Publications by authors named "Isadora Martini Garcia"

32 Publications

The golden proportion concept: smile makeover with an 18-month follow-up.

Int J Esthet Dent 2021 05;16(2):216-230

Department of Esthetic and Restorative Dentistry, School of Dentistry, Universidad Científica del Sur, Lima, Peru

Aim: The altered size, shape or position of the teeth affect their proper alignment, the harmony of the smile, and the dentofacial composition. The aim of this article is to describe a minimally invasive approach to improve the esthetics of a patient through the golden proportion (GP) concept with the use of direct composite resin stratification.

Materials And Methods: A 26-year-old female complained about the appearance of her smile due to the existing spaces between her anterior teeth; her small, peg-shaped lateral incisors; the wear of her canines; and the color of her teeth. The clinical examination confirmed diastemas in the anterior teeth, peg-shaped maxillary lateral incisors, and incisal wear of the canines. Treatment with dental whitening followed by composite restorations was performed in line with the current conservative approach in dentistry. The patient was followed up for 18 months.

Conclusion: The use of the additive technique with composite for the closure of diastemas under the GP concept illustrates an example of viable management to restore esthetic harmony through a minimally invasive approach, with reliability over time and the advantages of being less laborious, less time consuming, and less expensive than other approaches. The treatment plan was acceptable to the patient.
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May 2021

Physicochemical properties and biological effects of quaternary ammonium methacrylates in an experimental adhesive resin for bonding orthodontic brackets.

J Appl Oral Sci 2021 3;29:e20201031. Epub 2021 May 3.

Universidade Federal do Rio Grande, Pós-Graduação em Odontologia da do Sul, Porto Alegre, RS, Brasil.

Methodology: Fixed orthodontic appliances may lead to biofilm accumulation around them that may increase caries risk. This study aimed to evaluate the influence of quaternary ammonium methacrylates (QAMs) on the physicochemical properties, cytotoxicity, and antibacterial activity of adhesive resins for orthodontic purposes. A base resin was prepared with a comonomer blend and photoinitiator/co-initiator system. Two different QAMs were added to the base adhesive: dimethylaminododecyl methacrylate at 5 wt.% (DMADDM) or dimethylaminohexadecyl methacrylate (DMAHDM) at 10 wt.%. The base adhesive, without QAMs, (GC) and the commercial Transbond™ XT Primer 3M (GT) were used as control. The resins were tested immediately and after six months of aging in the water regarding the antibacterial activity and shear bond strength (SBS). The antibacterial activity was tested against Streptococcus mutans via metabolic activity assay (MTT test). The groups were also tested for the degree of conversion (DC) and cytotoxicity against keratinocytes.

Results: The resins containing QAM showed antibacterial activity compared to the commercial material by immediately reducing the metabolic activity by about 60%. However, the antibacterial activity decreased after aging (p<0.05). None of the groups presented any differences for SBS (p>0.05) and DC (p>0.05). The incorporation of DMADDM and DMAHDM significantly reduced the keratinocyte viability compared to the GT and GC groups (p<0.05).

Conclusion: Both adhesives with QAMs showed a significant reduction in bacterial metabolic activity, but this effect decreased after water aging. Lower cell viability was observed for the group with the longer alkyl chain-QAM, without significant differences for the bonding ability and degree of conversion. The addition of QAMs in adhesives may affect the keratinocytes viability, and the aging effects maybe decrease the bacterial activity of QAM-doped materials.
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http://dx.doi.org/10.1590/1678-7757-2020-1031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8092807PMC
May 2021

Ionic liquid-loaded microcapsules doped into dental resin infiltrants.

Bioact Mater 2021 Sep 12;6(9):2667-2675. Epub 2021 Feb 12.

Department of Dental Materials, School of Dentistry, Federal University of Rio Grande do Sul, Ramiro Barcelos Street, 2492, Rio Branco, 90035-003, Porto Alegre, RS, Brazil.

Resin infiltrants have been effectively applied in dentistry to manage non-cavitated carious lesions in proximal dental surfaces. However, the common formulations are composed of inert methacrylate monomers. In this study, we developed a novel resin infiltrant with microcapsules loaded with an ionic liquid (MC-IL), and analyzed the physical properties and cytotoxicity of the dental resin. First, the ionic liquid 1--butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI.NTf) was synthesized. BMI.NTf has previously shown antibacterial activity in a dental resin. Then, MC-IL were synthesized by the deposition of a preformed polymer. The MC-IL were analyzed for particle size and de-agglomeration effect via laser diffraction analysis and shape via scanning electron microscopy (SEM). The infiltrants were formulated, and the MC-IL were incorporated at 2.5%, 5%, and 10 wt%. A group without MC-IL was used as a control. The infiltrants were evaluated for ultimate tensile strength (UTS), contact angle, surface free energy (SFE), and cytotoxicity. The MC-IL showed a mean particle size of 1.64 (±0.08) μm, shriveled aspect, and a de-agglomeration profile suggestive of nanoparticles' presence in the synthesized powder. There were no differences in UTS among groups (p > 0.05). The incorporation of 10 wt% of MC-IL increased the contact angle (p < 0.05), while the addition from 5 wt% reduced the SFE in comparison to the control group (p < 0.05). The human cell viability was above 90% for all groups (p > 0.05). The incorporation of microcapsules as a drug-delivery system for ionic liquids may be a promising strategy to improve dental restorative materials.
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http://dx.doi.org/10.1016/j.bioactmat.2021.02.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7895677PMC
September 2021

The Antibacterial Effects of Resin-Based Dental Sealants: A Systematic Review of In Vitro Studies.

