The Possible Role of Starch in Oral Calcification: The In Vitro Formation of Hydroxyapatite is Regulated by a Combination of Protein and Mineral Content in Dietary Starch Flour

Saburo Hidaka*, 1, Yoshizo Okamoto2, Suehiro Tsukamoto3, Akiko Oishi4
1 Department of Dental Hygiene, Fukuoka College of Health Sciences, Fukuoka, 814-0193, Japan
2 Department of Den-tal Engineering, Bioengineering Section, Fukuoka Dental College, Fukuoka, 814-0193, Japan
3 Department of Growth and Development, Section of Dentistry for Persons with Disabilities, Fukuoka Dental College, Fukuoka, 814-0193, Japan
4 Department of Health and Welfare, Fukuoka College of Health Sciences, Fukuoka, 814-0193, Japan

© 2008 Hidaka et al.;

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Dental Hygiene,Fukuoka College of Health Sciences, 2-15-1, Tamura, Sawara-Ku, Fukuoka 814-0193, Japan; Tel: 81-92-801-0411, Ext. 108; Fax: 81-92-801-4473; E-mail:


The effects of twelve kinds of dietary starch flour, i.e. rice (non-glutinous and glutinous), wheat (soft, medium, and hard), barley (roasted), buckwheat (inner layer and straight), corn, sweet potato, kudzu, and tapioca on in vitro calcium phosphate precipitation were investigated using the pH drop method. The induction time was elongated by the addition of all of the kinds of flour. Although the rate of amorphous calcium phosphate (ACP) formation was not affected, the rate of transformation of ACP to hydroxyapatite (HAP) was either stimulated or inhibited by the different types of flour. The following observations were made: (1) When the lipid content below 0.2% (w/w), any of the types of starch had a stimulatory effect on the transformation of ACP to HAP. (2) When the lipid content around or above 1.0% (w/w), the value of the product of (protein content) ≥ (mineral content) seems to determine the effect of starch.

Keywords: Amorphous calcium phosphate, calcium phosphate precipitation, dietary starch flours, hydroxyapatite, oral calcification.