Optical integration of incisoproximal restorations using the natural layering concept

Objective: To evaluate the optical integration of 4 contemporary composite resin materials used for incisoproximal restorations and the natural layering concept. Method and Materials: Miris 2 (M2; Coltene Whaledent), Gradia Direct (GD; GC), Enamel Plus HFO (HFO; Micerium), and Filtek Supreme Plus (FSP; 3M ESPE) composite resins were used to consecutively restore 6 extracted incisors with incisoproximal restorations using the natural layering concept, mimicking the natural anatomy of the tooth with only 2 composite resin masses (dentin and enamel). Following each restoration, the specimen was allowed to rehydrate for 2 weeks and was then photographed under standardized conditions (direct, indirect, and fluorescent lights). Six independent evaluators scored each light condition using an optical integration score on a scale from 1 to 4 (1 = worst optical integration, restoration can be easily distinguished from remaining tissues; 4 = optimal optical integration, restoration "invisible"). Mean optical integration scores (from the 6 evaluators) were analyzed with a 2-way analysis of variance (ANOVA) (composite resin brand and light condition). Pooled data of M2 and HFO (single-hue systems) and GD and FSP (multiplehue systems) were also analyzed with a 2-way ANOVA (shade system and light condition). Results: M2 obtained the highest optical integration scores (P .03), followed by GD and HFO (not significantly different, P = .99). FSP showed the least favorable optical behavior (P .0001), which is explained in part by the lack of fluorescence and possible inappropriateness for use with the natural layering technique. Single-hue systems (M2 and HFO) achieved better optical integration (P .02) compared to multihue systems (GD and FSP). Conclusions: For M2, the simplified natural layering concept produced incisoproximal restorations with excellent optical integration. GD and HFO are also suitable for this technique. FSP failed to produce acceptable optical integration in the present study. Keywords: composite resin, dental esthetics, natural layering technique, optical integration