Materials (Basel) 2021 Jan 15;14(2). Epub 2021 Jan 15.

Department of Preventive Dental Sciences, College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam 34212, Saudi Arabia.

This review aimed to assess the antimicrobial effects of different antibacterial agents/compounds incorporated in resin-based dental sealants. Four databases (PubMed, MEDLINE, Web of Science and Scopus) were searched. From the 8052 records retrieved, 275 records were considered eligible for full-text screening. Nineteen studies met the inclusion criteria. Data extraction and quality assessment was performed by two independent reviewers. Six of the nineteen included studies were judged to have low risk of bias, and the rest had medium risk of bias. Compounds and particles such as zinc, tin, Selenium, chitosan, chlorhexidine, fluoride and methyl methacrylate were found to be effective in reducing the colony-forming unit counts, producing inhibition zones, reducing the optical density, reducing the metabolic activities, reducing the lactic acid and polysaccharide production and neutralizing the pH when they are added to the resin-based dental sealants. In addition, some studies showed that the antibacterial effect was not significantly different after 2 weeks, 2 months and 6 months aging in distilled water or phosphate-buffered saline. In conclusion, studies have confirmed the effectiveness of adding antibacterial agents/compounds to dental sealants. However, we should consider that these results are based on laboratory studies with a high degree of heterogeneity.
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http://dx.doi.org/10.3390/ma14020413DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7830019PMC
January 2021

Antibacterial response of oral microcosm biofilm to nano-zinc oxide in adhesive resin.

Dent Mater 2021 03 17;37(3):e182-e193. Epub 2020 Dec 17.

Ph.D. Program in Dental Biomedical Sciences, University of Maryland School of Dentistry, Baltimore, MD 21201, USA; Operative Dentistry Division, General Dentistry Department University of Maryland School of Dentistry, Baltimore, MD 21201, USA. Electronic address:

Objective: Various nanoparticles are currently under investigation to impart biointeractivity for dental materials. This study aimed to: (1) formulate an experimental dental adhesive containing ZnO nanoparticles; (2) evaluate its chemical and mechanical properties; and (3) assess the antibacterial response against oral microcosm biofilm.

Methods: Nanosized ZnO was chemically and morphologically evaluated. ZnO was incorporated at 0 (G), 2.5 (G), 5 (G) and 7.5 (G) wt.% in an experimental dental adhesive. The adhesives were evaluated for the degree of conversion (DC), flexural strength (FS), and elastic modulus (E). The antibacterial activity was evaluated using a 48h-microcosm biofilm model after the formation of acquired pellicle on samples' surfaces. Colony-forming units (CFU), metabolic activity, and live/dead staining were assessed.

Results: Nanosized ZnO presented characteristic peaks of Zn-O bonds, and the particles were arranged in agglomerates. The DC ranged from 62.21 (±1.05) % for G to 46.15 (±1.23) % for G (p<0.05). G showed lower FS compared to all groups (p<0.05). Despite achieving higher E (p<0.05), G did not show differences for G regarding the FS (p>0.05). G had lower CFU/mL compared to G for mutans streptococci (p<0.05) and total microorganisms (p<0.05), besides presenting lower metabolic activity (p<0.05) and higher dead bacteria via biofilm staining.

Significance: The dental adhesives' physicochemical properties were similar to commercial adhesives and in compliance with ISO recommendations. G restricted the growth of oral microcosm biofilm without impairing the physicochemical performance.
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http://dx.doi.org/10.1016/j.dental.2020.11.022DOI Listing
March 2021

Incorporation of amoxicillin-loaded microspheres in mineral trioxide aggregate cement: an study.

Restor Dent Endod 2020 Nov 7;45(4):e50. Epub 2020 Oct 7.

Department of Dental Materials, School of Dentistry, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.

Objectives: In this study, we investigated the potential of amoxicillin-loaded polymeric microspheres to be delivered to tooth root infection sites via a bioactive reparative cement.

Materials And Methods: Amoxicillin-loaded microspheres were synthesized by a spray-dray method and incorporated at 2.5% and 5% into a mineral trioxide aggregate cement clinically used to induce a mineralized barrier at the root tip of young permanent teeth with incomplete root development and necrotic pulp. The formulations were modified in liquid:powder ratios and in composition by the microspheres. The optimized formulations were evaluated for physical and mechanical eligibility. The morphology of microspheres was observed under scanning electron microscopy.

Results: The optimized cement formulation containing microspheres at 5% exhibited a delayed-release response and maintained its fundamental functional properties. When mixed with amoxicillin-loaded microspheres, the setting times of both test materials significantly increased. The diametral tensile strength of cement containing microspheres at 5% was similar to control. However, phytic acid had no effect on this outcome ( > 0.05). When mixed with modified liquid:powder ratio, the setting time was significantly longer than that original liquid:powder ratio ( < 0.05).

