Ceramic inserts do not generally improve resin composite margins

summary  Ceramic inserts are reported to possibly reduce polymerization shrinkage for posterior resin composite fillings. The aim of the present investigation was to evaluate the effect of different insert systems before and after thermomechanical loading. Sixty sound human third molars received occlusomesial Class II cavities, 40 with proximal margins 2 mm above and 20 with proximal margins 1 mm below the cementum‐enamel junction. The specimens were randomly assigned to one of the six experimental groups (n = 10). The enamel‐bordered cavities were restored with Syntac classic and Tetric Ceram (ST), Syntac classic, Tetric Ceram and β‐quartz inserts (TB), Syntac classic, Tetric Ceram and Cerana inserts (TC), Syntac classic, Tetric flow and SonicSys approx inserts (TS). The dentin‐limited cavities were filled with Syntac classic and Tetic Ceram (DT), Syntac classic, Tetric flow and Sonic Sys approx inserts (DS). Before and after thermomechanical loading (100 000 × 50 N, 2500 × 5 °C/55 °C), replicas were made and both interfaces tooth/composite and insert/composite were examined under a scanning electron microscope at 200×. The Cerana and Sonic Sys insert groups showed significantly less gaps in enamel (P < 0·05). With β‐quartz inserts, no reduction of gaps was found (P > 0·05). Marginal integrity in dentine‐bordered specimens could not be improved with Sonic Sys inserts (P > 0·05). The bonding performance insert/composite was promising for all IPS Empress inserts (Cerana, Sonic Sys enamel) but worse for β‐quartz inserts. Regarding gap formation between resin composite and tooth, Cerana and SonicSys inserts significantly reduced gaps. The use of SonicSys inserts in deep proximal cavities cannot be recommended.