Antibacterial, chemical and physical properties of sealants with polyhexamethylene guanidine hydrochloride

Influence of incorporation of nanostructured silver vanadate decorated with silver nanoparticles on roughness, microhardness, and color change of pit and fissure sealants

Objective

The aim of this study was to evaluate the roughness, hardness, and color change of pit and fissure sealants of two commercial brands (Fluroshield ™ and Ultraseal XT ™) incorporated with nanostructured silver vanadate nanomaterial decorated with silver nanoparticles (β-AgVO3) in concentrations (0% - control, 2.5% and 5%).

Material and methods

Two commercial brands Fluroshield TM and Ultraseal XT ™ were used to make the samples with dimensions of 6 × 6 × 4 mm. The control group was made according to the manufacturer's instructions and in the groups with the addition of β-AgVO3, the nanomaterial was added proportionally by mass at percentages of 2.5% and 5%. Roughness properties were evaluated using a 3D Laser Confocal Microscope (n = 10), Knoop microhardness by Microdurometer (n = 10), and color change by Portable Color Spectrophotometer on the CIEDE2000 system (n = 10). Data were evaluated by one-way ANOVA with Bonferroni adjustment and Tukey's mean comparison test at a 5% significance level.

Results

Ultraseal XT ™ sealant roughness showed a significant difference between concentrations with the highest mean for the 5% group (P = 0.010). Regarding the hardness, both sealants showed no significant difference between the groups. Fluroshield ™ sealant showed a significant difference in ΔE00 between the control-2.5% 24.93 (3.49) and control-5% 28.41 (2.58).

Conclusion

It may be concluded that the incorporation of β-AgVO3 influenced the increase in roughness for Ultraseal XT ™ pit and fissure sealant, did not interfere with the microhardness of both sealants, and promoted a change in the color of Fluroshield ™ sealant within clinically acceptable limits.

Antimicrobial effect and the mechanical and surface properties of a self-disinfecting and a chlorhexidine-incorporated Type IV dental stone

STATEMENT OF PROBLEM

Stone casts are subject to contamination, but whether disinfectants incorporated into the stone are effective is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the antimicrobial activity and the mechanical and surface properties of self-disinfecting gypsum (SDG) and gypsum mixed with 2% chlorhexidine (GCHX).

MATERIAL AND METHODS

Antimicrobial action was evaluated using the diffusion-disk technique on Streptococcus aureus and Candida albicans 1 hour and 24 hours after pouring the gypsum. The groups were SDG, GCHX, a positive control (PC) of gypsum mixed with distilled water, and a negative control (NC) of filter paper disk soaked with 2% chlorhexidine; n=8. Inhibition halos were measured using the ImageJ software program and statistically analyzed using the repeated measures mixed ANOVA with time×group interaction. Compressive strength (CS) in MPa and surface roughness (SR) in μm (parameters: Ra - roughness average; and Sa - 3-dimensional (3D) arithmetic mean of the surface profile) tests were performed to characterize the specimens (evaluated groups: SDG, GCHX, and PC; n=10). CS data were analyzed by a 2-way ANOVA with time×group interaction, and SR data by a 1-way ANOVA (α=.05).

RESULTS

For S aureus, there were differences between GCHX and SDG at 1 hour and 24 hours (P<.05), but no significant differences were found for C albicans (P>.05). GCHX was better than PC, except for C albicans, and showed a reduction in CS when compared with PC and SDG (P<.05) at all time intervals. The SR of GCHX increased (Ra:1.76, Sa:2.08) when compared with PC (Ra:0.89, Sa:1.12) and SDG (Ra:1.03, Sa:1.35) (Ra: P<.004 and Sa: P<.001).

CONCLUSIONS

The antimicrobial activity of GCHX against S aureus was better than that of SDG, but neither had an effect against C albicans. As for CS and SR, GCHX presented a decrease in properties when compared with PC and SDG but was within the American Dental Association #25 specification values.

Physicochemical and biological properties of experimental dental adhesives doped with a guanidine-based polymer: an in vitro study

OBJECTIVES

The objective of this study is to formulate experimental dental adhesives with different polyhexamethylene guanidine hydrochloride concentrations (PHMGH) and evaluate their physical, chemical, and biological properties.

