Influence of sterilization on the retention properties of magnetic attachments for dental implants

When used with dental implants advantages of the magnetic attachments include control of load transmitted to implants, improvements in stability, support and retention for the prosthesis, and the relative ease of prostheses fabrication. Clinically, the use of sterilized components is required, and this may be problematic as magnetic alloys are sensitive to temperature. The purpose of this study was to evaluate the influence of autoclave sterilization on the maximum retentive forces and characteristic curves for magnetic attachments recommended for use with dental implants.

Eleven SmCo and NeFeB implant magnetic attachments were evaluated as provided by the respective manufacturers. Implant magnetic abutment and the corresponding denture magnet (n=5 magnet pairs) were tested before and after standardized autoclave sterilization (10 min at 134 degrees C). Each magnet pair was tested 10 times in a calibrated universal testing machine using a non-magnetic test device (s=40 mm, v=20 mm/min). Results were recorded electronically and statistically analyzed using t-test and ANOVA (Welch and Brown-Forsythe test; P<0.05).

After autoclave sterilization all magnetic pairs produced lower (though statistically insignificant) overall retention forces compared with the untreated pairs. After sterilization mean maximum retentive forces (SD) ranged from 5.65 (0.33) to 1.41 (0.07) N. The characteristic force-displacement curves of the tested magnetic systems showed differences among the single products.

Autoclave sterilization caused a non-significant reduction in retentive force of 0.04-14.6% when compared with the unsterilized magnet pairs. There were differences between the tested magnetic pairs for both the initial breakaway forces and the characteristic force-displacement curves. Within the limitations of this study all tested magnetic attachments were sterilized in an autoclave without significant change of retention properties. Nevertheless magnetic implant abutments should be sterilized with caution to reduce the risk of alterations of the retention properties.