Bone remodeling in immediately loaded and unloaded titanium dental implants: a histologic and histomorphometric study in humans

Remodeling is thought to prevent microdamage accumulation caused by repetitive loading and to increase the fatigue life of bone. The bone remodeling rate (BRR) is the period of time needed for new bone to replace the existing bone and to allow for the adaptation of bone to its environment. BRR is expressed as a percentage or volume of new bone within a specific time period. The aim of the present study was to evaluate bone remodeling events on submerged and immediately loaded dental implants. Twelve patients with edentulous mandibles participated in this study. All patients were rehabilitated with fixed mandibular prostheses, with 10 dental implants per patient. An additional implant was inserted in the most distal posterior mandibular jaw region. In 6 patients, these additional implants were loaded with a fixed provisional prosthesis the same day of the implant surgery and loaded. In the other 6 patients, the additional implants were left submerged and not loaded. After 6 months, all the additional implants were retrieved with a trephine. The percentage of woven and lamellar bone, number of osteoclasts and osteoblasts, and percentage of bone labeled by tetracycline at 0.5 mm and 2 mm from the implant surface were evaluated. The percentage of lamellar bone, number of osteoblasts, and percentage of bone tetracycline labeling was significantly higher in the loaded implants than in the unloaded implants (P =.0001). Also in the loaded implants, the percentage of woven and lamellar bone, number of osteoclasts and osteoblasts, and percentage of bone tetracycline labeling was significantly higher at 0.5 mm than at 2 mm from the implant surface (P =.0001). No such differences were found in unloaded implants (P =.377). In conclusion, we found that (1) loading appeared to stimulate bone remodeling at the interface, (2) a higher percentage of lamellar bone was found in loaded implants, (3) the percentage of bone labeling was higher at the interface of loaded implants, (4) no differences were found in the BRRs between immediately loaded and unloaded implants, and (5) immediate loading had not interfered on the lamellar bone formation at the interface and had not produced formation of woven bone at the interface.