REMOVABLE PARTIAL DENTURES – PRINCIPLES

OF DESIGN4th April

Selby Dental Care Ralf Guscott

Who should design a partial denture?

Clinician?Technician?

The four movements

1. Tissue – ward 2. Tissue – away3. Horizontal

LateralAnterio – posterior

4. Rotational

Basic Requirements

1.Support 2.Retention3.Stability4.Indirect Retention

Support Support is the resistance of movement

towards the foundation tissues and the transferral of occlusal stresses to the underlying supporting oral structures

Supporting oral Structures

Crowns of teeth or coronal restorations

Root faces of teeth Mucosa Implants

Supporting Elements

Rests on teeth or coronal restorations

Rigid major connectors Accurately fitting and

correctly extended denture base saddles

Retention Resistance to movement of a

denture away from its tissue foundation

Retaining Elements - direct retainers

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

Stability The resistance to lateral movement

Stability Lateral movements

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

Stabilising Elememts

Bracing arms placed at or above survey lines

Minor connectors Proximal plates Adequate extension of

flanges

Indirect Retention Components that are used to reduce the

tendency a denture to rotate in an occlusal direction about the fulcrum axis

Indirect Retention

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

Materials Chrome Cobalt Acrylic Resin

Which material is better?

Materials

Acrylic Resin is often thought tobe ‘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.

MaterialsThe 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.

Materials Take the acrylic resin above the survey

lines to gain tooth support. Practise is risky and fractures often occur

with time

Design

1. Patient’s wishes /expectations/DH

Design

2. Study Models Assess the occlusion Is there enough space for

rests/ minor and major connectors?

Any other obvious complications?

Design

3. Identify teeth to be replaced4. Outline the saddles Is Flange required?5. Decide on the nature of

support for the denture

6. Provision for further teeth to be added?

7. Decide how best to unite the saddles

8. Decide how best to maximise retention

Design

9. Consider anti rotation (indirect retention)

Design

Case 1

Case 2

Case 3

Case 4

Case 5