If baby teeth do not fall out on time, they may prevent the permanent teeth from developing properly. In the attempt to erupt, the permanent teeth may find another path in which to erupt, thus causing misalignment. Sometimes, more than the normal number of teeth erupt; these extra teeth are called supernumerary teeth. They may cause overcrowding and may have to be pulled. Some permanent teeth may not develop at all. In this case, the baby teeth will not fall out and should be kept as long as possible. The occurrence of too few or too many teeth tends to follow a genetic pattern, with other family members-past or present- displaying the same condition.
The position of teeth may also be altered when baby teeth are lost too early due to decay, accidents, or other causes. The teeth on either side of and opposing a lost tooth will then begin to shift and cause problems with the proper sequence of erupting new teeth. In this situation, a splint is used to prevent shifting and to keep the space open. (See Trauma to Children's Teeth in Part Two.)
Other factors affecting tooth position may involve permanent teeth that have become locked in the bone (a condition called ankylosis) and are unable to erupt. These teeth may have to be moved with surgery and braces.
Spaces between the baby teeth are normal. As the jaw grows, the baby teeth are spaced in order to accommodate their larger base. When the permanent teeth come in, they fit the larger adult jaw and fill in the spaces. Excess space may be present until a child is twelve to fourteen years old.
Types of Teeth
Eventually, there will be thirty-two permanent teeth: eight incisors, four canines, eight premolars, and twelve molars as shown in Figure 1.5. These permanent teeth will begin to appear as the baby teeth are lost-when a child is about six years
old-and should all be present by the time a child is seventeen. Only the last three teeth in each half of each jaw are not replacements for baby teeth. The teeth in these positions erupt only once.
Incisors are the sharp, chisel-shaped front teeth used for cutting food. Cone-shaped canines or cuspids are used for tearing food. The premolars or bicuspids have two cusps that are used for tearing and crushing food. The molars are located in the back of the mouth and have several cusps that are used for grinding food. The furthest (third) set of molars in the back of the mouth are also known as wisdom teeth.
As the mouth is explored, it becomes apparent how important every structure is, no matter how much we take it for granted. For example, eating would become impossible without a roof dividing the mouth from the nasal cavity. The roof of the mouth or palate is the horizontal structure separating the mouth and the nasal cavity. The palate is divided into two sections, as seen in Figure 1.5.
The front portion, directly behind the teeth, is the hard palate, which consists of bone that is covered by soft tissue. The hard palate contains some major nerves that affect the teeth. It is concave or vaulted and is the area in which the tongue rests when the mouth is closed. Ridges contained here aid in manipulation of food during mastication (chewing) and swallowing.
The soft palate is located behind the hard palate and blends into the pharynx, the cavity behind the soft palate where the digestive and respiratory passages meet. The soft movable palate is where the gag reflex begins. On either side of the soft palate are the tonsils. When we eat, the soft palate automatically seals the area that connects to the nasal areas so that food does not get into the respiratory system.
The palate plays an important role in dental care and dental health. During the developmental stage of the embryo, if the palate does not fuse in the middle, a condition called cleft palate results. (See Cleft Palate and Lip in Part Two.) In this condition, an opening exists between the two parts of the palate, making eating and speaking very difficult if not impossible. Surgery or appropriate appliances can correct cleft palate. In other cases, the palate may be too narrow, and the teeth will not come together properly. In this situation, the palate is expanded with orthodontic appliances.
When dentures are worn, the palate is used for suction to support the false teeth. However, this becomes difficult when excess bone (tori) develops. Tori usually occur in the middle of the palate and may have to be surgically removed if dentures are to be worn or if the tori become irritated or painful.
With certain kinds of gum disease, tissue is taken from the palate and transplanted on the gums. Some nerves that supply the teeth originate in the palate. During difficult procedures, such as those performed during oral surgery, these nerves on the palate are anesthetized.
Eating very hot or crusty foods such as pizza may damage the delicate soft tissues covering the palate. The palate also shows specific signs during illnesses such as AIDS, chicken pox, or herpes.
Forked tongue, tongue-lashing, tongue-twister.... Even the English language recognizes the importance of the tongue, without which we would not be able to speak, swallow, or taste. This important part of our body can even tell us, in a general way, the state of our health. And what more graphic way to express disgust than by sticking out your tongue?
The tongue is a mass of "voluntary" muscles, called intrinsic and extrinsic muscles. The intrinsic muscles allow the tongue to change size and shape quickly. The flexible extrinsic muscles allow the tongue to rapidly change position.
The bottom of the tongue is attached to the floor of the mouth. This is where the salivary glands are located. Many nerves are situated in the tongue and floor of the mouth. If a person becomes unconscious, the tongue tends to fall back into the airway, causing suffocation. It is, therefore, necessary to look in the person's mouth and clear the airway before commencing CPR (cardiopulmonary resuscitation).
