锥形束CT测量牙齿长度与牙体实际长度的比较

Comparison between the tooth length measured by cone-beam CT and the tooth length measuredwith vernier caliper

目的比较锥形束CT牙齿影像长度和牙体实际长度的差异，为151腔临床应用锥形束CT进行诊断和治疗提供参考。方法选取160颗因正畸拔除的单根或融合单根前磨牙，数显游标卡尺测量离体牙实际长度，采用随机数字表法分10次，每次16颗牙，排列于人颅骨标本上下颌磨牙区、前磨牙区、尖牙区和前牙区共8个分区，拍摄锥形束CT，测量锥形束CT冠状位、矢状位上牙齿的影像长度，并与牙齿实际长度进行比较。结果锥形束CT冠状位结果显示，除上下颌前磨牙区牙齿影像长度与实际长度差异无统计学意义（P〉0．05）外，其余6个分区牙齿影像长度均显著小于实际长度（P〈0．05）；矢状位结果显示，上下颌磨牙区、下颌前磨牙区、下颌尖牙区、下颌前牙区牙齿影像长度[分别为（20．41±1．71）、（18．78±2．67）、（18．90±1．99）、（20．30±1．50）、（20．01±1．98）mm]均显著小于实际长度[分别为（21．77±1．60）、（21．37-4-1．53）、（21．70±1．38）、（21．414-1．72）、（21．42±I．90）mm]（P〈0．05）。牙齿颊舌向转矩角与锥形束CT冠状位上的牙齿影像长度存在相关性（Spearman相关系数为7．00，P〈0．001）；牙齿近远中轴倾角与锥形束CT矢状位上的牙齿影像长度存在相关性（Spearman相关系数为0．624，P〈0．001）。结论应用锥形束cT测得的牙齿影像长度小于牙齿实际长度。牙齿轴倾角和转矩角可影响锥形束CT牙齿影像长度的准确性。

Objective To evaluate the accuracy of cone-bean CT （CBCT） on the measurement of the tooth length. Methods One hundred and sixty single root premolars extracted for orthodontic purposes were selected. The tooth length was measured with vernier caliper. The premolars were divided into 10 groups randomly, 16 premolars in each group. In each group, the teeth were lined in molar area, premolar area, canine area and anterior tooth area in maxilla and mandible. Then CBCT was taken, and the tooth length was measured using the software supplied by the manufacturer in coronal and sagittal plane. Accuracy was compared between vernier caliper measurement and CBCT measurement. Results The tooth length measured by CBCT was smaller than that measured with the vernier caliper. Significant differences were found in six areas, except the maxillary and mandibular premolar areas. With the increase of mesial-distal inclination or bueeolingua] torque angle, the difference between tooth length measured by CBCT and that measured with vernier caliper increased. The correlation between buecolingual torque angle（ LX1 ） and the coronal view of CBCT radiology tooth length （ Spearmen index was 7.00, P 〈 0. 001 ） , and the correlation between mesial- distal inclination and the coronal view of CBCT radiology tooth length （ Spearmen index was 0. 624, P 〈 0. 001 ） were found. Conclusions The tooth length measured by CBCT was smaller than that measured with vernier caliper.