24 hours until amalgam sets
Methods of post removal
Masseran
Ultrasonic
Eggler device
Moskito forceps
Sliding hammer
Anthogyr
Problems in post removal
Cant remove it
Root fracture - immediate or delayed
Render tooth unrestorable
Post space too wide
Break post
Problems with posts
Perforation
Core fracture
Root fracture
Post fracture
Options when post perforation
Repair - internal or external (periradicular surgery)
Extract
What causes post failure?
60% restorative reasons
32% periodontal
8% due to endodontic reasons
Why is unified post and core preferred?
One less material interface
Design considerations of a post retained restoration
How long will the post be?
Is there a ferrule?
How wide?
3-5mm remaining GP
Is canal straight?
How much space for the core? - need to factor in the type of crown to be placed
Core design
Taper and length are important
6 degree taper
Length required - to allow 2mm clearance for MCC
Provisional restorations during provision of post/core restorations
Provisional post core crown - temp bond
Immediate denture?
Dressing - not aesthetic but might prevent leakage
Essix retainer
Para post - provisional post and para post drill and impression post
Gutta percha removal for post placement
Dental dam
Soft - solvent or heat
Glades gliddens to minimum size 3 (straight part of the canal only)
Use working length and rubber stopper on the gg
Essential to leave 3-5mm GP apical third
Check GP plug remains
How much GP should be left in a root canal prepared for a post?
3-5mm
Lab prescription for cast post/core
PLease construct cast post and core
Para post (colour)
Core 6 degree taper
Please leave 2mm space in occlusion for crown
Enclosed registration/opposing impression
Post/core try in
Check post space for temp bond
Irrigate 0.2% chlorhexidine
Dry paper points
Ensure fits around prep
Do you have enough occlusal clearance?
Post/core fit
Be careful not to fill post space with cement - may prevent seating
Use firm apical pressure
Get rid of excess
Can ask lab for provisional acrylic crown
Make sure no excess around when taking crown impression/fitting MCC
Osseointegration
A direct functional and structural connection between a load bearing dental implant and living (organised) bone
Primary and secondary
Primary osseointegration
Implant is anchored in bone due to frictional forces provided between osteotomy and dental implant design features
Secondary osseointegration
The process of a functional connection between bone and dental implant
Living bone grows onto the surface of a dental implant
Healing process following implant insertion
Days - granulation tissue in wound chamber
Weeks - immature (woven bone)
4w - collagen orientation
6-8w - mature tissue attachment
Months - mature lamellar bone
Supracrestal soft tissue of tooth vs implant
Tooth has more fibroblasts, less collagen and the collagen fibres are orientated perpendicular to root surface
Implant has less fibroblasts, more collage and the collagen fibres are orientated parallel to implant crown
Subcrestal soft tissue tooth vs implant
Tooth anchored to bone by periodontal complex bone/PDL/cementum and is capable of physiologic adaption - resilient tissue attachment
Implant anchored to bone by direct functional contact, no physiologic adaption present, rigid connection
Materials for dental implants
Ti
TiZr - increased strenght
Ceramic - Y-TZP yittra stabilised zirconia
True or false
Implant design has a significant effect on survival and success
False
Where are bone level implants commonly used?
Aesthetic zone
Upper anteriors
Where are tissue level implants usually used?
Where aesthetic demand less high
Posteriors
Factors in implant design
Material
Bone/tissue level
Tapered/parallel
Length and diameter
Tapered vs parallel implants
Tapered may provide increased primary stability in immediate placed
Tapered may be used where there is root convergence apically
What influences choice of implant length/diameter?
Site
Indication
Local anatomy
How do length and diameter impact implant survival?
High survival of narrow diameter and short <10mm implants
Why are implant surfaces sometimes treated and what are the methods?
To create roughness
Sand blasting/acid etch/plasma spray
How is roughness of dental implant surface described?
