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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