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.

Comparison of In Vitro Biofilm Formation on Titanium and Zirconia Implants

Background

Peri-implant diseases are emerging issues in contemporary implant dentistry. As biofilms play a critical role in peri-implant diseases, the characteristic of resisting bacterial adhesion would be ideal for dental implants. The aims of the study were to compare titanium (Ti) and zirconia (Zr) implants regarding the amount of biofilm formation at different time frames and assess the distribution of biofilm on different aspects of dental implants.

Methods

Biofilm was developed on Ti and Zr dental implants with a peri-implant-related multispecies model with Streptococcus oralis, Actinomyces naeslundii, Veillonella dispar, and Porphyromonas gingivalis, for 3 and 14 days. Quantitative assessment was performed with the measurement of total bacterial viability (colony forming units, CFU/mg). Scanning electron microscopy (SEM) was used to evaluate biofilm formation on different aspects of the implants.

Results

Three-day-old biofilm on Ti implants was significantly higher than that on Zr implants (p < 0.001). The Ti and Zr groups were not significantly different for 14-day-old biofilm. SEM images demonstrated that 3-day-old biofilm on Zr implants was sparse while biofilm growth was more pronounced for 3-day-old biofilm on Ti implants and 14-day-old biofilm groups. It appeared that less biofilm formed on the valley compared to the thread top for 3-day-old biofilm on Zr implants. Differences between the valley and the thread top became indistinguishable with the development of mature biofilm.

Conclusion

While early formed biofilms show greater accumulation on Ti implants compared to Zr implants, older biofilms between the two groups are comparable. The distribution of biofilms was not uniform on different areas of implant threads during early biofilm development.

Effects of artificial honey and epigallocatechin-3-gallate on streptococcus pyogenes

Background

Streptococcus pyogenes is an important global human pathogen that causes pharyngitis, and antibacterial therapy has become an important part of the overall therapy for pharyngitis. As natural derivatives, honey and green tea are often recommended for patients with pharyngitis in traditional Chinese medicine without experimental theoretical basis on wether the combined effect of honey and green tea on pharyngitis is better than they alone. The aims of this study were to explore the effects of artificial honey (AH) and epigallocatechin-3-gallate (EGCG) on S. pyogenes and elucidate the possible mechanisms, which were investigated using MIC (the minimum inhibitory concentration), FIC (fractional inhibitory concentration) index, growth pattern, biofilm formation and RT-qPCR.

Results

The MIC of AH on S. pyogenes was 12.5% (v/v) and the MIC of EGCG was 1250 μg/ml. The FIC index of AH and EGCG was 0.5. The planktonic cell growth, growth pattern and biofilm formation assays showed that AH and EGCG mixture had stronger inhibitory effect on S. pyogenes than they alone. RT-qPCR confirmed that the expression of hasA and luxS gene were inhibited by AH and EGCG mixture.

Conclusions

AH and EGCG mixture can inhibit the planktonic cell growth, biofilm formation and some virulence genes expression of S. pyogenes, better than they alone. The combination of honey and green tea have the potential to treat pharyngitis as natural derivatives, avoiding drug resistance and double infection.

Evaluating hop extract concentrations found in commercial beer to inhibit Streptococcus mutans biofilm formation

AIMS

The purpose of this study was to compare the effect of hop extracts with diverse β-acid concentrations on Streptococcus mutans biofilm formation.

METHODS AND RESULTS

Ten different hop extracts, with α-acid concentrations similar to those found in commercial beer products and β-acid concentrations ranging from 2.6 to 8.1%, were added to distilled water to make standardized concentrations. S. mutans isolates were treated with hop extract dilutions varying from 1:2 to 1:256. The minimum inhibitory, minimum bactericidal, and minimum biofilm inhibitory concentrations were determined and the optical density was evaluated. Live/dead staining confirmed the bactericidal effects. Biofilm formation of several strains of S. mutans was significantly inhibited by hop extract dilutions of 1:2, 1:4, 1:8, 1:16, and 1:32. Strong negative correlations were observed between α- and β-acid concentrations of the hop extracts and S. mutans total growth and biofilm formation.

CONCLUSIONS

The use of hop extracts prepared similarly to commercial beer decreased S. mutans biofilm formation.

SIGNIFICANCE AND IMPACT OF THE STUDY

The inclusion of hops in the commercial beer products may provide beneficial health effects. Further studies are warranted to determine an effect in vivo on the development of dental caries.

Analyses of the Effects of Arginine, Nicotine, Serotype and Collagen-Binding Proteins on Biofilm Development by 33 Strains of Streptococcus mutans

Streptococcus mutans serotype k strains comprise <3% of oral isolates of S. mutans but are prominent in diseased cardiovascular (CV) tissue. Collagen binding protein (CBP) genes, cbm and cnm, are prevalent in serotype k strains and are associated with endothelial cell invasion. Nicotine increases biofilm formation by serotype c strains of S. mutans, but its effects on serotype k strains and strains with CBP are unknown. Saliva contains arginine which alters certain properties of the extracellular polysaccharides (EPS) in S. mutans biofilm. We examined whether nicotine and arginine affect sucrose-induced biofilm of S. mutans serotypes k (n = 23) and c (n = 10) strains with and without CBP genes. Biofilm mass, metabolism, bacterial proliferation, and EPS production were assessed. Nicotine increased biomass and metabolic activity (p < 0.0001); arginine alone had no effect. The presence of a CBP gene (either cbm or cnm) had a significant effect on biofilm production, but serotype did not. Nicotine increased bacterial proliferation and the effect was greater in CBP + strains compared to strains lacking CBP genes. Addition of arginine with nicotine decreased both bacterial mass and EPS compared to biofilm grown in nicotine alone. EPS production was greater in cnm + than cbm + strains (p < 0.0001). Given the findings of S. mutans in diseased CV tissue, a nicotine induced increase in biofilm production by CBP + strains may be a key link between tobacco use and CV diseases.

Effect of a Tea Polyphenol on Different Levels of Exposure of Nicotine and Tobacco Extract on Streptococcus mutans Biofilm Formation

Objective: The purpose of this study was to compare the effects of different levels of nicotine and tobacco extract exposure on Streptococcus mutans biofilm formation and the inhibitory effect of the polyphenol epigallocatechin-3 gallate (EGCG) found in green tea. This study addressed the results of biofilm assays with EGCG and varying relative concentrations of nicotine and tobacco extract consistent with primary, secondary and tertiary levels of smoking exposure. Primary smoking exposure to nicotine has been demonstrated to significantly increase biofilm formation, while EGCG has been demonstrated to reduce S. mutans biofilm formation.

Methods:S. mutans was treated with varying levels of nicotine or cigarette smoke condensate (CSC) concentrations (0–32 mg/ml and 0–2 mg/ml, respectively) in Tryptic Soy broth supplemented with 1% sucrose for different lengths of time simulating primary, secondary and tertiary smoking exposure with and without 0.25 mg/ml EGCG. The amount of total growth and biofilm formed was determined using a spectrophotometric crystal violet dye staining assay.

Results: For both nicotine and CSC, primary exposure displayed overall significantly less growth compared to secondary exposure. For nicotine, secondary exposure demonstrated significantly greater growth than tertiary exposure levels. Overall, significantly greater total bacterial growth and biofilm formation in the presence of nicotine and CSC was observed in the absence of EGCG than in the presence of EGCG. However, biofilm growth was not significantly different among different concentrations of CSC.

Conclusion: The results of this study help illustrate that nicotine-induced S. mutans biofilm formation is reduced by the presence of EGCG. This provides further evidence of the potential beneficial properties of polyphenols.

An in-vitro comparison of four antibacterial agents with and without nicotine and their effects on human gingival fibroblasts

BACKGROUND

To compare anti-bacterial activity of 0.12% Chlorhexidine (CHX), 10% Povidone Iodine (PVD), Vega Oral Care Gel (VEGA) and Antioxidant Gel (AO) on Streptococcus mutans, Streptococcus sanguis, Fusobacterium nucleatum and Porphyromonas gingivalis with and without nicotine and to evaluate their effects on human gingival fibroblasts (HGFs).

