Dental Anatomy - Skull and Oral Cavity PDF

Dental Anatomy - The Skull and Oral Cavity Objectives ▪ Identify parts of the skull, upper and lower jaws ▪ Differentiate between the movable and fixed bones of the skull ▪ Identify parts of the oral cavity Introduction Anatomy; Study of body structure Physiology; Study of body func...

Dental Anatomy - The Skull and Oral Cavity Objectives ▪ Identify parts of the skull, upper and lower jaws ▪ Differentiate between the movable and fixed bones of the skull ▪ Identify parts of the oral cavity Introduction Anatomy; Study of body structure Physiology; Study of body functions An underpinning knowledge of head and neck anatomy is needed for you to understand how abnormal functioning can effect dental health and create complications during treatment. We can split head and neck anatomy into: Skull and general features of the oral cavity Muscles Nerves Tooth structure and supporting structures Saliva These features all link together but first to look at is the skull (also referred to as the ‘cranium’). ©Tempdent 2021 Page 1 of 8 (04.21) The upper part it is hollow and acts to protects the brain like a shell. The frontal, parietal, temporal and occipital bones form this section of the cranium. Parietal bones Frontal Supraorbital Temporal foramen bones Orbital Nasal bones foramen Zygomatic arch Infraorbital foramen Maxilla Mental foramen Mandible The lower part forms the facial features including the jaws (further split into the maxilla and mandible). Foramen are holes (located all over skull) through which nerves and blood vessels pass. ©Tempdent 2021 Page 2 of 8 (04.21) The foramen magnum is a large foramen in the occipital bone which allows the spinal cord to pass from brain to body, which protects all the main nerves and blood supply to the rest of the body. Incisive Zygomatic foramen arch Hard palate Greater palatine foramen Foramen ovale Lateral pterygoid Medial pterygoid Foramen Temporal magnum Parietal Occipital The maxilla is the upper jaw which is fused as part of the cranium and so is fixed and immovable. It has thinner, more compact bone than the mandible and is made of two halves joined together in the hard palate. It also has an alveolar process (containing the upper teeth). The hard palate forms the roof of mouth and separates the nasal (nose) and oral cavity (mouth). ©Tempdent 2021 Page 3 of 8 (04.21) In the cranium are also hollow air spaces known as sinuses. These are in the frontal bone and also the maxilla. This is known as the maxillary sinus or maxillary antrum. It often becomes inflamed when the condition of sinusitis arises. As this space is just above the maxillary molars, pressure build up from inflammation, can be a cause for toothache. Parietal Frontal Nasal bones Zygomatic bone Maxilla Temporal Occipital External acoustic meatus Body of the Angle of the Ramus of Sphenoid mandible mandible the mandible The zygomatic arch is the name for the cheekbone and is formed by the maxilla, zygoma and temporal bone. ©Tempdent 2021 Page 4 of 8 (04.21) The mandible is the name given to the lower jaw. It is unusual because it is the only bone in the cranium that can move. The horizontal part of the mandible is known as the body which contains the lower alveolar processes. The vertical part is known as the ramus. The junction where the ramus and body meet is known as the angle. The external oblique line is the ridge on outer surface of body and forms the base of the alveolar process. The mylohyoid line is on the inner surface of body and marks the floor of mouth. At top of ramus is the coronoid process which is the front projection and behind this is the condyle. They are separated by sigmoid notch. Coronoid Mandibular Head of the process foramen condyle Sigmoid notch Lingula Neck of the condyle Mylohyoid line Ramus of the mandible Mental Angle of the protuberance mandible (chin) Mental Body of the External foramen mandible oblique line ©Tempdent 2021 Page 5 of 8 (04.21) The condyle and temporal bone, at the base of the skull, form the TMJ (temporo- mandibular joint) which is responsible for the lower jaw movements. When the mouth is at rest, the condyle lies in a hollow area of the temporal bone known as the glenoid fossa. Temporal bone Meniscus ead of the Glenoid Condyle fossa Articular eminence Sigmoid notch Coronoid process As the mouth is opened wider, the condyle slides forward to reach tip of glenoid fossa called the articular eminence. It is possible for the condyle to get stuck in front of the articular eminence and therefore the mouth is unable to close. The jaw is then said to be dislocated. The bones are covered by thick cartilage and are surrounded by several ligaments. There are no nerves or blood vessels in this connective tissue, however there is synovial fluid, which is sticky and thick. This is a disc called the meniscus. The function of this fluid (which is generally found in the joints of bones) is to bathe these bone structures, providing them nourishment. It also lubricates the bones therefore enabling them to glide over each other. When food is being chewed (mastication), the condyle moves backwards and forwards as well as side to side. To enable this process to occur we need the muscles of mastication. ©Tempdent 2021 Page 6 of 8 (04.21) TMJ problems are varied and common. They can occur in the form of a tender jaw, clicking, creaking and grinding sound (crepitus), headaches, restricted movement or even earache and toothache. It is most common in young women or people with a lot of stress is down to bruxism (teeth grinding) for which the treatment is tranquilizers or occlusal splints. There is also the condition known as trismus which is a protective spasm of the muscles of mastication. This can occur in acute inflammatory conditions such as pericoronitis or following a long period of time with an open mouth. Crepitus indicates damage to the TMJ due to degenerative changes such as wear and tear to the disc, causing bone to bone contact of the mandibular condyle with the joint socket. Injury to the disc or its posterior attachment resulting in crepitus can be caused by chronic (long term) TMJ disorders due to bruxism (parafunctional habits), rheumatoid arthritis, malocclusion, postural problems or acute trauma. Inside the mouth are the soft tissues (skin) which are known as the mucous membrane. There is the buccal sulcus, which is the space between teeth and cheek as well as the soft palate which is attached to the back of hard palate and seals the nose from the mouth when swallowing. ©Tempdent 2021 Page 7 of 8 (04.21)  Labial Lips Frenum Incisive Rugae foramen Hard palate Pharyngeal arch Soft palate Labial Uvula commissure Taste buds Tonsils Mucous Tongue membrane Alveolar mucosa Lingual Gingiva frenum This also contains the uvula which is the dangly tissue at back of soft palate. There is also the tongue which is a thick and strong muscular organ. It is attached to floor of mouth by the lingual frenum. It is responsible for speech, taste, cleansing and swallowing. The upper surface is rough and thick as it contains the taste buds (enables us to distinguish between sweet, salty and sour foods/drinks) and the lower surface of tongue is much thinner which makes it easy to absorb drugs. Inflammation and soreness of tongue is known as glossitis and can occur with anemia, vitamin B deficiency or hormone problems. ©Tempdent 2021 Page 8 of 8 (04.21)