Introduction to the Masticatory System and Dental Occlusion (eBook)

Dinesh Rokaya (Autor)

eBook Download: EPUB

2024
350 Seiten
Wiley-Blackwell (Verlag)
978-1-119-88420-0 (ISBN)

Infos

A comprehensive introduction to the masticatory system and its relation to dental occlusion

Introduction to the Masticatory System and Dental Occlusion meets the need for a rigorous guide to the masticatory system and how it relates to dental occlusion to aid interventions. The text offers a sound understanding of functioning dental anatomy and the biomechanics that are essential to understanding dental occlusion. It covers all structures required for chewing: jaws and jaw muscles, teeth, joints, and tongue as well as other significant areas including the vascular and nervous systems that supply these structures with blood and stimulation. Beginning with the understanding of these concepts, the author provides further guidance on oral function, esthetics, and alerting patients to potential issues.

Introduction to the Masticatory System and Dental Occlusion readers will also find:

• A thorough introduction to the basic structure and function of the masticatory system
• Detailed coverage of subjects including TMJ, mastication muscles, occlusal therapy, and more
• Images to illustrate key concepts and systems
• Advice on choosing the correct medical intervention in each case

Introduction to the Masticatory System and Dental Occlusion is ideal for undergraduate and postgraduate dental students for subjects such as masticatory systems, dental anatomy, restorative dentistry, and prosthodontics, as well as for practicing dentists and medical professionals in related fields.

The Author

Dinesh Rokaya, PhD is a Visiting Professor at the Faculty of Dentistry, Chulalongkorn University, Bangkok, Thailand.

Textauszug

1
Structures and Functions of Masticatory System

1.1 Introduction

The masticatory system consists of teeth, muscles, ligaments, bones, and joints, which are responsible for functions of the masticatory system, i.e. mastication, speech, swallowing, and speaking. The system also assists in breathing. It is regulated and coordinated by the neurologic controlling system. The musculature aids in specific motion of the mandible and effective teeth movement during function. To study occlusion, explicit knowledge of biomechanics and functional anatomy of mastication is crucial.

1.2 Structures and Functions of Temporomandibular Joint

The temporomandibular joints (TMJs) are synovial joints and movable articulations in the skull [1, 2]. The muscles of mastication along with the suprahyoid and infrahyoid move the TMJ and play a crucial part in jaw movements. The basic components of the TMJ include (Figures 1.1 and 1.2) the mandible (head of the condyle), disc, temporal bone (glenoid fossa and articular eminence), and the capsule surrounding the TMJs.

1.2.1 Articular Surfaces

Each TMJ is formed by the mandible's condylar head and squamous temporal bone's articular surfaces. Mostly, the synovial joints are shielded by the hyaline cartilage; however, the articular surfaces of TMJs are shielded by fibrocartilage (predominantly collagen accompanied by few chondrocytes), which makes them atypical [3, 4]. During jaw movements, the condyles translate forward onto the convex articular eminence.

1.2.2 Ligaments

The ligaments are mainly built from collagenous connective tissue fibers of distinct lengths. Normally, they are nonstretchable, but they can be elongated if extensive forces are applied. Ligaments control the movements of the border. The three major functional ligaments of the TMJ are the collateral, capsular, and temporomandibular ligaments (TMLs) [1, 5]. The accessory ligaments are two in number: sphenomandibular and stylomandibular.

Figure 1.1 Left temporomandibular joint (TMJ) showing the condyle, disc, glenoid fossa, and articular eminence of the temporal bone. Image taken from the Anatomage Table (Anatomage Inc., California, USA).

Figure 1.2 Diagram of the right temporomandibular joint (TMJ) sagittal section showing the various components.

1.2.2.1 Collateral (Discal) Ligaments

The other name for collateral ligaments is discal ligaments. These are the true ligaments that comprise fibers of collagenous connective tissue and are nonelastic. These ligaments divide the joint mediolaterally into the inferior and superior joint cavities. The articular disc (lateral and medial borders) is linked to the condyle by the collateral ligaments. The medial discal ligament connects the medial pole of the condyle from the medial edge of the disc, and the lateral discal ligament connects the lateral pole of the condyle from the lateral edge of the disc (Figure 1.3) [1]. During glides of the condyle anteriorly and posteriorly, passive movement with the condyle is permitted by them. Moreover, the anterior and posterior disc rotation on the condyle's articular surface is allowed by them. Hence, they are beneficial for the hinge motion of the TMJ that happens between the articular disc and the condyle.

Figure 1.3 Anterior view of the temporomandibular joint (TMJ).

Adapted from Reference [1]; chapter published in Management of Temporomandibular Disorders and Occlusion, 7th edition, Okeson J.P., Functional Anatomy and Biomechanics of the Masticatory System, page 10, Copyright Elsevier (2013).

1.2.2.2 Capsular Ligament

The capsular ligament incorporates the entire TMJ (Figure 1.4) [1]. Superiorly, the capsular ligament's fibers are connected to the temporal bone through the mandibular fossa's articular surfaces and the articular eminence. Inferiorly, the capsular ligament's fibers are connected to the condylar neck. The function of this ligament is to withstand all the forces arising medially, laterally, or inferiorly, which might result in the separation or dislocation of the articular surfaces. This ligament also helps retain the synovial fluid.