MATERIALS AND METHODS

The experimental adhesives were formulated with 0 (control, G_CTRL), 0.5 (G_0.5%), 1 (G_1%), or 2 (G_2%) wt.% into the adhesive. The adhesives were analyzed for degree of conversion (DC%), softening in solvent (ΔKHN%), ultimate tensile strength (UTS), microtensile bond strength (μTBS) immediately and after 1 year of aging, antibacterial activity, and cytotoxicity.

RESULTS

There were no differences among groups for DC%, ΔKHN%, and UTS (p > 0.05%). There were no differences between each PHMGH-doped adhesive compared to G_CTRL in the immediate μ-TBS (p > 0.05). Adhesives with at least 1 wt.% of PHMGH presented better stability of μ-TBS. PHMGH-doped adhesives showed improved longitudinal μ-TBS compared to G_CTRL (p < 0.05). Lower Streptococcus mutans biofilm formation was observed for PHMGH-doped adhesives (p < 0.05). There was lower viability of planktonic S. mutans in the media in contact with the samples when at least 1 wt.% of PHGMGH was incorporated (p < 0.05). The formulated adhesives showed no cytotoxicity against pulp cells (p > 0.05).

CONCLUSIONS

The adhesive with 2 wt.% of PHMGH showed the highest antibacterial activity, without affecting the physicochemical properties and cytotoxicity, besides conferring stability for the dental adhesion.

CLINICAL RELEVANCE

PHMGH, a positively charged polymer, conveyed antibacterial activity to dental adhesives. Furthermore, it did not negatively affect the essential physicochemical and biocompatibility properties of the adhesives. More importantly, the incorporation of PHMGH provided stability for the μ-TBS compared to the control group without this additive.

Physicochemical and biological evaluation of a triazine-methacrylate monomer into a dental resin

OBJECTIVES

This study aimed to (1) formulate blend resins with 2.5 or 5 wt.% of the methacrylate monomer 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAT), and (2) to evaluate the blend resins regarding the physicochemical and biological properties.

METHODS

The base resin was formulated mixing 60 wt.% of bisphenol A glycol dimethacrylate and 40 wt.% of triethylene glycol dimethacrylate with photoinitiator/co/initiator system. TAT was added at 2.5 (G_2.5%) or 5 (G_5%) wt.%, and a group without TAT was used as control (G_ctrl). The resins were analyzed for degree of conversion (DC), Knoop hardness (KHN), softening in solvent (ΔKHN), ultimate tensile strength (UTS), contact angle, surface free energy (SFE), antibacterial activity against Streptococcus mutans biofilm formation, and cytotoxicity against human keratinocytes.

RESULTS

There was no difference for the DC (p = 0.676). The addition of TAT at 5 wt.% induced higher KHN (p<0.001), higher resistance against softening in solvent (p<0.001), and higher UTS (p = 0.04). There were no statistically significant differences for contact angle with water (p = 0.106), α-bromonaphtalene (p = 0.454), and SFE (p = 0.172). The higher the TAT concentration, the higher the antibacterial activity (p<0.001). G_2.5% showed no cytotoxicity compared to G_ctrl (p>0.05), and G_5% induced lower cell viability (p<0.05).

CONCLUSIONS

The addition of 2.5 wt.% of TAT is suitable for conveying antibacterial activity for dental resins without changing the physicochemical properties or impairing the cytotoxic effect.

CLINICAL RELEVANCE

Methacrylate monomers that decrease bacterial viability and copolymerize with the resin matrix are exciting approaches to developing therapeutic materials. TAT showed promising properties to may hamper and prevent carious lesions when incorporated into dental materials. Further evaluations with higher cariogenic challenges will be carried to analyze the formulated materials.

Evaluation of Antibacterial Effects of Fissure Sealants Containing Chitosan Nanoparticles

Objectives

The present study evaluated the antimicrobial effects of fissure sealants containing chitosan nanoparticles.

