Purpose:Effective use of mechanical plaque control devices can depend on individual manual dexterity levels. The purpose of this component of a 12-week, virtually-supervised clinical trial was to investigate the role of manual dexterity on clinical outcomes for gingivitis, as measured by the relationship between manual dexterity scores on the Purdue Pegboard Test (PPT) and the effects of various mechanical and chemotherapeutic oral hygiene regimens.Methods:This was a single-center, examiner blinded, randomized, four-treatment arm, parallel group, 12-week plaque and gingivitis study. At baseline, healthy adult volunteers with evidence of gingivitis were assessed for manual dexterity and were then examined for plaque, gingivitis and bleeding. After a dental prophylaxis, participants were randomized into four treatment groups: brush only (BO); brush/rinse (BR); brush/floss (BF); and brush/floss/rinse (BFR). The flossing groups received instruction in flossing. The PPT was used to assess manual dexterity and was performed by a licensed occupational therapist. Virtual supervision was required once each weekday and the oral hygiene regimen was unsupervised on evenings and weekends.Results:Of the 213 subjects enrolled, 209 completed the trial. Improvements from baseline to week 12 in interproximal percent nonbleeding healthy sites (Expanded Bleeding Index (EBI)=0 and Modified Gingival Index (MGI)=0 or 1) were dependent on the participant’s dexterity score. Participants with the lowest dexterity scores (9 or lower) in the BFR treatment group demonstrated the greatest improvement interproximally based on the indices (EBI and MGI). In comparison, the BF test group subjects with dexterity scores 9 or lower had limited change in improvement interproximally. There was a direct correlation between flossing effectiveness and dexterity scores.Conclusions:Less manual dexterity can limit dental flossing effectiveness. Flossing is a difficult daily task that requires functional bilateral dexterity to be perform correctly. Individuals with lower levels of manual dexterity were shown to benefit from the addition of an essential oil mouthrinse to a regimen of toothbrushing and flossing in this clinical trial. The addition of an essential oil mouthrinse improved interproximal gingival health and mitigated the manual dexterity variable.