Seating-related adaptation and deformation of components of removable partial denture frameworks fabricated by different workflows.

Statement of problem: Removable partial denture (RPD) frameworks have traditionally been produced by conventional impression making and casting. Due to the popularity of intraoral scanning (IOS) and digital manufacturing, RPD frameworks can be produced by alternative workflows.

Purpose: The purpose of this in vitro study was to assess the seating-related adaptation and deformation of components of RPD frameworks fabricated by different workflows.

Materials and methods: A partially edentulous mandibular arch was used as the master model. Three RPD framework manufacturing workflows were evaluated: the conventional impression making and casting (Imp-Cast) group, conventional impression making and digital fabrication by selective laser melting (Imp-SLM) group, and IOS and digital fabrication (IOS-SLM) group. According to each workflow, 10 frameworks were produced. The virtual superimposition of seated and unseated frameworks was executed to determine component adaptation (retentive arm, reciprocating arm, and occlusal rest) and component deformation (retentive arm and framework body). The 1-way analysis of variance (ANOVA) test was used to determine the differences among the groups (α=.05).

Results: No difference in component adaptation was observed for Imp-Cast and Imp-SLM (P>.05), and both were better than IOS-SLM (P<.001). The least retentive arm deformation was observed for Imp-SLM. Imp-Cast and Imp-SLM showed no difference in framework body deformation (P=.92), and both were better than IOS-SLM (P<.05). The IOS-SLM frameworks appeared narrower than the master model.

Conclusions: Frameworks fabricated from conventional casts exhibited comparable adaptation of components. In some comparisons, SLM fabrication was associated with less deformation than casting. Frameworks fabricated from IOS had the greatest adaptation error and deformation. As all the frameworks were seated on the master model without adjustment, the clinical relevance of this study's finding is yet to be determined.