VARIATION IN TOOTH POSITION FOLLOWING EXTRACTION OF FIRST MOLARS IN RELATION TO INCIDENCE AND DISTRIBUTION OF DENTAL CARIES

¹ Dental Service, New York City Vocational Schools, New York, N. Y.

According to the data presented, the boys and girls examined at 15 to 19 years of age show an increase of "exteeth" in the maxilla over the mandible when they have 1 to all 4 M1's extracted, regardless as to which jaw the extraction occurred. The rate of distal drift of PM1 and PM2 is more frequently even in the maxilla than in the mandible. The difference in the rate of movement between PM1 and PM2 in the mandible persists over a longer interval of time after the extraction of M1 than in the maxilla. The distal drift of the maxillary PM1 and PM2, as is indicated in the foregoing, is accompanied by loss of contact points without apparently sufficient separation of the respective teeth occurring to allow food debris to be freely removed from between these teeth. In the mandible the difference in the rate of drift between PM1 and PM2 is greater than in the maxilla and food may be expelled more readily from between these teeth. Furthermore, in cases where the mandibular M1 has been extracted, there is an elevation or continuous eruption of the opposing teeth and consequent loss of contact point in the maxillary teeth. It is reasonable to assume, therefore, that the difference in the rate of drifting between PM1 and PM2 in the respective jaws is responsible for the increase in exteeth distribution in the maxilla in mouths from which 1 to 4 M1's have been extracted.

On the basis of the data herein presented, it appears that when the dentist fills first molar teeth, he does not simply perform a mechanical job which preserves these important teeth for use in chewing, but he also helps to maintain the occlusal relationship of all teeth in the mouth and lowers the incidence of caries in the mouth as a whole.