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Removable Partial Dentures – Principles of design

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Text of Removable Partial Dentures – Principles of design

4th April Selby Dental Care Ralf Guscott

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1. 2. 3.

Tissue ward Tissue away Horizontal Lateral Anterio

posterior

4.

Rotational

1. Support 2. Retention 3. Stability 4. Indirect

Retention

Support is the resistance of movement towards the foundation tissues and the transferral of occlusal stresses to the underlying supporting oral structures

Crowns

of teeth or coronal restorations Root faces of teeth Mucosa Implants

Rests on teeth or coronal restorations Rigid major connectors Accurately fitting and correctly extended denture base saddles

Resistance to movement of a denture away from its tissue foundation

Clasps Precision retainers Guiding proximal plates acting on surfaces/planes physical forces at fitting surfaces of denture bases Physiological forces on the polished surface of the denture

The resistance to lateral movement

Lateral

movements have a destructive effect on teeth leading to tilting, breakdown of the periodontal ligament and looseness of abutment teeth.

Bracing

arms placed at or above survey lines Minor connectors Proximal plates Adequate extension of flanges

Components that are used to reduce the tendency a denture to rotate in an occlusal direction about the fulcrum axis

Indirect retention is essential for dentures with one or more free end saddles or a single bound anterior saddle

Chrome Cobalt Acrylic Resin

Which material is better?

Acrylic Resin is often thought to be second best but this is not necessarily the case. considering that the material selection is part of the most appropriate design is probably more important.

The advantages of acrylic resin based RPDs primarily relates to ease of construction, lower production cost and their relative ease of adjustment/ alteration. They are light in weight but usually cover more tissue than a Chrome because of their inferior strength; they are therefore thicker. Acrylis tend to take up stain more easily. However, in many cases it is possible to design a hygienic acrylic resin UPPER denture with a design similar to (but covering more tissue than) a metal denture of a plate design.

Take the acrylic resin above the survey lines to gain tooth support. Practise is risky and fractures often occur with time

1.

Patients wishes /expectations/DH

2.

Study Models Assess the occlusion Is there enough space for rests/ minor and major connectors? Any other obvious complications?

3. 4. 5.

Identify teeth to be replaced Outline the saddles Is Flange required? Decide on the nature of support for the denture

6.

7.

8.

Provision for further teeth to be added? Decide how best to unite the saddles Decide how best to maximise retention

9.

Consider anti rotation (indirect retention)

Case 1

Case 2

Case 3

Case 4

Case 5

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