Smooth 0-0.5um
Mild 0.5-1um
Moderate 1-2um
Rough >2um
Primary aims of dental implant treatment
Replace missing teeth with aesthetic, functional and predictable restoration
Low rate of complications during healing and maintenance
Long term stability
Medications that can affect the success or survival of dental implants
SSRIs
PPIs
Bisphosphonates
Steroids
Radiotherapy
(poorly controlled diabetes)
Smokers who smoke <10 per day affect on implants
Medium risk
Smoking affects concerning dental implants
Reduces vascularity
Fibroblast/osteoblast function
PMN function polymorphic neutrophils
What are PMNs?
Polymorphic neutrophils
The most abundant innate immune cells, first defence against infection
Risks of placing implants in patients who are not skeletally mature?
Relative infra occlusion
Suboptimal aesthetics
Occlusal disharmony
Implant fenestration
High smile line
> 2mm ST show
Low smile line
lip covers >25% of teeth
Gingival phenotypes
Thick/thin
Flat/scalloped (low scalloped, medium scalloped, high scalloped)
How is gingival phenotype differentiated?
Probe visibility
Gingival biotype impacts on implants
Risk of recession, risk of implant visibility through tissues
Thick tissue more likely to scar and less likely to develop papilla
Factors in pink aesthetics
M-D papilla
Gingival zenith
Mucosal colour/deficiency
ST colour and texture
What is the most important factor in determining presence of papilla in implants?
Distance from the bone crest to the adjacent contact point
Relevant local anatomy for implant placement in the maxilla
Maxillary sinus
Nasal floor
Naso-palatine canal
Infraorbital nerve
Relevant local anatomy for implant placement in the mandible
Inferior alveolar canal
Mental foramen
Incisive canal
Lingual perforating vessels
Submandibular fossa
What is meant by prosthetically driven planning of dental implants?
Implants should be planned starting form the final planned prosthesis position
This should be taken into account when requesting special tests
3D implant positioning depends on
Implant system
Proposed gingival margin
Local anatomy
Prosthetic plan - cement vs screw
How far must implants be placed from adjacent teeth?
Minimum 1.5mm
Why is it important not to place implants too close to the adjacent teeth?
To lower risk of damage to the adjacent tooth and lower risk of bone necrosis and ST defect inbetween the implant and the tooth
How much tissue should you have labially/buccally when positioning implants?
Aim for >1mm bone or >2mm bone and soft tissue
Low risk gingival biotype for implants
Thick low scalloped
Medium risk gingival biotype for implants
Medium thick medium scalloped
High risk gingival biotype for dental implants
Thin high scalloped
Low risk shape of crown for dental implants
Rectangular
High risk shape of crown for dental implants
Triangular
Low risk bone level of adjacent teeth for dental implants
</=5mm to contact point
Medium risk bone level of adjacent teeth for dental implants
5.5-6.5 mm to contact point
High risk bone level of adjacent teeth for dental implants
> /= 7mm to contact point
Which is higher risk for implant placement
A vertical bone defect at the site or a horizontal bone defect at the site?
Vertical
What is considered early implant placement with soft tissue healing?
4-6 weeks
What is considered early implant placement with partial bone healing?
12-16 weeks
What is considered late implant placement in healed sites?
6 months +
Aids to implant planning
Study models
Diagnostic wax up
Surgical template
Clinical photos
CBCT
Surgical guide
Essix (provisional)
Types of implant retained prosthesis
Fixed - single/multi unit/full arch screw or cement retained
Removeable - stud, bar, ball, magnet retained
2 impression techniques for restoration of dental implants
Open tray impression
Closed tray impression
The choice depends on use preference and the clinical situation
Open tray impression techniques components
Impression post
Guide screw
Closed tray impression technique components
Cap
Post
Screw
Benefits of open tray impression technique
Colour coded components correspond to prosthetic connection
High precision impression
Clear cut tactile response for accurate positioning
Guide screw can be tightened by hand or with the SCS screwdriver
Closed tray impression technique benefits
Colour coded components correspond to prosthetic connection
No additional prep of tray
Cheaper
High precision impression
Clear cut tactile response for accurate positioning
Which has better retrievability - screw or cement retained implants?
Screw
Which has better retention - screw or cement retained implants?
Screw
Which complications are more common with screw retained implants than cement?
More susceptible to porcelain fracture and screw fractures or loosening
Which complications are cement retained implants more prone to than screw retained?
Peri implant inflammation - often due to excess cement
Which are more expensive - screw or cement retained implants?
