Shear Bond Strength of Self-Adhesive Cements on Paediatric Zirconia Kiddy-Caps-Crowns

Objectives: The aim of the present study was to evaluate the shear bond strength (SBS) of four different self-adhesive resin cements to a new zirconia ceramic paediatric crown material (Kiddy-Caps; FIMA, Germany) for primary molars in vitro.
Methods: Eighty zirconia ceramic crown specimens of 3.0 mm diameter and 5.0 mm height were included and randomly assigned to four different cementation procedures of twenty samples each: B: Bifix SE (Voco) M: Maxcem (Kerr), P: Permacem 2.0 (DMG) and R: RelyX Unicem (3M Espe). Each crown sample was luted to a stainless steel test piece (1.5 cm x 1 cm, 3 mm thickness) using the assigned self-adhesive resin cement and following the instructions of the manufacturer. The stainless steel specimens were pre-treated with Rocatec Plus and silanized prior to cementation. Shear bond strength between zirconia ceramic and cement was measured after 24 h storage in 37°C distilled water using a universal testing machine.
Results: Following SBS were evaluated (mean values and standard deviations in MPa): B: 15.27 (+/-3.49), M: 19.50 (+/-3.01), P: 27.56 (+/-4.47), R: 18.56 (+/-4.81). Statistical analysis showed a significant influence of the used self-adhesive system on SBS (p<0.05, ANOVA). The highest SBS were observed in ceramic specimens cemented with Permacem 2.0 (group P) (p<0.001, Tukey test). Pairwise comparison between Maxcem (group M) and RelyX Unicem (group R) as well as between Bifix SE (group B) and RelyX Unicem (group R) presented no significant differences (p>0.05, Tukey test).
Conclusions: Although Permacem 2.0 showed a significant higher initial shear bond strength on the Kiddy-Caps specimens than the other tested self-adhesive cements, all resin cements showed good initial bonding capacity. Further investigations will have to focus on the bonding ability of these cements on primary dentin.