Long-term tensile bond strength of differently cemented nanocomposite CAD/CAM crowns on dentin abutment

To test the tensile bond strength of luted composite computer aided design/computer aided manufacturing (CAD/CAM) crowns after use of different adhesive systems combined with different resin composite cements on dentin abutments.

Human molars (n=200) were embedded in acrylic resin, prepared in a standardized manner and divided into 20 groups (n=10). The crowns were treated as follows: (i) Monobond Plus/Heliobond (MH), (ii) Ambarino P60 (AM), (iii) Visio.link (VL), (iv) VP connect (VP), and (v) non-treated as control groups (CG) and luted with Variolink II (VAR) or Clearfil SA Cement (CSA). Tensile bond strength (TBS) was measured initially (24h water, 37°C) and after aging (5000 thermal cycles, 5/55°C). The failure types were evaluated after debonding. TBS values were analyzed using three-way and one-way ANOVA, followed by post hoc Scheffé-test, and two-sample Student's t-tests.

Among VAR and after aging, CG presented significantly higher TBS (p=0.007) than groups treated with MH, AM and VP. Other groups showed no impact of pre-treatment. A decrease of TBS values after thermal aging was observed within CSA: CG (p=0.002), MH (p<0.001), VL (p<0.001), AM (p=0.002), VP (p<0.001) and within VAR: MH (p=0.002) and AM (p=0.014). Groups cemented with VAR showed significantly higher TBS then groups cemented with CSA: non-aged groups: CG (p<0.001), and after thermal aging: CG (p=0.003), MH (p<0.001), VL (p=0.005), VP (p=0.010).

According to the study results nano-composite CAD/CAM crowns should be cemented with VAR. Pre-treatment is not necessary if the tested resin composite cements are used.