Self-determined motivational predictors of increases in dental behaviors, decreases in dental plaque, and improvement in oral health: a randomized clinical trial.

OBJECTIVE The present study tested the hypotheses that: (a) a dental intervention designed to promote dental care competence in an autonomy-supportive way, relative to standard care, would positively predict perceived clinician autonomy support and patient autonomous motivation for the project, increases in autonomous motivation for dental home care, perceived dental competence, and dental behaviors, and decreases in both dental plaque and gingivitis over 5.5 months; and (b) the self-determination theory process model with the intervention and individual differences in autonomy orientation positively predicting project autonomous motivation and increases in perceived dental competence, both of which would be associated with increases in dental behavior, which would, in turn, lead to decreased plaque and gingivitis. METHODS A randomized two-group experiment was conducted at a dental clinic with 141 patients (Mage = 23.31 years, SD = 3.5), with pre- and postmeasures (after 5.5 months) of motivation variables, dental behaviors, dental plaque, and gingivitis. RESULTS Overall, the experimental and hypothesized process models received strong support. The effect sizes were moderate for dental behavior, large for autonomous motivation for the project and perceived competence, and very large for perceived autonomy support, dental plaque, and gingivitis. A structural equation model supported the hypothesized process model. CONCLUSIONS Considering the very large effects on reductions in dental plaque and gingivitis, promoting dental care competence in an autonomy-supportive way, relative to standard care, has important practical implications for dental treatment, home care, and health.