Introduction
The root of the tooth (lat. Radix dentis) lies below the crown of the tooth and fixes the tooth in the tooth socket of the jaw. The transition between the root and the crown of the tooth is called the neck of the tooth. The root of the tooth is covered by dental cement and is about twice as long as the crown. Furthermore, the root of the tooth is conical, which means that it tapers towards the tip of the root.
Neck of tooth
The neck of the tooth is the upper part of the tooth root and is therefore located between the crown and the root. The neck of the tooth is not protected by enamel like the crown of the tooth, but is surrounded by less protective gums. Histologically, the neck of the tooth is made of dentin.
This is a thin layer of cement, which, unlike root cement, does not contain any cementing agents. If the gums become diseased and the necks of the teeth are exposed, painful changes to the neck of the teeth can occur. Caries also often develops at this point.
Structure of the tooth root
The root of a tooth consists mainly of dentin (dentine), which is covered by root cement on the surface. This is formed by the cementoblasts. The tip of the root of the tooth (apex denitis) has a small opening (Foramen apicale dentis), which serves as an entrance for blood vessels and nerve fibers into the tooth cavity. The pathways in the tooth cavity are called dental pulp. The narrow extensions of the dental pulp into the tooth root are also called root canals.
Number of roots
Human permanent teeth have a different number of roots. The rule of thumb is that the further the tooth is in the oral cavity, the more roots it has. There is always at least one root canal per root.
The exception to this rule are the first two front molars: The first upper premolar usually has two roots, but the second upper premolar usually has only one root. So normally the incisors and canines have one root with one root canal, the small front molars (premolars) have one or two roots with correspondingly many root canals. The large posterior molars (molars) and wisdom teeth have an individually very different number of roots.
However, the individual tooth roots can also grow together or be divided into two root tips. Since anomalies and deviations from the norm can always occur, it is advisable to take an x-ray before removing a tooth root in order to get an exact picture of the tooth roots. Milk teeth also have tooth roots when they are fully grown.
The milk incisors and canines each have a root. The molars (milk molars) in the child’s dentition (milk teeth) have two roots in the lower jaw and three in the upper jaw. Anomalies are rather the exception with the milk teeth. During the tooth change between the ages of 6 and 12, the milk teeth are displaced by the permanent teeth. The roots of the milk teeth are absorbed by the following teeth so that it seems as if the milk teeth had no roots.