Histological evaluation of the effectiveness of increased apical enlargement for cleaning the apical third of curved canals

Fornari VJ, Silva‐Sousa YTC, Vanni JR, Pécora JD, Versiani MA, Sousa‐Neto MD. Histological evaluation of the effectiveness of increased apical enlargement for cleaning the apical third of curved canals. International Endodontic Journal, 43, 988–994, 2010. Objective To evaluate the influence of apical size on cleaning of the apical third of curved canals prepared with rotary instruments. Methodology Forty‐four mesiobuccal canals of maxillary molars teeth were instrumented to different apical sizes (30, 0.02; 35, 0.02; 40, 0.02; 45, 0.02) using a crown‐down technique. After canal preparation, the apical thirds of the roots were submitted to histological processing and examination. The specimens were analysed at 40× magnification and the images were submitted to morphometric analysis with an integration grid to evaluate the percentage of debris and uninstrumented root canal walls. The action of the instruments on the root canal walls was assessed based on the surface regularity, abrupt change on the continuity of root canal walls, and partial or total pre‐dentine removal. The results were statistically compared using one‐way anova with post hoc Tukey test. Pearson’s correlation was performed to identify potential correlations between values. Results The percentage of uninstrumented root canal dentine was higher when apical enlargement was performed with instruments 30, 0.02 taper (55.64 ± 4.62%) and 35, 0.02 taper (49.03 ± 5.70%) than with instruments 40, 0.02 taper (38.08 ± 10.44%) and 45, 0.02 taper (32.65 ± 8.51%) (P