Influence of distal extension length of free-end RPD on mastication

Objectives: This study aimed to evaluate masticatory performance, selection chance, breakage function, and masticatory ability of removable partial denture (RPD) wearers presenting different occlusal support extension. Methods: It was selected eighteen subjects with maxillary edentulism and mandibular Kennedy class I edentulism presenting only anterior teeth. Mean age of subjects was 54.2 ± 8.3 years. Removable complete and partial dentures were accomplished for maxilla and mandible, respectively. Occlusal support of RPD was gradually shortened determining the following cumulative conditions: complete occlusal support, occlusal support until first molar; until second premolar; until first premolar; and absence of occlusal support. Comminution of Optocal test food and sieve method were used for masticatory performance, selection chance and breakage function tests. Masticatory ability was registered using a Likert self-perception questionnaire. Results were submitted to repeated measures one-way ANOVA and Friedman tests (a = 0.05). Results: Subjects presenting complete occlusal support showed higher masticatory performance values than when their occlusal support was reduced until first (p < 0.001) and second (p < 0.0001) premolars, and in absence of occlusal support (p < 0.0001). No difference was found between masticatory performance reached by subjects presenting complete occlusal support and occlusal support until first molar (p > 0.05). Selection chances and breakage function also were reduced progressively as occlusal support was shortened (p < 0.0001). A decreased masticatory ability only was perceived when subjects had occlusal support until first premolar and in absence of occlusal support. Conclusions: Within the limitations of this study, it was suggested that occlusal support of RPD should be extended at least to first molars to prevent a reduction of masticatory function.