Treatment Planning for Fixed Prosthodontics Flashcards
what is fixed prosthodontics
• The area of prosthodontics focused on permanently attached (fixed) dental prostheses
• Such dental restorations are also referred to as indirect restorations
because they are made in a lab mostly then cemented in
what are the types of fixed prosthodontic restorations
- Veneers
- Inlays and Onlays
- Crowns
- Bridgework
• Could maybe include posts and cores into this list as well
○ But this is kind of between fixed prosthodontics and endodontics territory
what is included in the history and examination
- Patient complaint (CO)
- History of presenting complaint (HPC)
- Past dental history (PDH)
- Past medical history (PMH)
- Social history (SH)
- Family history (FH)
- Extra-oral examination (EO)
- Intra-oral examination (IO)
what does the history and examination lead to
provisional diagnosis
what is included in the extra-oral examination
○ TMJ
○ Muscles of Mastication (MoM)
○ Lymph nodes
○ Symmetry
○ Lips - often over looked
what needs to be considered with regards to the lips
§ Vermillion borders
§ Commissures ~ corners
§ Smile line
what does a high lip line mean
□ High basically means you can see the zenith teeth and a bit of the gingiva is exposed
what does a medium smile line mean
□ Medium smile line means the vermillion border just touches the zenith of the teeth and can see a little bit of the interproximal gingival tissue as well between the teeth
what does a low lip line mean
□ Low lip line means the patient essentially hides the zenith of the teeth and hides a good chunk of the gingivae as well
what lip line is most beneficial in prosthodontics
In terms of prosthodontics a low lip line tends to be better as it hides a bit of the margins of the teeth as it can be quite tricky to get the margins of prosthetic teeth to look realistic so the more of that you can hide the better essentially
what is the gingival zenith
The gingivalzenithis the most apical aspect of free gingival margin
what is included in an intra-oral examination
○ Look at whole mouth first before individual teeth
○ Soft tissues
§ Buccal mucosa
§ Tongue
□ Lateral border
□ Dorsum
§ Sublingual tissues / floor of the mouth
§ Palate
□ Hard
□ Soft
§ Lips
what other examinations and tests would you do in when examining the patient
• Periodontal
○ BPE
• Dentition ○ Chart teeth § Present and missing teeth § Restorations § Caries
• Occlusion ○ Incisal relationship ○ Excursions of the mandible § Protrusion § Retrusion § Lateral ○ Canine guidance or group function?
• Inter-arch space
○ Want to make sure there is actually room to place these restorations
○ Look in both vertical and horizontal dimensions
• Inter-tooth space (mesio-distal)
what special investigations would you do
• Sensibility testing = to get an indication of the vitality of the teeth
○ EPT and thermal tests
• Radiographs
○ Caries ~ Restorability
○ Tooth fractures [root fractures]
○ Periapical pathology
○ Bone levels ~ Want to make sure the teeth are adequately supported as they are going to be subjected to more occlusal loads if a fixed prosthodontic is placed
○ Existing large restorations (direct or indirect)
○ Assessment of potential abutment teeth
• Study models
Allows you to further consider options (even if you have a pretty good idea of what you want to do)
• Facebow
○ Particularly if doing work on teeth that are involved in guidance (such as canines but then if the patient has group function then there will be several teeth involved)
○ Also want to get one of these if you are considering changing anything to do with the patient’s occlusion (such as contact points or even the occlusal vertical dimension [OVD])
• Diagnostic wax-up
○ Allows you to see what the finished result is going to look like
○ Also allows you to see how it may potentially function as you can look at the occlusal contact points
• Additional information
○ Diet diary
○ Plaque and gingivitis indices
○ Full mouth periodontal chart
§ Needed if the patient’s BPE chart comes back as 4 in any of the sextants
○ Clinical photographs
○ Microbiology, biopsy, haematology ~ more rare
§ If you get a patient and you are worried about any of these you would probably want to refer them to the oral medicine department
what are the 5 stages to think about in treatment planning
- Immediate
- Initial (disease control)
- Re-evaluation
- Reconstructive
- Maintenance
what is the immediate stage of treatment planning
- priority
○ Relief of acute symptoms
○ Consider endodontics and extractions
○ Consider immediate denture / bridge
want to sort out the pain
what is the initial (disease control) stage of treatment planning
○ Extraction of hopeless teeth
○ OHI and dietary advice
○ HPT
○ Management of carious lesions and defective restorations or provisional restorations
○ Endodontics
○ Denture design, wax up for fixed prosthodontics
what is the re-evaluation stage of treatment planning
○ Re-assessment of periodontal status, confirm denture / bridge design
○ Want to make sure our disease control stage worked
○ Check that there is no active disease so you are able to move on to doing the more complex dentistry
what is the reconstructive stage of treatment planning
○ Perio surgery
○ Fixed and removable prosthodontics
§ Shouldn’t be diving into these if the patient has poor oral hygiene and lots of carious lesions
what is the maintenance stage of treatment planning
○ Supportive periodontal care and review of restorations