Conclusions: Lack of optimal concentrations of antibiotics at anatomical sites of the dental tissues is a hallmark of recurrent endodontic infections. Therefore, targeting the controlled release of broad-spectrum antibiotics may improve the therapeutic outcomes of current treatments. Overall, these results indicate that the carry of amoxicillin by microspheres could provide an alternative strategy for the local delivery of antibiotics for the management of tooth infections.
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http://dx.doi.org/10.5395/rde.2020.45.e50DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7691264PMC
November 2020

Silane content influences physicochemical properties in nanostructured model composites.

Dent Mater 2021 02 24;37(2):e85-e93. Epub 2020 Nov 24.

Dental Materials Laboratory, School of Dentistry, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.

Objective: To determine the effect of organosilane content on the physicochemical properties of model composites formulated with nano-sized fillers.

Methods: Model composites were formulated with dimethacrylate-based monomers, a photoinitiator/co-initiator system and silicon dioxide nano-sized fillers treated with different amounts of 3-methacryloxypropyltrimethoxysilane (MPTS): 1.0 (G), 2.0 (G), 5.0 (G), 7.5 (G) and 10 (G) wt.% relative to SiO. Non-silanized fillers (G) were used in the control group. Degree of conversion (DC) was assessed by Fourier-transformed infrared spectroscopy (ATR-FTIR). Knoop hardness (KHN) and elastic modulus were determined before and after water storage for 4 months. Water sorption (Wsp) and solubility (Wsl) were calculated by successive mass determinations in analytical balance. Surface gloss and roughness were characterized before and after toothbrushing simulation.

Results: With the exception of those fillers treated with 1% MPTS, DC was not dependent on the silane content. Within the silanized groups, G showed the lowest initial and final KHN, without statistical difference from G. The elastic modulus was not affected by the silane content, regardless of the storage condition, but those groups formulated with at least 5% silane presented improved values after storage. Silane content did not affect the WSl, but affected Wsp, in which those groups formulated with at least 2 wt.% of MPTS produced a more resistant material than G. The use of treated particles with at least 2 wt.% of silane was able to produce materials that did not change their gloss after the brushing process. Additionally, these materials presented lower surface roughness than G after the brushing process (p < 0.05).

Significance: The concentration of MPTS affected the physicochemical properties of nano-filled composites. Therefore, 2 wt.% of silane was the optimized quantity to produce materials resistant to degradation, both in bulk and surface properties.
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http://dx.doi.org/10.1016/j.dental.2020.10.022DOI Listing
February 2021

Zinc-based particle with ionic liquid as a hybrid filler for dental adhesive resin.

J Dent 2020 11 17;102:103477. Epub 2020 Sep 17.

Department of Dental Materials, School of Dentistry, Federal University of Rio Grande do Sul, Ramiro Barcelos Street, 2492, Rio Branco, 90035-003, Porto Alegre, RS, Brazil. Electronic address:

Objectives: The aim of this study was to evaluate the effect of a zinc-based particle with ionic liquid as filler for an experimental adhesive resin.

Methods: The ionic liquid 1-n-butyl-3-methylimidazolium chloride (BMI.Cl) and zinc chloride (ZnCl) were used to synthesize 1-n-butyl-3-methylimidazolium trichlorozincate (BMI.ZnCl), which was hydrolyzed under basic conditions to produce the simonkolleite (SKT) particles. SKT was analyzed by scanning electron microscopy and transmission electron microscopy. An experimental adhesive resin was formulated and SKT was incorporated at 1, 2.5, or 5 wt.% in the adhesive. One group without SKT was a control group. The antibacterial activity against Streptococcus mutans, cytotoxicity, degree of conversion (DC), ultimate tensile strength (UTS), softening in solvent, and microtensile bond strength (μ-TBS) were investigated.

Results: SKT prepared from the ionic liquid BMI.ZnCl presented a hexagonal shape in the micrometer scale. SKT addition provided antibacterial activity against biofilm formation of S.mutans and planktonic bacteria (p < 0.05). There were no differences in pulp cells' viability (p > 0.05). The DC ranged from 62.18 (±0.83)% for control group to 64.44 (±1.55)% for 2.5 wt.% (p > 0.05). There was no statistically significant difference among groups for UTS (p > 0.05), softening in solvent (p > 0.05), and 24 h or 6 months μ-TBS (p > 0.05).

Conclusions: The physicochemical properties of adhesives were not affected by SKT incorporation, and the filler provided antibacterial activity against S. mutans without changes in the pulp cells' viability. This hybrid zinc-based particle with ionic liquid coating may be a promising filler to improve dental restorations.

Clinical Relevance: A filler based on a zinc-derived material coated with ionic liquid was synthesized and added in dental adhesives, showing antibacterial activity and maintaining the other properties analyzed. SKT may be a promising filler to decrease the biofilm formation around resin-based restorative materials.
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http://dx.doi.org/10.1016/j.jdent.2020.103477DOI Listing
November 2020

Wollastonite as filler of an experimental dental adhesive.

