J Korean Acad Prosthodont JKAP The Journal of Korean Academy of Prosthodontics 0301-2875 2005-3789 The Korean Academy of Prosthodontics 10.4047/jkap.2012.50.1.10 Original Article A FEM study on stress distribution of tooth-supported and implant-supported overdentures retained by telescopic crowns Paek Jang-Hyun DMD MS Lee Chang-Gyu DMD MSD PhD Kim Tae-Hun DDS Kim Min-Jung DMD Kim Hyeong-Seob DMD MSD PhD Kwon Kung-Rock DMD MSD PhD Woo Yi-Hyung DMD MSD PhD Department of Prosthodontics, School of Dentistry, Kyung-Hee University, Seoul, Korea. Corresponding Author: Yi-Hyung Woo. Department of Prosthodontics, School of Dentistry, Kyung-Hee University, #1, Hoegi-Dong, Dongdaemun-Gu, Seoul, 130-701, Korea. +82 2 958 9340, yhwoo@khu.ac.kr 01 2012 31 01 2012 50 1 10 20 12 10 2011 23 12 2011 30 12 2011 Copyright © 2012 The Korean Academy of Prosthodontics 2012 Purpose

The purpose of this study was to investigate the stress distribution in mandibular implant-supported overdentures and tooth-supported overdentures with telescopic crowns.

 Materials and methods

The assumption of this study was that there were 2, 3, 4 natural teeth and implants which are located in the second premolar and canine regions in various distributed conditions. The mandible, teeth (or implants and abutments), and connectors are modeled, and analyzed with the commercial software, ANSYS Version 10.1. Stress distribution was evaluated under 150 N vertical load bilaterally on 3 experimental conditions - between canine areas, canine and 2nd premolars, 10 mm posterior to 2nd premolars.

 Results

Overall, the case of the implant group showed more stress than the case of the teeth group in stress distribution to bone. In stress distribution to superstructures of tooth and implants, there was no significant difference between TH group and IM group and the highest stress appeared in TH-IV and IM-IV. The stress caused from bar was much higher than those of implant and tooth. TH group showed less stress than IM group in stress distribution to abutment teeth and implant.

 Conclusion

The results shows that it is crucial to make sure that distance between impact loading point and abutment tooth does not get too far apart, and if it does, it is at best to set abutment tooth on premolar tooth region. It will be necessary to conduct more experiments on effects on implants, natural teeth and bone, in order to apply these results to a clinical treatment.

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Finite element model of A: mandible, B: natural tooth (left), implant (right), and abutments, C: outer crown and connector.

Loading conditions A. LC1: Vertical load was applied between canines (150 N). B. LC2: Vertical load was applied between canine and 2nd premolars (150 N). C. LC3: Vertical load was applied on 10 mm posterior area to 2nd premolars (150 N).

Stress distributions of LC1 on peri-implant bone. A: TH-I, B: TH-II, C: TH-III, D: TH-IV, E: TH-V, F: TH-VI.

Stress distributions of LC2 on peri-implant bone. A: TH-I, B: TH-II, C: TH-III, D: TH-IV, E: TH-V, F: TH-VI.

Stress distributions of LC3 on peri-implant bone. A: TH-I, B: TH-II, C: TH-III, D: TH-IV, E: TH-V, F: TH-VI.

Stress distributions of LC1 on peri-implant bone. A: IM-I, B: IM-II, C: IM-III, D: IM-IV, E: IM-V, F: IM-VI.

Stress distributions of LC2 on peri-implant bone. A: IM-I, B: IM-II, C: IM-III, D: IM-IV, E: IM-V, F: IM-VI.

Stress distributions of LC3 on peri-implant bone. A: IM-I, B: IM-II, C: IM-III, D: IM-IV, E: IM-V, F: IM-VI.

Material properties

Classification of teeth and implants by the number and area in mandible

Maximum von Mises stress values in mandible (MPa)

LC: load case, TH: tooth, IM: implant

Maximum von Mises stress values in the prostheses (MPa)

LC: load case, TH: tooth, IM: implant

Maximum von Mises stress values in teeth and implants (MPa)

LC: load case, TH: tooth, IM: implant