ORIGINAL ARTICLE Clinical evaluation of a low-shrinkage resin composite in endodontically treated premolars: 3-year follow-up Nihan Gönülol 1 & Elif Kalyoncuoğlu 2 & Ertan Ertaş 1 & Tuğba Misilli 3 Received: 22 August 2017 /Accepted: 1 October 2018 # Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Objectives This study compared the 3-year clinical performance of a low-shrinkage silorane-based composite material with that of a methacrylate-based composite material in the restoration of endodontically treated premolar teeth. Materials and methods A total of 70 patients requiring a Class II composite-resin restoration of a premolar tooth following root- canal treatment participated in the study. Cavities were restored with either a silorane-based restorative (Filtek Silorane + Silorane System Adhesive) or a methacrylate-based restorative (Filtek Z250 + Clearfil SE Bond) system applied according to the man- ufacturer’ s instructions. Restorations were evaluated by two blinded observers at five different time intervals (baseline; 6 months; 1, 2, and 3 years) according to modified USPHS criteria. Pearson’ s chi-square tests were used to examine differences in the clinical performance of the materials (retention, color match, marginal discoloration, secondary caries, anatomical form, marginal adaptation, and surface roughness), and Friedman and Wilcoxon tests were used to compare changes between baseline and each recall time, with a level of 0.05 considered statistically significant. Results After 3 years, no statistically significant differences in clinical performance were observed between the two materials (p > 0.05). Intra-system comparisons revealed a statistically significant deterioration in color match, marginal discoloration, anatomical form, marginal adaptation, and surface roughness scores after 3 years for both systems. Although the difference was not significant at 3 years of follow-up, the level of deterioration in marginal adaptation and surface roughness was greater for the Filtek Silorane restoration than for the Filtek Z250 restoration at the 1 year follow-up (p > 0.05). Conclusion Restorations of both materials were clinically acceptable after 3 years. The Filtek Silorane system did not appear to offer any clinical advantages over the methacrylate-based system when used in the restoration of Class II cavities in endodon- tically treated premolars. Clinical relevance The restoration of endodontically treated premolars with minor or moderate loss of tooth structure can be directly performed either with silorane or methacrylate-based composite resins. Keywords Class II restoration . Endodontic treatment . Randomized clinical trial . Resin-based composite . Silorane Introduction Endodontically treated teeth may be weakened due to a sub- stantial loss of tooth structure caused by pre-existing caries and restorations as well as endodontic procedures [1]. Just what constitutes the optimal restoration of endodontically treated teeth that will guarantee the success of treatment remains con- troversial [2]. Appropriate restoration is mainly dependent upon the remaining coronal tooth structure and the functional require- ments of the tooth. Coronal coverage has been advocated as a means of strengthening endodontically treated molar and pre- molar teeth in cases of extensive loss of tooth structure [3, 4]. However, treatment options for non-vital teeth with minor loss of coronal hard tissue have received little attention [5–7]. For teeth with only minor or moderate loss of tooth structure, the adhesive properties of resin-based composites could make them a preferable alternative to crown placement, allowing for min- imal cavity preparation while strengthening the remaining cor- onal hard tissue and providing satisfactory esthetics [3, 8]. * Nihan Gönülol nihan.gonulol@omu.edu.tr 1 Faculty of Dentistry, Department of Restorative Dentistry, Ondokuz Mayis University, Samsun, Turkey 2 Faculty of Dentistry, Department of Endodontics, Ondokuz Mayis University, Samsun, Turkey 3 Faculty of Dentistry, Department of Restorative Dentistry, Çanakkale Onsekizmart University, Çanakkale, Turkey Clinical Oral Investigations https://doi.org/10.1007/s00784-018-2677-6