The health of the mouth and rest of the body would be improved, in most persons, by removal of the four least healthy teeth, one in each quadrant. Retention of a tooth that nature has doomed to loss, by caries, induces carious processes in other teeth because there is not enough nourishment for all of them. Resistance of first molars to caries is often diminished when third molars begin to use their alloted nourishment for growth. Gingivitis and Vincent infection often occur because of retention of teeth that should have been removed. Lateral incisors and other teeth in the same quadrant, when all teeth are present, are often diseased. Before filling large cavities—and often before treating caries—study should be made of the unerupted teeth to determine their position and chances of normal eruption. Extraction, then, might be infinitely better treatment than filling, thus effecting a possible cure rather than applying a questionable remedy.
At average age of twenty, only 11.8 percent of 1230 college students—who had not lost one or more teeth—had room in their mouths for the third molars. In 17.2 percent, either one or more extractions afforded room for third molars. In nine out of ten cases either a third molar, or another tooth posterior to the cuspid, should be removed by the age of nineteen. The health of the remaining teeth is enhanced by this treatment—exposed pulps deposit secondary dentin for protection, and diseased gingiva returns to normal.
Reference: Nutr. Den. Health, 1937.