Effect of Hafnium Coating on Osseointegration of Titanium Implants: A Split Mouth Animal Study

The behaviour of hafnium as surface coating in biological environments has not been studied. Little is known about osseointegration of hafnium-coated titanium implants. Thus, further studies of hafnium coating under biological conditions are required in order to determine the suitability of this material, as a surface coating for biomedical application. The aim of the study is to analyse the difference between hafnium-coated titanium and uncoated titanium by evaluating the osseointegration ability of hafnium metal and mechanism of which promotes better bone integration. The study was conducted with a split mouth design on 16 Wistar Albino rats of both sexes, at the age of 6-7 months, weighing $2526.5\pm 74.4\text{g}$ . Self-tapping titanium osteosynthesis screws ( $4\text{mm}\times 2\text{mm}$ ) (LeForte System Bone Screw®) were implanted in the mandible of rats: Group A (pure titanium screws, $n=12$ ) and Group B (hafnium-coated screws, $n=12$ ). The implanted screws’ stability was checked and noted with a specially customised torque apparatus during insertion and removal of implant. The tissue sections were then processed for hematoxylin and eosin and Masson’s trichrome for bone and connective tissue examination, after 4 and 8 weeks of placement. Hafnium coating appears to have offered similar biocompatibility (aspartate transaminase (AST), alanine aminotransferase (ALT), and creatine kinase (CK) enzyme assay), statistically significant improvement (independent Student’s $t$ -test, $p<0.05$ ) in insertion torque ( $25.42\pm 3.965$ ) and removal torque ( $29.17\pm 2.887$ ) than commercially pure titanium with insertion torque ( $22.08\pm .575$ ) and removal torque ( $25.42\pm 2.575$ ). Hafnium coating in the rat mandible showed promising osseointegration with good tissue biocompatibility. Further human trials of hafnium-coated implants are needed to understand the biological behaviour better to enhance clinical performance.