Does motivational interviewing or oral hygiene instruction improve plaque control?

Both motivational interviewing (MI) and traditional oral hygiene instruction (OHI) appear capable of improving plaque control, though the evidence on which approach is superior is mixed and overall limited in quality.

In a 12-month RCT, both traditional OHI and brief MI groups showed significant reductions in plaque score over time, with the OHI group actually showing a statistically greater improvement in plaque score at visits three and four ^[1]. However, pooled data from a 2024 meta-analysis found no significant difference in plaque levels between MI and control groups overall ^[2], and a 2024 community-level meta-analysis similarly found only a marginal, non-significant summary effect favouring MI for plaque index (-3.59 percentage points, CI crossing zero) ^[3].

An earlier 2017 systematic review noted that in two of five included studies MI did show a significant positive effect on plaque values, while two studies showed no influence, highlighting inconsistency across trials ^[4]. A 3-year follow-up of a single-MI-session RCT found that both test and control groups maintained similarly desirable plaque scores over time, and the single MI session could not be shown to add long-term benefit beyond conventional therapy alone ^[5].

At the 3-year longitudinal follow-up of the brief MI trial, the time-by-group interaction for plaque score did not reach statistical significance (p=0.12) between MI and OHI groups ^[6]. Overall, both approaches can support plaque reduction, but current evidence does not consistently demonstrate that MI is superior to traditional OHI for plaque control, and additional high-quality, standardised trials are needed before firm conclusions can be drawn ^[2][4].