Acid resistance of human enamel in vitro after bicarbonate application during remineralization

Evidence for biofilm acid neutralization by baking soda

BACKGROUND

The generating of acids from the microbial metabolism of dietary sugars and the subsequent decrease in biofilm pH below the pH at which tooth mineral begins to demineralize (critical pH) are the key elements of the dental caries process. Caries preventive strategies that rapidly neutralize biofilm acids can prevent demineralization and favor remineralization and may help prevent the development of sugar-induced dysbiosis that shifts the biofilm toward increased cariogenic potential. Although the neutralizing ability of sodium bicarbonate (baking soda) has been known for many years, its anticaries potential as an additive to fluoride dentifrice has received only limited investigation.

TYPES OF STUDIES REVIEWED

There is evidence that baking soda rapidly can reverse the biofilm pH decrease after a sugar challenge; however, the timing of when it is used in relation to a dietary sugar exposure is critical in that the sooner its used the greater the benefit in preventing a sustained biofilm pH decrease and subsequent demineralization. Furthermore, the effectiveness of baking soda in elevating biofilm pH appears to depend on concentration. Thus, the concentration of baking soda in marketed dentifrice products, which ranges from 10% to 65%, may affect their biofilm pH neutralizing performance. People with hyposalivation particularly may benefit from using fluoride dentifrice containing baking soda because of their diminished ability to clear dietary sugars and buffer biofilm acids.

CONCLUSIONS

Although promising, there is the need for more evidence that strategies that modify the oral ecology, such as baking soda, can alter the cariogenic (acidogenic and aciduric) properties of biofilm microorganisms.

PRACTICAL IMPLICATIONS

The acid neutralization of dental biofilm by using fluoride dentifrice that contains baking soda has potential for helping counteract modern high-sugar diets by rapidly neutralizing biofilm-generated acid, especially in people with hyposalivation.

Comparative study of the measurement of enamel demineralization and remineralization using transverse microradiography and electron probe microanalysis

Transverse microradiography (TMR) and electron probe microanalysis (EPMA) are commonly used for characterizing dental tissues. TMR utilizes an approximately monochromatic X-ray beam to determine the mass attenuation of the sample, which is converted to volume percent mineral (vol%min). An EPMA stimulates the emission of characteristic X-rays from a variable volume of sample (dependent on density) to provide compositional information. The aim of this study was to compare the assessment of sound, demineralized, and remineralized enamel using both techniques. Human enamel samples were demineralized and a part of each was subsequently remineralized. The same line profile through each demineralized lesion was analyzed using TMR and EPMA to determine vol%min and wt% elemental composition and atomic concentration ratio information, respectively. The vol%min and wt% values determined by each technique were significantly correlated but the absolute values were not similar. This was attributable to the complex ultrastructural composition, the variable density of the samples analyzed, and the nonlinear interaction of the EPMA-generated X-rays. EPMA remains an important technique for obtaining atomic ratio information, but its limitations in determining absolute mineral content indicate that it should not be used in place of TMR for determining the mineral density of dental hard tissues.

Sodium bicarbonate solution as an anti-erosive agent against simulated endogenous erosion

This study investigated whether sodium bicarbonate solution, applied on enamel previously exposed to a simulated intrinsic acid, can control dental erosion. Volunteers wore palatal devices containing enamel slabs, which were exposed twice daily extra-orally to hydrochloric acid (0.01 M, pH 2) for 2 min. Immediately afterwards, the palatal devices were re-inserted in the mouth and volunteers rinsed their oral cavity with a sodium bicarbonate solution or deionized water for 60 s. After the washout period, the palatal devices were refilled with a new set of specimens and participants were crossed over to receive the alternate rinse solution. The surface loss and surface microhardness (SMH) of specimens were assessed. The surface loss of eroded enamel rinsed with a sodium bicarbonate solution was significantly lower than the surface loss of eroded enamel rinsed with deionized water. There were no differences between treatments with sodium bicarbonate and deionized water for SMH measurements. Regardless of the solution used as an oral rinse, eroded enamel showed lower SMH than uneroded specimens. Rinsing with a sodium bicarbonate solution after simulated endogenous erosive challenge controlled enamel surface loss but did not alter the microhardness.

Acid resistance of the enamel in primary second molars from children with down syndrome and cerebral palsy

OBJECTIVES

This study was carried out to evaluate the extent of differences in mineralization of inner and outer enamel of the lower primary second molars of children with Down syndrome (DS) and Cerebral Palsy (CP) as revealed by acid treatment of exfoliated teeth. The results were compared to those obtained from a control group of healthy children.

METHODS

The sample included 4 mandibular second molars from each group. On each tooth, a thin section was cut, bisecting the mesial cusps. The analysis was carried out on the mesio-buccal cusps. Atomic force microscopy (AMF) was used to analyze the morphological structure of the dental enamel after 10 sec of 0.1 mol% citric acid treatment. The measurements were performed on 3 points in the enamel close to the outer surface and 3 points in the enamel close to the dentin. The differences between groups were analyzed using Mann Whitney tests.

RESULTS

In controls and CP teeth the outer enamel was more resistant to etching than the inner enamel. In DS teeth both outer and inner enamel showed similar results for all parameters. Between group comparisons showed that roughness values were significantly higher (P<0.01) in DS teeth than in either controls or CP teeth. No significant differences were found between CP and control teeth.

CONCLUSIONS

The higher values obtained for DS enamel reflect increased solubility of the enamel to acid relative to controls and CP teeth together with irregularity of the organic matrix. The practical importance of the results is that DS primary molars needs reduced etching time when prepared for pit and fissure sealants or composite/compomer restorations.