Thickness of Enamel at the Base of Pits and Fissures in Human Molars and Bicuspids

Abstract

The pattern of distribution of deeply invag-inated pit and fissure areas and the enamel thickness at the base of these areas in a pooled sample of 40 upper and lower 1st and 2nd molars and 12 upper 1st and 2nd bicuspids was investigated, using 1312 undecalcified semiserial sections and a graphical reconstruction technique. In all but one of the 52 teeth examined, the presence of deeply invaginated fissure areas was noted. Although there was no fixed relationship between tooth morphology and distribution of these areas, they were present to about the same extent in the molar and upper bicuspid teeth sectioned. The use of a dental probe to gauge the thickness of enamel in such areas is bound to give the clinician a misleading impression, since the thickness estimate could be optimistic by a factor of 6 times in the molars and 5 times in the bicuspids. The contour of the occlusal opening of the fissure corresponded to the contour of the underlying dentinoenamel junction but not to the contour of the enamel surface along the fissure base. This study shows that areas of deep invagination in the enamel are much more prevalent than was hitherto suspected.