Sunku Raghavendra, Roopesh R, Kancherla Pavan, Perumalla Kiran Kumar, Yudhistar Palla Venkata, Reddy V Sridhar
Department of Orthodontics and Dentofacial Orthodpedics, Dental College and Hospital, Sangareddy, Andhra Pradesh, India.
J Contemp Dent Pract. 2011 Nov 1;12(6):422-8. doi: 10.5005/jp-journals-10024-1070.
The objective of this study was to evaluate density changes around the apices of teeth during orthodontic treatment by using digital subtraction radiography to measure the densities around six teeth (maxilla central incisors, lateral incisors, and canines) before and after orthodontic treatment in 36 patients and also assess treatment variables and their coorelation with root resorption.
A total of 36 consecutive patient files were selected initially. The selected patients presented with a class I or II relationship and were treated with or without premolar extractions and fixed appliances. Some class II patients were treated additionally with extraoral forces or functional appliances. External apical root resorption (EARR) per tooth in millimeters was calculated and was also expressed as a percentage of the original root length. Image reconstruction and subtraction were performed using the software Regeemy Image Registration and Mosaicing (version 0.2.43-RCB, DPI-INPE, Sao Jose dos Campos, Sao Paulo, Brazil) by a single operator. A region of interest (ROI) was defined in the apical third of the root and density calibration was made in Image J® using enamel (gray value = 255) as reference in the same image. The mean gray values in the ROIs were reflective of the change in the density values between the two images.
The root resorption of the tooth and the factors of malocclusion were analyzed with a one-way ANOVA. An independent t-test was performed to compare the mean amount of resorption between male and female, between extraction and nonextraction cases. The density changes after orthodontic treatment were analyzed using the Wilcoxon signedrank test. In addition, the density changes in different teeth were analyzed using the Kruskal-Wallis test. The cut-off for statistical significance was a p-value of 0.05. All the statistical analyses were carried out using SPSS (version 13.0 for Windows, Chicago, IL, USA).
Gender, the age at which treatment was started and Angle's classification was not statistically related with observed root resorption. The mean percentage density reduction as assessed by DSR was greatest in both central incisor: by 27.2 and 25.2% in the upper-right and upper-left central incisors, respectively, followed by the upper-right and upper-left canine teeth (23.5 and 21.0%) and then the upper-right and upper-left lateral incisors (19.1 and 17.4%).
Tooth extraction prior to treatment initiation and the duration of orthodontic treatment was positively correlated with the amount of root resorption. DSR is useful for evaluating density changes around teeth during orthodontic treatment. The density around the apices of teeth reduced significantly after the application of orthodontic forces during treatment.
Assessment of density changes on treatment radiographs of patients undergoing orthodontic therapy may help in the monitoring of external apical root resorption during course of treatment.
本研究的目的是通过数字减影放射摄影术评估36例患者正畸治疗前后六颗牙齿（上颌中切牙、侧切牙和尖牙）根尖周围的密度变化，并评估治疗变量及其与牙根吸收的相关性。
最初共选择了36例连续患者的病历。所选患者呈现I类或II类关系，接受或未接受拔除前磨牙及固定矫治器治疗。部分II类患者还接受了口外力或功能矫治器治疗。计算每颗牙齿的根尖外吸收（EARR），以毫米为单位，并表示为原始牙根长度的百分比。由一名操作人员使用Regeemy图像配准和拼接软件（版本0.2.43-RCB，DPI-INPE，巴西圣保罗坎皮纳斯市圣若泽杜斯坎普斯）进行图像重建和减法运算。在牙根根尖三分之一处定义感兴趣区域（ROI），并在Image J®中以同一图像中的牙釉质（灰度值=255）为参考进行密度校准。ROI中的平均灰度值反映了两张图像之间密度值的变化。
采用单因素方差分析对牙齿的牙根吸收情况和错牙合因素进行分析。采用独立t检验比较男性和女性、拔牙病例和非拔牙病例之间的平均吸收量。使用Wilcoxon符号秩检验分析正畸治疗后的密度变化。此外，使用Kruskal-Wallis检验分析不同牙齿的密度变化。统计学显著性的临界值为p值0.05。所有统计分析均使用SPSS（美国伊利诺伊州芝加哥市Windows版13.0）进行。
性别、开始治疗的年龄和安氏分类与观察到的牙根吸收无统计学相关性。通过数字减影放射摄影术评估的平均密度降低百分比在两颗中切牙中最大：右上和左上中切牙分别为27.2%和25.2%，其次是右上和左上尖牙（23.5%和21.0%），然后是右上和左上侧切牙（19.1%和17.4%）。
治疗开始前拔牙及正畸治疗持续时间与牙根吸收量呈正相关。数字减影放射摄影术有助于评估正畸治疗期间牙齿周围的密度变化。正畸治疗过程中施加正畸力后，牙齿根尖周围的密度显著降低。
评估正畸治疗患者治疗X线片上的密度变化可能有助于在治疗过程中监测根尖外吸收情况。
