title: Water content and apparent stiffness of non-caries versus caries-affected human dentin.
abstract: Caries-affected dentin contains less mineral and more water than surrounding normal dentin. Such dentin should be less stiff and should shrink more than normal dentin when dried. The purpose of this study was to test the relationships between the stiffness, shrinkage, and water content of caries-affected versus normal dentin. Extracted human carious third molars were stained with caries-detector dye and the occlusal surfaces ground down until only caries-affected dentin remained, surrounded by normal dentin. Dentin disks were prepared from these crowns placed in a aluminum well positioned under a modified thermal mechanical analyzer. Changes in specimen height and stiffness were measured following drying or static loading in both caries-affected and surrounding normal dentin. Core samples of these two types of dentin were used to gravimetrically measure water content. Two-way ANOVA and regression analysis was used to test the relationship between shrinkage versus water content, stiffness versus water content, and stiffness versus shrinkage. Caries-affected dentin was found to be less stiff and contained more water than normal dentin (p < 0.05). Regression analysis revealed highly significant inverse relationships between stiffness and water content, and stiffness and shrinkage (p < 0.0005).
authors.affiliation: Department of Operative Dentistry and Endodontology, School of Dentistry, Health Sciences University of Hokkaido, 1757 Tobetsu, Hokkaido 061-0293, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Ito
authors.forename: Takashi
authors.initials: T
authors.lastname: Saito
authors.forename: Franklin R
authors.initials: FR
authors.lastname: Tay
authors.forename: Ricardo M
authors.initials: RM
authors.lastname: Carvalho
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yoshiyama
authors.forename: David H
authors.initials: DH
authors.lastname: Pashley
mesh_terms: D003731:Dental Caries / Q000503:physiopathology*; D003804:Dentin / Q000737:chemistry* / Q000473:pathology*; D006801:Humans; D014867:Water / Q000032:analysis*
chemical_list: D014867:Water