J Dent 2020 11 12;102:103472. Epub 2020 Sep 12.

Department of Dental Materials, School of Dentistry, Federal University of Rio Grande do Sul. Ramiro Barcelos Street, 2492, Rio Branco, 90035-003, Porto Alegre, RS, Brazil. Electronic address:

Objective: The aim of this study was to formulate experimental dental adhesives with wollastonite and evaluate the physical, chemical, and bioactivity properties of the resins.

Methods: Wollastonite was characterized by Fourier transform infrared spectroscopy, X-ray and laser diffraction analyses, and scanning electronic microscopy. An experimental adhesive resin was formulated, and wollastonite was used as filler at 0 (control group), 0.5, 1, or 2 wt.%. Radiopacity, degree of conversion (DC%), microhardness, softening in solvent, ultimate tensile strength (UTS), 24 h- and 1 year- microtensile bond strength (μTBS), mineral deposition, and color of the adhesives were evaluated.

Results: Wollastonite particles showed a needle-like shape, a mean diameter of 70 (± 30) μm, characteristic chemical peaks, and pure crystalline β-CaSiO phase. There were no significant differences (p > 0.05) for radiopacity, softening in solvent, and color change. The group with 2 wt.% of wollastonite showed higher microhardness and UTS in comparison to the control group (p < 0.05). After one year, the control group showed reduced μTBS compared to the immediate value (p < 0.05). The groups with wollastonite presented stable μTBS after one year in comparison to the immediate μTBS (p > 0.05). Wollastonite induced mineral deposition on the adhesive surface over the time of storage in simulated body fluid.

Conclusion: The addition of wollastonite improved the mechanical behavior of the adhesive without changing the analyzed chemical properties. The adhesives with this filler presented mineral deposition and acceptable clinical color. Moreover, dentin treated with wollastonite-doped adhesives showed higher bonding stability after one year of aging.

Clinical Significance: Wollastonite, a silicate-based material, provided bioactivity for the adhesives, which assists in producing therapeutic tooth-restoration interfaces. Moreover, the incorporation of this mineral improOfiller to improve the biological properties of adhesives and assist in dentin-restoration stability.
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http://dx.doi.org/10.1016/j.jdent.2020.103472DOI Listing
November 2020

Assessment of surface roughness changes on orthodontic acrylic resins by all-in-one spray disinfectant solutions.

J Dent Res Dent Clin Dent Prospects 2020 17;14(2):77-82. Epub 2020 Jun 17.

Ph.D. Program in Dental Biomedical Sciences, University of Maryland School of Dentistry, Baltimore, MD 21201, USA.

The disinfection of orthodontic acrylic resins might change the physical and mechanical properties of these materials. We aimed to investigate the impact of four different commercially available disinfectants on the surface roughness of acrylic resins used for orthodontic appliances. Four disinfectant solutions (BirexSE, Opti-Cide3, COEfect MinuteSpray, and CaviCide Spray) were used to disinfect orthodontic acrylic resins using the spraying method. The resins were subjected to repeated disinfection protocols. Distilled water, also applied via spraying method, was used as a control. Surface roughness was scrutinized to examine the extent of surface topography changes by stylus profilometry. Data normality was evaluated via the Shapiro-Wilk test, followed by the Wilcoxon Signed-Rank test for non-parametric data or paired Student's t-test for parametric data to compare intra-group differences in roughness before and after the use of the disinfectant solutions. Some of the disinfectants (BirexSE and CaviCide) resulted in significant changes in surface roughness values before and after the disinfection compared to the controls (P<0.05). The groups that were in contact with distilled water, Opti-Cide, and Coeffect did not exhibit significant differences in surface roughness before and after the intervention (P>0.05). However, from a clinical perspective, the resulting variations in surface roughness (<%0.15) induced by these solutions might not reflect clinically significant differences. The use of disinfectant solutions is unlikely to harm the surface of orthodontic acrylic resins. Oral care providers need to be attentive to the interpretation and implementation of clinically significant changes in their evidence-based approach regarding potential material damages by disinfection sprays.
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http://dx.doi.org/10.34172/joddd.2020.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7464227PMC
June 2020

Quantum chemistry study of the interaction between ionic liquid-functionalized TiO quantum dots and methacrylate resin: Implications for dental materials.

Biophys Chem 2020 10 24;265:106435. Epub 2020 Jul 24.

