Formation of Caries-Like Lesions in vitro on the Root Surfaces of Human Teeth in Solutions Simulating Plaque Fluid

Abstract

Lesion formation on root surfaces of human posterior teeth was studied in acetate/lactate buffers with a background electrolyte composition based on plaque fluid analyses. Lesion depth after 28 days at 37°C was measured in relation to: the presence or absence of cementum; the concentration of undissociated buffer; the presence or absence of magnesium ions at plaque fluid concentration. Each factor was evaluated at several values of –log(ion activity product for hydroxyapatite): pI_HA. Solutions were formulated to minimize variation in pH, which varied by ≤0.03 for a given comparison (individual pI_HA) and by 0.42–0.82 over the range of pI_HA within experiments. Lesions on surfaces from which cementum had been ground were significantly deeper than on intact surfaces, but this is considered to be due to subsurface mechanical damage and not to a solubility difference. Neither the concentration of undissociated buffer nor the presence of magnesium ions significantly affected lesion depth. Lesion depth was strongly influenced by the correlated variations in pI_HA and pH. At pI_HA 54 and 55, only extremely shallow lesions formed. From pI_HA 56, lesion depth increased with increasing pI_HA. The results confirm that the solubility of the mineral of root tissues is higher than that of hydroxyapatite, but indicate that it is probably lower than suggested by Hoppenbrouwers et al. [Arch Oral Biol 1987;32:319–322]. For calcium concentrations of 3–12 mM, the critical pH for root tissue mineral was calculated as 5.22–5.66 assuming solubility equivalent to pI_HA 54 and 5.08–5.51 assuming pI_HA 55.

A Tissue-Dependent Hypothesis of Dental Caries

“…However, when a channel is demineralized by their action and dentin is reached, the community changes significantly and is predominantly proteolytic, and the main environmental pressure has an osmotic nature. At this stage, the tissue has a mineralized component with a lower proportion of hydroxyapatite and a higher critical pH which was estimated to be as high as 6.7 [Hoppenbrouwers et al, 1987], although lower values in the range 5.22-5.66 have been reported by recent in vitro work in root surfaces of human teeth [Shellis, 2010]. In addition, pH values in dentin caries lesions appear to be variable [Hojo et al, 1994].…”

Equine peripheral cemental defects and dental caries: Four case reports

“…The concentration of calcium and phosphate ions in saliva and dental plaque are important factors (Paschalis et al 1996). Some studies indicate that the concentration of magnesium (Mg) prohibits the dissolution of hydroxyapatite crystals (Paschalis et al 1996), while other studies claim that Mg is of no or minor importance (Shellis 2010). The pH-level when cementum starts to dissolve has been suggested to be as high as 6.7 (Hoppenbrouwers et al 1987), but this has been questioned by other researchers who have analysed the so called pI(HA) values (Shellis 2010).…”

Effect of Lesion Baseline Severity and Mineral Distribution on Remineralization and Progression of Human and Bovine Dentin Caries Lesions

“…However, comparatively few such studies were conducted on root caries lesions as researchers have generally focused on lesion creation under different conditions [Shellis, 2010;Moron et al, 2013] or the study of fluoride and/or potentially cariostatic agents on de-and remineralization of one particular lesion type in situ [Wefel et al, 1995[Wefel et al, , 2002 and in vitro [Xie et al, 2008;Qia et al, 2012]. Nonetheless, a series of mechanistic studies [Kawasaki et al, 2000;Smith et al, 2005;Preston et al, 2008] found that lesion baseline mineral distribution affects fluoride response under subsequent remineralization, that smaller lesions are more prone to remineralization and that, as shown for enamel [ten Cate and Duijsters, 1982], the mineral and fluoride content of the surface layer determines the rate of remineralization.…”