Clinical observation on minimally invasive orthodontic extrusion of intruded immature central incisors

Objective To observe the clinical outcomes of traumatically intruded young permanent teeth after using a minimal invasive orthodontic repositioning method. Methods Eight patients aged from 7 to 11 years old presenting dental trauma were admitted to our department. A total of 11 injured maxillary incisors, with 9 severely intruded and 2 moderately intruded. All teeth were observed for spontaneous re-eruption for at least 1 month, before initiating orthodontic repositioning. Minimal invasive orthodontic repositioning were possible using the following method: (1) "2 × 4" nickel titanium wire appliance: single tooth moderately intruded with adjacent teeth erupted above 3/4; (2) removable appliance: severely and vertically intruded tooth, with adjacent teeth erupted less than 1/2 or traumatically dislocated; (3) removable appliance and "2 × 4" nickel titanium wire appliance: severely buccal or palatal intruded tooth, with adjacent teeth erupted less than 1/2 or traumatically dislocated. During the re-eruption status, pulp necrosis, loss of gingival attachment, marginal bone loss, root resorption and the condition of adjacent teeth were observed. Results (1) Re-eruption status: all the teeth were repositioned in good alignment with the adjacent teeth; (2) root resorption: 4 teeth showed mild root resorption. 2 teeth showed evidence of obvious periapical and lateral radiolucency before the repositioning, which were ceased and healed at the end of the treatment; (3) marginal bone loss: 2 teeth showed mild marginal bone loss; (4) pulp status: 3 mature teeth were root-treated with calcium hydroxide paste before the repositioning, 4 immature teeth were treated during the treatment, and 4 teeth maintained pulp vitality, one tooth showed root canal calcification. Conclusions If the traumatically intruded teeth show no signs of re-eruption, depending on the direction of intrusion, the stage of eruption of the adjacent teeth and the severity of the trauma, immediate repositioning should be initiate. "2 × 4" nickel titanium wire appliance, removable appliance or even the use of both in one unit should be a feasible choice to effectively reposition dislocated tooth, avoid root absorption, reduce the occurrence of marginal bone loss, and maintained pulp vitality. Key words: Dentition permanent; Tooth intrusion; Minimally invasive; Orthodontic extrusion; Root absorption