Biomechanical investigations of the expanded platform-switching concept in immediately loaded small diameter implants.

STATEMENT OF PROBLEM: Use of a small diameter implant may increase the stress on bone around the implant neck; however, an expanded platform design may mitigate these stress concentrations. To date, no study has compared the biomechanical effect of regular platform and extended platform designs on an implant. PURPOSE: The purpose of this in vitro study was to evaluate the biomechanical effects of an expanded platform-switching design for immediately loaded small diameter implants on bone strains. MATERIAL AND METHODS: Three groups of artificial jawbone models were prepared for small diameter (3.25-mm) and standard diameter (4.0-mm) implants with expanded or regular platform designs. Platform-switching implant design was implemented by assembling implants with a smaller connected abutment. Specimens were tested under both vertical and lateral static loads at 190 N. Peak values of the principal microstrain of bone were recorded and analyzed statistically with Kruskal-Wallis test and multiple comparisons Bonferroni test (alpha=.05). The initial stability of each implant was also measured for 3 types of implant. RESULTS: Under vertical loading, the bone strain was lowest for the regular type of immediately loaded small diameter implant. Under lateral loading, peak bone strain around the expanded platform small diameter implant with platform switched abutment was up to 74.9% lower than that of the regular type of small diameter implant. Increasing the implant diameter from 3.25 mm to 4.0 mm on the expanded platform implants reduced the bone strain by approximately 10% and 30% under lateral and vertical loading, respectively. The initial implant stability did not vary significantly among the implants tested. CONCLUSIONS: Using the expanded platform small diameter implant with a platform-switched abutment may decrease the marginal bone strains around immediately loaded small-diameter implants under lateral loading.