Bishara S E, Cummins D M, Zaher A R
Department of Orthodontics, University of Iowa College of Dentistry, Iowa City 52242-1001, USA.
Am J Orthod Dentofacial Orthop. 1997 Jan;111(1):18-27. doi: 10.1016/s0889-5406(97)70297-x.
The purpose of this study was to evaluate the treatment and posttreatment changes in the facial and dental parameters in two groups of patients with Class II, Division 1 malocclusions. In one group (n = 46), the patients were treated with a nonextraction approach, whereas in the second group (n = 45), the treatment included the extraction of four first premolars. The treatment groups were compared with matched untreated normals (n = 35) from the Iowa Growth Study. Lateral cephalograms and dental casts were evaluated at three stages: pretreatment, posttreatment, and approximately 2 years after treatment. Student's t tests were used to compare the extraction and nonextraction groups. Significance was predetermined at p < or = 0.05. The cephalometric findings indicate that before treatment, the subjects treated with four first premolar extractions had more protrusive upper and lower lips and a larger tooth size-arch length discrepancy. After treatment the upper and lower lips were more retrusive in the extraction groups, and more protrusive in the nonextraction groups. The extraction groups tended to have straighter faces and slightly more upright maxillary and mandibular incisors, whereas the nonextraction groups had the opposite tendencies. The average soft tissue and skeletal measurements for both groups were close to, but on opposite sides of, the corresponding averages derived from the Iowa normative standards. The findings from the dental arch measurements indicate that after treatment both the extraction and nonextraction groups experienced an increase in tooth size-arch length discrepancy and a reduction in arch length. In general, extractions did not significantly alter the direction of the overall posttreatment trends. Furthermore, the trends in the posttreatment changes were similar in male and female patients, as well as in the maxillary and mandibular arches. The current findings suggest that the extraction/nonextraction decision, if based on sound diagnostic criteria, does not have a systematic detrimental effect on the facial profile. But clinicians should be aware of the trends introduced by the two treatment modalities to avoid accentuating undesirable profile characteristics.
本研究的目的是评估两组安氏II类1分类错牙合患者治疗前后面部和牙齿参数的变化。一组（n = 46）患者采用非拔牙矫治方法，而另一组（n = 45）的治疗包括拔除四颗第一前磨牙。将治疗组与来自爱荷华生长研究的匹配未治疗正常人群（n = 35）进行比较。在三个阶段评估头颅侧位片和牙模：治疗前、治疗后以及治疗后约2年。采用学生t检验比较拔牙组和非拔牙组。显著性预先设定为p≤0.05。头影测量结果表明，治疗前，拔除四颗第一前磨牙治疗的受试者上下唇更突出，牙齿大小与牙弓长度差异更大。治疗后，拔牙组的上下唇更后缩，非拔牙组的上下唇更前突。拔牙组面部趋于更直，上颌和下颌切牙稍更直立，而非拔牙组则有相反的趋势。两组的平均软组织和骨骼测量值接近爱荷华标准相应平均值，但位于其两侧。牙弓测量结果表明，治疗后拔牙组和非拔牙组的牙齿大小与牙弓长度差异均增加，牙弓长度均减小。总体而言，拔牙并未显著改变治疗后总体趋势的方向。此外，治疗后变化趋势在男性和女性患者以及上颌和下颌牙弓中相似。目前的研究结果表明，如果基于合理的诊断标准，拔牙/不拔牙决策对面部轮廓没有系统性的有害影响。但临床医生应了解两种治疗方式所带来的趋势，以避免加重不良的轮廓特征。
