Novel Anticaries and Remineralization Agents: Future Research Needs

Chitosan nanoparticles loaded with epigallocatechin-3-gallate: synthesis, characterisation, and effects against Streptococcus mutans biofilmEpigallocatechin-loaded chitosan nanoparticles: effects against Streptococcus mutans biofilm

This study evaluated the effects of chitosan nanoparticles loaded with epigallocatechin-3-gallate (EGCG) against Streptococcus mutans biofilm. EGCG-loaded chitosan (Nchi + EGCG) nanoparticles and Chitosan (Nchi) nanoparticles were prepared by ion gelation process and characterised regarding particle size, polydispersion index, zeta potential, and accelerated stability. S mutans biofilms were treated twice daily with NaCl 0.9% (negative control), Nchi, Nchi + EGCG, and chlorhexidine (CHX) 0.12% (positive control). After 67 h, the biofilms were evaluated for acidogenesis, bacterial viability and dry weight. Biofilm morphology and structure were analysed by scanning electron microscopy. The nanoformulations presented medium to short-term stability, size of 500 nm, and polydispersion index around 0.400. Treatments affected cell morphology and biofilm structure. However, no effects on microbial viability, biofilm dry weight, and acidogenesis were observed. Thus, the nanoformulations disassembled the biofilm matrix without affecting microbial viability, which makes them promising candidates for the development of dental caries preventive and therapeutic agents.

Effect of fluoride varnishes on oral bacteria of preschool children with cavitated and non-cavitated carious lesions: randomized clinical trial

We compare the effect of calcium and phosphate-containing sodium fluoride (NaF) varnishes to conventional NaF varnish on S. mutans and L. fermentum counts. 3-4 years old children were grouped according to their caries status (n = 45 each): caries-free, with non-cavitated and with cavitated lesions. Each group was randomly subdivided (n = 15 each) into: Group 1- 5% NaF, Group 2- 5% NaF with tricalcium phosphate, Group 3- 5% NaF with casein phosphopeptide- amorphous calcium phosphate. Biofilm and saliva were collected to quantify microorganisms at baseline (T1) and 24-months (T2). Differences between groups were compared using Kruskal-Wallis test, followed by Dunn-Bonferroni post-test, at 0.0167 α-level. Significant difference was found for percentage of children with detectable biofilm L. fermentum (p = 0.013) at T1 and salivary S. mutans (p = 0.011) at T2. Percentage of children increased from T1 to T2 in Group 2 with salivary S. mutans (p = 0.007), salivary L. fermentum (p = 0.035), and biofilm L. fermentum (p = 0.019) and in Group 3 with salivary L. fermentum (p = 0.035). Bacterial change was not significant in both samples of intervention groups, except increase in salivary S. mutans (p = 0.038) in Group 3. Both calcium- and phosphate-containing NaF varnishes demonstrated similar antibacterial effect on S. mutans and L. fermentum compared to conventional NaF varnish.

Anticariogenic Activity of Celastrol and Its Enhancement of Streptococcal Antagonism in Multispecies Biofilm

Dental caries is a chronic disease resulting from dysbiosis in the oral microbiome. Antagonism of commensal Streptococcus sanguinis and Streptococcus gordonii against cariogenic Streptococcus mutans is pivotal to keep the microecological balance. However, concerns are growing on antimicrobial agents in anticaries therapy, for broad spectrum antimicrobials may have a profound impact on the oral microbial community, especially on commensals. Here, we report celastrol, extracted from Traditional Chinese Medicine's Tripterygium wilfordii (TW) plant, as a promising anticaries candidate. Our results revealed that celastrol showed antibacterial and antibiofilm activity against cariogenic bacteria S. mutans while exhibiting low cytotoxicity. By using a multispecies biofilm formed by S. mutans UA159, S. sanguinis SK36, and S. gordonii DL1, we observed that even at relatively low concentrations, celastrol reduced S. mutans proportion and thereby inhibited lactic acid production as well as water-insoluble glucan formation. We found that celastrol thwarted S. mutans outgrowth through the activation of pyruvate oxidase (SpxB) and H2O2-dependent antagonism between commensal oral streptococci and S. mutans. Our data reveal new anticaries properties of celastrol that enhance oral streptococcal antagonism, which thwarts S. mutans outgrowth, indicating its potential to maintain oral microbial balance for prospective anticaries therapy.

