Title: 0395 - Partially Edentulous Casts Vertical Stabilization – Hunt for the Adequate Tripod


Michael Etinger (Presenter)
Hebrew University

Nurit Beyth, Hebrew University
Yael Houri-Haddad, Hebrew University
Gilad Ben Gal, Hebrew University
Yoav Pietrokovski, Hebrew University


Objectives: Accurate transfer of interocclusal relations for cast mounting is essential for the prosthodontic treatment success. Various occlusal registration methods are advocated aiming to achieve horizontal stability between the casts, while maintaining interocclusal accuracy. Partial occlusal rims are recommended when interocclusal tripod contacts are lacking. The present study seeks to establish when partial occlusal rims are the recommended interocclusal-registration-technique in relation to the number and location of the missing teeth.

Methods: Standard typodent upper and lower jaw models were occlusaly adjusted using composite add-ons, and selective grinding until ideal occlusion was achieved. Full arch and serial extraction of typodent teeth were performed to simulate edentulous jaws. Impressions and casts of the edentulous jaws were made following a standardized repetitive protocol. Stability of the casts was evaluated using an intraoral scanner. Bite registration of each edentulous cast was compared to full arch interocclusal record that served as control. Vertical stability was recorded as: Stable (full contact), unstable (reduced contact), Non-articulating. Parabolic line was drawn between the occlusal contacts and the area enclosed by the parabola and a line segment was computed using ImageJ software. Correlation between model stability and the geometric measurements of the area of the occlusal-parabola was indexed.

Results: In all cases of Kennedy Class 1&2 defects articulation was lost when occlusal parabola area was <50% In Kennedy Class 4 defect when occlusal-parabola area was <45% vertical stability was lost.

Conclusions: The occlusal-parabola area correlates with occlusal stability of the casts in passive articulation. Occlusal cast stability without using partially occlusal rims in Kennedy Class 1 and 2 can be achieved when two premolars on both sides or one premolar and at least one molar are present.In Kennedy Class 4 defects, adequate stability will be achieved with at least two premolars on one side and one premolar on the other.

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: NONE