Effects Of Lateral Canals Filling On Apical Microleakage In Single Canal Premolar After Root Canal Treatment

Introduction: Root canal filling is the final stage of root canal treatment.The purpose is to provide a liquid-tight seal for the prepared root canal to prevent reinfection caused by microleakage.There is a lot of literature showing that incomplete root canal filling is the main cause of root canal treatment failure.This is mainly due to the complex anatomical structure of the apical region,which formed lateral canals,apical ramifications and apical furcations.These areas is a difficult point for root canal filling.Many literatures have studied the effects of root canal filling methods or root canal sealers on lateral root canal filling.However,there has been much controversy about the impact of lateral root canal filling on the success of root canal treatment.Therefore,this experiment studied the relationship between lateral root canal filling and apical microleakage,and studied the incidence and filling rate of collateral root canals.There are many literatures studying the effects of root canal obturation methods or root canal sealers on the filling of lateral canals.What remains to be determined is the impact of lateral canals obturation on the success of root canal treatment.However,the impact of collateral root canal filling on the success of root canal therapy has been controversial.Therefore,this experiment studied the relationship between collateral root canal filling and apical microleakage,and analyzed the incidence and filling rate of collateral root canals.Methods:The root canal preparation and root canal filling were performed on single canal premolars.The best root canal filling method and root canal sealer were selected by dye penetration and glucose penetration.Then,the lateral root canals were scanned and analyzed the incidence and filling rate with high-precision Micro CT.Next,a scanning electron microscope was used to check the filling quality of the main root canal.Finally,the effects of lateral root canal filling on apical microleakage were examined using staining and glucose quantification.Results:The Warm vertical condensation and iRoot SP sealer had the best apical sealability by dye penetration and glucose penetration.We used Warm vertical condensation with iRoot SP sealer to fill the root canal,and then scanned the root apex of the tooth 3mm after root canal treatment by a high-precision Micro CT.We found the 30 apical root segments were identified a total of 21 samples with lateral canals,including 11 unfilled lateral canals and 10 filled lateral canals.Our results indicated that the incidence of lateral root canals in a single canal premolar is 70.00% and the filling rate is 47.62%.SEM data indicated that the apical regions of the three experimental groups were well closed.There were similar gaps between the filling material and the root canal wall at the apical of the main root canal in three experiment groups.These proved that the filling of the main root canals in three experimental groups were similar,so the influence of the microleakage difference produced by the main root canals on the lateral canals was excluded.The dye penetration results showed that the apex of each group had different degrees of microleakage.The lowest rate of apical micro-leakage was seen in no lateral canals groups(2.481±0.074 mm)and the highest apical micro-leakage was related to lateral canals unfilled groups(2.526±0.037 mm).The lateral canals filled group was 2.512 ± 0.032 mm.However,there were no statistically significant differences in apical microleakage rates in the 3 experimental groups(P>0.05).In the glucose penetration,there was a tendency of increase in leakage in all experimental groups from the 1st day to the end of experimental period(P<0.05).In the no lateral canals groups and lateral canals filled groups,there were a statistically significant increase in the amount of microleakage from the 4th day compared with the previous day(P<0.05).And in the lateral canals unfilled groups,the increase of microleakage from the 6th day was statistically different from the previous day(P<0.05).But,the groups were compared with each other,no significant differences were found among the 3 experimental groups at experimental period(P>0.05).Conclusions: For single canal premolars,the incidence of lateral canals is high and the filling rate is relatively low.While the 2 apical microleakage detection methods proved that there is no necessary relationship between the lateral canals filling and apical microleakage.