Alkali production in the mouth and its relationship with certain patient's characteristics

Synbiotic-fluoride synergism on enamel remineralization, cytotoxicity and genotoxicity

OBJECTIVE(S)

The objectives of the present study were to examine the - a) enamel remineralization potential of synbiotic-fluoride (SF) therapy using a multi-species bacterial pH-cycling model; and b) cytotoxic and genotoxic effects of SF therapy extracts.

MATERIALS AND METHODS

The SF therapy group comprised of 2% arginine (Arg), 0.2% NaF, and a probiotic Lactobacillus rhamnosus GG (LRG). The intervention groups studied were: 1) No treatment; 2) 2% Arg; 3) 0.2% NaF; 4) LRG; 5) 2% Arg+0.2% NaF; 6) 2% Arg+LRG; 7) 0.2% NaF+LRG; and 8) 2% Arg+0.2% NaF+LRG (SF therapy). The enamel remineralization potential of SF therapy was investigated under cariogenic biofilm challenge; while the cytotoxicity and genotoxicity of SF therapy extracts were examined on HGF-1 and Chinese hamster fibroblast V79, respectively. To determine the remineralization effect, the specimens were subjected to mineral density (MD) assessment using micro-CT, Ca/P molar ratio with SEM-EDX, and enamel fluoride uptake (EFU) estimates. The HGF-1 proliferation assessment was quantified using MTT/CCK-8 assays with qualitative analysis by nuclei staining Hoechst-based fluorescence imaging. The genotoxicity was determined by micronuclei formation test.

RESULTS

Mineral gain and %remineralization derived from MD assessment for the SF therapy were significantly higher than the other groups (p<0.05). The %ΔCa/P for the SF and 2% Arg+0.2% NaF were significantly higher than the other groups (p<0.05). The SF and 2% Arg+0.2% NaF groups had the highest EFU compared to the other groups (p<0.05). No significant difference in the %viable HGF-1 cells were observed between the treatment interventions and no treatment group (p>0.05). Compared to the EMS-positive control, the micronuclei formation for all the intervention groups was significantly lower (p<0.05), with no significant difference among the treatment groups (p>0.05).

CONCLUSION

The SF therapy enhanced enamel remineralization with no biocompatibility concerns.

CLINICAL SIGNIFICANCE

With the enhanced enamel remineralization potential discerned in the present study, the SF therapy can be used as a promising caries-preventive agent targeted for high caries-risk individuals.

Micro-PAD card for measuring total ammonia nitrogen in saliva

This work presents a portable microfluidic paper-based analytical device (micro-PAD) card for the quantification of total ammonia nitrogen in human saliva. The amount of total ammonia nitrogen in saliva can be an indicator of the status of the oral microbiome with potential correlation to kidney health problems. The developed micro-PAD card comprises twenty units consisting of three stacked layers of circular discs: the sample layer, paper discs impregnated with sodium hydroxide solution, the PTFE membrane layer, and the detection layer, paper discs impregnated with bromothymol blue. The twenty units were aligned on transparent laminating pouches laminated to form the micro-PAD card (7.5 cm × 10.5 cm). Saliva samples can be directly dispensed onto the micro-PAD card and the detection was achieved by the BTB indicator color change, from yellow to blue, after conversion of ammonium into ammonia and diffusion of the ammonia gas through a hydrophobic layer. The determination of total ammonia nitrogen in saliva using the developed micro-PAD card intended to be very simple method and operated without the need of laboratory equipment. A quantification limit of 11.3 NH₄⁺mg L^-1 and linear application range from up to 150 NH₄⁺mg L^-1 were obtained making it suitable for the expected concentrations of total ammonia nitrogen in human saliva. It was successfully applied to saliva samples and its validation obtained by comparison against a potentiometric method. The card is stable for at least 1 month making it ideal as a portable device for point-of-care diagnosis. Graphical Abstract.

Cleansing effect of acidic L-arginine on human oral biofilm

Background

Dental plaque formed on tooth surfaces is a complex ecosystem composed of diverse oral bacteria and salivary components. Accumulation of dental plaque is a risk factor for dental caries and periodontal diseases. L-arginine has been reported to decrease the risk for dental caries by elevating plaque pH through the activity of arginine deiminase in oral bacteria. Here we evaluated the potential of L-arginine to remove established oral biofilms.

Methods

Biofilms were formed using human saliva mixed with Brain Heart Infusion broth supplemented with 1 % sucrose in multi-well plates or on plastic discs. After washing the biofilms with saline, citrate (10 mM, pH3.5), or L-arginine (0.5 M, pH3.5), the retained biofilms were analyzed by crystal violet staining, scanning electron microscopy, and Illumina-based 16S rDNA sequencing.

Results

Washing with acidic L-arginine detached oral biofilms more efficiently than saline and significantly reduced biofilm mass retained in multi-well plates or on plastic discs. Illumina-based microbiota analysis showed that citrate (pH3.5) preferentially washed out Streptococcus from mature oral biofilm, whereas acidic L-arginine prepared with 10 mM citrate buffer (pH3.5) non-specifically removed microbial components of the oral biofilm.

Conclusions

Acidic L-arginine prepared with citrate buffer (pH3.5) effectively destabilized and removed mature oral biofilms. The acidic L-arginine solution described here could be used as an additive that enhances the efficacy of mouth rinses used in oral hygiene.

Electronic supplementary material

The online version of this article (doi:10.1186/s12903-016-0194-z) contains supplementary material, which is available to authorized users.