Cortical and Trabecular Bone Healing Patterns and Quantification for Three Different Dental Implant Systems

Abstract

The present study hypothesized that different bone healing patterns through initial stages of osseointegration would be observed when three distinct commercially available implant systems (Nobel Groovy, Implacil, and Zimmer TSV) were used, leading to significant variations in histometric levels of total bone and new bone formation during the osseointegration process. Materials and Methods: A total of 48 implants were placed bilaterally on the tibias of eight beagle dogs and allowed to heal for 2 and 6 weeks. Following euthanasia, nondecalcified specimens were processed for morphologic and histometric evaluation. Bone-to-implant contact (BIC) and new bone area fraction occupancy (BAFO) analyses for native and new bone were performed along the whole perimeter of each implant and separately for the cortical and trabecular bone regions. Results: Morphologic evaluation of cortical bone presented different healing patterns and osseointegration levels for different implant systems as time elapsed in vivo. Interfacial remodeling was the chief healing pattern in Zimmer implants, while a combination of interfacial remodeling and healing chambers was observed in Nobel and Implacil implants. When trabecular bone was evaluated, similar bone healing patterns were observed between systems despite different levels of osseointegration observed as a function of implantation time, implant system, and native and/or new bone BIC and BAFO. Conclusion: Different implant systems led to different healing patterns during early stages of osseointegration. Such variation in pattern was more noticeable in the cortical regions compared to the trabecular regions. The variation in bone healing pattern did significantly influence overall indicators of native and new BIC and BAFO during the osseointegration process. The postulated hypothesis was accepted.

Histological and Histomorphometrical Evaluation of a New Implant Macrogeometry. A Sheep Study

“…In a rabbit study, the use of a, probably, too traumatic technique led to the formation of a 200-500 micron area of necrosis [18]. A way to decrease the levels of these forces at the interface could be an implant site with the same diameter of the external portion of the implant [13,17,19,20]. A consequence of this technique could be, however, a decrease of the primary stability [9].…”

“…Wound or healing chambers have been introduced, in the last two decades, in the macrodesign of a few implant types [21][22][23][24]. Inside these healing chambers there is, first of all, the formation of a blood clot, characterized by the presence of many red blood cells immersed in a fibrin network [23] that progresses to the formation of an osteogenic stroma, rich in blood vessels [23,25], into which the osteogenic cells could migrate [13,17,19,20] to produce bone via an intramembranous-like path [21]. Moreover, in many cases, it will be possible to see a nucleation of bone throughout the healing chambers [17].…”

“…In the last decade, several paper have reported that, in press-fit conditions during implant insertion, no space was present between implant and bone, while, on the contrary, when there were lower degrees of compression of the peri-implant bone, a higher amount of bone formation was observed [7][8][9][10]. The macrogeometry of the implant is then considered a factor of great importance in the process of osseointegration [8,9,11,12], and expectations of an improved bone healing via implant macrostructure modifications have been reported [13]. An ideal implant shape should provide a balance between compressive and tensile forces.…”

Biomaterial and biomechanical considerations to prevent risks in implant therapy

“…The hybrid healing osseointegration pathway has been utilized in an attempt to obtain devices that are atemporally stable and is a combination of features presented in the interfacial remodeling and healing chambers osseointegration pathways. Screw‐type implants with large thread pitch and outer to inner thread diameter differences have been designed to allow surgical instrumentation sufficiently large for the formation of healing chambers between threads, implant inner diameter, and bone instrumented walls . For such an implant design configuration, primary stability is obtained by the interaction between the outer regions of the threads that engage bone and such initial stability is proportional to the thread design and the amount of mismatch between implant outer thread and osteotomy diameters.…”

“…Hence, this osseointegration pathway simultaneously presents bone remodeling where engagement between implant and bone occurred, resulting in stability loss that is supposedly compensated by the rapid woven bone formation in the healing chambers formed between threads. Unlike screw‐type implant systems that result in interfacial remodeling osseointegration and plateau root form implants that osseointegrate through healing chambers, implant systems deliberately designed for this purpose are relatively new in the market . Thus, long‐term human retrieved samples are not yet available for adequate assessment of the effect of this healing pathway on long‐term bone morphologic evolution.…”