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Effects of the type and rigidity of the retainer and the number of abutting teeth on stress distribution of telescopic-retained removable partial dentures

Sahin, Volkan
Akaltan, Funda
Parnas, Levend
Background/purpose:Little is known about the force-transmission characteristicsand patterns of telescopic-retained removable partial dentures (RPDs) as related to their typeand rigidity (rigid and/or resilient) and the number of abutting teeth supporting the tele-scopic dentures. In this study, we compared the strain around the abutting teeth and eden-tulous ridges supporting telescopic-retained RPDs with different designs using a straingauge technique.Materials and methods:A maxillary model including four abutting teeth (# 14, 13, 23, and 24)was constructed and is referred to as Case 1. In total, four RPD frameworks (two resilient andtwo rigid) were fabricated for Case 1 with a conventional telescope retainer and attachment-retained telescopic retainer (ARTR) groups. A vertical static load of 280 N was applied, andstrain values obtained from the strain gauges were recorded. RPDs were modified accordingto the following casesdCase 2 included teeth 14, 13, and 23; Case 3 included teeth 14 and13; and Case 4 included teeth 13 and 23dand measurements were repeated. A randomizedblock analysis of the variance test was conducted using a general linear model procedure withstatistical software. Multiple comparisons between groups were performed using Tukey’shonest significant difference test (aZ0.05).Results:RPDs with an ARTR produced more strain distal to the abutting teeth than RPDs witha conventional telescope retainer. Both retainer types with a rigid design produced morestrain distal to the abutting teeth than did retainers with a resilient design. RPDs supportedby four, three, and two unilateral abutting teeth produced similar strain patterns. RPDs sup-ported by two bilateral abutting teeth produced the highest strain distal to the abuttingteeth, but there was no significant difference between the strains produced by RPDs supported by either two unilateral or bilateral abutting teeth. The highest strain values wereobtained from strain gauges distal to the “terminal” abutting teeth. Directions of the prin-cipalstrainwereinaverticaldirectionforgauges located distal to the terminal abuttingteeth. More strain was produced on the posterior edentulous ridges.Conclusion:RPDs with an ARTR and both retainer typeswitharigiddesignproducedmorestrain distal to the abutting teeth. Using more than two abutting teeth did not improve thestrain patterns of the tested RPDs. More strain was produced on the posterior edentulousridges.Copyrightª2012, Association for Dental Sciencesof the Republic of China. Published byElsevier Taiwan LLC. All rights reserved.