METHODS

S. mutans, S. sanguis, P. gingivalis and F. nucleatum were incubated with serial dilutions (1/4, 1/8, 1/16, 1/32 and 1/64) of anti-bacterial agents in media (with and without nicotine). Minimum inhibitory and minimum bactericidal concentrations (MIC/MBC) were measured, and confocal microscopy was performed.  HGFs were exposed to serial dilutions (1/10, 1/100, 1/1000 and 1/10,000) of antibacterial agents with media. Water-soluble tetrazolium-1 (WST-1) assay and lactate dehydrogenase (LDH) assay were used to assess proliferation and cytotoxicity towards HGFs.

RESULTS

CHX and PVD significantly inhibited growth of all bacterial species (p<0.0001) at all dilutions. AO and VEGA inhibited growth of all bacterial species up to only the 1/4 dilution. CHX and PVD decreased HGF proliferation at 1/10 and 1/100 dilution, while AO at all dilutions (p<0.05). CHX and AO were cytotoxic at all dilutions (p<0.05). VEGA was not cytotoxic to HGFs and did not affect HGF proliferation at any dilution (p>0.05). An increased bacterial growth was seen for all species except P. gingivalis with addition of nicotine.

CONCLUSION

CHX and PVD demonstrate superior antibacterial properties, but significantly reduce HGF proliferation. AO is bacteriostatic at lower dilutions but is highly toxic to HGFs. VEGA was bacteriostatic and demonstrated no detrimental effects on HGF's. This article is protected by copyright. All rights reserved.

Antibacterial Activities of Methanol and Aqueous Extracts of Salvadora persica against Streptococcus mutans Biofilms: An In Vitro Study

The use of herbal products in oral hygiene care has a long history, and their use is popular today. A tree stick, named Salvadora persica (S. persica), is commonly used to remove dental plaque and clean teeth in many countries. In addition, extracts of S. persica can be used as a mouthwash, as they demonstrate antimicrobial properties. This study aimed to investigate the antibacterial effect of S. persica methanol and aqueous extracts against Streptococcus mutans (S. mutans) biofilm. A S. mutans biofilm formation assay was conducted using different concentrations of S. persica methanol or water extracts in tryptic soy broth (TSB) supplemented with 1% sucrose. The biofilm was stained with crystal violet dye, and the absorbance was assessed to examine biofilm formation. One-way analysis of variance (ANOVA) and Tukey tests were used to analyze the results. The S. persica methanol extract displayed a significant inhibition (p ≤ 0.001) against the S. mutans biofilm. The 10 mg/mL concentration of the S. persica methanol extract was determined as the minimum biofilm inhibitory concentration (MBIC). The used methanol concentration, mixed with TSB supplemented with 1% sucrose and without the S. persica extract, did not inhibit the S. mutans biofilm. The S. persica aqueous extract did not demonstrate any biofilm inhibition at any concentration (p ≥ 0.05). The findings of this study suggest the potential of using S. persica methanol extract as a mouthwash or adjunctive to oral hygiene tools.

In vitro comparison of root surface roughness and bacterial adhesion following treatment with three different instruments

BACKGROUND

A novel device, piezoelectric 11 Gracey curet tip, reportedly combines benefits of a piezoelectric device and manual curet. The primary objective of this study was to compare root surface roughness outcomes between traditional manual curets and piezoelectric devices, as compared with this novel device. The secondary aim was to assess the level of adhesion of Streptococcus mutans on the root surface after instrumentation.

METHODS

The groups consisted of the following: 1) Gracey curet; 2) piezoelectric scaler; 3) piezoelectric 11 Gracey curet tip; and 4) untreated control. Root specimens were obtained from extracted human teeth and randomly assigned to each group. Surface roughness measurements (Ra and Rz) were taken with a profilometer before and after instrumentation. After instrumentation, root specimens were inoculated with S. mutans and biofilm was dislodged. Various dilutions of resuspended biofilm were incubated on blood agar plates and colony forming units (CFU) values were measured.

RESULTS

The experimental device resulted in significantly lower Ra and Rz compared with other groups (P < 0.01), and the Gracey curet was significantly lower than the piezoelectric tip and untreated control (P < 0.05). The Gracey curet and experimental device tip had significantly lower CFU values compared with the control (P < 0.05). There were no significant CFU value differences between the Gracey curet and both the piezoelectric and experimental device tips. There were no significant CFU differences between piezoelectric tip and both experimental device and control. There was no correlation between Ra and CFU values for Gracey curet, piezoelectric tip, or the control. However, correlation between Ra values and CFU approached significance for the experimental device (correlation = 0.66, P = 0.05).

CONCLUSIONS

Piezoelectric 11 Gracey curet tip is effective at resulting in a significantly smoother surface compared with traditional piezoelectric and hand instruments. CFU values with piezoelectric 11 Gracey curet tip were significantly lower than non-instrumented surfaces, but there were no significant differences compared with conventional methods.

Resin-based dental materials containing 3-aminopropyltriethoxysilane modified halloysite-clay nanotubes for extended drug delivery

OBJECTIVE

To synthesize and characterize a novel resin-based dental material containing 3-aminopropyltriethoxysilane (APTES) surface-modified halloysite-clay nanotubes (HNTs) for long-term delivery of guest molecules.

METHODS

The optimal concentrations of HNT (10, 15, 20 wt.%) and silane (0, 2, 4 vol.%sil) to be incorporated into the resin-based materials were determined (15 wt.%HNT, 4 vol.%sil) after assessment of the mechanical properties (DC%, degree of conversion; FS, flexural strength; FM, flexural modulus; and UTS, ultimate tensile strength). The HNTsil-powder was loaded with chlorhexidine (CHX) to evaluate the effect of the silanization on drug release. Resin-discs were prepared for the following groups: RES (resin), HNT (resin+15 wt.%HNT), HNTsil (resin+15 wt.%HNT silanized), HNT-CHX (resin+15 wt.%HNT loaded with chlorhexidine), HNTsil-CHX (resin+15 wt.%HNTsil-CHX), and 0.2 vol.%CHX (resin+0.2 vol.%CHX solution). Specimens were stored in water for 1, 3, 5, 10, and 15 days at 37 °C. Aliquots from each time point and the final 15-day specimens were evaluated for the zone of inhibition (ZOI) against Streptococcus mutans. CHX release was analyzed using spectrophotometry at absorbance of 300 nm. Data were statistically analyzed (α = 0.05).

RESULTS

All materials presented similar DC%. Reduced FS but increased FM was detected for 20 wt.%HNT-4%APTES. Groups with 15 wt.% and 20 wt.%HNT with/without APTES presented higher values of UTS. Agar diffusion data indicates that the HNTsil-CHX had a greater ZOI than all other groups over 15 days. HNTsil-CHX had the highest absorbance for day 1 but presented similar values to other groups every time point after.

SIGNIFICANCE

Silanization of nanotubes followed by encapsulation of chlorhexidine is a promising technique for long-term delivery of guest molecules.

Effects of platelet-rich fibrin on human gingival and periodontal ligament fibroblast proliferation from chronic periodontitis versus periodontally healthy subjects

BACKGROUND

Platelet-rich fibrin (PRF), an autogenous blood concentrate, contains multiple growth factors and is used as an adjunct in the periodontal regeneration and implant site development procedures to stimulate wound healing. Patient-related factors such as chronic periodontitis may affect the quality of PRF.

OBJECTIVES

This study aimed to investigate and compare PRF's effects from patients diagnosed with generalized moderate or severe chronic periodontitis to patients who presented with intact periodontium on human gingival fibroblast (HGF) and human periodontal ligament fibroblast (HPLF) proliferation.

MATERIALS AND METHODS

A total of 33 ml of whole intravenous blood was collected from each subject and centrifuged at 2700 rpm for 12 min in three 10 ml tubes, and 3 ml of blood was used for Complete Blood Count analysis. Three PRF clots were compressed to produce the membranes and liquid exudate. PRF membrane and 10% liquid exudate were exposed to 20,000 HPLFs/well or 25,000 HGFs/well in triplets from each subject in a 48 cell well plate. After 72 h of incubation, the conditioned media were evaluated by Water Soluble Tetrazolium-1 assays to determine fibroblast proliferation. Controls included cells alone and media without cells. Complete blood counts were measured.

RESULTS

Subjects in both groups were age and gender-matched (intact 46.7 ± 11.4 years and periodontitis 54.8 ± 10.4 years, p-value = 0.1344). Body Mass Index and White Blood Corpuscles in the periodontitis group was significantly higher than the intact group (p = 0.0176 and p = 0.0038) whereas no differences were seen for Red Blood Corpuscles (p = 0.2020), Hemoglobin (p = 0.2290) and Platelets (p = 4,094). There were no significant differences in the HGF and HPLF proliferation with PRF exudates and membranes between intact periodontium and periodontitis groups (all p > 0.05). However, PRF exudates in both groups induced significant more cell proliferation when compared to PRF membranes.

