66) Basic principles of bridge restoration construction. Mechanical resistance. Periodontal base.

whats in it

• RPCA (ALWAYS TO DO WITH BRIDGE RESTORATION) retainer, pontic, connector, abutment tooth

• brdge restorations - used wheb?

• bending/deflection

• how to minimise this

• mechanical resistnace

• periodontal base

RPCA

retained - seats on retainer tooth

Pontic: suspended member of the FPD that replaces missing tooth.

Connector: provides connection between the retainer and the Pontic.

Abutment tooth: tooth that provides support for retainer.

Basic Principles of Bridge Restoration Construction

• when is it used

• mechanical resistance

• periodontal base

• occlusal consideration

• bridge configuration

Basic Principles of Bridge Restoration Construction

When Is a Bridge Indicated?

• Indicated when tooth loss is clearly visible or functionally significant.

• Especially necessary when edentulous spaces are present in both anterior and posterior regions.

• Replacing missing teeth early prevents:

  • Drifting of adjacent teeth into the space

  • Supra-eruption of opposing teeth

  • Occlusal imbalance and disruption of the dental arch

Mechanical Resistance

• Bridge must withstand functional loads such as chewing and grinding.

• Key factors affecting mechanical resistance: (using simple FPDs as an example)

• • • Rigid connectors that distribute occlusal forces evenly

    • Well-prepared abutments with proper taper and height

    • High-strength materials (e.g., metal-ceramic or all-ceramic)

  • Minimal movement or flexion occurs due to the stability of the design and short span.

  • Accurate tooth preparation and good parallelism

• Poor mechanical resistance increases risk of prosthesis failure.

Periodontal Base

• Success depends on the support from abutment teeth and their periodontal structures.

• Abutment teeth should have:

  • Healthy periodontal ligament and bone support

  • Adequate root surface area (Ante’s law)

• Periodontal disease or mobility reduces success rate of the bridge.

Occlusal Considerations

• Opposing teeth may super-erupt into the edentulous space.

• In such cases, simply placing a pontic is insufficient.

• May require restoration or reduction of the opposing tooth.

• In severe cases, devitalization may be needed to correct occlusal height.

Bridge Configuration

• Standard design includes one abutment tooth on each side of the edentulous space.

• Best outcomes occur when:

  • Abutments are periodontally sound

  • Span is short

  • Retainers are well designed

• This configuration can provide long-term, reliable function.

Bending or deflection may also occur in bridge restorations

"Bending increases directly with the cube of the span length and decreases inversely with the cube of the occluso-gingival thickness of the pontic."

so If you double the length of the pontic span, the bending force increases 8 times (because 2³ = 8).
So, longer spans bend more easily and are at higher risk of fracture or debonding.

to prevent flexing:

• Pontic designs with greater occluso-gingival dimension.

• Prosthesis may also be fabricated of an alloy with higher yield

  strength, such as nickel-chromium.