Roughness and wettability effect on histological and mechanical response of self-drilling orthodontic mini-implants.

Abstract

Self-drilling orthodontic mini-implants can be used as temporary devices for orthodontic treatments. Our main goal was to evaluate surface characteristics, roughness and wettability, of surface modified mini-implants to increase their stability during orthodontic treatment without inducing bone fracture and tissue destruction during unscrewing. Modified mini-implants by acid etching, grit-blasting and its combination were implanted in 20 New Zealand rabbits during 10weeks. After that, the bone-to-implant (BIC) parameter was determined and the torque during unscrewing was measured. The surface characteristics, roughness and wettability, were also measured, onto modified Ti c.p. discs. Acid-etched mini-implants (R a≈1.7μm, contact angle (CA)≈66°) significantly improved the bone-to-implant parameter, 26%, compared to as-machined mini-implants (R a≈0.3μm, CA≈68°, BIC=19%) due to its roughness. Moreover, this surface treatment did not modify torque during unscrewing due to their statistically similar wettability (p>0.05). Surface treatments with higher roughness and hydrophobicity (R a≈4.5μm, CA≈74°) lead to a greater BIC and to a higher removal torque during unscrewing, causing bone fracture, compared to as-machined mini-implants. Based on these in vivo findings, we conclude that acid-etching surface treatment can support temporary anchoring of titanium mini-implants. This treatment represents a step forward in the direction of reducing the time prior to mini-implant loading by increasing their stability during orthodontic treatment, without inducing bone fracture and tissue destruction during unscrewing.