Ultraviolet-C irradiation to titanium implants increases peri-implant bone formation without impeding mineralization in a rabbit femur model

Abstract

Objectives. Volume and bone quality of peri-implant supporting bone, in particular, at implant neck region, as well as bone–implant contact ratio, is important for long-term stability of implants. Ultraviolet-C (UVC) irradiation is known to enhance the osseointegration capability of titanium implants. However, the histological determination was performed only on a rat model, but not pre-clinical animal model such as a rabbit model. The purpose of this study was to determine the effects of UVC irradiation on titanium implants on the volume and mineral density of peri-implant supporting bone formation in a rabbit femur model. Materials and methods. Acid-etched pure titanium screw implants with or without 3 mW/cm² UVC irradiation for 48 h were placed in rabbit femur diaphyses. Peri-implant bone tissue formation was analyzed at 3 and 8 weeks post-operatively by histology and micro-CT-based bone morphometry after calibration with hydroxyl apatite phantoms. Results. UVC pre-irradiated implants accumulated a higher density of cells and thicker and longer bone tissue attachments that continued into the inner basic lamellae of the surface of existing cortical bone at 3 and 8 weeks than the implants without irradiation. Although the bone mineral density around both implants was equivalent to that of the existing cortical bone, bone volume was greater with UVC pre-irradiation in two-thirds or more of the apical region throughout the observation period. Conclusions. These results indicate that UVC treatment increased the volume of cortical-like bone tissue in the coronal region of titanium implants without deterioration of bone mineral density.

Key Words:

• contact osteogenesis
• microCT
• photo-functionalization
• osseointegration
• surface modification

Acknowledgment

This research was supported by Oral Health Science Center Grant hrc8 from Tokyo Dental College, and by a Project for Private Universities: matching fund subsidy from MEXT (Ministry of Education, Culture, Sports, Science and Technology) of Japan, 2010–2012.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.