Yasuo Miake et al.: Variation in the Teeth Color and Structural Changes in Enamel Rod Sheath Journal of Hard Tissue Biology 25[2] (2016) 131-136 © 2016 The Hard Tissue Biology Network Association Printed in Japan, All rights reserved. CODEN-JHTBFF, ISSN 1341-7 649
Original Variation in the Color of Japanese Teeth and Structural Changes in Enamel Rod Sheath Associated with Age Yasuo Miake1), Sei Tsutsui2) and Yoshiyuki Eshita2) Department of Histology and Developmental Biology, Tokyo Dental College, Tokyo, Japan Personal Health Care Products Research, Kao Corp., Tokyo, Japan (Accepted for publication, February 10, 2016) 1) 2)
Abstract: This study was intended to clarify the changes in the color of teeth and enamel rod sheath with age. A total of 14 first premolars taken from patients between the ages of 10-70 years old were used in this study. Photographs of the buccal surface of teeth were taken and the tone was converted into color system marked as L*, a* and b* using image processing software. Thick sections of 1.5 mm traversing the tooth axis were prepared and the enamel translucency and color of enamel and dentin were determined in the same manner. Correlation analysis was carried out between the clinical color of the buccal surface and age, enamel color and age, dentin color and age and translucency and age. The sections were embedded in resin and the polished cross section was observed a backscattered electron image with SEM. The observation sites were the following: outer of the enamel, middle layer and deep layer (near the dentin-enamel junction). The structure of the enamel rod sheath was the focus of observation. The area and width of enamel rod sheath were measured from SEM images. Correlation analysis between color, area of enamel rod sheath and age were carried out with these data. Results showed that color of enamel and dentin became darker with age; the color of the entire buccal surface became dark reddish and yellowish but it was not due to increased permeability of enamel. The enamel rod sheath was clear in teeth of young people but it showed a rapid decrease with age. From the results, the crystal gap and enamel rod sheath suppress the reflection of the color of underlying dentin with the tendency of scattering the light from the outer layer to the deeper layer in teeth of young patients. However with increasing age, the crystal gap and enamel rod sheath decrease thereby strongly reflecting the color of dentin resulting to a darker color. Thus, microstructural changes in enamel affect the color of the tooth. Key words: Enamel rod sheath, Post-eruptive maturation, Tooth color, Backscattered electron image
Introduction
color of enamel and post-eruptive maturation of enamel rod sheath due to aging.
Studies on color of teeth have been done in the past and it is known that teeth become dark yellow with age1,2). Factors such as adhesion and penetration of organic matter to the enamel, yellowing of dentin, thinning of enamel due to attrition and abrasion and
Materials and Methods The specimens were first premolar without caries or any repair and were removed either for orthodontic or periodontal disease.
even increase in transparency of enamel due to aging have been considered. Changes in enamel during post-eruptive maturation
Consent was obtained from all patients. A total of 14 teeth were used which came from various ages: 3 teeth from 10’s, 6 teeth
associated with aging create a significant impact on the structure of enamel rod sheath and growth of enamel crystals. Furthermore,
from 20’s, 1 tooth from 30’s, 2 teeth from 50’s, 1 tooth from 60’s, 1 tooth from 70’s. The study was approved by Tokyo Dental
it is involved in enamel acid resistance, hardness and a change of the color3-8). However, a detailed study on the post-eruptive matu-
College Ethics Committee (Approval Number: 432).
ration and change in the color of teeth associated with aging are very few. This study aimed to clarify the relationship between Correspondence to: Dr. Yasuo Miake, Department of Histology and Developmental Biology, Tokyo Dental College, 2-9-18 Misaki-cho, Chiyoda-ku, Tokyo, 101-0061 Japan; Tel.: +81-3-6380-9274; Email:
[email protected]
Color analysis and translucency The harvested first premolars were washed and then fixed in 10% formalin solution. Then after, specimens were rinsed with water and the surface moisture was removed. Photographs of the crown were taken
131
J.Hard Tissue Biology Vol. 25(2):131-136, 2016 Mitani Co, Tokyo, Japan). Extraction was carried out in three
using a digital camera (D1x, Nikon) equipped with polarizing filters to remove specular reflection in the dark box. The color in the
places per tooth and the area of enamel rod sheath was calculated by dividing the area of enamel rod sheath and measurement range
center of the buccal surface (3 × 4 mm) was processed using an image software (Photoshop, CS3, Adobe Systems) and the value
area. Furthermore, the binary images of enamel surface layer of three teeth from patients in their 10’s were used to calculate the
was converted into L*, a*, b* color space. Then after, thick sections of 1.5 mm traversing the tooth axis were prepared and
width of enamel rod sheath using image analysis software (WinROOF, Ver. 6.6). Therefore, the measurement per tooth was
photographs of the polished cross section (#4000) were taken in the same manner. Photographs of the enamel on the buccal surface
done in three visual fields in five sites and the average in 45 locations in 9 viewings was calculated. The relationship between age, color
without enamel lamellae and gaps and dentin near the dentinenamel junction were taken in 5 locations (0.5 × 0.5 mm) each.
and area of enamel rod sheath was calculated using SPSS statistics and correlation analysis was carried out using Spearman’s rho.
The translucency of enamel was measured using a standard plate of known enamel translucency in gray scale (G) value for each site
paper and diamond lapping film (0.5 µm) and then subjected to carbon coting. The cross section of enamel was observed by
Results Relationship of color of teeth and age When the color of crown was compared to age, negative correlation between L* and age ( = 0.535, p
