The Quality of Evidence in Trials of Sugar-free Chewing Gum

Objectives: Whilst trials of sugar-free chewing gum suggest chewing gum may be anticariogenic, the quality of these trials has been questioned in reviews. The purpose of this review is to identify in a systematic manner these specific weaknesses in methodology and reporting. Methods: 17 studies of sorbitol or xylitol containing sugar-free chewing gum were identified using MEDLINE. Two assessors and an adjudicating third assessor individually assessed the trials for methodological quality and reporting adequacy according to a validated scale. Assessors were blinded to authors, institutions, sponsorship, publication year, and journal. Study results were not blinded so inconsistency across results could be assessed. The quality of evidence was graded according to the GRADE Working Group approach, which classifies non-randomised and field trials as observational studies. Results: Missing information was not sought from the authors, as the review sought to assess published evidence from the perspective of the general readership. Evidence from RCTs and observational studies was assessed as low and very low respectively. The major reporting weaknesses were in adverse event monitoring, participant flow and specification of inclusion and exclusion criteria. Weaknesses in methodology that failed to adequately address bias were inadequate subject blinding, and failure to account for compliance and loss to follow-up in analyses. The power of the studies was doubtful with sample size calculations rarely reported. The four reviewed RCTs utilised cluster randomisation by class or school, that latter of which was limited in control of bias. Conclusions: If the anticariogenicity of xylitol and sorbitol sugar-free chewing gums is to be established with confidence, future RCTs are indicated that minimise sources of bias in study design and substantially improve reporting standards.