Clinician-generated torque on abutment screws using different hand screwdrivers

Abstract

Statement of problem: Many clinicians use hand screwdrivers to tighten prosthetic and abutment screws. The impact of the screwdriver type, the location of the implant, and the sex of the practitioner on the generated torque is not well understood.

Purpose: The purpose of this in vitro study was to compare the torque generated by different hand screwdrivers when used in the anterior and posterior regions and to evaluate the correlation between the applied torque and the sex and body mass index (BMI) of the practitioner.

Material and methods: A mandibular typodont with anterior and posterior implants was mounted in a mannequin head. Fifty clinicians (6 prosthodontists, 8 graduate prosthodontic students, and 36 dental students) used their maximum force to tighten the abutment screws in the anterior and posterior regions, using 3 different hand screwdrivers, with handles of different shapes and sizes (small, medium, and large). The torque values generated were measured using torque meters connected to the implants. The generated torque, sex, age, height, and weight were also recorded for each clinician. A generalized linear model was used to find correlations between the different factors and the generated torque (α=.05).

Results: Significant differences were observed among the applied torque values when different screwdrivers were used (P<.001). Higher torque values were generated in the anterior region than in the posterior region (P<.001). The interaction of the sex and BMI of the participants significantly affected the generated torque values (P=.044).

Conclusions: The type of screwdriver and location of the implant affected the generated torque. Torque values generated by the large screwdriver were higher than those of small and medium screwdrivers. Higher torque was applied in the anterior region.