Pierre Carpentier

Insertions of the lateral pterygoid muscle: An anatomic study of the human temporomandibular joint

The objective of this investigation was to evaluate the anatomic relationships of the lateral pterygoid muscle with the disc-condyle complex using an acrylic embedding technique to obtain anatomic serial cuts of a solid block containing the temporomandibular joint (TMJ) and the neighboring structures. The fibers of the upper and lower heads were found to be fused in front of the TMJ and to constitute medially a strong muscular wall. The lateral third of the anterior band of the disc was free of any muscle insertions and related anteriorly with loose connective tissue; the middle third showed fibers that run under the anterior band of the disc and attached in the upper part of the condylar fovea. Only the medial portion demonstrated both fibers running into the disc and fibers inserting into the bone. The fibers inserted into the bone run under those attached into the disc and terminated below the medial pole of the condyle binding the disc tightly over the medial pole. This study demonstrates that the main insertions of the superior head are not into the disc but into the condyle. Considering the anatomic organization of the upper head, the explanation of anterior displacement of the disc due to a spastic activity of this muscle alone is not probable. Hypotonicity, not hyperactivity, of the upper head may contribute to an anterior and medial disc displacement.

MR of 732 TMJs: anterior, rotational, partial and sideways disc displacements

OBJECTIVE The purpose of this study was to determine the prevalence of anterior, sideways, rotational and partial anterior disc displacements, as well as degenerative changes in patients with clinical signs and symptoms of internal disorders. MATERIALS AND METHODS 732 MR Images of temporomandibular joints (TMJ) were produced for 366 symptomatic patients. Image analysis included assessment of disc positions and mobility, as well as recapture in coronal and mediolaterally divided sagittal planes in closed and open positions. RESULTS Of these images, 545 TMJ showed an internal derangement comprised of 52% anterior disc displacements without reduction, 26% anterior disc displacements with reduction, 11% partial anterior disc displacement, 5% pure sideways displacements and 4% stuck discs. Rotational disc displacements were observed in 34% of the anterior disc displacements without reduction group and in 53% of the anterior disc displacements with reduction group. A total of 97% of the partial anterior disc displacement occurred laterally. Degenerative changes increased with age, mainly in the anterior disc displacements without reduction group. CONCLUSION Magnetic resonance imaging (MRI) investigations show that the disc is subject to a great variety of displacements and that there is a need for further research to refine the clinical therapy for TMJ internal derangements.

Kinetic magnetic resonance imaging analysis of swallowing: a new approach to pharyngeal function

The emergence of turbo-FLASH MR sequences allows us to acquire five 10-mm sections each second and thus to catch images of the soft tissues during function. One can trace the pathway of a liquid between the tongue, the soft palate, the epiglottis and the pharyngeal apparatus and analysis the role of the anatomic structures during swallowing. Restricted to the sagittal plane for the purpose of this preliminary study, this technique can be extended to the other planes to provide a three-dimensional analysis of oropharyngeal function or dysfunction.

Innervation of the human lateral pterygoid muscle

The one- or two-headed arrangement of the lateral pterygoid m. (LPM) was analysed by studying the motor nerve distribution within the muscular tissue. In all subjects, the main innervation of the lateral pterygoid m. came from the anterior trunk of the mandibular n. by one to three nerves. These nerves divided into five or six vertical branches which ramified into parallel horizontal tiny fibers. Consequently, the lateral pterygoid m. appeared to be divided into oblique sagittal planes and horizontal layers by the nerve branches, reflecting the multipennate organisation of the muscle. These layers can be selectively recruited during mandibular movements, ensuing a fine medial-lateral control. According to its nerve supply, the LPM has to be considered as a single unit made of independent functional musulo-aponeurotic layers even though its morphologic conformation is in one, two or three heads.

Anatomic and mechanical properties of the lateral disc attachment of the temporomandibular joint

PURPOSE This study measured the strength to failure of the human temporomandibular joint (TMJ) lateral disc attachment (LDA) using a tension-compression machine. These data were correlated with the LDA location and its morphologic aspects, the age and sex of the subjects, and the amount of the lateral pterygoid muscle (LPM) inserted in the disc. METHODS Forty-two TMJs without any obvious internal damage were carefully dissected to preserve the LDA. The width of insertion of the lateral pterygoid muscle fibers in the anterior band, as well as the width of the disc, were measured. The tension test was performed until the complete failure of the sample using a screw machine. RESULTS Two types of LDA were recognized. In LDA 1, the anterior and posterior bands lateral disc junction were directly inserted on the lateral pole, whereas in LDA 2 this lateral junction was attached behind and below the pole through a sheet of fibrous tissue. The breaking points for LDA 1 (55.8 N) and LDA 2 (28.8 N) were significantly different (P = .03). No correlation was found between the amount of LPM discal fibers insertion, sex, age, or the LDA breaking strength point. CONCLUSION The LDA 2 insertion strongly suggests that the lateral joint ligament together with the capsule may act as a substitute for the original disc attachment to the lateral pole of the condyle.

Temporomandibular Joint Serial Sections Made with Mandible in Intercuspal Position

This article presents a method for preparing block sections of the human temporomandibular joint. The purpose of the study was to examine the relationship of the temporomandibular joint components without disturbing the anatomic arrangement of the parts. The mandibles of seven fresh cadavers were locked into a specific occlusal position (intercuspal) throughout all procedures. An acrylic embedding technique allowed serial sections in any plane without displacement or tearing of mineralized and soft tissues. Photographs were obtained using an Olympus transmitted light microscope with various magnifications from 1 X to 40 X.

Anatomy of the Temporomandibular Joint and Related Structures in the Frontal Plane

Conclusions about the anatomy and physiology of the temporomandibular joint have too often been based on sagittal representations. The aim of the article is to describe frontal serial cuts of an acrylic embedded articulation of a subject with teeth in intercuspal position. The frontal plane is best to visualise the difference between lateral and medial aspects of structures such as the disk-condyle-complex, the articular capsule, and related muscles.