Influence of temporary cement contamination on the surface free energy and dentine bond strength of self-adhesive cements

Objectives: The surface free energy and dentine bond strength of self-adhesive cements were examined after the removal of temporary cements. Methods: The labial dentine surfaces of bovine mandibular incisors were wet ground with #600-grit SiC paper. Acrylic resin blocks were luted to the prepared dentine surfaces using HY Bond Temporary Cement Hard (HY), IP Temp Cement (IP), Fuji TEMP (FT) or Freegenol Temporary Cement (TC), and stored for 1 week. After removal of the temporary cements with an ultrasonic tip, the contact angle values of five specimens per test group were determined for the three test liquids, and the surface-energy parameters of the dentine surfaces were calculated. The dentine bond strengths of the self-adhesive cements were measured after removal of the temporary cements in a shear mode at a crosshead speed of 1.0 mm/min. The data were subjected to one-way analysis of variance (ANOVA) followed by Tukey's HSD test. Results: For all surfaces, the value of the estimated surface tension component γ _S ^d (dispersion) was relatively constant at 41.7-43.3 mJ m ^-2. After removal of the temporary cements, the value of the γ _S ^h (hydrogen-bonding) component decreased, particularly with FT and TC. The dentine bond strength of the self-adhesive cements was significantly higher for those without temporary cement contamination (8.2-10.6 MPa) than for those with temporary cement contamination (4.3-7.1 MPa). Conclusions: The γ _S values decreased due to the decrease of γ _S ^h values for the temporary cement-contaminated dentine. Contamination with temporary cements led to lower dentine bond strength. Clinical significance: The presence of temporary cement interferes with the bonding performance of self-adhesive cements to dentine. Care should be taken in the methods of removal of temporary cement when using self-adhesive cements.