Screw
Common causes of compromised tissue sites for implants
Post extraction defects
Trauma
Hypodontia
Periodontal disease
Thin biotype
Determinants of aesthetic outcome of implants
Bone volume and morphology
Space dimensions
3D implant position
Biotype
Operator skill and experience
Extrinsic causes of tooth discolouration
Smoking
Tannins - tea coffee red wine guinnes
Chromogenic bacteria
Chlorhexidine
Iron supplements
Intrinsic causes of tooth discolouration
Fluorosis
Tetracycline
Non vitality - blood products
Physiological (age changes)
Dental materials - amalgam, root filling materials
Porphyria - red primary teeth
Cystic fibrosis - grey
Thalassemia, sickle cell anaemia (blue, green, brown)
Hyperbilirubinaemia (green teeth)
First method of whitening for extrinsic staining
HPT
Two types of tooth bleaching
External vital bleaching
Internal non vital bleaching
(can be used together in non vital teeth)
Active agent in vital external bleaching
Hydrogen peroxide H2O2
Forms an acidic solution in water, breaks down to form water and oxygen
Free radical HO2 hydroperoxyl is formed - this is the active oxidising agent
Fast reacting oxidising agent
What is the active oxidising agent in vital external bleaching?
Free radical HO2
Vital external bleaching gel constituents
Carbamide peroxide
Urea
Surfactant
Calcium phosphate
Fluoride
Potassium nitrate
Flavour
Preservative
Pigment disperses
Carbopol
What is the active ingredient in vital external bleaching?
Carbamide peroxide
Breaks down to produce hydrogen peroxide and urea
What is carbopol in vital external bleaching?
Thickening agent
Slows the release of oxygen
Increases gel viscosity - stays where you put it
Slows diffusion into enamel
What is the purpose of urea in external tooth bleaching?
Raises pH
Stabilises hydrogen peroxide
What is the purpose of surfactant in external bleaching?
Allows the gel to wet the tooth surface
What is the purpose of potassium nitrate and calcium phosphate in external bleaching?
Tooth desensitising agents
What is the purpose of fluoride in external bleaching?
Desensitises tooth
Prevents erosion
What are the factors affecting bleaching effect in external vital bleaching?
Time - more time more effect
Cleanliness of tooth surface - cleaner better effect
Concentration of solution - higher con more and quicker effect
Temperature - higher temp quicker effect
Caution before external vital bleaching
Always check patient is dentally fit
Any leakage around carious cavity margins will lead to pulpal damage
What to do BEFORE beginning external vital bleaching treatment
Take an initial shade and agree it with the patient to record in the notes
Check that the patient is dentally fit
Warnings for patient regarding external vital bleaching (6)
Sensitivity
Relapse
Restoration colour
Allergy
Might not work
Compliance with regime
Two methods of external vital bleaching
Chair side
Home
Advantages of chair side vital bleaching
Controlled by dentist
Can use heat/light
Quick results for patient
Disadvantages of chair side vital bleaching
Time for dentist
Can be uncomfortable
Results tend to wear off quicker
Expensive
Chairside vital bleaching technique
Thorough cleaning of teeth
Rubber dam (at least gingival mask)
Apply bleaching gel to tooth
Apply heat/light
Wash/dry/repeat
Takes 30-60 min
Caution during external vital bleaching
Gingival protection
What % is home bleaching gel?
10-15% carbamide peroxide
(16.7% carbamide peroxide equates to 6% hydrogen peroxide which is the max legal strength)
What is the tray for at home bleaching?
0.5mm thick soft acrylic vacuum formed soft splint
Stopping 1mm short of gingival margin
Buccal spacer to allow for placement of gel
At home bleaching delivery appt
Full mouth cleaning/polishing
Fit trays and check extension and comfort
Instructions:
Brush and floss teeth
Load tray 1mm2 dot buccally on each tooth
Fit tray in mouth for at least 2 hours, ideally overnight
Give written instructions
Review at 1 week
How long do at home bleaching results take?
Most see a result 2-3 days
Normally reached maximum 3-4weeks
If no change in 2 weeks it is not going to work
With age related discolouration, which stains respond better than others?
