Effect of fluoride gels with nano-sized sodium trimetaphosphate on the in vitro remineralization of caries lesions

Abstract Objective To evaluate the effects of fluoride (F) gels supplemented with micrometric or nano-sized sodium trimetaphosphate (TMPmicro and TMPnano, respectively) on the in vitro remineralization of caries-like lesions. Methodology Bovine enamel subsurface lesions (n=168) were selected according to their surface hardness (SH) and randomly divided into seven groups (n=24/group): Placebo (without F/TMP), 4,500 ppm F (4500F), 4500F + 2.5% TMPnano (2.5% Nano), 4500F + 5% TMPnano (5% Nano), 4500F + 5% TMPmicro (5% Micro), 9,000 ppm F (9000F), and 12,300 ppm F (Acid gel). The gels were applied in a thin layer for one minute. Half of the blocks were subjected to pH cycling for six days, whereas the remaining specimens were used for loosely- (calcium fluoride; CaF2) and firmly-bound (fluorapatite; FA) fluoride analysis. The percentage of surface hardness recovery (%SHR), area of subsurface lesion (ΔKHN), CaF2, FA, calcium (Ca), and phosphorus (P) on/in enamel were determined. Data (log10-transformed) were subjected to ANOVA and the Student-Newman-Keuls' test (p<0.05). Results We observed a dose-response relation between F concentrations in the gels without TMP for %SHR and ΔKHN. The 2.5% Nano and 5% Micro reached similar %SHR when compared with 9000F and Acid gels. For ΔKHN, Placebo and 5% Nano gels had the highest values, and 5% Micro, 2.5% Nano, 9000F, and Acid gels, the lowest. All groups had similar retained CaF2 values, except for Placebo and Acid gel. We verified observed an increase in Ca concentrations in nano-sized TMP groups. Regarding P, TMP groups showed similar formation and retention to 9000F and Acid. Conclusion Adding 2.5% nano-sized or 5% micrometric TMP to low-fluoride gels lead to enhanced in vitro remineralization of artificial caries lesions.

Erosive softening and erosive loss of enamel: hardness and profilometry analysis / Erosão e desgaste erosivo do esmalte: análises por microdureza e perfilometria

Objetivo: Esse trabalho tem como objetivo determinar e diferenciar a erosão e o desgaste erosivo do esmalte induzidos pelos ácidos cítrico e clorídrico. Materiais e Métodos: Quarenta amostras de esmalte foram divididas em 2 grupos: 1) 0,05 M de ácido cítrico (pH 2,5) simulando a erosão extrínseca e 2) 0,01 M de ácido clorídrico (pH 2,2) simulando a erosão intrínseca. Amostras de esmalte foram submetidas aos desafios erosivos. A microdureza de superfície (erosão) ou a perfilometria (desgaste erosivo) foi realizada após 30 s, depois a cada 60 s até 10 min, depois a cada 5 min até 30 min e depois de 60, 90 e 120 min. Resultados: A erosão (perda de dureza do esmalte) foi mensurável até 1 e 2 min de exposição aos ácidos clorídrico e cítrico, respectivamente. O desgaste erosivo aumentou significativamente ao longo do tempo para ambos os ácidos. Após 8 min, o ácido cítrico foi mais agressivo comparado ao clorídrico (p < 0,001). Conclusão: A progressão da erosão do esmalte do amolecimento ao desgaste erosivo é altamente dependente do tipo de ácido, sendo o ácido cítrico mais agressivo em estágios avançados. Portanto, este resultado deve ser considerado na escolha do método de análise para estudos laboratoriais.

Objective: This study aimed to determine and differentiate erosive softening and enamel erosive loss induced by citric and hydrochloric acids. Material and Methods: Forty enamel specimens were divided into 2 groups: 1) 0.05 M citric acid (pH 2.5) simulating extrinsic erosion and 2) 0.01 M hydrochloric acid (pH 2.2) simulating intrinsic erosion. The enamel specimens were submitted to erosive challenges. Surface microhardness (softening) or contact profilometry (loss) was done after 30 s, after each 60 s up to 10 min, after each 5 min up to 30 min and after 60, 90 and 120 min. Results: Erosive softening (enamel hardness loss) was measurable up to 1 and 2 min for hydrochloric and citric acids, respectively. Erosive loss was significantly increased over time for both types of acids. After 8 min, citric acid was more aggressive than hydrochloric acid (p < 0.001). Conclusion: The progression of enamel erosion from erosive softening to erosive loss is highly dependent on the type of acid, being citric acid more aggressive in later stages. Therefore, this finding should be considered when choosing the method of analysis for laboratory studies

Use of dentifrices to prevent erosive tooth wear: harmful or helpful?

Dental erosion is the loss of dental hard tissues caused by non-bacterial acids. Due to acid contact, the tooth surface becomes softened and more prone to abrasion from toothbrushing. Dentifrices containing different active agents may be helpful in allowing rehardening or in increasing surface resistance to further acidic or mechanical impacts. However, dentifrices are applied together with brushing and, depending on how and when toothbrushing is performed, as well as the type of dentifrice and toothbrush used, may increase wear. This review focuses on the potential harmful and helpful effects associated with the use of dentifrices with regard to erosive wear. While active ingredients like fluorides or agents with special anti-erosive properties were shown to offer some degree of protection against erosion and combined erosion/abrasion, the abrasive effects of dentifrices may increase the surface loss of eroded teeth. However, most evidence to date comes from in vitro and in situ studies, so clinical trials are necessary for a better understanding of the complex interaction of active ingredients and abrasives and their effects on erosive tooth wear.

Insights into preventive measures for dental erosion: [review]

Dental erosion is defined as the loss of tooth substance by acid exposure not involving bacteria. The etiology of erosion is related to different behavioral, biological and chemical factors. Based on an overview of the current literature, this paper presents a summary of the preventive strategies relevant for patients suffering from dental erosion. Behavioral factors, such as special drinking habits, unhealthy lifestyle factors or occupational acid exposure, might modify the extent of dental erosion. Thus, preventive strategies have to include measures to reduce the frequency and duration of acid exposure as well as adequate oral hygiene measures, as it is known that eroded surfaces are more susceptible to abrasion. Biological factors, such as saliva or acquired pellicle, act protectively against erosive demineralization. Therefore, the production of saliva should be enhanced, especially in patients with hyposalivation or xerostomia. With regard to chemical factors, the modification of acidic solutions with ions, especially calcium, was shown to reduce the demineralization, but the efficacy depends on the other chemical factors, such as the type of acid. To enhance the remineralization of eroded surfaces and to prevent further progression of dental wear, high-concentrated fluoride applications are recommended. Currently, little information is available about the efficacy of other preventive strategies, such as calcium and laser application, as well as the use of matrix metalloproteinase inhibitors. Further studies considering these factors are required. In conclusion, preventive strategies for patients suffering from erosion are mainly obtained from in vitro and in situ studies and include dietary counseling, stimulation of salivary flow, optimization of fluoride regimens, modification of erosive beverages and adequate oral hygiene measures.