Effect of ultraviolet photoactivation of titanium on osseointegration in a rat model

Purpose: The objective of this study was to determine whether ultraviolet (UV) light treatment of titanium implants could enhance osseointegration to sufficiently overcome the negative aspects of shorter implants in a rat femur model. Materials and Methods: Acid-etched miniature titanium implants with lengths of 2 mm (longer implants) and 1.2 mm (shorter implants) were prepared. Some of these implants were treated with UV light for 48 hours prior to surgery. The strength of osseointegration generated by these implants was evaluated using a biomechanical implant push-in test in a rat model. Periimplant osteogenesis was examined by scanning electron microscopy for tissue morphology and energy dispersive x-ray spectroscopy for elemental composition. Results: Push-in test values for the longer implants were 80% and 100% greater than those of the shorter implants at weeks 4 and 8 of healing, respectively. UV treatment of the shorter implants significantly increased their push-in value, resulting in a 100% higher value than untreated longer implants at week 2 and a push-in value that was equivalent to that of the untreated longer implants at weeks 4 and 8. Scanning electron micrographs and energy dispersive x-ray spectroscopic examinations after push-in testing revealed that the UV-treated implant surfaces were covered more extensively by bone or tissue remnants containing calcium and phosphorous than the untreated surfaces. The titanium surfaces were converted from hydrophobic to super - hydrophilic status after UV treatment, although the cause-result relationship between the acquired superhydrophilicity and biologic effects remained unclear. Conclusions: Within the limits of this investigation, UV light pretreatment substantially enhanced the osseointegration capacity of acid-etched titanium implants. The deficiencies of osseointegration in implants with a 40% shorter length were overcome by UV treatment in the rat model using miniature implants. These results need to be confirmed in other animal models and implants that more closely resemble human dental implants to determine the true clinical significance.