Application Of Micro-implant Anchorage(MIA)in The Treatment Of Gummy Smile

ObjectivesThe experiment is aimed to evaluate clinical efficacy of MIA intruding the anterior teeth to treat the gummy smile, by studying the changes of maxilla-ry incisors and first molars in both vertical and sagittal direction as well as facial soft tissue which are intruded by MIA. Meanwhile it provides clinical references and theoretical basis for orthodontic treatment of gummy smile a-nd intruding the anterior teeth.Methods10patients were selected whose average age is24.90±5.15years old in this research. Their anterior deep overbite is more than Ⅱ degree. Their maxillary alveolar bone also overgrew vertically. The relation between upper lip and teeth is not adjustable. The gum expose of patients selected is over2mm.9patients were pulled out four maxillary first premolars while another patient only had his14and24pull out due to lack of a mandibular anterior teeth.O-PAK was used in the research. MIA implanted in the middle of maxillary lateral incisor teeth and maxillary central incisors, and then was loaded immediately. The unilateral afterburner was50g. X-ray cephalometrical film and panoramic radiograph were shot down before and after being intruded respectively. Photos both with smile face and without smile face were shot down as well. The measurements include changes of maxillary central incisors and maxillary molars in vertical and sagittal direction before and after being intruded(U1-PPmm、U1-PP°、U6-SN°、U6-PPmm and U6-PP°), the changes of MP-FH,OP-SN,Y axis angle, NLA, ULL and UL-EP. They also include the reduced amount of clinical crown of tooth as well as OB,OJ.SPSS13.0software was used for statistical analysis of the measurement results. Results10patients are in good condition of oral hygiene. Symptoms of swelling and bleeding have not happened on their gingiva except that only one patient had his implant Anchorage loose. The average intruding time was (5.90±0.74) months. There is no feeling of pain suffered from hot and cold stimulation appeared on maxillary anterior teeth after treatment.1. Results of X-ray Analysis:(1) X-ray cephalometrical film anlaysis:After treatment,the resistance center of the upper central incisor was intruded (2.10±0.57) mm, U1-SN angle was decreased (11.70±0.89)°, Spr-PP was decreased (1.70±0.48) mm, NLA and ULL was increased obviously, UL-EP,OB and OJ was decreased, P<0.01; MP-FH angle,U6-PP angle and U6-PP was essentially flat, P>0.05.(2) Panoramic radiograph anlaysis:Maxillary anterior teeth apical were not found obviously absorbed.2.Model Analysis:The length of maxillary central incisors clinical crown was decreased (0.80±0.33) mm.The length of maxillary lateral incisor clinical crown was decreased (0.77±0.25) mm.The length of maxillary canine clinical crown was decreased (0.70±0.26) mm, P<0.01.3.Results of Gingival Exposure Analysis:After treatment, nine patients’gummy smile disappeared. One patient had his Gingival Exposure significantly reduced while smiling. The average reduction of Gingival Exposure is (2.83±0.17) mm.Conclusions1.The utilization of MIA can effectively intrude anterior teeth and cure gummy smile caused by excessive development of the anterior alveolar bone.2.The treatment of MIA will not cause the raise of maxillary molars.And1/3of the face lower will not increase. MIA is suitable for patients with high-angle.3. MIA simplifies clinical operation. It does not reply on the cooperation of patients. The comfort and curative effect of MIA is generally recognized.