THE IMPORTANCE OF PRIMARY TEETH

The general order of eruption of the primary dentition is central incisor, lateral incisor, first molar, canine, and second molar, with the mandibular pairs preceding the maxillary teeth. The loss of the deciduous teeth tends to mirror the eruption sequence – incisors, first molars, canines, and second molars, with the mandibular pairs preceding the maxillary teeth.

The high peak for caries to attack occurs at age 13, when only 5 percent of the primary teeth remain. The susceptibility to dental caries is a function of exposure time to the oral environment and morphological type. The increase in prevalence of dental caries among tooth types reverses their order of eruption.

However, the relative susceptibility of different tooth surfaces is a complex problem. Although dental caries of the primary dentition and loss of these teeth are sometimes thought of erroneously as only an annoyance, this belief fails to acknowledge the role of the primary teeth in mastication and their function in maintaining the space for eruption 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 normal occlusal relations in the permanent dentition. Thus, there should be no question of the importance of preventing and treating dental decay and providing the child with a comfortable functional occlusion of the deciduous teeth.

THE PRIMARY TEETH

The primary teeth are twenty 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, first molar and second molar.

Incisors 2/2 Canines 1/1 Molars 2/2 = 5 maxillary teeth per side

5 mandibular teeth per side

ERUPTION TIME OF PRODUCTION

The first primary teeth to erupt are usually the mandibular central incisors, at about 6 months of age. The last teeth to emerge, thus completing the primary dentition, are the maxillary second molars, at about 24 months of age.

The complete primary dentition is in the mouth from 2 years to 5 3/4

or 6 years of age, when no permanent teeth are present. Shortly after the 4th birthday, as the maxilla and the mandible grow larger, spaces develop between the primary teeth. This frequently concerns parents, but is perfectly natural in providing space for permanent incisors and canines, which are considerably wider than their predecessors.

Important Functions of Sound Primary Teeth

Efficient mastication of food.

Maintenance of a normal facial appearance.

Formulation of clear speech.

Maintenance of a proper diet.

Avoidance of infection and concomitant pain.

Maintenance of space and arch continuity for the emergence of permanent teeth.

Nomenclature

The process of exfoliation of the primary teeth takes place between the seventh and the twelfth years. This does not, however, indicate the period at which the root resorption the deciduous tooth begins. For only a year or two after the root is completely formed and the apical foramen is established, resorption begins at the apical extremity and continuous in the direction of the crown until the resorption of the entire root has taken place and the crown is lost from lack of support.

Mixed Dentition: Presence of Primary and Permanent Teeth

The first permanent teeth to erupt are usually the mandibular first molars and then maxillary first molars. They appear distal to the second primary molars when a child is between 5 3/4

and 6 years of age, they are commonly called “6 years molars”. It is important to recognize that these are permanent teeth and to care for them accordingly. With their eruption commences the mixed dentition period.

GENERAL CHARACTERISTICS OF PRIMARY TEETH

PRIMARY TEETH Smaller in size than the analogous permanent teeth

Whiter in color than the analogous permanent teeth

Less mineralized than the analogous permanent and become very worn (There is considerable attrition because of the expanding growth of the jaws and the various position of occlusion of the teeth before they are shed. Attrition, therefore is not a dentition trait, but a fact of life or normal occurrence.)

Shorter crowns with respect to their roots

Crowns have a marked consideration at the cervix, appearing as if they are being squeezed with a rubber band

PRIMARY TEETH The enamel seems to bulge close to the

cervical line, rather than gradually tapering

The layers of enamel and dentin are thinner than on permanent teeth

The pulp cavities are proportionally larger

Primary teeth have more consistence shapes than permanent dentition (fewer anomalies)

The crown on primary teeth appear bulbous, often having labial or buccal cingula.

ANTERIOR TEETH Usually there is no depression or perikymata on the labial

surface of the crowns of the incisors. These surfaces are smooth.

There are no mamelons on the incisal edge.

