Denture base

Dr. Shaima’a Ahmed Radwan

Partial denture component

Artificial teeth

Denture base

(saddle) Clasps

(retainer)

Major connectors

Minor

connector

Supporting

rest

The part of a denture that rests on the foundation tissues and to which teeth are attached

Types of denture base

Bounded partial denture base Free end partial denture bases (distal-extension base)

Functions 1.Carries the artificial teeth. 2.Transfers occlusal stress to the supporting oral structures

Vertical forces acting in gingival direction tending to move the denture towards the tissues

3.(support)Tissue-ward movements

3.(support)Tissue-ward movements

Vertical forces acting in gingival direction tending to move the denture towards the tissues

4.Retention

5.Bracing

Resistance to Lateral Movement of the Partial Denture

6.Stability • It is the resistance to tipping forces

7.Prevent migration and over eruption of remaining teeth

• Accuracy of Adaptation To Tissues With Low Volume Change

• Sufficient strength Resistance to fracture/distortion

Low specific gravity – Lightness in mouth Biologically Compatible with tissues

• Good Thermal conductivity. • Esthetics .

Materials

Metallic Bases

• Small edentulous spaces (no room for grid work)

Beaded Metal Base

Prosthetic teeth are attached to the metal base with a plastic base (acrylic resin) or by

retentive posts on the metal surface.

Retentive Posts

Indications:

Metal bases can be used wherever acrylic resin

bases are used.

1. A tooth supported edentulous space where

further bone resorption is not anticipated.

2. When a facing, metal pontic, or metal

reinforced denture tooth is to be used.

Contraindications:

1- Tooth-tissue supported edentulous space.

2- Tooth supported edentulous space where bone

resorption is expected (in areas where teeth have

been removed within 12 months, resorption will

still be occurring at an increased rate and relining

will be usually be required).

Advantages:

1. Very rigid.

2. Very stable form – Maintain their accuracy.

3. High abrasion resistance.

4. High thermal conductivity - improved thermal

perception may lessen the feeling of the denture

as a foreign object.

5. Less porous than resin and therefore easier to clean (more hygienic). Also this character lessens food, plaque and calculus accumulation, thereby maintaining healthy tissues.

6. Minimal weight and bulk - The metal bases can be cast thinner than resin bases while maintaining adequate strength.

1. Metal not esthetic - the esthetic result can be compromised unless the metal can be veneered with sufficient thickness of acrylic. If an insufficient veneer is used, a greyish hue of the underlying metal becomes visible.

2. Difficult to make adjustment and corrections or teeth addition

3. Difficult to Reline or repair

Non-metallic denture base

2. Acrylic Resin Bases

• Acrylic resin bases are the most common types

used in removable partial dentures.

• The acrylic resin denture bases have the plastic

material in contact with the edentulous ridge.

• They should be routinely used in distal

extension cases to allow for relining of the base

to maintain mucosal support.

Indications:

1. Tooth-tissue supported edentulous spaces.

2. Tooth supported edentulous spaces where bone

resorption will necessitate a reline/rebase.

3. Where considerable missing alveolar tissue

must be replaced.

4. Where esthetics is a primary concern.

Advantages:

1. Can be easily relined.

2. Esthetically superior to metal bases

3. Easy to fabricate, adjust, finish and polish, and

repair.

Disadvantages:

1. Dimensional stability less than metal bases –

risk of warpage

2. Lower strength than metal • Requires more bulk for rigidity than metal

• Easily abraded.

• Easily fractured.

3. More porous than metal and therefore more

difficult to clean.

4. Low thermal conductivity.

III. Combined

Free end saddle cases I,II

Long class III,IV

• Diabetic patients , steroid therapy

• Extreme bone loss

Methods of Attaching denture base

Closed meshwork

Open lattice ladder

Tissue stops

They are formed by making holes in the relief wax during preparation of the master cast

before duplication. They are essential part in the fitting surface of minor connectors. They

are 2 or 3 in number that contact the cast.

1- Stabilize the framework on the master cast during processing as the acrylic resin is

packed in the retention spaces.

2- Elevate the minor connectors forming the base from the ridge by providing space equal

to the thickness of the acrylic bases.

Tissue stops

Finish Lines

The purpose of finish lines is to create a distinct resin-metal interface and

to prevent the acrylic resin from becoming too thin.

Finish Lines

- Finish lines are : Internal and External finish

lines.

-The Internal finish line formed by carving the

relief wax on the master cast before duplication to

create space for packing acrylic resin under mesh

minor connector.

-The external finish line formed during formation of wax pattern by carving a sharp definite angle at the junction between the major connector and the minor connectors forming the denture base (the angle should be less than 90 degree).

It should be located approximately

2 mm lingual to the lingual surface of the

replacement denture teeth.

During designing denture base important

notes should be take into consideration:

- Support is an important consideration in designing saddles

for extension base saddle.

- Maximum coverage to the residual ridge, buccal shelf, palate, and pear shaped pad.

- Maximum coverage without encroaching on movable tissue

to reduce stress on the abutment teeth.

- When denture cross gingival tissue it should be relieved to

avoid the impinge on gingival tissue which cause irritation

& periodontal damage.

-Wide distribution of the load on the teeth and the

mucosa.

- Need for future relining.

Acrylic Resin Finish Lines

a

major connectoredentulous ridge

slight undercut

staggered finish lines

gridwork

Acrylic denturebase

• Internal & external finish lines should not coincide