BCS/Pulpal Disease Flashcards
Role of cementum in the spread of bacteria from pulp
Stops the bacteria and toxins spreading from pulp into dentine tubules and surrounding PDL.
Pulpal 1st/2nd line of defense
1 = odontoblasts make tertiary dentine 2 = inflammation and immune response at the apex/periapical area to stop bacteria going into the surrounding tissues.
What to check for in a pre-op assessment before RCT
Reference point Radiographic apex Number and shape of canals and roots Size of canals space e.g. is it patent Periapical pathology
Steps to a RCT
Access cavity - straight-line access Coronal 2/3 of pulp prep Full glide path Working length and master apical file Step back to shape the file. Apical guaging Obturate Cut back Restore
Chemical prep of the RCT aims
Lubricant for the instruments
Kill and remove bacteria and the smear layer.
Remove debris to stop the apex getting blocked
Dissolution of the pulp material and necrotic tissue so it can then be flushed away.
Disinfectant.
Aims of a RCT
Remove all the dead tissue and seal all the entry and exits, create a full glide path.
Why is rubber dam important for RCT
Protect surrounding tissues and teeth from the irrigant and bacteria. Can use oroseal too.
How to do a good access cavity for RCT
Check long axis of the tooth before rubber dam and follow the long axis. Remove all of the pulp roof and chamber so u can see all the way to the apex and it is straight-line access.
No ledges or overhangs and smooth axial walls and tapered shape. Can see all the orifices.
Instrument used for access cavity and coronal 2/3 of root prep
Diamond burs - pear and round
Rosehead burs - long shaft
Gates Glidden burs in different sizes, smaller as u get closer to coronal 2/3 of the canal.
Endo Z file - has a rounded blunt end so just used for shaping the access cavity e.g. doesn’t enter the pulp canal.
Benefits of a straight-line access and full glide path.
No ledges or perforations or transported axis. Easy instrumentation/less stress e.g. less chance of them breaking.
What is the working length
0.5-1mm short of the radiographic apex, at the apical constriction. Delta shape of apex means that you can’t see it radiographically but can feel it (tactile sensation)
Importance of getting the correct working length
Too long = bacteria and debris and irrigant pushed out of apex into the surrounding tissue, and the canal will end up being over-filled and the material will be recognised as foreign and cause an immune response.
How to determine the working length
- Paper points to working length - if they are wet or have blood on them then they’re too long.
- Radiographically by measuring the length.
- Place GP point or file (min 15mm to be seen radiographically) and check where it ends on the radiograph.
- Tactile sensation
- Electronic apex detector
How to find the master apical file size.
The biggest file that goes to the working length + 2 file sizes. Minimum will be 25mm because you need at least 15mm file size to see it on a radiograph.
Recapitulating
While prepping the canal. Each time u go up a file size, go back with a smaller file size to the working length to stir up the debris and stop it blocking the apex, and irrigate.
Apical guaging
To check if the master apical file fills the apical constriction:
- If u apply pressure, the master apical file doesn’t get pushed further down past the working length and should fit snuggle.
- A size larger file stops 1mm short of the working length.
Ideal properties of the irrigant
Non-corrosive to the instruments Non-toxic Removes organic and inorganic e.g. smear layer Kills microbes Antiseptic Antisepsis properties to stop bleeding for better visualisation Lubricant Dissolve pulp tissue
What is the irrigant normally used in RCT
1 to 5% sodium hypochloride - antibacterial and dissolves organic
17% EDTA removes inorganic material
What is the alternative irrigant used in RCT
Chlorhexidine 2%, if you are allergic to the other. Antibacterial but doesn’t dissolve organic or inorganic. Can’t be combined with sodium hypochloride bc it forms a toxic ppt.
Why is it important to remove the smear layer in a RCT
Bacteria and nutrients in the smear layer and it blocks the dentine tubules and reduced the quality of the bond when it is filled and if it breaks down later it leaves voids.
Can act as a barrier to irrigants.
