Prosthodontics

Question 1

Cawood and Howell ridge classification

Answer 1

1. I - dentate
II - post-extraction
III - broad alveolar process
IV - knife edge
V - flat ridge

Question 2

Support

1. Define
2. 2 from maxilla
3. 3 from mandible (anatomical landmark of one)

Answer 2

1. Resistance to occlusal directed forces
2. Hard palate, residual ridge
3. Retromolar pad, residual ridge, buccal shelf
   Retromolar pad - triangular soft tissue (pear-shaped) pad of tissue at posterior end of edentulous ridge, anterior to ramus of mandible

Question 3

Retention

1. Define
2. 2 from maxilla
3. 2 from mandible (muscle adjacent to one)

Answer 3

1. Resistance to vertical displacement
2. Post dam, border seal (into functional sulcus)
3. Retro-mylohyoid space, border seal (into functional sulcus)
   Retro-mylohyoid space - distal end of lingual sulcus (posterior to mylohyoid and medial to medial pterygoid)

Question 4

Stability

1. Define
2. 2 from maxilla
3. 2 from mandible

Answer 4

1. Resistance to horizontal displacement
2. Residual ridge, neutral zone, arch of palate
3. Residual ridge, neutral zone, retro-mylohyoid space

Question 5

Denture anatomy

1. Posterior border anatomy – 3 things (describe location of one)
2. 2 reasons for relief
3. 4 poor denture bearing areas

Answer 5

1. Hamular notches, palatine fovea anterior to vibrating line, HSPJ
   Hamular notch - between distal surface of tuberosity and the hamular process of the medial pterygoid plate
2. Bony prominences (tori), high frenal attachment
3. Flabby ridge, atrophic mandibular ridge, bony prominences (tori), high frenal attachment, dry mouth

Question 6

Design stages

Answer 6

Patient/denture assessment, primary impressions, master impressions, jaw registration, tooth trial, delivery, review, aftercare

Question 7

Primary impressions

1. 3 key things
2. 2 materials (2 benefits of one)
3. Disinfection process

Answer 7

1. Adequate surface reproduction, cover denture-bearing anatomy, good peripheral seal, suitable to produce satisfactory cast
2. Alginate - cheap, easy to use, elastic, accurate
   Impression compound
3. Rinse off saliva/debris, place in Perform for 10 mins, rinse off Perform, place in bag with damp paper towel, take to lab along with prescription for casting

Question 8

Master impressions

1. 2 other names
2. 3 key things
3. 2 materials (2 benefits of each)
4. Occlusal stop function

Answer 8

1. Secondary/definitive impressions
2. Good surface reproduction, cover denture-bearing anatomy, good peripheral seal, suitable to produce master cast
3. Alginate - cheap, easy to use, elastic, accurate
   Polyether - hydrophilic, very accurate, easy to use
4. Allow accurate correction of posterior borders of tray and will pre-form for impression material

Question 9

Jaw reg

1. 2 reasons for
2. 5 things to record
3. 6 stages
4. What data to include on jaw registration

Answer 9

1. Determine occlusal plane, determine jaw relationship, define shape of maxillary rim, define position of lower teeth, select shade and mould
2. Extension, retention, stability, occlusion, aesthetics
3. Adjust upper record block, lip line and occlusal plane, measure vertical dimension and establish face height, lower tooth position, registration, tooth selection
4. Lip line, centre-line, incisor line (incisal plane), occlusal plane, canine line

Question 10

Define:

1. Balanced occlusion
2. Balanced articulation
3. Neutral zone
4. Christensen’s phenomenon and how to prevent

Answer 10

1. Simultaneous bilateral contacts between teeth in anterior and posterior occlusal areas of the jaw when static
2. Continuing simultaneous, bilateral contacts between as many artificial teeth as possible during excursive (lateral and protrusive) movements of the mandible
3. Stable tooth position where the forces exerted by the muscles of the tongue equal/balance forces exerted by the muscles of the lips and cheeks
4. Gap occurring in natural dentition/between opposing posterior flat occlusal rims when mandible protruded (posterior disclusion).
   Can cause denture instability and is resolved using compensating curve

Question 11

Hanau’s quint

1. Define
2. 5 components

Answer 11

1. Factors/determinants affecting the setting of teeth for balanced occlusion
2. Sagittal condylar guidance angle, incisal guidance, cusp height/inclination/angulation, orientation of occlusal plane, compensating curve

Question 12

PMMA

1. 1 pro
2. 1 con
3. 2 finishing methods
4. 5 finishing issues and define

Answer 12

1. High softening temperature
2. Poor thermal conductivity
3. Dough-packing, injection-moulding
4. Gaseous porosity - due to monomer boiling (small bubbles/air blows in thick sections of base)
   Contraction porosity - due to insufficient pressure during processing/too much monomer (occurs everywhere)
   Granular porosity/granularity - rough granular surface due to incorrect mixing ratio (too much polymer)
   Crazing - cracks at high stress areas/material junctions due to quenching and different thermal contraction coefficients
   Residual monomer - due to insufficient terminal boil (causes irritation)

Question 13

Setting teeth

1. 5 techniques for setting teeth
2. 1 pro/con of two
3. 3 types of artificial teeth – 2 features of each

Answer 13

1. Cupsed teeth, cuspless/flat cusped teeth, monoplane occlusion, lingualised occlusion, crossbite
2. Cusped teeth - efficient at breaking up food; occlusal interference (unstable)
   Cuspless teeth - no occlusal interference (stable); not as efficient at breaking up food
3. Plastic/acrylic - silent in function, soft, tough, chemical bond with denture base
   Modified acrylic/polymers/composite - high abrasion resistance, not as soft, silent in function, chemical bond with denture base
   Porcelain - noise in function, hard, brittle, mechanical bond with denture base