Effect of titanium dioxide on Streptococcus mutans biofilm

BACKGROUND

Streptococcus mutans (S. mutans) participates in the dental caries process. Titanium dioxide (TiO₂) nanoparticles produce reactive oxygen species capable of disrupting bacterial DNA synthesis by creating pores in cell walls and membranes.

OBJECTIVE

The objective of this study was to determine the effect of TiO₂ on the disruption of S. mutans biofilm.

METHODS

This study was conducted in four phases involving a TiO₂-containing toothbrush and TiO₂ nanoparticles. Each phase was completed using 24 h established S. mutans biofilm growth. Phase one data was collected through a bacterial plating study, assessing biofilm viability. Biofilm mass was evaluated in phase two of the study by measuring S. mutans biofilm grown on microtiter plates following crystal violet staining. The third phase of the study involved a generalized oxygen radical assay to determine the relative amount of oxygen radicals released intracellularly. Phase four of the study included the measurement of insoluble glucan/extracellular polysaccharide (EPS) synthesis using a phenol-sulfuric acid assay.

RESULTS

Both exposure time and time intervals had a significant effect on bacterial viability counts (p = 0.0323 and p = 0.0014, respectively). Bacterial counts after 6 min of exposure were significantly lower than after 2 min (p = 0.034), compared to the no treatment control (p = 0.0056). As exposure time increased, the amount of remaining biofilm mass was statistically lower than the no treatment control. Exposure time had a significant effect on oxygen radical production. Both the 30 and 100 nm TiO₂ nanoparticles had a significant effect on bacterial mass. The silver nanoparticles and the 30 and 100 nm TiO₂ nanoparticles significantly inhibited EPS production.

CONCLUSION

The TiO₂-containing toothbrush kills, disrupts, and produces oxygen radicals that disrupt established S. mutans biofilm. TiO₂ and silver nanoparticles inhibit EPS production and reduce biofilm mass. The addition of TiO₂ to dental products may be effective in reducing cariogenic dental biofilm.

Evaluation of the effect of remineralization with strontium-doped nanohydroxyapatite with noncollagenous protein analog: Chitosan on the shear bond strength of resin composite to dentin - An in vitro study

Context

The resin-dentin interface is less durable, which reduces the longevity of tooth-colored restorations. To encounter this shortcoming, the use of nanotechnology to mimic biomineralization proves beneficial.

Aims

This study was conducted to evaluate the effect of remineralization with strontium-doped nanohydroxyapatite (Sr-nHAp) with chitosan on shear bond strength of resin composite to dentin.

Materials and Methods

Sixty five extracted human premolars were divided into five groups (n = 13) based on remineralization protocol as: Group A - 20% (Sr-nHAp) with chitosan, Group B - 10% (Sr-nHAp) with chitosan, Group C - 20% (Sr-nHAp) with simulated body fluid, Group D - 10% (Sr-nHAp) with simulated body fluid, and Group E - control. Following bonding, resin composite of specified dimension was built and was subjected to shear bond strength test after 24 h and 1 week using Universal Testing Machine, and mode of failure was assessed. ANOVA and paired sample t-test were used for analyzing the data, and the level of significance was set at 5%.

Results

The highest value of shear bond strength was obtained from Group A after aging for a week, and there is a significant increase in the value of all the groups as compared to the control group after 1 week of storage than 24 h.

Conclusions

Remineralization with Sr-nHAp and chitosan has positively improved the bond strength of resin to dentin at the end of 1 week.

