Fewer teeth, same accuracy: a faster way to score plaque

Clinical question: can a reduced, partial-mouth plaque recording protocol reliably approximate full-mouth plaque scores, and can data-driven subsets outperform established schemes like Ramfjord or CPITN?

Methodology: disclosed-plaque intraoral scans were obtained from 30 adults at three timepoints — baseline, after 72 hours of plaque accumulation, and after toothbrushing. Plaque was quantified both planimetrically (percentage plaque coverage) and with two established indices (Turesky-modified Quigley-Hein and Rustogi-modified Navy Plaque Index). The established Ramfjord (6 teeth/12 surfaces) and CPITN (6 teeth/12 surfaces or 10 teeth/20 surfaces) subsets were compared against full-mouth recordings, alongside newly optimized subsets derived directly from the observed plaque distribution and additional subsets targeting plaque-prone sites. Agreement was assessed with bias, root-mean-square error, and intraclass correlation coefficients (ICC).

Main findings: an optimized 12-surface subset showed near-perfect agreement with full-mouth percentage plaque coverage (bias 0.03, ICC 0.962); the 12-surface CPITN performed similarly well (ICC 0.967). The classic Ramfjord subset slightly underestimated full-mouth plaque but retained high agreement (ICC 0.970), and even a reduced 6-surface Ramfjord subset preserved strong agreement (ICC 0.954). The clear outlier was the 20-surface CPITN, which consistently overestimated full-mouth plaque (bias 4.33, ICC 0.839) — more surfaces did not mean better accuracy. Subset performance was consistent across oral hygiene stages and across all three plaque metrics tested.

Clinical relevance: this study offers practical reassurance for time-pressed practice and research settings — with one important exception. Most partial-mouth schemes, including the well-established Ramfjord index and a compact 6-surface variant, closely track full-mouth plaque scores, making them defensible shortcuts for monitoring hygiene over time. The 20-surface CPITN, however, is the one scheme shown here to systematically overestimate plaque, a useful caution for anyone relying on it as a proxy for full-mouth status. For plaque-prone-site monitoring specifically, the newly developed elevated-plaque subsets offered the best targeted alternative.