Abstract：
BACKGROUND: Patients undergoing orthodontic treatment (OT) face an increased risk of developing external apical root resorption (EARR). A prognostic risk assessment prior to OT can potentially be conducted through anatomical features in panoramic radiography. This retrospective study aimed to assess the significance of Kjær\'s morphological characteristics in analyzing the risk of EARR.
METHODS: Panoramic radiographs of 1,156 patients (624 females, 532 males) were retrospectively analyzed. Anamnestic and treatment-related data were extracted from patient records. The mean age at the start of OT was 12.8 ± 2.2 years (min. 6.4 years, max. 22.3 years) and at the end of OT 15.9 years (min. 8.5 years, max. 24.1 years). The mean treatment duration was 3.1 ± 1.6 years. Panoramic radiographs with a minimum of two per patient were examined for the presence of Kjær\'s characteristics. The degree of EARR was registered defining resorption in four degrees of severity. Bivariate analysis and multivariate Poisson regression were performed to assess the association between Kjær\'s characteristics and EARR patient- and tooth- related (α = 0.05).
RESULTS: In total, 72.8% of the patients showed EARR at the end of OT with lateral maxillary incisors most frequently affected. Short roots (p < 0.001) were significantly associated with EARR in patients. Tooth-related microdontia (#12, #22, lower second premolars), narrow crowns (#11, #21, lower incisors), short roots (upper incisors, lower first molars) and ectopia (#11, #21, #13), such as shorter distal roots of the mandibular first molar showed a significant association with EARR depending on severity degree. The type of orthodontic appliance (fixed: p < 0.001, fixed and removeable: p = 0.008), as well as treatment duration (p < 0.001) were also identified as risk factors for EARR.
CONCLUSIONS: Although the risk assessment for EARR development through panoramic radiography analysis is limited, predisposition appears to be present in specific dental characteristics and treatment-related factors.
METHODS: Panoramic radiographs of 1,156 patients (624 females, 532 males) were retrospectively analyzed. Anamnestic and treatment-related data were extracted from patient records. The mean age at the start of OT was 12.8 ± 2.2 years (min. 6.4 years, max. 22.3 years) and at the end of OT 15.9 years (min. 8.5 years, max. 24.1 years). The mean treatment duration was 3.1 ± 1.6 years. Panoramic radiographs with a minimum of two per patient were examined for the presence of Kjær\'s characteristics. The degree of EARR was registered defining resorption in four degrees of severity. Bivariate analysis and multivariate Poisson regression were performed to assess the association between Kjær\'s characteristics and EARR patient- and tooth- related (α = 0.05).
RESULTS: In total, 72.8% of the patients showed EARR at the end of OT with lateral maxillary incisors most frequently affected. Short roots (p < 0.001) were significantly associated with EARR in patients. Tooth-related microdontia (#12, #22, lower second premolars), narrow crowns (#11, #21, lower incisors), short roots (upper incisors, lower first molars) and ectopia (#11, #21, #13), such as shorter distal roots of the mandibular first molar showed a significant association with EARR depending on severity degree. The type of orthodontic appliance (fixed: p < 0.001, fixed and removeable: p = 0.008), as well as treatment duration (p < 0.001) were also identified as risk factors for EARR.
CONCLUSIONS: Although the risk assessment for EARR development through panoramic radiography analysis is limited, predisposition appears to be present in specific dental characteristics and treatment-related factors.
摘要：
背景：接受正畸治疗（OT）的患者面临发生外根尖吸收（EARR）的风险增加。OT之前的预后风险评估可能会通过全景射线照相术中的解剖特征进行。这项回顾性研究旨在评估Kjär的形态特征在分析EARR风险中的意义。
方法：1,156名患者（624名女性，532名男性)进行了回顾性分析。从患者记录中提取记忆和治疗相关数据。OT开始时的平均年龄为12.8±2.2岁（min。6.4年,max.22.3年）和OT15.9年（最小。8.5年,max.24.1年）。平均治疗时间为3.1±1.6年。检查每位患者至少两张的全景X光片，以检查是否存在Kjär\的特征。记录了EARR的程度，定义了四个严重程度的吸收。进行了双变量分析和多变量泊松回归来评估Kjär的特征与EARR患者和牙齿相关之间的关联（α=0.05）。
结果：总计，72.8％的患者在OT结束时显示EARR，上颌侧切牙最常受到影响。短根(p<0.001)与患者的EARR显著相关。与牙齿相关的牙体（＃12，＃22，下第二磨牙），狭窄的牙冠（＃11，＃21，下切牙），短根（上切牙，下第一磨牙)和外翻(#11、#21、#13)，例如下颌第一磨牙的较短远端根与EARR显着相关，具体取决于严重程度。正畸矫治器的类型（固定：p<0.001，固定和可移除：p=0.008），以及治疗持续时间(p<0.001)也被确定为EARR的危险因素。
结论：尽管通过全景射线照相分析对EARR发展的风险评估有限，易感性似乎存在于特定的牙齿特征和治疗相关因素中。
方法：1,156名患者（624名女性，532名男性)进行了回顾性分析。从患者记录中提取记忆和治疗相关数据。OT开始时的平均年龄为12.8±2.2岁（min。6.4年,max.22.3年）和OT15.9年（最小。8.5年,max.24.1年）。平均治疗时间为3.1±1.6年。检查每位患者至少两张的全景X光片，以检查是否存在Kjär\的特征。记录了EARR的程度，定义了四个严重程度的吸收。进行了双变量分析和多变量泊松回归来评估Kjär的特征与EARR患者和牙齿相关之间的关联（α=0.05）。
结果：总计，72.8％的患者在OT结束时显示EARR，上颌侧切牙最常受到影响。短根(p<0.001)与患者的EARR显著相关。与牙齿相关的牙体（＃12，＃22，下第二磨牙），狭窄的牙冠（＃11，＃21，下切牙），短根（上切牙，下第一磨牙)和外翻(#11、#21、#13)，例如下颌第一磨牙的较短远端根与EARR显着相关，具体取决于严重程度。正畸矫治器的类型（固定：p<0.001，固定和可移除：p=0.008），以及治疗持续时间(p<0.001)也被确定为EARR的危险因素。
结论：尽管通过全景射线照相分析对EARR发展的风险评估有限，易感性似乎存在于特定的牙齿特征和治疗相关因素中。
