Frequency of Ankylosis, Loss of Pulp Vitality and External Root Resorption after Root Contact with Mini-screw

To evaluate the frequency of ankylosis, loss of pulp vitality and external root resorption after intentional root contact with mini-screw. Sixty maxillary and mandibular second, third, and fourth premolars teeth of five mature beagle dogs were randomly assigned into three experimental groups. Premolars teeth at group I, received a mini-screw (6-mm length, 1.5-mm diameter, self drilling) which was removed immediately after contact with the root. Group II consisted of teeth that received mini-screw and the screw left in situ for 15 weeks. In group III once contact was made with mini-screw, the teeth were shifted away from the screw with brackets and Titanium closed coil spring tightened to another bonded orthodontic brackets on the neighbor teeth. Group IV was the control group. The specimens were decalcified, stained and evaluated histologically to determine the presence/absence of root resorption, ankylosis and tooth vitality. There were no signs of ankylosis, root resorption, moderate to severe inflammation or necrosis within the pulp in any experimental group. Ankylosis, pulp necrosis and sever root resorption are not common clinical outcomes when mini-screw contacts the root. Repair after contact with mini-screw depends on the severity of invasion. More severe invasion needs further time necessary for repair.