11. Mouth Preparation and Master Impressions

Question 1

Components of restorative treatment plan (4)

Answer 1

Immediate treatment
Hygienic (preparatory) phase
Corrective (reconstructive) phase
Maintenance

Question 2

Clinical stages of partial denture contraction (9)

Answer 2

Primary impressions
Primary jaw registration
Mounted, surveyed study casts
Design denture
Tooth preparation and master impressions
Jaw registration
Trial
Delivery
Review

Question 3

Components of mouth preparation (6)

Answer 3

Initial prosthetic treatment
Surgery
Periodontal treatment
Orthodontic treatment
Conservation treatment and endodontics
Tooth preparation

Question 4

Components of initial prosthetic treatment (4)

Answer 4

Repairs and additions
Temporary relines
Occlusal adjustments
Treatment of denture stomatitis

Question 5

Components of pre-prostehtic surgery (4)

Answer 5

Removal of retained roots/non-erupted teeth
Removal of pathologies
Improving contours of edentulous areas – reduction of bony prominences and hyperplastic soft tissue
Elimination of prominent frenal attachments

Question 6

Components of periodontal treatment (5)

Answer 6

Establishes health in periodontal tissues
Assesses patient motivation
Details instructions in oral hygiene procedures
Scaling and root surface debridement
Periodontal surgery

Question 7

Components of orthodontic treatment (3)

Answer 7

Optimises space
Optimises abutment alignment
Cleft patients, hypodontia patients, periodontal patients

Question 8

Components of conservation treatment and endodontics (4)

Answer 8

Inclused fixed prosthodontics treatment
Should follow denture design and precede denture construction
Establishes clinical integrity of teeth before master impressions are recorded
Facilitates provision of crowns (and/or teeth) with guide planes, rest seats, etc.

Question 9

Tooth preparation helps to (4)

Answer 9

Provide rest seats
Establish guide surfaces
Modify unfavourable survey lines
Create retentive areas

Question 10

Rest seat preparation involves (3)

Answer 10

Producing favourable tooth surface for support
Prevents interference with occlusion
Reduces prominence of rest

Question 11

Guidelines for rest seats on anterior mandibular teeth (2)

Answer 11

Lingual surface is too vertical, and the cingulum is too poorly developed to avoid penetrating the enamel
Incisal rest seats are used

Question 12

Alternative guidelines for rest seats on anterior mandibular teeth (2)

Answer 12

Produce a rest seat in composite applied to the cingulum area
Bond a cast metal cingulum to the tooth

Question 13

Guidelines for rest seats on posterior teeth (4)

Answer 13

Reduce marginal ridge
Rests should be saucer-shaped to allow some horizontal movement and dissipation of occlusal forces
Rest seats should be deep enough to allow a rest of at least 1mm thick
If there is no space occlusally for a clasp to extend buccally from an occlusal rest, the preparation must be extended as a channel onto the buccal surface

Question 14

Definition of guide planes (2)

Answer 14

Two or more parallel axial surfaces on abutment teeth, which limit the path of insertion of a denture
They may occur naturally, but more often need to be prepared

Question 15

What do guide planes provide (4)

Answer 15

Increased stability
Reciprocation
Prevention of clasp deformation
Improved appearance

Question 16

Features of guide plane preparation (3)

Answer 16

Must be prepared parallel to each other and the path of insertion
Should extend vertically 3mm but be kept as far from the gingival margin as possible
Not more than 0.5mm of enamel should be removed

Question 17

Material used for individual special/custom trays for master impressions (2)

Answer 17

Heat-cured acrylic (thinner and usually preferred by dentate patients)
Light-cured acrylic