A Preliminary Study Of The Effect Of Low Intensity Pulsed Ultrasound On Periodontium Repair With Periodontal Flap Surgery Or Guided Tissue Regeneration In Beagle Dogs

Low Intensity Pulsed Ultrasound, a secure and non-invasive therapeutic method, can promote the repair process of bone and soft tissue. Periodontal disease is the chronic inflammation of periodontium, and the key to treatment is rebuilding the structure and function of periodontal tissue.Based on the periodontal tissue regeneration theory and the biological effects of LIPUS, the study of the effect of LIPUS combined with periodontal flap surgery or guided tissue regeneration on the periodontium repair in Beagle dogs was preliminarily conducted, which may provide a adjuvant therapy of the periodontal disease by LIPUS in future.At first, LIPUS transducer morphous and fixation was reformed on the base of preliminary studies, which can avoid the artificial error and blind operation in transducer fixation, avoid thermogenesis when it works.Then,two studies were performed:1. Preliminary study of the effect of LIPUS combined with periodontal flap surgery on the chronic periodontitis repair in Beagle dogsChronic periodontitis models in mandibular premolars were eatablished in 4 Beagle dogs. After inflammation control and root surface compatibility improvement with periodontal flap surgery and root conditioning, LIPUS was conducted on the periodontitis tissue in Beagle dogs, 4 LIPUS (parameter of frequency 1.5MHz, pulsed width 200μs, repeated frequency 1kHz) groups were divided as①ISATA30mW/cm2 *20min/d group,②ISATA30mW/cm2*20min/2d group,③ISATA60mW/cm2 *20min/d group,④ISATA60mW/cm2*20min/2d group, one control group designed with flap and root conditioning treatment at the same time.6 weeks later, the inflammation of the periodontitis tissue was relieved. After LIPUS treatment no significant changes were observed with X-ray examination; and the average temperature fluctuation of the gingival tissue was below 1°C. Histological analysis indicated that the neogenetic alveolar bone in LIPUS groups was more mature than that in the control group, but no significant difference was founded in the 4 LIPUS groups; the osteoblasts were more active in ISATA30mW/cm2 *20min/d group than in other groups; long-junction epithelium was founded in each group. Fluorescent markers in vivo indicated that the neogenetic alveolar bone formation in LIPUS groups was more active than in control group.All results indicated that LIPUS with certain parameters (frequency 1.5MHz, pulsed width 200μs, repeated frequency 1kHz, ISATA30mW/cm2 or 60 mW/cm2, exposure time 20min/d or 20min/2d) may have some repairtive effects on the periodontitis tissue,especially the alveolar bone; parameters of ISATA30mW/cm2 and exposure time 20min/d may have better effects on osteoblast, which needs further study.In addition, gingival epithelium cell grows quicker than periodontal ligament cell, as a result, long-junction epthilium was founded in each group, which suggests attachment of the gingival epithelium cell and the connective tissue to root surface should be confined to received better repairtive results in periodontal tissue.2. Preliminary study of the effect of LIPUS combined with guided tissue regeneration in periodontal bone defects repair in Beagle dogs.After measuring the LIPUS penetration rates of several ePTFE membranes in different thickness, the LIPUS-penetrative ePTFE membrane which can only attenuate 10-15% LIPUS energy was chosed.Periodontal bone defect model were established in 5 Beagle dogs. LIPUS(ISATA60mW/cm2 *20min/d, freqency 1.5MHz, pulsed width 200μs, repeaded frequency 1KHz, exposure time 20min/d)was applied in the study, and 4 groups of①GTR和LIPUS combination group,②LIPUS group,③GTR group and④control group were designed.4 weeks later, the"tooth-periodontium"specimens revealed that the defects were flood with neogenetic tissue; the gingival temperature had no significant change after LIPUS treatment. Histological analysis indicated that the periodontal bone defects were flooded with neogenetic bone and connective tissue; the neogenetic periodontal tissue was more in quantity and more mature in GTR and LIPUS combination group; the quantity of neogenetic cementum and alveolar bone was more in GTR group than in control group, while the maturation of the neogenetic bone was inferior to LIPUS group; the quantity of neogenetic bone was less and the maturation was inferior in control group.The result suggested that combination of LIPUS and guided tissue regeneration can have better results on periodontal tissue repair and neogenetic bone maturation, LIPUS may have some potential on the bone maturation. The combination of LIPUS and tissue regeneration method as guided tissue regeneration may have some potential to promote the rapair of the periodontal tissue, while the membrane can attenuate some of the ultrasound engergy, the LIPUS parameters should be adjusted when used with GTR. In conclusion, LIPUS with some parameter may have some effects on calcium deposition, neogenetic bone rebuilding and maturation to shorten the periodontal tissue repair process, which may be better when combined with guided tissue regeneration. Although this study provides some reference to suitable LIPUS parameters for the adjuvant therapy of periodontal disease, the mechanism of LIPUS in the repair of periodontal tissue should be further studied.