Zinc oxide eugenol paste jeopardises the adhesive bonding to primary dentine.

AIM: This was to evaluate the influence of root canal filling pastes on microshear bond strength (microSBS) of an adhesive system to primary dentine. METHODS: Human (32) primary molars were randomly assigned into four experimental groups (n = 8): zinc oxide eugenol paste (ZOE); iodoform paste (Guedes-Pinto paste); calcium hydroxide paste thickened with zinc oxide; and no filling paste (control). Flat dentine surfaces were covered with a 1 mm-thick layer of the pastes for 15 min at 37 degrees C. The pastes were mechanically removed from dentine surfaces, followed by rinsing and drying. After adhesive application (Adper Single Bond 2, 3M ESPE), starch tubes were placed over pre-treated dentine and filled with composite resin (Z250, 3M ESPE). The microSBS test was performed after 24 h of water storage at 37 degrees C. The failure mode was evaluated using a stereomicroscope. The microSBS values (MPa) were analysed with one-way ANOVA and Tukey post-hoc tests (alpha = 0.05). RESULTS: The lowest microSBS values were achieved when ZOE was used. No difference was found among other filling pastes compared with control group. All specimens showed adhesive/mixed failures. CONCLUSIONS: Zinc oxide eugenol paste negatively influenced the bond strength of adhesive systems to primary dentine. Iodoform-based Guedes-Pinto paste and calcium hydroxide paste thickened with zinc oxide did not influence the microshear bond strength values.