Orthodontic Treatment Of Impacted Mandibular First And Second Molars

Objective: To evaluate effects of surgical-orthodontic treatment in unilateral impacted mandibular first and second molars.Methods: A case was selected in 2014,who was a male,15 years old and unilateral mandibular first and second molars impaction.The mentum was obvious and mentolabial sulcus was deep.Normal centre line and over jet,deep over bite Ⅲ°.The left molar relationship was neutral and crossbite,the right side of maxillary first molar was too long and mandibular first and second molars was impacted.There were some space between lower second premolar and canine.By analysis of his panoramic radiograph,projection measurement analysis and CT 3D reconstruction analysis,the impacted mandibular first molar was distally inclined and the impacted mandibular second molar was mesially inclined.Model analysis: the crowding of maxillary arch was 0mm,the crowding of mandibular was 4.7 mm because of the third molar germ.The left spee curve was 4mm and the right was 0mm.Pont index showed that maxillary arch width of first molar was a little smaller and Bolton index was normal.Projection measurement analysis: FMA 14.6°、OP-FH 1°、OP-SN 4.5°、FHI 0.98、ANS-Me56mm、ANS-Me/N-Me 51.7%,meant low-angle;NA-PA-6.9°、Po-NB 5.8mm、Y axis 60°,meant the obvious mentum;IMPA 86.9°、L1-NB(°)5.4°、L1-NB(mm)-0.6mm,meant lingual inclination of mandibular incisor;ODI 87 meant deep over bite.Used straight wire appliance for treatment,put a pair of micro implant into the buccal and palatal side of upper first molar for intruding the molar,adhered bite turbos on the lingual of maxillary incisor,used surgical exposure of mandibular second molar,expand space,and used orthodontic traction and T-loop for uprighting molars.Results: After treatment,the impacted mandibular first and second molars were moved to their normal positions with vital pulp and healthy periodontium.Comparing the changes between pre-treatment and post-treatment: FMA increased 1.4°、OP-FH increased 6.1° 、 OP-SN increased 6.1° 、 FHI decreased 0.02 、 ANS-Me increased1.8mm、ANS-Me/N-Me increased 0.7 %,indicated that the mandible turnd to clockwise with the treatment of impacted molars and the increase of occlusal height;IMPA increased 6.1°、L1-NB(°)increased 7.1°、L1-NB(mm)increased 1mm,meant that lingual inclination of mandibular incisor was improved;Y axis increased 0.9°,indicated the change of the mentum and the soft tissue profile showed improvement.Conclusion: For this case,that was unilateral mandibular first and second molars impaction,we can get a good therapeutic effect by using surgical-orthodontic treatment.