The structures of the maxilla and mandible discussed in this section are illustrated in Fig 1-12. The oral vestibule (vestibulum oris) is the space between the cheeks and lips laterally and the teeth, gingiva, and the alveolar region medially. Usually the tissue surfaces lie close together so that the space in between is only potential in nature. An actual space can be produced if the cheeks are puffed out or pressed in when chewing food.
The oral cavity is the space between the orifice of the mouth and the isthmus of the fauces (isthmus faucium; also called the oropharyngeal isthmus) (Fig 1-11). The
alveolar processes, which bear the teeth, divide the oral cavity into the oral vestibule (vestibulum oris) and the oral cavity proper (cavi-tas oris propria), the mucosa of which is covered by stratified squamous epithelium.
The proportions of the face and head can be measured cephalometrically. Cephalometry is the science of measuring the skull. Cephalometric points and reference lines are used in profile analysis during orthodontic examination. This facilitates analysis of the maxillofacial relationship and determination of the position of the teeth in the jaws and the relationship of the dental arches.
The human face (facies) can be divided into three areas by the interpupillary line (a line through the pupils with the eyes looking straight ahead; see Fig 1-10) and a line through the oral aperture:
The masticatory system, or orofacial system (system of mouth + face system; in Latin, os = mouth, facies = face; facial = relating to the face), includes all the different types of tissue that are involved in the chewing process.The stomatognathic system, as the masticatory system is also called, is not described as an organ unit according to the biologic descriptive model but as a unit with functionally coordinated tissue structures.
Terms that denote direction and position are standardized in anatomical nomenclature so that all the positional descriptions of areas of the human body can be located by reference to specific planes and directions. In dentistry, these systems of reference can be used, for example, to fit a row of teeth into the geometry of the skull. To locate the position of parts of the body or organs, the human body can be divided into four principal planes and three main axes (Fig 1-3).
Trunk, head, and neck
The trunk (truncus) comprises the chest, abdomen, and pelvis. The posterior region of the trunk is known as the back (dorsum). The upper region of the trunk, the chest (thorax), is formed from the bony rib cage, which protects the lungs.The chest cavity (cavitas thoracis) is separated from the abdominal cavity below by the diaphragm. The abdomen describes the area between the thorax and the pelvis, its bony structure being formed by the lumbar spine. The abdominal cavity (cavitas abdominalis) contains the abdominal viscera, which are bordered by the peritoneum. The lower part of the trunk, the pelvis, contains the pelvic organs and connects the trunk to the lower extremities.
Skilled dental technicians should have a fundamental medical knowledge, which will enable them to produce functional dental prostheses. In dentistry, prosthetic work is objectively assessed using criteria based on the form and function of anatomical tissue structures. Anatomy is therefore a primary discipline for dental technicians.
Orthodontic movement is the response to force applied on teeth through braces, wires, elastics, modules, elastic bands, coils. The process occurs in this manner: when a Force is applied on the tooth, it moves inside the alveolar socket, this provokes the stretching of some
periodontal fibers and the compression of other fibers.
When we use reverse curves to level a deep curve of Spee, we find that the intrusive forces exercised in the anterior and posterior sectors are balanced with the extrusive forces that are exercised in the premolar region. Another effect is that the intrusive forces are going to provoke at the molar level a positive torque and a distal inclination of the crowns and a mesial movement of their roots; on the other hand the intrusive forces exercised at the incisor level will provoke a buccal movement of these (positive torque].