Sterilization and Disinfection of Magnetic Attachments

E. Muraishi, Y. Suminaga, F. Tsuchida, N. Takishin and T. Hosoi

Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine

Introduction

Sterilization and disinfection are important in dental treatment. Although magnetic attachments have been used in clinical dentistry for about ten years, sterilization and disinfection have not been frequently studied, and there are no established sterilization and disinfection methods for magnetic attachments. As heating can weaken magnetic assemblies and keepers, and chemicals can corrode metals; sterilization and disinfection may alter the surface properties of magnetic surfaces or lower attractive force. There is a need to develop sterilization and disinfection methods that are suitable for magnetic attachments.

Purpose

The purpose of this study is to optimize and standardize sterilization and disinfection methods for magnetic attachments by measuring the surface roughness and attractive force of magnetic assemblies and keepers after subjecting them to conventional dental sterilization and disinfection. Materials and Methods

Table 1 summarizes the sterilization and disinfection methods used in this study. The magnetic attachment PHYSIO MAGNET 35 (Nissin Co. Ltd., Kyoto, Japan) was used. The diameter and thickness of magnetic assemblies were 3.5 and 1.3 mm, respectively, while those of keepers were 3.5 and 0.8 mm, respectively. Attractive force indicated by the manufacturer was 5.5 N.

Five magnetic assemblies and five keepers were subjected to each sterilization and disinfection method. As a control, five magnetic assemblies and five keepers that were not sterilized or disinfected were used in comparison.

After sterilization or disinfection, the surface roughness (Ra) of magnetic assemblies and keepers was measured using non-contact 3-dimensional measurement equipment (NH-4H, Mitaka Kohki Co., Ltd., Japan) (Fig.1). Then, attractive force was measured using a digital force gauge (FGC-1, NIDEC-SHIMPO Co., Kyoto, Japan) (Fig.2). Statistical analysis was performed using one-way layout analysis of variance and Scheffe's test (SPSS ver.12, SPSS Japan Inc., Tokyo, Japan) at significance level of α= 0.05.

Results

Figure 3 shows the surface roughness of magnetic assemblies. When compared to the control, the surface roughness of sterilized or disinfected magnetic assemblies was greater, and surface roughness was similar in all four methods. There was a significant difference between the control and the four sterilization and disinfection methods. There was no significant difference in the surface roughness of magnetic assemblies among the four sterilization and disinfection methods.

Figure 4 shows the surface roughness of keepers. As was the case with magnetic assemblies, there was a significant difference between the control and the four sterilization and disinfection methods. Moreover, EOG sterilization was the smallest value in four methods in the surface roughness of keeper. The surface roughness of keepers was the largest using 0.5% NaOCl, and there was a significant difference with EOG sterilization.

Figure 5 shows attractive force. When compared to the control, there was no marked difference in attractive force using STERIHYDE, and attractive force tended to be lower for the other methods. There was a significant difference between control and autoclave, between control and EOG sterilization and between autoclave and STERIHYDE. While the sterilization slightly lowered attractive force, the degree of decrease was within a clinically acceptable range.

Conclusions

1. Sterilization and disinfection increased surface roughness and lowered attractive force.

2. The degree of change in surface roughness was low for EOG sterilization and STERIHYDE, but large for NaOCl.

3. Autoclave and EOG sterilization slightly lowered attractive force, but the degree of decrease was within a clinically acceptable range.

4. For sterilization and disinfection of magnetic attachments, EOG sterilization and STERIHYDE are suitable, but not NaOCl.

References

1. Nakamura K., Kotake M., Mizutani H. et al; Influences of the Heat Treatment for Magnet Assemblies with or without Keepers on Attractive Force of Magnetic Attachments, J J Mag. Dent 12(1):27-32,2003.(in Japanese)

2. Nakamura Y., Tanaka Y., Ishida T. et al; Experimental Research of Some Clinical Treatments on theAttractive Force of a Magnetic Attachment;MAGFIT. Aichi-Gakuin Dent Sci 36(4):731-735, 1998.(in Japanese)

3. Nakamura K., Mizutani H., Fukazawa N. et al; Influences of Heat Treatments on Attractive Force of Magnetic Attachments, J J Mag. Dent 6(1):63-70,1997. (in Japanese)

Discussion Board