CONCLUSIONS

PRF exudates induced significant proliferation of fibroblasts and can play a vital role in wound healing. The current study concluded that PRF membranes, in combination with PRF exudates, can be utilized for their therapeutic and wound healing potential, not affected by the periodontal condition of the patient.

Combined effects of soft drinks and nicotine on Streptococcus mutans metabolic activity and biofilm formation

The purpose of this study was to explore the effects of nicotine on the activity of Streptococcus mutans (S. mutans) in soft drinks. Regular soft drinks contain large proportions of high-fructose corn syrup (HFCS), which increases the activity of S. mutans resulting in high-caries risk compared with sugar-free soft drinks. Nicotine use exhibits a strong correlation with increased S. mutans biofilm formation. The soft drinks chosen were (Coca-Cola Classic, Diet Coke, Coca-Cola Zero Sugar, Caffeine-Free Coca-Cola, Caffeine-Free Diet Coke, Caffeine-Free Coca-Cola Zero Sugar). S. mutans was grown overnight in tryptic soy broth; nicotine was diluted in tryptic soy broth supplemented with 1.0% sucrose followed by soft drinks in dilution of 1:3. Total growth absorbance and biofilm growth were determined by spectrophotometry, absorbance measured to determine biofilm formation, and metabolic activity quantified. One-way ANOVA showed a considerable effect for HFCS and caffeine in the presence of nicotine and their interaction in all measures. Results showed sugar-free caffeinated colas demonstrated significant effect in inhibiting S. mutans biofilm formation and metabolic activity with nicotine. Nicotine-induced S. mutans increased biofilm formation and metabolic activity in the presence of HFCS and caffeine in soft drinks. In conclusion, smokers should consider sugar-free caffeinated versions to minimize the chance of developing dental caries dut to the reduction of biofilm formation.

Development of an antibacterial and anti-metalloproteinase dental adhesive for long-lasting resin composite restorations

Despite all the advances in adhesive dentistry, dental bonds are still fragile due to degradation events that start during application of adhesive agents and the inherent hydrolysis of resin-dentin bonds. Here, we combined two outstanding processing methods (electrospinning and cryomilling) to obtain bioactive (antimicrobial and anti-metalloproteinase) fiber-based fillers containing a potent matrix metalloproteinase (MMP) inhibitor (doxycycline, DOX). Poly(ε)caprolactone solutions containing different DOX amounts (0, 5, 25, and 50 wt%) were processed via electrospinning, resulting in non-toxic submicron fibers with antimicrobial activity against Streptococcus mutans and Lactobacillus. The fibers were embedded in a resin blend, light-cured, and cryomilled for the preparation of fiber-containing fillers, which were investigated with antibacterial and in situ gelatin zymography analyzes. The fillers containing 0, 25, and 50 wt% DOX-releasing fibers were added to aliquots of a two-step, etch-and-rinse dental adhesive system. Mechanical strength, hardness, degree of conversion (DC), water sorption and solubility, bond strength to dentin, and nanoleakage analyses were performed to characterize the physico-mechanical, biological, and bonding properties of the modified adhesives. Statistical analyses (ANOVA; Kruskal-Wallis) were used when appropriate to analyze the data (α = 0.05). DOX-releasing fibers were successfully obtained, showing proper morphological architecture, cytocompatibility, drug release ability, slow degradation profile, and antibacterial activity. Reduced metalloproteinases (MMP-2 and MMP-9) activity was observed only for the DOX-containing fillers, which have also demonstrated antibacterial properties against tested bacteria. Adhesive resins modified with DOX-containing fillers demonstrated greater DC and similar mechanical properties as compared to the fiber-free adhesive (unfilled control). Concerning bonding performance to dentin, the experimental adhesives showed similar immediate bond strengths to the control. After 12 months of water storage, the fiber-modified adhesives (except the group consisting of 50 wt% DOX-loaded fillers) demonstrated stable bonds to dentin. Nanoleakage was similar among all groups investigated. DOX-releasing fibers showed promising application in developing novel dentin adhesives with potential therapeutic properties and MMP inhibition ability; antibacterial activity against relevant oral pathogens, without jeopardizing the physico-mechanical characteristics; and bonding performance of the adhesive.

In-Vitro Model of Scardovia wiggsiae Biofilm Formation and Effect of Nicotine

Recently, Scardovia wiggsiae has been reported to be strongly associated with caries formation. This study aimed to establish an in vitro model of S. wiggsiae biofilm and to investigate the effect of nicotine on S. wiggsiae colony-forming units (CFUs) growth. S. wiggsiae biofilm was grown overnight using brain-heart infusion (BHI) broth supplemented with 5 g of yeast extract/L (BHI-YE). The overnight culture was used as an inoculum to grow S. wiggsiae biofilm on standardized enamel and dentin samples. Samples were incubated with different nicotine concentrations (0, 0.5, 1, 2, 4, 8, 16 and 32 mg/mL) for 3 days. The dissociated biofilms were diluted, spiral plated on blood agar plates, and incubated for 24 h. CFUs/mL were quantified using an automated colony counter. A two-way ANOVA was used to compare the effect of different nicotine concentrations on S. wiggsiae CFUs. This study demonstrated that S. wiggsiae biofilm could be initiated and formed in vitro. Increased CFUs was observed through 0.5-4 mg/mL and 0.5-8 mg/mL of nicotine using enamel and dentin substrates, respectively. 16 and 32 mg/mL of nicotine were determined as the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC), respectively. S. wiggsiae formed greater biofilm on enamel than dentin specimens in response to the nicotine stimulus. This study demonstrated the negative effect of smoking on increasing S. wiggsiae biofilm. Establishing S. wiggsiae biofilm in vitro may allow researchers in the future to have a better understanding of caries pathogenesis and bacterial interaction.

Synthesis of multifunctional chlorhexidine-doped thin films for titanium-based implant materials

Our goal was to create bio-functional chlorhexidine (CHX)-doped thin films on commercially pure titanium (cpTi) discs using the glow discharge plasma approach. Different plasma deposition times (50, 35 and 20 min) were used to create bio-functional surfaces based on silicon films with CHX that were compared to the control groups [no CHX and bulk cpTi surface (machined)]. Physico-chemical and biological characterizations included: 1. Morphology, roughness, elemental chemical composition, film thickness, contact angle and surface free energy; 2. CHX-release rate; 3. Antibacterial effect on Streptococcus sanguinis biofilms at 24, 48 and 72 h; 4. Cytotoxicity and metabolic activity using fibroblasts cell culture (NIH-F3T3 cells) at 1, 2, 3 and 4 days; 5. Protein expression by NIH-F3T3 cells at 1, 2, 3 and 4 days; and 6. Co-culture assay of fibroblasts cells and S. sanguinis to assess live and dead cells on the confocal laser scanning microscopy, mitochondrial activity (XTT), membrane leakage (LDH release), and metabolic activity (WST-1 assay) at 1, 2 and 3 days of co-incubation. Data analysis showed that silicon films, with or without CHX coated cpTi discs, increased surface wettability and free energy (p < 0.05) without affecting surface roughness. CHX release was maintained over a 22-day period and resulted in a significant inhibition of biofilm growth (p < 0.05) at 48 and 72 h of biofilm formation for 50 min and 20 min of plasma deposition time groups, respectively. In general, CHX treatment did not significantly affect NIH-F3T3 cell viability (p > 0.05), whereas cell metabolism (MTT assay) was affected by CHX, with the 35 min of plasma deposition time group displaying the lowest values as compared to bulk cpTi (p < 0.05). Moreover, data analysis showed that films, with or without CHX, significantly affected the expression profile of inflammatory cytokines, including IL-4, IL-6, IL-17, IFN-y and TNF-α by NIH-F3T3 cells (p < 0.05). Co-culture demonstrated that CHX-doped film did not affect the metabolic activity, cytotoxicity and viability of fibroblasts cells (p > 0.05). Altogether, the findings of the current study support the conclusion that silicon films added with CHX can be successfully created on titanium discs and have the potential to affect bacterial growth and inflammatory markers without affecting cell viability/proliferation rates.

