Augmented Indian hedgehog signaling in cranial neural crest cells leads to craniofacial abnormalities and dysplastic temporomandibular joint in mice.

Extensive studies have pinpointed the crucial role of Indian hedgehog (Ihh) signaling in the development of the appendicular skeleton and the essential function of Ihh in the formation of the temporomandibular joint (TMJ). In this study, we have investigated the effect of augmented Ihh signaling in TMJ development. We took a transgenic gain-of-function approach by overexpressing Ihh in the cranial neural crest (CNC) cells using a conditional Ihh transgenic allele and the Wnt1-Cre allele. We found that Wnt1-Cre-mediated tissue-specific overexpression of Ihh in the CNC lineage caused severe craniofacial abnormalities, including cleft lip/palate, encephalocele, anophthalmos, micrognathia, and defective TMJ development. In the mutant TMJ, the glenoid fossa was completely absent, whereas the condyle and the articular disc appeared relatively normal with slightly delayed chondrocyte differentiation. Our findings thus demonstrate that augmented Ihh signaling is detrimental to craniofacial development, and that finely tuned Ihh signaling is critical for TMJ formation. Our results also provide additional evidence that the development of the condyle and articular disc is independent of the glenoid fossa.

Temporomandibular joint development and functional disorders related to clinical otologic symptomatology.

Temporomandibular disorders (TMDs) are a form of musculoskeletal pain of the temporomandibular joint (TMJ) and/or masticatory muscles of nonspecific etiology. In this study, the relationship between embryonic and anatomic-topographic similarities of the TMJ and the ear was analyzed, i.e. secondary otologic symptoms that can be closely connected to TMJ disorder. Nonspecific otologic symptoms are not primary diagnostic symptoms of TMD, but may cause diagnostic confusion due to patients' inability to correctly locate the origin of pain. The most common otologic symptoms that can be related to TMDs are otalgia, tinnitus and vertigo. Otorhinolaryngologists have to differentiate between primary otologic symptoms and those caused by TMJ disorders. In TMD diagnosis, manual techniques are used to determine the arthrogenic or myogenic form, whereas in the diagnosis of arthrogenic disorders magnetic resonance imaging is indicated as the highly specific imaging method ofjoint disk and osteoarthritic changes. Symptomatic treatments for TMD as well as the etiologic diagnosis of the pain require multidisciplinary cooperation between dentists and medical specialists.

Theories on Otic Symptoms in Temporomandibular Disorders: Past and Present / Teorías de los Síntomas Óticos en los Trastornos Temporomandibulares: Pasado y Presente

For many years otic symptoms have been closely observed in TMD clinical practice. This review includes trials that meet eligibility criteria in the field of otic symptoms diagnosed and treated by a stomatognathic focal point. The aim is centered on the implications of the debated cause-effect connection between otic symptoms and TMD offering a probable bond between the TMJ, ear and adjacent structures. The rationalization is based on an embryological and anatomical approach that offers explanations on the otic pathogenic mechanisms symptoms interconnected with TMD. The accompanying reciprocity among disciplines of odontology and otolaryngology is brought together by TMD and otic referred mutual symptomatology as is showed in multiple trials. This research is an attempt that targets the integration of these two health specialties in the diagnosis and treatment of this type of population.

Por muchos años, síntomas óticos observados en la práctica clínica se han relacionado estrechamente con trastornos temporomandibulares (TTM). Esta revisión incluye juicios que plantean criterios específicos en el campo de los síntomas óticos diagnosticados y tratados desde un punto vista estomatognático. El objetivo está centrado en las implicancias debatidas causa-efecto entre síntomas óticos y TTM estableciendo un probable vínculo entre la ATM, oído y estructuras adyacentes. La revisión está basada en una aproximación embriológica y anatómica que explica los mecanismos y síntomas de patogenia ótica interconectados con TTM. El acompañamiento recíproco entre disciplinas de odontología y otorrinolaringología estableció un equilibrio entre los TTM y la mutua sintomatología ótica remitida, como está mostrado en múltiples diagnósticos. Esta investigación constituye un intento de alcanzar una integración entre estas dos especialidades médicas en el diagnóstico y tratamiento de este tipo de patologías.

The morphogenesis of the human discomalleolar and sphenomandibular ligaments.

The morphogenesis of the discomalleolar ligament and its relationship with the sphenomandibular ligament were studied in human embryos and fetuses, on histological grounds. Total number of 18 embryos and fetuses, ranging from 6.5 to 230 mm (5-25 weeks of fertilization age) were examined. The discomalleolar ligament emerged from the posterior part of the temporomandibular joint capsule and disc, passing through the squamotympanic fissure, joined the malleus. The superior fibres of the ligament inserted on the anterior process of the malleus and on the bony wall of the squamotympanic fissure. The inferior fibres of the discomalleolar ligament encircles the anterior malleolar ligament, the remnant of Meckel's cartilage, and chorda tympani, and inserted on the tympanic wall of the temporal bone. Within the tympanic cavity, the discomalleolar ligament and the anterior malleolar ligament, a continuation of the sphenomandibular ligament, formed a horizontal 'V' shape at the attachment site on the ventral surface of the malleus. The study shows that the discomalleolar ligament is an embryological continuation of the sheath of the lateral pterygoid muscle. The sphenomandibular ligament derives from Meckel's cartilage.

[Temporomandibular fibro-chondromalacia. Physiological basis. Classification on the basis of clinical characteristics and course. Spongialisation (author's transl)]. / Les fibro-chondro-malacies temporo-mandibulaires. Bases physiologiques. Classification nosologique et évolutive. Spongialisation.

The temporomandibular joints are neural structures which develop from the cephalic ectomesenchyme of the neural crests. They are analogous to the effector organs. Their lesional abnormalities have two characteristics:--pain sensation,--"foreign body". A classification is suggested on the basis of clinical characteristics and course of articular signs due to temporo-menisco-condylar stress resulting from occlusion problems, and concomitant lesions of the articular fibrocartilage: closed and open fibro-chondromalacia. Emphasis is placed upon the constant dissociation between articular clinical features and nosography. Spongialisation, or the property of regeneration of fibrocartilage from spongy bone tissue fully justifies the technique of condyloplasty to remodel the temporomandibular joints in the presence of fibro-chondromalacia. The future lies in the distinction between fibro-chondromalacia secondary to occlusive stress and that due to primary ischaemia of bone.