Loaded hydroxylapatite-coated implants and uncoated titanium-threaded implants in distracted dog alveolar ridges

Abstract

The aim of this study was to determine the response of alveolar bone after it was augmented vertically with distraction osteogenesis, implanted with hydroxylapatite (HA)-coated implants and noncoated titanium-threaded implants, and subsequently loaded for 1 year. Eight dogs each had 4 implants placed horizontally into an edentulous mandibular quadrant. After integration, a distraction osteogenesis device was fabricated in the laboratory. An osteotomy was made to allow the crest of the alveolar ridge to be distracted vertically. After 10 mm of vertical distraction, the distraction devices were stabilized with light cured resin. After bone fill of the distraction gap was radiographically confirmed in all dogs at 10 weeks, 2 implants were placed into the ridges. Four dogs had threaded titanium implants placed, and 4 dogs had threaded HA-coated implants placed, with 1 implant in the distracted bone and 1 implant in adjacent nondistracted bone, for both groups. After 4 months for implant integration, bridges were fabricated and secured to the implants with screws. Crestal bone levels were evaluated by radiographs through 1 year of function. Animals were killed after 1 year of loading for histologic evaluation. The vertical ridge augmentation averaged 8.8 +/- 1.0 mm after 10 weeks of healing after distraction. Analysis of variance indicated a significantly greater change from baseline for HA-coated implants and for distracted bone sites. Histologic examination showed that bone had formed between the distracted segments creating an augmented ridge. The average thickness of the labial cortex in the distraction gap was significantly thinner than the lingual cortex in distracted bone or the lingual and labial nondistracted cortical bone. The presence of a dental implant did not significantly affect cortical bone thickness. Serial sections showed that implants remained integrated and functional without soft tissue inflammation. Dental implants placed into alveolar ridges augmented with the technique of distraction osteogenesis were functional for the length of this study.