Tooth anatomy is a study dedicated to the structure of the teeth. The growth, appearance, and arrangement of teeth fall in this category. Dental anatomy is also denoted as a taxonomic science as it deals with the naming of different teeth and their structures. This detailed information serves a very useful and practical purpose for dentists, enabling them to easily identify each tooth and their structure during various treatments.
A tooth’s anatomic crown is the area covered in enamel above the cementoenamel junction (CEJ) or what we can describe as the neck part of a particular tooth. Most of the crown is made up of dentin with the pulp chamber deep inside. The crown is within the bone right before the eruption. The anatomic root is found below the cementoenamel junction (CEJ) and is layered with cementum. A tooth may have several roots or just one root (single-rooted teeth). Canines and most premolars usually have one root only, whereas maxillary first premolars and mandibular molars usually have two roots. Further, if we check the Maxillary molars, they consist of three roots. Any other additional roots found in the teeth are generally termed as supernumerary roots.
Human beings customarily have 20 primary (baby or milk) teeth and 32 permanent (adult) teeth. Our teeth can be classified into four different segments such as incisors, canines, premolars (also known as bicuspids), and molars. Incisors are mainly used for biting food articles like raw carrots or apples and bananas; while on the other hand, molars are used for grinding the food after the Incisors have bitten them into smaller size pieces during the initial process of eating.
Amongst the deciduous or primary teeth, ten are found in the upper jaw (maxilla) and ten of them in the lower jaw (mandible) to complete a total set of twenty teeth. The dental formula for primary teeth is as shown below.
There are two types of incisors and two types of molars in the primary set of teeth. Incisors are known as centrals and laterals, while the molars are addressed as the first and second. All primary teeth are replaced by a set of permanent teeth at the right age.
Among the permanent set of teeth, sixteen are found in the maxilla and sixteen in the mandible to make a full set of thirty-two adult teeth. The dental formula for the same can be mentioned as below.
The maxillary teeth consist of the maxillary central incisor, maxillary lateral incisor, maxillary canine, maxillary first premolar, maxillary second premolar, maxillary first molar, maxillary second molar, and maxillary third molar. The mandibular teeth are the mandibular central incisor, mandibular lateral incisor, mandibular canine, mandibular first premolar, mandibular second premolar, mandibular first molar, mandibular second molar, and mandibular third molar. Third molars are commonly known as “wisdom teeth” and it may or may not form at all. Just in case any additional teeth are formed like a fourth or a fifth molar, which happens in rare cases, are referred to as supernumerary teeth (hyperdontia) in dental terms. Extra eruptions than the normal teeth are called hyperdontia and lesser than the usual number of teeth is called hypodontia.
Enamel is the hardest and highly mineralized substance of the body. There are four major tissues which make up the tooth structure, namely enamel, dentin, cementum, and dental pulp. It is generally visible and needs to be supported by the dentin beneath. 96% of enamel consists of mineral, while the rest of 4% is made of water and organic material. The routine colour of enamel can vary from pale yellow to greyish white. Enamel being semi-translucent, the colour of dentin and any other restorative dental material beneath the enamel has a strong effect on the tooth’s appearance. The thickness of the enamel varies on the tooth’s surface and is often at its thickest on the cusp (up to 2.5mm) and thinnest at its border. The depreciation rate of the enamel or attrition is annually 8 micrometres from all the daily routine factors.
Dentin is the substance between enamel or cementum and the pulp chamber. It lays concealed by the odontoblasts of the dental pulp. The formation of dentin is known as dentinogenesis. The porous, yellow-hued material composition is made up of 70% inorganic materials, 20% organic materials, and 10% water by weight. It is softer than the enamel, hence it decays more promptly and severe cavities can take place if not treated properly. In spite of this, the dentin still acts as a protective layer and supports the crown of the tooth.
Cementum is a specialized bone-like substance that covers the root of a tooth. It is roughly 45% inorganic material (predominantly hydroxyapatite), 33% organic material (predominantly collagen) and 22% water. Cementum is emitted by cementoblasts from within the root of a tooth and is found to be the thickest at the root apex. It appears yellow in colour and is softer than both dentin and enamel. The principal purpose of cementum is to serve as a medium through which the periodontal ligaments can attach themselves to the tooth for a proper stability.
Dental pulp is at the centre and the most vital part of the tooth filled with a soft connective tissue. This tissue contains the blood vessels and nerves that enter the tooth through a hole found at the apex of the root. Along the margin between the dentin and the pulp are odontoblasts, which induce the formation of dentin. Other cells present in the pulp are fibroblasts, preodontoblasts, macrophages and Lymphocytes. The pulp is generally referred to as “the nerve” of the tooth.
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