The effect of different access cavity designs on the removal of calcium hydroxide from root canals

Aim: The aim of this study is to investigate the effect of different access cavity designs and irrigation solutions on the removal of calcium hydroxide from root canals. Materials and Methods: A total of 84 human mandibular molars were selected for this study. The samples were divided into three main groups, each consisting of 28 teeth, according to the cavity designs to be prepared. Calcium hydroxide was placed into the root canals of the teeth after cavity preparation and root canal shaping. All samples were kept in an incubator at 37°C with 100% humidity for one week. To allow imaging under the confocal laser scanning microscope, calcium hydroxide was mixed with rhodamine B dye. The samples were then divided into 4 subgroups according to the irrigation solutions used to remove calcium hydroxide. After the removal process, apical 3 mm sections were taken, and images of these sections were obtained using a confocal laser microscope. The images were analyzed with ImageJ software. The obtained data were analyzed using two-way anova and tukey post hoc tests, keeping the significance level at p<0.05. Results: A significant difference was found in the cleanliness of the canal walls with respect to access cavity designs. The TGK group showed statistically significantly cleaner canal walls compared to the NGK group (p<0.05). Regarding the irrigation solution, no significant difference was observed between 70% ethanol and 0.2% chitosan in terms of cleaning the canal wall (p>0.05 Also, no significant difference was observed between 0.2% chitosan and 17% EDTA (p>0.05). It was observed that 70% ethanol removed calcium hydroxide from the canal walls at a statistically significant level compared to 17% EDTA (p<0.05). No significant difference was found in the depth of cleaned tubules between the access cavity designs (p>0.05). 70% ethanol showed statistically significantly deeper tubule cleaning compared to 0.2% chitosan and 17% EDTA (p<0.05). 0.2% chitosan was also statistically significantly more effective than 17% EDTA in cleaning deeper tubules (p<0.05). When maximum penetration depth and area of calcium hydroxide were analyzed, no significant differences were found between 70% ethanol, 0.2% chitosan, and 17% EDTA (p>0.05). The GGK group exhibited statistically significantly greater penetration area compared to the other cavity designs (p<0.05). Both GGK and NGK groups showed statistically significantly greater penetration depth than the TGK group (p<0.05). Conclusion: Minimal invasive cavity designs are recommended to prevent tooth fractures. However, these cavity designs may compromise root canal cleaning. Ethanol and chitosan may serve as alternatives to EDTA for removing calcium hydroxide. Keywords: Calcium hydroxide, Chitosan, Confocal laser microscope, Ninja cavity, Truss cavity