Several Formation Patterns of Remarkable Perikymata in Human Permanent Teeth

Abstract

We examined the origins of the remarkable perikymata on the human permanent enamel surface mainly by using the 252 ground sections obtained from 252 teeth, although several investigators have reported their relationship in enamel hypoplasia. In these observations, the origins were roughly classified into 5 types (1-5). Some sigmoid or curbed lines of Retzius formed the wide or relatively narrow perikymata associated with the irregular dentin-enamel junction (DEJ) (type 1). One clear straight line of Retzius without the irregular DEJ formed the shallow perikymata followed with the clear or somewhat unclear lines of Retzius that converged towards the perikymata (type 2). The appositional enamel formation was concerned with the 2 sub-origins including the remarkable perikymata on the initial points of the appositional regular (type 3-1) and irregular enamel deposited on the resting lines of the already formed enamel (type 3-2). In mild enamel hypoplasia, the abnormal formation of the DEJ was concerned with the 2 sub-origins including the remarkable wave- or scallop-shaped DEJ which induced the disorder of enamel prism directions so that the irregular perikymata was formed (type 4-1) and the extremely step-shaped appearance of the DEJ which induced the abnormal perikymata (type 4-2). No incremental lines of Retzius concerning with the remarkable perikymata as well as the type 4 were also observed in some teeth, probably partial enamel hypoplasia (type 5). Some of their origins (types 1-5) were complexes.