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It is essential that dental students and practitioners understand the structure and function of the temporomandibular joints and the muscles of mastication and other muscle groups that move them. The infratemporal fossa and pterygopalatine fossa are deep to the mandible and its related muscles; many of the nerves and blood vessels supplying the structures of the mouth run through or close to these areas, therefore, knowledge of the anatomy of these regions and their contents is essential for understanding the dental region. The temporomandibular joints (TMJ) are the only freely movable articulations in the skull together with the joints between the ossicles of the middle ear; they are all synovial joints. The muscles of mastication move the TMJ and the suprahyoid and infrahyoid muscles also play a significant role in jaw movements. The articular surfaces of the squamous temporal bone and of the condylar head (condyle) of the mandible form each temporomandibular joint. These surfaces have been briefly described in Chapter 22 on the skull and Figure 24.1A indicates their shape. The concave mandibular fossa is the posterior articulating surface of each squamous temporal bone and houses the mandibular condyle at rest. The condyle is translated forwards on to the convex articular eminence anterior to the mandibular fossa during jaw movements. The articular surfaces of temporomandibular joints are atypical; they covered by fibrocartilage (mostly collagen with some chondrocytes) instead of hyaline cartilage found in most other synovial joints. Figures 24.1B and 24.1C show the capsule and ligaments associated with the TMJ. The tough, fibrous capsule is attached above to the anterior lip of the squamotympanic fissure and to the squamous bone around the margin of the upper articular surface and below to the neck of the mandible a short distance below the limit of the lower articular surface. The capsule is slack between the articular disc and the squamous bone, but much tighter between the disc and the neck of the mandible. Part of the lateral pterygoid muscle is inserted into the anterior surface of the capsule. As in other synovial joints, the non-load-bearing internal surfaces of the joint are covered with synovial membrane.

A child’s future perceptions and expectations are likely to be conditioned by early experiences of dental treatment. Just under half of all children report low to moderate general dental anxiety, and 10–20% report high levels of dental anxiety. Montiero et al. (2014) indicate that the prevalence of needle phobia may be as high as 19% in 4- to 6-year-olds. Davidovich et al. (2015) reflected that, for general practitioners and specialists alike, Local anaesthetic (LA) injection for an anxious child was the most stressful procedure regardless of the operator’s age, gender, or years of professional experience. Despite impressive reductions in caries in children in recent years, there still exists a social gradient with inequalities in experience of dental disease, and there remains a significant cohort of children for whom extractions and restoration of teeth are necessary. Aside from emerging restorative strategies that do not require LA (e.g. atraumatic restorative technique or placement of preformed metal crowns using the Hall technique), effective and acceptable delivery of LA remains an important tool to enable successful operative dental treatment to be carried out comfortably for child patients. Effective surface anaesthesia prior to injection is very important as a child’s initial experience of LA techniques may influence their future perceptions and help in establishing trust. Cooling tissues prior to injection has been described but is rarely used, and surface anaesthesia is generally achieved with intra-oral topical agents. Although the main use of topical agents is as a pre-injection treatment, they have been used as the sole means of anaesthesia for some procedures including the extraction of mobile primary teeth. It is possible to achieve a depth of 2–3mm of anaesthesia if topical agents are used correctly: • the area of application should be dried • topical anaesthetic agent should be applied over a limited area • the anaesthetic agent should be applied for sufficient time. In the UK 5% lidocaine (lignocaine) and 18–20% (17.9%) benzocaine gels are the most commonly used agents. Benzocaine topical anaesthetic gel is not recommended for use on children under 2 years old because of an increased risk of methaemoglobinaemia.