Abstract
Low-intensity pulsed ultrasound (LIPUS) is an emerging physical therapy for the treatment of early temporomandibular joint injury and has a good effect on promoting cartilage and subchondral bone tissue repair. However, the best LIPUS intensity and treatment duration remain unclear. This study is aimed at observing the preventive and therapeutic effects of different modes of LIPUS and at identifying the optimal LIPUS treatment regimen for temporomandibular joint injury. In the present study, rat models of temporomandibular joint injury were established using a chronic sleep deprivation (CSD) method, and the effect of LIPUS as intensities of 30, 45, and 60 mW/cm2 was observed at 7, 14, and 21 days. After CSD, the condylar cartilage of the rats demonstrated variable degrees of surface roughening, collagen fiber disarrangement or even partial exfoliation, decreased proteoglycan synthesis and cartilage thickness, decreased chondrocyte proliferation, decreased type 2 collagen (COL-2) expression, and increased matrix metalloproteinase- (MMP-) 3 expression at all three time points. When the rats with CSD received different intensities of LIPUS treatment, the pathological changes were alleviated to various extents. The groups receiving 45 mW/cm2 LIPUS showed the most significant relief of cartilage damage, and this significant effect was observed on days 14 and 21. These results demonstrated that LIPUS can effectively inhibit CSD-induced condylar cartilage damage in rats, and LIPUS treatment at an intensity of 45 mW/cm2 for at least 2 weeks is the optimal regimen for temporomandibular joint injury.
Highlights
Temporomandibular joint disorder (TMD) is a common and highly prevalent disease of the oral and maxillofacial region
When treated with different Low-intensity pulsed ultrasound (LIPUS) intensities, the pathological changes in the condylar cartilage were improved to various extents, and the improvements began to be significant starting from 14 days
The Toluidine Blue (TB) staining showed that the proteoglycan distribution in the condylar cartilage was decreased in the chronic sleep deprivation (CSD) groups compared with the CON groups
Summary
Temporomandibular joint disorder (TMD) is a common and highly prevalent disease of the oral and maxillofacial region. The main pathological changes include articular disc and condylar cartilage inflammation, degenerative changes, condylar surface injury, and cartilage vascularization [1, 2]. TMD treatments can be divided into noninvasive, minimally invasive, and invasive according to the degree of trauma induced [3]. The current noninvasive treatment for TMD mainly focuses on regulating occlusal disorders or mental factors, and a direct treatment for the injury site is still lacking, which is the main reason for failure to quickly and effectively relieve local TMD symptoms [5]. Directly and effectively controlling local inflammation and promoting cartilage repair have become urgent problems that must be resolved for TMD treatment
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