Effect of different mechanical cleansing protocols of dentin for recementation procedures on micro-shear bond strength of conventional and self-adhesive resin cements

Service life of debonded indirect dental restorations could be prolonged by recementation. This process requires removal of cement remnants from dentin. This study evaluated the effect of different mechanical cleansing protocols of dentin for recementation procedures on micro-shear bond strength (μSBS) of conventional and self-adhesive resin cements. The labial surfaces mandibular incisors ( N=200) were ground with a low speed saw to expose the coronal dentin. The teeth were randomly divided into two subgroups ( n : 100 per group) and received either (a) conventional (Panavia F 2.0, Kuraray, PAN) or (b) self-adhesive (Clearfil SA, Kuraray, CSA) resin cement. Resin cements were condensed into polyethylene molds incrementally and photo polymerized using an LED polymerization unit. Specimens were stored in distilled water at 37 °C for 24 h and subjected to μSBS (0.5 mm/min). Resin cement remnants on bonded dentin surfaces were removed using by (a) composite finishing bur (cb), (b) tungsten carbide bur (ob), (c) ultrasonic scaler tip (sc) or (d) pumice-water slurry (pw). Non-cleaned teeth acted as the control group (cn) ( n : 20 per subgroup). After cleaning, the same cement type was rebonded simulating clinical recementation. Failure types were analyzed using optical microscope and Scanning Electron Microscope (SEM). Data (MPa) were analyzed using Wilcoxon Signed Ranks, Mann-Whitney U and Bonferroni tests ( α=0.05). Overall, CSA (6.42±2.96) showed significantly lower results than that of PAN cement (7.88±3.49) ( p<0.05). All cleansing protocols (4.29±2.17 to 5.82±2.5) showed significantly lower results than that of the control group (9.84±4.88) for PAN cement. For CSA cement, all cleansing protocols presented non-significant results (4.25±2.74 to 6.44±2.4 MPa) compared to control group ( p>0.05) expect cb method (3.42±1.47) ( p <0.05). Remnants of cements were detected on dentin surfaces in all groups at varying degrees. SEM showed that while using pumice-water slurry was the least effective for PAN, tungsten carbide bur was the most effective for both cements. All other methods showed similar cleansing efficacy. None of the cleansing protocols yielded to complete removal of resin cement rest on dentin upon recementation for both cements tested.