Fabricating Removable PartialDenture Bases

(1) Factors Affecting Selection of Artificial Teeth

(2) Altered Cast Technique

(3) Procedures for Articulating and Restoring VDO

(4) Procedures for Arranging Artificial Teeth and Waxing Up Denture Bases

(1) Factors Affecting Selection of Artificial Teeth

(a) Criteria for common denture base and artificial tooth combinations

1 Maxillomandibular space

2 Esthetic values

3 Absence of soft tissue undercuts

4 Length of edentulous space

5 Health of soft tissue and anticipated rate of bone resorption

(1) Factors Affecting Selection of Artificial Teeth

The choice of selecting acrylic or porcelain

teeth are determined by the dentist

(b) Types of anterior tooth and tissue replacement

(Primary factor is esthetic acceptability)

1 Commercial facings

a Prefabricated facings retained on a metal backing with a cementing medium

b Identical replacement possible

c May be used when undesirable soft tissue undercuts are present

d No reline potential

(b) Types of anterior tooth and tissue replacement

2 Reinforced Acrylic Pontics

a Denture teeth ground to fit an edentulous space and retained on a metal base

b Variety of shades and molds

c An advantage over commercial facings are the improved three dimensional effects, such as overlapping teeth

d May be used when undesirable soft tissue undercuts are present

Braided PostUsed with stock denture teeth similar to RAP.

Denture teeth not needed for wax-up

(b) Types of anterior tooth and tissue replacement

3 Processed tooth-colored resin

a Waxed to metal framework and processed with tooth-colored resin

b May be used when undesirable soft tissue undercuts are present

c Requires stable ridge

(b) Types of anterior tooth and tissue replacement

4 Acrylic denture teeth with resin base

a Attached to metal retention grid or mesh

b Compensates for gross ridge resorption

c Resin base provides support and bracing

d Resin can be relined

e Requires significant vertical space

f Not recommended when deep labial soft tissue undercuts are present

(c) Types of posterior tooth and tissue replacement

1 Acrylic denture teeth with denture resin

a Attached to metal retention grid or mesh

b Denture base can be relined

c Easy to modify

d Moderately esthetic

(c) Types of posterior tooth and tissue replacement

2 Metal teeth integrated into framework

a Better tissue adaptation than processed acrylic

b Requires least amount of space

c Least esthetic

3 Tube tooth attached to metal denture base

a Limited to short span, well healed areas

b Requires 4 mm posts for adequate retention

(c) Types of posterior tooth and tissue replacement

4 Processed tooth-colored resins with spiral post retention

a Short span application

b Substitute for tube teeth

c Requires slightly less interarch space than a tube tooth

(2) Altered Cast Technique

(a) Definition - A corrected impression of the distal extension area(s) of the patient’s mouth, made after the fit of the framework is confirmed in the mouth and before artificial teeth are arranged

(b) Purpose - This procedure is designed to ensure the best possible soft tissue support for a distal extension denture base

(c) Procedures for the Altered Cast Technique1 Dentist adjusts and fits the framework in the patient’s

mouth

2 Dentist designs outline of proposed impression tray

3 Plastic tray will be constructed over the framework’s distal denture base retention

4 Adapt a 26 gauge sheet wax spacer to the edentulous area, then adapt a second layer of 26 gauge sheet wax to the retromolar pad and blend it with the first sheet wax layer, trim wax to design line

(c) Procedures for the Altered Cast Technique5 Warm the distal extension grid of the framework over

a flame and place the framework on the master cast

a Be sure the rests are fully seated

b Remove any wax that flowed over the metal

c apply separator to cast

6 Mix self curing resin to a dough-like consistency

7 Adapt resin over the edentulous area to form a tray that is firmly attached to the retention grid

(c) Procedures for the Altered Cast Technique8 After resin is cured, lift the framework with attached

tray from the cast

9 Trim the tray to the outline the spacer forms

10 Remove wax spacer

11 Disinfect IAW manufacturer’s directions

12 Return framework to the dentist

(c) Procedures for the Altered Cast Technique13 Making the corrected impression

a The dentist makes the corrected impression

b Impression material is placed in the tray(s), then the entire framework is seated in the patient’s mouth

c Disinfect the completed impression

(c) Procedures for the Altered Cast Technique14 Altering the Master Cast

a Draw design for saw cuts across the distal extension, from buccal to lingual, on a line that passes 1 mm behind the distal abutment

b Draw another saw cut line that is parallel and lingual to the lingual sulcus to join with the first cut

c Cut along design lines

d Using a fissure bur or a saw, place multiple dovetail cuts in the cut surface of the cast to create mechanical retention for the corrected addition

(c) Procedures for the Altered Cast Technique

e Place the framework with corrected impression on the prepared master cast

1 Be certain all rests are in complete contact with their respective seats

2 Secure the framework in place with sticky wax

(c) Procedures for the Altered Cast Technique

f Bead and box around the borders of the impression

1 Place utility wax around the outer border of the impression 3 mm below the peripheral roll and seal it to both the impression and the base of the cast at the ends of the wax

2 Seal boxing wax in place even with the height of the base of the cast and along the outer border of the utility wax

g Soak the base of the cast for about 5 minutes

(c) Procedures for the Altered Cast Technique

h Vacuum mix stone and pour impression

1 Use manufacturer’s directions for water/powder ratio

2 Remove wax after stone sets

i Separate Cast

1 Remove framework and tray from the cast

2 Completely clean debris from the cast

3 Check the cast for voids

4 Trim cast, preserving the land area

(c) Procedures for the Altered Cast Technique

j Remove acrylic resin tray

1 Flame tray until it softens

2 Peel tray from the framework

3 Clean framework thoroughly

k Seat the framework back on the cast with all rests seated