The effect of different liners on the bond strength of a compomer to primary teeth dentine: in vitro study.

Objective: This in vitro investigation should identify the effect of protective liners on dentine bond strength of a polyacid modified resin composite to dentine of primary teeth.

Methods: Forty-two extracted caries-free primary molars were randomly assigned to seven groups (n = 6) and flattened. Six test groups were centrally covered with different protective liners/base materials: Kerr Life (KL), IRM zinc oxide eugenol cement (IRM), Ketac Bond (KB), Vitrebond (VB), Dycal (DY), and mineral trioxide aggregate (MTA). Specimens were bonded with Prime&Bond NT (PB) and restored with Dyract eXtra. The control group (C) did not receive liner pretreatment. After 24-h storage in Aqua dest. (37 °C), specimens were cut and regional microtensile bond strengths of the uncovered areas were tested. Fractography was conducted under a light microscope and further interface/surface analyses were performed under a SEM. Statistical appraisal was carried out using oneway ANOVA (mod. LSD test; p < 0.05).

Results: Independent of the distance to the applied liner, all groups exhibited inferior μ-TBS to dentine of primary teeth compared to the control group (p < 0.05). The results were as follows in MPa(SD) ^x:significance level/percentage of adhesive fractures: PB: 34 (10)^A/72%; KL: 23 (25)^B/64%; KB: 15 (12)^C/76%; DY 15 (13)^C/55%; IRM: 14 (10)^C/68%; VB: 12 (10)^C/61%; MTA 12 (10)^C/69%.

Conclusions: Protective liners significantly reduced μ-TBS to dentine of primary teeth.