| [Objectives] To investigate the prevalence and distribution of the patients with short root anomaly(SRA) in permanent dentition for large sample, summarize the disease characteristics, and make up for the deficiencies of researches about this disease in China.To study the changes of root-crown ratio(R/C) after orthodontic treatment on the maxillary central incisors with SRA, To investigate whether SRA is a risk factor of orthodontically induced root resorption. To provide some reference and guidance for orthodontic clinical diagnosis and treatment of SRA patients.[Methods] Part one:2,855 cases of permanent dentition as the research objects were selected from January 2011 to December 2011 in Orthodontic Department of the Affiliated Stomatology Hospital of Kunming Medical University. The patients with SRA were diagnosed by Panoramic Radiographs and lateral cephalograms with the ApaJalahti’s standard. To analyse the R/C of SRA, prevalence rate, gender, affected teeth, teeth developmental abnormalities, skeletal pattern and anterior occlusion relationship. Part two:According to the inclusion criteria,34 cases who have SRA in the maxillary central incisors were selected in Orthodontic Department of the Affiliated Stomatology Hospital of Kunming Medical University, these cases had completed between 2008 and 2012. According to the matching condition,34 cases with normal maxillary central incisors were selected. Cases who have SRA in the maxillary central incisors were used as the experimental group, the maxillary central incisors in normal patients and the maxillary lateral incisors in SRA patients were used as the control group. To measure the R/C in each group before and after treatment according to the improved Lind’s method. To calculate the relative root-crown ratio (rRCR) and the relative root resorption(rRR) through the Fritz’s method. To analysis the situation of root resorption in each group after treatment. According to The grouping, compared the difference of the incidence of root resorption and rRR between groups.[Results] 1. In this study, the prevalence of SRA was 2.8%. the ratio of male to female was 1:2.3, and there was no difference in gender. The average R/C of SRA was 0.84±0.88, which mainly involving the maxillary central incisors and the second premolars, accompanied by ectopic eruption. SRA is more common in patients with Class Ⅲ skeletal pattern, the occlusion relationship of anteriors was mainly crossbite. 2. (1) In this study, each patient had one maxillary central incisors with root resorption at least, SRA group was more bilateral simultaneous involvement. Whether extraction or not, the incidence of root resorption was similar in the SRA group (87%) and in the control group (73%). There was no difference in the incidence of root resorption between SRA group and control group.(2) In this study, the rRR of 2 maxillary central incisors were more than 1/3 in the SRA group which occured severe root resorption. The rRR of the other groups were lower than 15%. The rRR of SRA group was greater than 5%, the rRR of control group were mainly concentrated in 0-5%, and the overall degree of root resorption was not large.(3) The rRR of SRA group was significantly higher than control group after orthodontic treatment, especially in the extraction group.(Conclusions] 1.In this study, the prevalence of SRA was 2.8%, there was no difference in gender.The average R/C of SRA was 0.84±0.88, which mainly involving the maxillary central incisors and the second premolars. There is a certain correlation between Ectopic eruption, Class Ⅲ skeletal pattern and anteriors crossbite with SRA. It is necessary to evaluate the R/C and the root morphology of these patients before orthodontic treatment.2. There was no difference in the incidence of root resorption between SRA group and control group after orthodontic treatments, but the degree of root resorption in SRA group was more serious, especially in the patients with tooth extraction. So SRA is a risk factor for orthodontically induced root resorption in the maxillary central incisors. However, in addition to individual patients, the overall degree of root resorption was not large, SRA is not the absolute contraindication of orthodontic treatment.3. For the orthodontic treatment of the patients with SRA, we need to be careful and cautious, make a reasonable plan, and shoot X-ray regularly. When serious root resorption occurs, we should reassess the treatment plan and make appropriate adjustments. |
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