fp ante law Flashcards
What does Ante’s Law state in prosthodontics?
The root surface area of abutment teeth must be equal to or greater than that of the missing teeth being replaced.
What is the clinical relevance of Ante’s Law?
It ensures abutment teeth can handle the load of pontics without failure of the prosthesis.
What should you do when the crown-to-root ratio is unfavorable for abutments?
Use double abutments, where the secondary abutment has equal or greater root surface area than the primary.
When are double abutments required?
When the primary abutment’s crown-root ratio is unfavorable or root surface area is insufficient.
Why is root surface area important in FDP planning?
It helps determine whether abutments can support the functional load of pontics.
What happens if pontics lie outside the inter-abutment axis?
It creates torquing forces on abutments, increasing the risk of tipping and failure.
Why is adding first premolars useful in a long-span anterior bridge?
It increases retention and resistance, reduces torquing forces on canines.
How does arch curvature affect stress on abutments?
More curvature = longer lever arm = more stress and torque on abutments.
What is the biomechanical risk of pontics placed too far forward in a curved arch?
Tipping or torquing of abutment teeth due to increased lever arm effect.
What is a major cause of dislodgement due to preparation design?
Inadequate retention and resistance form dt
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(gap) 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 provisional breakage due to material weakness? use… (eg …) with better… , …. resistances, and … toughness; follow… instructions.
Use bis-acryl composites (e.g., Protemp) with better strength; wear resistance and fracture toughness. Follow handling instructions.