Materials and Methods

Antibacterial effect of Master Dent fissure sealant alone and after incorporating chitosan nanoparticles was evaluated on Streptococcus mutans, sanguis, and Lactobacillus acidophilus. Biofilm growth was evaluated by determining colony counts. Antimicrobial effect was determined on days 3, 15, and 30 by counting microbial colonies using eluted components test. One-way ANOVA, Tukey HSD tests, t test, and two-way ANOVA were used for statistical analyses (α = 0.05).

Results

Biofilm inhibition test showed that fissure sealant containing 1 wt.% chitosan decreased colony counts significantly (P < 0.05). Eluted components test with S. mutans and sanguis showed significant decrease in colony counts during the first 15 days in chitosan containing group; however, from day 30, antimicrobial activity decreased noticeably, with no significant difference from control group (P > 0.05). Antimicrobial activity against L. acidophilus was maintained in chitosan group up to 30 days, and decrease in colony counts was significant (P < 0.05).

Conclusion

According to the results of this study, incorporation of 1 wt.% chitosan into fissure sealant induced an antimicrobial activity. Antibacterial effect on L. acidophilus persisted for longer time (30 days) compared to the two other bacterial species (15 days).

Comparison of Two Types of Pit and Fissure Sealants in Reducing the Incidence of Dental Caries Using a Split-Mouth Design

Objectives

To evaluate the effectiveness of two pit and fissure sealants (PFS) in reducing the incidence of dental caries in schoolchildren.

Material and Methods

A randomized split-mouth experimental design was used in a sample of 140 subjects assigned to two groups. The sealants used were Clinpro©3M and BeautiSealant©Shofu placed in first permanent molars (FPMs). Each sealant was compared to molars in the controls to determine effectiveness over a period of 6 months. The study had a 12.9% loss to follow-up. No statistically significant differences (p>0.05) were observed for sex, age, baseline dmft, or type of sealants. Nonparametric tests were used for statistical analysis.

Results

Average dmft index at baseline was 4.10±3.16. Lower incidence of caries was observed in FPMs with pit and fissure sealants (p<0.01), regardless of the type used. When sealants remained intact there was a lower caries incidence compared to sealants partially or completely missing – but differences were only significant for FPM 16. Caries incidence was higher for BeautiSealant sealed teeth than for Clinpro’s, but only statistically significant in FPMs 16, 36 and 46 (p< 0.05). Caries incidence was higher in those cases with a higher baseline dmft but it only reached statistical significance in FPMs 26 and 36. Relative risks for dental caries were lower in sealed teeth (p<0.01).

Conclusions

Pit and fissures sealants are an effective preventive treatment to reduce caries during a 6-month follow-up in schoolchildren 6 to 8 years of age, regardless of the type of sealant used. The sealant brand that showed greater effectiveness in terms of prevention and retention was Clinpro©3M.

Antimicrobial Polymer-Based Assemblies: A Review

An antimicrobial supramolecular assembly (ASA) is conspicuous in biomedical applications. Among the alternatives to overcome microbial resistance to antibiotics and drugs, ASAs, including antimicrobial peptides (AMPs) and polymers (APs), provide formulations with optimal antimicrobial activity and acceptable toxicity. AMPs and APs have been delivered by a variety of carriers such as nanoparticles, coatings, multilayers, hydrogels, liposomes, nanodisks, lyotropic lipid phases, nanostructured lipid carriers, etc. They have similar mechanisms of action involving adsorption to the cell wall, penetration across the cell membrane, and microbe lysis. APs, however, offer the advantage of cheap synthetic procedures, chemical stability, and improved adsorption (due to multipoint attachment to microbes), as compared to the expensive synthetic routes, poor yield, and subpar in vivo stability seen in AMPs. We review recent advances in polymer-based antimicrobial assemblies involving AMPs and APs.

