provided by: David DiGiallorenzo
The teeth are the first point of contact for food, drink or anything else we come into contact with, and the enamel on teeth are the most dense and toughest of all skeletal tissue. Enamel is also sometimes the only thing that survives on an organism in an archaeological sense. Sometimes, teeth can be easy to identify on something, even when the body and other tissue is no longer present. Many creatures including fish, reptiles aside from turtles, most mammals and amphibians have teeth. Some vertebrates do not have teeth such as birds, turtles, baleen whales, and some bony fish.
The teeth can show a lot about the history of a person or animal that is being studied because they portray a large number of pathological conditions that can give a background of the organism’s life. One example is called enamel hypoplasias, which shows a history of possible poor diet or bad health in childhood. Caries are cavities in the tooth, and display a history of diets high in carbohydrates. Mineralized plaque on teeth known as calculus can show remains of an organism’s past diet.
As a living thing ages, the teeth can wear down over time. Several methods of studying teeth and wear on teeth can help display the age of both humans and animals. Microwear, or tiny wear on the teeth just visible by a microscope, can be seen and shows how the tooth enamel becomes scratched over time because of eating. It also helps to demonstrate how the teeth are used as tools and ways to devour meat and other foods.
The Age at Death
Looking at teeth and jaws can help scientists determine the age of death of an organism. As the teeth go through stages of wear, eruption, and loss, these things can help determine and assess the developmental age of a once living thing. It should be noted that developmental age is not the same thing as actual age. Different organisms within the same group can reach different stages in life at various ages and it can all depend on various factors like genes or nutrition. For example, sheep can show significant tooth wear if they are castrated; a study of Shetland sheep’s teeth showed much faster wear for rams that had been castrated. On the other hand, this did not show in the case of tooth eruption
The part of the mouth where it is shut behind the canine teeth is known as the postcanine occlusal area. This percentage in adult populations in regards to teeth eruption differs between developmental ages.
Time or Season of Death
For mammals, the base of the tooth known as cementum is deposited yearly in patterns of growth. Often the greatest or fastest increment is during the summer, and less in the winter. This increment appears as a thin, dark line. By studying these dark lines, often scientists can determine how long an animal survived after the tooth erupted. Of course, these lines are not always clear or easily observed, so the factors can vary.
The Anatomy of Teeth
In vertebrates, there are four different types of tooth attachments to the jaw. The thecodont is where the teeth have roots that fit right into the sockets. Most reptiles and amphibians exhibit teeth that anchor into a bony shelf known as a pleurodont. In bony fish, this attachment is known as the acrodont, where the teeth are attached to the bones by small pedestals at the base. Other fish with cartilage and sharks have an attachment known as Sharpey’s fibers, multiple rows of teeth that are attached directly to the cartilage by these fibers.
Most vertebrate animals have two sets of teeth: the milk teeth (also known as “baby teeth”), and permanent adult teeth. Whales with teeth have only one set of teeth and so they are referred to as monophyodont, while other vertebrates with two sets are known as diphyodont. Certain animals that can replace teeth throughout the lifespan are known as polyphyodont.
Mammals have four different types of teeth. These teeth types are the incisors, canines, molars, and premolars. The visible part of the tooth known as the crown is covered with enamel. The root is held inside the alveoli, and is covered with a tissue that resembles bone known as cementum. Underneath those layers is a substance called dentine, which is also the source of ivory. The pulp chamber of the tooth is protected by the dentine.
Diseases of the Tooth
One of the most common tooth diseases is known as calculus. This is also called plaque, which sticks to the teeth. Scientists can use a variety of different methods to record calculus that has grown over time on the tooth through laboratory testing.
Another common tooth disease is called caries. This condition is exhibited when acids can break down the enamel of the tooth and cause damage. In humans, caries is more commonly known as cavities. By studying caries in humans, we can see the move from a hunter and gatherer life over time. Many scientists can study caries in human remains to get a clearer picture of how early man once lived and ate.
Modification of Teeth
Before the modern dentist, there were other cases where people once deliberately changed the teeth. Often, people would simply file or chip away at rotting teeth. This can be found in different parts of the word including Africa, Australia, the Americas, Egypt, Europe, and in Southeast Asia. The removal of teeth, also referred to as tooth avulsion, was not as common in archaeological groups of humans, however removing incisors was found to be practiced in the Italian region during the Neolithic period. In addition, the use of prosthetics such as gold fillings and bridges were discovered as far back as the Etruscan period.