Effects of the green tea catechin epigallocatechin-3-gallate on Streptococcus mutans planktonic cultures and biofilms: systematic literature review of in vitro studies

This study aimed at performing a systematic review of the literature on the effects of epigallocatechin-3-gallate (EGCG) on Streptococcus mutans planktonic cultures and biofilms. The selected references demonstrated that EGCG suppresses S. mutans acid production by inhibiting the activity of enzymes such as lactate dehydrogenase and FIF0-ATPase. Regarding virulence factors, one study reported a reduction in soluble and insoluble polysaccharide synthesis, another demonstrated that EGCG inhibited GTase activity, and another showed effects of EGCG on the expression of gtf B, C, and D. The effects of EGCG on S. mutans biofilms were reported only by 2 of the selected studies. Moreover, high variability in effective concentrations and microbial assessment methods were observed. The literature suggests that EGCG has effects against S. mutans planktonic cells viability and virulence factors. However, the literature lacks studies with appropriate biofilm models to evaluate the precise effectiveness of EGCG against S. mutans biofilms.

Tannic acid induces dentin biomineralization by crosslinking and surface modification

It is currently known that crosslinking agents can effectively improve the mechanical properties of dentin by crosslinking type I collagen. However, few scholars have focused on the influence of crosslinking agents on the collagen-mineral interface after crosslinking. Analysis of the Fourier transform infrared spectroscopy (FTIR) results showed that hydrogen bonding occurs between the tannic acid (TA) molecule and the collagen. The crosslinking degree of TA to collagen reached a maximum 41.28 ± 1.52. This study used TA crosslinked collagen fibers to successfully induce dentin biomineralization, and the complete remineralization was achieved within 4 days. The crosslinking effect of TA can improve the mechanical properties and anti-enzyme properties of dentin. The elastic modulus (mean and standard deviation) and hardness values of the remineralized dentin pretreated with TA reached 19.1 ± 1.12 GPa and 0.68 ± 0.06 GPa, respectively, which were close to those of healthy dentin measurements, but significantly higher than those of dentin without crosslinking (8.91 ± 1.82 GPa and 0.16 ± 0.01 GPa). The interface energy between the surface of collagen fibers and minerals decreased from 10.59 mJ m^-2 to 4.19 mJ m^-2 with the influence of TA. The current work reveals the importance of tannic acid crosslinking for dentin remineralization while providing profound insights into the interfacial control of biomolecules in collagen mineralization.

Effects of Fluoride and Calcium Phosphate-Based Varnishes in Children at High Risk of Tooth Decay: A Randomized Clinical Trial

BACKGROUND

The aim of this study was to investigate the effect of the application of two varnishes-MI Varnish (5% sodium fluoride with CPP-ACP) and Clinpro White Varnish (5% sodium fluoride with fTCP)-applied every three months in children with high caries risk for 12 months on plaque indexes, salivary pH, salivary lactic acid and chemical elements concentrations.

METHODS

We included 58 children aged 4-12 years, assigned to control (placebo), Clinpro and MI groups. Baseline and three-month saliva samples were taken. We assessed changes in pH, lactic acid concentrations and chemical elements in saliva.

RESULTS

At 12 months, all groups showed a nonsignificant increase in pH levels and a reduction in lactic acid, which was greatest in the placebo group. There was a significant reduction in ²⁴Mg (p = <0.001), ³¹P (p = 0.033) and ⁶⁶Zn (p = 0.005) levels in the placebo group (p ≤ 0.05), but not in the other elements studied: ²³Na, ²⁷Al, ³⁹K, ⁴⁴Ca, ⁵²Cr, ⁵⁵Mn, ⁵⁷Fe, ⁵⁹Co, ⁶³Cu, ⁷⁵As, ¹¹¹Cd, ¹³⁷Ba, ²⁰⁸Pb and ¹⁹F.