Dental Materials Laboratory, School of Dentistry, Federal University of Rio Grande do Sul, Ramiro Barcelos, 2492, Rio Branco, 90035-003, Porto Alegre, RS, Brazil. Electronic address:

Quantum Chemistry calculations within the density functional Theory (DFT) are a powerful feature to obtain the atomistic and molecular properties of macromolecules such as polymers and nanoparticles. DFT calculations are essential to understand the stability of new composite materials. In this work, DFT with the Local Density Approximation (LDA) and norm-conserving pseudopotentials is used to analyze the energetic stability as well the electronic properties when titanium dioxide quantum dots (TiO) are added to an adhesive resin (methacrylate - HEMA - and dimethacrylate - BisGMA - monomers), which presents reliable physical, chemical, and biological properties in dentistry. The ionic liquid 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF) was previously used to functionalize the quantum dots, forming the complex system TiOQDs/BMI.BF. DFT provides the most stable configuration through binding energies and bond distances analysis. Our results show that van der Waals interactions between BisGMA and HEMA may contribute to the stabilization of the interaction between the resin and TiOQDs/BMI.BF. Furthermore, according to experimental results, the calculations show that the presence of the ionic liquid increases the quantum dots and resin interactions (binding energies), suggesting that the ionic liquid is important to stabilize the TiOQDs/BMI.BF-resin composite.
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http://dx.doi.org/10.1016/j.bpc.2020.106435DOI Listing
October 2020

Chemical, Mechanical and Biological Properties of an Adhesive Resin with Alkyl Trimethyl Ammonium Bromide-loaded Halloysite Nanotubes.

J Adhes Dent 2020 ;22(4):399-407

Purpose: The aim of this study was to evaluate the chemomechanical properties, antibacterial activity, and cytotoxicity of an experimental adhesive resin containing halloysite nanotubes (HNT), doped with alkyl trimethyl ammonium bromide (ATAB).

Materials And Methods: A filler of HNT doped with ATAB was obtained (ATAB:HNT) and incorporated (5 wt%) into a resin blend made of bisphenol A glycerolate dimethacrylate, 2-hydroxyethyl methacrylate and a photoinitiator/co-initiator system (GATAB:HNT). The same resin blend without ATAB:HNT was used as control (Ctrl). The ATAB:HNT filler was assessed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The two tested adhesives were evaluated for degree of conversion (DC) in vitro and in situ, softening in alcohol, dentin microtensile bond strength (µTBS), antibacterial activity, and cytotoxicity (n = 5).

Results: SEM showed that the nanotubes had a characteristic tubular-needle morphology, while the TEM analysis confirmed the presence of ATAB inside the lumens of HNT. The incorporation of ATAB:HNT induced no reduction (p > 0.05) of the DC either in situ or in vitro. No difference was encountered after the softening challenge test (p > 0.05) and no difference was found in µTBS between the two adhesives, both at 24 h (p > 0.05) and after 6 months of storage in distilled water (p > 0.05). However, ATAB:HNT reduced Streptococcus mutans viability (p < 0.05) without a cytotoxic effect on pulp cells (p > 0.05).

Conclusions: GATAB:HNT adhesive demonstrated appropriate polymerization without significant differences in softening after solvent immersion, while concomitantly maintaining reliable bond strength after 6 months of water aging. Moreover, the ATAB:HNT filler can provide antibacterial activity to the adhesive resin without affecting pulp cell viability.
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http://dx.doi.org/10.3290/j.jad.a44871DOI Listing
July 2020

Bio-additive and enameloplasty technique for restoring anterior esthetics: 54-month clinical follow-up.

Quintessence Int 2020 ;51(8):622-629

Teeth with altered size and shape, incisal wear, and inadequate position affect the smile and dentofacial harmony. The aim of this article was to describe a simple and safe protocol for an additive technique with composite resin and cosmetic enameloplasty to improve a patient's smile. A 24-year-old man complained about the appearance of his smile regarding color, shape, and position of the maxillary anterior teeth. Relevant dental history included previous orthodontic treatment with inadequate completion. The clinical examination revealed a disharmony of the smile caused by size and shape alterations of the incisors, a white spot on the right central incisor, incisal wear of the canines, and uneven incisal edges between the maxillary anterior teeth. Treatment with direct composite restoration and enameloplasty was performed in line with the current conservative approach in dentistry. The patient was recalled for 54 months. The use of appropriate techniques in enameloplasty allowed the desired outcome to be observed over the 54 months of follow-up. With this method, it is possible to perform future repair and/or modification, and it may increase the longevity of the restoration. Esthetic and functional results were achieved by careful planning and execution as well as periodic recalls. This conservative approach is a useful alternative to conventional restorations, reducing invasive treatments, chairside time, and costs.
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http://dx.doi.org/10.3290/j.qi.a44814DOI Listing
August 2020

Multifunctional antibacterial dental sealants suppress biofilms derived from children at high risk of caries.

Biomater Sci 2020 Jun 20;8(12):3472-3484. Epub 2020 May 20.

Ph.D. Program in Biomedical Sciences, Biomaterials and Tissue Engineering Division, University of Maryland School of Dentistry, Baltimore, MD 21201, USA.

