Enamel mineralization by calcium-containing bicarbonate toothpastes: assessment by various techniques.

Howard E. Strassler, DMD

Charig A, Winston A, Flickinger M. Compend Contin Educ Dent. 2004;25(9 Suppl 1):14-24.

Abstract

Surface defects such as scratching, acidic erosion, and natural dimpling of the tooth enamel can significantly affect its cosmetic appearance. There are many analytical techniques that can be used to view the surface of enamel and to assess the effect of surface treatments. Light microscopy, scanning electron microscopy (SEM), profilometry, and atomic force microscopy (AFM) can usefully be applied to viewing mineral surfaces and obtaining information about surface morphology and smoothness. Energy-dispersive x-ray fluorescence and other surface-ionizing techniques can give information about surface chemistry. Microhardness instrumentation can be used to determine surface hardness, while gloss meters and reflectometry can provide measurements of gloss and whiteness. In this study, four sets of in vitro experiments were performed, which illustrate the value of three of these techniques. Specially formulated calcium-containing toothpastes (now as Arm and Hammer Age Defying toothpaste, Church and Dwight) designed to fill surface defects in tooth enamel, were evaluated in four experiments for their ability to effect cosmetic defects in etched tooth enamel: (1) two calcium-containing, sodium-bicarbonate-based toothpaste formulations were shown by SEM to smooth tooth enamel without introducing new scratches. In contrast, a commercial whitening toothpaste removed similar scratches but also created new ones; (2) calcium containing dentifrices were shown by SEM and hardness measurements to put mineral onto the surface of enamel and to harden it. The effects of uneven dispensing of the two-phase, bicarbonate-based calcium-containing formulation were shown to be small; (3) a number of different calcium-containing toothpastes were shown by SEM to deliver mineral onto the etched enamel surfaces, whereas a conventional fluoride toothpaste did not; and (4) AFM was used to follow the smoothing of an etched enamel surface after serial treatments with a calcium-containing, bicarbonate-based toothpaste. After 15 in vitro cycles, surface roughness was reduced by 50% and peak height was reduced by two thirds. The results illustrate the effectiveness of the three analytical techniques and show that the calcium-containing toothpastes can deposit mineral into enamel surface deformities under a wide variety of conditions and from a wide variety of formulas.

COMMENTARY

Recently, there has been excitement in the tooth remineralization research community as a result of the use of and effectiveness of soluble amorphous calcium phosphate (ACP) in remineralizing enamel when used as an additive to chewing gums, mints, toothpastes, and brush-on pastes. This calcium phosphate chemistry has been shown to remineralize acid-attacked and eroded enamel. Unlike fluoride alone, which becomes incorporated into the superficial surface of enamel and dentin without itself adding new mineral or changing the surface structures’ physical appearance, under the influence of fluoride ACP actually reverses the erosive effects of acid attack on enamel by replacing lost mineral.

These two studies used a variety of different qualitative methodologies to demonstrate the remineralization of enamel with the use of an ACP, bicarbonate-containing, fluoride toothpaste (Arm and Hammer® Age Defying toothpaste, Church and Dwight, Princeton, NJ). There was definitive proof of reversal of the acid demineralization with the use of a thorough assessment of surface roughness, gloss, and microhardness by remineralization through calcium phosphate deposition. This research parallels an important clinical study which compared a conventional fluoride toothpaste to an ACP-containing fluoride toothpaste for the prevention of caries in a radiation therapy population.¹ There is no doubt that this population is at highest risk of caries because of changes in the saliva-protective ability and a decrease in salivary flow. Radiation caries is insidious and very difficult to control. What this study demonstrated was that the remineralizing ability of a fluoride toothpaste containing ACP was significantly superior to the conventional fluoride toothpaste in preventing root caries in this at-highest-caries-risk population.

Dental professionals recommend fluoride-containing oral care products to all patients. Now, for those patients at highest risk (eg, patients with orthodontic brackets, patients with recession and at risk for root caries, patients with bulimia, gastroesophageal reflux disease, or those who ingest high quantities of acid-containing and enamel-eroding beverages and foods), we can recommend products delivering calcium and phosphate ions for routine use to prevent caries and remineralize and resurface existing acid-demineralized enamel.

References

1. Papas A, Russell D, Singh M, et al. Double blind clinical trial of a remineralizing dentifrice in the prevention of caries in a radiation therapy population. Gerodontology. 1999;16(1):2-10.

ABOUT THE AUTHOR

Howard E. Strassler, DMD Professor and Director of Operative Dentistry Department of Endodontics, Prosthodontics and Operative Dentistry University of Maryland Dental School, Baltimore,Maryland