Effects of casein phosphopeptide-amorphous calcium phosphate crème on nicotine-induced Streptococcus mutans biofilm in vitro

OBJECTIVES

The aim of this study was to test the effects of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) crème, or MI Paste™ (MIP), on nicotine-induced Streptococcus mutans biofilm. The experiment utilized S. mutans biofilm assays with varying concentrations of nicotine and MIP aqueous concentrate levels. First hand exposure to nicotine has been demonstrated to significantly increase S. mutans biofilm formation, while the active component, CPP-ACP, in MIP has been shown to reduce S. mutans biofilm formation.

MATERIALS AND METHODS

A 24-h culture of S. mutans UA159 in microtiter plates were treated with varying nicotine concentrations (0-32 mg/ml) in Tryptic Soy Broth supplemented with 1% sucrose (TSBS) with or without MIP aqueous concentrate. A spectrophotometer was used to determine total growth absorbance and planktonic growth. The microtiter plate wells were washed, fixed, and stained with crystal violet dye and the absorbance measured to determine biofilm formation.

RESULTS

The presence of MIP aqueous concentrate inhibits nicotine-induced S. mutans biofilm formation at different concentrations of nicotine (0-32 mg/ml).

CONCLUSION

The results demonstrated nicotine-induced S. mutans biofilm formation is decreased in the presence of MIP. This provides further evidence about the cariostatic properties of CPP-ACP, the active soluble ingredient in the MIP, and reconfirms the harmful effects of nicotine.

CLINICAL SIGNIFICANCE

Smokers may gain dual benefits from the use of MIP, as a remineralization agent and as a cariostatic agent, by inhibiting nicotine-induced S. mutans biofilm formation.

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.

Effectiveness of in vitro primary coronal caries prevention with silver diamine fluoride - Chemical vs biofilm models

OBJECTIVES

The main goal of this study was to investigate the effectiveness of SDF and its individual components, silver (Ag⁺) and fluoride (F^-) ions, in preventing enamel demineralization using biofilm and chemical models.

METHODES

Polished human enamel specimens were assigned to five treatment groups (n = 18 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 (DIW). Treatments were applied once to sound enamel. In the biofilm model, specimens were demineralized by aerobic overnight incubation using cariogenic bacteria isolated from human saliva in brain heart infusion supplemented with 0.2 % sucrose for three days. In the chemical model, enamel specimens were immersed in a demineralizing solution containing 0.1 M lactic acid, 4.1 mM CaCl₂, 8.0 mM KH₂PO₄, 0.2 % Carbopol 907, pH adjusted to 5.0 for five days. Vickers surface microhardness was used to determine the extent of enamel demineralization. Data were analyzed using one-way ANOVA.

RESULTS

In the chemical model, there was no statistically significant difference between SDF and SDF + KI in preventing coronal caries (p < 0.0001). In the biofilm model, SDF + KI was significantly less effective in preventing demineralization than SDF (p < 0.0001). In both models, SDF and SDF + KI were superior in their ability to prevent caries lesion formation than AgNO₃ and DIW.

CONCLUSION

KI application after SDF treatment appears to impair SDF's ability to prevent biofilm-mediated but not chemically induced demineralization.

CLINICAL SIGNIFICANCE

SDF may be a viable option in preventing primary coronal caries.

Influence of salivary conditioning and sucrose concentration on biofilm-mediated enamel demineralization

INTRODUCTION

The acquired pellicle formation is the first step in dental biofilm formation. It distinguishes dental biofilms from other biofilm types.

OBJECTIVE

To explore the influence of salivary pellicle formation before biofilm formation on enamel demineralization.

METHODOLOGY

Saliva collection was approved by Indiana University IRB. Three donors provided wax-stimulated saliva as the microcosm bacterial inoculum source. Acquired pellicle was formed on bovine enamel samples. Two groups (0.5% and 1% sucrose-supplemented growth media) with three subgroups (surface conditioning using filtered/pasteurized saliva; filtered saliva; and deionized water (DIW)) were included (n=9/subgroup). Biofilm was then allowed to grow for 48 h using Brain Heart Infusion media supplemented with 5 g/l yeast extract, 1 mM CaCl2.2H2O, 5% vitamin K and hemin (v/v), and sucrose. Enamel samples were analyzed for Vickers surface microhardness change (VHNchange), and transverse microradiography measuring lesion depth (L) and mineral loss (∆Z). Data were analyzed using two-way ANOVA.

RESULTS

The two-way interaction of sucrose concentration × surface conditioning was not significant for VHNchange (p=0.872), ∆Z (p=0.662) or L (p=0.436). Surface conditioning affected VHNchange (p=0.0079), while sucrose concentration impacted ∆Z (p<0.0001) and L (p<0.0001). Surface conditioning with filtered/pasteurized saliva resulted in the lowest VHNchange values for both sucrose concentrations. The differences between filtered/pasteurized subgroups and the two other surface conditionings were significant (filtered saliva p=0.006; DIW p=0.0075). Growing the biofilm in 1% sucrose resulted in lesions with higher ∆Z and L values when compared with 0.5% sucrose. The differences in ∆Z and L between sucrose concentration subgroups was significant, regardless of surface conditioning (both p<0.0001).

CONCLUSION

Within the study limitations, surface conditioning using human saliva does not influence biofilm-mediated enamel caries lesion formation as measured by transverse microradiography, while differences were observed using surface microhardness, indicating a complex interaction between pellicle proteins and biofilm-mediated demineralization of the enamel surface.

In vitro Cariostatic effects of cinnamon water extract on nicotine-induced Streptococcus mutans biofilm

Background

Dental caries is one of the most prevalent chronic oral diseases worldwide. Dental caries is mainly associated with Streptococcus mutans and the Lactobacillus species. A specific relationship was found between nicotine and S. mutans growth as the presence of nicotine increased S. mutans biofilm formation. Nicotine is able to increase the number of S. mutans and extracellular polysaccharide (EPS) synthesis. Among the widely used herbs and spices is cinnamon which demonstrated a strong antibacterial activity against a wide variety of bacteria including S. mutans and showed the ability to inhibit S. mutans biofilm formation. Cinnamon essential oil, obtained from the leaves of C. zeylanicum, has been demonstrated to be effective against S. mutans and Lactobacillus acidophilus, which are partially responsible for dental plaque formation and caries development. The aim of this study was to identify the effects of nicotine exposure on the inhibitory effects of cinnamon water extract on S. mutans biofilm formation.

Materials and methods

A 24-h culture of S. mutans UA159 in microtiter plates was treated with varying nicotine concentrations (0–32 mg/ml) in Tryptic Soy broth supplemented with 1% sucrose (TSBS) with or without a standardized concentration (2.5 mg/ml) of cinnamon water extract. A spectrophotometer was used to determine total growth absorbance and planktonic growth. The microtiter plate wells were washed, fixed and stained with crystal violet dye and the absorbance measured to determine biofilm formation.

Results

The presence of 2.5 mg/ml cinnamon water extract inhibits nicotine-induced S. mutans biofilm formation from 34 to 98% at different concentrations of nicotine (0–32 mg/ml).

Conclusion

The results demonstrated nicotine-induced S. mutans biofilm formation is decreased from 34 to 98% in the presence of 2.5 mg/ml cinnamon water extract. This provides further evidence about the biofilm inhibitory properties of cinnamon water extract and reconfirms the harmful effects of nicotine.

The Impact of Nicotine and Cigarette Smoke Condensate on Metabolic Activity and Biofilm Formation of Candida albicans on Acrylic Denture Material

PURPOSE

Smokers have increased denture stomatitis caused primarily by Candida albicans. The primary aim of this study was to demonstrate the impact of a wide range of nicotine and cigarette smoke condensate (CSC) concentrations on biofilm formation and metabolic activity of C. albicans on acrylic denture material.

MATERIALS AND METHODS

C. albicans (ATCC strain 10231) was used. Standardized denture acrylic (PMMA) specimens (total of 135 specimens) were incubated with C. albicans and exposed to nicotine and CSC at different concentrations (0, 0.25, 0.5, 1, 2, 4, 8, 16, and 32 mg/ml) and (0, 0.25, 0.5, 1, 2, and 4 mg/ml), respectively. For each experiment, 3 samples per nicotine and CSC concentration and a total of 45 specimens (27 specimens for the nicotine and 18 specimens for the CSC-treated samples) were used and were selected randomly for each group. The control group consisted of 0 mg/ml of nicotine or CSC. The viability of C. albicans was measured using spiral plating on blood agar plates. The effect of nicotine and CSC concentrations on planktonic cells was were measured using a microplate reader. Metabolic activity of 24-hour-old established C. albicans biofilm exposed to nicotine and CSC for 24 hours in microtiter plates was determined using a 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-carboxanilide (XTT) reduction assay.

