18. Changes of retentive Force of Radicular Attachments Before and After Wear Simulation-Fpcusing on Overseas Magnetic Attachments

A.Bazar, H. Mizutani, M. Hideshima, M.Sato, A. Nishiyama, T. Ando, K. Nakamura, N. Takano, S. Ishikawa, D. Okusa, Y.Igarashi

Section of Removable Prosthodontics, Graduate School, Tokyo Medical and Dental University

Introduction

Denture retention depends on several factors, in particular, denture retainer, bone support, interfacial surface tension, interfacial viscous tension, adhesion, gravity1, to cite only those.

Tooth retained or implant retained mandibular overdentures have proved to be logical methods to maintain oral function and to delay or eliminate future prosthodontic problems.

As a result, with time overdenture attachments loose their retentive properties. Failure of overdenture attachments adversely affects their function, maintenance and patient satisfaction.

Objective

To evaluate and compare maximum retentive force of overdenture attachments before and after various levels of wear simulation.

Materials and Methods

Six specimens from 8 types of commercially available overdenture attachments were tested (Table1, Figure 1) .

Wear Simulation

Wear simulation was performed for each specimen by a micromaterial testing machine (MMT-250NB-10, Shimadzu Co., Kyoto, Japan) with a sensor interface PCD-320 and maximum retentive force were recorded by software package PCD-30A (Kyowa Electronic Instruments Co.,Tokyo, Japan). Five thousand insertion-removable cycles were performed with 50 mm/min cross head speed in normal saline (Otsuka Pharmaceutical Co.,Ltd, Tokyo, Japan) at 37ºC. Initially, and after each 500 cycles, 3 records of maximum retentive force were recorded and averaged for each specimen (Figure 2) .

Results

Recorded and averaged means are showed in Fig.3 This figure represented the relations between all the samples.

EOB, E3, LRP, E4 decreased slightly and continued keeping the same level while CN increase and after kept the same level. With HS we noticed any variation.

As for DZ we observed a variation level.DB sharply decreased before to keep the same level.

Discussions

During the function denture performs variety of complex and difficult to evaluate movements. Unfortunately measurements during these movements are impossible to accomplish intraorally and results of in vitro experiments should be taken as a guidance.

As film of saliva between corresponding parts of attachment acts as a protective layer and lubricant that reduces wear, during fatigue simulation specimens were immersed in0normal salina of 37 º C.

High congruence exists between in vitro measured retentive properties of overdenture attachments on teeth and implant imitating models, therefore results of this study can be applied to both treatment concepts - tooth and implant-supported overdentures.

Conclusions

Overdenture attachments, except Conod and Hyper Slim tend to loose their retention due to fatigue. Initial retention is significantly different from retention after wear simulation.

Retentive properties of studs are more susceptible to fatigue than that of magnetic attachments.

References

1. V. Rutkunas, H.Mizutani,H Takahashi,H. Influence of attachment wear on retention of mandibular overdenture. Journal Of Oral Rehabilitation 2007 34; 41-51.

2. C.E.Besimo, A. Guarneri. In vitro retention force changes of prefabricated attachments for overdentures. Journal of Oral Rehabilitation 2003 30; 671-678

Discussion Board