The importance of inter-visit medication in RCT
Stops the bacteria proliferating and reduced the number of bacteria in the canal. Seals the canal so stops more bacteria or nutrients getting in.
Types of inter-visit medication
Non-setting calcium hydroxide and odontopaste
Non-setting calcium hydroxide as a inter-visit medication
Easy to apply and remove. Is temporary and begins to break down after 2 weeks. Very alkaline so denatures bacteria and proteins. Barium sulphate added so that it is radioopaque.
How to apply and remove inter-visit medication
Apply with paper points or k files. Remove by breaking it up using k-files or ultrasonic scaler with water and irrigate.
Odontopaste as an inter-visit medication
anti-inflammatory (steroids) so reduced post-op pain and antibacterial (antibiotics) so good for patients in pain.
What covers the inter-visit medication
Cavit or coltosol or sponge and then a temporary restoration (all easy to remove). Don’t use wool or cotton bc fibres track bacterial in and get stuck in the cavity.
Post-operative instructions after inter-visit medication applied.
Take NSAIDs and analgesics
The importance of obturating
Blocks all entries and exits from the pulp and fills the canal so bacteria and fluids can’t enter or proliferate. Prevent reinfection and seals everything in.
Obturation techniques
Cold-lateral condensation
Thermalplastic condensation - warm verticle or lateral.
Ideal properties of root canal filing material and an example
E.g. gutta percha
- Easy to place and remove
- Inexpensive
- Radioopaque
- Inert non-toxic etc
- Doesn’t change dimension on setting
- Insoluble in tissue fluid
- Can follow canal’s shape
- Stops leakages
- Compatable with other materials
- Long shelf life/stable
- Bactericidal
Root canal sealer uses
To fill voids, stick the GP points together and fill lateral canals. Lubricates and help the GP points move.
Cold lateral condensation
- GP point to working length and the same size as the master apical file. Tug back to check that it fits snuggly.
- Radiograph to check that it goes to working length.
- Sealer applied to walls of canal and tip of GP point.
- Finger spreaders used to push GP to the side of the canal and then a GP accessory point of the same size is inserted (+sealer at the tip).
- Repeat until can’t fit anymore accessory point.
- Take a radiograph to check for voids.
- Cut back the GP at the canal orifice
- Restore
When to take a radiograph during obturation and why
To check master GP file length
To check for voids
To review
Properties of an ideal RCT filling
3D and dense filling (no voids)
To full working length and no longer e.g. 1mm short of radiographic apex.
Smooth tapered shape
What form does GIC come in/what is it made of
Powder + liquid.
Liquid = soluble acid polymer
Solid = glass powder
How does GIC set
Acid/base reaction
Polymer dissolves in water and H+ ions released which attack the glass surface and release calcium and phosphate ions. These bind to the COO- on the acid chain and form cross-links and harden the mixture.
Dissolution -> gelation -> hardening
Properties of GIC
Strong bond to the tooth, doesn’t need moisture control, safe and biocompatible, F- releasing, antibacterial properties, doesn’t shrink when setting.
Poor aesthetics and poor wear resistance bc larger particles. Not good for incisal edges bc not durable/is brittle. Not command set so is technique sensitive.
Clinical uses of GIC
Class V or where moisture control is difficult.
Temporary restorations
Primary teeth
When aesthetics aren’t important
RM-GIC
HEMA monomers added
and photoinitiator. Sets by acid-base reaction and photo-polymerisation of HEMA monomers.
Polyacid modified resin composite
Normal resin composite but F- releasing glass particles added - need water to release F- so don’t act until much later and v slowly.
Advantages of resin composite
Bonds to tooth material = more conservative Better for environment and health Better aesthetics Strong and durable Chemically stable Safe to use Easy to place Command set Minimal tooth prep.
Disadvantages of resin composite
Less wear resistant Polymerisation shrinkage = leakages Need moisture control. Technique sensitive. Needs bonding system.
