National Diploma in Dental Nursing Module 3- Part 1 Anatomy

Anatomy In this module you will learn about: 1. Structures of the oral cavity 2. The teeth – function, types, structure 3. Supporting structures of the teeth 4. Anatomy of the skull 5. Muscles of mastication and facial expression 6. Salivary glands 7. Nerve supply to head and neck region

1. Structures of the oral cavity The oral cavity or mouth is the first part of the gastrointestinal tract and the airway – the place where food and air enter the body

Structures of the oral cavity The oral cavity is surrounded by the cheeks (called Buccae in Latin) & the lips (called Labia in Latin) The upper or superior lip & the lower or inferior lip are attached to the gingiva by folds of soft issue called labial frenula Please note: 1 frenulum but many frenula The vestibule is the space between the cheeks/lips and the teeth

Structures of the oral cavity The palate forms the roof of the mouth & the floor of the nasal cavity (nose) The bony anterior part of the palate is called hard palate Palatine raphe is the midline of the palate The soft, mobile posterior part of the palate is called soft palate The uvula is a soft tissue projection of the soft palate and helps with the formation of some sounds

Structures of the oral cavity The palatine tonsils are part of the immune system and protect the body from disease Palatoglossal and palatopharyngeal arches are the border between the oral cavity and the pharynx (throat) The pharynx behind the mouth is called the oropharynx

Structures of the oral cavity The tongue (called Lingua in Latin and Glossa in Greek) is a muscular organ The tongue helps with: mastication (chewing), deglutition (swallowing), articulation (sound formation and taste sensation The tongue is attached to the floor of the mouth by the lingual frenulum

Structures of the oral cavity The gingiva or gums are part of the soft tissue lining the inside of the mouth The gingiva surrounds the teeth and forms a tight seal around them

2. The teeth Teeth are small calcified, whitish structures found in the jaws of humans and many other animals. In humans the teeth have the following functions: 1. To chew food during mastication 2. To help with sound formation during speech 3. To provide support for the jaws, cheeks and lips and so contribute to facial appearance

Tooth structure

Tooth structure The part of the tooth which is visible in the oral cavity is called the crown The neck of the tooth is the border between the crown and the root. The gingiva is attached to the neck of a tooth The roots are buried inside the alveolar bone of the jaws which keeps the teeth firmly in place

Crown Surfaces Pits and fissures – grooves 1. Labial surface is in contact with lips 2. Buccal surface is in contact with cheeks 3. Lingual surface is next to the tongue. 4. Palatal surface is next to the palate 5. Mesial surface is toward the midline 6. Distal surface is towards the back of the mouth 7. Incisal edge is the cutting edge of anterior (front) teeth 8. Occlusal surface is the chewing surface of the posterior (back) teeth Pits and fissures – grooves Cusps - pronounced elevations on the occlusal surfaces of a tooth terminating in a conical or rounded surface.

Tooth structure Enamel 1. Protective outer layer of crowns 2. Hardest substance in body – to withstand forces of chewing 3. Transluscent – yellowish colour of teeth is due to dentine 4. Produced by cells called ameloblasts 5. Composed of 96% inorganic matter – calcium & phosphorus in form of hydroxyapatite prisms. Prisms run at 90° to surface. 6. Prisms are held together by inter-prismatic substance 7. Has no nerve endings – insensitive to pain 8. Can not be repaired once destroyed by caries

Tooth structure 1. Forms bulk of crown & roots Dentine 1. Forms bulk of crown & roots 2. Protected by the much harder enamel 3. Harder than bone 4. Yellowish in colour 5. Produced by cells called odontoblasts which line the pulp cavity 6. Composed of dentinal tubules which contain nerve endings – sensitive to stimuli like temperature

Tooth structure Pulp 1. Found at the core of the tooth, under the dentine, in the pulp cavity. 2. Contains blood vessels, nerves and connective tissue. 3. Blood supply provides nutrients that keep the tooth alive. 4. Blood vessels & nerves enter the root through apical foramen 5. The part of pulp cavity located in the root is the root canal. 6. The root canals widen into the pulp chamber 7. pulp horns are extensions of the pulp chamber which point upward toward the cusps

The teeth Throughout their life humans have 2 sets of teeth 1. Deciduous dentition – the set of baby or milk teeth which erupt (appear in the mouth) when a baby is a few months old and are exfoliated (fall out) when the person reaches 12-13 years of age. 2. Permanent dentition – set of adult teeth which begin to replace the deciduous teeth when the person is around 6 years of age.

