Topographical and elemental changes of retrieved stainless steel and titanium mini-implants after orthodontic treatment

Objective To investigate the surface changes and elemental composition of retrieved titanium and stainless steel orthodontic mini-implants and to determine the type of bone at the mini-implant–alveolar bone interface. Materials and methods Surface characteristics, such as dullness, cracks, craters, and blunting of retrieved stainless steel and titanium mini-implants placed for orthodontic anchorage were studied with scanning electron microscopy and the change in composition was assessed with energy dispersive X-ray spectroscopy analysis. Bone tissue samples adjacent to mini-implant surface were examined histologically to identify the bone type. Results The mean scores showed that the surface defects were 26% in titanium mini-implant threads and 33.33% of stainless steel mini-implant threads at the tip portion which were not statistically significant on comparison (P = 0.75). Comparing mean net wt% of carbon, oxygen, and nitrogen elements adsorbed on the surface of retrieved and control groups of titanium mini-implants yielded statistically significant results (P = 0.001). The histological sections of bone particles from mini-implant surface showed lamellar bone. Conclusions Blunting (of the tips and threads) of all retrieved mini-implants were evident on SEM images and craters were observed in body region of retrieved stainless steel mini-implant. The retrieved titanium implants showed oxygen, carbon, calcium, and nitrogen on the surface, whereas only carbon and oxygen elements were found on retrieved stainless steel implants. The elemental oxygen (22.67%) was higher in the titanium group and a higher carbon (7.43%) in the stainless steel group. Numerous lacunae, resting lines, and osteocytes were found in bone tissue from mini-implant surface.