Restorative Dentistry

Question 1

Define:

1. Functional occlusion
2. Mutually protected occlusion
3. Guidance (2 types, benefits of 1)

Answer 1

1. Absence of pathology and free from interference to smooth-gliding mandible movements
2. Gold standard. Canine guidance, posterior disclusion in excursion, no working/non-working side contacts, no protrusive interference
3. Anterior/canine - reproducible, protects posterior teeth
   Group function - occlusion of multiple working-side posterior teeth during excursion

Question 2

Occlusal forces

1. 4 features of normal
2. 4 features of parafunction

Answer 2

1. Forces directed down long axis of tooth, only for few mins/day, ICP in chewing and swallowing, light forces, protective NM reflexes prevent injury
2. Purposeless grinding and clenching. Forces may be horizontally directed, heavier forces, NM reflexes don’t work, long duration, damaging

Question 3

Posselt’s envelope of motion

1. Define
2. Draw shape and label diagram
3. Describe points
4. Define rest position
5. Define FWS

Answer 3

1. 3D concept of mandibular movement. Combination of border movements in all 3 planes
2. Draw and label shape
3. ICP - maximum interdigitation of teeth
   RCP - guided tooth position. First tooth-tooth contact on retruded arc of closure, when condyles are in their most superior anterior position in their fossa
   R - maximum opening position of rotation (when condyles are in their most superior anterior position in their fossa)
   T - maximum opening position of mandible. Condyles leave their fossa and slide over the articular eminence
   Pr - protrusion. Position when mandible pushed as far forward as possible, so lower incisors occlude anterior to upper incisors
   E - edge-to-edge. Position when upper central incisor incisal edges occlude with lower central incisor insical edges
4. Rest position - maxilla-mandibular relationship when patient relaxed and sitting upright. Teeth slightly apart (interocclusal clearance), TMJ in fossa
5. Difference between OVD and RVD/ICP and rest position. 2-4mm normal

Question 4

Veneers

1. 2 pros
2. 2 contraindications

Answer 4

1. Close/hide gaps and spaces, preferentially change shape/contour of teeth
2. Interproximal caries, severely rotated teeth, severe NCTSL, heavy occlusal contacts

Question 5

Onlays/inlays

1. 2 indications
2. 2 contraindications

Answer 5

1. RETT, # cusp, replace failing indirect restoration, posterior tooth with access difficulties
2. Active caries, active perio disease. Time-consuming, expensive

Question 6

Crowns

1. 2 pros
2. 2 contraindications
3. Principles of prep
4. 4 types and reductions for each

Answer 6

1. Protect weakened tooth structure, improve/restore function and aesthetics
2. Active caries, active perio disease, lack of tooth tissue remaining
3. Tooth preservation, resistance and retention forms (6 degree taper), structural durability, marginal integrity, preservation of periodontium, aesthetic considerations
4. Metal/cast metal - 0.5mm axial reduction, 0.5mm non-functional cusp reduction, 1.5mm functional cusp reduction, 0.5mm chamfer finish line

Feldspathic ceramic/PJC - 1.0mm axial reduction, 1.0mm non-functional cusp reduction, 1.5mm functional cusp reduction, 1.0mm shoulder finish line

MCC - 1.3mm axial reduction, 1.3mm non-functional cusp reduction, 1.8mm functional cusp reduction, 1.3mm labial/buccal shoulder (0.4mm metal + 0.9mm porcelain) and 0.5mm chamber (metal) finish lines

Core-strengthened ceramic (alumina/zirconia) - 1.5mm axial reduction, 1.5mm non-functional cusp reduction, 2mm functional cusp reduction, 1-1.5mm chamfer finish line

Question 7

Provisional restorations

1. 5 pros
2. 4 types
3. 2 pros/cons of custom
4. 2 pros/cons of preformed

Answer 7

1. Restore tooth characteristics, improve function, restore aesthetics, prevent sensitivity, prevent over-eruption, restore tooth as a functional unit
2. Custom (bis-acrylic resin), preformed (metal, plastic, polycarbonate)
3. Excellent fit, restores tooth to pre-prepared character; more expensive for patient, technique sensitive
4. Good for trauma cases/no pre-preparation impression, cheaper for patient; large bank required (more expensive), unlikely to fit accurately

Question 8

Restoration of endodontically treated tooth

1. Anterior options and indications
2. Posterior options

Answer 8

1. Composite/veneer - marginal ridge intact
   Crown - marginal ridge destroyed
2. Inlay/crown and composite core

Question 9

Residual dentine collar

1. Name
2. Define
3. Dimensions

Answer 9

1. Ferrule
2. Residual collar of dentine left after crown preparation that helps to prevent #
3. 1.5mm height and width

Question 10

Core

1. Define/function
2. 2 materials

Answer 10

1. Provides retention for crown, strengthens the tooth when there is an inadequate amount of sound tooth tissue remaining to retain a conventional crown
2. Composite, amalgam

