Mandibular residual ridge morphology in relation to complete dentures and implant overdentures-Part II: Predictors for effectiveness of implant overdenture therapy.

BACKGROUND The significance of mandibular residual ridge height and satisfaction with conventional complete dentures (CCD) as predictors for the added value of implant-overdenture (IOD) therapy is unknown. PURPOSE To investigate the predictive value of thresholds for (1) residual ridge height at premolar location (PRH), and (2) satisfaction with CCD-stability for the added value of two intraforaminal implants supporting the mandibular CCD. METHODS Thirty CCD wearing patients (67.9 ± 7.0 years) for whom a new CCD was advised, received a new CCD. Mandibular gypsum models were digitally measured. After 3 months free of complaints (T1), perceived CCD-stability was evaluated, and participants received two intraforaminal implants. At T1 and T2 (3 months free of complaints after IOD therapy) participants completed OHIP14-CN, and denture satisfaction (VAS) questionnaires, and performed mixing ability tests. Participants were grouped according to PRH of ≥6.15 mm versus < 6.15 mm, and perceived CCD-stability satisfied vs. dissatisfied. Scores at T2 were compared to T1 (paired t-tests). Predictive values of PRH and CCD-stability were analyzed with logistic multivariate regression models. RESULTS At T2, only participants with PRH of <6.15 mm or dissatisfied with CCD-stability had significant lower OHIP-total and domain scores for 'physical pain' and 'physical disability' and significantly higher VAS scores for perceived chewing function, denture retention and oral comfort. Regression analyses showed that participants with PRH of <6.15 mm, or dissatisfied with CCD-stability had significantly higher chance for lower OHIP-total and domain scores 'physical pain' and 'physical disability', and for higher VAS scores for perceived chewing function, denture retention and oral comfort at T2. Masticatory performance improved significantly after IOD therapy, but independent of PRH and CCD-stability. CONCLUSION PRH and satisfaction with CCD-stability were adequate prognostic indicators for improvement of oral health-related quality of life and denture satisfaction by mandibular IOD therapy.