Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing, China.
Am J Orthod Dentofacial Orthop. 2010 Nov;138(5):544.e1-9; discussion 544-5. doi: 10.1016/j.ajodo.2009.12.027.
The objective of this pilot randomized clinical trial was to investigate the relative effectiveness of anchorage conservation of en-masse and 2-step retraction techniques during maximum anchorage treatment in patients with Angle Class I and Class II malocclusions.
Sixty-four growing subjects (25 boys, 39 girls; 10.2-15.9 years old) who required maximum anchorage were randomized to 2 treatment techniques: en-masse retraction (n = 32) and 2-step retraction (n = 32); the groups were stratified by sex and starting age. Each patient was treated by a full-time clinic instructor experienced in the use of both retraction techniques at the orthodontic clinic of Peking University School of Stomatology in China. All patients used headgear, and most had transpalatal appliances. Lateral cephalograms taken before treatment and at the end of treatment were used to evaluate treatment-associated changes. Differences in maxillary molar mesial displacement and maxillary incisor retraction were measured with the before and after treatment tracings superimposed on the anatomic best fit of the palatal structures. Differences in mesial displacement of the maxillary first molar were compared between the 2 treatment techniques, between sexes, and between different starting-age groups.
Average mesial displacement of the maxillary first molar was slightly less in the en-masse group than in the 2-step group (mean, -0.36 mm; 95% CI, -1.42 to 0.71 mm). The average mesial displacement of the maxillary first molar for both treatment groups pooled (n = 63, because 1 patient was lost to follow-up) was 4.3 ± 2.1 mm (mean ± standard deviation). Boys had significantly more mesial displacement than girls (mean difference, 1.3 mm; P <0.03). Younger adolescents had significantly more mesial displacement than older adolescents (mean difference, 1.3 mm; P <0.02).
Average mesial displacement of the maxillary first molar with 2-step retraction was slightly greater than that for en-masse retraction, but the difference did not reach statistical significance. This finding appears to contradict the belief of many clinicians that 2-step canine retraction is more effective than en-masse retraction in preventing clinically meaningful anchorage loss.
本研究旨在通过随机临床试验比较安氏Ⅰ类和Ⅱ类错（牙合）患者在使用最大支抗治疗时，整体内收和两步内收技术对支抗保持的相对效果。
64 名生长发育期患者（男 25 名，女 39 名；年龄 10.2-15.9 岁）需要最大支抗，随机分为两组：整体内收组（n=32）和两步内收组（n=32）；根据起始年龄和性别分层。所有患者均由北京大学口腔医学院正畸科经验丰富的正畸医生使用两种内收技术进行治疗。所有患者均使用头帽，大多数患者使用腭刺。在治疗前和治疗结束时拍摄侧位头颅定位片，评估治疗相关变化。在解剖腭部结构最佳拟合的基础上，叠加治疗前后描记线，测量上颌磨牙近中移动和上颌切牙内收的差异。比较两种治疗技术、性别和不同起始年龄组之间上颌第一磨牙近中移动的差异。
整体内收组上颌第一磨牙的平均近中移动量略小于两步内收组（平均差值为-0.36mm；95%置信区间为-1.42 至 0.71mm）。将两组患者（因为 1 例失访，n=63）的上颌第一磨牙近中移动量合并后，平均移动量为 4.3±2.1mm（均值±标准差）。男孩的近中移动量明显大于女孩（平均差值为 1.3mm；P<0.03）。青少年早期患者的近中移动量明显大于青少年晚期患者（平均差值为 1.3mm；P<0.02）。
两步内收的上颌第一磨牙平均近中移动量略大于整体内收，但差异无统计学意义。这一发现似乎与许多临床医生的观点相矛盾，他们认为两步法尖牙内收比整体内收更能有效预防临床上有意义的支抗丧失。
