| Objective: The purpose of this study was to evaluate the modification of rabbit condylar cartilage under the use of low-intensity pulsed ultrasound with using X-ray evaluation , histological analysis , immunohistochemistry method.According to evaluating the effect of therapeutic US on condylar and mandibular growth in the rabbit model ,which include anthropometrical and histological evaluations to see if the low-intensity pulsed ultrasound is possible to enhance functional appliance results.Methods: Ten growing New Zealand male rabbits (10 weeks of age) were chosen for this study. LIPUS was applied for 20 minutes/day for four weeks to the left side of the mandible in each rabbit, while the right side served as the control side. After 4 weeks ,all animals were sacrificed ,and the mandilbles were surgically removed and divided into two hemimandibles, which were radiographed with the X-ray.Each hemimandible was traced using acetate tracing paper,and three parameters were measured.Then 4-um-thick sections were cut along the sagittal plane, and stained with hematoxylin and eosin. HE staining was used to detect the histological changes and immunohistochemical technique was used to detect the expression of TGF-β1 .JD801 Morphology Software was used to measure the changes. Students' t-test was used to determine if there were significant differences between the 2 sides.Results: 1. According to the X-ray evaluation,the mean and standard deviation of the anthropometrical variables measured in this study showed that there was a significant increase in the mandibular ramus length, condylar height and mandibular length in the US-treated hemimandibles compared with the untreated hemimandibles.Enlarged condyles and increased ramal height were clearly observed in the US-treated sides compared with the nontreated sides.Canting of the occlusal plane could also be seen.2. From histological point, wo divided the condylar cartilage into five layers ,which included fibrin, unpolarization, transition, maturation, and calcification layers in this study.3. HE staining detection showed with the use of LIPUS there was significant difference between the experimental side (ES) and control side (CS) in the total layer thickness: 467.31um to 368.38um. The most obvious change of layer thickness was found in maturation layer.4. HE staining detection showed with the use of LIPUS there were significant differences between ES and CS in the cell amount of unpolarization, transition, and maturation layers of the US-treated hemimandibles, especially of the former two layers.5. HE staining detection showed with the use of LIPUS there were significant differences between ES and CS in the cell area of transition, maturation, and calcification layers of the US-treated hemimandibles, especially of the maturation layer.6. Immunohistochemical technique results showed that the expression of TGF-β1 were detected in unpolarization, transition, maturation, and calcification layers, especially of the maturation and calcification two layers. After the use of LIPUS , the TGF- β1 were expressed noticeably and the immunostain levels of the ES were higher than those of CS, especially of the maturation and calcification layers. Conclusion: 1. According to the X-ray evaluation, this study shows that LIPUS can stimulate significant increase in the mandibular ramus length, condylar height and mandibular length in the US-treated hemimandibles.Also LIPUS can Enlarge condyles and increase ramal height.2. In this study ,the fibrin layer shows the most stable characteristic of the five layers,not only from histological but immunohistochemical points.3. With the use of LIPUS there were significant differences between ES and CS in the cell amount of unpolarization, transition layers of the US-treated hemimandibles ,which have proliferate characteristic.This result shows that LIPUS can stimulate cell proliferation.4. With the use of LIPUS there were significant differences between ES and CS in the cell area of transition, maturation layers, especially of the maturation layer. This result shows that LIPUS can stimulate cell maturation.5. With the use of LIPUS there was significant difference between the experimental side (ES) and control side (CS) in the total layer thickness: 467.31 urn to 368.38um. The most obvious change of layer thickness was found in maturation layer. This result shows that the effect of LIPUS is to stimulate cell maturation mainly.6. Immunohistochemical technique results showed the TGF- β1 were expressed noticeably and the immunostain levels of the ES were higher than those of CS. This result shows that LIPUS can stimulate the condylar and mandibular modification.
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