Dental Development

Process of development of the permanent teeth.

Dental development begins in the first trimester of prenatal life, when the tips or cusps of the primary or deciduous teeth start to form, and it ends (in most individuals) when the root ends of the third permanent molars fully calcify and finally close. From start to finish, development and exfoliation (shedding) of the 20 deciduous teeth and the development of the 32 permanent teeth occupies a period of more than two decades.

"Teething," the emergence of the deciduous teeth, begins in the middle of the first year of life, and ends in the second year with the emergence of the second deciduous molars (symbolized as "dm2"). Some discomfort is associated with the piercing of the gums, especially so for the large deciduous molars; the permanent teeth may also cause some discomfort in the course of emergence through the gums, especially the permanent molars, which have no predecessors to pave the way.

There are in all 20 deciduous teeth, i.e., 2 incisors, one canine, and two deciduous molars in each of the four jaw quadrants of the jaw. The successional or permanent teeth (typically 32 in number) are also shown relative to the occlusal level (horizontal line) and the midline of the face.

Except for the earliest stages of prenatal dental development and with the possible exception of the third permanent molar (M3), girls are advanced over boys in dental development, by as much as six percent or so. Girls also have slightly smaller tooth crowns and slightly shorter tooth roots, allowing sex identification of cadavers and skeletalized material.

To a larger extent, both dental development and tooth size are under genetic control, as shown in twin and sibling comparisons, and there are population differences both in developmental timing and in crown size and shape. Dental development is also affected by such endocrine disorders as hypopituitarism and hypothyroidism. Dental development is slightly advanced in obesity and slightly retarded in chronic malnutrition.

Some teeth may fail to form, a condition known as agenesis, especially so for the third molar (M3) and—sometimes—the lateral (2nd) incisors, i.e., 12. When M3 and especially 12 are missing, the remaining teeth tend to be reduced in size and late developing as well. Supernumerary (extra) teeth also exist, though rarely, usually as relatively shapeless pegs, but in some cases there may be a complete extra molar (M4) that is fully formed.

MOUTH PROTECTORS

The American Dental Association, in cooperation with the Academy of Sports Dentistry, recommends that all participants in contact sports wear protective mouth gear. Since 1962, high school and college-level football players have been required to wear faceguards and mouth protectors during practice sessions and in competition, preventing an estimated 200,000 injuries per year. Many experts go beyond contact sports, to recommend that mouth protectors be worn during any recreational sport where there is danger of mouth injury, including surfing, basketball, skateboarding, gymnastics, racquet sports, and field hockey.

The ADA recommends wearing a mouth protector when participating in these sports:

Acrobatics, gymnastics, skateboarding, and skydiving
Basketball and volleyball
Boxing, martial arts, weightlifing, and wrestling
Discus throwing and shotputting
Field hockey, football, rugby, and soccer
Handball, lacrosse, racquetball, and squash
ice hockey and skiing
Surfing and water polo

There are three types of mouth protectors: the ready-made (one size fits all) mouth protector; the mouth-formed mouth protector; and the custommade protector. The preferred design covers only the upper teeth. This is more comfortable for the athlete and protects the most often injured. In addition, since the upper teeth overlap the lower teeth for most people, the mouth guard offers some protection for the lower teeth as well.

Young athletes who wear removable orthodontic appliances, such as retainers, should remove them when playing contact sports.

Traditionally, the emergence of the first deciduous or baby tooth was taken as an indication to extend the infant's diet beyond breast milk alone. (Nowadays cereals and other foods are introduced much earlier then in the past.) In turn, completion of the deciduous dentition was taken as a readiness for solid foods, now introduced far earlier than the end of the second year of life. Traditionally also, emergence of the second permanent molars was considered evidence of the ability to perform "adult," rigorous labor.

The major disorders of the dentition during childhood are dental caries (cavities), malocclusion (malpositioning of the teeth), and less commonly, accidental injury. The incidence and prevalence of dental caries increased rapidly during the 19th century until the middle of the 20th century, consistent with increased consumption of sucrose. Addition of fluorides to the water supply and the use of topical fluorides reversed the incidence of caries, and many dental schools have been closed as a consequence.

Malocclusions are now ubiquitous, with over 90% of children affected to some degree. Though the actual cause of malocclusion is not known, satisfactory dental alignment can be achieved by orthodontic intervention.

Many accidental injuries occur during participation in contact sports. Most injuries of this type can be prevented by the use of mouthguards and protective headgear.

Dental Development

MOUTH PROTECTORS

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