Stress Distribution after Installation of Fixed Frameworks with Marginal Gaps over Angled and Parallel Implants: A Photoelastic Analysis

• Published in: Journal of prosthodontics Vol. 16; no. 2; pp. 117 - 122
• Main Authors: Markarian, Roberto Adrian, Ueda, Cristiane, Sendyk, Claudio Luiz, Laganá, Dalva Cruz, Souza, Roberto Martins
• Format: Journal Article
• Language: English
• Published: Malden, USA Blackwell Publishing Inc 01-03-2007
• Subjects: Compressive Strength; dental implant; Dental Implants; Dental Prosthesis, Implant-Supported - methods; Dental Stress Analysis; Dentistry; Elasticity; fixed prosthesis; framework; implant-supported prosthesis; photoelasticity
• ISSN: 1059-941X; 1532-849X
• DOI: 10.1111/j.1532-849X.2007.00161.x

Purpose: The objective of this work was to compare by photoelastic analysis the stress distribution along a fixed framework placed over angled or parallel implants with different gap values between the framework and one of the implants.
Materials and Methods: Two photoelastic models were created: (i) with parallel implants; (ii) with a 30° angled central implant. In both cases, three implants were used, and CP titanium frameworks were constructed with commercial components. A plane polariscope was used to observe the photoelastic fringes generated after initial framework assembly, and also when an axial load of 100 N was applied over the central implant. For both models, stress analysis was conducted on well‐fitting frameworks and on another with a 150 μm vertical gap between the framework and the central implant.
Results: The photoelastic analysis indicated that in the model with parallel implants, stress distribution followed the implant axis, and in the model with an angled implant, a higher and nonhomogeneous stress concentration was observed around the apical region of the lateral implants. The placement of an ill‐fitting framework resulted in increased preload stress patterns.
Conclusion: Stresses were generated after screw tightening of the frameworks, increasing when a load was applied and when a vertical gap was present. Angled implants resulted in oblique stress patterns, which were not transferred with homogeneity to the polymeric model.