The Experimental Study Of Low-frequency Ultrasound In The Treatment Of Oral Ulcer

Background The term "oral mucosal disease" is the general name applied to indicate various types of diseases which occur in the oral mucosa and soft tissues. The oral cavity ulcer, mainly occurring in the oral mucosa, is the most common oral mucosal disease. It is shown in an investigation that at present the incidence of oral diseases makes up74%of China’s population. Among different kinds of oral diseases, the following four are the most common ones:dental caries, gingivitis, periodontal disease and oral ulcer. The prevalence rate of oral cavity ulcer is high up to20%, ranking the first in oral mucosal diseases and the third in oral diseases, only after caries and periodontal diseases. But because of the complexity of the etiology of oral cavity ulcer, the obvious individual differences, as well as the particularity of oral environment, the main treatment usually combines local treatment with systemic therapy to prolong the intermission, shorten the episode, and alleviate symptoms. Due to the sophisticated medication, the side reactions, such as the patients’high compliance, the local treatment, therefore, becomes a hotspot and a difficulty in clinical treatments of oral cavity ulcer. The primary method in local treatment is the application of medication, mainly functioning so as to diminish inflammation, relieve pain and promote healing. However, because of the special environment of the oral cavity, the medication applied in the mouth can be easily diluted by saliva and its effectiveness is thus reduced. Based on this, a new way which can promote medication absorption and increase its effectiveness should be found.In recent years, with the study of biological effects of ultrasound deepened, the application of low-frequency ultrasound in medical treatment has attracted widespread attention of scholars, no matter at home or abroad. Because its equipment is safe, low technical involved and easy to control, the low-frequency ultrasound is usually used to promote to the incision, tendon injury, nerve damage, fracture and restoration or regeneration of radiation osteonecrosis, which obtain positive results. But reports about the low-frequency ultrasound applied in oral mucosal diseases treatment are rarely heard. It was reported once that the low-frequency ultrasound toothbrush was applied in the treatment of oral ulcer. The main principle is to use the piezoelectric ultrasonic transmitter embedded in the head of the toothbrush to transmit low intensity ultrasound. When people brushing the teeth, the ultrasound makes contact with the gums and stimulates the oral mucosa so as to achieve therapeutic purpose. However, because of its low curative effect, this kind of toothbrush has not been widely used. Therefore, if the low-frequency ultrasonic therapeutic apparatus can be improved in the treatment of oral ulcers, a new, safe, reliable local treatment of oral cavity ulcer pathway will be opened up, the pain of patients’can be thus reduced, and their quality of life would be highly improved.Objective By the modification of Chen Qianming’s method to establish animal models of oral ulcer, the present experiment applies different doses of low-frequency ultrasound irradiation, observes the time of healing and histopathological changes; at the same time, the present experiment would conduct a discussion about the impact of low-frequency ultrasound on the activity of superoxide dismutase (SOD) in oral ulcer tissue, the content of malondialdehyde (MDA), nitrogen monoxide (NO) and nitricoxide synthase (NOS); besides, this experiment would apply immunohistochemical techniques to observe and analyze the changes of epidermal growth factors and their receptors.Materials and methods(1) Use the oxygen free radical induction method and the physical burn method to establish the SD rat buccal mucosa ulcer; then, observe the formation of ulcer with naked eyes for24hours, cut specimens and conduct pathological section identification by using the method of HE staining;(2) After the success of modeling, radiate the ulcer surfaces with different doses of low-frequency ultrasound respectively, and record the healing time of the experimental rats’ oral mucosal ulcer; then measure with chemical reagents the content of NO, NOS, MDA in ulcer tissues and the activity of SOD. (3) Embed the different groups of samples in paraffin, make pathological biopsy, use the immunohistochemical techniques to test and analyze the changes of epidermal growth factors and their receptors.Results(1) This experiment modifies Chen Qianming’s method of constructing SD rat ulcer models, and the histologic sections shows the basic pathological features of rats’ulcer is similar to those of human oral cavity ulcer;(2) The healing time of low-frequency ultrasound group is shorter than that of the ulcer group and the medication group, but there was no significant difference among the groups of low-frequency ultrasound. The contents of NO, NOS and MDA in groups of which the low-frequency ultrasonic output is1.1W,1.58W,2.06W respectively are remarkably reduced (P<0.05) and the contents of SOD are obviously increased (P<0.05), which has no statistic significance between groups under nonnal control (P>0.05);(3) EGF in nonnal oral mucosa cell cytoplasm shows in positive expression; however, the volume of its positive expression in oral cavity ulcer tissue declines (P<0.05); EGFR is expressed both in normal oral mucosa and in ulcer tissue, but the expression in the normal mucosa mainly exists in the basal layer of the cell cytoplasm and the cell membrane; in ulcer tissue, its positive expression rate in ulcer regional tissue cells is relatively low. Because the ulcer area epithelial structure disappears, the expression rate in the epithelia on the edge of ulcer is low; but in the groups of different powers of low-frequency ultrasound and the medication group, the positive expressions of EGF and EGFR in ulcer regional tissue are higher than those in the tissue of ulcer groups (P<0.05), but have no significant difference between normal groups (P>0.05).Conclusions(1) A modified Chen Qianming’s method can be successfully applied to construct animal models of oral ulcer;(2) The experimental results show that the radiation of different powers of ultrasound (1.1W,1.58W,2.06W) can shorten the healing time of oral ulcer; however, there is no obvious difference among them, even between the medication group. It is testified by the experiment that the low-frequency ultrasound can be applied in the treatment of oral ulcer and it may have a positive effect.(3) The experimental results also show that after the irradiation of different powers ultrasound (1.1W,1.58W,2.06W), the contents of NO, NOS and MDA in the ulcer tissue of rats’reduces, but the content of SOD increases, resuming to the normal volume, which illustrates the low-frequency ultrasound of power between1.1W to2.06W may promote the cure of oral ulcer.