Influence of 2% chlorhexidine digluconate on bond strength of a glass-fibre post luted with resin or glass-ionomer based cement

Objectives: This study evaluated the influence of 2% chlorhexidine digluconate (CHX) on the bond strength (BS) of a glass-fibre post to the root canal, regarding the cements (dual-cured resin or resin-modified glass-ionomer cement), the root thirds and the time of storage. Method: Eighty bovine roots were selected and endodontically treated, before being randomly assigned to the following groups according to the luting protocol: ARC (RelyX ARC); ARC + CHX; RL (RelyX Luting 2); and RL + CHX. After 24 h of luting, the roots were sliced to obtain 1 mm-thick slices. Half of each group was submitted to either 7-day or 6-month storage in artificial saliva (n = 10). The specimens were subjected to push-out tests with a crosshead speed of 0.5 mm/min. The data were analysed with four-way ANOVA and Tukey's test (P <= 0.05). The failure modes were analysed with a digital microscope (50 x and 200x). Results: ARC yielded a significantly higher BS compared to RL (P < 0.001). Despite CHX exerted a significant effect; it depends on the interaction with the luting cement and time (P < 0.001). Thus, CHX decreased the values of BS to those of ARC after 6 months (P < 0.001). On the 7th day of storage, the ARC + CHX presented higher BS to the cervical and middle thirds compared to RL + CHX (P = 0.012). Time solely was not a significant factor (P = 0.081). Adhesive cement-dentine type and mixed failures were predominant modes for the ARC groups. For the RL groups, the main failures were adhesive cement-post and mixed modes. Conclusions: Glass-fibre posts luted with RelyX ARC dual-cure resin cement exhibited higher BS than those luted with RelyX Luting 2 resin-modified glass-ionomer cement. Furthermore, CHX was not effective to improve the BS and negatively affected the BS of RelyX ARC after 6 months of storage. Clinical significance: The use of chlorhexidine solution seems not to improve the bond strength of fibre posts to root canals, disregarding the composition of the luting cement. (C) 2014 Elsevier Ltd. All rights reserved.