A Guide to Dental Anatomy
Dental anatomy examines the structures that make up the teeth of a human being. Those studying dental anatomy will learn the classification, appearance, and development processes of the teeth. It is considered to be a taxonomical science due to the nature of classifying the various teeth and structures. The naming of the teeth is also practically used in dentistry to diagnose and treat patients.
Teeth begin developing in a human fetus white it is still in utero. This is a crucial time of development, because the during this development phase the teeth are already forming and determining what their eventual morphology will be. During various stages of fetal development, the enamel, dentin, cementum, and periodontium need to cultivate in order for the person to have good oral health throughout life. Between the sixth and eighth week of gestation, primary teeth begin to form, and in the twentieth week, permanent teeth begin to develop. There are four stages of tooth development. They are referred to as bud, cap, bell, and maturation.
As a general rule, humans are born with twenty primary teeth that eventually fall out and are replaced with permanent teeth. There can be twenty-eight to thirty-two permanent teeth depending on the person. In some cases, a person may not develop any or all of the four wisdom teeth. The teeth are divided evenly within the top and bottom jaws. The upper jaw is called the maxilla, and the lower jaw is called the mandible.
There are a few factors that determine how teeth are named. The set, arch, class, type, and side are all used to classify and identify the different teeth. Teeth come in two sets, known as primary or deciduous and permanent or adult. The arch of the teeth is also classified in two ways; mandibular located in the upper jaw and maxillary in lower. The classes of teeth are divided into four categories. They are names incisors, canines, premolars, and molars. Primary teeth sets do not contain premolars. Within these categories, teeth can be further classified. Incisors can be lateral or central, premolars can be 1st or 2nd, and molars can be 1st, 2nd, or 3rd. Teeth can also be named by the side of the mouth that they are located on.
Notable Tooth Structures
Each tooth has defining structures that make up its general composition. These main components are known as the crown, root, surfaces, cusp, cingulum, ridges, developmental groove, embrasures, and mammelons.
The crown structure is located above the neck of the tooth, the area that is also known as the cementoenamel junction. It is covered completely by protective enamel tissue. The composition of the crown is mainly dentin, surrounding an internal pulp chamber. After teeth have protruded into the mouth, the crown will be visible.
Below the cementoenamel junction, lays the root of the tooth. The anatomic root is covered with cementum and is composed mostly of dentin. Pulp canals are also part of the makeup of the root. Some teeth have one root, while others may have multiple roots. The root works with the periodontium to aid in support and attachment of the tooth in bone.
Surfaces are denoted in two ways: facial and lingual. Facial surfaces of teeth are situated nearest to the cheeks, while lingual surfaces are found closer to the tongue. In posterior teeth (premolars and molars), occlusal surfaces help with chewing. In anterior teeth (incisors and canines) surfaces that work in the same function are called incisal. Cervical surfaces are found where the crown and root meet, while apical surfaces are located near the apex of the root. Mesial surfaces are closer to the median of the face, and distal surfaces are found further away.
Posterior teeth and canines have elevations on the occlusal surface called a cusp. Maxillary and mandibular first premolars tend to have two cusps, while canines only have one. Three cusps can usually be found on mandibular second premolars, maxillary molars tend to have four cusps. When a fifth cusp is formed on the maxillary first molar, it is called the cusp of Carabelli.
Elevations on the teeth are known as ridges. The cingulum is a ridge located at the base of the cuspid teeth and the upper incisors crown’s lingual surface. It can be shaped like either a U or a W. Most of the cervical third’s lingual surface is composed of the cingulum.
The triangular spaces between the proximal surfaces of neighboring teeth are called embrasures. There are four embrasures for every point of contact and they are called, facial, lingual, occlusal, and cervical. The interdental papilla from the gingiva fills the cervical embrasure. The purpose of the embrasure is to protect the gingiva from food and frictional trauma, as well as serve as a self-cleansing mechanism.
Notable Tooth Characteristics
There are eight incisors located in the anterior teeth, divided evenly between the upper and lower jaw. The main purpose of the incisors is to aid in cutting food while chewing. Incisors do not contain cusps, but have incisal ridges on their surface areas. The two upper front teeth are known as maxillary central incisors, and in the permanent teeth, they are the widest teeth in the anterior set. Their counterparts in the lower jaw are called mandibular central incisors. The teeth on either side of the upper two front teeth are called the maxillary lateral incisors. In the lower jaw, the teeth on either side of the maxillary lateral incisors are called the mandibular lateral incisors.
Located three teeth away from the center in both the maxillary and mandibular sets are the canines. They separate the incisors from the molars, serving as an aid to both during chewing. The main purpose of the canines is to tear food. Each canine has one cusp. The maxillary canine is the longest tooth in the mouth.
Premolars are located distal to the canines, and are categorized as first or second. They have a variety of purposes depending on the type of premolar. Maxillary first premolars and mandibular first premolars have two cusps and are mainly used for tearing food. The main function of the maxillary second premolar is to grind during chewing. They also have two cusps, but they are duller in shape than the cusps of the first premolar. There are three cusps on the mandibular second premolars, and their primary function is to assist mandibular first molars in chewing.
The most posterior teeth are the molars and they vary in appearance. The purpose of the molars is to grind food. Molars can be first, second, or third. Third molars are most commonly referred to as wisdom teeth.
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