Effect of Whole Saliva Components on Enamel Demineralization In Vitro

Abstract

The aim of the present study was to use an in vitro enamel demineralization model (1) to confirm that whole saliva pretreatment conferred acid resistance to dental enamel and (2) to determine whether this phenomenon was attributable to specific salivary proteins, minerals, lipids, or some combination of these. Crowns of human teeth, each with one exposed window, were prepared in groups of ten. They were each pretreated by immersion individually in 4 ml of either (1) clarified whole saliva for 18, 72, or 168 h, (2) dialyzed saliva (3500 MWCO membrane), (3) the "flow-through" fraction from a DEAE separation of whole saliva (neutral and basic proteins), (4) the "eluted" fraction of a DEAE separation of whole saliva (anionic proteins), or (5) a combination of salivary lipids and the DEAE "flow-through" fraction of whole saliva (neutral and basic proteins). Control groups were group 6 with no pretreatment, group 7 pretreated for 168 h in a borate buffer (5 mmol/l), and group 8 pretreated in a mineral solution containing calcium (0.7 mmol/1) and phosphate (2.6 mmolfI). The crowns were then demineralized for 7 d in vitro (0.1 mol/I acetate, 1 mmol/I Ca and phosphate, pH 5.0) to produce artificial caries-like lesions. Lesions were assessed by cross-sectional microhardness profiles, and mineral loss (AZ, Rim x vol% mineral) calculated. Mineral loss (AZ) values decreased linearly with the square root of time of pretreatment by whole saliva, confirning a time-dependent protective effect of salivary pellicle against demineralization of enamel. Pretreatments (168 h) by whole saliva (group 1), dialyzed saliva (group 2), and lipid/'flow through" proteins (group 5) gave equivalent protection (approximately 55%). However, no protection was provided by DEAE-separated protein fractions (no lipid present) or by the mineral alone. The protection of surface enamel against demineralization appears to be given by a combination of specifically adsorbed salivary lipids and proteins.

Efecto In Vitro de las Bebidas Refrescantes sobre la Mineralización de la Superficie del Esmalte Dentario de Piezas Permanentes Extraídas

“…Estos cristales de hidroxiapatita son susceptibles a la acción de los ácidos constituyendo esta característica el sustrato químico que da origen a las caries y erosión dental (Mas). La desmineralización se produce cuando la acidez se sitúa por debajo del pH 5.5 que es el pH crítico de la hidroxiapatita, de esta forma se producirá una liberación de iones de calcio y fosfato desde el esmalte hacia el medio circundante (Featherstone et al, 1993) provocando erosión en las piezas dentarias, éste término deriva del latín erodere, erosi, erosum (corroer) el cual describe el proceso de destrucción gradual de la superficie de un cuerpo, generalmente por procesos electrolíticos o químicos (Liñan et al, 2007), no incluyendo la participación de microorganismos de la flora bacteriana intraoral (Narváez, 2008). En los últimos años ha existido un gran incremento en la prevalencia de la erosión dental, sobretodo en la población de niños y adolescentes, siendo uno de los factores de riesgo más importante la ingesta de bebidas carbonatadas (Liñan et al), bebidas ácidas, light, deportivas y jugos de frutas (Zero &Lussi).…”

Salivary carbonic anhydrase isoenzyme VI

“…This adsorption is assumed to be dependent on the chemical characteristics of the surface as well as the properties of the particular proteins. The enamel pellicle evidently prevents demineralization of the surface hydroxyapatite, increasing its acid resistance, although the mechanisms responsible for this effect remain elusive (Zahradnik et al 1976(Zahradnik et al , 1977(Zahradnik et al , 1978Kousvelari et al 1980;Meurman & Frank, 1991;Featherstone et al 1993). It is also thought to prevent calculus formation on the dental surfaces by controlling the precipitation of calcium phosphate from supersaturated saliva (Hay & Moreno, 1989).…”

Effect of Hydroxyapatite and Sodium Hexameta Phosphate Application on Demineralized Enamel and Dentine

“…In contradication, (15) reported that after free calcium and phosphate were removed from whole saliva by dialysis, the remaining organic molecules imparted the same resistance to demineralization as whole saliva.…”