Sucrose Irrigants Combined With Sodium Hypochlorite On Removal Effect Of Calcium Hydroxide Paste And Effect Of Bacterial Colonization In Root Canals

Background:Thoroughly eliminating the infectious agents is the principal purpose of the root canal therapy.And the mechanical instrument and chemotherapeutic procedures are the key to achieving this goal.Therefore,it is important to make good use of the disinfectant agents and chemotherapeutic irrigants in root canals.At present,calcium hydroxide[Ca（OH）2]has become one of the most commonly used root canal disinfection agents as its antimicrobial property,biocompatibility and the ability to induce hard tissue formation.But it has been reported that,the residual calcium hydroxide in root canals can reduce the sealing capability of the root canal sealers and affect the success rate of root canal treatment.Therefore,it is an urgent problem for clinicians to thoroughly remove calcium hydroxide after root canal disinfection.Sucrose is the main component of the canteen.It is a kind of disaccharide,which is soluble in water and non-toxic.It has been extensively used in chemical field for the reason that it can dissolve Ca（OH）₂.Therefore,it is conjecturable that the use of sucrose solution in clinical field may promote the removal of calcium hydroxide in the root canals,which will have good perspectives.This job intended to evaluate the efficacy of Ca（OH）₂ removal by using ultrasonically activated irrigation with sucrose solution and sodium hypochlorite（NaOCl）,and to evaluate the effect of these irrigants on bacterial colonization in root canals for providing data support in the application of clinical field.Objective:To evaluate the efficacy of Ca（OH）₂ removal when using ultrasoni cally activated irrigation combined with sucrose solution and NaOCl and to evaluate the effect of irrigantion agents on bacterial colonizati on in root canals.Method:1.Ca（OH）₂ powder was dissolved in deionized water.The solubility of Ca（OH）₂solution was observed by naked eye.PH-meter was used to measure the variation of pH when added the different mass concentration and varing amounts of sucrose solution into the Ca（OH）₂ solution.2.After collecting 30 single-rooted premolars extracted for orthodontic treatment,the standardized in vitro dental models were prepared.All samples were randomly divided into 3 groups（n=10）and were irrigated with ultrasonically activated irrigation:NaOCl+sucrose solution group,NaOCl+deionized water+EDTA group and negative control group.Dental radiography,dental operating microscope and SEM were used to observe the effect of removing Ca（OH）₂in the coronal third,middle third,and apical third of root canals in each group.3.After collecting 12 single-rooted premolars extracted for orthodontic treatment,the standardized in vitro dental models and the flake dentin models were prepared.All the root of samples were divided into coronal third,middle third and apical third.They were randomly divided into 4groups（n=3）and were irrigated with ultrasonically activated irrigation after a week:NaOCl+sucrose solution EDTA group,NaOCl+deionized water+EDTA group,sucrose solution+EDTA group,negative control group.Each group contained coronal third,middle third,apical third of the three.SEM was used to observating the effect of removing Ca（OH）₂in each group.4.After collecting 16 fresh single-rooted premolars extracted for orthodontic treatment,the standardized in vitro dental models and the E.faecalis infected models were established.The division of 4 groups is as above（n=4）and were irrigated with ultrasonically activated irrigation.CLSM was used to observe the depth distribution and calculate the proportion of dead bacteria to total bacteria in coronal third,middle third and apical third.Results:1.The pH of Ca（OH）₂solution was decreased as the added amounts of sucrose solution increased.When added same amounts of sucrose solution with different mass concentration,300g/L sucrose solution can observably decreased the pH of Ca（OH）₂solution,the minimum of its pH was 12.07.2.Both NaOCl+sucrose solution+EDTA group and NaOCl+deionized+EDTA group removed large amounts of Ca（OH）₂in the observation of the dental radiography and dental therapy microscope.In the results of the SEM,compared with the negative control group,both the NaOCl+sucrose solution+EDTA group and NaOCl+deionized water+EDTA group can’t completely remove the Ca（OH）₂ in all thirds of root canals（P<0.05）.In the coronal third,the effect of removing Ca（OH）₂ in NaOCl+sucrose solution+EDTA group was cleaner than NaOCl+deionized water+EDTA group,however,there was no statistical difference between the two groups in the middle third and apical third（P>0.05）.3.In the results of the SEM observation,NaOCl+sucrose solution+EDTA group,NaOCl+deionized water+EDTA group and sucrose solution+EDTA group can’t completely remove the Ca（OH）₂ on the flake model in all thirds of root canals（P<0.05）,but there was no statistical difference between the three groups（P>0.05）.4.The depth proportion of dead bacteria to total bacteria in three experimental groups was all larger than that in negative control group（P<0.05）,but there was no statistical difference between the three groups（P>0.05）.Conclusions:1.Sucrose irrigants can increase its solubility.We can make use of this characteristic to assist in promoting the removal rate of Ca（OH）₂paste in root canals.2.In the coronal third,the effect of removing Ca（OH）₂in root canals by using sucrose irrigants combined with NaOCl and EDTA is better than that by using deionized water combined with NaOCl and EDTA.But any kind of irrigation agent combination can not remove the Ca（OH）₂paste both in root canals or on the flake dentine.3.There was no significant effect on the control of E.faecalis infection in root canals when using sucrose solution as one of the irrigants with ultrasonically activated irrigation.It can be used as a kind of root canal irrigation agent to assist removing the Ca（OH）₂paste in root canals.