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  » Baby's developmental milestones  »  Dentition

In normal dentition there are 20 primary teeth: one central and one lateral incisor, one canine, and two molars in each quadrant of the mouth. The development of the primary tooth buds begins during the 12th week of fetal life. Permanent teeth form in two groups: the incisors, cuspids, and premolars develop from about the fifth month of gestation to 10 months' gestation, 1 year, and 4 years, respectively.

Each tooth is made up of a crown and a root. Enamel covers the crown and cementum covers the root. The main portion of the tooth is composed of dentin and pulp. Table 12-8 shows the average tooth eruption during infancy. Mandibular teeth usually erupt first, followed by the maxillary teeth; teeth often erupt earlier in girls than boys. Most children have at least one tooth by 14 months of age.

Primary teeth are just as important as permanent teeth; they are necessary for chewing, speaking, and appearance. More important is the fact that primary teeth create the space in the jaw for permanent teeth. Thus, caution during development and eruption is necessary to ensure proper dental growth.

Normal development of teeth can be interrupted by (1) disturbances in formation of the matrix (2) a lack of one or more of the necessary minerals, or (3) ingestion of toxic substances. Alterations in tooth formation can change the color, texture, and thickness of the tooth surface (Behrman & Vaughan, 1987). For example, tetracycline taken by a pregnant mother can permanently damage the color of the developing teeth. Therefore, caution should be exercised when giving medication to pregnant women or children up to 13 years of age. Enamel hypoplasia is characterized by pits of fissures on the enamel surface and can occur as a result of high fevers, chemical ingestion (i.e., excessive amounts of fluoride) at the time of enamel development, or deficiency of vitamin A, C, or D (Shafer, Hine, & Levine, 1974).

Prevention is the key to good oral hygiene. After teeth have erupted, parents should clean them with a washcloth until children can brush their own teeth (Fig. 12-6). Fluoride is another essential element in good oral hygiene. Fluoride affects the chemistry and structure of teeth during tooth development (birth through 13 years of age). After the tooth crown develops and before eruption, the tooth absorbs more fluoride. This continues during tooth eruption (Kula & Tianoff, 1982). The daily requirement of fluoride for prevention of tooth decay is 0.25 mg. If the drinking water is fluoridated and infants' formula is prepared with water, supplemental fluoride is not necessary during the first year of life. Infants who are solely breast-fed need 0.25 mg of fluoride supplement daily. Fluoride may be supplemented either by itself or in combination with vitamins. Drinking water is prepared for the infant by adding either tablets or drops of fluoride to achieve the proper concentration of 1 part per million. For example, one 2.2-mg tablet of sodium fluoride dissolved in 1 quart of water provides the proper concentration. Parents must be cautioned that exceeding the recommended dosage can cause mottling of the teeth.

Average Tooth Eruption During Infancy

  Mandibular Maxillary
Central incisors 5-7 mo 6-8 mo
Lateral incisors 7-10 mo 8-11 mo


20 Deciduous 32 Permanent
Symbol Name Symbol Name
Central incisor
Lateral incisor
Canine (cuspid)
1st molar
2nd molar
Central incisor
Lateral incisor
Canine (cuspid)
1st premolar (bicuspid)
2nd premolar (bicuspid)
1st molar
2nd molar
3rd molar
* Each quadrant (left or right half of each jaw) contains the teeth listed.