Walker Mhairi
University of Aberdeen Dental School & Hospital, Aberdeen, Scotland.
Evid Based Dent. 2013 Sep;14(3):81-2. doi: 10.1038/sj.ebd.6400951.
Three arm, parallel group, patient randomised trial.
Seventy-five patients who had just completed a course of treatment with four premolar extractions and fixed straight wire appliances in both jaws (0.022 inch, MBT) having had no previous orthodontics, were randomised by participant ballot sampling. To be eligible they had to be in the permanent dentition, with space deficiencies in both jaws, normal skeletal and dentoalveolar sagittal, vertical and transverse relationships, Class I molars or 3mm anterior or posterior deviation. The three retention methods were: 1) removable vacuum-formed retainer with maxillary canine-to-canine and palatal coverage plus a mandibular canine-to-canine bonded retainer (GroupV-CTC); 2) an identical maxillary vacuum-formed retainer as in Group V-CTC plus stripping of mandibular anterior teeth (Group V-S); and 3) a prefabricated positioner covering all erupted teeth in both jaws (Group P). Patients were given appliances within one hour of debonding, which were worn more for the first than second year then discontinued.
Dental casts were taken at four time points; before treatment, on removal of fixed appliances, after 12 months and 24 months of retention. Twenty randomly selected casts were measured by a single blinded assessor on two separate occasions, four weeks apart, using electronic digital callipers for inter-canine width; inter-molar width; arch length; overjet; and overbite. Height and estimated compliance was recorded at every visit. Successful retention using Little's Irregularity Index was considered to be <3.5mm.
Seventy-five patients were enrolled, and 69 completed, the trial. The mean active treatment time was 1.7 years and mean age was 14.4 years (SD 1.5) at start of retention. Although there were statistically significant differences for some of the parameters measured, there were no clinically significant differences between the three retention methods. All three were equally effective in retaining orthodontic treatment results and controlling relapse to a clinically significant level even when the results were adjusted for cooperation, initial crowding, growth and gender. The major part of relapse took place during the first year of retention.
All three retention methods, V-CTC, V-S and P, retained the orthodontic treatment results and prevented relapse within clinically acceptable levels. Most relapse took place within the first year of retention and changes during the second year were small or negligible.
三臂平行组患者随机试验。
75例刚刚完成双侧拔除四颗前磨牙并使用上下颌固定直丝矫治器（0.022英寸，MBT）进行治疗疗程、此前未接受过正畸治疗的患者，通过参与者抽签抽样进行随机分组。入选患者必须处于恒牙列期，上下颌均存在间隙不足，骨骼及牙-牙槽矢状、垂直和横向关系正常，磨牙为I类关系或前后向偏差3mm。三种保持方法分别为：1）上颌从尖牙到尖牙及腭部覆盖的可摘真空成型保持器加下颌从尖牙到尖牙的粘结保持器（V-CTC组）；2）与V-CTC组相同的上颌真空成型保持器加下颌前牙去釉（V-S组）；3）覆盖上下颌所有已萌出牙齿的预制定位器（P组）。患者在拆除矫治器后1小时内佩戴矫治器，第一年佩戴时间多于第二年，然后停止佩戴。
在四个时间点制取牙模；治疗前、拆除固定矫治器时、保持12个月和24个月后。由一名单盲评估者在两个不同时间、间隔四周，使用电子数字卡尺对随机选取的20个牙模测量尖牙间宽度、磨牙间宽度、牙弓长度、覆盖和覆合。每次复诊记录身高和估计的依从性。使用Little不规则指数，保持成功被定义为<3.5mm。
75例患者入组，69例完成试验。保持开始时的平均积极治疗时间为1.7年，平均年龄为14.4岁（标准差1.5）。尽管所测量的一些参数存在统计学显著差异，但三种保持方法之间无临床显著差异。即使对合作程度、初始拥挤度、生长情况和性别进行调整后，三种方法在保持正畸治疗效果和将复发控制在临床显著水平方面同样有效。复发的主要部分发生在保持的第一年。
V-CTC、V-S和P这三种保持方法均能保持正畸治疗效果，并将复发预防在临床可接受水平内。大多数复发发生在保持的第一年，第二年的变化较小或可忽略不计。
