Influence of Calcium Phosphate and Apatite Containing Products on Enamel Erosion

Abstract

For the purpose of erosion prevention the present study aimed to compare the efficacy of two biomimetic products and a fluoride solution to optimize the protective properties of the pellicle. After 1 min of in situ pellicle formation on bovine enamel slabs, 8 subjects adopted CPP-ACP (GC Tooth Mousse), a mouthwash with hydroxyapatite microclusters (Biorepair), or a fluoride based mouthwash (elmex Kariesschutz) for 1 min each. Afterwards, samples were exposed in the oral cavity for 28 min. Native enamel slabs and slabs exposed to the oral cavity for 30 min without any rinse served as controls. After oral exposure, slabs were incubated in HCl (pH values 2, 2.3, and 3) for 120 s and kinetics of calcium and phosphate release were measured photometrically; representative samples were evaluated by SEM and TEM. The physiological pellicle reduced demineralization at all pH values; the protective effect was enhanced by fluoride. The biomimetic materials also reduced ion release but their effect was less pronounced. SEM indicated no layer formation after use of the different products. However, TEM confirmed the potential accumulation of mineral components at the pellicle surface. The tested products improve the protective properties of the in situ pellicle but not as effectively as fluorides.

Figure 1

Flowchart of the experiments.

Figure 2

Kinetics of calcium loss during incubation of enamel slabs for 120 s with and without application of different preparations in situ. Physiological 30 min pellicles (without rinse) and specimens without pellicle served as controls. In summary the erosion-preventive effect of fluoride was confirmed and could not be achieved by the calcium phosphate and apatite based products. Please note the different scale; n = 8 subjects; n = 24 enamel samples per subgroup; mean values ± standard deviation.

Figure 3

Kinetics of phosphate loss during incubation of enamel slabs for 120 s with and without application of different preparations in situ. Physiological 30 min pellicles (without rinse) and specimens without pellicle served as controls. On the whole, the phosphate release reducing effect of the calcium phosphate and apatite based products appeared inferior to fluoride. Please note the different scale; n = 8 subjects; n = 24 enamel samples per subgroup; mean values ± standard deviation.

Figure 4

Incubation of enamel slabs in HCl for 60 s after pretreatment with different products in situ, scanning electron microscopic evaluation.

Figure 5

Transmission electron microscopic images of the in situ formed 30 min pellicle without pretreatment (a) and with pretreatment with Biorepair mouth rinsing solution (b, d, e) and GC Tooth Mousse (c, f, g) at 98.000-fold magnification. For representative images of the influence of elmex Kariesschutz on in situ pellicle formation previously published by our workgroup see Weber et al. [33]. The enamel was removed during the preparation of the samples; the former enamel site is marked with an asterisk. After 30 min of physiological pellicle formation a fine electron-dense basal layer (basal pellicle) as well as a thin fine granular second layer can be detected at the enamel surface (a). Clearly neither rinses with Biorepair mouth rinsing solution ((b, d) contrasted, (e) uncontrasted) nor the application of GC Tooth Mousse ((d, f) both contrasted, (g) uncontrasted) after 1 min of pellicle formation seemed to affect or penetrate the characteristic appearance of the basal layer. However, in 10% of the analyzed pellicle, ultrastructural changes that are possibly due to an accumulation of electron-dense mineral components could be visualized in the outer parts of the in situ formed pellicle 28 min after pretreatment with the prophylactic products (d–g). While the inorganic electron-dense aggregates after rinsing with Biorepair mouth rinsing solution appear randomly distributed throughout the pellicle layer (d, e), electron-dense inorganic particles are more homogenously arranged and densely attached to the outer parts of the in situ formed pellicle after application of the Tooth Mousse paste (f, g).