Division of Orthodontics, Faculty of Dentistry, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
Division of Orthodontics, Faculty of Dentistry, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
Am J Orthod Dentofacial Orthop. 2021 Jan;159(1):e7-e16. doi: 10.1016/j.ajodo.2020.08.007. Epub 2020 Nov 21.
To evaluate the influence of compensatory tipping of maxillary and mandibular incisors on the anterior arch length ratio and canine relationship in skeletal Class II malocclusion.
The study was based on posttreatment lateral head films and dental casts of 88 patients. The sample was divided into a Class II malocclusion group (32 patients; ANB ≥5° and mean [± standard deviation] age, 20.82 ± 7.67 years) and a Class I malocclusion group (56 patients; 1° ≤ ANB ≤ 2.5° and mean [± standard deviation] age, 19.20 ± 5.04 years). Measurements obtained for anterior arch length and width, Bolton discrepancy, canine relationship, growth pattern, and incisor position were compared between the groups. The canine relationship was correlated with dental and skeletal variables (P <0.05).
The mean ANB angles were 6.21° and 1.78° for the Class II and Class I malocclusion groups, respectively. The skeletal Class II group presented significantly larger mandibular anterior arch length, producing an unbalanced anterior arch length ratio. The canine relationship was more displaced toward Class II in this group. Anterior arch length ratio was the most influential variable in the canine relationship. The mandibular incisors had a higher compensation degree than the maxillary incisors. The groups were similar regarding overjet, overbite, and growth pattern.
Class II malocclusion camouflage treatment with excessive proclination of the mandibular incisors was associated with an increase in mandibular arch length, negatively influencing the anterior arch length ratio and the final canine relationship. Mandibular anterior arch length reduction by interproximal stripping may be necessary in moderate to severe skeletal Class II malocclusion orthodontic treatment.
评估上颌和下颌切牙代偿性倾斜对上颌牙弓长度比率和安氏Ⅱ类错（牙合）的尖牙关系的影响。
本研究基于 88 名患者的治疗后侧头颅侧位片和牙模。样本分为安氏Ⅱ类错（牙合）组（32 例；ANB≥5°，平均[±标准差]年龄为 20.82±7.67 岁）和安氏Ⅰ类错（牙合）组（56 例；1°≤ANB≤2.5°，平均[±标准差]年龄为 19.20±5.04 岁）。比较两组前牙弓长度和宽度、Bolton 不调、尖牙关系、生长模式和切牙位置。犬牙关系与牙性和骨性变量相关（P＜0.05）。
安氏Ⅱ类错（牙合）组和安氏Ⅰ类错（牙合）组的平均 ANB 角分别为 6.21°和 1.78°。骨性安氏Ⅱ类错（牙合）组下颌前牙弓长度明显增大，导致前牙弓长度比例失衡。该组的尖牙关系更偏向安氏Ⅱ类。前牙弓长度比率是影响尖牙关系的最主要变量。下颌切牙的补偿程度高于上颌切牙。两组在覆（牙合）、覆盖和生长模式方面相似。
下颌切牙过度倾斜的安氏Ⅱ类错（牙合）掩饰性治疗会导致下颌牙弓长度增加，对上颌牙弓长度比率和最终尖牙关系产生负面影响。在中度至重度骨性安氏Ⅱ类错（牙合）的正畸治疗中，可能需要通过邻面去釉来减少下颌前牙弓长度。
