Bone specimens

Twenty mandibles from fresh porcine cadavers were obtained from a local slaughterhouse. The animals did not show any macroscopic signs of any pathologic bone conditions. After removal of the surrounding soft tissue, the surfaces of the bone samples were thoroughly cleaned. Each sample was checked macroscopically for irregularities and a minimum thickness of 20 mm at the place of the intended implant placement was verified. All obtained samples were immediately used.

Surgery

In the following, a preparation wider than recommended by the company (also if narrower than the implants’ diameter) will be termed as over-dimensioned protocol (ODP).

Osteotomies were done following the manufacturer’s protocol, using sequences of varied diameter drills. One hundred and twenty implants (HiTec Tapered Self Thread implant, Hi-Tec Implants, Herzlia, Israel; 8 mm length and 3.3/3.75 diameter) were inserted either manually or machine-driven into porcine mandibles using SP or ODP. A manual insertion mode was used for implants inserted via SP (n = 45) or ODP (n = 30). A machine-driven mode was used for additional implants inserted via SP (n = 45). Drilling was conducted at 850 rpm and the implant was inserted at a speed of 15 rpm using a surgical motor for dental implants (Elcomed, type SA-310, W&H Dentalwerk Bürmoos GmbH, Bürmoos, Austria). Maximum insertion torque was set at 45 Ncm when implants were machine-driven, whereas manually inserted implants were drilled in by a hand ratchet at max. 45 Ncm.

Preparation protocol for standard osteotomy (SP)

Osteotomies were conducted in accordance with the manufacturer’s protocol. After exposure, the bone was penetrated to a depth equivalent to the implant length using the 2-mm internal irrigation drill. Using the 2.5-mm and 2.8-mm drill, the preparation for 3.3 mm implants was completed. To achieve the space for 3.75 mm implants, the 3.2-mm drill was also used (Fig. 1).