Dental caries in children is a leading worldwide oral health concern. Combining antibacterial and remineralizing additives within dental sealants is a promising approach for caries prevention. Saliva contains oral bacteria that are indicative of the whole oral microbiome and may have the ability to reflect the dysbiosis present in patients with dental caries. Here, we used the saliva of children at a low and high risk of caries to culture microcosm biofilms resembling caries-associated microbial communities and investigated the changes in the biofilms promoted by the formulated dental sealants containing dimethylaminohexadecyl methacrylate (DMAHDM), a quaternary ammonium monomer, and nanoparticles of amorphous calcium phosphate (NACP). Ten volunteers were selected from each caries-risk condition for saliva collection. Biofilms were grown on the tested sealant samples using a 48 h-microcosm biofilm model. The biofilm growth, metabolic behavior, and bacterial acid production were combined with 16S rRNA sequencing analysis for the assessment of the biofilm grown over the material. The DMAHDM-NACP dental sealant formulations promoted a significant reduction in the population of mutans streptococci, total streptococci, lactobacilli, and total microorganisms in the biofilms regardless of the risk status of the donor child's saliva (p < 0.05). Metabolic and lactic acid production was greatly reduced when in contact with the DMAHDM-NACP sealants in both the sources of inoculum. The relative abundance of the Streptococcus genera derived from patients at a high risk of caries was reduced on contact with the antibacterial sealant. The dental sealant formulations were effective in modulating the growth of the biofilm derived from the saliva of children at a low and high risk of caries. The sealants formulated herein with dual functions and purpose for biointeractivity to prevent biofilm formation and mineral loss can be a reliable complementary strategy to decrease the incidence of carious lesions in children at a high risk of caries.
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http://dx.doi.org/10.1039/d0bm00370kDOI Listing
June 2020

How we are assessing the developing antibacterial resin-based dental materials? A scoping review.

J Dent 2020 08 7;99:103369. Epub 2020 May 7.

MPH Program, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA; Division of Operative Dentistry, Department of General Dentistry, University of Maryland School of Dentistry, Baltimore, MD 21201, USA. Electronic address:

Objectives: To identify antibacterial additives and screening/assessment approaches used to evaluate the antibacterial activity of resin-based restorative dental materials containing these additives.

Data: In vitro studies that compared the antibacterial effects of resin-based restorative dental materials with and without antibacterial additives were screened. Risk bias was assessed, and the following data were extracted: antibacterial additive, parental dental material, curing mode, bacterial growth outcome assessment, samples used as a substrate for bacterial growth, inoculum complexity, and culture time as an indicator of biofilm maturity.

Source: Arksey and O'Malley's five stages framework using Medline (OVID), EMBASE, and Scopus (Elsevier) databases guided this review.

Study Selection: From 6503 studies initially identified, 348 studies were considered eligible for full-text screening, and 153 were included for data extraction. Almost all studies have a high sampling bias related to both sample size and blindness. Quaternary ammonium monomers were the most investigated additive (45 %), and the most prevailing parental material was resin composite (49 %). There was extensive methodological heterogeneity among the studies for outcome assessment with the majority using resin composite disks (78 %), mono-species Streptococcus mutans as the inoculum (54 %), and a relatively short period of biofilm growth (≤24 h).

Conclusion: The findings herein present the urgent need for improved biological efficacy studies in this important and exciting field. There is a need for efforts to improve study designs to mimic the oral environment in vivo and to develop standardized methods to help understand and optimize these materials.

Clinical Significance: Most studies that incorporate antibacterial additives into resin-based materials claim promising results by bacterial reduction. However, these results should be interpreted with caution due to significant variation in the methods applied for quantifying bacterial growth, the frequent lack of complexity in the biofilms, and the often-short duration of biofilm growth.
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http://dx.doi.org/10.1016/j.jdent.2020.103369DOI Listing
August 2020

pH-responsive calcium and phosphate-ion releasing antibacterial sealants on carious enamel lesions in vitro.

J Dent 2020 06 28;97:103323. Epub 2020 Apr 28.

Ph.D. Program in Biomedical Sciences, Biomaterials and Tissue Engineering Division, University of Maryland School of Dentistry, Baltimore, MD, 21201, USA; Division of Operative Dentistry, Department of General Dentistry, University of Maryland School of Dentistry, Baltimore, MD, 21201, USA. Electronic address:

Objective: Nanoparticles of amorphous calcium phosphate (NACP) have shown beneficial effects of a robust release of calcium and phosphate ions at low pH. Here we examined the effect of NACP combined into antibacterial/rechargeable sealant formulations on the mineral content of artificial carious enamel during pH-cycling mimicking intraoral conditions.

Materials And Methods: NACP and a quaternary ammonium methacrylate (DMAHDM) were synthesized. Three resin sealants were formulated: "base formulation" (without NACP and DMAHDM, used as control); "NACP on the base formulation" (with 20 wt.% NACP); "NACP on the antibacterial formulation" (with 20 wt.% NACP and 5 wt.% DMAHDM). Standardized enamel windows on sealed non-carious human molars were demineralized and randomly divided into four groups: three groups of teeth sealed with the experimental materials and one group of teeth without sealant application used as negative control. The teeth were exposed to pH cycling regime. The changes in the mineral content of enamel were assessed by quantitative surface hardness loss in percentage (%SHL) and qualitative analyses via scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDX) and polarized light microscopy (PLM).

Results: The contact with NACP-containing formulations provoked significant lower %SHL on sealed enamel (p < 0.05) in comparison to control groups. This outcome was supported by the results of SEM-EDX, in which the enamel presented higher percentages of calcium and phosphate than control groups. PLM showed less enamel superficial demineralization around the sealants containing NACP.

