Hetero-dontia dentition is the technical term given to the teeth of humans and most omnivorous mammals, simply meaning that the teeth are capable of handling various forms of food substances. The upper and lower jaws have a nearly identical set up.

The incisors can be found are the four front teeth on both rows, which are designed to tear through and cut the food from its source, such as biting into a sandwich. Their shape is reminiscent of chisels, and they operate on the same basic principle.

The cuspids, which are often called canines, are shaped rather like cones. Their main purpose is to hold food and help in the tearing process, and they are positioned at the corners of each set of teeth. Canines and incisors are unique in their single root composition, unlike the remaining teeth which have at least two. The labial side of the incisors and canines are those that run along the lips’ edges.

The bicuspids, or premolars, are positioned just behind the canines. Premolars generally have two or three roots and appear to be more rounded to serve their purpose of grinding food. The irregular surfaces that they appear to have are known as dental cusps, and are the exact right shape for grinding the food to a pulpy, easy to swallow mass. The surface of the premolars which remains near the cheek is known as the buccal surface. The remaining teeth are known as molars. For all teeth, the surface which runs along the tongue is known as the lingual surface.


Humans go through two sets of teeth, the first set which arrive during early childhood and the second set of permanent teeth that comes in during late childhood and preadolescence. This phenomenon is known as diphyodont. There is an actual formula to discern the two sets of teeth humans develop over a lifetime.

Deciduous Dentition Formula: I 2/2, C 1/1, DM2/2, = 10x2 = 20 teeth Permanent Dentition Formula: I2/2, C 1/1, P 2/2, M 3/3, = 16x2 = 32 teeth

What this stands for is nothing more than the first letter of the identified tooth followed by the total number of that tooth in the mouth for each given cycle. I stands for incisors, C means canines, DM refers to deciduous molar, P refers to premolars, and M means molar, as in the permanent type.


Image: Teeth

Somewhere around 6 months of age, the milk teeth, or the 20 deciduous teeth, begin to emerge from the gums. The first teeth are most typically the incisors, although sometimes a rare child might sport a lower canine or something first. These teeth continue to come in until at around age 2 ½ to 3 the full first set of deciduous teeth have grown into the mouth.

Somewhere around the age of 6 or 7, the deciduous teeth begin to be replaced by the permanent teeth, forcing the deciduous teeth to fall out as the permanent teeth grow into the space. Typically around age 17, the final set of molars, the wisdom teeth, begin to erupt. However, there have been numerous documented cases of wisdom teeth breaking the surface of the gums as late as age 30. Wisdom teeth are not usually able ot accommodated by the size of the current human mouth, leading scientists to believe that the mouths of humans was once much larger. Wisdom teeth often grow in sideways, and can crush the molars next to the erupting wisdom teeth if not removed.

The design of human teeth is really quite ingenious. The dental cusps belonging to both the molars and the premolars are designed to occlude, allowing for the crushing and mashing of food that the incisors and the canines have torn from the source via a slicing action made when they slide across each other.

Each tooth has a crown, which is the exposed section above the gum line. Teeth are held into their sockets, or dental alveoli, by at least one root. The teeth fit into the recesses of the alveolar processes belonging to the mandible and the maxillae. Every tooth socket has a lining of connective tissue known as the periodontal membrane. Roots are cemented with a material aptly named cemetum, which enables teeth to be exposed to a wide variety of circumstances. The tooth is actually secured to the dental alveoli via fibers which run from the periodontal membrane into the cementum. There is a mucous membrane which encases the alveolar process, casually called the gums, known as the gingiva.


The tooth itself is similar to bone, but is in fact constructed of dentin, which is harder than bone. Enamel coats the dentin, creating the crown, which makes the tooth even more difficult to penetrate. Enamel is the hardest, most durable substance throughout the entire human body, and is comprised of nearly 100% calcium phosphate. Inside the tooth, centrally located, the tooth contains an additional cavity which holds the pulp. The pulp is comprised of connective tissue and blood vessels, and is responsible for keeping the tooth alive. Lymph vessels and nerves are also found within the pulp cavity. It is this cavity which is opened and repaired when a root canal is performed. The apical foramen, which is the opening that permits a root canal, is the main entranceway to the tooth for the necessary nourishment the tooth requires. During embryonic development, a mother who lacks sufficient Vitamin D and calcium in the diet is likely to rob the fetus of the proper building blocks for healthy teeth. A poor diet during the embryonic stage can result in bad teeth even after the permanent set grow in.

Chemical digestion begins with saliva, which with the help of the premolars and molars, churns the masticated food into the bolas. Saliva helps to break down the food, give it taste, and is the secondary link in the process of digestion, second only to the teeth.
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