5C,D) and the areas of new bone formation (arrows, Figs. 5C,D). Polarized light and Picrosirius red staining further demarcated the linear organization of the native bone (dotted line, Figs. 5E,F) from the crosshatched pattern seen in the new osteoid matrix (arrows, http://www.selleckchem.com/products/gsk1120212-jtp-74057.html Figs. 5E,F). Thus, the structure of the
new bone was woven in comparison to the lamellar organization of intact bone. We next evaluated the extent to which bone remodeling associated with implant placement affected these two osteoid matrices. Using alkaline phosphatase (ALP) activity to identify newly mineralizing bone matrix  and  we found only the new bone exhibited ALP activity; native bone showed no evidence of ALP activity (dotted line indicates native bone, arrows indicate ALP activity in Figs. 5G,H). The activity of osteoclasts, as measured by tartrate resistance acid phosphatase (TRAP) activity , was primarily evident on the remodeling surfaces of the new osteoid matrix, on both nasal and oral sides of the bone (Figs. 5I,J). TRAP activity was completely absent from the native maxillary cortex,
indicating a very low rate of bone turnover. TUNEL activity was used to identify cells undergoing apoptosis . TUNEL activity was minimal along the implant surface on day 14, in keeping with the deposition of new bone here; this website instead, TUNEL+ ve cells were found in areas of the native lamellar bone (Fig. 5K), indicating osteocyte cell death in this locale. We used immunostaining for proliferating cell nuclear antigen (Fig. 5J) to confirm that cells continued to proliferate in the peri-implant space and in the lacunae (Fig. 5L). Immunostaining for Osteocalcin (Fig. 5M),
Osteopontin (Fig. 5N), and Pro-collagen type I (Fig. 5O) verified that cells were actively differentiating into osteoblasts in the peri-implant space, and in the periosteum adjacent to the implant. Decorin (Fig. 5P) and Fibromodulin (Fig. 5Q), both markers of fibroblastic cells, were not expressed in the gap-interface, thus confirming that bone, and not fibrous tissue, formed in the peri-implant space. Many of our assumptions concerning oral implant osseointegration are extrapolated from experimental models studying skeletal tissue repair in long bones  and . We avoided this presupposition by directly studying oral implant osseointegration in an oral bone, the maxilla. First, we showed that in comparison learn more to long bone injuries, craniofacial bones are derived from cranial neural crest (Fig. 1). Second, we find that injuries to craniofacial bones tended to heal more slowly than analogous injuries to the tibia (Fig. 1). The reasons for this are not obvious but there are a number of other features that undoubtedly contribute to the difference in healing potential: for example, the marrow space in the tibia contains abundant numbers of osteoprogenitor cells, a robust blood supply, and stem cell niche signals  and , all of which are essential for new bone formation.