The Ex Vivo Study Of Filling Curved Canals Of Posterior Teeth Using Different Methods

Purposes:The purpose of this ex vitro study was to compare the first depth of spreader penetration,filling time and apical sealing ability of different filling methods with different tapered gutta-percha master cones, using cold gutta-percha lateral condensation with nickel—titanium spreader in curved canals of posterior teeth,prepared by hand ProTaper, in order to approach the master cone gutta-percha which was to fit the curved canals of posterior teeth prepared by large tapered nickel—titanium instruments,in order to provide some experimental evidences for clinical use.Methods:Sixty-six freshly extracted human posterior teeth with a single,curved canals according to Schneider's measurement method,were collected with normally getting the access to the pulp chamber and extracting dental pulp.All root samples were divided into five experimental groups of 11 teeth each(group1.0.06 tapered gutta-percha master cone 25^#,group2:0.04 tapered gutta-percha master cone 25^#,group3:0.04 tapered gutta-percha master cone 30^#,group4:0.06 tapered gutta-percha master cone 20^#,group5:0.02 tapered gutta-percha master cone 25^#)using cold gutta-percha lateral condensation,negative control group(AH-PLUS sealer)of 5 teeth and positive control(0.06 tapered gutta-percha master cone 25^#)of 6 teeth using warm vertical condensation.After removing the crown at enamelo-cemental junction and measuring working length,all teeth were prepared by hand ProTaper according to crown-down technique.The main apical file was F₂.The canals were filled by different methods,recording the first depth of nickel—titanium spreader penetration,filling time,and comparing the concentration of the apical microleakage of different days.Results:1.The average difference value of working length of those 66 root of posterior teeth ex vitro between ant-preparation and post-preparation was significantly smaller than reference standard 1.0mm (P＜0.05).And different groups were not obviously different(P＞0.05).2.The average difference values between working length of ant-preparation,post-preparation and the first depth of spreader penetration were not significantly different in ant-preparation and post-preparation(P＞0.05)but in experimental groups(P＜0.05).The difference values between working length of ant-preparation, post-preparation and the first depth of spreader penetration of group2,was significantly smaller than those of group1 and group3.The difference values between working length of ant-preparation,post-preparation and the first depth of spreader penetration of group5,was significantly smaller than those ofgroupl,group3 and group4.3.The filling time of different groups had significant difference(P＜0.05).The filling time of experimental groups were obviously longer than control groups,and the filling time of group6 was obviously shorter than group7.The filling time of group3 and group4 both were significantly shorter than group1,group2 and group5.The correlations between the difference values between working length of ant-preparation,post-preparation and the first depth of nickel—titanium spreader penetration and filling time had significant difference(P＜0.05).4.The apical microleakage of different days and different groups had significant difference(P＜0.05).The apical microleakage of group6 was obviously higher than other six groups(P＜0.05),and the other six groups had no significant difference(P＞0.05).Conclusions:1.When hand ProTaper was used to prepare curved canal,the working length of ant-preparation and post-preparation had no significant difference.2.Smaller tapered but same size master cone gutta-percha was more suitable for curved canals prepared by hand ProTaper using cold gutta-percha lateral condensation.3.The filling time of chosing one degree smaller tapered or size master cone gutta-percha was shorter using cold gutta-percha lateral condensation.The first depth of nickel—titanium spreader penetration may influence the filling time of curved canal.4.The apical sealing ability of curved canals filled with different tapered master cone gutta-percha,had no significant difference in short time(30 days).In summary,it was better to select smaller tapered or size master cone gutta-percha to fill curved posterior teeth canals prepared by hand ProTaper using cold gutta-percha lateral condensation.But they had some advantages and disadvantages at the the first depth of spreader penetration and filling time.It could be got a deeper choice by combining clinical conditions.