The cervical ridges on facial surfaces are prominent(running mesiodistally in the cervical third).

The cingula are prominent or seem to bulge and occupy about one third of the cervico-incisal length.

The roots are long in proportion to crown length, and are narrow mesiodistally.

The roots bend labially in their apical one third to one-half by as much as 10 degree.

POSTERIOR TEETH

The molar crowns are wide mesiodistally, yet very short cervico-occlusally.

the second molars are decidedly larger than the first molars.

the molars crowns have a narrow chewing surface.

the molar occlusal anatomy is shallow, in other words, the cusps are short, the ridges are not pronounced, and the fossa are correspondingly not as deep.

POSTERIOR TEETH

The buccal cusps on molars are not pointed or sharp, and their cusp slopes meet at very wide obtuse angle.

There are few grooves or deressions in the crowns.

The mesial cervical ridge is prominent(it is easy to distinguish rights from left)

Microscopically, the enamel rods at the cervix slope occlusally, unlike in permanent teeth where these rods slope cervically.

The root furcations are near the crown, with little or no root trunk.

POSTERIOR TEETH

The roots are widely spread beyond the outlines of the crown.

The roots are thin and slender.

The second molar roots are spread more widely than the first deciduous molar.(the opposite of the permanent molars)

CONTRASTS BETWEEN DECIDUOUS AND PERMANENT TEETH

DECIDUOUS V.S PERMANENT

DECIDUOUS

Also known as milk teeth, baby teeth, temporary teeth and primary teeth

The first set of teeth in the growth development of humans and many other mammals.

They develop during the embryonic stage of development and erupt—that is, they become visible in the mouth—during infancy.

PERMANENT

Permanent teeth are the second set of teeth formed in humans. There are thirty-two permanent teeth, consisting of six maxillary and six mandibular molars, four maxillary and four mandibular premolars, two maxillary and two mandibular canines, four maxillary and four mandibular

The first permanent tooth usually appears in the mouth at around six years of age, and the mouth will then be in a transition period with both deciduous teeth and permanent teeth (mixed dentition) until the last deciduous tooth is lost.

DECIDUOUS V.S PERMANENT

DECIDUOUS

They are usually lost and replaced by permanent teeth, but in the absence of permanent replacements, they can remain functional for many years.

PERMANENT

The first of the adult teeth to erupt are the permanent first molars that come through the gums at the back, right behind the last 'milk' molars. These first permanent molars are the most important teeth for the correct development of an adult dentition. Up to the age of thirteen years twenty-eight of the thirty-two permanent teeth will appear.

The full permanent dentition is completed much later. The four last adult teeth, one at the back of every arch will appear between the ages of seventeen and twenty-one years. This is the reason they are named wisdom teeth.

DECIDUOUS V.S PERMANENT

DECIDUOUS PERMANENT

Pulp Chambers and Pulp Canals

A Comparison Section of Primary and Permanent Teeth demonstrate

the shape and relative size pulp chambers and canals

Crown widths in all directions are large in comparison with root trunks and cervices.

The enamel is relatively thin and has a consistent depth.

The dentin thickness between the pulp chambers and the enamel is limited, particularly in some areas(lower second deciduous molar).

The pulp horns are high pulp chambers are large.

Primary roots are narrow and long when compared with crown width and length.

Molar roots of primary teeth flare markedly and thin out rapidly as the apices are approached. 

It is well, at all times, to study the comparisons between the deciduous

and the permanent dentitions. Further

variations between the microscopic form of the

deciduous and the permanent teeth will follow, with a detailed

description of each deciduous tooth.

Pulp Cavities Of Primary Teeth

Primary anterior teeth have pulp cavities that are similar in shape to the pulp cavities of the permanent teeth, but are much large in proportion because of the thinner, more form enamel covering, and the thinner portion of dentin in the deciduous teeth.

There are slight projections on the incisal border corresponding to the lobes, and there is usually no demarcation or constriction between the single canal and pulp chamber except on the mandibular central incisor.

THE END