○ Making sure treatment is a success
○ Making sure there is no new active disease
what are the different options in treatment planning driven by
- dentist
- patient
- medical factors
- costs
- time
- dental facts
how would the dentist and dental factors influence treatment planning
○ Has the knowledge about what is appropriate
○ Know what is most conservative
○ What is best and works long term
how does the patient influence treatment planning
depends on their preferences
how does medical factors influence treatment plannings
Might stop you from providing some of the options you would like to such an allergies to some materials
or maybe patient has medical problems that means certain treatments would not work as well for them or it would not be a good idea to carry out that treatment
how does time and cost influence treatment planning
○ Always factor into treatment planning
○ Fixed prosthodontics are more time consuming as they are made in a lab and need tooth preparations etc as well
○ Need more stages
○ Then if things don’t go to plan the treatment is prolonged again
what are some decisions that need to be made about teeth in poor conditions
- Keep the tooth or extract?
- If to be kept, what kind of restoration?
- What tooth preparation is necessary?
caries / fractures extending beyond where is the ultimate cut off point indicating the tooth is not restorable
beyond the alveolar ridge
Anything that fractures below or any caries extending beyond the alveolar ridge will not be able to be restored
Tooth needs extracted
if a tooth has a horizontal fracture running straight through the furcation of the tooth, is it restorable?
○ This cannot be restored, it will leak and cause the restoration to fail
○ Probably quite painful for the patient when they bite down on that tooth because the tooth will want to flex a little bit but it is now fractured
Needs extracted
if root canal treatment has left a tooth discoloured over time, what are the treatment options and what would be the best treatment?
Could opt for something like a veneer
- would still give a good aesthetic result
- Problem with a veneer is that it will eventually fail (after 5-10 years)
- After failure patient might have to opt for a crown then post crowns etc
= restorative sliding scale
)The longer you can avoid this sliding scale the better)
As this patient already has a root treated tooth the best option would be to do internal and external bleaching
- whitens the affected tooth - veneer treatment could be avoided
when can bridgework not be an option?
due to the degree of tooth loss
why place veneers?
○ Improve aesthetics
○ Change shape teeth and / or contour or colour
○ Correct peg-shaped laterals
○ Reduce or close proximal spaces and diastemas (especially in the midline)
○ Align labial surfaces of instanding teeth (if patient does not want orthodontic treatment)
what is a diastema
Diastema = space / gap between 2 teeth
what can the gurel minimal preparation technique help with
ideally want to remain in enamel when carrying out veneer treatment
This technique can help you to do this
what is involved in the gurel minimal preparation technique
○ Wax up
○ Stent
○ Intra-oral mock-up
§ Use the stent to create this using pro-temp
○ Preparation into mock up (can use depth cut burs)
§ Cut through the mock-up to the ideal veneer preparation you would want
○ Means any surfaces of the teeth that need prepared get prepared and any surfaces that don’t need preparation don’t get touched
= being more conservative
when should you not use veneers
○ Poor oral hygiene
○ High caries rate
○ Interproximal caries and / or unsound restorations
○ Gingival recession
○ Root exposure
○ High lip lines
§ Not absolute but proceed with caution
§ Work closely with technician to get good result
○ If extensive prep is needed
§ >50% of surface area no longer in enamel
○ Labially positioned, severely rotated and overlapping teeth
§ To try and align all of these teeth you would have to cut a lot of tooth tissue away to try and achieve the final result that you want
○ Extensive tooth surface loss / insufficient bonding area
§ Affects bonding
○ Heavy occlusal contacts
§ Not good for patients in class 3
§ Veneers will just fracture
○ Severe discolouration
§ Crowns might be better
§ Try bleaching first
if extensive prep is needed veneers are not a good option but what alternatives are available
Consider alternatives like: □ PJC □ DBCs □ MCCs Gives more mechanical retention Veneers rely heavily on a chemical bond to the tooth and this bond works best to enamel
why restore teeth with inlays / onlays
○ Tooth wear cases
§ Increase OVD - useful if this is what you want to do
○ Fractured cusps
○ Restoration of root treated teeth
§ Onlays provide cuspal coverage
§ Can use better materials with onlays
○ Replace failed direct restorations
○ Minor bridge retainers (not recommended)
in what patients might the OVD be decreased and why
May be decreased as a result of the patient constantly grinding away on their teeth
maybe patients with severe attrition and erosion
why would you not use inlays / onlays
○ Active caries and periodontal diseases
○ Time
§ Tooth preparation and lab work needed
§ If the patient just wants the treatment done and out of the way then there are other options that they may be better suited to such as a direct restoration
○ Cost
§ Using better, more expensive materials
why restore teeth with crowns?
