Evaluation of the design-driven prediction of removable partial denture retention

Statement of problems. Removable partial dentures (RPDs) are a cost-effective treatment designed to replace missing teeth for partially edentulous patients. However, RPDs often have insufficient retention, which results in treatment failure and patient dissatisfaction. Purpose. The purpose of this clinical study was to investigate the factors related to RPD retention that affect patient satisfaction, to clinically validate a newly published model for predicting RPD retention based on the number and position of missing teeth and clasps, and to identify the predictions of patient satisfaction to improve the guidelines for RPD design. Material and methods. Seventy-five patients treated with 107 RPDs delivered at the McGill University Dental Clinic (Montreal, Canada) and Estaing University Hospital (Clermont-Ferrand, France) participated in this study. Data on the RPD design were collected from the clinical records, and the retention of each RPD was tested with the mathematical model designed for predicting RPD retention. Data on patient satisfaction with their RPDs were collected by using a standardized questionnaire (McGill Denture Satisfaction Instrument). Statistical analysis of factors related to RPD retention and patient satisfaction was performed by using the chi-square test and Mann-Whitney test, while the developed model for predicting RPD retention was evaluated by using sensitivity and specificity analysis. Results. The average satisfaction score for all RPDs was 8.2 +/- 1.7 out of 10. Patients were more satisfied with RPDs in the maxillary arch, tooth-supported, or retained by >= 3 clasps than with RPDs in the mandibular arch, with distal extension bases, or retained by <3 clasps. The materials used for RPD fabrication (metal-based or acrylic resin-based), the number of missing teeth, and the presence of indirect retention were not associated with patient satisfaction. Participants were significantly more satisfied with RPD designs predicted by the developed mathematical model to have enough retention than with RPD designs predicted to have insufficient retention. The mathematical model for predicting the RPD retention showed a clinical specificity of 83% in predicting patient satisfaction. Conclusions. RPD retention predicted from the number and position of clasps and missing teeth might help to determine patient satisfaction. In addition, patient satisfaction with RP Ds was influenced by the arch type, the presence of a distal extension base, and the number of clasps.