1.2.2.3 Temporomandibular Ligament

The strengthened capsular ligament builds the temporomandibular (TM) or the lateral ligament with the help of strong tight fibers. The TML consists of an inner horizontal portion and an outer oblique portion (Figure 1.4A) [1]. The inner horizontal portion stretches from the zygomatic process and articular tubercle horizontally to the condyle's lateral pole and the articular disc's posterior part. The outer oblique portion stretches from the articular tubercle and zygomatic process to the neck of the condyle.

Figure 1.4 Ligaments of the temporomandibular joint. A, Temporomandibular ligament showing the outer oblique portion and the inner horizontal portion. B, Stylomandibular ligament and sphenomandibular ligament.

Adapted from Reference [1]; chapter published in Management of Temporomandibular Disorders and Occlusion, 7th edition, Okeson J.P., Functional Anatomy and Biomechanics of the Masticatory System, page 10–11, Copyright Elsevier (2013).

1.2.2.4 Sphenomandibular Ligament

The sphenomandibular ligament is one of the accessory ligaments of the TMJ (Figure 1.4B) [1], which emerges from the sphenoid bone's spine and descends to the mandibular ramus’ lingula [6]. This ligament has no crucial function in mandibular movement limitation.

1.2.2.5 Stylomandibular Ligament

The stylomandibular ligament is another accessory ligament of the TMJ (Figure 1.4B) [1], which emerges from the styloid process and descends downward and forward to the mandibular angle and posterior border of the ramus. The uncontrolled protrusive mandibular motions are limited by the stylomandibular ligament. This ligament becomes tense while protruding the mandible and relaxes while opening the mandible.

1.2.3 Nerve Innervation of the Temporomandibular Joint

The trigeminal nerve innervates the TMJ and supplies sensory and motor innervation to the muscles that regulate it. The afferent innervation is supplied by the mandibular nerve branches. Most of the innervation is supplied through the auriculotemporal nerve while it branches off the mandibular nerve. Masseteric and deep temporal nerves provide supplemental innervation [7].

1.2.4 Blood Supply of the Temporomandibular Joint

The principal arteries of the TMJs are composed of the middle meningeal artery anteriorly, the superficial temporal artery posteriorly, and the internal maxillary artery inferiorly. The deep auricular, ascending pharyngeal, and anterior tympanic arteries are the additional crucial vessels. The “feeder vessels” that by a direct route get into the head of the condyle both anteriorly and posteriorly and the inferior alveolar artery through marrow spaces are the routes through which the condyle acquires its vascular supply [8].

1.2.5 Functions of the Temporomandibular Joint

The function of the TMJ is based on the articular design, neuromuscular control, and integrity of soft tissue elements that comprise the anatomy [9]. The prime function of the TMJ is to facilitate movements of the lower jaw. This joint allows a range of movements of the lower jaw, i.e. translational movements (protrusion, retraction, and lateral deviation) and rotational movements (elevation and depression) [2, 9].

1.2.6 Clinical Evaluation of the Temporomandibular Joint

The clinical evaluation of the TMJ includes the observation of the symmetry of the face and the various movements of TMJ. In patients with TMJ dysfunction, it will result in an asymmetry of the mandibular branch.

Pain and clicking are recorded at specific degrees of articular opening or closing, along with accessory movements. The muscles are palpated (externally and internally) and the presence of enlarged submandibular lymph nodes is also checked by palpation. The jaw is slowly moved to evaluate the TMJ ligament apparatus. The fingers are placed on the joint while the patient opens his mouth to evaluate the TMJ. The maximum opening of the mouth should also be evaluated [10].

1.2.7 Radiographic Examination of the Temporomandibular Joint

Various instruments are used in the assessments of the TMJs, and they play a vital role in the diagnosis. Hence, it is necessary to do a proper assessment using instruments before taking a therapeutic approach to a TMJ in the dysfunction [11]. Various imaging techniques for the TMJ include panoramic radiography, plain radiography (transcranial projection), computed tomography or cone‐beam computed tomography, and magnetic resonance imaging (Figure 1.5) [12–14]. Panoramic radiography (Figure 1.5A) is important in the evaluation of the mandibular condyles to the glenoid fossa relationship. Plain radiography of the TMJs (Figure 1.5B) using...

Produkt-Details

• Erscheint lt. Verlag: 23.10.2024
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie ► Gesundheitsfachberufe
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete
• Themenwelt: Medizin / Pharmazie ► Zahnmedizin
• Schlagworte: Biofilm • bio-surfactant • Enzyme • exopolysaccharide • Genetic Engineering • hazardous contamination • hazardous pollutant • indigenous microbe • metabolite • Microbial Bioremediation • microbial product • microbial synthesized nanoparticle • Novel microbe
• ISBN-10: 1-119-88420-9 / 1119884209
• ISBN-13: 978-1-119-88420-0 / 9781119884200