Diagnostic accuracy of microcomputed tomography for osseous abnormalities in the rat temporomandibular joint condyle

A rat model for inducing temporomandibular anterior disc displacement experimentally

The aim of this study was to establish an experimental rat model of temporomandibular joint (TMJ) anterior disc displacement (ADD). A pilot study was conducted to determine the most appropriate surgical protocol. In the main experiment, 40 rats were used. Twenty-four rats were subjected to ADD in the right TMJ, and subsequently thereafter six, nine, and nine rats were sacrificed at 1, 4, and 8 weeks, respectively, for gross evaluation. Twelve rats that underwent a sham operation were equally divided and sacrificed at each of the above time points. Four non-treated control rats were sacrificed at the beginning of the study. TMJ blocks were harvested for radiological and histological assessment. Gross examination showed that 14 rats in the ADD group (58.3%) had anterior displacement of the TMJ disc. In the ADD joints, posterior condylar cartilage thickness decreased during the follow-up period; however, there was no significant difference between the sham-treated and ADD joints, or among the follow-up time points (P > 0.05). The anterior condylar cartilage exhibited obvious qualitative alterations. Radiologic signs of osteoarthrosis appeared after ADD surgery, but this became attenuated with time. The model investigated in this study successfully induced ADD in rats, and should be useful for assessment of progressive changes in the TMJ following ADD.

Effect of low-intensity pulsed ultrasound (LIPUS) on mandibular condyle growth in rats analyzed with micro-CT

This study examined the effects of a bite-jumping appliance combined with low-intensity pulsed ultrasound (LIPUS) stimulation on the mandibular condyle of growing rats using micro CT (mCT) and histological examinations. Twelve Wistar rats were divided into three groups of four individuals each: Group 1 was an untreated control group, Group 2 received bite-jumping appliances, and Group 3 received bite-jumping appliances and LIPUS stimulation (15 min/day, 2 weeks) to the temporomandibular region. We measured the length and three-dimensional bone volume of each rat's mandibular condyle using mCT. The condylar cartilage was observed after the rats had been sacrificed. There was no significant difference in condylar sagittal width among the groups. The bite-jumping appliance combined with LIPUS stimulation increased the condylar major axis, mandibular sagittal length and condylar bone volume to a greater degree than use of the bite-jumping appliance alone. Histological examination demonstrated hypertrophy of the condylar cartilage layers, the fibrous layer and hypertrophic cell layer of the rats treated with bite-jumping appliances combined with LIPUS stimulation in comparison to rats treated with bite-jumping appliances alone. (J Oral Sci 58, 415-422, 2016).

Effects of high molecular weight hyaluronic acid on induced arthritis of the temporomandibular joint in rats

High molecular weight hyaluronic acid (HMWHA) has been used to treat temporomandibular joint (TMJ) disorders, but controversial results have been described. This study aimed to characterize the morphological and biochemical actions of HMWHA on induced arthritis of the TMJ. Twenty-four male Wistar rats were used, and arthritis of the TMJ was induced through an intra-articular injection of Complete Freund's Adjuvant (CFA) (50 μl). One week after arthritis induction, the animals were treated with HMWHA (once per week for three weeks). Histological analyses were performed using sections stained with hematoxylin-eosin, toluidine blue and Picrosirius. Were also performed histomorphometric analysis and birefringence of collagenous fibers (polarization microscopy). Biochemical analyses of TMJ tissues were carried out through measurements of sulfated glycosaminoglycans and zymography for evaluation of metalloproteinase-2 and -9 (MMP-2 and -9). Data were analyzed using paired t-test and unpaired t-test, with a 5% significance level. HMWHA reduced histologic changes and thickness of the articular disc, led to a greater arrangement of collagenous fibers, lower concentration of sulfated glycosaminoglycans and lower activity in all isoforms of MMP-2 and -9 in TMJs with induced arthritis. These findings suggest that HMWHA may exert a protective effect on the TMJ.

The use of micro-computed tomography in the diagnosis of dental and oral disease in rabbits

Background

The aim of this study was to investigate the use of a newly developed micro-computed tomography (micro-CT) system for the diagnosis of oral pathologies in small animals, using the rabbit as a model. The diagnosis of dental diseases in rabbits is usually based on oral endoscopy and radiographic imaging, but detailed pathological diagnosis using these methods is frequently difficult. Micro-CT was used in this study to address this challenge.

