Patients of legal age treated for implant explantation of nonmobile dental implants between March 2010 and December 2018 were included in this retrospective study.
The treatment was performed using an implant removal kit (BTI Biotechnology Institute, Vitoria, Spain) that allowed the application of a counter-torque to the bone-implant interface . The decision to raise a flap or not was made according to the surgical needs. Following the manufacturer instructions, a ratchet was engaged into the implant connection and then a counter-torque was exerted by a wrench in counter-clockwise direction. If the counter-torque exceeded the 200 Ncm limit (the torque wrench opened), trephine bur was used to cut into the first 3–4 mm of implant-bone contact. The implant explantation was then continued with the torque wrench. Treatment was considered a failure if the implant could not be removed by this procedure. All the complications occurring during the procedure were also recorded.
The cause of implant removal was grouped into biological (excessive bone loss), mechanical (improper implant positioning, prosthetic failure), and surgical (treatment of lesion that involve dental implant like medication-related osteonecrosis of the jaw).
The bone level around the implant before the explantation was measured on panoramic radiographs (Sidexis XG, Sirona Dental Systems). The percentage of the implant length covered by bone was measured mesially and distally to the implant by considering the implant length as the 100%. Then the mean of the two measurements was calculated. The frequency of the implant covered by bone was grouped into four different categories 0–25%, 26–50%, 51–75%, and 76–100%. It was not possible to calculate the implant length covered by bone in millimeters as the implant length was unknown for most of the implants.
The frequency of the variables of interest (implant location, cause of implant removal, implant length covered by bone, implant removal success, and complications) was calculated and represented in percentage. Statistical analysis of categorical variables was calculated using the Chi-square test. The IBM SPSS Statistic v15 software package (SPSS Inc., Chicago, IL, USA) was used. Statistical significance was set at p value < 0.05.