Abstract
Optical microscopy and morphometric analysis were used in this study to evaluate, in vitro, the cleaning of the apical region in root canals with mild or moderate curvatures subjected to biomechanical preparation with a rotary system, as well as to assess the amount of extruded material to the periapical area. Lateral incisors (n = 32), 16 with curvature angles smaller or equal to 10º (GI) and 16 between 11º and 25º angles (GII) were submitted to Hero 642 rotary instrumentation with different surgical diameters: (A) 30.02 and (B) 45.02. Irrigation was performed at each change of instrument with 5 mL of ultrapure Milli-Q water and the extruded material through the apical foramen was collected. Root cross-sections were subjected to histological analysis by optical microscopy (×40) and the images were evaluated morphometrically using the Image Tool software. Quantification of the extruded material was performed by weighing after liquid evaporation. ANOVA showed no statistically significant differences (p>0.05) among the groups with respect to the procedures used to clean the apical region. Considering the amount of extruded material, the Tukey's HSD showed that canals with mild curvature prepared with the 45.02 surgical diameter showed significantly higher values (p<0.05) that those of the other groups, which were similar between themselves (p>0.05). In conclusion, the effect of cleaning the apical region did not differ in the groups, considering root curvature and the surgical diameter of instruments used for apical preparation. The amount of extruded material was greater in canals with mild curvature that were prepared with the 45.02 surgical instrument diameter.
Highlights
The mechanical action of endodontic instruments during biomechanical preparation combined with the physicochemical properties of irrigation solutions is aimed at cleaning and disinfecting toot canals and favor periapical repair [1]
Root canals with mild curvature prepared with the 45.02 instrument to the full working length (WL) showed the highest values for extruded material to the periapical region (0.87±0.22)
Fornari et al [7] reported that better cleaning is obtained in severely curved roots when final instruments of greater diameter are used, but this greater enlargement and apical patency may result in material extrusion to the periapical region causing persistent inflammation and postoperative pain [8]
Summary
The mechanical action of endodontic instruments during biomechanical preparation combined with the physicochemical properties of irrigation solutions is aimed at cleaning and disinfecting toot canals and favor periapical repair [1]. During this procedure, rests of excised dentin not removed by the irrigation/aspiration processes are kept inside the root canal, adhered to the walls and forming an amorphous structure called smear layer or, at the canal lumen in areas not reached by the endodontic instruments and/or irrigation solution forming debris that remain together with pulp remnants. The amount of material extrusion to the periapex varies according to the instrumentation and irrigation techniques, the apical patency and root curvature [9,10]
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