| Objective:The purpose of the experiment was to analyze the related factors of labial gingival recessions of lower anterior teeth after treatment in fixed orthodontic adolescent, including the position of lower anterior teeth, alveolar thickness, symphysis morphology and other factors, so as to provide the theoretical basis for preventing the labial gingival recessions of lower anterior teeth in orthodontic adolescent.Methods:The patients were divided into the extraction group and non-extraction group according to the orthodontic methods. According to the inclusion criteria,30 cases of adolescents with labial gingival recessions of lower anterior teeth after orthodontic treatment were selected into the experimental group, and 30 cases of adolescents with labial gingival non-recessions of lower anterior teeth after orthodontic treatment were selected as the control group. The related factors were compared. The proportions of men and women in two groups were kept consistent. The patients underwent the lateral cephalometric radiographs and intraoral photography before and after treatment. The dental model and lateral cephalometric radiographs were measured using the electronic vernier caliper.The two digits after the decimal point were retained. The measuring results were analyzed using SPSS 19.0 software.Conclusions:1、Among the related projects reflecting the position and change of lower anterior teeth before and after orthodontic treatment, the mandibular extraction orthodontic group showed the movement types of lower anterior teeth were significantly different between the non-recession group and recession group (P＜0.01). The lower anterior teeth moved towards labial-mesial direction in the recession group and moved towards lingal-distal direction in the non-recession group; The positions of lower anterior teeth were also different between the two groups after orthodontic treatment (P＜0.05). The labial inclination of mandibular anterior teeth was larger than that of non-recession group, suggesting that the position and movement type of lower anterior teeth were related to the labial gingival recessions. The related projects in the mandibular non-extraction group showed no statistical difference between the recession group and non-recession group (P>0.05).2、Among the relate projects reflecting alveolar thickness and change before and after orthodontic treatment group, both in mandibular extraction orthodontic group and non-extraction orthodontic group, the alveolar thicknesses were thinner in the recession group and non-recession group after orthodontic treatment than those of before orthodontic treatment (P<0.05). Moreover, the alveolar thickness of recession group after orthodontic treatment was thinner than that of non-recession group and the difference was statistically significant (P<0.05).The results showed that the alveolar thickness was related to labial gingival recessions of lower anterior teeth before and after orthodontic treatment. The thinner the alveolar thickness, the more easily the gingival recession.3、Among the projects reflecting the symphysis morphology and change before and after orthodontic treatment, both in mandibular extraction orthodontic group and non-extraction orthodontic group, the ratios of symphysis height and depth were increased in the recession group and non-recession group after orthodontic treatment. Among them, the change in the recession group was greater than that of non-recession group (P＜0.05). The results showed that the symphysis morphology tended to be was long-narrow shaped in the recession group. The ratio change in the maindibular non-extraction orthodontic treatment group was mainly caused by significantly increased symphysis height, and the change in the recession group was significantly greater than that of non-recession group (P<0.01); The ratio change in the mandibular extraction orthodontic treatment group was mainly because the symphysis depth became thin,and the decrease of symphysis thickness was significantly larger than that of non-recession group (P＜0.01). The result showed that the symphysis morphology in the recession group tended to be long-narrow shaped, but the symphysis morphological change of the non-recession group was not significant. The patients with long-narrow shaped symphysis easily occurred to gingival recessions.4、The variables with statistical difference in the recession group and non-recession group were included into single-factor logistic regression model, and the standardized coefficients whether these variables occurred to gingival recession were calculated. The results showed that the effect of the position of lower anterior teeth on labial gingival recession was most significant in the mandibular extraction orthodontic treatment group (P＜0.01); While the effect of the symphysis morphology change on labial gingival recession was most significant in the mandibular non-extraction orthodontic treatment group (P<0.01).5、The chi square tests of gingival biotype, lower anterior teeth movement type and labio-lingual inclination of lower anterior teeth were conducted. The results showed that the gingival biotype, movement type and labio-lingual inclination of lower anterior teeth were related to labial gingival recession (P<0.05). Of which, labial gingival recession of lower anterior teeth easily occurred in the patients with thin gingival biotype, labial movement of lower anterior teeth and labio-lingual inclination>95 °.Conclusions:1. The labial gingival recessions were caused by the combined action of many factors in adolescents with fixed orthodontic treatment after orthodontic treatment; 2. Regardless of mandibular extraction treatment or non-extraction treatment, the labial gingival recession was related to symphysis morphology and alveolar thickness. The anterior alveolar was thinner, the patients with long-narrow symphysis were more easily occur to the labial gingival recessions.3. The labial gingival recessions was significantly related to lower anterior teeth movement type and degree after mandibular extraction treatment. The labial movement of lower anterior teeth more easily occurred to gingival recessions. However, the gingival recessions was not related to the movement of lower anterior teeth in mandibular non-extraction teeth orthodontic treatment patients, but was more related to the symphysis morphology change. The patients with thin gingival biotype more easily occurred to gingival recessions. The labial gingival recession of lower anterior teeth easily occurred in the patients with thin gingival biotype, labial movement of lower anterior teeth and labio-lingual inclination>95°. |
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