Conclusion: NACP incorporated into an antibacterial sealant protected the enamel against demineralization. pH-responsive calcium and phosphate-ion releasing sealants with antimicrobial and rechargeable properties may be a reliable complementary approach for caries management.

Clinical Significance: Dental caries is the most common childhood disease. Enamel demineralization represents the initial stage of carious lesion formation and may lead to invasive dental procedures. We explored the role of amorphous calcium phosphate (NACP) in a newly-developed antibacterial and rechargeable dental sealant formulation as a preventive approach.
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http://dx.doi.org/10.1016/j.jdent.2020.103323DOI Listing
June 2020

Quantum Dots of Tantalum Oxide with an Imidazolium Ionic Liquid as Antibacterial Agent for Adhesive Resin.

J Adhes Dent 2020 ;22(2):207-214

Purpose: To synthesize tantalum oxide quantum dots (Ta2O5QDs) using an imidazolium ionic liquid as a precursor and evaluate the effect of its addition to an experimental adhesive resin on the degree of conversion (DC) and antibacterial activity.

Materials And Methods: Ta2O5QDs was synthesized from the hydrolysis of an imidazolium ionic liquid (1-n-decyl-3-methylimidazolium hexachlorotantalate [DMI.TaCl6]) and evaluated by transmission electron microscopy (TEM). The adhesive was formulated with 66.7 wt% bisphenol A-glycidyl methacrylate (bis-GMA), 33.3 wt% 2-hydroxyethyl methacrylate (HEMA) with a photoinitiator/co-initiator system. In one group, Ta2O5QDS was added to the adhesive at 1 wt% Ta2O5QDs) and one group remained without Ta2O5QDS as control (CTRL). The adhesives were evaluated for DC by Fourier Transform Infrared spectroscopy. Direct contact inhibition assay was used to evaluate the antibacterial activity of the experimental adhesive resins against biofilm formation and planktonic bacteria.

Results: Ta2O5QDs had a particle size distribution of 1.52 ± 0.73 nm. DC was 50.91 ± 4.94% for CTRL and 55.4 ± 4.58% for Ta2O5QDs (p = 0.310). Ta2O5QDs showed less Streptococcus mutans biofilm formation on adhesive surfaces (p = 0.013). There was no statistically significant difference in terms of antibacterial activity against planktonic bacteria (p = 0.079).

Conclusion: Non-agglomerated Ta2O5QDs synthesized from an imidazolium ionic liquid provided antibacterial activity to the experimental adhesive resin against biofilm formation of Streptococcus mutans.
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http://dx.doi.org/10.3290/j.jad.a44285DOI Listing
April 2020

Dental Sealant Empowered by 1,3,5-Tri Acryloyl Hexahydro-1,3,5-Triazine and α-Tricalcium Phosphate for Anti-Caries Application.

Polymers (Basel) 2020 Apr 12;12(4). Epub 2020 Apr 12.

Dental Materials Laboratory, School of Dentistry, Federal University of Rio Grande do Sul, Rua Ramiro Barcelos, 2492, Rio Branco, Porto Alegre RS 90035-003, Brazil.

Quaternary ammonium compounds and calcium phosphates have been incorporated into dental materials to enhance their biointeractivity and preventive effects. This study aimed at evaluating the physical and chemical properties and effects against of a dental sealant containing 1,3,5-tri acryloyl hexahydro-1,3,5-triazine (TAT) and α-tricalcium phosphate (α-TCP). A methacrylate-based dental sealant was initially formulated. α-TCP and TAT (G) were added to the experimental sealant at 2 wt.% each. One group was formulated without α-TCP and TAT and used as control (G). All tested resins were analyzed for polymerization kinetics and degree of conversion (DC %), Knoop hardness (KHN), softening in solvent (∆KHN%), ultimate tensile strength (UTS), the contact angle with water or with α-bromonaphthalene, surface free energy (SFE) and antibacterial activity against in biofilm and in planktonic cells. The polymerization kinetic was different between groups, but without statistical differences in the DC % (p<0.05). KHN and ΔKHN% did not change between groups (p>0.05), but G presented greater UTS compared to G (p<0.05). No differences were found for contact angle (p>0.05) or SFE (p>0.05). G showed greater antibacterial activity in comparison to G (p<0.05). The formulation of dental sealants containing TAT and α-TCP can be characterized by improved mechanical and antibacterial properties.
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http://dx.doi.org/10.3390/polym12040895DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7240744PMC
April 2020

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

Bioact Mater 2020 Jun 21;5(2):228-232. Epub 2020 Feb 21.

Dental Materials Laboratory, Postgraduate Program in Dentistry, School of Dentistry, Federal University of Rio Grande Do Sul, Rua Ramiro Barcelos, 2492, Rio Branco, 90035-003, Porto Alegre, RS, Brazil.

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, . 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.
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http://dx.doi.org/10.1016/j.bioactmat.2020.02.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7036732PMC
June 2020

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

J Funct Biomater 2020 Feb 15;11(1). Epub 2020 Feb 15.

Dental Materials Laboratory, School of Dentistry, Federal University of Rio Grande do Sul, 90035-003 Porto Alegre-RS, Brazil.

