Histomorphometric Analysis and Removal Torque of Small Diameter Implants With Alternative Surface Treatments and Different Designs
This study was designed to investigate the histomorphometric and biomechanical comparison of small-diameter implants with different designs. These implants can be placed surgically in narrow bone spaces, such as the lower incisor region, that have low occlusal loading. Specimens of screw-shaped pin implants were designed for the study. These specimen implants were divided into 6 groups: group 1, machined implants; group 2, resorbable blast media (RBM)-treated implants; group 3, machined implants with a long vertical groove; group 4, RBM-treated implants with a long vertical groove; group 5, RBM-treated implants with a vertical groove on the upper thread; and group 6, RBM-treated implants with a vertical groove on the lower trunk. The specimen implants were placed surgically on the medial side of the rabbit tibia. Animals were sacrificed 2, 4, and 8 weeks after surgery. The removal torque was measured and tissues were prepared for histologic and histomorphometric analysis. The bone-to-implant contact and the percentage of the bone area inside the threads were measured. RBM-treated implants with vertical groove groups showed significantly higher values of removal torque, bone-implant contact, and bone area rate than the ones of machined surface groups.Abstract
Diagram of a specimen of the titanium small diameter implant. It is screw-shaped, 2 mm in diameter, 6 mm in length and made of grade 5 titanium (Slimplant, YK-pros). It was prepared with 2 types of surface: machined (1, 3) and resorbable blast media (RBM)-treated (2, 4, 5, 6). Vertical groove was applied at an angle of 45° and at a depth of 0.5 mm from the center of 4 experimental implants to provide resistance to mechanical loosening. The implant specimens were divided into 6 groups: group 1, machined implants; group 2, RBM-treated implants; group 3, machined implants with a long vertical groove; group 4, RBM-treated implants with a long vertical groove; group 5, RBM-treated implants with a vertical groove on the upper thread; and group 6, RBM-treated implants with a vertical groove on the lower trunk.
Mean and standard deviation of removal torque for 6 groups of implant at 2, 4, and 8 weeks. Group 1, machined implants; group 2, resorbable blast media (RBM)-treated implants; group 3, machined implants with a long vertical groove; group 4, RBM-treated implants with a long vertical groove; group 5, RBM-treated implants with a vertical groove on the upper thread; and group 6, RBM-treated implants with a vertical groove on the lower trunk. *Significant difference, P < .05.
Histologic sections of machined and resorbable blast media (RBM)-treated implant 2, 4, and 8 weeks after implantation in rabbit tibiae (original magnification ×40). (a) Machined implant at 2 weeks. (b) RBM-treated implant at 2 weeks. (c) Machined implant at 4 weeks. (d) RBM-treated implant at 4 weeks. (e) Machined implant at 8 weeks. (f) RBM-treated implant at 8 weeks. I indicates implant fixture; B, bone marrow. New bone formation can be observed (blue arrow). The overall features of the RBM-treated implant were similar to those of the machined implant. However, at many sites the new bone could not be distinguished from the adjacent preexisting bone, due to the almost complete formation of compact bone. In general, the connectivity of the compact bone was greater in the RBM-treated implant than in the machined implant.
Figure 4. The values of percentage of bone to implant contact at 2, 4, and 8 weeks. *Significant difference, P < .05. Figure 5. The values of bone area at 2, 4, and 8 weeks. *Significant difference, P < .05.
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