Experimental Study Of The Pulsed Nd: YAG Laser In The Dental Ulcer Therapy

BackgroundDental ulcer is one of the common diseases of oral mucosa, the overall morbidity of dental ulcer disease is about 20% at the first place of oral mucosa diseases. The rate is only less than dental caries and periodontal disease it take the 3 place of all the oral disease. The WHO oral health standards are: teeth are clean ; no caries;no pain; gingival color is normal; no bleeding. Some research showed that the overall morbidity of oral diseaseis 74% in China.It contains :dental caries; periodontal;periodontal disease; gingivitis; dental ulcer. The etiological factors of dental ulcer are complicated, individual difference play a important role in it.Fortunately, the pulsed Nd:YAG laser was introduced in 1960. Studies have revealed that the laser had the abilitities of solidify and vaporize both the endepidermis and the inflammatory infiltration soft tissue. Because of the laser can be specificity merging by hemoglobin, fibroglia fibrils fibrinous degeneration , collogen chain shrinkage at the same time seal off the micrangium so by this way it can reduce bleed or not bleed . It also can active various kinds of enz; speed up the circulation of blood; etc. The laser promote the EC and FC regeneration shorten the healing time of the ulcer. Pulsed Nd:YAG laser can interfere the transport function of neurocyte cell membrane Na+/K+ pump,and effect the cell membrane permeability,and inhibit the conduction of the local nerve impulse.so, it get the favourable anesthesia effect,and make a lighter response after iateria, pain release obviously,most of the patients can accept.But these studies were more in vitro experiments in which irradiation parameters and experimental condition varied greatly and provided little information for in vivo application.Few investigation at present has been found on the safety and feasibility in clinical treatment.ObjectiveThis study is to obtain an effective energy by comparing the therapeutic efficacy of 4 different laser energy levels radiation on dental ulcer mucosa and thus to provide theoretical support for the dental ulcer therapy by the pulsed Nd:YAG laser. Establish experimental dental ulcer animal model similar to dental ulcer of mankind in SD rats to approach the 4 energy levels of the pulsed Nd:YAG laser was used to establish the relationship between energy parameters irradiation on dental ulcer mucosa. Their safety to oral mucosa, then the proper parameters may obtain and apply for dental ulcer therapy to evaluate the feasibility reliability and superiority in the healing of dental ulcer.Materials and methods1. 4 healthy SD rats were randomly selected as the control group. 58 healthy SD rats ( male, 180~220g) to perform dental ulcer model. 72 hours later, 4 modeling rats and 4 normal rats were randomly selected to test the oral mucosa by HE staining to conform whether the modeling was successful. Then 50 rats of successful modeling were divided into 5 groups( each group had 10 sample )to receive experimental treatment of radiation by laser with the energy level of 1.5 W 40 mJ,1.5 W 60 mJ,1.5 W 80 mJ,1.5 W 100 mJ; select one group with no treatment as the dental ulcer group . the 4 levels of the laser groups treat the rats 3 days (once per day). 24 hours later they 2 sampel of each group were sacrificed then harvested the oral mucosa in order to HE staining. The other 8 rats in each group to raise 8 more days.2. After established the rates model of dental ulcer,the modeling succeed SD rates were divided into groups,the laser group were treated by laser for 3 days(once per day).24 hours later they were sacrificed to test the SOD,MDA,NO,NOS in oral mucosa to verify the treatment effects of the pulsed Nd:YAG laser.3. 24 Sprague-Dawley rates were randomly assigned to the control group, dental ulcer control group, dental ulcer with pules Nd:YAG laser iatreusis group and drug treatment group . 8 normal rats in addition were selected randomly as the control group. The dental ulcer group with no treatment ; the laser group treat the rats 3 days (once per day) with the power of 1.5 W 80 mJ ; the drug group treat the rats 3 days with iodoglycerin (once per day). 24 hours later they were sacrificed to test the level of EGF,EGFR in oral mucosa.Results1. The average healing time of the ulcer group is (7.63±0.53),And the 1.5 W 40 mJ group is (5.13±0.83), the 1.5 W 60 mJ group is (4.88±0.64),the 1.5 W 80 mJ group is (4.75±0.71), the 1.5 W 100 mJ group is (5.50±1.20).There was not significant difference between the every laser groups ,which was significant difference compared to the ulcer group. The result of the experiment mainfest the laser groups of 1.5 W 40 mJ,60 mJ,80 mJ,100 mJ can promote the healing time compared to the ulcer group,and the time of 1.5 W 60 mJ ~ 80 mJ laser groups is the shortest.2. In the vivo experiment the result demonstrate that with the pules Nd:YAG laser energy level between 1.5 W 60 ~80 mJ the levels of NO,NOS degrade and the levels of SOD MDA could return to balance . Due to the pules Nd:YAG laser the inflammatory reaction and cell damage could be controlled . The production and eliminate of oxygen free radical in tissue could keep balance.3. In normal oral mucosa,immuno-staining of EGF was mainly localized in basal layer cells and prickle layer cells.The expression intensity of EGF was higher in normal oral mucosa than that in in ( P < 0. 05 ). While in normal oral mucosa,immuno-staining of EGFR was mainly localized in the endochylema and cell membrane of basal layer cells.In all samples,the expression in EGFR was significantly weak t between dental ulcer and normal mucosa was ( P < 0. 05 ).The expression in marginal part of the dental ulcer was weak ( P < 0. 05 ). Level of EGF and EGFR activity in 1.5 W 80mJ,drug groups was evident to higher than the ulcer group (p < 0.05 ) ; but the changes of EGF and EGFR activity was no significant difference at the healthy group.Conclusions1. The result showed that the healing time of 1.5 W 40 mJ,60 mJ,80 mJ,100 mJ laser radiation groups were less than the control group.The best therapeutic efficacy groups were the 1.5 W 60 mJ~ 80 mJ groups.our result confirmed that use the proper pulse energy of Nd:YAG lase can be effective to treat dental ulcer.2. 1.5 W 60 mJ~ 80 mJ of pulsed Nd :YAG laser irradiation on dental ulcer of rats were effective to promote dental ulcer healing, and it can to cause NO,NOS degrade and the levels of SOD MDA could return to balance Based on the above results, a preliminary parameters both safety and efficacy of the laser could be 1.5 W 80 mJ with initiator.3. The regeneration ability of EC degraded at the same time the protein level of EGF and EGFR significantly decrease when with disease of dental ulcer. the result approved 1.5 W 80 mJ laser irradiation and region drug treatment can promote dental ulcer healing .