Effect of mechanical and air-particle cleansing protocols of provisional cement on immediate dentin sealing layer and subsequent adhesion of resin composite cement

摘要

Immediate dentin sealing (IDS) could avoid contamination of dentin from impression material and provisional cement but prior to final cementation of indirect restorations, removal of the provisional cement may damage the IDS. The objectives of this study were to investigate the effect of mechanical and air-particle cleansing protocols of provisional cement on IDS layer and subsequent adhesion of resin composite cement. The cuspal dentin surfaces of human third molars (N=21, n(quadrant)=84) were exposed by a low-speed diamond saw under water cooling and conditioned with an adhesive system based on the three-step etch and rinse technique (OptiBond FL). Provisional cement (Freegenol) was applied on each specimen. They were then randomly divided into six subgroups where the provisional cement was removed either by (1) air-borne particle abrasion with 50-mu m Al2O3 particles at 2bar (AL2), (2) air-borne particle abrasion with 50-mu m Al2O3 particles at 3.5bar (AL3.5), (3) air-borne particle abrasion with 30-mu m SiO2 particles at 2bar (SL2), (4) air-borne particle abrasion with 30-mu m SiO2 particles at 3.5bar (SL3.5), (5) prophylaxy paste (Cleanic) (PP) or (6) pumice-water slurry (PW) at 1500rpm for 15s. The dentin surface on each tooth was assigned to four quadrants and each quadrant received the cleansing methods in a clockwise sequence. The non-contaminated and non-cleansed teeth acted as the control (C). Two separate teeth, contaminated and cleansed according to six cleansing protocols, were allocated for scanning electron microscopy (SEM) analysis (x2000). The dentin surfaces in each quadrant received resin composite luting cement (Variolink II, Ivoclar Vivadent) incrementally in a polyethylene mould (diameter: 1mm(2); height: 4mm) and photopolymerized. The specimens were stored in distilled water for 24h at 37 degrees C until the testing procedures and then shear force was applied to the adhesive interface until failure occurred in a universal testing machine (0.5mm/min). Microshear bond (mu SBS) was calculated by dividing the maximum load (N) by the bonding surface area of the resin cement. Failure types were analysed using optical microscope and SEM. Data (MPa) were analysed using one-way ANOVA (alpha=0.05). Two-parameter Weibull distribution values including the Weibull modulus, scale (m) and shape ((0)), values were calculated. Mean mu SBS results (MPa) showed a significant difference between the experimental groups (p=0.011) and were in a descending order as follows: C (8 +/- 2.3)(a)