Comparative Histological and Histomorphometrical Evaluation of Marginal Bone Resorption Around External Hexagon and Morse Cone Implants: An Experimental Study in Dogs

Purpose: Aim of this study was to evaluate the histological and histomorphometrical differences at the marginal bone level with the use of 2 different implant-abutment assembly designs (the traditional External Hexagon and the Morse Cone tapered connections). Methods: Nine Morse Cone and 9 External Hexagon implants were inserted in 6 mongrel dogs. The Morse Cone implants were installed 2 mm below the crestal bone level, whereas the External Hexagon flush. The implants were retrieved after 2 months. Mean distance between the original level of coronal bone to the top of the implant and the mean distance between the top of the implant and the first bone-to-implant contact (fBIC) were recorded. Results: No significant differences were found when the mean distance between the original level of coronal bone to the top of the implant was evaluated; however, there were statistically significant differences in the mean distances between the top of the implants and fBIC, suggesting a smaller amount of bone loss or remodeling in the Morse Cone compared to the External Hexagon group. Conclusion: Subcrestal placement had a positive impact on crestal bone remodeling in Morse Cone implants.