Head and Neck Anatomy Lecture #2: Tooth Functions and Terms PDF

Head and Neck Anatomy Lecture # 2 The Tooth: Functions and Terms Functions of Teeth Teeth are important in acquiring and chewing food, aiding in the process of digestion by breaking down food and by forming a hard physical barrier to protect the oral cavity Teeth function in speech...

Head and Neck Anatomy Lecture # 2 The Tooth: Functions and Terms Functions of Teeth Teeth are important in acquiring and chewing food, aiding in the process of digestion by breaking down food and by forming a hard physical barrier to protect the oral cavity Teeth function in speech and are important for esthetics Teeth support the facial musculature Crown and Root  Each tooth has a crown and root portion  Crown is covered with enamel and root is covered with cementum  Root and crown are joined at the cementoenamel junction (cej)  The line formed at this junction is also known as the cervical line  Crown portion of a tooth erupts through bone and gum (gingival) tissue The anatomic crown is the part of the tooth covered with enamel The clinical crown is that part of the crown visible above the gingiva Root Morphology Teeth may exhibit a single root, or multiple roots with a bifurcation (two roots) or trifurcation (three roots) Each root has one apex or terminal end The portion of jaw bone that supports the teeth is called the alveolar process Tooth Tissues: enamel, dental, cementum and pulp Enamel – forms outer surface of anatomic crown Thickest at tip (apex) of crown Colour varies with mineralization and thickness Most densely mineralized tissue with 96% inorganic and 4% organic matter and water Enamel is durable and resistant to wear Harsh acids, bacteria and severe grinding can wear away enamel Dentin  Forms the bulk of the tooth  Wrapped in an envelope of enamel and cementum  Softer than enamel, yellower in colour  70% inorganic and 30% organic matter  Dentin is capable of adding to itself with the formation of secondary dentin  In response to cavities or trauma dentin forms reparative dentin Cementum A very thin bone like substance which covers the root Provides a place for the attachment of the tooth to the alveolar bone via the periodontal ligament fibers Composed of 45 – 50% inorganic and 50 – 55% organic components making it ‘softer’ than dentin and enamel Acellular cementum covers the entire anatomic roots and cellular cementum covers the apical third of the root Dental Pulp  The nourishing, sensory and dentin-reparative system of the tooth  Anatomically divided into pulp chamber and pulp canals  Pulp chamber is housed within the coronal (crown) portion of the tooth  Pulp canals are located within the roots of the tooth  Pulp horns extend into the cusps of the teeth Types and Functions of Teeth  Humans may eat both meat and plants (omnivores)  To accommodate this variety in diet, teeth vary in size, shape and location in the arch  Teeth are designed for cutting, tearing, and grinding (mastication) of different types of food  The permanent dentition contains central and lateral incisors, canines, first and second premolars and first, second and third molars Incisor Teeth  single-rooted teeth with a relatively sharp and thin edge  biting edge is called incisal edge  located at the front of the mouth  they are designed to cut food without the application of heavy forces  incisor means “that which makes an incision, or cut”  the tongue side, or lingual surface, is shaped like a shovel to aid in guiding the food into the mouth. Canine Teeth  located at the "corner" of the arch  designed for cutting, holding, grasping and tearing food  canines have the longest root and are the most stable teeth  because of its sturdy crown, long root, and location in the arch, the canine is referred to as the cornerstone of the dental arch Premolar Teeth  there are four maxillary and four mandibular premolars in the permanent dentition  there are no premolars in the primary dentition  the premolars may exhibit 2 or 3 cusps  the pointed buccal cusp holds the food while the lingual cusps grind it  premolar crowns are shorter than canines and they exhibit a wide surface for grinding food Molar Teeth  there are six maxillary and six mandibular molars in the permanent dentition  there are 4 maxillary and 4 mandibular molars in the primary dentition  molars are larger than premolars, having 4 or more cusps  the function of the molars is to chew (masticate) or grind up food  maxillary and mandibular molars differ greatly from each other in shape, size, number of cusps and roots  Tooth Surfaces Each tooth has five surfaces named according to the direction they face 4 1. Facial 5 2. Occlusal (Incisal for ant teeth only) 3. Lingual (palatal for maxillary arch only) 3 4. Mesial 5. Distal 2 1 Tooth Surfaces 1. Facial surface: surface closest to the face Facial surface closest to the lips are also called labial surface Facial surface closest to the cheek are also called buccal surface 2. Occlusal surfaces: chewing surface of posterior teeth - Incisal surfaces: biting edge or surface of anterior teeth 3. Lingual surfaces: surface closest to the tongue Lingual surfaces of upper teeth may also be called palatal surface 4. Mesial surfaces: surface of the tooth toward the midline 5. Distal surfaces: surface of the tooth distant or away from the midline Surfaces of the teeth.  1 2 3 5 4 8 6 7 Tooth Surfaces  when teeth are adjacent to each other in the arch the surfaces which contact each other are called proximal surfaces (mesial and distal)  the area between adjacent tooth surfaces is called the interproximal space  where surfaces meet the names are combined eg. mesioincisal, distolingual Dividing the Tooth into Thirds To help in identifying various areas within a specific surface of a tooth the root and crown of the tooth can be divided into thirds vertically and horizontally