2 phases of composite resin and what they contain
Organic phase = methacrylate monomers, accelerators (faster reaction), stabilizers (for when not being used), inhibitors (stop normal light polymerising it).
Filler phase = filler particles (quartz or silica), photoinitiator.
Large filler size composite properties
Less wear resistance, poorer aesthetics, weaker bond to enamel surface and more shrinkage.
Nano filler size composite properties
Less shrinkage Stronger bond Better aesthetics bc small particles reflect light more Can be polished More wear resistant More homogenous mixture
Composite resin setting methods
Light-cured Chemical cured (activator and free-radical initiator)
How to classify composite resins
Filler size
Initiation/curing method
Viscosity
Clinical application
Adhesion benefits for composite resins
More conservative.
Can support the remaining tooth structure and undercuts.
Better adaptation to tooth material = less microleakage.
Allows for bevelled margins and better aesthetics.
Benefits of having beveled margins for composite restorations.
More surface area so more exposed tubules so stronger bond and better aesthetics bc junction between restoration and tooth tissue are less evident.
Indications for use of composite
. Can't create retentive features . Where aesthetics important . Incisal edges . Conserving tooth structure . Small cavities . If the patient allergic to metals. . Repairing enamel/dentine fractures and tooth wear
Contraindications for composite
. Can't have good moisture control . Not enough tooth structure to bond to . Too large restoration . Time constraints . Lots of force/pressure on restoration . Patients with high caries risk or grinding habits . If allergic to the materials.
How to acid etch
35% phosphoric acid for 20-30s
Benefits of acid etching.
- Removes pellicle layer so exposes enamel surface which allows for complete wettability bc enamel surface energy > adhesive surface tension.
- Removes contaminants
- Makes enamel surface rougher by partial desolation of HA prisms increases SA and undercuts and creates a more terentive surface so stronger bond to adhesive/more intimate contact.
Why does bonding area for composite restorations need to be kept dry
Water is polar and resin in not polar so if water was in the way it would stop complete intimate contact between resin and enamel so the bond would be weaker.
Steps to a composite restoration
- clean with pumice and slurry 30s
- wash and dry
- acid etch 20-30s
- wash and dry until a frosted white appearance
- apply bond
- light cure for 15s
- apply the composite in small increments and light cure for 30s in between.
Why is it important to clean before acid etch and what is the process
Clean with pumice and slurry and then rinse and dry.
To remove debris so that the acid can act on the enamel surface.
How to reduce shrinkage/stress in composite restorations
Reduce the C-factor (Configuration factor = bonded surfaces: open surfaces in the cavity. Large means more bonded surface so more stress and a higher C-factor).
Oblique packing for rebuilding cusps or curing in small increments.
Bulk fill composites and benefits
A Sonic device changes the viscosity of the composite and makes it more flowable. Better adaptation, less polymerisation shrinkage, better seal and better aesthetics.
Instruments used to finish and polish composite restorations
Finish with microfine diamond burs and polish with polishing strips and soflex discs.
Resin bonding to dentine benefits
- Seals the dentine tubules and enhances retention and strength.
- Stops internal gaps so stops hydrodynamic effect and post-op sensitivity/pain.
- Stops marginal gaps which allow bacterial invasion and secondary caries.
Problems/challenges with resin-dentine bonding
- Dentine is hard to dry/is hydrophilic whereas resin is hydrophobic so need a primer.
- Smear/pellicle layer needs to be removed
- Complex heterogenous substrate (dentine).
- Fluid flow from resin into tubules and to the pulp (toxic).
Dentine conditioner
Acid etch to remove the smear layer and to dissolve the dentine leaving a collagen meshwork.
Stronger etch/acid = wider tubules.
Dentine primer structure and example
A polar group that binds to the collagen/HA
A methacrylate group that binds to the resin via polymerisation
A spacer that is long enough to make molecule and bonds flexible so the bond is stronger.
E.g. HEMA
In a solvent that carries the monomers deep into the tubules and chases out the water and evaporates e.g. acetone.