The teeth The teeth are arranged in 2 arches in the upper and lower jaws. The upper jaw is called the MAXILLA and so the upper teeth can also be called maxillary teeth The lower jaw is called the MANDIBLE and so the lower teeth can also be called mandibular teeth. In the deciduous dentition there are 10 teeth per arch In the permanent dentition there are 16 teeth per arch

Types of teeth in the two dentitions DECIDUOUS DENTITION PERMANENT DENTITION

Eruption dates of Deciduous Teeth TOOTH LETTER UPPER ERUPTION DATES in MONTHS LOWER ERUPTION DATES in MONTHS Central incisor A 10 8 Lateral incisor B 11 13 Canine C 19 20 First molar D 16 Second molar E 29 27

Eruption dates of Permanent Teeth TOOTH NUMBER UPPER ERUPTION DATES IN YEARS LOWER ERUPTION DATES IN YEARS Central incisor 1 7 -8 6-7 Lateral incisor 2 8-9 7-8 Canine 3 10-12 9-10 First premolar 4 9-11 Second premolar 5 10-11 First molar 6 Second molar 7 12-13 11-12 Third molar 8 18-25

Eruption of Permanent Teeth

Eruption of Permanent Teeth Permanent incisors and canines replace deciduous incisors & canines First premolars replace first deciduous molars Second premolars replace deciduous second molars First permanent molar erupts behind the deciduous teeth

Deciduous Teeth

Upper permanent central incisor

Upper permanent lateral incisor

Upper permanent canine

Upper permanent first premolar

Upper permanent second premolar

Upper permanent first molar

Upper permanent second molar

Upper permanent third molar (wisdom tooth)

Lower permanent central incisor

Lower permanent lateral incisor

Lower permanent canine

Lower permanent first premolar

Lower permanent second premolar

Lower permanent first molar

Lower permanent second molar

Lower permanent third molar (wisdom tooth)

Tooth roots Upper teeth with 1 root: Central and lateral incisors, canines, Second premolar Upper teeth with 2 roots: First premolar Upper teeth with 3 roots: First, second molars Lower teeth with 1 root: Central & lateral incisors, canines, first & second premolars Lower teeth with 2 roots Variable roots: Upper and lower third molars (wisdom ) teeth

Tooth cusps TOOTH NUMBER OF CUSPS Cuspid teeth – canines 1 cusp Bicuspid teeth – premolars 2 cusps Molars except upper and lower first molars 4 cusps Upper and lower first molars. The fifth cusp on the upper first molar is called the Cusp of Carabelli 5 cusps

The teeth The incisors and canines are the anterior or front teeth The premolars and molars are the posterior or back teeth. We always count the teeth starting with the teeth near the midline (central incisors) going backward. The midline is an imaginary line which divides the body in half

Differences between deciduous & permanent teeth Deciduous teeth : 20 in number Permanent teeth – 32 in number (there are no deciduous premolars and third molars) Deciduous teeth : Are much smaller Are whiter Have thinner enamel & larger pulp chambers Roots are more splayed & thinner Roots shorten with age

Supporting structures of the teeth The supporting structures of the teeth are collectively known as the periodontium. These structures surround and support the teeth, keeping them in the maxilla and mandible. The periodontium consists of: 1. alveolar bone 2. cementum 3. periodontal ligament 4. gingiva

Supporting structures of the teeth Alveolar bone The alveolar bone or alveolar process is the thickened ridge of bone that contains the tooth sockets. The alveolar process contains a layer of compact bone next to the periodontal ligament called lamina dura. The lamina dura is attached to the cementum by the periodontal ligament. The less dense bone forming the jaws is the spongy bone. Bone is made by cells called Osteoblasts Bone is resorbed (broken down) by cells called Osteoclasts

Supporting structures of the teeth Cementum 1. covers the dentine in the roots 2. produced by cells called cementoblasts 3. anchors the roots to the periodontal ligament 4. composed of cementocyte cells in a collagen matrix 5. meets the enamel at the neck of the tooth at the cemento-enamel junction (CEJ)

Periodontal ligament (PDL) 1. Made of collagen firers which connect cementum to lamina dura. 2. Acts as a shock absorber during chewing 3. Contains pressure sensors which tell the brain how much pressure is exerted on a tooth – brain tells us how hard to bite.

Supporting structures of the teeth Gingiva (gums) 1. Pink fleshy tissue covering the alveolar process. 2. Connected to underlying bone by gingival fibres. 3. Forms a tight seal around necks of teeth. 4. Gap between gingiva and neck of tooth is the gingival crevice or sulcus. 5. The interdental gingiva which fills the embrasures (interdental spaces) between the contact points of 2 teeth is the interdental papilla. 6. The contact point is the point at which the crowns of 2 neighbouring crowns touch.

Structures of periodontium Interdental or Interproximal space Structures of periodontium Interdental papilla Contact point Gingival sulcus/crevice Cementum Cementum Cementum Gingiva (gum) Periodontal ligament Periodontal ligament Periodontal ligament Cemento Enamel Junction (CEJ) Lamina dura Lamina dura Alveolar bone Furcation of roots

Healthy gingiva - Pink - Firm - Sharply pointed papillae - Gingival crevice is 2-3 mm deep - Do not bleed on probing Interdental papilla

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