To compare primary stability of orthodontic miniscrews of pure titanium, of titanium alloy and of stainless steel presenting the same design in an in vitro model.
Method:
Thirty self-drilling miniscrews (ten of pure-titanium, ten of Ti6Al4V and ten of stainless steel) of same design and same dimensions (2 mm diameter and 12mm in length) were inserted into artificial bone blocks (Sawbones® 1,64g/cm3 cortical bone density, 0,48 g/cm3 trabecular bone density) with a 2-mm thick cortical layer. Axial pullout strength, maximum insertion torque (MIT) and cortical insertion time (CIT) were measured. The tip and thread of the miniscrews used for the pull-out strength test were observed by SEM.
Result:
No statistical differences between miniscrews of pure-titanium, Ti6AL4V and stainless steel were found regarding axial pullout strength. However, MIT values were significantly lower for pure-titanium devices compared to stainless-steel and Ti6Al4V devices. Miniscrews of stainless steel presented the shortest values of CIT. The tips and threads of the stainless steel devices presented less blunting than TI6Al4V and pure Titanium.
Conclusion:
In this in vitro study, the miniscrews material influenced primary stability. Stainless steel and Ti6Al4V presented higher values of MIT than pure Titanium. Into thick cortical bone, stainless steel allow for an easy and quick insertion of miniscrews.