Fabricating Removable Partial Denture Bases 1 Factors Affecting

Fabricating Removable Partial Denture 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 4 The choice of selecting acrylic or porcelain teeth are determined by the dentist

(b) Types of anterior tooth and tissue replacement 4 (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 Post Used 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 toothcolored 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 Technique 1 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 Technique 5 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 Technique 8 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 Technique 13 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 Technique 14 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

1. Procedures for Arranging Artificial Teeth and Waxing Up Denture Bases a. Tooth arrangement 1. If try-in is going to be accomplished, tinfoil is applied to cast over edentulous area as separator 2. Set the maxillary posterior teeth a. Flow wax around denture base retention to seal frame to cast b. Lower incisal guide pin 0. 5 mm c. Set posterior teeth in maximum intercuspation 1. Marginal ridges set at same height 2. Maintain buccal alignment with adjacent teeth 3. Eccentric contacts must be avoided

1. Procedures for Arranging Artificial Teeth and Waxing Up Denture Bases a. Tooth arrangement 1. If try-in is going to be accomplished, tinfoil is applied to cast over edentulous area as separator 2. Set the maxillary posterior teeth a. Flow wax around denture base retention to seal frame to cast b. Lower incisal guide pin 0. 5 mm c. Set posterior teeth in maximum intercuspation 1. Marginal ridges set at same height 2. Maintain buccal alignment with adjacent teeth 3. Eccentric contacts must be avoided

1. Procedures for Arranging Artificial Teeth and Waxing Up Denture Bases a. Tooth arrangement d. Return incisal guide pin flush with upper member e. Grind occlusal surfaces until pin touches the table to develop tight maximum intercuspation

1. Procedures for Arranging Artificial Teeth and Waxing Up Denture Bases b. Wax-up 1. Snowshoe principle a. Establish full coverage; cover ridge, mucco-buccal and lingual folds entirely b. Pressure is distributed over a broad surface area rather than concentrated on a point 2. Bulk wax - from finish lines to 1 mm past blue design line a. Overwax 2 mm onto the external finish line; allows finishing with no step between metal and acrylic b. Fill peripheral roll

b. Wax-up 3. Gingival trim - duplicate natural tissue a. 45° angle on the buccal side b. 90° angle on the lingual side 4. Festooning - eminences, when contoured should appear natural 5. Check occlusion to ensure no tooth movement has occurred during waxing

(3) Finishing RPD Bases (b) Remount the casts on the articulator (c) Selective Grind Artificial teeth

(3) Finishing RPD Bases (c) Restore vertical dimension of occlusion 1 Ensure incisal pin contacts the incisal guide table 2 Be sure to maintain contacts in tight centric occlusion 3 Adjust Excentric excursions, Protrusive and lateral

(3) Finishing RPD Bases (d) Carefully remove RPDs from casts (don’t break acrylic or bend out clasps) (e) Finish 1 Trim flash using arbor bands or acrylic trimming stone 2 Free acrylic from clasp using sandpaper discs 3 Smooth transition between acrylic and external finish lines using rubber points and wheels 4 Borders should be round with no sharp edges

(3) Finishing RPD Bases 5 Use a fissure bur to grind bubbles from gingival trim (f) Polish 1 Do not pumice festooning away - go back to finishing for hard to get areas 2 Close attention should be given around clasps 3 Repolish metal areas as necessary (g) Disinfect RPDs IAW manufacturer's directions

Denture Base Repairs 4 Denture Tooth Repair – Box Preparation – Matrix to position tooth

Denture Base Repairs 4 Denture Base Fracture – Rabbet Preparation – Position on cast

Denture Base Repairs 4 Denture Base Reline – Reline Jig