Pathogenesis of traumatic temporomandibular joint ankylosis: a narrative review

IRE1α inhibits osteogenic differentiation of mouse embryonic fibroblasts by limiting Shh signaling

OBJECTIVES

This study aimed to investigate the effect of endoplasmic reticulum (ER) stress sensor inositol-requiring enzyme 1α (IRE1α) on the sonic hedgehog N-terminus (N-Shh)-enhanced-osteogenic differentiation process in mouse embryonic fibroblasts (MEFs).

MATERIALS AND METHODS

Osteogenesis of MEFs was observed by alkaline phosphatase (ALP) staining, alizarin red staining, and Von Kossa staining assays. Activation of unfolded protein response and Shh signaling were examined using real-time quantitative PCR and western blot assays. IRE1α-deficient MEFs were used to explore the effect of IRE1α on N-Shh-driven osteogenesis.

RESULTS

N-Shh increased ALP activity, matrix mineralization, and the expression of Alp and Col-I in MEFs under osteogenic conditions; notably, this was reversed when combined with the ER stress activator Tm treatment. Interestingly, the administration of N-Shh decreased the expression of IRE1α. Abrogation of IRE1α increased the expression of Shh pathway factors in osteogenesis-induced MEFs, contributing to the osteogenic effect of N-Shh. Moreover, IRE1α-deficient MEFs exhibited elevated levels of osteogenic markers.

CONCLUSIONS

Our findings suggest that the IRE1α-mediated unfolded protein response may alleviate the ossification of MEFs by attenuating Shh signaling. Our research has identified a strategy to inhibit excessive ossification, which may have clinical significance in preventing temporomandibular joint bony ankylosis.

Temporomandibular Joint Ankylosis as a Sequel of an Overlooked Condylar Fracture in a Child

Temporomandibular joint ankylosis is an important entity that dentists and maxillofacial surgeons should know about. It clinically manifests through a permanent limitation of mandibular movements coupled with mouth opening inferior to 3 cm. This serious pathology can have serious functional repercussions, such as mastication problems, speech troubles, eating disorders, and jaw growth hindrance, in addition to the psychological difficulties in coping with such a condition in daily life. Herein, we present a radiological and chronological illustration of the evolution of temporomandibular joint ankylosis following an overlooked traumatic fracture of the mandibular condyle. The present case report involves an 8-year-old patient referred for a gradually evolving mouth opening limitation following a car accident. Tomodensitometry was helpful as it revealed an osseous block between the left temporomandibular joint surfaces, showing an ankylosis. Posttraumatic cerebral computed tomography scan was performed. It revealed an undetected fracture of the left condyle. The aim of this paper was to show how a traumatic ankylosis could have been avoided if enough attention was paid to the interpretation of immediate posttraumatic computed tomography scans. A thorough dental examination must be carried out once vital emergency is over. Early diagnosis of temporomandibular joint trauma is a crucial factor in preventing complications, such as ankylosis and its consequent oral dysfunctions. The dentist must automatically suspect condylar fracture when a child presents a history of head trauma, especially a mandibular trauma. This case should be a reminder that although temporomandibular joints are very often left out in patients' vital emergency first examination, temporomandibular joints/they are still a highly important structure which omission, and thus, dysfunction, if lesions are present, can lead to nonnegligible medico-legal consequences/that temporomandibular joints should be taken into account during patients' vital emergency first examination because if they are neglected, in the presence of lesions, they cause dysfunction, thus leading to nonnegligible medico-legal consequences.

Puricelli biconvex arthroplasty as an alternative for temporomandibular joint reconstruction: description of the technique and long-term case report

Background

There are several indications for partial or total replacement of the temporomandibular joint (TMJ), including neoplasms and severe bone resorptions. In this regard, several techniques have been suggested to increase the functionality and longevity of these prosthetic devices. This case report describes the treatment of a TMJ ankylosis patient with the Puricelli biconvex arthroplasty (ABiP) technique, with a long-term follow-up.

Case presentation

In 1978, a 33-year-old male polytraumatised patient developed painful symptoms in the right preauricular region, associated with restricted movement of the ipsilateral TMJ. Due to subcondylar fracture, an elastic maxillomandibular immobilisation (EMMI) was applied. Subsequently, the patient was referred for treatment when limitations of the interincisal opening (10 mm) and the presence of spontaneous pain that increased on palpation were confirmed. Imaging exams confirmed the fracture, with anteromedial displacement and bony ankylosis of the joint. Exeresis of the compromised tissues and their replacement through ABiP was indicated. The method uses conservative access (i.e., preauricular incision), partial resection of the ankylosed mass, and tissue replacement using two poly(methyl methacrylate) components, with minimal and stable contact between the convex surfaces. At the end of the procedure, joint stability and dental occlusion were tested. The patient showed significant improvement at the postoperative 6-month follow-up, with no pain and increased mouth opening range (30 mm). At the 43-year follow-up, no joint noises, pain or movement restrictions were reported (mouth opening of 36 mm). Imaging exams did not indicate tissue degeneration and showed the integrity of prosthetic components.

Conclusions

The present case report indicates that ABiP enables joint movements of the TMJ, allowing the remission of signs and symptoms over more than 40 years of follow-up. These data suggest that this technique is a simple and effective alternative when there is an indication for TMJ reconstruction in adult patients with ankylosis.