Experimental Study On Direct Pulp Capping Of Rat Molars By Low Lever Laser Combined With Dycal

Objective:The low-lever laser therapy（LLLT）combined with Dycal after direct pulp capping in rats molars,The inflammatory changes and restorative dentin of the pulp were observed in different time and space.The expressions of interleukin-1β（IL-1β）,transient potential receptor channel 1（TRPA1）,substance P（SP）and alkaline phosphatase（ALP）in the pulp were measured.To explore the mechanism of LLLT combined with Dycal for pulp vigor preservation and pulp wound healing,and to provide a certain experimental basis for clinical practice.Methods:64 SD adult male rats were randomly divided into 4 groups（n=16）:Normal control group（NC）、Low-Level Laser Therapy+Dycal group（LLLT+Dy）、Low Level Laser Therapy group（LLLT）and Dycal group（Dy）.The first molars of the left maxillary and mandibular of the rats mechanical wear pulp after direct pulp capping,postoperative 3^rd,7^th,14^thand 28^thdays take the experimental teeth specimens,the embedding,slice,By HE staining and IL-1β、TRPA1、SP and ALP expression in pulp tisssue was measured with immunohistochemical staining.and the mean optical density（MOD）was measured by Image pro plus6.0,and statistical analysis.Result:1.HE staining results:differences were found in intramedullary inflammation under the medullary foramen in the three experimental groups.There were no significant differences in intramedullary inflammation and dentin repair in the three experimental groups on the 3rd and 7th day after surgery（P>0.05）,but there were significant differences on the 14th and 28th day after surgery（P<0.05）.In terms of the changes of inflammation,the changes of inflammation in LLLT group,DY group and LLLT+DY group were decreased successively.There were significant differences in inflammatory changes between LLLT group and LLLT+DY group on the 14th and 28th day after surgery（P<0.0167）.The formation of restorative dentine Bridges depends on the situation.On the 14th day after surgery,the formation of dentine Bridges in LLLT+DY group was significantly different from that in LLLT group and DY group（P<0.0167）,while on the 28th day,the dentine Bridges in LLLT+DY group were significantly better than that in LLLT group（P<0.0167）.2.Immunohistochemical results of IL-1β、TRPA1:On the 28^thday IL-1βpositive expression MOD value LLLT<Dy<LLLT+Dy group,while LLLT<LLLT+Dy group had positive MOD value of TRPA1,and there were significant differences（P<0.05）.By univariate analysis of two-factor variance,the positive MOD value of IL-1β、TRPA1 was firstly increased and then decreased.Except for 28^thdays,the expression of them in all the experimental groups was statistically different from that in the NC group（P<0.05）;The 3^rdday postoperative,the positive MOD value of IL-1β、TRPA1 was no signficant difference LLLT and LLLT+Dy group（P<0.05）,on the 7^thday postoperative IL-1β、TRPA1 positive MOD value was significant difference in LLLT+Dy<LLLT<Dy group,on the 14^thday,they were significant difference in LLLTand Dy group（P<0.05）,On the 28^thday IL-1βpositive expression MOD value LLLT<Dy<LLLT+Dy group,while LLLT<LLLT+Dy group had positive MOD value of TRPA1,and there were significant differences（P<0.05）.3.Immunohistochemical results of SP、ALP expression:There was a significant difference in the expression of SP、ALP on the 7th day after surgery,and the expression of SP reached the peak on the 14th day.The expression of ALP in LLLT+Dy group and LLLT group reached the peak on the 7th day.The expression of SP LLLT+Dy>LLLT>NC group on the 14^thday（P<0.05）.The expression of SP、ALP decreased gradually and approached the normal level with the formation of prosthetic dentin on the 28^thday.The expression of ALP in the three groups was higher than that in the control group on the 3rd,7th and14th days after operation（P<0.05）.The expression level of SP、ALP in LLLT+DY group was higher than that in Dy group on the 7th day（P<0.05）,but had no statistical significance with LLLT group（P>0.05）,while the expression level of ALP in LLLT+DY group was higher than that in LLLT group on the 14th day（P<0.05）,while the expression level of ALP in LLLT+Dy、Dy group was higher than that in LLLT group（P<0.05）.Conclusion1.LLLT may by reducing IL-1 beta TRPA1 was expressing reduce inflammation,to create a more suitable microenvironment for dental pulp repair.2.LLLT may increase SP expression to accelerate the formation of blood vessels,increasing the dentin bridge.3.LLLT+Dycal in pulp damage healing regeneration programs can significantly reduce inflammation,promote healing,accelerate the reparative dentine formation,is a kind of good direct pulp capping method.4.LLLT cannot be used as a pulp capping agent for living pulp preservation.