Effect of different periodontal ligament simulating materials on the incidence of dentinal cracks during root canal preparation

Background. The present study was undertaken to evaluate the incidence of dentinal cracks during root canal preparation with different periodontal ligament simulating materials in vitro. Methods. Seventy freshly extracted human mandibular first premolars were selected and divided into 7 groups in terms of simulating material: group 1: polyether impression material; group 2: polyvinyl acetate adhesive; group 3: polyvinyl siloxane impression material; group 4: cyanoacrylate adhesive; group 5: epoxy resin adhesive; group 6: positive control, without any periodontal ligament simulation; and group 7: negative control, where neither a periodontal ligament simulating material was used nor canal preparation was carried out. Root canal preparation was carried out in all the groups followed by sectioning of roots at 3 mm, 6 mm and 9 mm. The sections were evaluated under a stereomicroscope at ×2.5 for the presence or absence of cracks. Chi-squared test was used to compare the appearance of defective roots between the different experimental groups. Results. The least number of cracks were found in the negative control group, followed by group 1 where polyether impression material was used for periodontal ligament simulation. The difference was significant with a P-value of 0.002 for coronal sections. Conclusion. Under the limitation of the present study, polyether and polyvinyl siloxane (light body) can both be used for simulation of periodontal ligament.