|The Primary (Deciduous) Teeth
We have learned the detailed description of each permanent tooth for a period of time，from now on we are going to learn the detailed description of each primary tooth.
The primary teeth are 20 in number, 10 in each jaw, and they are classified as follows: four incisors, two canines, and four molars in each jaw. Beginning with the median line, the teeth are named in each jaw on each side of the mouth as follows: central incisor, lateral incisor, canine, the first molar, and the second molar.
The postnatal period of development of the primary dentition spans about 21/2 years. This primary dentition remains intact until a child is about 6 years of age, when the transition to the permanent dentition begins. The primary molars are replaced by permanent premolars. There are no premolars in the primary set, and there are no teeth in the deciduous set that resemble the permanent premolars. However, the crowns of the primary maxillary first molars resemble the crowns of the permanent premolars as much as they do any of the permanent molars. The deciduous mandibular first molar is unique in that it has a crown form unlike that of any permanent teeth. These two primary teeth differ from any teeth in the permanent set when crown forms are compared in particular.
The formation of the teeth, development of dentition, and growth of the craniofacial complex are closely related in the prenatal as well as the postnatal development period. At birth there are usually no teeth visible in the mouth, but many teeth in various stages of development are found in the jaws.
In clinical practice the notation system divides the arches into quadrants with the entire dentition notated as
Thus, for a single tooth, such as the left maxillary central incisor the designation is A. For the mandibular right second molar, the notation is given as E.
Major Contrasts between Primary and Permanent Teeth
In comparison with their counterparts in the permanent dentition, the primary teeth are smaller in overall size and crown dimensions. They have markedly more prominent cervical ridges, are narrower at their “necks,” are lighter in color, and have roots that are more widely flared; in addition, the buccolingual diameter of primary molar teeth is less than that of permanent teeth. More specifically, in comparison with their following difference are noted:
Size: The primary teeth are much smaller than the permanent teeth
Color: The primary teeth are usually less pigmented and are whiter in
appearance than the permanent
The crowns of primary anterior teeth are wider mesiodistally in comparison with their crown length than are the permanent teeth.
The buccal and lingual surfaces of primary molars are flatter above the cervical curvatures than those of permanent molars, thereby narrowing the occlusal surfaces.
The cervical ridges of enamel of the anterior teeth are more prominent. These bulges must be considered seriously when they are involved in any operative procedure.
The cervical ridges buccally on the primary molars are much more pronounced, especially on the first molars maxillary and mandibular.
Cervical: The crowns and roots of primary molars at their cervical
portions are more slender mesiodistally.
5. Root: The roots of primary anterior teeth are narrower and longer comparatively. Narrow roots with wide crowns present
an arrangement at the cervical third of crown and root that
differs markedly from the permanent anterior teeth.
The roots of primary molars accordingly are longer, are
more slender, and flare more, extending out beyond projected outlines of the crowns. This flare allows more room between the roots for the development of permanent tooth crowns.
Clinical of the primary teeth
After the eruption of the primary mandibular central incisor in sixth month, the primary dentition is complete at about 21/2 years of age. Then the first permanent molar will erupt in 6 years old and the primary maxillary second molar is replaced by permanent premolar in 12 years old. Thus the longest primary tooth will stay in mouth for 10 years. There should be no question of the importance of preventing and treating dental decay and providing the children with a comfortable functional occlusion of the deciduous teeth.
The susceptibility to dental caries is a function of exposure time to the
oral environment and morphological type. The high peak for caries attack occurs when the children are in their developmental period.
The premature loss of primary teeth because of caries may not only reflect an unfortunate lack of knowledge as to the course of the disease but also establishes a negative attitude about preventing dental caries in the adult dentition. Loss of primary teeth may lead to lack of space for the permanent dentition. It is sometimes assumed by laypersons that the loss of primary teeth, which are sometimes referred to as “baby teeth” or “milk teeth”, is of little consequence because they are only temporary. However, the primary dentition may be in use from the age of 2 to 21/2 years until the age of 7,or about 5 years in all. Some of the teeth are in use until 12 years of age. Thus these primary teeth are in use and contributing to the health and well being of the individual during the greatest
development, physically and mentally.
A completely primary dentition plays an important part in mastication.
It is important to the children’s development of body.
3. The increase in prevalence of dental caries among the tooth types reverses their order of eruption.
The transition from primary to permanent dentition begins about 6
years of age with the eruption of the first permanent molars, The timing of the shedding of the primary teeth has an effect on the emergence of the permanent teeth, i.e., early shedding of primary teeth advances the emergence of the permanent teeth.
A lack of space associated with premature loss of deciduous teeth is a
significant factor in the development of malocclusion; the development of adequate spacing is a significant positive factor in the development of occlusal relations in the permanent dentition.
Premature loss of primary teeth, retention of primary teeth, congenital
absence of teeth, dental anomalies, and insufficient space are considered important factors in the initiation and development of an abnormal occlusion. Premature loss of primary teeth from dental neglect is likely to cause a loss of arch length with consequent tendency for crowding of the permanent dentition.
There are permanent tooth crowns in front of the anterior primary
tooth roots and under the primary molar roots. We should pay more attention to them when we are treating the primary teeth
A Detailed Description of Each Primary Tooth
In the crown of the primary central incisor, the mesiodistal diameter is greater than the cervicoincisal length.
The mesioincisal angle is a right angle but the distalincisal angle is round
Cervical ridge is obvious
Developmental grooves are not seen and the labial surface is very smooth
The lingual aspect of the crown shows well –developed marginal ridges and highly developed cingulum
Lingual fossa is small and divided into two parts by lingual axis ridge
Mesial and distal aspect:
The mesial and distal aspects of the primary maxillary central incisors are similar, triangle: the cervical aspect is thicker when the incisal aspect is thinner. The crown appears thick at the middle third and even down toward the incisal third. The curvature of cervical line, which represents the cementoenamel junction, is distinct, curving toward the incisal ridge.
It is relatively straight and the labial surface is much broader and smoother than the lingual surface
It’s cone shaped and the cross section is triangle
It turns to labial aspect
Developmental grooves are not seen
•Developmental grooves are not seen •Cervical ridge is obvious
•Developmental grooves are not seen