Maxillary Protraction Appliance For Treatment Of Skeletal Class III Malocclusion In Children:a Systematic Review

Objective: To evaluate the effects of maxillary protraction appliance and maxillary protraction appliance combined with other appliances for treatment of skeletal class III.Methods: A literature search was carried out in international databases(MEDLINE, ISI Web of science, the Cochrane Central Register of Controlled Trials, Science Direct and EMBASE), Chinese language databases (CNKI, VIP, Wanfang and CBM) and using handing search (Campbell library, NLM and WHOLIS)up till December 2009 to identify all clinical control trials on maxillary protraction appliance for correction of skeletal class III malocclusion. Data was independently extracted by two reviewers and a quality assessment was carried out. The Cochrane Collaboration's RevMan 5.0 software was used for data analysis. Meta analysis was carried out using fixed or random effect model. If the pooled articles were found to have heterogeneity, subgroup analysis or sensitivity analysis was carried out and if the articles could not be pooled together, then descriptive analysis was used.Results: Nineteen Controlled clinical studies matched the inclusion criteria, only one article was found to be RCT and eighteen articles were non-RCTs. Among nineteen articles, seven articles used maxillary protraction appliance, twelve articles used maxillary protraction appliance combined with rapid maxillary expansion (both maxillary protraction appliance and maxillary protraction appliance combined with rapid maxillary expansion were used in two studies), one article used MPBA and another article made use of maxillary protraction appliance combined with chin cup. Methodologic quality assessment showed the RCT was low level and of the eighteen CBAs, five articles were C level and thirteen articles were B level.1) Maxillary protraction applianceMeta analysis of four articles, involving 112 patients, showed that the change in SNA, SNB, ANB and ANS-Me of the two groups was statistically different, except for U1-NA, which did not show any statistically significant differences.2) Maxillary protraction appliance combined with rapid maxillary expansionMeta analysis of eight articles, involving 275 patients, showed the change in SNA, SNB, ANB, ANS-Me and Wits of the two groups to be statistically different, except for U1-NA which did not any have statistically significant differences. 3) MPBAOne article involving 120 patients, showed statistically significant differences when the experimental group(deciduous and mixed dentition) was compared to the control group, however,the changes found in the deciduous dentition experimental group was more significant than those of the mixed dentition group.4)Maxillary protraction appliance combined with chin cupIn one article involving 40 patients, treatment with maxillary protraction appliance combined with chin cup resulted in forward movement of the maxilla, backward and downward rotation of the mandible and labial movement of upper incisors.5)Stability of treatmentFour articles assessing the stability of treatment,found that the maxilla and mandible had relapsed during the follow-up study, however, over correction is more effective for stability.Conclusion:1. Treatment with maxillary protraction appliance and maxillary protraction appliance combined with other appliances resulted in maxillary forward movement and downward and backward rotation of the mandible.2. The benefits of treatment with maxillary protraction appliance is, enhanced maxillary forward movement and mandible rotation, however, the application of different forces (300g,400g and 600g per side)yields different effects,and moreover, no significant changes in the upper incisor position(U1-NA) was seen.3. Maxillary protraction combined with rapid maxillary expansion results in significant forward maxillary movement. When the force is 200-600g per side, the appliance is more effective in limiting the mandibular forward movement. It also results in downward and backward rotation of mandible with a net increase in ANS-Me length. However, no significant changes in the upper incisor position(U1-NA) was seen.4. The quality of the nineteen articles was not high since only one was RCT. There is evidence showing that maxillary protraction appliances have significant effects on skeletal class III, however, there is a need for more multiple samples and high quality RCTs, to confirm this conclusion.