Dental anatomy is primarily concerned with the external form and appearance of a tooth.
DEFINITIONS
It is the branch of dentistry which deals with gross structure, mainly the morphology of the tooth and its associated parts.
It is the branch of dentistry which deals with the art and science of basic morphological, anatomical and functional relationships of teeth, jaws and their associated structures needed for normal harmony of an individual.
It is a branch of medicine and dentistry, which comprises of the study of morphology of both tooth and its associated structures including masticatory system.
Dental anatomy not only includes the study of tooth morphology, but also involves roots, pulp chambers, crown contours, contacts and embrasures associated with the crowns of teeth.
Tooth: Teeth are mineralized structures except for the pulp and are located in first part of the digestive tract. A tooth is defined as “one of the hard tissues that are positioned on the jaws and help in holding and mastication of food, also as weapons of offense and defense in lower animals”. The designs of the teeth are a reflection of eating habits. Teeth of a man are formed for cutting, tearing and grinding of food substances.
Human dentitions are divided into many classes of teeth based on the appearance and function or position. The types or different classes of teeth are as follows:
- Incisors: Incisors are named because they are used to incise or cut food. They are located in the front part of the mouth and have sharp, thin edges for cutting
- Cuspids: Cuspids, also referred to as canines, are at the angles of the mouth. Each tooth has a single cusp instead of an incisal edge and are designed for cutting and tearing
- Bicuspids: Bicuspids, also referred to as premolars, are similar to the cuspids. They have two cusps used for cutting and tearing, and an occlusal surface that is wider to crush the food
- Molars: Molars are located in the back part of the mouth. Their size gradually becomes smaller from the first to third molar. Each molar has four or five cusps; these teeth are shorter and more blunt in shape than other teeth and provide a broad surface for grinding and chewing solid masses of food.The detailed description of each tooth is given in following chapters.
FUNCTIONS OF TEETH
Human beings have teeth with rich and unique anatomic characteristics and thus necessitate a comprehensive learning. The normal tooth form is extremely varied with every individual and is very difficult to reproduce. The normal anatomy of teeth assures the efficiency of mastication.
- Mastication is the primary function which includes cutting, shearing and chewing.
- Many others like growth of the skull and facial structures are seen with the development of teeth.
- Deglutition and swallowing are done with the help of teeth.
- Phonation and aesthetics are other major functions of teeth (note these properties in cleft lip/palate and edentulous patients).
- Protection to soft tissues of the mouth.
- Some animals, mainly carnivorous, use teeth for fighting and/or defense too. It is very important for an animal to have teeth as they are used not only for eating but also in grooming and defense.
- Last but not the least, tooth has a very important role in forensic odontology.
Each function of a tooth is described in respective chapters and in chapter 16, page 217.
AIMS OF DENTAL ANATOMY
- The dentist who is intended to care for teeth should have thorough knowledge of the characteristics and fundamentals of dental morphology.
- To develop adequate manual skill to reproduce any part of the tooth, thus maintaining the perfect correlation with associated structures.
- Of great importance, a knowledge of function and anatomy that is intimately related to most dental areas.
OBJECTIVES OF DENTAL ANATOMY
The objectives of dental anatomy are as follows:-
- To know the normal anatomic, physiologic, and biomechanical relationships of the dental structures.
- To be familiar with the clinical significance and define the shape and contour relationships of the normal dentition.
- Identify, describe, and to reproduce in drawings and wax, the morphology of permanent teeth from various views.
- Discuss the relationships between teeth and supporting structures.
- Correctly identify natural teeth with and without anatomical variations.
SCOPE OF DENTAL ANATOMY
Though currently the use of computers and computer assisted graphics have helped out in teaching dental anatomy in three dimensional views, drawing and dental carving are considered to be very practical and objective methods for teaching and motivating dental students to obtain the knowledge till today.
The knowledge of dental anatomy is fundamental for the practice of any branch of dentistry. Clinical/practical research and other activities in dental anatomy, carving of tooth can also be directly correlated. Carving of tooth helps in preparation of crown and bridge and other esthetic and restorative treatments.
The purpose of carving is to restore, in general by means of total or partial reconstruction, one or more parts of a tooth in its form and function as also to re-establish the lost balance in the physiology of mastication.
