Distribution of fluoride and calcium in plaque biofilms after the use of conventional and low-fluoride dentifrices

The influence of biofilm maturation on fluoride's anticaries efficacy

OBJECTIVES

(1) To explore the influence of biofilm maturation and timing of exposure on fluoride anticaries efficacy and (2) to explore biofilm recovery post-treatment.

METHODS

Bovine enamel specimens were utilized in a pH cycling model (28 subgroups [n = 18]). Each subgroup received different treatments [exposure]: sodium fluoride [NaF]; stannous fluoride [SnF₂]; amine fluoride [AmF]; and de-ionized water [DIW], at a specific period: early: days 1-4; middle: days 3-6; and late: days 7-10. During non-exposure periods, pH cycling included DIW instead of fluorides. Objective 1: part 1 (cycling for 4, 6, or 10 days). Part 2 (cycling for 10 days). Objective 2: early exposure: three sample collection time points (immediate, 3 days, and 6 days post-treatment); middle exposure: two sample collection time points (immediate, 4 days post-treatment). The enamel and biofilm were analyzed ([surface microhardness; mineral loss; lesion depth]; [lactate dehydrogenase enzyme activity; exopolysaccharide amount; viability]). Data were analyzed using ANOVA (p = 0.05).

RESULTS

Objective 1: Early exposure to fluorides produced protective effects against lesion progression in surface microhardness and mineral loss, but not for lesion depth. Objective 2: Early exposure slowed the demineralization process. SnF₂ and AmF were superior to NaF in reducing LDH and EPS values, regardless of exposure time. They also prevented biofilm recovery.

CONCLUSION

Earlier exposure to SnF₂ and AmF may result in less tolerant biofilm. Early fluoride treatment may produce a protective effect against demineralization. SnF₂ and AmF may be the choice to treat older biofilm and prevent biofilm recovery.

CLINICAL RELEVANCE

The study provides an understanding of biofilm-fluoride interaction with mature biofilm (e.g., hard-to-reach areas, orthodontic patients) and fluoride's sustainable effect hours/days after brushing.

Risk factors for dental caries in Latin American and Caribbean countries

Identifying the risk factors for dental caries is vital in epidemiology and clinical practices for developing effective preventive strategies, both, at the individual and collective levels. Different causality/determination models have been proposed to understand the development process of dental caries. In the present review, we designed a model inspired by the world-known social determinants models proposed in the 90s and more recently in the 10s, wherein the contextual factors are placed more externally and encompass the individual factors. The contextual factors included those related to the cultural and societal values, as well as the social and health government policies. The individual factors were classified into the following categories: socioeconomic (social class, occupation, income, and education level), demographic characteristics (age, sex, and ethnicity), behavioral factors (non-use of fluoride dentifrice, sugar consumption, poor oral hygiene, and lack of preventive dental care), and biological factors (recent caries experience/active caries lesions, biofilm retentive factors, developmental defects of the enamel, disabilities, saliva amount and quality, cariogenic biofilm). Each of these variables was addressed, while focusing on the current evidence from studies conducted in Latin American and Caribbean countries (LACC). Based on the proposed model, educational aspects were addressed, and individual caries risk assessment and management decisions were proposed; further, implications for public health policies and clinical practice were described. The identification of modifiable risk factors for dental caries should be the basis for multi-strategy actions that consider the diversity of Latin American communities.

The anti-caries efficacy of three fluoride compounds at increasing maturation of a microcosm biofilm

OBJECTIVE

To explore the anti-caries efficacy of three fluoride compounds at increasing maturation of a microcosm biofilm.

DESIGN

Microcosm biofilm, obtained from saliva collected from three donors (IRB #1406440799), was grown on enamel samples (n = 18/group) for 24-h (Brain Heart Infusion; 0.2 % sucrose). Then, pH cycling model started. Three maturations were explored (4d, 8d, and 12d). The pH cycling consisted of daily 2 × 5 min treatments (NaF, SnF₂, AmF: 287.5 ppm F, and de-ionized water [DIW]), 4 × 10 min remineralization (BHI, no sucrose, pH 7.0), and 3 × 2:15 h demineralization (BHI, 1% sucrose, pH 4.5). We analyzed the enamel (surface microhardness [VHN_change], integrated mineral loss [ΔZ], lesion depth [L]), and the biofilm (viability [log₁₀ CFU/mL], lactic acid production [LDH], and exopolysaccharide [EPS] amount). Data were analyzed using two-way ANOVA (p = 0.05).

RESULTS

The interaction between tested variables was significant for VHN_change, viability, LDH, EPS (p = 0.0354, p = 0.0001, p < 0.0001, p < 0.0001), but not for L (p = 0.2412) or ΔZ (p = 0.6811). LDH and EPS analyses exhibited more tolerance of mature biofilm against NaF (LDH and EPS p < 0.0001); NaF-treated groups demonstrated significantly lower results than the control in the 12d group. The effect of SnF₂ and AmF continued over time. VHN_change, L, and ΔZ: The effect of SnF₂ and AmF was higher than NaF and DIW. L and ΔZ did not result in significant differences over time (all treatments). Within each maturation, fluoride compounds demonstrated statistically significantly lower L and ΔZ values than DIW.

CONCLUSIONS

Biofilm's maturation may influence the selection of fluoride compounds to achieve an optimum cariostatic effect.

Intraoral fluoride levels after use of conventional and high-fluoride dentifrices

OBJECTIVES

This study aimed to evaluate saliva and plaque as indicators of intraoral fluoride (F) levels after the use of conventional and high-fluoride dentifrices.

MATERIALS AND METHODS

Subjects were randomly assigned to brush their teeth with conventional (1000 ppm F), high-fluoride (5000 ppm F), and placebo dentifrices (fluoride free) for 10 days, following a double-blind, crossover protocol. Saliva and plaque samples were collected on the morning of the 5(th) and 10th days, respectively at 1 and 12 h after brushing, and analyzed with an ion-selective electrode after HMDS-facilitated diffusion. Data were analyzed by two-way repeated measures ANOVA, Tukey's test and Spearman's correlation coefficient (p < 0.05).

RESULTS

Plaque and salivary F levels were significantly increased after the use of conventional and high-fluoride dentifrices when compared to values obtained for placebo, except plaque 12 h after the use of conventional dentifrice. A positive and significant correlation was found between fluoride concentrations in plaque and saliva for both times of sample collection.

CONCLUSION

Both indicators assessed were able to detect significant differences among treatments and between times after brushing. The use of a high-fluoride dentifrice is able to significantly increase intraoral fluoride levels throughout the day, being therefore a useful therapy for patients at high caries risk.

CLINICAL RELEVANCE

A dentifrice with high fluoride concentration could be regarded as a useful therapy of F delivery for high caries-risk patients, since intraoral F levels were sustained throughout most of the day after using this formulation.