○ To protect weakened tooth structure
§ If there has been extensive tooth surface loss
○ To improve or restore aesthetics
§ More destructive options than veneers
○ For use as a retainer for fixed bridgework
○ When indicated by the design of a RPD
§ Rest seats
§ Clasps - design undercuts
§ Guide planes - ensures single path of insertion and removal for the denture which means the denture is more retentive as well
§ Take advantage of patients who are being fitted with crowns and getting a denture as part of their treatment plan
○ To restore tooth function
Eg restore in OVD
why not restore with crowns
○ Active caries and periodontal disease
○ More conservation options available
§ Can always fall back on more destructive options
○ Lack of tooth tissue for preparation
§ In these cases can probably provide a post and core
§ Core gives adequate height to the tooth for the crown to sit on top & grip
§ Then the post itself will hold the core into the tooth
○ Unable to provide post and core
○ Unfavourable occlusion
what are the principles of crown preparation
- Preservation of tooth structure
- Retention and resistance
- Structural durability
- Marginal integrity
- Preservation of the periodontium
- Aesthetic considerations
preserving sound tooth structure avoids what
Weakening the tooth structure unnecessarily
Damage to the pulp
what are disadvantages of overpreparing the tooth
○ This thins the tooth tissue and the thinner the tooth is, the more likely it is going to fracture further down the line
○ The more tooth tissue you cut into, the more likely you are to jeopardise the health of the pulp (if the tooth was still alive in this case)
[Risk when preparing crowns that 1 in 5 teeth will become non-vital which would then potentially require root canal treatment]
what is the degree of preparation needed dependent on
what materials you will use
when can you get away with a thinner preparation and what is the advantage of this
Anywhere you have a material on the outside of your crown you can get away with a thinner preparation
advantage = more conservative
what is the problem with using porcelain and how does this affect its preparation
Anywhere where you are starting to put porcelain it needs to be thicker as porcelain is a brittle material so you need to thicken it up to ensure there is adequate strength
do you need to cover all the metal on both the buccal and lingual surfaces with porcelain?
You don’t really need to cover the metal part on the palatal / lingual surface as this is not really seen so doesn’t affect the aesthetics
Can just restrict the porcelain to the buccal surfaces
what does under preparation of the tooth result in
○ Poor aesthetics
○ Over built crown with periodontal and occlusal consequences
○ The lab will make the crown very thin and then it is more likely to fracture
[But then what most technicians will do is they will make the crown to the correct thickness so then when you put the crown on top of the tooth the tooth itself then becomes even thicker so that will result in the labial surface being quite bulbous so this makes the aesthetics poor and can also increase the biological width of the tooth at the gingival margin and cause gingivitis or periodontitis around the crowns]
what does over preparation result in
Pulp and tooth strength being compromised
Tooth itself more prone to fracture
what is retention
Prevents removal of the restoration along the path of insertion or the long axis of the tooth preparation
what is resistance
Prevents dislodgement of the restoration by forces directed in an apical or oblique direction and prevents any movement of the restoration under occlusal forces
Ie resists displacement along any other direction than path of insertion
what should the taper be
Ideal inclination of opposing walls 6˚
This determines the path of insertion
how many paths of insertions is ideal
Only want to create a single path of insertion to make sure it is more retentive
as well as taper, what other factors affect retention and resistance
• Length of the walls
• Extra means of retention
○ Grooves
○ Slots
[The crown can then lock into these]
how does the length of walls affect resistance and retention
- Longer walls interfere with tipping displacement
- Want as tall a preparation as you can get
Longer walls = better
why do you want as tall a preparation as possible
○ The reason for this is because if the crown is going to become dislodged it has a longer way to have to slide up the tooth before it lifts off the tooth
- If you have a shorter wall then the crown doesn’t have very far to slide before it reaches the top of the tooth and it can lift off
what is the path of insertion
Imaginary line along which the restoration will be placed onto or removed from the preparation
