Bone healing and the effect of implant surface topography on osteoconduction in hyperglycemia.

Dental implant failures that occur clinically for unknown reasons could be related to undiagnosed hyperglycemia. The exact mechanisms that underlie such failures are not known, but there is a general consensus that bone growth is compromised in hyperglycemia. Nevertheless, contradictory findings exist related to peri-implant bone healing in hyperglycemia. We hypothesized that hyperglycemia delays early bone healing by impeding osteoconduction, and that the compromised implant integration due to hyperglycemia could be abrogated by using nanotopographically complex implants. Thus we undertook two parallel experiments, an osteotomy model and a bone in-growth chamber model. The osteotomy model tracked temporal bone healing in the femora of euglycemic and hyperglycemic rats using micro computed tomography (microCT) analysis and histology. The bone in-growth chamber model used implant surfaces of either micro- or nanotopographical complexity and measured bone-implant contact (BIC) using backscattered electron imaging in both metabolic groups. Quantitative microCT analyses on bone volume, trabeculae number and trabeculae connectivity density provided clear evidence that bone healing, both reparative trabecular bone formation and remodeling, was delayed in hyperglycemia, and the reparative bone volume changed with time between metabolic groups. Furthermore, fluorochrome labeling showed evidently less mineralized bone in hyperglycemic than euglycemic animals. An increased probability of osteoconduction was seen on nano-compared with microtopographically complex surfaces, independent of metabolic group. The nanotopographically complex surfaces in hyperglycemia outperformed microtopographically complex surfaces in euglycemic animals. In conclusion, the compromised implant integration in hyperglycemia is abrogated by the addition of nanotopographical features to an underlying microtopographically complex implant surface.

Low-temperature particulate calcium phosphates for bone regeneration.

BACKGROUND: Low-temperature synthesized calcium phosphates are produced by mixing calcium phosphate powders in an aqueous solution resulting in a precipitated phase. These compounds can be formulated in several forms (e.g. injectable cements and implantable blocks), and are commonly used as bone substitutes and drug delivery systems for the treatment of bone defects. As bone substitutes, calcium phosphates in general offer the advantages of being biocompatible and osteoconductive. AIMS: The present work employed a machine-based process to derive a reproducible preparation method for low-temperature calcium phosphate particulate (LTCP). The in vivo outcomes of LTCP were compared with those of three commercially available bone substitutes by histomorphometric measurements of bone formation and material degradation in a rat femur implantation model. MATERIALS & METHODS: Specifically, LTCP, anorganic bovine bone (AB), bioactive glass (BG), and demineralized bone matrix (DBM) were implanted in defects created in the distal aspect of rat femora. Reparative bone and particulate volumes of these biomaterials were evaluated post-operatively using micro-computed tomography and histological analyses at 3, 6, 12, and 16 weeks. RESULTS & DISCUSSION: Results showed that, despite invoking bone formation, AB, BG, and DBM were found un-resorbed in situ at 16 weeks. Conversely, LTCP showed an early increase in bone formation as well as clear evidence of complete degradation and reparative bone remodelling, resulting in the total reconstitution of the marrow cavity and marrow tissue. CONCLUSION: LTCP promoted increased early bone formation, associated with an improved degradation rate, compared with the other three bone-substitute biomaterials tested.

Intraosseous leiomyoma of the mandible.

An intraosseous leiomyoma arising within the mandible was diagnosed in a 24-year-old woman. Clinically, a nodular swelling of the lower border of the mandible was noted. Radiographically, a unilocular ellipsoid radiolucency, loss of the lower border of the mandible, and tooth resorption were observed. The mitotic count was 0.4 per 10 high-power fields, which supported the benign nature of the tumor. The clinical and histologic parameters for distinguishing between benign and malignant smooth muscle neoplasms are discussed.

Intraosseous leiomyoma of the mandible / Leiomioma intra-ósseo da mandíbula

An intraosseuos leiomyoma arising within the mandible was diagnosed in a 24-year-old woman. Clinically, anodular swelling of the lower border of the mandible was noted. Radiographically, a unilocular ellipsoid radiolucency, loss of the lower border of the mandible, and tooth resorption were observed. The mitotic count was 0.4 per 10 high-power fields, which supported the benign nature of the tumor. The clinical and histologic parameters for distinguishing between benign and malignant smooth muscle neoplasms are discussed