CONCLUSIONS

Neither pH, lactic acid concentrations or most salivary chemical elements were useful in defining patients at high risk of caries or in monitoring the effect of MI Varnish and Clinpro White Varnish after three-month application for 12 months. However, the appearance of new cavities was stopped, and the hygiene index improved, probably due to hygienic and dietary measures and the use of fluoridated toothpaste.

TRIAL REGISTRATION

ISRCTN registry, ISRCTN13681286.

A Comparison of Four Caries Risk Assessment Methods

Introduction: Caries risk assessment (CRA) is essential as the basis for successful management of dental caries. Of the many published CRA tools, four well-known ones are CAMBRA, Cariogram, American Dental Association (ADA), and American Academy of Pediatric Dentistry (AAPD) CRAs. The predictive accuracy of CAMBRA and Cariogram CRA tools have been examined in clinical outcomes studies in thousands of patients and the tools are widely used all over the world. The purpose of the present paper is three-fold, namely (1) to briefly review, compare and contrast these four CRA methods, (2) to provide a concise method for CRA introducing a quantitative component to the CAMBRA forms (CAMBRA 123), and (3) to guide the choice of CRA methods that will support caries management decisions. Comparison of Caries Risk Assessment Methods: In the present evaluation, the above-mentioned four CRA methods for ages 0-6 years and 6 years-adult were compared using 26 hypothetical patients (13 per age group). Comparison results show that Cariogram and CAMBRA categorized patients into identical risk categories. Each of the ADA and AAPD tools gave different results than CAMBRA and Cariogram in several comparison examples. CAMBRA 123 gave the same caries risk level results as the Cariogram and the CAMBRA methods for all hypothetical patients for both age groups. Conclusions: Both the Cariogram and the CAMBRA CRA methods are equally useful for identifying the future risk of dental caries. CAMBRA 123 shows promise as an easy-to-use quantitative method for CRA in clinical practice. The health care providers will be the ones to decide which CRA method will allow them to establish individualized, successful caries management therapies and how to combine these for the best care of their patients.

Chemical and morphological changes of femtosecond laser-irradiated enamel using subablative parameters

Chemical composition of dental enamel has a great relationship with the prevention of caries. The objective of the present work was to evaluate the chemical and morphological changes of femtosecond laser-irradiated enamel with subablative parameters using Raman spectroscopy, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM). Bovine incisor teeth were used to obtain 30 enamel specimens (5 × 5 mm² ). The chemical composition of the control sample was analyzed by Raman spectrometry to acquire the absorption spectrum, delimiting the areas under the carbonate and phosphate bands. This analysis was used to evaluate the change in the chemical composition of the sample after irradiation. The specimens were irradiated (IRR) with a Ti:Sapphire laser system (pulsed and focused modes, femtosecond regime 70 fs, average power of 1 W and exposure time of 15 s). After irradiation, the areas under the carbonate and phosphate absorption bands were delimited in each specimen. Raman spectrometry data were analyzed using Student's t-test (α = 5%). By comparing the spectra of the IRR and non-irradiated (NI) specimens, the results showed a significant increase in the area value for the phosphate peaks and a significant reduction in the area value for the carbonate peak and the carbonate:phosphate ratio. CLSM and SEM analyses did not reveal structural alterations in the subsurface nor morphological alterations in the IRR enamel surface, respectively. It was concluded that femtosecond laser irradiation using subablative parameters reduced the carbonate content and the carbonate/phosphate ratio without altering the structure and morphology of the dental enamel.

The effect of silver diamine fluoride in preventing in vitro primary coronal caries under pH-cycling conditions

OBJECTIVES

This study investigated the ability of SDF, and its individual components, silver (Ag⁺) and fluoride (F^-) ions, in preventing enamel demineralization under pH-cycling conditions in the presence or absence of twice-daily fluoride application.