when is the path of insertion decided
Is set before the preparation is begun and all the features of the preparation must coincide with that line
what does the path of insertion usually follow
This usually follows the long axis of the tooth
It is not always the case because you sometimes get things like an overlying cusp from an adjacent tooth
if the path of insertion cannot follow the long axis of the tooth what are the options to overcome this problem
○ Option to just trim that bit of the tooth away ~ not ideal
○ Or to design where you want your path of insertion to be, change the angle to avoid the premature contact with occlusal contact of the adjacent tooth and the interproximal contact of the crown
how is retention improved
is improved by limiting the number of paths of insertion
what is the ideal taper
ideal taper of around 5-7˚
if a tooth has been over tapered what is the result
as a result the crown can slide off in several different ways = the number of paths of insertion have been increased
Retention is not as good
why must a restoration contain an adequate bulk of material
Restoration must contain a bulk of material that is adequate to withstand the forces of occlusion
Changes due to the material you are using ie can be thinner for metals, has to be thicker for ceramics
how can structural durability achieved through
○ Occlusal reduction
○ Functional cusp bevel
○ Axial reduction
what happens if you dont bevel the cusp and why is this a problem
- If you don’t bevel it you end up with a pointed area essentially ~ sharp
- A sharp area of tooth constantly subjected to occlusal forces may result in fracture of the restoration that is placed on top of the tooth
- Bevelling the functional cusp is just rounding it off and removing sharp internal lines
what is involved in axial reduction
Ideally want to reduce the tooth in two planes labially at least
- dont want to cut a labial face that almost reaches the pulp
- want to prepare the more cervical aspect in one plane, and then prepare the more coronal aspect in another plane
- best thing to do is to follow the natural contour of the tooth on the labial surface
A crown prep should essential be a shrunken down version of the tooth, ideally should be the same shape as what the natural tooth would be ~ don’t make a big flat cut into the tooth
what is involved in marginal integrity
Finish line configurations
what would you use to finish line configurations
a. Knife edge
b. Bevel
c. Chamfer
d. Shoulder
e. Bevelled shoulder
a lot of these are now outdated
you are most likely to only use the chamfer and shoulder
what is the difference between a chamfer finish line and a shoulder finish line
chamfer more rounded towards the tip and used predominantly for providing veneers or any restoration where the outside surface of the restoration is made from metal (ie the palatal surface when providing a metal ceramic crown)
shoulder used for ceramic for crowns
to preserve the periodontium, how should the margin of the restoration be
- Smooth and fully exposed to a cleaning action
- Placed where the dentist can finish them and the patient can clean them
- Placed at gingival margin whenever possible
- Placement of the margins sublingual may be required
when might placement of margins need to be sublingual
- Want to keep them supragingival where possible
- Around anterior teeth the supragingival margin becomes an aesthetic problem
- So either want to place them right at the gingival margin or in some case you might have to go slightly subgingival
if you do have to place the margin slightly subgingival to hide the margin, what do you need to be careful about
If you have to go slightly subgingival to hide the margin, be careful that you don encroach on the biological width
what is the biological width
Biological width = height from the most superior aspect of the alveolus to the base of the gingival sulcus
what problems will occur by encroaching the biological width
encroach on the biological width = you are going to get recession around the crowns and the patient is going to find this very difficult to clean as well
where can the margins of crowns be placed subgingivally
Can go subgingival for your margin and have it placed in the area of the sulcular epithelium, where it is still within the gingival crevice
the biological width contains what
junctional epithelium and connective tissue
what are aesthetic considerations
• Smile lines
○ High smile lines are more tricky and demanding for the dentist and the technician to get a good aesthetic result
○ Can get away with more in a patient with a low lip line
what needs to be considered with regards to choosing which material is best
○ Provides the best aesthetics
§ Will the restoration(s) be visible?
