Anchorage effectiveness of orthodontic miniscrews compared to headgear and transpalatal arches: a systematic review and meta-analysis

<b>Background:</b> Anchorage in orthodontics can be provided through several extra- and intra-oral sources including headgear, teeth, cortical bone and soft tissue. <b>Objective:</b> The aim of this review was to systematically review the effectiveness of miniscrews in reinforcing anchorage during en-masse retraction of anterior teeth in comparison to conventional anchorage appliances. <b>Search method:</b> Comprehensive searching of the electronic databases was undertaken up to March 2018 in the Cochrane Database of Systematic review, Cochrane Central Register of Controlled Trials, MEDLINE via PubMed and Scopus databases. Additional searching for on-going and unpublished data and hand search of relevant journals were also undertaken, authors were contacted, and reference lists screened. <b>Eligibility criteria:</b> Searches were restricted to randomized clinical trials (RCTs) published in English, which compared anchorage reinforcement using mechanically-retained miniscrews (diameter of 2 mm or less) to conventional anchorage appliances during en-masse retraction of anterior teeth in participants of any age treated with fixed appliances combined with extraction of maxillary premolars. <b>Data collection and analysis:</b> Blind and induplicate study selection, data extraction and risk of bias assessment were undertaken. The primary outcome was the amount of mesial movement of the upper first permanent molar (anchorage loss) while secondary outcomes included treatment duration, number of visits, adverse effects and patient-centered outcomes. The risk of bias was assessed using Cochrane risk of bias tool. A random-effects model with its corresponding 95% confidence interval (CI) were generated for comparable outcomes. Statistical heterogeneity across the studies were assessed using the <i>I</i>² and Chi² test. Additional sensitivity tests were implemented. <b>Results:</b> Seven RCTs met the inclusion criteria, however, data of 241 participants from 6 RCTs (250 miniscrews and 134 conventional anchorage appliances) were meta-analyzed. Qualities of the included RCTs varied from low to high. The standardized mean difference (SMD) of the anchrage loss between the two intervention groups was 2.07 mm ((95% CI (–3.05) to (–1.08), <i>p</i> I² = 88%, 6 RCTs)) in favour of miniscrews, which was also preserved after excluding the high risk of bias studies (SMD 1.94 mm, 95% CI (–2.46) to (–0.42) <i>p</i> I² = 93%, 3 RCTs)). Information on overall treatment duration, space closure duration, quality of treatment, patient-reported outcomes, adverse effects and number of visit were limited. <b>Conclusion:</b> The result of the meta-analysis suggested that there is moderate quality of evidence that miniscrews are clinically and statistically more effective in preserving orthodontic anchorage than conventional appliances. However, this conclusion is supported by a small number of studies with variable qualities. High-quality RCTs would give a better understanding of miniscrews effectiveness in providing orthodontic anchorage.

<b>背景：</b>正畸矫治中的支抗可通过多种口外及口内途径获取，包括头帽、牙齿、皮质骨以及软组织。<b>目的：</b>本系统综述旨在系统评价正畸微螺钉（miniscrews）在前牙整体内收过程中强化支抗的效果，并与传统支抗装置进行对比。<b>检索方法：</b>截至2018年3月，对以下电子数据库开展全面检索：Cochrane系统评价数据库（Cochrane Database of Systematic Reviews）、Cochrane对照试验中心注册库（Cochrane Central Register of Controlled Trials）、PubMed收录的MEDLINE数据库以及Scopus数据库。此外，还进行了未发表及在研数据的检索、相关期刊的手工检索，联系了相关作者并筛选参考文献列表。<b>纳入标准：</b>检索仅限定为英文发表的随机对照试验（randomized clinical trials, RCTs），此类研究需对比在接受固定矫治联合上颌前磨牙拔除治疗的任意年龄受试者中，采用直径≤2mm的机械固位型正畸微螺钉强化支抗，与传统支抗装置在前牙整体内收过程中的效果差异。<b>资料收集与分析：</b>采用盲法及双人重复的方式开展研究筛选、数据提取与偏倚风险评估。主要结局指标为上颌第一恒磨牙的近中移动量（即支抗丧失量）；次要结局指标包括治疗时长、复诊次数、不良事件及患者相关结局。采用Cochrane偏倚风险评估工具进行偏倚风险评价。对于具有可比性的结局指标，采用随机效应模型计算相应的95%置信区间（confidence interval, CI）。采用I²检验与卡方检验评估研究间的统计学异质性，并开展额外的敏感性分析。<b>结果：</b>共7项RCT符合纳入标准，但最终仅对来自6项RCT的241名受试者的数据（含250枚正畸微螺钉及134套传统支抗装置）进行了Meta分析。纳入研究的方法学质量从低到高不等。两组支抗丧失量的标准化均数差（standardized mean difference, SMD）为2.07 mm（95%CI：-3.05~-1.08，I²=88%，共6项RCT），结果偏向于正畸微螺钉组；剔除偏倚风险较高的研究后，该结果仍保持一致（SMD=1.94 mm，95%CI：-2.46~-0.42，I²=93%，共3项RCT）。关于总治疗时长、间隙关闭时长、治疗质量、患者报告结局、不良事件及复诊次数的相关数据较为有限。<b>结论：</b>本次Meta分析结果显示，现有中等质量证据表明，正畸微螺钉在维持正畸支抗方面的临床及统计学效果均优于传统支抗装置。但该结论仅得到少量方法学质量参差不齐的研究支持。未来需开展高质量RCT，以进一步明确正畸微螺钉在提供正畸支抗中的有效性。