DESIGN

Polished human enamel specimens were assigned to five treatment groups (n = 36 per group): SDF (38 %); SDF followed by application of a saturated solution of potassium iodide (SDF + KI); silver nitrate (AgNO₃; silver control, 253,900 ppm Ag); potassium fluoride (KF; fluoride control, 44,800 ppm F); deionized water. Treatments were applied once. Specimens in each treatment group were divided into two subgroups (n = 18). During the subsequent 7-day pH-cycling phase, specimens were treated twice daily with either 275 ppm fluoride as sodium fluoride or deionized water, immediately before and after a 3-h cariogenic challenge with exposure to artificial saliva at all other times. Changes in color, Vickers surface microhardness (SMH), transverse microradiography (TMR) was calculated. Data were analyzed using two-way ANOVA.

RESULTS

In both models, SDF, SDF + KI and KF were superior in inhibiting demineralization compared to AgNO₃ and deionized water (p < 0.0001). There was no statistically significant difference between SDF, SDF + KI and KF with twice daily fluoride treatments (p > 0.8). However, KF was more effective in preventing demineralization than SDF and SDF + KI in the absence of fluoride treatments (p = 0.0002). KI did not affect the ability of SDF to prevent demineralization (p > 0.4).

CONCLUSION

SDF and SDF + KI appears to be an effective option in preventing primary coronal caries.

A Century of Change towards Prevention and Minimal Intervention in Cariology

Better understanding of dental caries and other oral conditions has guided new strategies to prevent disease and manage its consequences at individual and public health levels. This article discusses advances in prevention and minimal intervention dentistry over the last century by focusing on some milestones within scientific, clinical, and public health arenas, mainly in cariology but also beyond, highlighting current understanding and evidence with future prospects. Dentistry was initially established as a surgical specialty. Dental caries (similar to periodontitis) was considered to be an infectious disease 100 years ago. Its ubiquitous presence and rampant nature-coupled with limited diagnostic tools and therapeutic treatment options-meant that these dental diseases were managed mainly by excising affected tissue. The understanding of the diseases and a change in their prevalence, extent, and severity, with evolutions in operative techniques, technologies, and materials, have enabled a shift from surgical to preventive and minimal intervention dentistry approaches. Future challenges to embrace include continuing the dental profession's move toward a more patient-centered, evidence-based, less invasive management of these diseases, focused on promoting and maintaining oral health in partnership with patients. In parallel, public health needs to continue to, for example, tackle social inequalities in dental health, develop better preventive and management options for existing disease risk groups (e.g., the growing aging population), and the development of reimbursement and health outcome models that facilitate implementation of these evolving strategies. A century ago, almost every treatment involved injections, a drill or scalpel, or a pair of forceps. Today, dentists have more options than ever before available to them. These are supported by evidence, have a minimal intervention focus, and result in better outcomes for patients. The profession's greatest challenge is moving this evidence into practice.

Towards AR-assisted visualisation and guidance for imaging of dental decay

Untreated dental decay is the most prevalent dental problem in the world, affecting up to 2.4 billion people and leading to a significant economic and social burden. Early detection can greatly mitigate irreversible effects of dental decay, avoiding the need for expensive restorative treatment that forever disrupts the enamel protective layer of teeth. However, two key challenges exist that make early decay management difficult: unreliable detection and lack of quantitative monitoring during treatment. New optically based imaging through the enamel provides the dentist a safe means to detect, locate, and monitor the healing process. This work explores the use of an augmented reality (AR) headset to improve the workflow of early decay therapy and monitoring. The proposed workflow includes two novel AR-enabled features: (i) in situ visualisation of pre-operative optically based dental images and (ii) augmented guidance for repetitive imaging during therapy monitoring. The workflow is designed to minimise distraction, mitigate hand-eye coordination problems, and help guide monitoring of early decay during therapy in both clinical and mobile environments. The results from quantitative evaluations as well as a formative qualitative user study uncover the potentials of the proposed system and indicate that AR can serve as a promising tool in tooth decay management.

