Amelogenesis imperfecta

Definition

Primary dental development involves the development of the primary, first, or baby teeth.

Description

The primary teeth usually begin to appear about six months after birth. Most children have all 20 primary teeth by age two. The eruption of teeth is associated with teething, a process often causing symptoms such as drooling, disturbed sleep, irritability, swollen gums, and, sometimes, a low-grade fever. While there are typical patterns of tooth eruption, these patterns can vary greatly from child to child.

Tooth development in the upper jaw

The primary teeth in the upper jaw are:

• Central incisors, which erupt between ages seven and 12 months and fall out around 6 to 8 years of age.

• Lateral incisors, erupting between nine and 13 months of age and falling out by the time a child reaches seven or eight years of age.

• Canines or cuspids, which appear around 16 to 22 months of age and fall out at 10 to 12 years old.

• First molars, emerging between 18 and 19 months and falling out at 9 to 11 years of age.

• Second molars, which come in at 25 to 33 months old and fall out at 10 to 12 years of age.

Tooth development in the lower jaw

The primary teeth in the lower jaw are:

• Central incisors, which erupt at six to 10 months and fall out at five to six years.

• Lateral incisors, erupting at seven to 16 months and falling out between seven to eight years of age.

• Canines, which come in at 16 to 23 months of age and fall out between nine and 12 years of age.

• First molars, emerging at 12 to 18 months and falling out at nine to 11 years of age.

• Second molars, which erupt between 20 and 31 months and fall out at 10 to 12 years of age.

Function

Teeth are for chewing and crunching food. They are attached to the tooth root, which anchors them to the jaw bone. The visible part of the tooth is the crown and its hard covering is enamel, which is the hardest substance in the body. The enamel covers a material, called dentin, which makes up the majority of each tooth. Deeper inside the tooth is the pulp, which includes nerve sensations and provides nutrients to the tooth. Baby teeth, like permanent teeth, include pointier incisor and cuspid teeth capable of tearing meats and rounder, flatter molars for grinding foods such as vegetables.

Role in human health

Primary teeth have many roles. They allow children to chew properly, helping them to maintain sound nutrition. Primary teeth are important for good pronunciation and speech and are a key aesthetic facial feature. Another function of primary teeth is that they guide permanent teeth and contribute to healthy jaw development.

Common diseases and disorders

Premature primary tooth loss

At times, primary teeth fall out or are knocked out too early. The resulting space might become too small for the erupting tooth, so dentists often fill the space with a space maintainer to ensure adequate room for permanent tooth eruption.

Dental decay or caries

Dental decay often begins in childhood. Caries, also known as cavities, start as an interaction between bacteria, which normally occurs on teeth, and sugars in the diet. The bacteria and sugars produce an acid, which causes teeth that are exposed to it to lose mineral. Cavities that form in the primary teeth can spread into the developing permanent teeth below. To treat the decay, the dentist has to remove it and fill the tooth with silver- or tooth-colored materials. The fluoride found in drinking water helps prevent cavities and has resulted in far fewer children developing dental caries. Dentists also use sealants to prevent decay. Sealants are clear or shaded plastic materials, which dentists apply to the chewing surfaces of the back teeth. The sealants coat the teeth and form a barrier to protect against bacteria.

Early childhood dental caries

Early childhood dental caries is a dental problem that frequently develops in infants that are put to bed with a bottle containing a sweet liquid. Bottles containing liquids such as milk, formula, fruit juices, sweetened drink mixes, and sugar water continuously bathe an infant's mouth with sugar during naps or at night. The bacteria in the mouth use this sugar to produce acid that destroys the child's teeth. The upper front teeth are typically the ones most severely damaged; the lower front teeth receive some protection from the tongue. Pacifiers dipped in sugar, honey, corn syrup, or other sweetened liquids also contribute to early childhood dental caries. The first signs of damage are chalky white spots or lines across the teeth. As decay progresses, the damage to the child's teeth becomes obvious.

Injuries, such as falls

Falls and athletic injuries can result in damage to the primary teeth and gums. Dentists should examine these injuries as soon as possible after they occur because they can often save teeth even if they have been knocked out of the socket.

Amelogenesis imperfecta

Amelogenesis imperfecta is a genetic defect in tooth enamel formation. It can appear as a localized row or pits of linear depressions or as generalized tooth discoloration, varying from white to translucent brown. Some children have no enamel at all, or their teeth might look hard or rough on the surface. Sometimes, the enamel of children with amelogenesis imperfecta looks soft and mottled. It can also appear honey-colored, yellow, orange, or brown. Dentists often treat amelogenesis imperfecta by placing crowns or fillings to restore the primary teeth. Fluoride supplements can help. Regular dental care to monitor amelogenesis imperfecta is important. It is not known how this condition affects the permanent teeth.

Bite problems and growth and development disturbances

Bite problems, or malocclusions, can be hereditary or caused by missing or extra teeth from birth, thumb sucking, or early loss of baby teeth. Bite problems can affect a child's appearance, as well as his or her ability to talk, eat, and digest foods properly. Dentists or orthodontists can help correct malocclusions.

Developmental abnormalities

Discoloration or deformation of teeth can occur in the primary dentition. The problem might affect a few of the teeth or the entire dentition. These defects can affect normal chewing, disrupt normal tooth development, and adversely affect appearance. Illness, high fevers, or some medications can cause unerupted teeth to erupt discolored.

Hard tissue formation begins (weeks in utero)Eruption (months)Root completed (years)MaxillaryCentral incisor148-121.5Lateral incisor169-132Canine1716-223.25First molar15.513-19 boys
14-18 girls1.5Second molar1925-333MandibularCentral incisor146-101.5Lateral incisor1610-161.5Canine1717-233.25First molar15.514-182.25Second molar1823-31 boys
24-30 girls3

Data from Lunt, R.C. and D.B. Law. "A review of the chronology of eruption of deciduous teeth." J. Am. Dent. Assoc. 89 (Oct. 1974): 872.

Key Terms

Amelogenesis imperfecta

An enamel formation defect.

Canines or cuspids

Second to last primary teeth on each side of the back of the upper and lower jaw.

Caries

Another word for dental cavity or decay.

Dentition

Development and eruption of teeth.

Fluoride

A chemical compound containing fluorine that is used to treat water or applied directly to teeth to prevent decay.

Malocclusions

Bite problems caused by malpositioned teeth.

Sealant

A thin plastic substance that is painted over teeth as an anti-cavity measure to seal out food particles and acids produced by bacteria.