Impact of estrogen therapy on temporomandibular joints of rats: Histological and hormone analytical study

Abstract

Objectives: This research aims to evaluate the effects of estrogen deficiency and replacement on the TMJ structures of rats. The considerable similarities in the anatomical features of rats and humans make rats a suitable model for human scientific studies.

Methods: A clinical trial was conducted on 18 female Sprague-Dawley rats grouped into three categories. The GI group included 6 female rats labelled as the control group, the GII group consisted of 6 females that received ovariectomies, and the GIII group had 6 ovariectomised females that were injected with estrogen replacement therapy in a science laboratory at King Abdulaziz University. ANOVA and Tukey HSD post hoc tests were used to determine any significant differences between the levels of estrogen among the three groups.

Results: The results indicate that some TMJ structures, including the articular disc and condylar cartilaginous layer, were degraded after estrogen deficiency. However, there was a slight improvement in the cartilaginous layer thickness and proliferation of chondroid cells after estrogen replacement therapy. Estrogen level was reduced in the ovariectomized rats, and while estrogen injections increased blood hormone levels, the levels did not reach those of the control group.

Conclusion: Estrogen deficiency degraded some TMJ structures, and there is only a slight recovery after estrogen replacement therapy.

Keywords: Estrogen; Ovariectomy; TMJ; Temporomandibular disorder; Temporomandibular joint.

Fig. 1

Photomicrograph from the sagittal section of the temporomandibular joint (TMJ) from a female rat in the control group (GI) showing the histological components. Legend: roof of the glenoid fossa (GF); condylar bone (CL); articular disc (AD). (H & E stain, orig. mag. X100).

Fig. 2

Photomicrograph from the sagittal section of the TMJ from a female rat in the group (GII) showing the fragmentation of the articular disc (arrow) and the fusion of the central part of the disc with the fibrous layer of the condylar head (arrowhead), the irregular thickness of the condylar cartilaginous layer, and the approach of the bone marrow spaces to the condylar cartilaginous layer. (H& E stain, orig. mag. X100).

Fig. 3

Photomicrograph from the sagittal section of the TMJ from a female rat in the group (GШ) showing the changes in the condyle fibrocartilagenous layer and a lack of interface between the condylar cartilaginous and fibrous layers. The cartilaginous layer exhibited an increased thickness and a proliferation of chondroid cells. (H & E stain, orig. mag. X00).

Fig. 4

Bar chart representing the mean estrogen levels in the control and experimental animal groups.