EVOLUTION OF TEETH
- Homodont: It is a Greek term, meaning ‘same teeth’. Animals, which have one/single type of dentition where in all are similar in shape, indicative of a uniform diet.Example: Fishes, amphibians, and most reptiles. Crocodile has cone shaped teeth as also whales and dolphins
- Hetrodont:Term derived from Greek, meaning ‘different teeth’, which refers to animals having more than a single type tooth morphology and are of different sizes and shapes, specialized for different tasks.Example: Man has different types of teeth
- Monophyodont: Dentition in which the species has only one set of teeth, which are functional through out the life.Example: Reptiles
- Diphyodont: Dentition in which the species have two sets of teeth, one set (called ‘deciduous’) being shed and replaced by a permanent set of teeth, which are functional throughout the life.Example: Cats, dogs, and humans
- Polyphyodont: Dentition in which the species has many sets of teeth, which get replaced and remain functional throughout the life.Example: Seen in lower vertebrates, mainly fishes.
DEFINITIONS
- Mandible: It is the complete lower jaw which is made up of a single pair of bones
- Maxilla: It is a bone or part in the upper jaw that contains canine, premolar and molar teeth
- Premaxilla: It has paired bones present at the front of the upper jaw (maxilla) that contains incisor teeth on both sides in the midline.
As we all know, human beings have two sets of dentition: a deciduous and a permanent set. The oral cavity is divided into 4 quadrants, which represent one side of a jaw and each quadrant contains 5 deciduous teeth or 8 permanent teeth or combination of both depending on the age of the individual, which is discussed in detail in succeeding chapters.
THE DECIDUOUS DENTITION
There are twenty deciduous teeth, ten in the maxilla and mandible respectively, and are grouped into three classes as incisors, canines and molars.
- Synonyms of deciduous teeth are primary teeth, milk teeth, baby teeth or temporary teeth or lacteal teeth or juvenile teeth. There are a total of 20 primary teeth (8 incisors, 4 cuspids and 8 molars). Incisors are the first primary teeth to erupt and usually between 6–9 months. The last teeth usually erupt in by 24 months. These are present till the permanent are erupted, i.e. 6 years
- These teeth differ from the permanent in many ways. Specifically, no premolars are developed in this dentition.
Features of each deciduous tooth are discussed in detail in chapter 9.
THE PERMANENT DENTITION
There are thirty two permanent teeth, out of which sixteen each are maxillary teeth and sixteen are mandibular teeth that are grouped into four classes as incisors, canines, premolars and molars.
- Synonyms of permanent teeth are secondary, permanent or succedaneous teeth. There are a total of 32 secondary teeth (8 incisors, 4 cuspids, 8 premolars and 12 molars). The first secondary tooth to erupt in the oral cavity is the first molar, and it usually erupts around 6 years of age. The last to erupt is the 3rd molar at around the age of 21 years. All other teeth are usually present by the age of 14 years
- These teeth stay in the oral cavity lifelong if maintained properly.
DENTAL FORMULA
It is a way of designating or indicating the number or arrangement of teeth for a given species, but used mainly for mammalian teeth. Teeth of the upper jaw are listed over the lower jaw. The dental formula is described only on one side of the jaw, which represents the teeth on one side of the face of both jaws and is done so because the jaw is bilaterally symmetrical. The incisors are indicated first, followed by the canine, premolars and molars.
For instance I 3/3, C 1/1, P 4/4, M 3/3 letters indicate 3 incisors, 1 canine, 4 premolars and 3 molars on one side of both upper and lower jaws, so the dental formula would be:
Individual teeth can also be denoted. The disadvantage of this dental formula is that the sides of the jaw cannot be indicated.
From now onwards we take it as granted that the permanent dentition is considered generally and it is understood that the reader is aware of this. If deciduous teeth are explained, it will be specified.
FURTHER READING
- Ash M M and Stanley J N, 2003. Wheeler's dental anatomy, physiology, and occlusion. 8th edition.
- Siéssere S, Vitti M, de Sousa LG, Semprini M, Regalo SCH. Educational material of dental anatomy applied to study the morphology of permanent teeth. Braz Dent J 2004;15(3):238–42.