Purpose: The results of trials can inform health care decisions. However, this is dependent on both clear and transparent reporting. The aim of this study was to assess the reporting quality of split-mouth trials in implant dentistry in relation to the CONSORT extension checklist for reporting within-person randomized clinical trials (RCTs).

Materials and methods: Split-mouth trials published between January 1, 1997, and September 30, 2020, were identified from four databases. Study characteristics at the level of each trial were extracted. Each trial was assessed against a 37-item checklist and assigned one of four categories. Descriptive statistics and the frequencies of the ratings per checklist item were calculated. A percentage score was calculated per study. Linear regression assessed associations between the aggregate score and the study characteristics.

Results: Two hundred forty-four trials were analyzed. More than 50% of the RCTs were published between 2016 and 2020, were published in specialty journals (81.2%), and were interventional-type RCTs (98.4%). Generally, the reporting of checklist items was suboptimal in many areas. The reporting score was predicated by the number of authors (> 7 vs baseline [1 to 4] authors: β: 6.00; 1.48, 10.52; P = .01), authors' continent (Europe vs Americas: β: 5.30; 0.85, 9.74; P = .02), and the number of participants (per-unit increase: β: .07; 0.01, 0.12; P = .02).

Conclusion: The reporting of split-mouth trials in implant dentistry seems to be suboptimal. The endorsement and adherence to the CONSORT extension for the within-person trials checklist by journal editors and investigators could improve reporting quality and transparency.