Yellow/orange discolouration respond better than bluish/greyish
Indications for bleaching
Age related darkening
Mild fluorosis
Post smoking cessation
Tetracycline staining?
Problems with external bleaching
Sensitivity
Wears off
Cytotoxicity
Gingival irritation
Problems with bonding to tooth
Sensitivity from vital bleaching
Common 60%+
Worse initially, resolves 2-3 days post bleaching
Predictors of sensitivity from bleaching
Pre-existing sensitivity
High conc bleaching agent
Frequency of change
Bleaching method
Gingival recession
Why do some bleached teeth have problems with bonding?
Residual oxygen from the peroxide remains within the enamel structure initially
Dissipates over a short time, ideally delay restorative procedures for a week after bleaching
Why do non vital teeth become discoloured?
Dead pulp -> bleeding into dentine
Blood products diffuse and darken leading to grey discolouration
Indications for non vital internal bleaching
Non vital tooth
Adequate RCT
No apical path
Contraindications for internal non vital bleaching
Heavily restored tooth
Staining due to amalgam
Advantages of non vital bleaching
Easy
Conservative
Patient satisfaction good
Risks of internal non vital bleaching
External cervical resorption dur to diffusion of H2O2 through dentine into periodontal tissues
(High conc H2O2 and heat, history of trauma)
Technique for internal bleaching
Record initial shade
Rubber dam
Remove filling from access cavity
Remove GP from pulp chamber and 1mm below AGJ
Place 1mm RMGIC over GP to seal canal
Remove any very dark dentine
Etch internal surface 37% phosphoric acid
10% carbamide peroxide gel in cavity
Seal cotton wool over this
Seal with GIC
Repeat weekly
Until shade achieved or no change after 4 visits
How can you avoid root resorption with internal bleaching?
After removing GP to 1mm above the ACJ, place 1mm RMGIC over it to seal dentine
Roughly how often is retreatment of internal bleaching required?
Variable
~4-5 years
Once required shade is reached with internal bleaching..
Restore palatal cavity
Place white GP or similar
Restore with a light shade of composite
What is combination bleaching?
Inside-outside bleaching
Removed GP and cover with RMGIC
Make bleaching tray with palatal reservoir (instead of buccal)
Bleach placed in access cavity and in tray
Replaced frequently over about a week
Must wear tray whole time
Microabrasion
Removes discolouration limited to the outer layers of enamel
Combination of erosion (acid) and abrasion (pumice)
Indications for microabrasion
Fluorosis
Post ortho demineralisation
Demineralisation with staining
Prior to veneering if dark staining present
Microabrasion technique
Clean teeth thoroughly
Rubber dam
Mix 18% HCl and pumice
Apply to teeth
Gently rub with prophy cup 5 seconds/tooth
Wash
Repeat up to 10x
Remove dam
Polish teeth with fluoride prophy paste
Apply fluoride gel or varnish to help reharden and decrease sensitivity
RV 1 month
Advantages of microabrasion
Quick
Easy
No long term problems
Disadvantages of microabrasion
Acid
Sensitivity
Only works for superficial staining
Works much better for brown staining than white marks
Acid used for microabrasion
37% phosphoric acid or 18% HCl
(HCl removes 100 microns, phosphoric only 10 microns)
Medical contraindications for bleaching
Very rare
Glucose 6 phosphate dehydrogenase deficiency
Acatalasemia
(Because neither can metabolise hydrogen peroxide)
Medico-legal requirement for bleaching for U18s
Products containing or releasing between 0.1% and 6% hydrogen peroxide cannot be used on any person U18 except where such use is intended wholly for the purpose of preventing disease
Maximum H2O2 conc for bleaching
6% (16.7% carbamide peroxide)
Chemical process causing discolouration
Formation of chemically stable, chromogenic products within tooth substance
These are long chain organic molecules
Bleaching oxidises these compounds into smaller molecules which are often not pigmented
Resin infiltration
Treatment for discolouration
Doesn’t remove surface layer
Infiltrate the white area with resin
Changes the refractive index of the white area
Masks it and makes it look like surrounding enamel
Hydrophilic resin impregnation of the porous enamel surface
