Teeth with Anatomical Structure || Dental Cavities & Plaque
Teeth
The teeth are a group of hard organs found in the oral cavity. We use teeth to masticate (or chew) food into tiny pieces. They also provide shape to the mouth and face and are important components in producing speech.
A tooth can be divided into two main parts: the crown and root. Found above the gum line, the crown is the enlarged region of the tooth involved in chewing. Like an actual crown, the crown of a tooth has many ridges on its top surface to aid in the chewing of food. Below the gum line is the region of the tooth called the root, which anchors the tooth into a bony socket known as an alveolus Roots are tapered structures resembling the roots of plants, and each tooth may have between one to three roots. The exterior surface of the root is covered in a bone-like mixture of calcium and collagen fibers known as cementum. Cementum provides grip for the periodontal ligaments that anchor the root to the surrounding alveolus.
Anatomy of the Tooth
The teeth are a group of hard organs found in the oral cavity. We use teeth to masticate (or chew) food into tiny pieces. They also provide shape to the mouth and face and are important components in producing speech.
A tooth can be divided into two main parts: the crown and root. Found above the gum line, the crown is the enlarged region of the tooth involved in chewing. Like an actual crown, the crown of a tooth has many ridges on its top surface to aid in the chewing of food. Below the gum line is the region of the tooth called the root, which anchors the tooth into a bony socket known as an alveolus. Roots are tapered structures resembling the roots of plants, and each tooth may have between one to three roots. The exterior surface of the root is covered in a bone-like mixture of calcium and collagen fibers known as cementum. Cementum provides grip for the periodontal ligaments that anchor the root to the surrounding alveolus.
Each tooth is an organ consisting of three layers: the pulp, dentin, and enamel.
Teeth are classified into four major groups: incisors, canines, premolars, and molars.
Babies are born without teeth, but grow a temporary set of twenty deciduous teeth (eight incisors, four canines, and eight molars) between the ages of six months and three years. Baby teeth fill the child’s tiny jaws and allow the child to chew food while larger, stronger adult teeth develop inside the mandible and maxilla bones. At about six years of age the deciduous teeth are slowly shed one at a time and replaced by permanent adult teeth.
Adult teeth develop while hidden within the maxilla and mandible after the deciduous teeth have erupted. When an adult tooth erupts, it triggers the roots of the deciduous tooth above it to atrophy. This causes the baby tooth to become loose and eventually fall out. The new permanent tooth slowly pushes up through the gums to replace the baby tooth. Eventually, a total of thirty-two permanent adult teeth form and erupt. The adult teeth are arranged in both the upper and lower jaws from the midline of the mouth as follows: central incisor, lateral incisor, canine (cuspid), first premolar (bicuspid), second premolar, first molar, second molar, and third molar.
The first twenty-eight adult teeth are fully erupted by the age of eleven to thirteen with the third molars, known as wisdom teeth, erupting in the back of the jaw several years later in early adulthood. Sometimes the wisdom teeth become impacted when they grow and become wedged at an abnormal position in the jaws and fail to erupt. In some cases there is not enough room in the jaw to accommodate a third set of molars. In both cases the wisdom teeth are surgically removed, as they are not needed to properly chew food.
Mastication, or chewing, is the main function of the teeth. The teeth are aligned in the jaws so that the peaks of one tooth align with the valleys of its counterpart on the other jaw. Every bite forces food into the interface of the teeth to be chopped, while lateral motion of the jaw is used to grind food in the premolars and molars.
Tooth decay and cavities are important health concerns related to the teeth. The enamel that covers the crown in each tooth can be broken down by acids produced by bacteria that live in the mouth and assist in digestion of small bits of food. This process of enamel erosion by acids is called decay. To prevent decay, good oral hygiene, consisting of daily brushing and flossing, is necessary. Decay can eventually lead to cavities, also known as dental caries, where holes appear in the enamel and expose the dentin. Cavities require medical intervention to prevent their growth, usually resulting in the removal of the affected tissue and the filling of the cavity with a hard material to restore the strength and function of the tooth.
Dental Cavities
Different Dental Cavities
Dental cavities are caused by tooth decay. There are essentially three causes for tooth decay: (1) bacteria in the mouth; (2) food for bacteria, and (3) susceptibility to decay such as heredity or age. Tooth decay is a gradual process that ordinarily begins with the outer layer of enamel and then penetrates into the dentin and perhaps even on into the pulp.
There is a general consensus that the process of decay begins with plaque formation. Plaque is food debris and their products, which form a sticky, concentrated film that adheres to the teeth. Decay usually begins with a small-pitted area on the surface of the bone that enlarges to create a soft spot of partially dissolved enamel. This stage of decay is usually painless. The process is kept alive by the addition of sugar in our food that promotes bacterial growth. The longer this process is untreated, the greater the rate of destruction until the decay reaches the dentin, the main substance of the tooth. Dentin is part mineral and part living cells, and decay spreads much faster in dentin than in enamel, and will enlarge forming a cavity.
Inflammation of the pulp of the tooth that contains living cells, nerves, and blood vessels, produces pain. Survival of the tooth is critical at this stage, and prolonged irritation or inflammation of the tooth may cause its death, or it may lead to abscess formation, a severely inflamed, hollow area under the root. This may require tooth extraction. Antibiotics are normally given before extraction and also to prevent bacteria from spreading through the blood stream causing serious illness. The best cure for tooth decay is prevention. The best way to reduce susceptibility to decay is through the use of fluorides. You can reduce the food supply for bacteria by reducing sugar in your diet. The build-up of plaque can be minimized considerably by frequent brushing and the use of dental floss. Regular, professional care is essential for longevity of tooth life.
Dental Plaque and Periodontal Disease
Dental plaque can lead to periodontal disease. Tooth decay can lead to the destruction and eventual loss of teeth. However, periodontal disease, a disease of the supporting tissue around the tooth, can be so severe that the teeth loosen and fall out. The teeth are seated in sockets in the bones of the upper and lower jaws in the alveolar bone, (alveolar means hollow). The bone does not hold the teeth in place; rather, the teeth are stabilized by connective tissue called periodontal ligaments that extend between tooth-roots and sockets. The part of the tooth next to the sulcus is extremely difficult to keep free of bacterial plaque, and if not removed constantly, or left undisturbed for a few days, will form tartar - a rough, hard material that adheres to teeth.
Plaque and tartar build-up constitute the primary cause of periodontal disease. Periodontal disease begins with mild gum inflammation and becomes more severe over time. Its progression can be divided into four stages. The first stage is gum inflammation or gingivitis, and the gums may become reddish or purple and slightly swollen. They may be tender and they may bleed easily. You may have a sour taste, and your breath may be offensive. You may have no symptoms. The second stage or early periodontitis will involve the sulcus becoming swollen and more inflamed. The sulcus expands its borders creating an even better environment for bacterial growth. As the inflammation spreads and worsens, it will soon attack the periodontal ligament that holds the teeth in place. At this point, a dentist would use a periodontal probe to measure the depth of each periodontal pocket.
Periodontitis does not progress steadily, but rather intermittently. Symptoms and the rate of destruction vary. The third stage will see erosion of the gum, pockets will deepen, and more potent forms of bacteria develop. The periodontal ligament and alveolar bone become inflamed. In the fourth stage, there is so much ligament and bone loss that the tooth, no longer stable, will loosen in its socket. Bone loss magnifies pressure from chewing, making the tooth progressively looser. As the tooth looses its support it will fall out or require extraction.
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