The Effect Of Phenolic Resin Sealing Root Canal Wall On Apical Microleakage

Objective: Microleakage is an important factor affecting long-term results of root canal therapy.At present,the studies on microleakage are more concentrated in the apex and crown of root canal,arguing that apical microleakage is the major cause for failed root canal therapy.However,the ideal three-dimensional root canal obturating is not only reflected in the apical leakage and crown leakage,but also in the microleakage of root canal wall.It can reduce the permeability and lower the microleakage of canal wall after the sealing with phenolic resin.This experiment explores whether the sealing measures for root canal wall with phenolic resin impacts on apical microleakage to provide theoretic basis for improveing the long-term curative effects of root canal therapy.Methods:Collect 44 premolars with single root extracted in the orthodontic treatment of patients from the oral surgery department of The Second Hospital of Hebei Medical University,flush the blood on the root surface under running water until the water is neutral,and use ultrasonic scaler to remove dental calculus on the root surface.Extracted teeth are randomly divided into four groups: A(20),B(20),C(2)and D(2).The crowns of all the extracted teeth are amputated with high speed handpiece from cemento-enamel junction,with root canal orifice exposed.Select K-file and Gates-Glidden bur for root canal cleaning and shaping,use EDTA,NaClO,H2O2 to alternatively flush and ultrasonic concuss when cleaning and shaping,and keep the apical foramen patency.Group A is set as the experimental group,with phenolic resin sealing the root canal wall.Group B is set as the control group,with no phenolic resin treatment on the root canal wall.Group C and D are set as positive and negative control groups,which with phenolic resin sealing the root canal wall.The root canals of extracted teeth in group A,B and D are all obturated with gutta-percha and zinc oxide eugenol sealer,adopting the cold lateral condensation of gutta-percha technique.Group C is set as the positive control group with gutta-percha obturated only,root canal sealer(zinc oxide eugenol sealer)is not used,and other operations are the same as those of group A and group D.7 days later,after the sealer is fully solidified,in the groups of A,B and C,except for the root tip of 2mm of the extracted teeth,the rest of root surface area is evenly coated with two layers of red nail,and ensure that all area is covered and outer surface of the root is completely sealed.Group D is set as the negative control group,and the whole root surface including the apical foramen is fully coated with two layers of red nail.All extracted teeth from the four groups are immersed in the EP tubes with methylene blue dye solution,6 days later,take out all the teeth for discoloring treatment.On spry cooling condition,along the median line of long axis,use high-speed emery bur to grind out a shallow trough of 1mm on the mesial and distal surface,not through the pulp cavity,split the extracted root into halves along the shallow trough with osteotome.Observe the dyeing condition of the longitudinal section of root canal under the stereomicroscope,measure the penetration distance from the anatomical apical foramen to the crown(accurate to 0.01 mm),measure 3 times,and take the mean value of the double-sided sections as the final result and record.Data was analysed with SPSS 22.0 statistical analysis software,and the data expressed as indicates the comparisons of the mean values of the two groups are in line with t test,with an inspection level α=0.05Results:1 Morphology Morphological observation: The methylene blue in the experimental group permeates through apical foramen vertically to 1/3 of apical area,and root canal wall is not permeated diffusely from the lateral.The methylene blue in the control group also permeates 1/3 of apical area through apical foramen,but root canal wall is diffusely permeated from the lateral.2 The mean values of the leakages of the experimental group and control group are 2.5340 mm and 2.7490 mm respectively,and there is no significant difference of apical microleakage levels(P > 0.05)between the 2 groups.It doesn’t aggravate or alleviate the microleakage level after the sealing treatment on root canal wall with phenolic resin.Conclusions:1 It has no effect on apical microleakage after the sealing treatment on root canal wall with phenolic resin,and it doesn’t aggravate or alleviate the microleakage level.2 It can be considered that the phenolic resin sealing root canal wall as the treatment process of the intermediary between the root canal preparation and the root canal filling for an operating procedure,which can reduce the maximum of the total micro leakage of the root canal therapy.2 The sealing treatment on root canal wall with phenolic resin can be recommended as an operating step between root canal cleaning and shaping and root canal obturating during root canal therapy to reduce the overall microleakage level of root canal system ulteriorly.