Sealer
Binds to the primer and hardens to seal tubules..
Causes and negatives of polymer shrinkage
VdW bonds get replaced by covalent bonds during polymerisation so molecules are brought closer together = total shrinkage. Causes stress and tension on the tooth structure and can lead to bond failure and poor marginal adaptation = gaps.
Wet dentine bonding
Highly volatile solvent chases out the water and carries monomer deep into the collagen so don’t need to dry.
Drying too much collapses the collagen so weaker bond bc primer can’t go in.
3 stage dentine bonding
Etch -> prime -> seal. Most complicated and technique sensitive and lots of stages for error. Strongest bond.
2 stage dentine bonding
Etch + Primer = a good bond, simple and don’t need to dry. The etch dissolves the smear layer and the HA but the particles aren’t removed so remain in the hybrid layer and can weaken the bond.
Primer + sealer = still need to dry, weaker bond.
All in one dentine bonding
Easiest to use but weakest bond.
How can you increase amalgam restoration retention
Grooves Ledges Slots Amalgapins - need to have healthy surrounding dentine and not go into pulp or roots etc. Bonding
Bonded amalgam
Material that bonds to metal and tooth material e.g. HEMA.
Only sets in anaerobic conditions e.g. when under the restoration so good working times and sets as the amalgam is condensed into it.
Increases retention, less sensitivity and less iatrogenic damage.
Problems with bonded amalgam
Is soluble in saliva so dissolves out and leaves a gap.
Binds to metal matrix bands.
If some left uncovered then it won’t set.
Reduces mechanical strength of amalgam.
Classification of caries (not Black’s classification)
Early not detectable. Only detected by caries diagnosis aids. D1 = Non cavitated enamel lesion D2 = Enamel caries D3 = Enamel and dentine caries D4 = Enamel and dentine and pulp
Methods of diagnosing caries
Radiographically.
Tactile (for hard to see places, using blunt explorer).
Visually (need good lighting and dry, clean teeth).
Transillumination.
Electric (caries have more water and ions so altered electrical conductivity).
Interproximal imps.
Why is caries detection difficult
Hard to see areas
Different opinions
Early lesions hard to detect
DMF uses
Compare populations
Helps determine risk factors/causes and evaluate treatments and effectiveness.
Chart trends in caries.
DMF problems
Age-related
Cumulative, irreversible
Non-specific e.g. can’t tell between small restoration or active caries or crown.
Can’t add secondary caries or replaced restorations
Doesn’t take into account other reasons for tooth loss e.g. trauma.
Types of tooth tissue loss
Attrition Erosion Abrasion Trauma Enamel/dentine abnormalities
Aetiology of attrition
Grinding, malocclusion (cross-bite, class 3), crowns affecting opposing tooth, loss of posterior teeth (anterior do more work)
Aetiology of abrasion
Tooth brushing, nail biting
Aetiology of erosion
Diet, acid reflux, bulimia
Treatment of TSL
Diet advice, mouth guard, restore, fluoride
Effects of bad occlusion
Attrition, TMJ problems, tooth drifting, localised periodontitis/pulpitis, fractured cusps.
ICP and benefits
Max intercuspation bw upper and lower teeth. Protects anterior teeth bc less contact here.
What to use if ICP is unacceptable
Use CR
Anterior guidance benefits
Disocclusion of posterior teeth.
CR
The most superior position of the condyle in the fossa.
RCP
The first contacts when the mouth is closed from CR
Ideal occlusion
RCP = ICP
Dis-occlusion of posterior teeth when not in ICP
Force applied in axial direction e.g. not lateral.
Indications for preformed metals crowns
Primary teeth with RCT or some caries
Enamel/dentine abnormalities e.g. amelogenesis imperfecta (children and adults)
When can’t do other treatment e.g. amalgam can’t be used in under 15s.
Infraoccluded teeth (shorter crowns)
Contraindications for preformed metal crowns
Large caries
The tooth about to be exfoliated
Unrestorable teeth