RESULTS

The viability of C. albicans increased concomitant with increasing concentrations of CSC and nicotine, particularly at 0.5 and 2 mg/ml, respectively. Concentrations of CSC and nicotine above this resulted in an inhibitory effect on C. albicans viability. CSC and nicotine at 4 and 16 mg/ml, respectively, increased C. albicans biofilm metabolic activity.

CONCLUSION

Nicotine and CSC up to certain concentrations caused increases in biofilm formation, metabolic activity, viability, and planktonic cell absorbance of C. albicans. This in vitro study demonstrates the effectiveness of tobacco on promoting the growth of C. albicans and suggests their potential contributing factor in C. albicans biofilm related infections in smokers.

Photoinhibition of Streptococcus mutans Biofilm-Induced Lesions in Human Dentin by Violet-Blue Light

This in vitro study determined the effectiveness of violet-blue light on Streptococcus mutans (UA159) biofilm induced dentinal lesions. Biofilm was formed on human dentin specimens in a 96-well microtiter plate and incubated for 13 h in the presence of tryptic soy broth (TSB) or TSB supplemented with 1% sucrose (TSBS). Violet-blue light (405 nm) from quantitative light-induced fluorescence (QLF^TM) was used to irradiate the biofilm. Supernatant liquid was removed, and the biofilm was irradiated continuously with QLF for 5 min twice daily with an interval of 6 h for 5 d, except with one treatment on the final day. Colony forming units (CFU) of the treated biofilm, changes in fluorescence (∆F; QLF-Digital Biluminator^TM), lesion depth (L), and integrated mineral loss (∆Z; both transverse microradiography) were quantified at the end of the fifth day. Statistical analysis used analysis of variance (ANOVA), testing at a 5% significance level. In the violet-blue light irradiated groups, there was a significant reduction (p < 0.05) of bacterial viability (CFU) of S. mutans with TSB and TSBS. Violet-blue light irradiation resulted in the reduction of ∆F and L of the dentinal surface with TSBS. These results indicate that violet-blue light has the capacity to reduce S. mutans cell numbers.

Oral Health Effects of Combusted and Smokeless Tobacco Products

The oral cavity is usually the first part of a consumer's body exposed to the constituents of tobacco products or their emissions. Consequently, the oral cavity is a frequent site for carcinogenic, microbial, immunologic, and clinical effects of tobacco use. This article summarizes 5 presentations on various aspects of oral health affected by combusted or noncombusted tobacco products from a recent conference, "Oral Health Effects of Tobacco Products: Science and Regulatory Policy," sponsored by the American Association for Dental Research and the Food and Drug Administration.

Impact of caffeine on metabolic activity and biofilm formation of Candida albicans on acrylic denture resin in the presence of nicotine

STATEMENT OF PROBLEM

Candida albicans has been implicated in denture stomatitis, and this effect is exacerbated by nicotine exposure. However, studies have also suggested that caffeine exposure inhibits the growth of C. albicans. The interaction effects of nicotine and caffeine are not yet clear on the growth of C. albicans.

PURPOSE

The purpose of this in vitro study was to determine the effect of caffeine on metabolic activity and biofilm formation of C. albicans growing on acrylic denture resin while simultaneously exposed to nicotine and, if an effect were to be identified, whether this effect would vary depending on the caffeine concentration.

MATERIAL AND METHODS

A total of 240 acrylic resin specimens were divided into 2 equal groups (120 each). Specimens in one group were processed to measure C. albicans metabolic activity, and those in the other group were processed to measure C. albicans biofilm attachment. Ten subgroups (n=12) were established within each group with different concentration combinations of nicotine and caffeine to test the interaction effect. The first subgroup was designed as a negative control, containing 0 mg/mL of nicotine and caffeine. The following subgroups all contained 8.00 mg/mL of nicotine, and the caffeine concentrations were prepared at the following 9 levels: 0, 0.25, 0.50, 1.00, 2.00, 4.00, 8.00, 16.00, and 32.00 mg/mL. Metabolic activity was measured by using a 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-carboxanilide (XTT) assay. Biofilm attachment was measured by using spiral plating and calculated in terms of the number of colony-forming units (CFUs)/mL. Descriptive statistics and a 2-way ANOVA were conducted to determine whether the concentrations of nicotine and caffeine used affected the biofilm attachment and metabolic activity of C. albicans (α=.05).

RESULTS

The presence of 8 mg/mL of nicotine increased the metabolic activity and biofilm formation of C. albicans. When compared with the 0 mg/mL of caffeine and 8.00 mg/mL of nicotine group, caffeine from 1.00 to 4.00 mg/mL significantly increased C. albicans biofilm metabolic activity. Caffeine at 16.00 and 32.00 mg/mL significantly decreased C. albicans biofilm metabolic activity in the presence of 8 mg/mL of nicotine. Caffeine from 1.00 to 32.00 mg/mL significantly decreased the biofilm formation of C. albicans in the presence of 8 mg/mL of nicotine.

CONCLUSIONS

The presence of 8 mg/mL of nicotine alone increased the metabolic activity and biofilm formation of C. albicans. In the presence of 8 mg/mL of nicotine with different caffeine concentrations, the results suggest that, overall, caffeine at higher concentrations (16 and 32 mg/mL) inhibited the metabolic activity and biofilm formation of C. albicans on acrylic denture resin most.

Curcumin-A Natural Medicament for Root Canal Disinfection: Effects of Irrigation, Drug Release, and Photoactivation

INTRODUCTION

Curcumin incorporation into polymeric fibers was tested for its antimicrobial properties and potential use in root canal disinfection.

METHODS

Curcumin-modified fibers were processed via electrospinning and tested against a 7-day old established Actinomyces naeslundii biofilm. The medicaments tested were as follows: curcumin-modified fibers at 2.5 and 5.0 mg/mL, curcumin-based irrigant at 2.5 and 5.0 mg/mL, saline solution (negative control), and the following positive controls: 2% chlorhexidine, 1% sodium hypochlorite, and triple antibiotic paste (TAP, 1 mg/mL). All medicaments, except for the positive controls, were allocated according to the light exposure protocol (ie, photoactivation with a light-emitting diode every 30 seconds for 4 minutes or without photoactivation). After treatment, the medicaments were removed, and 1 mL saline solution was added; the biofilm was scraped from the well and used to prepare a 1:2000 dilution. Spiral plating was performed using anaerobic blood agar plates. After 24 hours, colony-forming units (colony-forming units/mL, n = 11/group) were counted to determine the antimicrobial effects.

RESULTS

Data exhibited significant antimicrobial effects on the positive control groups followed by the curcumin irrigants and, lastly, the photoactivated curcumin-modified fibers. There was a significant reduction of viable bacteria in curcumin-based irrigants, which was greater than the TAP-treated group. Curcumin-free fibers, saline, and the nonphotoactivated curcumin-modified fibers did not display antimicrobial activity.

CONCLUSIONS

Curcumin seems to be a potential alternative to TAP when controlling infection, but it requires a minimal concentration (2.5 mg/mL) to be effective. Photoactivation of curcumin-based medicaments seems to be essential to obtain greater antibiofilm activity.

Effect of nicotine on biofilm formation of Streptococcus mutans isolates from smoking and non-smoking subjects

Objectives: To investigate effects of nicotine on biofilm formation of Streptococcus mutans isolates from oral washes of smoker and non-smoker human subjects. Materials and methods: This study was conducted using 60 S. mutans isolates with three S. mutans isolates collected from oral washes of ten smoking subjects and ten from non-smoking subjects. Biofilm was formed by culturing each S. mutans strain (10 μl) in 190 μl of TSB supplemented with 1% sucrose (TSBS) containing 0, 0.25, 0.5, 1.0, 2.0, 4.0, 8.0, 16.0, and 32.0 mg/ml of nicotine for 24 h in 5% CO2 at 37°C in 96 well microtiter plates. The absorbance values of biofilm were measured at 490 nm in a microplate spectrophotometer. Results: There was a significant effect (p-value < 0.05) of nicotine concentrations and smoking on the growth of biofilm, planktonic cells, and total absorbance, for all strains of S. mutans. Isolates from smokers had significantly more biofilm at 0-16 mg/ml of nicotine compared to those from non-smokers (p-value < 0.0001). Conclusion: S. mutans smoker isolates are more affected by high nicotine concentrations than non-smoker isolates. Clinical Relevance: The use of nicotine products increases the growth of S. mutans and may place tobacco users at risk for dental decay.

