INVESTIGATIONS INTO THE MINERALIZATION PATTERN OF HUMAN DENTAL ENAMEL

PART I. POLARIZED LIGHT STUDIES

¹ Oral Pathology Department, University of Sheffield, Sheffield, England

1. The present polarized light studies show that the mineralization of human enamel is a continuous process which occurs as follows: (a) The primary deposition of mineral matter starts shortly after the formation of the enamel organic matrix. This deposition, which is greatest in the earliest formed matrix at the cuspal portion of the amelodentinal junction, decreases in concentration in a regular manner as the enamel surface is approached. Neonatally and postnatally formed enamel matrix may at this stage show sharp variations in mineral content parallel to the striae of Retzius. (b) The primary deposition then advances cervically along the amelodentinal junction and peripherally toward the enamel surface. (e) Secondary areas of slightly increased mineralization then appear in the outer third, cervical, and surface enamel. (d) The primary deposition continues to expand cervi- eally and peripherally, at first roughly parallel to the striae of Retzius and finally almost parallel to the enamel surface, gradually obliterating the secondary areas and variations along the striae.

2. Within a given dentition, the order of decreasing mineral content during development is: central incisor, lateral incisor, first molar, canine, and second molar.

3. Crystalline mineral matter is detectable in the organic enamel matrix shortly after its deposition.

4. At no time during the whole process of mineralization, as visualized in polarized light, is there an influx of crystalline mineral matter starting at the surface of the incisal edge and proceeding cervically at right angles to the striae of Retzius.