Unusual Findings in Trials Evaluating Adjuncts to Scaling and Root Planing: Meta-analysis (Part 1)

A number of studies in patients with periodontitis have compared scaling and root planning (SRP) combined with an adjunctive treatment to SRP alone. Within that literature, an array of studies with overlapping investigators has consistently yielded substantially greater effects of adjunctive treatments than had been previously noted. This report investigates discrepancies between that cluster of research and the most recent American Dental Association (ADA) systematic review.

This review was preregistered at https://osf.io/4meyd/. A search using the Scopus platform identified 32 articles published from 2010 to 2017 by investigators affiliated with the Government Dental College and Research Institute (GDCRI) in Bangalore, India. The primary outcome used in this meta-analysis was the change in clinical attachment level (CAL) after 6 mo. Effect sizes were estimated using Comprehensive Meta-Analysis software after categorizing agents into groups based on pharmacologic similarity.

The search identified 32 studies encompassing 5 sets of adjunctive agents. Across the GDCRI studies, the CAL averaged 1.67 mm (95% confidence interval [CI]: 1.43-1.91 mm), substantially exceeding values reported in the ADA review (mean: 0.39 mm, 95% CI: 0.27-0.51 mm). For categories of studies in which comparable subgroup estimates were available, the evaluations yielded overlapping estimates of SRP alone, but CAL estimates were discrepant for both locally delivered antimicrobials (GDCRI studies: mean: 1.45 mm, 95% CI: 0.63-2.27 mm; ADA review: mean: 0.38 mm, 95% CI: 0.16 -0.60 mm) and systemic antibiotics (GDCRI studies: mean: 1.35 mm, 95% CI: 0.97-1.73 mm; ADA review: mean: 0.39 mm, 95% CI: 0.21-0.57 mm).

In the literature on adjunctive agents supplementing SRP, findings from investigators linked to GDCRI stand out as having significantly more favorable estimated effects. Meanwhile, some agents studied by GDCRI-linked investigators have not been investigated by other researchers. In the absence of a clear explanation for discrepant results, it is recommended that unusually favorable reported effects of adjunctive agents be viewed with caution.

The present meta-analysis observed an unusually large effect size of adjunctive agents to scaling and root planning in studies conducted by the same research group. These results were not consistent with trials on adjunctive agents and previous reports. As this research group has exclusively tested most of the agents, their results must be viewed with caution until other independent groups replicate the studies and reproduce the effect size.