The Study Of Soft And Hard Tissue Changes Before And After Orthodontic Treatment In Angle Classâ…  Bimaxillary Protrusion Adults

Objective:To investigate the soft and hard tissue profile changes in angle class l bimaxillary protrusion adults before and after orthodontic treatment,thus to provide theoretical basis for clinical diagnosis and treatment of these type of patients.Methods:The panoramic radiographs and lateral cephalometric films of completed and in accordance with the inclusion criteria bimaxillary adults from 2012 January to 2015 January in the First Affiliated Hospital of Zhengzhou University Department of Orthodontics,who used micro implant anchorage in the orthodontic treatment,were collected in the research,male 15 cases, female 17 cases, aged 18 to 35 years old.In a certain period of time, the lateral cephalometric X-ray radiographs before and after the treatment were measured two times, taking the average value.By making the comparison between bimaxillary protrusion group and the normal occlusion group,the changes before and after the orthodontic treatment in bimaxillary protrusion group,to find out the differences of the soft and hard tissue in these group.Then to provide the theoretical basis for clinical diagnosis and treatment of these type of patients.Results:Compared with normal adults,the measurements in Angle class I bimaxillary adults show that: the ANB angle, the line distance and angle between U1-NA, the angle between U1- SN plane, the line distance and angle between L1-NB, the angle of the L1-MP plane, MP- and SN plane are larger than normal measurements, with significant difference(P < 0.05). Soft tissue measurements show that nasolabial angle(NLA), the soft tissue facial angle(Ns-Sn-Pos) in bimaxillary protrusion patients were less than the normal, with statistically significant difference. The lip protrusion and H angle are larger than normal measurements(P < 0.05). There is no significant difference between chin thickness and normal occlusion.StudyⅡshow that:SNA, SNB angle, the length of mandibular and maxillary were decreased when compared with measurements before treatment, but the difference was not statistically significant.After the treatment,the angle of ANB, SN-MP, Y axis were increased, and it was significantly different.By contrast with the data before the treatment,after the retraction,the line distance and angle between the maxillary central incisor and NA, the angle between the maxillary central incisor and SN plane, the line distance and angle between the lower central incisor and NB,and the angle of the lower incisor with the mandibular plane were reduced significantly(P < 0.05).With the retraction of incisors, U1-L1 angle increases and anterior dental arch protrusion decreases quite obviously.When the treatment is finished,the distance of N-Me and ANS-Me was increased, but the difference was not statistically significant.After the treatment,the changes in soft tissue are as follows:the Nasolabial angle NLA, face angle Ns-Sn-Pos were increased, and the difference has statistical significance.The index that reflect the protrusion of the upper and lower lip,such as ULP、LLP、UL-Y axis、LL-Y axis、UL-E and LL-E were decreased, with significant differences.The H angle were sharply decreased(p<0.05).Chin thickness was reduced, the difference had no statistical significance.(P > 0.05).The upper lip thickness UL-UI and the thickness of lower lip LL-LI increased after treatment, with no significant difference.In the horizontal direction, the maxillary incisors margin point U1, apical margin point U1 R, the lower incisors margin point L1, the apical point L1 R were significantly moved to the inside after the treatment, with statistically different(P < 0.05).The point A and point B moved to the inside of the mobile after treatment, the difference was not statistically significant(P > 0.05).In the vertical direction, the cut edge points of U1, L1,B and L1 R to X axis distance increased, the apical point of U1 R and the point of A to the X axis distance decreased slightly(P > 0.05).Conclusion:Compared with normal adults,the upper and lower anterior dental arch and teeth in Angle class I bimaxillary adults tend to inclined labial obviously,the trend of skeletal Class II malocclusion and high angle is obvious.the relationship of lip and chin does not adjust, with the upper and lower lip protrusion, naso-labial angle small, soft tissue chin retraction sharply.By extraction treatment,bimaxillary protrusion patients can achieve significant improvement in soft and hard tissue profile. And the improvement in adult patients is mainly achieved by dental effects, the skeletal and soft tissue reconstruction is weak.Suitable nasolabial angle and good lip and chin morphology plays an important role in the facial aesthetics.Cortical bone is the limiting factor for the retraction of anterior teeth, remodeling of alveolar bone in patients with adult is slow.Implant anchorage is used for a variety of purposes, and provides a reliable and new therapeutic methods for orthodontic treatment.But we should avoid the potential risk during the treatment.In the treatment,attention should be attached to the vertical control, thus to prevent the mandible down back clockwise rotation.