The Clinical Study Of Distalizing Of Whole Dentition With Micro-implant Anchorage

[Objective] The purpose of this study is to evaluate the clinical effect of distalizing whole dentition when micro-implant is used as anchorage in eleven adult patients with bimaxillary protrusion and mild crowding. Position changes of first molars and incisors were measured in sagitttal and vertical direction to evaluate the amount of molar and incisor distalization and character of tooth movement. The differences in craniofacial hard and soft, dental measurements were also analyzed through study cast and cephalometric rentgenogram and panoramic. Root resorption in the maxillary incisor and mandibular incisor were evaluated as well.[Method] Based on the selective criteria, Eleven adults with moderate bimaxillary arch protrusion cases were selected to be treated with straight wire technique.Four males and seven female with an average age of21.7years old. The third molars were extracted. Implants were placed on infrazygomatic crest in the maxillary and onbuccal shelf in the mandible. Four draw hooks were welded on the arch wires between the lateral incisor and the canine. A NiTi coil spring was attached from the micro-implant to draw hook,250g force per side to.distalize the whole dentition. Cephalometrics and panoramic were taken before and after treatment, and the changes of hard-tissue and soft-tissue were studied, Root resorption in the maxillary incisors and mandibular incisors were evaluated.[Results]1. Micro-implants remained stable during treatment except four losin in the process,with a failure rate of9.09%.2. Changes of incisors:The incisors were significantly retracted after treatment with4.27°decreased in U1-SN,6.46°ecreased in L1-MP and6.59°in U1-L1(p<0.05); Significant changes were observed in the distalization of the upper incisor3.23mm at crown level and0.81mm at root level coupled with0.29mm intrusion (p<0.05); Significant changes were observed in the distalization of lower incisors3.14mm at the crown level and0.70mm at the root level accompaned by0.68mm intrusion (p<0.05).The distalization of incisors was presented as a distal tipping movement.3. Changes of molars:The molars were significantly distal tipping after treatment with3.33°decreased in U6-SN.6.80°decreased in L6-MP (p<0.05):The average amount of distalization of maxillary first molar was3.82mm at the crown level and3.18mm at the root level coupled with1.05mm intrusion(p<0.05). Significant changes were observed in the distalization of mandibulaur first molar3.19mm at the crown level and2.57mm at the root level accompaned by0.0.71mm intrusion (p<0.05).4. Changes of hard tissues:The skeletal changes during treatment showed that the Frankfort horizontalmandibular plane angle (FMA) decreased by1.35°with statistical significance (p<0.05). ANS-Me decreased by0.29mm with statistical significance (p<0.05). The other measurements were not statistically different.5. Changes of Soft tissues:The mean distal repositionings of the upper and lower lips relative to the E-line were1.58and2.19mm. respectively. The lower lip moved distally more than the upper lip(p<0.01).6. Changes of dental arch width:There were significant differences in maxillary and mandibular widths before and after distalization. Significant differences were seen in terms of coronal arch width of canines, premolars and molars. The differences in expansion between the canine coronal arch width.premolar coronal arch width and molar coronal arch width of maxillary were increased by approximately1.21、2.34and1.41mm (P<0.05). respectively:The distance between the canine cusps, premolar cusps and the mesiobuccal cusps of mandibular increased by0.95.1.89. and0.87mm p<0.05), respestively.7. Changes of the tooth length:Significant changes were observed in the length of central incisors and lateral incisors, the mean amount of0.37and0.46mm decreased in the maxillary.with the average amount of0.29and0.31mm decreased in the mandibular. There was no clinical significance in root resorption. [Conclusions]1. With microimplant-aided sliding mechanics, all of cases were distalized successfully and achieve normal overjet and overbite, ClassI molar and canine relation was achieved bilaterally;2.The first molars achieve bodily movement with less distal tipping, incisors achieved tipping movement.3. Soft tissue profile improved significantly after orthodontic treatment with Micro-implant.4. Significant increased were seen in terms of dental arch width and arch length discrepancy was improved after treatment.5. No significant root resorption were achieved in incisors through significant dentition distal movement.