Systematic Review of Systematic Reviews: A critical appraisal of the current evidences in orthodontics
Creators: name: Bucci, Rosaria
Publisher: name: Università degli Studi di Napoli Federico II
Year: 2015

description: Background: Systematic Reviews (SRs) and Meta-analyses (MAs) are the preferred research approaches to manage the growing number of clinical trials, since they bring together the results from multiple studies by applying rigorous methods, and provide summarized and critically appraised evidence on a given topic. Several orthodontic issues suffer from overwhelm of primary literature, and is frequent to find more than one SR on the same topic showing variable quality and scope. The diffusion of systematic approach made difficult to keep track of the number of SRs that are being published. Hence, SRs of SRs were introduced to integrate and to synthesise information from existing SRs. 
Objectives: The aims of this doctoral thesis were: (1) to assess the quality of SRs and MAs of debated issues in the orthodontic literature, (2) to collect the results provided by SRs and MAs and to critically appraise the evidence within reviews. More specifically, the current study focused on two issues: the functional orthopaedic treatment of Class II malocclusion and the dentoalveolar effects of palatal expansion.
Materials and Methods: Two separate literature reviews were conducted.
In the first review, SRs and MAs focusing on the effects of the functional orthopaedic treatment of Class II malocclusion in growing patients were included. In the second one, SRs and MAs focusing on the dentoalveolar and skeletal effects of palatal expansion were included. 
The methodological quality of each included SR or MA was assessed using the AMSTAR (A Measurement Tool to Assess Systematic Reviews). The level of evidence of the primary studies included in each SR or MA was assessed according to hierarchy of the evidence, and reported with the LRD scoring (Level of Research Design scoring). The main outcomes were summarized and the evidences retrieved were critically appraised applying pre-determined statements. Literature search, study selection, quality assessment and data extraction were independently conducted by two operators, and consensus was reached through discussion. 
Results: For the first SR fourteen studies on Class II treatment were included. The quality of SRs/MAs ranged between AMSTAR 2 and 10 (mean score: 6) and three SRs/MAs included only Randomized Clinical Trials (RCTs) (LRD II). The main outcomes analysed were: dentoalveolar effects, maxillary skeletal effects, mandibular effects and soft tissues effects. According to the current evidence provided by SRs and MAs there was still no sufficient evidence on the effects of Class II functional orthopaedic treatment, due to the small number of adequate MAs, the small number of primary studies for each outcome, and the low-medium quality of primary literature. However, we found some evidence of reduction of the overjet with different functional appliances, some evidence of maxillary growth control with Twin-Block and headgear and some evidence of mandibular length increasing with different functional appliances, even though the clinical relevance of the latter results was questionable. 
For the second SR twelve studies on dentoalveolar and skeletal effects of palatal expansion were included. The quality of SRs/MAs ranged between AMSTAR 4 and 10 (mean score: 6.8) and two SRs/MAs included only RCTs (LRD II). The main outcomes analysed were short- and long-term effects of rapid and slow maxillary expansion (RME/SME) on dentoalveolar and skeletal structures in the three directions (sagittal, vertical and transversal). According to our findings there was high level of evidence that RME determined a significant increase of transverse dentoalveolar maxillary dimensions in the short-term; however, long-term maintenance of this result seemed to be strongly influenced by the retention protocol and was supported by moderate evidence. Meanwhile, also SME showed similar results, but supported by moderate to low evidence. Maxillary skeletal expansion was mainly reported in the short-term with RME, but with low evidence.
Conclusions: Due to the variable quality of SRs and MAs in orthodontics clinicians should be aware of the existent tools to assess strength and weakness of these studies, in order to adequately recognize whenever limited information are provided.
SRs and MAs did not provide sufficient evidence to make a final decision about the effectiveness or ineffectiveness of Class II functional orthopaedic treatment, while RME was reported as an effective procedure for the short-term correction of dental transversal discrepancies.