Impact of Various Drying Protocols on the Bond Strength of AH Plus Sealer to Dentin Walls Using the Vertical Condensation Technique: An In Vitro Study

Background Moisture control within the root canal prior to obturation is a key factor influencing the bond strength of sealers to dentinal walls. Traditionally, paper points have been used to dry root canals, however, this method may not completely eliminate residual moisture, potentially compromising the adhesion of sealers. Recently, the use of chemical drying agents such as ethanol and isopropanol has been suggested to improve dentin dehydration and enhance sealer penetration into dentinal tubules. Objectives The main objective of this study is to evaluate the effects of isopropanol alcohol, ethanol alcohol, and paper points as drying protocols on the bond strength of root canal obturation with gutta-percha and AH Plus sealer, using the warm vertical condensation (WVC) technique, to the canal dentinal walls. Materials and methods Thirty single-rooted human permanent teeth were decoronated to a length of 15 mm. The roots were randomly divided into three groups (n = 10 for each group) according to the drying protocol: (Group 1 (G1): paper points, Group 2 (G2): 70% isopropanol, and Group 3 (G3): 95% ethanol). Thirty roots were prepared using ProTaper Universal rotary instruments. In G1, the canals were blot dried with paper points until the last one appeared dry; in G2, the canals were dried with paper points followed by dehydration with 70% isopropanol; and in G3, the canals were dried with paper points followed by dehydration with 95% ethanol. After drying, the canals were obturated with AH Plus sealer and gutta-percha using the WVC technique. Then, each root was sectioned into three slices (coronal, middle, and apical thirds) with 2-mm-thick sections using a diamond disc. The push-out strength between the sealer and dentin wall was tested for each slice using a universal testing machine at a crosshead speed of 1 mm/min, and failure modes were examined under a stereomicroscope at 40× magnification. The data were statistically analysed using one-way analysis of variance (ANOVA) and Bonferroni tests. The significance level was set at 0.05. Results The three experimental groups demonstrated significant differences (p < 0.05). G2 exhibited significantly higher bond strength than G3 (p < 0.05). In contrast, G1 showed the lowest push-out strength. Regarding failure modes, statistically significant differences were observed among the groups (p < 0.05). At different root levels, significant differences were also noted (p < 0.05). Specifically, in the coronal third, the majority of failures (80%) in G2 and G3 were cohesive failures, whereas G1 predominantly exhibited mixed failures, followed by a lower frequency of adhesive failures. Conclusions Drying with 70% isopropanol and 95% ethanol enhanced the bond strength between AH Plus sealer and dentinal tubules more effectively than the conventional paper point drying method when using the WVC technique, with 70% isopropanol being superior to the other studied groups.