pontic breakages Flashcards
What is a major cause of dislodgement due to preparation design?
Inadequate retention and resistance form due to 1)insufficient taper[4-8* each surface],
2)inadequate total occlusal convergence [10-20* Goodacre et al 2001];
3)short axial walls[minimal occlusocervical dimension of 4 mm for molars and 3 mm for other teeth], and 4)poor OC/FL ratio (<0.4).
5) Facioproximal and linguoproximal line angles are missing, and teeth are NOT modified with auxiliary resistance features such as axial grooves or boxes, preferably on proximal surfaces.
What OC/FL ratio is ideal for molars to ensure retention?
A ratio of 0.4 or higher; <0.4 suggests poor mechanical retention
What is the minimum occlusocervical dimension for molars and other teeth?
4 mm for molars, 3 mm for other teeth.
What can be added if resistance form is poor and crown height is insufficient?
Auxiliary resistance features like grooves or boxes (preferably proximal surfaces).
What preventive measure ensures good retention and resistance form?
Ensure proper taper (4–8° per surface) and adequate axial wall height.
How does improper occlusal adjustment cause dislodgement?
High/premature contacts or bruxism(parafxnal habits) concentrate stress causing fractures, loosening the provisional.
How to prevent dislodgement due to occlusion?
Adjust occlusion for even force distribution.
How does poor marginal adaptation lead to loss of retention?
Marginal gaps causes dissolution of temp cement, leading to loosening.
How to prevent poor marginal fit (gaps) in provisionals?
Use accurate impressions and relining techniques; eg putty-wash impression technique.
What causes dislodgement related to lack of support/contact?
Inadequate support from adjacent or opposing teeth or improper contact in multi-unit cases leading to m/m and dislodgement.
How to prevent movement/dislodgement in multi-unit provisionals?
Ensure good support and proximal/occlusal contacts.
How does poor cementation technique contribute to dislodgement?
Improper cement choice/application- (eg excessive cement reducing mechanical interlocking) and poor moisture control-lack cotton roll/dry angles.
What is the preventive strategy for cementation?
Use appropriate cement (e.g., self curing ZOE-based temp cement), isolate properly, follow protocol.
What material issue contributes to breakage?
Using weak materials like brittle auto-polymerizing acrylics PMMA (Polymethyl Methacrylate) in high-stress areas or improper mixing.
How to prevent breakage due to material weakness?
Use bis-acryl composites (e.g., Protemp) with better strength; wear resistance and fracture toughness.and follow handling instructions.
What does inadequate thickness of provisional lead to?
Fracture in thin areas like cusp tips, pontics, and connectors during function.
How to ensure structural integrity of the provisional?
Provide adequate material thickness, especially in high-stress areas.
How do patient habits cause breakage?
Parafunctional habits (bruxism/clenching) and sticky/hard food increase stress and fracture risk.
What patient advice helps prevent breakage?
Educate on avoiding hard/sticky foods; consider a night guard; recommend water flosser instead of floss holders.
What mechanical stress causes failure in long-span bridges?
Flexural fatigue due to excessive bending causes material fatigue and failure.
How to prevent breakage in long-span provisionals?
Reinforce with fibers or use splinting techniques.
What is TempBond? Easier to remove compared to?
Temp-Bond™ is a self-curing zinc-oxide eugenol-based temporary cement - ease of removal vs Reinforced ZnOE or eugenol free ZnO
eugenol free ZnO benefits and used for?
Higher strength.
Used for tooth prep lack retention; long term use; parafunction. Offer a balance between strength and esthetics.
Pontic design considerations?
Cleansable
