Enhancement of in-vivo remineralization of approximal initial caries in man by an organic and inorganic remineralization agent

Comparison of the remineralizing potential of child formula dentifrices

BACKGROUND

Although child formula fluoridated dentifrices can be used safely by young children their remineralizing capability remains questionable.

AIMS

To evaluate the remineralizing potential of child formula dentifrices on primary teeth.

DESIGN

In vitro single-section technique utilizing a 7 days pH-cycling model.

METHODS

Primary teeth were placed in demineralizing solution for 96 h to produce artificial carious lesions 100 μm deep, and then cut longitudinally into 50 sections 100-150 μm thick and randomly assigned to five groups. Sections in Groups A to D were treated with dentifrices containing 500 ppm AmF, 500 ppm MFP, 500 ppm MFP and xylitol, or 500 ppm NaF, respectively. Group E sections were treated with a nonfluoridated dentifrice.

OUTCOME MEASUREMENTS

Lesions were evaluated using polarized light microscopy and microradiography.

RESULTS

Group D (500 ppm NaF) sections exhibited a significant decrease in lesion depth, whereas those in Group E (nonF) showed a significant increase in depth (P<0.05, paired t-test). Decrease in lesion progression was observed in Groups A, B and C.

CONCLUSIONS

The 500 ppm NaF dentifrice demonstrated remineralization of carious lesions by virtue of a significant decrease in lesion depth; whereas dentifrices that contained AmF, MFP and MFP with xylitol decelerated the progression of demineralization.

Dentifrices, mouthwashes, and remineralization/caries arrestment strategies

While our knowledge of the dental caries process and its prevention has greatly advanced over the past fifty years, it is fair to state that the management of this disease at the level of the individual patient remains largely empirical. Recommendations for fluoride use by patients at different levels of caries risk are mainly based on the adage that more is better. There is a general understanding that the fluoride compound, concentration, frequency of use, duration of exposure, and method of delivery can influence fluoride efficacy. Two important factors are (1) the initial interaction of relatively high concentrations of fluoride with the tooth surface and plaque during application and (2) the retention of fluoride in oral fluids after application. Fluoride dentifrices remain the most widely used method of delivering topical fluoride. The efficacy of this approach in preventing dental caries is beyond dispute. However, the vast majority of currently marketed dentifrice products have not been clinically tested and have met only the minimal requirements of the FDA monograph using mainly laboratory testing and animal caries testing. Daily use of fluoride dental rinses as an adjunct to fluoride dentifrice has been shown to be clinically effective as has biweekly use of higher concentration fluoride rinses. The use of remineralizing agents (other than fluoride), directed at reversing or arresting non-cavitated lesions, remains a promising yet largely unproven strategy. High fluoride concentration compounds, e.g., AgF, Ag(NH3)2F, to arrest more advanced carious lesions with and without prior removal of carious tissue are being used in several countries as part of the Atraumatic Restorative Treatment (ART) approach. Most of the recent innovations in oral care products have been directed toward making cosmetic marketing claims. There continues to be a need for innovation and collaboration with other scientific disciplines to fully understand and prevent dental caries.

Nonsurgical treatment of incipient and hidden caries

Traditionally, dentists have been trained in the surgical model for caries management whereby detection is akin to diagnosis. This model unfortunately has been translated to patient expectations. Nevertheless, a growing body of clinical evidence suggests that noncavitated lesions, even those extending into dentin, can be managed by nonsurgical means with an expectation for remineralization.

The effect of biannual applications of amine fluoride solution on caries incidence in permanent first molars: a 5-year study

A randomized double-blind clinical trial was undertaken in a non-fluoridated community to assess the effectiveness of a minimal preventive intervention based on biannual applications of an amine fluoride (AmF) solution containing 1% fluoride. A total of 284 schoolchildren aged 6 years were recruited from a primary school in Milan, Italy, and randomly assigned to an experimental or a control group. The subjects of the experimental group received two applications each year of AmF to the permanent first molars and the control group subjects received similar applications of a placebo solution. Both in the experimental and control groups caries experience (DMFT) of the first molars was recorded every 6 months for 5 years. The mean DMFT scores in the experimental and control group were, respectively, 0.56 and 0.22 at the beginning and 1.14 and 1.75 at the end of the study. The preventive effect of the treatment became statistically significant only after 3 years. Survival analysis performed on the first molars that were sound at baseline showed that the topical AmF treatment caused, after 5 years, a significant reduction of caries incidence. This result confirms observations found in the international literature on the anticaries action of AmF. The administration rate used in this study seems to be useful for community preventive applications as it reduces the total amount of fluoride administered and the potential risks, and involves few personnel.

Hard-tissue substrates for evaluation of cariogenic and anti-cariogenic activity in situ

Hard-tissue substrates include primarily human and bovine enamel and human dentin. They have been used for in situ studies in a natural or sound condition, as well as flattened or containing an in vitro-formed caries-like lesion. Human enamel and dentin are generally the substrates of choice for studies of coronal and root-surface caries, respectively, but bovine enamel appears to offer a suitable alternative for many studies of enamel caries. Substrates with caries-like lesions will respond more rapidly to changes in the intra-oral mineral equilibrium and will allow both demineralization and remineralization to be determined. Findings from some studies suggest that caries-like lesions may respond somewhat differently, depending upon the degree of mineralization of the surface layer. Because in vitro findings with dentin show it to be significantly more soluble in acid than enamel, results from a study that used dentin may not be directly applicable to enamel. Both enamel and dentin substrates can be used in thin-section models. Hard-tissue substrates can also differ, depending upon their intra-oral location. Locations that result in the accumulation of plaque will behave differently from those that are plaque-free. So that plaque would accumulate, substrates have been placed approximally, beneath a fabric or steel mesh, in a protected trough, beneath a metal band or within a depression on the buccal surface. For studies requiring a determination of both demineralization and remineralization, human enamel or dentin containing a surface-softened caries-like lesion and covered with a uniform natural plaque are the substrates of choice.

Development of an intra-oral single-section remineralization model

An intra-oral model system has been developed which uses a single-section technique for before-and-after measurements on the same tissue. This model allows for placement of sections of enamel at both buccal and approximal sites. These sections may be sound or possess white-spot lesions. This allows for the evaluation of lesion initiation, lesion progression, and/or lesion remineralization. The sections are appropriate for measurement by polarized light microscopy, and, although not included in this study, they are also suitable for microradiographic evaluation. With ten human volunteers, the model system was evaluated by means of three rinse regimens in a cross-over design. The distilled water rinse showed the whole range of possible changes (e.g., demineralization, no change, and remineralization). More consistent remineralization was observed when a fluoride rinse or a remineralizing fluid was used. This model system should prove to be quite useful in evaluation of demineralization and remineralization phenomena in the oral environment.