Quality of Split-Mouth Trials in Dentistry: 1998, 2008 and 2018

Danchen Qin, Fang Hua, Shengjie Liang, Helen Worthington, Tanya Walsh

Research output: Contribution to journalArticlepeer-review


The objectives of this study were to assess the reporting quality and methodological quality of split-mouth trials (SMTs) published during the last two decades, and to determine whether there has been an improvement in their quality over time. We searched the MEDLINE database via PubMed to identify SMTs published in 1998, 2008, and 2018. For each included SMT, we used the CONsolidated Standards Of Reporting Trials (CONSORT) 2010 guideline, CONSORT for within-person trial (WPT) extension and a new three-item checklist to assess its trial reporting quality (TRQ), WPT-specific reporting quality (WRQ) and SMT-specific methodological quality (SMQ), respectively. Multivariable generalized linear models were performed to analyze the quality of SMTs over time, adjusting for potential confounding factors. A total of 119 SMTs were included. The mean overall score for TRQ (score range, 0 to 32), WRQ (0 to 15) and SMQ (0 to 3) was 15.77 (SD 4.51), 6.06 (2.06) and 1.12 (0.70), respectively. The primary outcome was clearly defined in only 28 SMTs (23.5%), and only 27 (22.7%) presented a replicable sample size calculation. Only forty-five SMTs (37.8%) provided the rationale for using a split-mouth design. The correlation between body sites was reported in only 5 studies (4.2%) for sample size calculation, and 4 studies (3.4%) for statistical results. Only 2 studies (1.7%) performed an appropriate sample size calculation, and 46 (38.7%) chose appropriate statistical methods both accounting for the correlation among treatment groups and the clustering / multiplicity of measurements within an individual. Results of regression analyses suggested that the TRQ of SMTs improved significantly with time (P < 0.001), while there was no evidence of improvement in WRQ or SMQ. Both the reporting quality and methodological quality of SMTs still have much room for improvement. Concerted efforts are needed to improve the execution and reporting of SMTs.
Original languageEnglish
JournalJournal of Dental Research
Publication statusAccepted/In press - 9 Jul 2020


  • clinical trials as topic
  • evidence-based dentistry
  • research design
  • medical writing
  • sample size
  • statistics as topic


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