Abstract
Background: The evidence stemming from trials on restorative materials is shaped not only by trial findings, but also trial design and validity. We aimed to evaluate both aspects in randomized controlled dental restorative trials published from 2005–2015. Methods: Using systematic review methodology, we retrieved trials comparing restorative or adhesive dental materials. Two authors independently assessed design, risk of bias, registration status, and findings of trials. Descriptive and regression analyses were performed. Results: 114 studies on 15,321 restorations placed mainly in permanent teeth of 5232 patients were included. Per trial, the median number of patients was 37 (25th/75th percentiles: 30/51). Follow-up was 24 (20/48) months. Seventeen percent of trials reported on sample size calculations, 2% had been registered. Most trials (90%) used US Public Health Service (USPHS) criteria, and had a high risk of bias. More recent trials were more likely to have been registered, to have reported on sample size calculations, to be of low risk of bias, and to use other than USPHS-criteria. Twenty-three percent of trials yielded significant differences between groups. The likelihood of such differences was significantly increased in older studies, studies with potential reporting bias, published in journals with high impact factor (>2), longer follow-up periods, and not using USPHS-criteria. Conclusions: The majority of dental restorative trials published from 2005–2015 had limited validity. Risk of bias decreased in more recent trials. Future trials should aim for high validity, be registered, and use defined and appropriate sample sizes, follow-up periods, and outcome measures.
Highlights
While randomized controlled trials remain the cornerstone of clinical research, there is increasing focus on the validity of clinical studies
The quality and comprehensiveness of reporting was found to impact on the credibility and applicability of trials [3], which is one reason why registration of clinical trials is increasingly seen as a requirement for performing such trials, reducing risks of selective reporting
After screening titles and abstracts, 97 articles were assessed full-text. 169 further articles were identified by screening the reference lists of the 97 retrieved articles and existing systematic reviews
Summary
While randomized controlled trials remain the cornerstone of clinical research, there is increasing focus on the validity of clinical studies. Like unit of randomization or choice of outcome measure, might impact on trial findings. Publication bias might distort the truly-found comparative effects, as significant findings are more often published [4]. The evidence stemming from trials on restorative materials is shaped by trial findings, and trial design and validity. We aimed to evaluate both aspects in randomized controlled dental restorative trials published from 2005–2015. Methods: Using systematic review methodology, we retrieved trials comparing restorative or adhesive dental materials. Two authors independently assessed design, risk of bias, registration status, and findings of trials.
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