Stress Breakers
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Transcript of Stress Breakers
In the distal extension RPD support is derived from both the residual ridge and abutment
teeth. The variation in consistency providing this support allows some rotational
movements of the free-end base towards the soft tissues
Harmful Tissue-ward movements of distal
extension under occlusal load are
transmitted to the abutment teeth
resulting in loosening of these teeth
1.Broad tissue coverage, 2.The use of functional basing.3.Use of narrow teeth and harmonious occ. 4.Placing the artificial teeth on the anterior two-thirds of the base.5.Correct choice of direct retainer.
Strain on the abutment teeth is minimized through:
This principle is fulfilled by stress breaker design
It is a device or design, which allows movement between the denture base and the retainer to reduce lateral and tipping forces on abutment
teeth. It is also called "Stress director" or "Stress equalizer".
The stress breaker
Types of Stress Breakers
RPD having a movable joint between the direct retainer and the denture base
1-
Partial dentures having a flexible connection between the direct retainer and the denture base
2-
b-Wrought wire connectors soldered to the main major connector
c-Clasps having a stress breaking effect
a- Split major connectors
Types of Stress Breakers
RPD having a movable joint between the direct retainer and the denture base This joint may be in the form of
hinges, ball and socket devices or sleeves and cylinders
1-
Hinged type stress breakers allows vertical and hinge movement of the base
Hinged type stress breakers allows vertical and hinge movement of the base to prevent direct transmission of
tipping forces to the abutment
A- Dalbo extra-coronal precision attachment device
B- Chrisman intra-coronal retainer
Split major connectors
Partial dentures having a flexible connection between the direct retainer and the denture base
2-
(a)
A lower partial denture framework with partial division of a lingual plate to
achieve stress breaking action
(b) Wrought wire connectors soldered to the main major connector
c-Clasps having a stress breaking effect
1- R.P.I.
3 -R.P.A.4 -WROUGHT WIRE CLASP
2- Reverse Aker Clasp
Indications for the use of stress breakers:
2- Cases exhibiting well formed residual ridges and weak abutment teeth
3- If internal attachments are used to retain a distal-extension base
1- In distal extension RPDs
Distribution of stress between abutment teeth and the residual ridge.
The alveolar support of abutment teeth is preserved because horizontal forces acting on them are minimized.
Physiologic stimulation of the mucosa helps to minimize bone resorption due to the intermittent pressure caused by movement of the denture base.
If relining of the denture base is needed but not done immediately for any reason, the abutment teeth are not damaged.
Advantages of Stress Breakers
Disadvantages of Stress Breakers
Difficult to construct.If the intermittent pressure are beyond the physiologic tolerance;
ridge resorption results.
Easily distorted and difficult to repair.
Reducing the effectiveness of I.R.Expensive.Less tolerated by patients.Allow food trapping and occasionally tissue-trapping.If relining of the denture base is needed but neglected for a long
time , excessive ridge resorption results.
F (fulcrum): Indirect retention
Stress breaker
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