That Not So Harmless Upper First Primary Molar Extraction
William M. Northway, D.D.S., M.S.
Journal of the American Dental Association, 131,
December, 2000, pp.1711-20.
Background:
Premature loss of primary molars has been associated with space loss and eruptive difficulties, especially when it is the second primary molar and when it occurs early -- not so for the first primary molar.
Methods:
From the dental cast sample used to study the effects of premature loss of deciduous molars, the thirteen cases that suffered premature loss of the upper first primary molar were revisited, this time using serial panarexes. These longitudinal cases were scrutinized to explain the irregular response in terms of dental migration. Two cases are presented.
Results:
In the earlier study, the author used digitized study casts and the concept of D-E Space to describe the dental migration that occurred after premature tooth loss. Using analysis of variance on data generated using the an instrument capable of measuring in 10ths of millimeters, the author generated findings regarding the amount of space loss, rate of space loss, effect of age at loss, amount of space regained when the succedaneous tooth erupted, and the effect on Angle classification. Finally, the author generated a simulation describing directional change; this revealed that the maxillary first primary molar loss resulted in a mesial displacement of the permanent canine on eruption.
Conclusions:
When the maxillary first primary molar is lost prematurely, the first premolar erupts in a more mesial direction than normal, off of the mesial incline of the second primary molar, and consumes the space for the permanent canine, which becomes blocked out.
Clinical Implications:
Rather than using a space maintainer following the premature loss of the maxillary first primary molar, measures should be taken to prevent the first premolar from erupting too far in a mesial direction.
Cases presented to demonstrate phenomenon
Due to editorial constraints, we are only allowed to present two of the upper first primary molar loss cases here (and, at that, we have been limited to the presentation of six registrations per case), but the ones presented are typical of the response to this phenomenon.
Acknowledgement:
The author whishes to acknowledge Dr. Arto Demirjian for his generous assistance and for allowing access to the Montreal growth data, Dr. Frans van der Linden for the use of the Optocom and advice, and the late Dr. Robert Moyers for providing the technical assistance of the Center for Human Growth and Development at the University of Michigan. Extreme gratitude is also due my wife, Carin for assistance and for allowing me the time to complete this labor of love.