The tongue is not the lively red color of the gums; rather, it has a greyish coat on the surface, caused by the specialized cells of which it is made. The muscle is covered with a mucous membrane formed into nipplelike elevations called papillae. Papillae roughen the tongue's surface to help it guide foods during chewing and swallowing. Papillae also contain nerves for touch sensations, and most contain taste buds. Examination of the tongue with a mirror reveals a row of v-shaped, rounded, raised areas toward the back of the tongue where the taste buds responding to bitterness are located. In front of this row are tall, thin, cone-shaped raised areas that respond to sweet, sour, or salty substances. At the sides of the tongue are taste buds that react to acidic ingredients.
The tongue has several functions. It is involved in speech, manipulation and positioning of food, tasting, and swallowing. The tongue aids chewing by crushing food against the roof of the mouth (the palate) and by rolling the food between the teeth. Swallowing is accomplished as the tongue presses the food against the palate and pushes it backward into the oropharynx (entrance into the digestive and respiratory systems). The act of chewing involves coordinated movements of certain muscles that close the mouth and raise and lower the mandible, causing the teeth to grind and crush the food. The smell and taste of food cause saliva to be secreted immediately, which helps dissolve, dilute, and lubricate chewed food. The cheeks become tense and the tongue moves the food between the teeth and backwards towards the stomach. If disease necessitates surgical removal of the tongue or if it is missing at birth due to genetic disturbances, chewing is assisted by the cheeks and the floor of the mouth.
The tongue is, of course, very active in speech. If the tongue is incorrectly attached to the floor of the mouth from birth, speech is impeded and a "lisp" develops. (See Speech Problems; and Tongue-Related Problems in Part Two.) The tongue must be placed near or against the upper front teeth to form the consonants D and T. Producing the sound made by the letter L also requires the interplay of tongue and teeth.
The Tongue as a Diagnostic Tool
The tongue's appearance is often used as an aid in the diagnosis of various diseases and conditions. We know, for instance, that during illness, some of the papillae become engorged and change color, becoming strawberry in appearance. When people have pernicious anemia, their tongues may be sore, appear beefy red, and have patchy white spots on the surface. An enlarged tongue is a sign of hypothyroidism.
According to Chinese medical science, the tongue is divided into certain sections, with each part pertaining to an organ. In this approach to the diagnosis and treatment of disease, the tip of the tongue represents the heart and lung; the central part represents the spleen and stomach; the root of the tongue represents the kidneys; and the sides of the tongue represent the liver and gall bladder. Color, texture, size, and shape of the tongue are taken into consideration as a diagnostic tool to help determine the organ to be treated.
Although self-diagnosis by using the tongue is certainly not practical, understanding what a healthy tongue looks like may give you clues about your general health. Any variation in color (too red or pale), texture (thickly coated), size (enlarged or swollen), or shape (scalloped border) may indicate an unhealthy condition.
The Salivary Glands
Cleansing of the teeth and mouth as well as good digestion depend a great deal upon the salivary glands. A number of these glands secrete saliva into the mouth. Saliva-which contains water, salts, enzymes, and mucus-moistens and softens foods for ease in swallowing, and cleanses the teeth and mouth. The function of the salivary glands is affected by hormones produced by the pancreas, testes, ovaries, and the thyroid and pituitary glands. The nature and quantity of saliva is affected by reflexes for which the taste buds act as receptors. The presence of soft moist foods in the mouth will, for instance, stimulate less secretion of the lubricating component of saliva. Salivation or watering of the mouth can also be a conditioned reflex, as when we think about a certain food or hear the mention of a particular food.
There are a few minor salivary glands situated around the lips, inside the cheeks, in the palate, and on the tongue. There are also three major pairs of salivary glands. On each side of the face, just in front of the ears, are the parotid glands, the largest of the salivary glands. The duct for each parotid gland, called Stenson's duct, opens into the mouth from each cheek opposite the upper second molar. The parotid glands produce a clear watery secretion that functions as a cleansing, dissolving, and digestive agent. The saliva produced by the parotid gland contains a substance called ptylin, a salivary enzyme that breaks down starch. When a sour food such as a lemon is introduced into the mouth, it stimulates the parotid glands.
The sublingual glands are located in the floor of the mouth, under the tongue. The duct for these glands, called Rivinus' duct, opens into the mouth from the floor of the mouth directly behind the lower front teeth. The saliva secreted by this gland is thicker and ropey compared with the secretion from the parotid. Sublingual-gland secretions serve as lubricating agents; bland substances such as milk and bread stimulate its production.
The submandibular glands are located deeper in the floor of the mouth, under the base of the tongue and more to the side of the lower jaw. These glands secrete a mixed type of saliva that is thin at first and becomes thicker. This secretion is also used for lubricative and digestive purposes.
From The Complete Book of Dental Remedies by Flora Parsa Stay, DDS, ©1996. Published by Avery Publishing, New York. For personal use only; neither the digital nor printed copy may be copied or sold. Reproduced by permission.