○ Has the least destructive preparation
○ Is least destructive to opposing teeth
○ Is best suited to bruxists
which materials provides the best results
§ Composite / ceramics have the best aesthetics
§ Metals are stronger / less brittle
§ Consider hybrids = metal ceramic crowns
what is the problem with crowns in patients with bruxism
§ Sometime patients who are bruxists have very tight occlusion
§ Although ceramics are brittle in thin section, they can actually cause tooth wear and can actually wear away naturally opposing teeth
§ Sometimes all ceramic crowns in upper anterior teeth are not good treatment options as they are just going to wear away their lowers
§ So in these cases it can be better to opt for a metal ceramic crown so they have the ceramic on the labial aspect (aesthetics) but the palatal aspect is then made of metal which is malleable / softer (even though it is stronger) so it won’t cause the same wear to the lower incisors
what are the reductions needed for all ceramic crowns: porcelain bonded to alumina or zirconia framework
axial reduction: 1.5mm
occlusal reduction
- functional cusps: 2mm
- non-functional cusps: 1.5mm
finish line: chamfer (1-1.5mm)
what are the reductions needed for metal crowns: full veneer gold crown
axial reduction: 0.5mm
occlusal reduction
- functional cusps: 1.5mm
- non-functional cusps: 0.5mm
finish line: chamfer (0.5mm)
what are the reductions needed for ceramic crowns: traditional porcelains
axial reduction: 1mm
occlusal reduction
- functional cusps: 1.5mm
- non-functional cusps: 1mm
finish line: shoulder (1mm)
what are the reductions needed for metal ceramic crowns
axial reduction: 1.3mm
occlusal reduction
- functional cusps: 1.8mm
- non-functional cusps: 1.3mm
finish line:
a) chamfer (0.5mm where only metal required)
b) shoulder (1.3mm = 0.4mm metal and 0.9mm porcelain)
why replace teeth using bridges?
• Aesthetics
• Occlusal stability
○ Prevent tilting and overeruption of adjacent and opposing teeth into spaces left by teeth that have been extracted
• Function
○ Mastication
○ Speech
○ Wind instrument players
• Periodontal splinting
○ Can stick teeth together essentially
§ Might have a patient with a sturdy tooth and a sligtly loose tooth as a result of periodontal disease so can sort out the periodontal disease and the tooth is still a bit loose can actually brace that tooth by providing a bridge between the two teeth together
• Restoring occlusal vertical dimension / OVD
○ Don’t want to be doing this solely on a bridge
○ Usually part of a bigger treatment plan that involves crowns and onlays as well
•Patient preference
They might not want dentures or implants
why not replace teeth using bridgework
• Damage to tooth structure and pulp (of remaining teeth)
○ Particularly in the case of posterior teeth, may have lost a tooth but overall not functioning any poorer as a result of missing this tooth
○ But patient might want the tooth replaced but one of the risks of this is having to cut into an adjacent tooth for a bridge which is then potentially jeopardising the health of that tooth so it would have been better for the patient to just leave the space
- Secondary caries risk
- Effect on the periodontium
• Cost
○ More expensive treatment options
• Failures
○ Prone to failure
○ Good success rate
name bridge designs
• Cantilever
○ Bridge is just held onto an adjacent tooth on one side
• Fixed-fixed
○ Prosthetic tooth is held on by two restorations on either side
• Adhesive / resin-bonded / resin retained
○ Just have a little wing that bonds onto the tooth next to the space to hold the prosthetic tooth in
• Conventional
○ This just means that the thing holding the prosthetic tooth on is a crown
• Hybrid
○ Mix of the two
○ Metal wing (adhesive) on one tooth and a crown (conventional) on the other
• Fixed-moveable
○ Fancier - more in later bridgework lectures
• Spring cantilever
○ Old fashioned design, probably will be rare to see this
○ Bridges where you have a crown on a posterior tooth that has a metal arm that goes all the way along the palate and then holds onto a prosthetic tooth at the front
how do you communicate with patients
verbal
written
what is involved in informed consent
ie what does the patient need to be informed of before giving consent
• Invasiveness / reversibility
○ Anything with cutting teeth is irreversible
• Likely longevity and success rates (evidence based)
○ How long can they expect to have these restorations for
○ The only thing you can guarantee the patient is that the restorations will fail at some point
• Possible complications
○ Bits of porcelain fracturing off
○ Crowns becoming dislodged
○ Need to make patients aware of those things
• Time involved
• Costs
○ This might drive what the patient actually allows you / permits you to provide
• Alternative options
○ “we can provide crowns but actually veneers are a bit more conservative”
○ “what you are looking for in terms of aesthetics might be achievable with something simple like bleaching or a little composite placement”
• What treatment is to be performed
• Why is it necessary
Consequences of not having treatment