Inhibition of nicotine-induced Streptococcus mutans biofilm formation by salts solutions intended for mouthrinses

OBJECTIVES

Biofilm formation is critical to dental caries initiation and development. The aim of this study was to investigate the effects of nicotine exposure on Streptococcus mutans (S. mutans) biofilm formation concomitantly with the inhibitory effects of sodium chloride (NaCl), potassium chloride (KCl) and potassium iodide (KI) salts. This study examined bacterial growth with varying concentrations of NaCl, KCl, and KI salts and nicotine levels consistent with primary levels of nicotine exposure.

MATERIALS AND METHODS

A preliminary screening experiment was performed to investigate the appropriate concentrations of NaCl, KCl, and KI to use with nicotine. With the data, a S. mutans biofilm growth assay was conducted using nicotine (0-32 mg/mL) in Tryptic Soy broth supplemented with 1% sucrose with and without 0.45 M of NaCl, 0.23 M of KCl, and 0.113 M of KI. The biofilm was stained with crystal violet dye and the absorbance measured to determine biofilm formation.

RESULTS

The presence of 0.45 M of NaCl, 0.23 M of KCl, and 0.113 M of KI significantly inhibited (p < 0.05) nicotine-induced S. mutans biofilm formation by 52%, 79.7%, and 64.1%, respectively.

CONCLUSIONS

The results provide additional evidence regarding the biofilm-enhancing effects of nicotine and demonstrate the inhibitory influence of these salts in reducing the nicotine-induced biofilm formation. A short-term exposure to these salts may inhibit S. mutans biofilm formation.

Silver Diamine Fluoride and Potassium Iodide Disruption of In Vitro Streptococcus mutans Biofilm

Purpose: The purpose of this study was to investigate the inhibitory in vitro effects of silver diamine fluoride (SDF) with and without a saturated solution of potassium iodide (SSKI) on established Streptococcus mutans biofilm.Methods: Fifty μl of an overnight S. mutans culture (10⁶ CFU per mL) in Tryptic Soy Broth (TSB) and three ml of fresh TSB supplemented with one percent sucrose (TSBS) were incubated for 24 hours to establish an S. mutans biofilm in six-well tissue culture plates. Four treatments (SDF, SSKI, SDF plus SSKI, and untreated control) were used to disrupt the biofilm. The biofilm groups were each treated with reagent and washed; the biofilm was collected, diluted, and spiral-plated onto blood agar plates; and an automated counting machine was used to determine the bacterial colony forming units (CFU).Results: The control had significantly more CFU than the SSKI, SDF, and SDF plus SSKI groups (P<.0001). The SSKI group had significantly more CFU than the SDF and SDF plus SSKI groups (P<.0001). The SDF group had significantly fewer CFU than the SDF plus SSKI group (P=.02). The reduction from the control was more than seven-fold for SDF, four-fold for SDF plus SSKI, and two-fold for SSKI.Conclusions: SDF alone, SDF plus SSKI, and SSKI disrupted an established S. mutans biofilm. SDF alone had the greatest overall disruption.

Effect of phototherapy on the metabolism of Streptococcus mutans biofilm based on a colorimetric tetrazolium assay

The aim of this in vitro study was to determine the effect of violet-blue light on the metabolic activity of early Streptococcus mutans biofilm, reincubated at 0, 2, and 6 h after 5 min of violet-blue light treatment. S. mutans UA159 biofilm cells were cultured for 12 to 16 h in microtiter plates with Tryptic Soy broth (TSB) or TSB with 1% sucrose (TSBS) and irradiated with violet-blue light for 5 min. After irradiation, the plates were reincubated at 37°C for 0, 2, or 6 h in 5% CO₂. Colorimetric tetrazolium salt reduction assay was used to investigate bacterial metabolic activity. Mixed model ANOVA was used to find the difference between the violet-blue light treated and nontreated groups. Bacterial metabolic activity was significantly lower in the violet-blue light group for TSB than in the nontreated group (P < 0.0001) regardless of recovery time. However, the differences between metabolic activity in the treated groups without sucrose decreased over time. For TSBS, metabolic activity was significantly lower with violet-blue light at 0 and 2 h. Violet-blue light inhibited the metabolic activity of S. mutans biofilm cells in the light-treated group. This finding may present a unique treatment method for patients with active caries.

Caries lesion remineralization with fluoride toothpastes and chlorhexidine - effects of application timing and toothpaste surfactant

Habitual toothbrushing with fluoridated toothpaste followed by rinsing with antibacterial mouthwashes is a method to maintain good oral hygiene and to diminish the occurrence and severity of dental caries and periodontal disease. However, our understanding of how antimicrobial agents in mouthwashes affect fluoride-mediated caries lesion remineralization is still poor.

Oral Sciences PhD Program Enrollment, Graduates, and Placement: 1994 to 2016

For decades, dental schools in the United States have endured a significant faculty shortage. Studies have determined that the top 2 sources of dental faculty are advanced education programs and private practice. Those who have completed both DDS and PhD training are considered prime candidates for dental faculty positions. However, there is no national database to track those trainees and no evidence to indicate that they entered academia upon graduation. The objective of this study was to assess outcomes of dental school-affiliated oral sciences PhD program enrollment, graduates, and placement between 1994 and 2016. Using the American Dental Association annual survey of advanced dental education programs not accredited by the Commission on Dental Accreditation and data obtained from 22 oral sciences PhD programs, we assessed student demographics, enrollment, graduation, and placement. Based on the data provided by program directors, the average new enrollment was 33, and graduation was 26 per year. A total of 605 graduated; 39 did not complete; and 168 were still in training. Among those 605 graduates, 211 were faculty in U.S. academic institutions, and 77 were faculty in foreign institutions. Given that vacant budgeted full-time faculty positions averaged 257 per year during this period, graduates from those oral sciences PhD programs who entered academia in the United States would have filled 9 (3.6%) vacant faculty positions per year. Therefore, PhD programs have consistently generated only a small pipeline of dental school faculty. Better mentoring to retain talent in academia is necessary. Stronger support and creative funding plans are essential to sustain the PhD program. Furthermore, the oral sciences PhD program database should be established and maintained by dental professional organizations to allow assessments of training models, trends of enrollment, graduation, and placement outcomes.

The Effect of Touch on a Visually Ambiguous Three-dimensional Figure

The effect of haptic (i.e. tactile-kinaesthetic) information on the perception of an ambiguous visual figure was investigated. The figure used was a self-luminous, threedimensional wire cube viewed in darkness. It was found that visual reversals still took place when the cube was explored with the hands, but the reversal rate was reduced and the time increased during which the cube looked as it “really” was.

Clindamycin-modified Triple Antibiotic Nanofibers: A Stain-free Antimicrobial Intracanal Drug Delivery System

INTRODUCTION

A biocompatible strategy to promote bacterial eradication within the root canal system after pulpal necrosis of immature permanent teeth is critical to the success of regenerative endodontic procedures. This study sought to synthesize clindamycin-modified triple antibiotic (metronidazole, ciprofloxacin, and clindamycin [CLIN]) polymer (polydioxanone [PDS]) nanofibers and determine in vitro their antimicrobial properties, cell compatibility, and dentin discoloration.

METHODS

CLIN-only and triple antibiotic CLIN-modified (CLIN-m, minocycline-free) nanofibers were processed via electrospinning. Scanning electron microscopy, Fourier-transform infrared spectroscopy (FTIR), and tensile testing were performed to investigate fiber morphology, antibiotic incorporation, and mechanical strength, respectively. Antimicrobial properties of CLIN-only and CLIN-m nanofibers were assessed against several bacterial species by direct nanofiber/bacteria contact and over time based on aliquot collection up to 21 days. Cytocompatibility was measured against human dental pulp stem cells. Dentin discoloration upon nanofiber exposure was qualitatively recorded over time. The data were statistically analyzed (P < .05).

