Tightening of healing abutments: influence of torque on bacterial proliferation risk, an in vitro investigation.

BACKGROUND: Gap at the implant-healing abutment junction can increase the risk of bacterial proliferation. In this study, we determined the leakage at the microgap, and we evaluated hand screwing among clinicians. MATERIALS AND METHODS: The torques tested with nitrogen gas flow were 10, 15, 20, and 30 N cm, and 54 clinicians were asked to torque down a healing abutment as for a surgical procedure. RESULTS: There were no significant differences between 10 and 15 N cm, with a total lack of tightness. For 20 and 30 N cm, there was a notable decrease in leakage. The torque achieved by hand was <10 N cm for 61.7% of the clinicians, between 10 and 15 N cm for 29.1%, between 15 and 20 N cm for 8.0%, and between 20 and 25 N cm for 1.2%. CONCLUSION: There was a significant difference related to the strength of tightening. Under the conditions of our experiment, the gap of connection was reduced with a torque of >/=20 N cm. Only a small portion of the clinicians could obtain these values by hand. Therefore, a dynamometrical manual wrench should be used to minimize the gap during the osseointegration period.