PRIMARY DENTITION It takes from 2 to 3 years for the primary dentition to be completed. Calcification of the primary teeth begins in utero 13 and 16 weeks.

PRIMARY DENTITION

• It takes from 2 to 3 years for the primary dentition to be completed .

• Calcification of the primary teeth begins in utero 13 and 16 weeks

• By 18-20 weeks post fertilization, all the primary teeth have begun to calcify, beginning with the initial calcification of the primary central incisor to the completion of the roots of the primary second molar.

PERMANENT TOOTH

Each permanent tooth takes 8-14 years to complete if the third molar is considered.

Normally at birth no teeth are visible in the mouth;

however, occasionally infants are born with erupted mandibular incisors.

• Investigations of the chronology of emergence of the primary teeth in different racial and ethnic groups reflect considerable variation, and there is very little information available on tooth formation in nonwhite/non-European-derived populations

World population differences in tooth standards suggest that there are patterned differences that may not be large.Tooth size or tooth morphology, as well as tooth formation, is highly inheritable. There are few definitive correlations between primary tooth emergence and other physiologic parameters such as skeletal maturation, size, and sex

values for eruption are presented as the mean age and a range of variation based on plus or minus one standard deviation, after rounding all values to the nearest month.

• The eruption or emergence of primary mandibular central incisors through the gingiva occurs at a mean age of eight months.

• The eruption of these teeth is followed about two months later by the maxillary central incisors at a mean age of 10 months, and then by the mandibular lateral incisors at a mean age of 13 months.

• In some instances babies may display four mandibular incisors before the maxillary teeth erupt.

1 year

• At a mean age of 16 months the primary first molars erupt with the maxillary molar tending most often to erupt earlier than the mandibular first molar.

• There is some evidence for a difference by sex for the first primary molars, but there appears to be no answer for the question: Why does the first molar have a different pattern of sexual dimorphism?

2 years

2 YEARS•The primary maxillary canine erupts at a mean age of 19 months and the mandibular canines at 20 months.

•The primary second mandibular molar erupts at a mean age of 27 months with evidence that there is difference between boys and girls.

•The primary maxillary second molar follows at a mean age of 29 months.

• The predominant sequence of eruption of the primary teeth in the individual jaw is

• central incisor (A), lateral incisor (B), first molar (D), canine (C), and second molar (E),

• Variations in that order may be due to reversals of central and lateral incisors, first molar and lateral incisor. or eruption of two teeth at the same time.

• Jaw reversals in eruption of canines and first molars have been found to be important in increasing the variety of sequences

• When differences according to jaws are considered, we may see that:

• The lateral incisor. first molar. and canine tend to erupt earlier in the maxilla than in the mandible.

• Characteristic order in about a third of the children is : AB D C E

• The completed primary dentition may show evidence of bruxing wear, especially of the anterior teeth.

• Spacing of the teeth may be beneficial for the subsequent eruption of the permanent successors.

• 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 lay persons 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.

• the primary teeth are in use and contributing to the health and well-being of the individual during the first years of greatest development, physically and mentally.

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.

• 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

3 YEARS 4 YEARS

5 YEARS 6 YEARS

7 YEARS 8 YEARS