Preliminary Study Of The Effect Of Low-Intensity Pulsed Ultrasound On Promoting Bone Repair In Beagle Dogs' Alveolar Bone And Mandible Defect Model

Alveolar bone defect is one of the main features of the periodontal disease, and how to promote the alveolar bone regeneration and repair effectively has been the key to treatment of periodontal disease. Although the previous treatment, such as Periodontal scaling, Bone graft, GBR (Guided Bone Regeneration) , growth factors and Periodontal tissue engineering, etc., were effective to some extent, but also need to be further improved.As a safe and non-invasive treatment, LIPUS (Low Intensity Pulsed Ultrasound) had the role of promoting bone repair and regeneration, and it had been used to promote fresh fracture healing and treatment of bone nonunion. At present, the study of LIPUS of promoting bone regeneration and repair is focused on fracture healing and distraction osteogenesis areas. There were few researches of LIPUS in the alveolar bone regeneration and repair areas, and it's still in initial stage in this regard. So in this study, we established the alveolar bone defect model of Beagle dogs'mandibular premolars by periodontal surgery, and we also established a Beagle dogs' mandible bone defect model as the auxiliary control group. To provide the comparison and initial basis in the further application of LIPUS for the treatment of periodontal disease, we explored the biological effects of LIPUS in the alveolar bone and mandible defect models.PARTⅠThe preliminary study of the effect of LIPUS on promoting bone repair in Beagle dogs'mandibular premolars alveolar bone defect model.Objects of this study were the bilateral mandibular third and fourth premolars of 2 adult male Beagle dogs. We established the alveolar bone defect models by removing 6mm buccal alveolar bone under the CEJ (the cementum-enamel junction) by periodontal surgery. The experimental group and the control group were randomly selected. LIPUS (ISATA 30mW/ cm2, 1.5MHz, 200μs, 1KHz) treated the experimental group 20 minutes per day, a total of eight weeks. Resulst of periodontal clinical examination(GI, PD, AL)showed that experimental group periodontal Clinical symptoms was less serious than the control group. Dual-energy X-ray bone mineral density (BMD) inspection: experimental group was 0.6689±0.0598g/cm2,and control group was 0.6353±0.0600 g/cm2. Histopathological analysis (HE, MASSON): In the experimental group, the newly formed alveolar bone collagen was obviously red dyed. The bone was dyed with red, and the red area around the cartilage was larger and showed a higher degree of calcification than the control group. Imaging and histological analysis showed that LIPUS could increase the level of calcification and bone density, promote the newly formed bone to rebuild mature organizational structure. This experiment suggested that the specific parameters of LIPUS may have a certain effect to promote the alveolar bone regeneration and repair, however, further study is needed.PARTⅡThe preliminary study of the effect of LIPUS on promoting bone repair in Beagle dogs mandible defect model.We established one round bone defect (diameter of 5 mm, deep of 4 mm) on both sides of the mandible in two male Beagle dogs by periodontal surgery. The experimental group and the control group was randomly selected for this study. LIPUS (ISATA 30mW/ cm2, 1.5MHz, 200μs, 1KHz) treated the experimental group 20 minutes per day, a total of six weeks. Dual-energy X-ray bone mineral density (BMD) inspection: experimental group was 0.5141g/cm2,and control group was 0.6353±0.0600 g/cm2. Scanning by electron microscopy showed that: The trabecular bone of experimental group, which was similar to the normal alveolar bone, was tighter and thicker and the degree of calcification was more significant than the control group. X-ray spectrum analysis of elements in calcium and phosphorus showed that: Ga/P=1.546±0.0951(experimental group), Ga/P=0.92±0.1370(control group). Histopathological analysis (MASSON) showed that: The newly formed bone of the experimental group was red dyed obviously, with a higher degree of calcification, and it's similar to the normal structure of the mandible bone. Bone lacuna around the osteoblasts was obvious. In the control group, the newly formed bone was mainly blue-dyed osteoid, with less red-dyed collagen and lower degree of calcification, and it's similar to cartilage collagen structure. The results suggested that: specific parameters of LIPUS could promote calcium deposits, increase bone density and speed up the establishment of the normal bone structure in the Beagle dog's mandible bone defect areas.To sum up, LIPUS could accelerate the process of calcium deposits, promote newly formed bone to rebuild into the mature bone structure and shorten the time of bone repair in the Beagle dog's alveolar and mandible bone defects. Therefore, this study suggested that as an effective contributing factor for bone repair, we can combine LIPUS and other methods of alveolar bone regeneration, such as GTR/GBR, bone graft operation, periodontal tissue engineering, etc., to increase alveolar regeneration in clinical treatment of periodontal disease.