Guanidine derivative inhibits C. albicans biofilm growth on denture liner without promote loss of materials' resistance

To reduce the burden of denture stomatitis and oral candidiasis, an aqueous solution containing polyhexamethylene guanidine hydrochloride (PHMGH) was investigated as an antifungal disinfectant against the leading cause of these oral conditions, Candida albicans. The solutions formulated with concentrations ranging from 0.125 to 0.50 wt% enabled increasing disinfection at the initial 5min-contact with 72h-mature candida biofilms formed on denture liner specimens. After 10 min-contact, the solution at lower concentration has reached total fungal elimination. The results also indicated that the denture liners preserved their mechanical property after the maximum contact time with the solution at the highest tested concentration. The PHMGH aqueous solutions at 0.125 wt% could be applied to promote interim denture liner disinfection without promoting the loss of materials' mechanical property.

Myristyltrimethylammonium Bromide (MYTAB) as a Cationic Surface Agent to Inhibit Streptococcus mutans Grown over Dental Resins: An In Vitro Study

This in vitro study evaluated the effect of myristyltrimethylammonium bromide (MYTAB) on the physical, chemical, and biological properties of an experimental dental resin. The resin was formulated with dental dimetacrylate monomers and a photoinitiator/co-initiator system. MYTAB was added at 0.5 (G_0.5%), 1 (G_1%), and 2 (G_2%) wt %, and one group remained without MYTAB and was used as the control (G_Ctrl). The resins were analyzed for the polymerization kinetics, degree of conversion, ultimate tensile strength (UTS), antibacterial activity against Streptococcus mutans, and cytotoxicity against human keratinocytes. Changes in the polymerization kinetics profiling were observed, and the degree of conversion ranged from 57.36% (±2.50%) for G_2% to 61.88% (±1.91%) for G_0.5%, without a statistically significant difference among groups (p > 0.05). The UTS values ranged from 32.85 (±6.08) MPa for G_0.5% to 35.12 (±5.74) MPa for G_Ctrl (p > 0.05). MYTAB groups showed antibacterial activity against biofilm formation from 0.5 wt % (p < 0.05) and against planktonic bacteria from 1 wt % (p < 0.05). The higher the MYTAB concentration, the higher the cytotoxic effect, without differences between G_Ctrl e G_0.5% (p > 0.05). In conclusion, the addition of 0.5 wt % of MYTAB did not alter the physical and chemical properties of the dental resin and provided antibacterial activity without cytotoxic effect.

Ionic liquid as antibacterial agent for an experimental orthodontic adhesive

OBJECTIVE

The aim of this study was to formulate and evaluate experimental orthodontic adhesives with different concentrations of 1-n-butyl-3-methylimidazoilium bis(trifluoromethanesulfonyl)imide (BMIM.NTf₂).

METHODS

The experimental orthodontic adhesives were formulated with methacrylate monomers, photoinitiators and silica colloidal. The ionic liquid BMIM.NTf₂ was synthesized and characterized. BMIM.NTf₂ was added at 5 (G_5%), 10 (G_10%) and 15 (G_15%) wt.%. One group contained no BMIM.NTf₂ to function as control (G_Ctrl). The adhesives were evaluated for polymerization kinetics, degree of conversion (DC), Knoop hardness and softening in solvent, ultimate tensile strength (UTS), shear bond strength (SBS), thermogravimetric analysis (TGA), antibacterial activity and cytotoxicity.

RESULTS

BMI.NTf₂ showed the characteristic chemical peaks. The polymerization kinetics were different among the groups. G_10% and G_15% showed higher DC (p < 0.05). G_5% and G_Ctrl had no differences for softening in solvent (p > 0.05). There were no differences for UTS (p > 0.05) and SBS (p > 0.05). TGA showed one different peak for G_15%. All groups with BMIM.NTf₂ showed antibacterial activity compared to G_Ctrl (p < 0.05) without cytotoxicity (p > 0.05).

SIGNIFICANCE

To reduce biofilm formation around brackets and to prevent demineralization at susceptible sites, materials have been developed with antibacterial properties. In this study, a new experimental orthodontic adhesive was formulated with an imidazolium ionic liquid (BMIM.NTf₂) as antibacterial agent. The incorporation of 5 wt.% of ionic liquid decreased biofilm formation without affecting the physico-chemical properties and cytotoxicity of an experimental orthodontic resin.