RESUMO
AIM: To study the effect of different apical shapes in prepared simulated root canals on the application of a commercially prepared calcium hydroxide paste by a syringe or lentulo spiral. METHODOLOGY: Three different types of root canal preparation were performed in 90 simulated canals: group A to an apical size 20 and a 0.10 taper using hand and rotary instruments, group B to an apical size 30 and a 0.08 taper using GT rotary instruments and group C to an apical size 40 and a 0.04 taper using ProFile 0.04 instruments. The insertion of calcium hydroxide [Ca(OH)2] paste was accomplished using either a lentulo spiral or a syringe. After 1 week of simulated fluid pressure applied to the apical end of the canal using physiological saline solution, the solution was evaluated for released Ca(OH)2. The specimens were weighed initially, after preparation, after insertion of Ca(OH)2 paste, after temporization with Cavit and after 1 week of simulated fluid pressure. Digital radiographs of the filled canals were taken and canal areas in mm2, gray values of the Ca(OH)2 dressings, total area of voids in mm2, as well as location of voids in the apical, middle or coronal thirds of the root canals were measured. Analyses of variance, with Scheffe's post-hoc tests, as well as chi-square tests were performed. RESULTS: Canals in group C had significantly fewer (P < 0.01) radiographic voids than canals in groups A and B. Using a lentulo spiral resulted in significantly (P < 0.05) fewer voids compared with the injection technique. More voids were detected coronally compared with middle and apical root canal thirds (P < 0.05). CONCLUSIONS: Canal shape and method of application had an impact on the amount and radiodensity of calcium hydroxide dressings in simulated root canals. Canals prepared to an apical size 40 and a taper of 0.04 had the least number of voids; Ca(OH)2 was placed with significantly fewer voids using a lentulo spiral compared with the injection technique.