The effect of cure mode of the adhesive and seating pressure technique on the microtensile bond strength of dual cure resin cements to for luting composite onlays

The aim of this study was to evaluate the effect of cure mode of the adhesive and seating pressure technique on the microtensile bond strength of dual cure resin cements to perfused dentin.Occlusal enamel of 32 extracted human third molars were removed using 180 grit SiC paper and smear layer on the mid coronal dentin was standardized using 600 SiC. Teeth were randomly divided into 2 groups according to the resin cement-adhesive combination (AdheSe-Variolink II, Ivoclar/Vivadent; Protect Bond-Clearfil Esthetic Cement, Kuraray). Each group was further subdivided into 4 groups according to the type of the curing mode of the adhesive (cured; uncured) and according to the seating pressure technique (40N/30 sec; 40 N/110 sec). Composite onleys (Filtek Z 250; 3M ESPE) 3mm in thickness and 9 mm in diameter were luted with the dual cure resin cements adhesive combinations to 15 cm/H2O perfused dentin. After storage in distilled water at 37oC for 24 h, each tooth was sectioned first mesio-distally into serial slabs then vestibulo-lingually using the low speed diamond saw under water lubrication in order to obtain 1x1mm composite-dentin sticks. Micro-tensile bond strengths were determined at a depth level with a remaining dentin thickness between 2 and 3 mm. Microtensile bond strength (MPa) was evaluated using Bencor Multi Testing device attached to a universal testing machine (Instron). Data were analyzed using Mann-Whitney-U test. Curing the adhesive, Clearfil Protect Bond in combination with Clearfil Esthetic Cement using the seating pressure technique (40 N/30 sec) showed significantly higher in bond strength than the uncured adhesive, Clearfil Protect Bond in combination with Clearfil Esthetic Cement using the seating pressure technique (40 N/ 30 sec) (p=0,003). Curing the adhesive, AdheSe in combination with Variolink II using the seating pressure technique (40 N/110 sec) showed significantly higher in bond strength than the uncured adhesive, AdheSe in combination with Variolink II using the seating pressure technique (40 N/110 sec) (p=0,03). Uncuring the adhesive, AdheSe in combination with Variolink II using the seating pressure technique (40 N/30 sec) showed significantly higher in bond strength than the uncured adhesive, Clearfil Protect Bond in combination with Clearfil Esthetic Cement using the seating pressure technique (40 N/ 30 sec)(p=0,005).Curing of the adhesive may improve the microtensile bond strength to dentin of Clearfil Esthetic Cement in combination with Protect Bond. The pressure technique (110 sec) may affect bonding of Variolink II to dentin when the adhesive (AdheSe) was cured.