There are 4 types of teeth in the oral cavity:
- Incisors – The four front teeth in both the upper and lower jaws are called incisors. Their primary function is to cut food. The two incisors on either side of the midline are known as central incisors. The two adjacent teeth to the central incisors are known as the lateral incisors. Incisors have a single root and a sharp incisal edge. The incisors are developed from 4 lobes, in contrast to posterior teeth which develop from 4 to 5 lobes. When first erupted, the incisors have 3 mamelons, or bumps on the incisal edge which are remainders of the lobes from which the tooth developed. The cingulum is remainder of the 4th mamelon and can have a pit formed in it where it meets the lingual surface of the tooth. These incisal edge mamelons are usually worn away shortly after eruption with normal biting function. Central incisors have sharper and more acute incisor angles that lateral incisors. The maxillary central incisors are also unique in that they are larger than mandibular central incisors. Maxillary lateral incisors often vary the most in their shape. Sometimes maxillary lateral incisors can have a peg-like shape and are thus referred to as “peg laterals.” The maxillary lateral incisors may also be congenitally missing. The mandibular central incisor is the smallest tooth of all the incisors.4
- Canines – There are four canines in the oral cavity. Two in the maxillary arch and two in the mandibular area. They are behind and adjacent to the lateral incisors. Their main function is to tear food. They have a single, pointed cusp and a single root. They have the longest root of any tooth. They also serve to form the corners of the mouth. The canines have very prominent cingulum, but the maxillary cingulum is more prominent than the one on the mandibular canines and it rarely has pits. The lingual is formed by a single lingual ridge that lies between two lingual fossae.4
- Premolars (Bicuspids) – These teeth are located behind and adjacent to the canines and are designed to crush and grind food. There are eight premolars in the oral cavity. There are two in each quadrant of the mouth. The one closest to the midline is the first premolar and the one farthest from the midline is the second premolar. These teeth can have 2-3 cusps (mandibular second premolar typically has 3). The facial cusp is typically longer and wider than the lingual cusp. In the mandibular 1st premolar, the lingual cusp is very small and usually not functional. The maxillary first premolar has two roots, and the remaining premolars have a single root. There are no premolars in the primary dentition. The premolars replace the primary molars when they exfoliate. Often the 1st premolar is the tooth that is extracted in orthodontic procedures to make room for crowded teeth to move into place.4
- Molars – The most posterior teeth in the mouth are the molars. They have broader and flatter surfaces with 4-5 cusps and have the largest crown of any other teeth. They are designed to grind food. Mandibular molars typically have 2 roots. Maxillary molars, which are located behind the second premolars, typically have 3 roots. There are 12 molars in the permanent dentition with three in each quadrant of the mouth. They are named starting with closest to the midline as first molars, second molars and third molars. Although, some people do not fully develop the third molars and thus can vary in size and shape or even be absent. Third molars are often referred to as wisdom teeth and often have fused roots. The primary dentition only contains eight molars. The mandibular molar is the first permanent tooth to erupt in the mouth.4