Mineral deposition promoted by resin-based sealants with different calcium phosphate additions

The aim of this study was to evaluate the influence of different calcium phosphates (CaPs) on the physical, biological, and remineralizing properties of experimental resin-based sealants (RBSs). Triethylene-glycol dimethacrylate (90wt%) and bisphenol A-glycidyl methacrylate (10wt%) were used to produce resin-based sealants. Hydroxyapatite (SHAp), α-tricalcium phosphate (Sα-TCP) and octacalcium phosphate (SOCP) were added to the sealants in a 10wt% concentration. One group without CaPs was used as the control group (SCG). The degree of conversion (DC) was assessed with Fourier-transformed infrared spectroscopy, whereas cytotoxicity was tested with the HaCaT keratinocyte cell line. The ultimate tensile strength (UTS) was used to assess the mechanical strength of the experimental RBSs. Sealed enamel was used for colorimetric assay. Mineral deposition was assessed with Raman spectroscopy after 7, 14, and 28 days of sample immersion in artificial saliva. Scanning electron microscopy was used to analyze the surface morphology after 28 days of immersion. The addition of 10wt% of fillers significantly reduced the DC of sealants. SOCP groups showed reduced cell viability. Higher UTS was found for Sα-TCP and SHAp. The color analysis showed that SGC and demineralized teeth presented higher mismatches with the sound tissue. Mineral deposition was observed for SHAp and Sα-TCP after 7 days, with increased phosphate content and mineral deposits for SHAp after 28 days. RBS with the addition of 10% HAp promoted increased mineralization in vitro after 28 days, and did not affect cell viability, DC, mechanical properties, or RBS color in the enamel.

Boron Nitride Nanotubes as Filler for Resin-Based Dental Sealants

The aim of this study was to evaluate the influence of boron-nitride nanotubes (BNNTs) on the properties of resin-based light-curing dental sealants (RBSs) when incorporated at different concentration. RBSs were formulated using methacrylate monomers (90 wt.% TEGDMA, 10 wt.% Bis-GMA). BNNTs were added to the resin blend at 0.1 wt.% and 0.2 wt.%. A Control group without filler was also designed. Degree of conversion, ultimate tensile strength, contact angle, surface free energy, surface roughness and color of the RBSs were evaluated for the tested materials. Their cytotoxicity and mineral deposition ability (Bioactivity) were also assessed. A suitable degree of conversion, no effect in mechanical properties and no cytotoxic effect was observed for the experimental materials. Moreover, the surface free energy and the surface roughness decreased with the addition of BNNTs. While the color analysis showed no difference between specimens containing BNNTs and the control group. Mineral deposition occurred in all specimens containing BNNTs after 7d. In conclusion, the incorporation of BNNTs may provide bioactivity to resin-based dental sealants and reduce their surface free energy.

A novel fluorescent adhesive-assisted biomimetic mineralization

We propose a novel fluorescent adhesive-assisted biomimetic mineralization strategy, based on which 1 wt% of sodium fluorescein and 25 wt% of polyacrylic acid stabilized amorphous calcium phosphate (PAA-ACP) nanoparticles were incorporated into a mild self-etch adhesive (Clearfil S3 Bond) as a fluorescent mineralizing adhesive. The characterization of the PAA-ACP nanoparticles indicates that they were spherical particles clustered together, each particle with a diameter of approximately 20-50 nm, in a metastable phase with two characteristic absorption peaks (1050 cm-1 and 580 cm-1). Our results suggest that the fluorescent mineralizing adhesive was non-cytotoxic with minimal esthetic interference and its fluorescence intensity did not significantly decrease within 6 months. Our data reveal that the fluorescent mineralizing adhesive could induce the extra- and intra-fibrillar remineralization of the reconstituted type I collagen, the demineralized enamel and dentin substrate. Our data demonstrate that a novel fluorescent adhesive-assisted biomimetic mineralization strategy will pave the way to design and produce anti-carious materials for the prevention of dental caries.