Results

This study was conducted using 50 privately owned rabbits, presented to our hospital due to loss of appetite or difficulty feeding. Image recording times were 18 s in normal mode and 120 s in fine mode. The animals were maintained in the required position for scanning via the administration of sedatives. Micro-CT captured with a slice thickness of 60–120 mm has excellent spatial resolution, and is suitable for the clinical diagnosis of dental diseases in rabbits weighing 1–3 kg.

Conclusions

Micro-CT can yield more detailed data than radiography or conventional CT. This study determined that this novel imaging modality can be utilized for the accurate assessment of dental and oral diseases in rabbits.

Contrast-enhanced microCT (EPIC-μCT) ex vivo applied to the mouse and human jaw joint

OBJECTIVES

The temporomandibular joint (TMJ) is susceptive to the development of osteoarthritis (OA). More detailed knowledge of its development is essential to improve our insight into TMJ-OA. It is imperative to have a standardized reliable three-dimensional (3D) imaging method that allows for detailed assessment of both bone and cartilage in healthy and diseased joints. We aimed to determine the applicability of a contrast-enhanced microCT (µCT) technique for ex vivo research of mouse and human TMJs.

METHODS

Equilibrium partitioning of an ionic contrast agent via µCT (EPIC-µCT) was previously applied for cartilage assessment in the knee joint. The method was ex vivo, applied to the mouse TMJ and adapted for the human TMJ.

RESULTS

EPIC-µCT (30-min immersion time) was applied to mouse mandibular condyles, and 3D imaging revealed an average cartilage thickness of 110 ± 16 µm. These measurements via EPIC-µCT were similar to the histomorphometric measures (113 ± 19 µm). For human healthy OA-affected TMJ samples, the protocol was adjusted to an immersion time of 1 h. 3D imaging revealed a significant thicker cartilage layer in joints with early signs of OA compared with healthy joints (414.2 ± 122.6 and 239.7 ± 50.5 µm, respectively). A subsequent significant thinner layer was found in human joints with late signs of OA (197.4 ± 159.7 µm).

CONCLUSIONS

The EPIC-µCT technique is effective for the ex vivo assessment of 3D cartilage morphology in the mouse as well as human TMJ and allows bone-cartilage interaction research in TMJ-OA.

In vivo morphometric analysis of inflammatory condylar changes in rat temporomandibular joint

OBJECTIVE

Injection of complete Freund's adjuvant (CFA) into the temporomandibular joint (TMJ) causes acute swelling around the joint and subsequent morphological alterations in the condyle. We aimed to evaluate changes in the three-dimensional architecture of the condyle induced with CFA.

MATERIALS AND METHODS

The CFA was injected into the unilateral TMJ of rats and morphological changes in the condyle were assessed repeatedly for 14 days by in vivo micro-CT.

RESULTS

Osseous abnormalities of condyle were first observed at 3-5 days after CFA injection on the tomographic images, and the condylar deformation became more obvious thereafter. Among 12 condyles examined at 14 days postinjection, osteophytosis was observed in all of the specimens and bone erosion coexisted in five condyles. None of the saline-treated condyles showed architectural changes. Significant changes were detected in the mesiolateral and rostrocaudal widths of the CFA-treated condyles at 10-14 days postinjection (P < 0.01). The extent of both condylar bone formation and resorption was greater in the CFA-injected TMJs than in saline-injected TMJs (P < 0.05).

CONCLUSION

These results indicate that CFA causes dynamic morphological changes in the condyle and that our experimental approach will provide new insights into the subacute inflammatory processes in the TMJ.

Establishment of temporomandibular joint puncture technique in rats using in vivo micro-computed tomography (R_mCT®)

The aim of the report was to establish puncture techniques for the temporomandibular joint (TMJ) cavity in rats. The experimental sample comprised 30 male Sprague-Dawley rats. Under general anaesthesia the superior joint cavity of the rat was punctured either laterally (lateral puncture technique (LPT), n = 11), anteriorly (anterosuperior puncture technique (ASPT), n = 13) or anteroinferior puncture technique (AIPT), n = 6) using a 27-gauge needle. After the tip of the needle was confirmed by micro-CT (R-mCT®, Rigaku, Tokyo, Japan) located on the mandibular fossa, 0.05 ml of contrast media was injected under micro-CT fluoroscopic guidance. After confirmation that the joint cavity was filled with contrast media, micro-CT imaging was carried out. The puncture for LPT was accurate in 5 of the 11 animals. The ASPT was accurate in all 13 animals. The AIPT punctured 3 of the 6 animals. Furthermore, the ASPT and AIPT demonstrated improved preservation of the needle; it was harder to detach the needle, which led to greater stability. These results suggest that ASPT assisted by R-mCT® is useful for basic research, including drug discovery and pathogenesis of TMJ diseases.