RESULTS

The mean fiber diameter of CLIN-containing nanofibers ranged between 352 ± 128 nm and 349 ± 128 nm and was significantly smaller than PDS fibers. FTIR analysis confirmed the presence of antibiotics in the nanofibers. Hydrated CLIN-m nanofibers showed similar tensile strength to antibiotic-free (PDS) nanofibers. All CLIN-containing nanofibers and aliquots demonstrated pronounced antimicrobial activity against all bacteria. Antibiotic-containing aliquots led to a slight reduction in dental pulp stem cell viability but were not considered toxic. No visible dentin discoloration upon CLIN-containing nanofiber exposure was observed.

CONCLUSIONS

Collectively, based on the remarkable antimicrobial effects, cell-friendly, and stain-free properties, our data suggest that CLIN-m triple antibiotic nanofibers might be a viable alternative to minocycline-based antibiotic pastes.

In Vitro Effects of Sports and Energy Drinks on Streptococcus mutans Biofilm Formation and Metabolic Activity

PURPOSE

Sports and energy drinks are being increasingly consumed and contain large amounts of sugars, which are known to increase Streptococcus mutans biofilm formation and metabolic activity. The purpose of this in vitro study was to investigate the effects of sports and energy drinks on S. mutans biofilm formation and metabolic activity.

METHODS

S. mutans UA159 was cultured with and without a dilution (1:3 ratio) of a variety of sports and energy drinks in bacterial media for 24 hours. The biofilm was washed, fixed, and stained. Biofilm growth was evaluated by reading absorbance of the crystal violet. Biofilm metabolic activity was measured by the biofilm-reducing XTT to a water-soluble orange compound.

RESULTS

Gatorade Protein Recovery Shake and Starbucks Doubleshot Espresso Energy were found to significantly increase biofilm (30-fold and 22-fold, respectively) and metabolic activity (2-fold and 3-fold, respectively). However, most of the remaining drinks significantly inhibited biofilm growth and metabolic activity.

CONCLUSIONS

Several sports and energy drinks, with sugars or sugar substitutes as their main ingredients inhibited S. mutans biofilm formation. Among the drinks evaluated, Gatorade Protein Recovery Chocolate Shake and Starbucks Doubleshot Energy appear to have cariogenic potential since they increased the biofilm formation and metabolic activity of S. mutans.

Triple Antibiotic Polymer Nanofibers for Intracanal Drug Delivery: Effects on Dual Species Biofilm and Cell Function

INTRODUCTION

Root canal disinfection and the establishment of an intracanal microenvironment conducive to the proliferation/differentiation of stem cells play a significant role in regenerative endodontics. This study was designed to (1) investigate the antimicrobial efficacy of triple antibiotic-containing nanofibers against a dual-species biofilm and (2) evaluate the ability of dental pulp stem cells (DPSCs) to adhere to and proliferate on dentin upon nanofiber exposure.

METHODS

Seven-day-old dual-species biofilm established on dentin specimens was exposed for 3 days to the following: saline (control), antibiotic-free nanofibers (control), and triple antibiotic-containing nanofibers or a saturated triple antibiotic paste (TAP) solution (50 mg/mL in phosphate buffer solution). Bacterial viability was assessed using the LIVE/DEAD assay (Molecular Probes, Inc, Eugene, OR) and confocal laser scanning microscopy. For cytocompatibility studies, dentin specimens after nanofiber or TAP (1 g/mL in phosphate buffer solution) exposure were evaluated for cell adhesion and spreading by actin-phalloidin staining. DPSC proliferation was assessed on days 1, 3, and 7. Statistics were performed, and significance was set at the 5% level.

RESULTS

Confocal laser scanning microscopy showed significant bacterial death upon antibiotic-containing nanofiber exposure, differing significantly (P < .05) from antibiotic-free fibers and the control (saline). DPSCs showed enhanced adhesion/spreading on dentin specimens treated with antibiotic-containing nanofibers when compared with its TAP counterparts. The DPSC proliferation rate was similar on days 1 and 3 in antibiotic-free nanofibers, triple antibiotic-containing nanofibers, and TAP-treated dentin. Proliferation was higher (9-fold) on dentin treated with antibiotic-containing nanofibers on day 7 compared with TAP.

CONCLUSIONS

Triple antibiotic-containing polymer nanofibers led to significant bacterial death, whereas they did not affect DPSC attachment and proliferation on dentin.

Biofilm sensitivity of seven Streptococcus mutans strains to different fluoride levels

The effect of fluoride concentrations in dental products could be different depending on the Streptococcus mutans strain. The aim of this study was to investigate the effect of different fluoride concentrations corresponding to dental products on biofilm formation and metabolic activity of S. mutans strains. Seven S. mutans strains (UA159, A32-2, NG8, 10449, UA130, LM7, and OMZ175) were inoculated into 96-well microtiter plates and were tested with various concentrations of sodium fluoride (0.0, 1.0, 1.56, 3.13, 6.25, 12.5, 25, 50, 100, 125, 175, 225, 275, 625, 1,250, 2,250, and 5,500 ppm) for inhibition of biofilm formation and bacterial metabolic activity by recording absorbance values followed by scanning electron microscope (SEM) images. Data were analyzed by one-way analysis of variance and Tukey’s tests (α = 5%). Significantly more (p≤0.05) biofilm mass in the presence of fluoride was produced by A32-2 and NG8. UA130, LM7, and OMZ175 were more sensitive to increased fluoride and demonstrated few bacterial cells and extracellular polysaccharide (EPS) production at 100 ppm in SEM images. All strains were unable to produce significant biofilm at concentrations >225 ppm. Patients with tolerantS. mutans strains would potentially benefit less from the inherent antibacterial effect of fluoride.

Nicotine Upregulates Coaggregation of Candida albicans and Streptococcus mutans

PURPOSE

Denture stomatitis is a condition of painless inflammation of denture-bearing mucosa. Reports indicate that nicotine, the major psychoactive ingredient in tobacco, increases growth of Streptococcus mutans and Candida albicans in denture biofilm. The purpose of this study was to determine the in vitro effects of nicotine on coaggregation of C. albicans with S. mutans.

MATERIAL AND METHODS

C. albicans strain ATCC 10231, S. mutans strain UA159 (ATTC 700610), and nicotine dilutions (ranging from 0 to 32 mg/ml) were used for this study. Both microorganisms were grown for 24 hours in dilutions of nicotine (0 to 32 mg/ml) made in tryptic soy broth (TSB) or TSB supplemented with 1% sucrose (TSBS; S. mutans) or yeast peptone dextrose broth (YPD; C. albicans). Suspensions of the nicotine-treated cells were prepared, mixed together and incubated for up to 24 hours to determine if there was an increase in coaggregation of nicotine-treated cells compared to the no nicotine control cells. Qualitative analysis of coaggregation was performed using a visual aggregation assay and light microscopic observation. A spectrophotometric assay was used to provide a quantitative analysis of the coaggregation.

RESULTS

The visual aggregation assay indicated a significant increase in coaggregation between C. albicans and S. mutans with increasing incubation time (0 to 24 hours) and nicotine concentrations (0 to 4 mg/ml). Microbial growth in nicotine at 4 mg/ml demonstrated a significant increase in coaggregation after 24 hours of incubation. The numbers of coaggregated S. mutans/C. albicans cells exhibited a significant increase with incubation time and nicotine concentrations when the samples were examined microscopically. More coaggregation of S. mutans and C. albicans was observed with incubation time and increased nicotine compared to the 0 mg/ml nicotine group. There was a noticeable increase of coaggregation when cells were grown in TSBS compared to TSB. Absorbance of nicotine-treated cells (0.25 to 4 mg/ml) exhibited a decrease in values compared to 0 mg/ml at 0 hours of incubation, confirming increased coaggregation.

CONCLUSION

These results demonstrated the effect of nicotine in increasing the coaggregation of S. mutans with C. albicans. Coaggregation increased with incubation time and nicotine concentration. Coaggregation was increased with S. mutans grown in TSBS compared to TSB, suggesting that growth in sucrose media leads to an increase in receptors responsible for coaggregation.

