Bone Healing at Functionally Loaded and Unloaded Screw-Shaped Implants Supporting Single Crowns: A Histomorphometric Study in Humans

Purpose: To evaluate histologically and histomorphometrically the effect of a delayed load on healing at implants with a moderately rough surface. Materials and Methods: Two solid titanium screw-shaped devices, 5 mm long and 3.5 mm in diameter, were inserted in the distal segments of the alveolar ridge of 16 volunteer patients in a nonsubmerged fashion. After 2 months, one implant was loaded, while the other was left unloaded. After 2 months, the two implants were collected from 10 patients using a sonic instrument, and ground sections were prepared from the biopsy specimens. Histomorphometric analyses were performed. Results: After 4 months of healing, biopsy specimens from 10 patients were available for analyses (n = 10). The total bone-to-implant contact percentage was 86.8% +/- 6.5% and 84.6% +/- 3.7% for loaded and unloaded implants, respectively. New bone was represented by 85.5% +/- 6.7% and 83.4% +/- 3.9% at the loaded and unloaded sites, respectively. A very small amount of old parent bone was found. The density of the mineralized bone was 76.8% +/- 8.3% for the loaded sites and 74.1% +/- 10.5% for the unloaded sites. The percentages of new and old bone densities were 69.0% +/- 8.3% and 7.8% +/- 3.9% at the loaded sites, and 65.9% +/- 10.3% and 8.2% +/- 4.5% at the unloaded sites, respectively. No statistically significant differences were disclosed. Conclusion: Applying a delayed load to implants supporting single crowns did not yield statistically significant differences, and only a tendency of higher osseointegration and bone density was observed at loaded sites compared with the unloaded sites.