Harmful effects, following extraction of first permanent molars, are well defined in adolescent boys and girls nearing final stages of growth and development; second molars do not come forward alone to occupy the spaces made by extraction of first molars; general disturbance in occlusion ensues. The younger the child, when a first permanent molar is extracted, the greater the harmful effects on occlusion and the higher the incidence of caries. In children between 15 and 19, there is concomitant increase in incidence of ” exteeth ” [see definition in (4), below], this increase showing high degree of correlation with increase in number of lost first molars. A child with one to four first permanent molars filled or carious shows an increase in incidence of caries in the mouth as a whole corresponding with increase of fillings or caries in his first permanent molars. Incidence of caries is intensified, after extraction of any first molar, and becomes cumulative with each succeeding extraction of a first molar. Owing to individual factors, spaces left after extraction of first permanent molars do not close uniformly in all cases, doing so faster in the upper jaw than in the lower. Maxillary second molars show comparatively greater amounts of change in position than maxillary second premolars or mandibular second molars. Mandibular second premolars and second molars show close relationships in amounts of change of position at various intervals after extraction of first molars. Effects of first-molar extractions are manifested in increase in caries, occlusal disturbances, changes in facial contour and appearance, and frequently also in interference with speech, general physical growth, and development. The fact that from the average boy or girl, at 15, almost two first molars have been extracted is additional proof that periodic dental examination, and treatment when necessary, should be begun as soon as teeth erupt. The havoc initiated in the dentition as a whole by extraction of first permanent molars, without provision for space maintenance for preservation of occlusal relationships, is a condition that should be recognized, publicized, and prevented by the practising dentist.
(1) In a group of 500 boys and girls (ages 15 to 19) there was but slight increase in number of first molars lost when correlated according to age of child. The peak for the ” one-molar-lost ” group was at age 13; for the ” two-molarslost,” at age 14 ; for the ” three-molars-lost,” at age 14 ; for the ” four-molarslost,” at age 15. First permanent molars are lost in increasing frequency in the following order : upper right, upper left, lower right, the lower left being the one most frequently lost-2.3 times as many lower first molars are lost as uppers. There is a high degree of correlation between the right and left sides, with a slight increase of upper and lower left sides over the respective quadrants on the right side. An average of 1.88 first permanent molars were lost, per child, between 15-19 years.
(2) After extraction of a first permanent molar the remaining teeth show changes of position with regard to inclination, rotation, elevation (continuous eruption), and bodily movement. There is deflection in the median line and recognizable imbalance in facial symmetry. Changes in position of remaining teeth are especially marked for premolars and second molar in the jaw-quadrant from which the first molar has been extracted. In 67 percent of such quadrants, there is pronounced change of position of both premolars and second molar. In 5.8 percent of jaw-quadrants there is change of position of premolars only ; in 13.6 percent, in position of second molars only. The last two categories (distal movement of premolars only, or mesial movement of second molars only) were not found in jaw-quadrants from which first molars had been extracted for a period longer than eight years, while distal movement of premolars plus mesial movement of second molars occurred at all intervals from three months to twelve years. All premolars tend to show change of position distally, and second molars mesially, in quadrants from which first molars have been extracted.
(3) Spaces remaining after extraction of first molars show an average tendency to decrease in size faster in the upper jaw than in the lower. Upper second molars show greater amounts of change in a forward direction than lower second molars ; lower second premolars tend to change position distally more than upper second premolars, the amount of change in position approximating that of the lower second molar.
(4) It is suggested that teeth having physical abnormalities acquired after eruption, including extracted teeth, be termed ” exteeth.” Children from whom first molars have been extracted show an average of three “exteeth ” more, each, than children whose first molars are present. At each age between 15 to 19 years, twice as many children who lost first molars had ten or more ” exteeth,” each, when compared with similar age-groups whose first molars were present. At 19 years, 40 percent of these children whose first molars were present had 10 or more ” exteeth,” each ; 80 percent of those who lost first molars had 10 or more ” ex- teeth,” each. The number of ” exteeth ” per child increased with age, from 15 to 19—and also with the actual number, from one to four, of first molars lost.
(5) The average number of carious cavities (or fillings) in children increases
in direct ratio to the number of carious or filled first molars when all of these teeth are present. In children from whom one to four first molars have been extracted, there is an increase in number of cavities (fillings) in direct ratio to number of first molars extracted and to number of cavities (fillings) in the remaining first molars. In all cases, children from whom first molars have been extracted show higher incidence of caries than those having a corresponding number of first molars filled or carious but retained. Therefore, (a) number of filled or carious Mi‘s can be used as an index to incidence of caries in a mouth as a whole; (b) extraction of first permanent molars is a direct cause of increase in caries in these children; and (c) orthodontic and facial sequelae following disturbed occlusion are caused by drifting of remaining teeth in jaw-quadrants from which first permanent molars have been extracted. These factual data show the advantage of retaining first permanent molars; the fallacy of extracting these teeth as an orthodontic measure; and reasons for immediate replacement or maintenance of the spaces left by extraction of first molars, regardless of the child’s age after one or more of these teeth have been lost.
References: Int. J. Orthod., 1937; J. Am. Den. Assoc., 1938; Bul. Den. Soc. State N. Y., 1938.