Fractal dimension analysis used to assess bone quality near hydroxyapatite-coated and non-coated titanium endosseous dental implants

The clinical fate of hydroxyapatite-coated titanium endosseous implants is controversial. Some researchers have found that coating implants with hydroxyapatite is advantageous, reporting significant success rates. Those researchers believe that the reasons reported for the failures (coating dissolution and increased microbial adhesion) no longer exist. Those who believe that hydroxyapatite-coated implants are not so advantageous admit there are short-term successes, but they believe coated implants will not have long-term success rates seen with the noncoated titanium implants.; In an attempt to diminish the controversy that exists, much work has been performed to analyze the biomaterials and biomechanics of various implant systems as well as to analyze the implant-bone interface. However little has been done to analyze the bone structure around the implant in human subjects. Fractal dimension analysis is a means of analyzing trabecular bone density and, to a degree, quality. Given this technique we hypothesize that fractal dimension analysis can be used to study the bone around implants and that there is a difference of fractal dimension between bone near hydroxyapatite-coated and noncoated implants.; An algorithm was developed using a surface area technique of fractal dimension. Our algorithm was first validated by using blocks of varying degrees of perceived roughness and then by using digitized dental radiographs of patients with osteoporosis/osteopenia. In both cases, a high fractal dimension was found to be associated with the low-density structure or with the image of greater perceived roughness. These results were not statistically significant (p > .05). However, they were sufficient to proceed with the main focus of this research.; The algorithm was then applied to digitized dental radiographs of hydroxyapatite-coated and noncoated endosseous dental implants taken over a 4-year period. There was no statistically significant difference between fractal dimension of bone near the 2 implant types, but there was a statistically significant difference between fractal dimension of the bone near the implants at the time of loading of the dental prosthesis (baseline) and 1 year of loading for both implant types (p < .05). Also, other researchers have seen no difference in clinical performance of these same implants. The hydroxyapatite-coated implants did have a higher fractal dimension for Years 1, 2, 3, and 4, which our algorithm indicates is a lower density situation.