Stereomicroscopic study of 700 root apices of maxillary and mandibular posterior teeth.

T HIS study is a supplement to my previous article entitled “A Stereomicroscopic Study of the Root apices of 400 Maxillary and Mandibular Anterior Teeth. “l I have thus completed the analysis of posterior as well as anterior teeth.2 The purpose of this article is to establish with greater precision than has heretofore been attained the morphology of the canal at the root apex, the major apical foramina, and accessory apical foramina. In examining past and current literature, I noted that in previous investigations of pulp canal morphology the techniques employed in the preparation of the teeth for study may have distorted the specimens. Therefore, any descriptions, evaluations, or conclusions drawn from such studies may have been inaccurate. The use of the stereomicroscope has given a view of these areas in depth and has provided a better opportunity to observe, analyze, and compare anatomic areas. In this study, the basic principle was to use specimens which had been carefully treated and prepared so as not to mar the natural detail. The specimen apices were cut at a 7 mm. distance from the apex and cemented, flat end down, on glass microscope slides. The apices were then studied under the threedimensional microscope, which had a micron measuring device on the lens. The measurements of the foraminal openings, as noted in Tables I and II, were tabulated to two decimals. Considerable judgment had to be used in classifying round, oval, irregular, and funnel-shaped openings, as many of these shapes were of the borderline variety. Some orifices which appeared to be foramina, such as indented cementurn, seemed to enter the main canal, but gradations of hard to soft cementum and dentine made classification difficult. In order to determine accurately the percentage of accessory foramina present, it was also necessary to explore, penetrate, and study the cut ends of