The Various Methods Of Removing Calcium Hydroxide From The Root Canal And Its Residues Effects On The Apical Sealing

OBJECTIVE:The conventional and effective treatment for endodontic and periapical diseases is root canal therapy,and root canal disinfection is an important step in root canal therapy.Calcium hydroxide（CH）is the main preparation recommended by the clinic.According to the different excipient is divided into water-based,viscous,oil-soluble calcium hydroxide.Apical sealing is the key to the success of root canal treatment.Clinical trials have confirmed that different methods cannot completely remove calcium hydroxide preparations in the root canal,and some studies have reported that calcium hydroxide remaining in the root canal has adverse effects on apical sealing.In this experiment,four mechanical irrigation methods were used to remove two types of calcium hydroxide,and the clearance rates of the four irrigation methods were compared.The apical sealing was also investigated in terms of the influence of residual calcium hydroxide and filling techniques.METHODS:Part Ⅰ:64 complete mandibular first premolars were randomly divided into two groups（n=32 each）after crown cutting and root canal preparation.Group A was injected with water-soluble calcium hydroxide,and group B was injected with oil-soluble calcium hydroxide.After two weeks of drug sealing,both group A and B were randomly split into four groups（n=8）,each with its own irrigation technique:Group 1,a lateral opening syringe irrigation group;Group 2,an acoustic root canal irrigation group;Group 3,an ultrasonic root canal irrigation group;and Group 4,an Er:YAG laser irrigation group.Scanning the samples before and after calcium hydroxide removal with cone beam CT,the data was imported into Mimics software for three-dimensional reconstruction.The root canal was split into three parts:the superior root,the root and the apical segment,and the calcium hydroxide volume of each was determined.Before being taken away,the amount of calcium hydroxide was V₁,and after being taken away,it was V₂.The clearance rate was（V₁-V₂）/V₁multiplied by 100%.Statistical analyses were performed using a three-way ANOVA.Part Ⅱ:75 isolated mandibular premolars were collected,crowns were cut,and root canals were prepared.Randomly selecting 60 premolars,two groups were formed（n=30each）:group A was injected with water-soluble calcium hydroxide,group B with oil-soluble calcium hydroxide,and the remaining 15 premolars were used as a blank control group C.After 2 weeks of drug sealing,the calcium hydroxide in the root canals was removed by ultrasonic vibration washing in both groups.The teeth in groups A,B,and C were divided into groups 1,2,and 3,respectively,using three different root canal filling methods:i Root SP single tip method,hot dental glue vertical filling method,and cold dental glue lateral pressure filling method.Dye permeation technique was used to evaluate apical sealing.An electron microscope scanning was employed to observe the micromorphology of the junction between dentin and root canal sealant in each group.Two factor analysis of variance was used to calculate the permeation length.RESULTS:The two types of calcium hydroxide could not be completely removed by four irrigation methods.The clearance rate of water-soluble calcium hydroxide was higher than that of oil-soluble calcium hydroxide（P<0.001）.Among the three root canal segments,the clearance rate of the apical segment was lower（P<0.05）.Er:YAG laser washing group had the highest removal efficiency of two kinds of calcium hydroxide,which was significantly higher than the other three groups,especially in the apical 1/3（P<0.05）.The ultrasonic group had significant advantages compared with the acoustic wave washing group and the syringe washing group（P<0.05）.The clearance rate of the acoustic wave washing group was higher than that of the syringe washing group only in the middle part of the oiling calcium hydroxide root group（P<0.05）.The residual calcium hydroxide in the root canal and different root canal filling methods have an effect on the apical sealing of the root canal.And there is an interaction.As for the influence of residual calcium hydroxide in the root canal on apical sealing,water-soluble calcium hydroxide had statistical significance only in the hot gum group（P<0.001）for the unsealed drug group,and oil-soluble calcium hydroxide and unsealed drug group had statistical significance in i Root SP single tip method（P<0.05）and cold lateral pressure group（P<0.001）.The effect of three root filling methods on apical sealing:in the unsealed group,only the i Root SP single tip group and the cold tooth glue group were different（P<0.05）;The apical sealing of the two groups of calcium hydroxide,hot dental glue and cold lateral pressure were significantly different from that of i Root SP group（P<0.001,P<0.001）.CONCLUSIONS:In this paper,two types of calcium hydroxide were selected as root canal disinfectants,the efficiency of four removal methods was compared,and the three root canal filling methods were compared based on the apical sealing,and the following conclusions were drawn.1.The removal efficiency of oil-soluble calcium hydroxide is lower than water-soluble calcium hydroxide.2.The removal efficiency of calcium hydroxide by Er:YAG laser is higher than the other three removal methods.3.For calcium hydroxide in residual root canals,oil-soluble calcium hydroxide had less effect on apical sealing than water-soluble calcium hydroxide.4.The single tip method of i Root SP has better apical sealing than vertical filling with hot dental glue and lateral pressure filling with cold dental glue.