Question 11

Post

1. Define/function
2. 3 ideal features
3. 3 types (2 features of each)
4. 4 placement considerations/ideal things to aim for

Answer 11

1. Placed in root, retains core. Does not strengthen/reinforce tooth (post preparation weakens tooth)
2. Parallel-sided (not tapered), non-threaded (passive), cement-retained
3. Fibre (bonds to dentine like composite, good aesthetics, radiolucent), ceramic (high flexural strength, good aesthetics, difficult to retrieve), metal (poor aesthetics, radiopaque, may cause root #)
4. 1:1 post/crown ratio, aim for longest/straightest canal, at least 1/2 of post into root, 4-5mm GP apically to maintain apical seal, <1/3 of root width

Question 12

Tooth whitening 1

1. 4 extrinsic/4 intrinsic causes of discolouration
2. What before bleaching
3. Process of extrinsic discolouration and bleaching
4. 4 gel constituents and functions
5. Max CP concentration

Answer 12

1. Extrinsic - smoking, tannins, CHX, iron supplements
   Intrinsic - fluorosis, tetracycline, amalgam/materials, loss of vitality
2. HPT/scaling
3. Discolouration caused by formation of chemically stable chromogenic products on tooth surfaces. Bleaching causes oxidation through H2O2. This causes the formation of smaller molecules, which are often colourless/not pigmented, as well as ion exchange with metallic molecules, leading to a lighter colour
4. Carbamine peroxide - active agent. Breaks down to form H2O2 and urea
   Urea - stabilises H2O2, increases pH
   Carbapol - thickening agent. Increases adherence of H2O2 to surface of tooth and slows diffusion into enamel
   Fluoride - desensitising agent, prevents erosion
5. 16.7%, breaks down into 6% H2O2

Question 13

Tooth whitening 2

1. 4 bleaching indications
2. 3 contraindications
3. 4 side effects
4. 4 reasons for sensitivity

Answer 13

1. Post-smoking cessation, tetracycline staining, fluorosis, age-related discolouration, non-vital, good RCT, no PAP
2. Painful sensitivity, G6PD deficiency, <16yrs, heavily restored tooth, smokers, amalgam staining
3. Sensitivity, gingival irritation, might not work, wears off/relapse, cervical resorption
4. Pre-existing sensitivity, increased concentration of bleaching agent, gingival recession, increased use time, method, frequency of change

Question 14

Tooth whitening 3

1. Name and describe 2 types of external vital bleaching
2. Describe non-vital bleaching
3. Describe how external cervical resorption occurs and how to prevent

Answer 14

1. Chairside - dam, apply bleach to tooth, heat/light/laser (dehydrates tooth, better initial effects), wash, dry, repeat
   Home - impressions for custom trays (1mm short of gingival margin, with buccal spacer); brush teeth, floss, load 1mm bleaching gel into buccal portion of trays, fit trays for 2hrs (ideally overnight), repeat
2. Remove restoration and GP to 1-2mm below ACJ, RMGIC coronal seal. Place 10% CP gel and cotton wool in coronal space, seal with GIC. Replace weekly, then restore palatal cavity
3. Diffusion of high concentration of H2O2 through dentine into perio tissues and application of heat. Prevent by using adequate RMGIC restorations at ACJ

Question 15

Tooth whitening 4

1. Describe combination bleaching
2. Describe micro-abrasion
3. 2 indications of micro-abrasion
4. 2 disadvantages of micro-abrasion
5. HCl substitution and why not as good
6. Regulations

Answer 15

1. Inside-outside. Internal non-vital + home external vital. Place GP in coronal space as well as in tray (create palatal reservoir). Replace frequently over the week
2. Removal of stained enamel (outer layer). Dam, apply 18% HCl and pumice mix to teeth, rub in with prophylactic cup for 5s/tooth, wash, dry, repeat, remove dam, fluoride prophy paste to seal tubules
3. Post-ortho demineralisation, mild fluorosis, dark staining pre-veneering
4. Over-use can result in yellowing of teeth (dentine showing through) or permanent sensitivity
5. Phosphoric acid etch. Only removes 10um vs. 100um. Etch (30s) prior to apply acid pumice mix for longer (30s/tooth)
6. OTC <0.1%. 0.1-6% - only dentists. Not for <16yrs except only where intended wholly for prevention of disease. >6% only where intended wholly for prevention of disease. >0.1% can be collected from dentist for home use after first cycle