An Experimental Study With The Effects Of Low-intensity Pulsed Ultrasound On Biological Rebuilding Of Beagle Dog's Periodontal Tissues

Low-intensity pulsed ultrasound (LIPUS) has biophysical effects of promoting bone to repair and regenerate.The repair and regeneration of periodontal organizations is one of the key to periodontal therapy, and LIPUS is introduced into the treatment of periodontal disease which has a theoretical possibility, it is worth further exploration.This study establishes the Beagle dog model of chronic periodontitis caused by alveolar bone defect with ligation, and compares the different parameters of LIPUS (intensity, frequency and duration) to study the biological effects of LIPUS on Beagle dog's periodontal tissues.This study would discuss the feasibility and effectiveness of LIPUS which stimulated periodontal tissue to repair and regenerate.At the same time, this study would research and develop the treatment probe of LIPUS for periodontal disease animal model of Beagle dogs,and which would be conducive to the LIPUS to full irradiate Beagle dog's periodontal disease organizations.In this study choosed experimental animals:six Beagle dogs were induced a defect of alveolar bone with ligation to rapidly construct a chronic periodontitis in Beagle dogs.Based on the animal model, this study used impression material and denture base resin (Type II) to produce the probe retention which adaptated to the anatomical structure of oral cavity of Beagle dogs,and improved the shape, size, operation mode of the probe according to the actual demand for irradiation treatment of periodontal disease and special form periodontium of the Beagle dogs,which to design the probe(ultrasonic transducer).On the basis of the rapid construction of chronic periodontitis animal model,this study selected the different parameters of LIPUS(50mW/cm2,100mW/cm2), the frequency of 1.5 MHz, the width modulation signal wave 200μs, 1 KHz repetition rate, to irradiate the experimental groups for eight weeks.The same duration of time was used for the control groups with no ultrasonic irradiation. The experimental animals were sacrificed after two months of irradiation treatment.We accessed to"dental-periodontal tissue"specimens,and conjuncted the clinical indicators of Periodontal Examination, Digital Radiography (DR)--KOARD DR3000, XR-46 bone mineral density measurement instrument, Histomorphology,et al. to do a preliminary study and evaluation for the effects of LIPUS which would rebuild Biology of Beagle dogs periodontium and control periodontal infection.This study found that during the eight weeks of LIPUS irradiation, the gingival tissue of experimental groups changed gradually from swelling, bleeding on probing, to reduction of bleeding and gradual disappearance of swelling. The color of gingival gradually was close to the surrounding normal gingival tissue. When compared with the control groups, the gingival inflammation of the experimental groups reduced significantly. It was found that the experimental groups had no obvious gingival recession, attachment loss and root furcation lesions. At this time, the gingiva of the control groups bleeded easily on probing,and there were different levels of gingival recession, attachment loss,exposed root furcation,furcation diseases and deeper periodontal pocket observed. Through the detection of periodontal indicators, it was found that different intensity groups ISATA50mW/cm2 continuous wave,ISATA50mW/cm2 pulsed wave and ISATA100mW/cm2 pulsed wave had some effect on control of inflammation for the gingival tissue to a certain extent. However, with different intensity irradiation, there was no significant difference on the experimental groups. Compared with the control groups,different intensity groups ISATA50mW/cm2 continuous wave,ISATA 50mW/cm2 pulsed wave and ISATA100mW/cm2 pulsed wave radiated 20min/d could make the gingival tissue collagen synthesis of experimental groups increase and we found a small number of chronic inflammatory cells infiltration;as well as the osteoblast activity and arraying around the new bone.Also there was a small amount of new bone formation in the area of the absorbed of alveolar ridge,and the surface of new bone had the newly formed not yet calcified bone matrix (osteoid).Compared with the control groups,the bone resorption lacunae of experimental groups decreased. However, with different intensity irradiation in experimental groups, the biological effects of alterations of different experimental groups were not significant.Compared with the control groups, the alveolar bone density of the experimental group increased significantly after LIPUS irradiation of eight weeks.It suggested that LIPUS may promote the increase in bone mass, but there was no clear distinction on different intensity groups. At the same time, we found that in both the experimental groups and the control groups, the average maxillary bone mineral density was significantly lower than mandible's.From the X-ray subjective judgement, there was a certain distinction between experimental groups and control groups, and different intensity experimental groups had not yet a clear distinction.In this study, there was apparent advantage for ultrasound treatment groups compaired to the control groups in the view of the detection of clinical indicators(GI,BI,PD,CAL,Glickman),but not in the view of X-ray inspection in this study. To a large extent,as the X-ray projection angle and the characteristics of 2D display to three-dimensional anatomical structure,the image of teeth and alveolar bone overlaped more in X-ray, so it was difficult to accurately assess the experimental results. So judgement should be combined with clinical examination. LIPUS could make new bone formation actively of canellous bone, and increase the mineral density of alveolar bone. It suggested that LIPUS had a certain biological effects to rebuild the alveolar bone of Beagle dogs, and made new bone formation,so that LIPUS would promote periodontal tissues to repair and regenerate.This research selected different intensity groups ISATA50mW/cm2continuous wave,ISATA50mW/cm2pulsed wave and ISATA100mW/cm2 pulsed wave irradiation for the same time, and LIPUS had a certain effect to make periodontal tissues repair and regeneration. However,there was no significant difference in whether the intensity of the groups or continuous wave and pulsed wave.So we should select the appropriate parameters of LIPUS for periodontal disease animal model of Beagle dogs for further.To sum up, this study rapidly established the Beagle dog model of chronic periodontitis caused by alveolar bone defect with ligation.With the small samples and specific parameters, through the clinical indicators of Periodontal Examination, digital X-ray imaging system(KOARD DR3000), XR-46 bone mineral density measurement instrument, Histomorphology,LIPUS had a certain effects to rebuild biology of Beagle dogs periodontitis,and a trend for LIPUS to make periodontal tissues repair and regeneration.It was significant to further reveal the biological rebuilding mechanism of LIPUS for periodontitis, and need to be further in-depth study.