Direct and indirect antibacterial effects of various concentrations of triple antibiotic pastes loaded in a methylcellulose system

We investigated the direct and indirect (residual) antibacterial effects of various concentrations of triple antibiotic paste (TAP) loaded into a methylcellulose system. Enterococcus faecalis (E. faecalis) was grown on sterilized dentin blocks (n = 60) and treated with clinically used TAP (1,000 mg/mL), low concentrations of methylcellulose-based TAP (100, 10, and 1 mg/mL), placebo paste, or 1.5% NaOCl (n = 10). The pastes were then removed, and biofilm disruption assays were performed. Additional dentin blocks (n = 120) were pretreated with the same experimental groups (n = 20). The pastes were rinsed off, and the samples were immersed independently in phosphate-buffered saline for 2 and 4 weeks (n = 10). E.faecalis was then grown on the dentin blocks, and biofilm disruption assays were performed. Fisher's Exact and Wilcoxon rank sum tests were used for statistical analyses. With regard to direct antibacterial effects, all treatment groups demonstrated complete eradication of biofilms in comparison to placebo paste, while 10 mg/mL of TAP or higher provided substantial residual antibacterial effects. However, dentin treated with 1 mg/mL of TAP or 1.5% NaOCl did not provide substantial residual antibacterial effects. Dentin pretreated with 10 mg/mL of TAP or higher exhibited extended residual antibacterial effects and can thus be used during endodontic regeneration.(J Oral Sci 58, 575-582, 2016).

A Case-Control Study to Determine the Prognostic Features of Salivary Epithelial Cells in Periodontitis

Periodontitis-a biofilm-induced immunoinflammatory pathology-often progresses gradually, exhibiting periodic bursts and resolution. Exfoliating oral epithelial cells act as reservoirs for key periodontal pathogens, facilitating reinfection or infection of new sites. Since saliva is a rich source of oral epithelial cells, we hypothesized that the microbial and functional profile of salivary epithelial cells (SECs) will reflect the in situ host response and disease severity. We used a case-control study design. Unstimulated whole saliva was collected from 20 chronic periodontitis patients and 20 healthy controls in accordance with the institutional review board. The isolated SECs were assessed for viability by trypan blue exclusion. Gram-stained SECs were analyzed by ImageJ, and Gram stain index (GSI) per SEC was calculated. Equal numbers of SECs from each sample were exposed to 2 periodontal pathogens- Porphyromonas gingivalis and Fusobacterium nucleatum-in biofilm or planktonic formulations at varying proportions. Cytokines in culture supernatants were assessed by ELISA (enzyme-linked immunosorbent assay). Additionally, soluble Toll-like receptor 2 (sTLR-2)-a pattern recognition receptor capable of binding microbial ligands associated with periodontitis-was measured in clarified saliva by ELISA. An increased number of SECs, a higher GSI/SEC, and a lower sTLR-2 were observed in periodontitis saliva as compared with healthy saliva. SECs from periodontitis saliva secreted higher amounts of interleukin 8 in response to P. gingivalis, and the presence of F. nucleatum dampened the response. Nonsurgical periodontal treatment improved clinical parameters, reduced the number of SECs, decreased GSI/SEC, and increased sTLR-2 in clarified saliva. In conclusion, our data suggest that SECs can provide a phenotypically distinct individualized resource for assessing epithelial response to pathogens in the course of periodontal disease. Furthermore, correlation between the sTLR-2 and GSI/SEC suggests that the expression profile of epithelial and soluble Toll-like receptor could provide an indirect measure of periodontal disease-associated dysbiosis. Knowledge Transfer Statement: The results of this study can be used for prognostic evaluation of chronic periodontitis in response to therapy and provide an opportunity for early identification of poor responders. A chip-based simple test incorporating the identified salivary epithelial cell characteristics can be developed and validated for future clinical applications, especially for monitoring patients with increased susceptibility for refractory and/or recurrent periodontitis.

Novel bioactive tetracycline-containing electrospun polymer fibers as a potential antibacterial dental implant coating

The purpose of this investigation was to determine the ability of tetracycline-containing fibers to inhibit biofilm formation of peri-implantitis-associated pathogens [i.e., Porphyromonas gingivalis (Pg), Fusobacterium nucleatum (Fn), Prevotella intermedia (Pi), and Aggregatibacter actinomycetemcomitans (Aa)]. Tetracycline hydrochloride (TCH) was added to a poly(DL-lactide) [PLA], poly(ε-caprolactone) [PCL], and gelatin [GEL] polymer blend solution at distinct concentrations to obtain the following fibers: PLA:PCL/GEL (TCH-free, control), PLA:PCL/GEL + 5 % TCH, PLA:PCL/GEL + 10 % TCH, and PLA:PCL/GEL + 25 % TCH. The inhibitory effect of TCH-containing fibers on biofilm formation was assessed by colony-forming units (CFU/mL). Qualitative analysis of biofilm inhibition was done via scanning electron microscopy (SEM). Statistical significance was reported at p < 0.05. Complete inhibition of biofilm formation on the fibers was observed in groups containing TCH at 10 and 25 wt%. Fibers containing TCH at 5 wt% demonstrated complete inhibition of Aa biofilm. Even though a marked reduction in CFU/mL was observed with an increase in TCH concentration, Pi proved to be the most resilient microorganism. SEM images revealed the absence of or a notable decrease in bacterial biofilm on the TCH-containing nanofibers. Collectively, our data suggest that tetracycline-containing fibers hold great potential as an antibacterial dental implant coating.

Tetracycline-incorporated polymer nanofibers as a potential dental implant surface modifier

This study investigated the antimicrobial and osteogenic properties of titanium (Ti) disks superficially modified with tetracycline (TCH)-incorporated polymer nanofibers. The experiments were carried out in two phases. The first phase dealt with the synthesis and characterization (i.e., morphology, mechanical strength, drug release, antimicrobial activity, and cytocompatibility) of TCH-incorporated fibers. The second phase was dedicated to evaluating both the antimicrobial and murine-derived osteoprecursor cell (MC3T3-E1) response of Ti-modified with TCH-incorporated fibers. TCH was successfully incorporated into the submicron-sized and cytocompatible fibers. All TCH-incorporated mats presented significant antimicrobial activity against periodontal pathogens. The antimicrobial potential of the TCH-incorporated fibers-modified Ti was influenced by both the TCH concentration and bacteria tested. At days 5 and 7, a significant increase in MC3T3-E1 cell number was observed for TCH-incorporated nanofibers-modified Ti disks when compared to that of TCH-free nanofibers-modified Ti-disks and bare Ti. A significant increase in alkaline phosphatase (ALP) levels on the Ti disks modified with TCH-incorporated nanofiber on days 7 and 14 was seen, suggesting that the proposed surface promotes early osteogenic differentiation. Collectively, the data suggest that TCH-incorporated nanofibers could function as an antimicrobial surface modifier and osteogenic inducer for Ti dental implants. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2085-2092, 2017.

Effect of nicotine on cariogenic virulence of Streptococcus mutans

Nicotine has well-documented effects on the growth and colonization of Streptococcus mutans. This study attempts to investigate the effects of nicotine on pathogenic factors of S. mutans, such as the effect on biofilm formation and viability, expression of pathogenic genes, and metabolites of S. mutans. The results demonstrated that addition of nicotine did not significantly influence the viability of S. mutans cells. The biofilms became increasingly compact as the concentrations of nicotine increased. The expression of virulence genes, such as ldh and phosphotransferase system (PTS)-associated genes, was upregulated, and nlmC was upregulated significantly, while ftf was downregulated. The lactate concentration of S. mutans grown in 1 mg/mL of nicotine was increased up to twofold over either biofilm or planktonic cells grown without nicotine. Changes in the metabolites involved in central carbon metabolism from sucrose indicated that most selected metabolites were detectable and influenced by increased concentrations of nicotine. This study demonstrated that nicotine can influence the pathogenicity of S. mutans and may lead to increased dental caries through the production of more lactate and the upregulation of virulence genes.

Sense of Humor, Childhood Cancer Stressors, and Outcomes of Psychosocial Adjustment, Immune Function, and Infection

The diagnosis, treatment, and side effects of childhood cancer have been described as extremely stressful experiences in the life of a child. Anecdotally, children report that a sense of humor helps them cope with the daily experiences of living with cancer; however, no research has examined sense of humor and childhood cancer stressors. This study investigated the effect of sense of humor on the relationship between cancer stressors and children’s psychosocial adjustment to cancer, immune function, and infection using Lazarus and Folkman’s theory of stress, appraisal, and coping. A direct relationship was observed between sense of humor and psychosocial adjustment to cancer, such that children with a high sense of humor had greater psychological adjustment, regardless of the amount of cancer stressors. A moderating effect was observed for incidence of infection. As childhood cancer stressors increase, children with high coping humor scores reported fewer incidences of infection than low scorers.