High doses of zoledronic acid induce differential effects on femur and jawbone microstructure.

OBJECTIVES: The aim of this study is to investigate the long-term effects on jaw and femur bone induced by oncologic doses of zoledronic acid in a young rat model. MATERIAL AND METHODS: Six 12-week-old male Wistar rats received zoledronic acid (0.6 mg/kg) and six control rats received saline solution in the same volume. Compounds were administered intraperitoneally in five doses every 28 days. Euthanasia was performed 150 days after therapy onset. After animal sacrifice, their mandibles and femurs were scanned ex vivo using a high-resolution (14 µm) micro-computed tomography. Morphometric bone parameters were calculated using CT-Analyzer (Bruker, Belgium) between the first and second mandibular molars and in the distal femur metaphysis and epiphysis. RESULTS: The treatment group as compared to the controls showed a significantly (p < .05) increased bone quantity (↑BV/TV, ↓Po[Tot], ↑Tb.Th), bone density (↑TMD, ↑BMD), and osteosclerosis of the trabecular bone (↓Tb.Sp, ↓Conn.Dn, ↓Tb.Pf, ↓SMI) in all anatomical sites. Bone remodeling suppression due to zoledronic acid treatment was more pronounced (p < .05) in the femoral metaphysis relative to the mandible and epiphysis. The exploratory linear discriminant analysis showed that for the mandible, it was mainly the bone quantity-related morphometric indices (BV/TV and Tb.Th), while for the femoral epiphysis and metaphysis, it was bone structure-related (Tb.Pf and Tb.N), which are of primary importance to study the treatment effect. CONCLUSION: High doses of bisphosphonates can differently affect the bone quantity, density, and structure in long bones and jawbones. In the metaphysis, bone changes were primarily concentrated in the region of the growth plate. Future studies may consider the use of bone morphometric indices to evaluate the effect of bisphosphonates.

Morphometric evaluation of bone regeneration in segmental mandibular bone defects filled with bovine bone xenografts in a split-mouth rabbit model.

BACKGROUND: Bovine bone grafts have been widely used in dentistry for guided tissue regeneration and can support new bone formation in direct contact with the graft. The aim of this study was to compare the morphometric and bone density changes after using two different bovine bone graft blocks in segmental osseous defects in the mandible of rabbits following different postoperative periods. MATERIAL AND METHODS: Critical size segmental defects were surgically created bilaterally in the jaw of 18 rabbits. The defects were filled with either deproteinized bovine bone mineral with 10% collagen (DBBM-C; BioOss Collagen®), lyophilized bovine medullary bone (LBMB; Orthogen®), or left untreated according to a split-mouth design. Animals were sacrificed after 3 or 6 months of healing. The hemimandibles were scanned ex vivo using a high-resolution (19 µm) microcomputed tomography. Morphometric and bone density parameters were calculated in the region of the defect using CT-Analyser (Bruker). Initial graft blocks were used as baseline. RESULTS: DBBM-C presented a denser microarchitecture, in comparison to LBMB at baseline. DBBM-C and LBMB grafted regions showed a similar progressive remodeling, with a significant decrease in structure complexity and maintenance of bone volume fraction during the postoperative follow-up periods. Both graft materials showed an enhanced bone replacement and more complex structure compared to untreated defects. The apparent fusion between the graft and host bone was observed only in the defects filled with LBMB. CONCLUSION: LBMB grafts showed a similar behavior as DBBM-C regarding structural remodeling. In LBMB samples, apparent integration between the host bone and the graft was present.