The effect of implant shape and screw pitch on microdamage in mandibular bone.

PURPOSE: The aim of this study was to investigate the effect of implant shape and screw pitch on microdamage in bone during insertion of dental implants. MATERIALS AND METHODS: Thirty custom-made implants (length, 10 mm; diameters, 4.1 mm; cylindrical, tapered, and taper-cylindrical shapes; screw pitches, 1.25 and 0.8 mm; classified as 1.25C, 0.8C, 1.25T, 0.8T, 1.25TC, 0.8TC) were placed with a surgical device in the mandibles of eight goats. Two implant sites were prepared in the edentulous area on each side of the mandible. Implants were placed in a randomized order. Immediately after placement of the implants, the bone blocks with the implants were collected, bulk stained with basic fuchsin, embedded in methyl methacrylate, and sectioned. Histomorphometric quantification of the microcrack length (Cr.Le, mum); microcrack surface density (Cr.Le/B.Ar, mum/mm(2) ), and damaged bone area fraction (DB.Ar/B.Ar, %) were measured. RESULTS: The Cr.Le, Cr.Le/B.Ar, and DB.Ar/B.Ar values of 0.8TC group were 80.96 +/- 17.55, 478.75 +/- 51.85, and 4.40 +/- 0.36, respectively. All these parameters of microdamage induced by 0.8TC were significantly lower than those induced by other five types of implants (p < .05). CONCLUSION: Taper-cylindrical implants with 0.8 mm screw pitch caused the least microdamage to the bone in comparison with the other five types of implants during placement of implants.