Photoelastic study of the support structures of distal-extension removable partial dentures.

Abstract

PURPOSE:

The double system of support, in which the distal-extension removable partial denture adapts, causes inadequate stress around abutment teeth, increasing the possibility of unequal bone resorption. Several ways to reduce or more adequately distribute the stress between abutment teeth and residual ridges have been reported; however, there are no definitive answers to the problem. The purpose of this study was to analyze, by means of photoelasticity, the most favorable stress distribution using three retainers: T bar, rest, proximal plate, I bar (RPI), and circumferential with mesialized rest.

MATERIALS AND METHODS:

Three photoelastic models were made simulating a Kennedy Class II inferior arch. Fifteen dentures with long saddles, five of each design, were adjusted to the photoelastic patterns and submitted first to uniformly distributed load, and then to a load localized on the last artificial tooth. The saddles were then shortened and the tests repeated. The quantitative and qualitative analyses of stress intensity were done manually and by photography, respectively. For intragroup analyses the Wilcoxon test for paired samples was used, while for intergroup analyses Friedman and Wilcoxon tests were used to better identify the differences (p < 0.05).

RESULTS:

The RPI retainer, followed by the T bar, demonstrated the best distribution of load between teeth and residual ridge. The circumferential retainer caused greater concentration of stress between dental apexes. Stress distribution was influenced by the type of retainer, the length of the saddle, and the manner of load application.

CONCLUSIONS:

The long saddles and the uniformly distributed loads demonstrated better distribution of stress on support structures.

• Authors: Marcio Magno Costa, Marco Antonio Moreira Rodrigues da Silva, Sonia Aparecida Goulart Oliveira, Vanderlei Luiz Gomes, Polliane Morais Carvalho, Barbara Lima Lucas
• Journal: Journal of prosthodontics : official journal of the American College of Prosthodontists (J Prosthodont) Vol. 18 Issue 7 Pg. 589-95 (Oct 2009) ISSN: 1532-849X [Electronic] United States
• PMID: 19531158 (Publication Type: Comparative Study, Journal Article)

Topics

• Biomechanical Phenomena
• Dental Abutments
• Dental Clasps
• Dental Stress Analysis
• Denture Bases
• Denture Design
• Denture Retention (instrumentation, methods)
• Denture, Partial, Removable
• Elasticity
• Functional Laterality
• Humans
• Mandible
• Models, Dental
• Statistics, Nonparametric
• Stress, Mechanical