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), 1 (G), and 2 (G) wt %, and one group remained without MYTAB and was used as the control (G). The resins were analyzed for the polymerization kinetics, degree of conversion, ultimate tensile strength (UTS), antibacterial activity against , 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 to 61.88% (±1.91%) for G, without a statistically significant difference among groups ( > 0.05). The UTS values ranged from 32.85 (±6.08) MPa for G to 35.12 (±5.74) MPa for G ( > 0.05). MYTAB groups showed antibacterial activity against biofilm formation from 0.5 wt % ( < 0.05) and against planktonic bacteria from 1 wt % ( < 0.05). The higher the MYTAB concentration, the higher the cytotoxic effect, without differences between G e G ( > 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.
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http://dx.doi.org/10.3390/jfb11010009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7151596PMC
February 2020

Cerium Dioxide Particles to Tune Radiopacity of Dental Adhesives: Microstructural and Physico-Chemical Evaluation.

J Funct Biomater 2020 Feb 11;11(1). Epub 2020 Feb 11.

Dental Materials Laboratory, School of Dentistry, Federal University of Rio Grande do Sul, Rua Ramiro Barcelos 2492, Rio Branco, Porto Alegre, RS 90035-003, Brazil.

The insufficient radiopacity of dental adhesives applied under composite restorations makes the radiographic diagnosis of recurrent caries challenging. Consequently, the misdiagnosis may lead to unnecessary replacement of restorations. The aims of this study were to formulate experimental dental adhesives containing cerium dioxide (CeO) and investigate the effects of different loadings of CeO on their radiopacity and degree of conversion for the first time. CeO was characterized by X-ray diffraction analysis, Fourier transforms infrared spectroscopy, and laser diffraction for particle size analysis. Experimental dental adhesives were formulated with CeO as the inorganic filler with loadings ranging from 0.36 to 5.76 vol.%. The unfilled adhesive was used as a control. The studied adhesives were evaluated for dispersion of CeO in the polymerized samples degree of conversion, and radiopacity. CeO presented a monoclinic crystalline phase, peaks related to Ce-O bonding, and an average particle size of around 16 µm. CeO was dispersed in the adhesive, and the addition of these particles increased the adhesives' radiopacity ( < 0.05). There was a significant decrease in the degree of conversion with CeO loadings higher than 1.44 vol.%. However, all materials showed a similar degree of conversion in comparison to commercially available adhesives. CeO particles were investigated for the first time as a promising compound to improve the radiopacity of the dental adhesives.
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http://dx.doi.org/10.3390/jfb11010007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7151632PMC
February 2020

Quaternary ammonium compound as antimicrobial agent in resin-based sealants.

Clin Oral Investig 2020 Feb 1;24(2):777-784. Epub 2019 Jun 1.

Dental Materials Laboratory, School of Dentistry, Federal University of Rio Grande do Sul, Rua Ramiro Barcelos, 2492, Rio Branco, Porto Alegre, RS, 90035-003, Brazil.

Objectives: The aim of this study was to evaluate the influence of [2-(methacryloyloxy)ethyl] trimethylammonium chloride (METAC) in the physico-chemical properties, antibacterial activity and cytotoxicity of an experimental resin-based sealant.

Materials And Methods: An experimental resin-based sealant was formulated with dimethacrylates and a photoinitiator system. METAC was added at 2.5 wt.% (G) and 5 wt.% (G) into the experimental resin-based sealant, and one group remained without METAC as control (G). The resin-based sealants were analysed for polymerization behaviour and degree of conversion (DC), Knoop hardness (KHN) and softening in solvent (ΔKHN), ultimate tensile strength (UTS), contact angle, surface free energy (SFE), immediate and long-term micro-shear bond strength (μ-SBS) and antibacterial activity and cytotoxicity against human keratinocytes.

Results: The experimental resin-based sealants presented different polymerization behaviours without significant differences in the DC (p > 0.05). There was no significant difference for initial KHN (p > 0.05). The ΔKHN ranged from 51.62 (±3.70)% to 62.40 (±4.14)%, with higher values for G (p < 0.05). G and G had decreased μ-SBS between immediate and long-term tests (p < 0.05) without significant differences among groups in the immediate and long-term analyses (p > 0.05). There were no significant differences for UTS, contact angle and SFE among groups (p > 0.05). G and G presented immediate and long-term antibacterial activity (p < 0.05) without cytotoxicity compared to G (p > 0.05).

Conclusion: The addition of METAC provided antibacterial activity to the experimental resin-based sealant.

Clinical Relevance: METAC is an effective quaternary ammonium compound as an antibacterial agent for resin-based sealants without cytotoxic effects against human keratinocytes.
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http://dx.doi.org/10.1007/s00784-019-02971-4DOI Listing
February 2020

Ionic liquid as antibacterial agent for an experimental orthodontic adhesive.

Dent Mater 2019 08 23;35(8):1155-1165. Epub 2019 May 23.

Dental Materials Laboratory, School of Dentistry, Federal University of Rio Grande do Sul, Ramiro Barcelos Street, 2492, Rio Branco, Porto Alegre, RS, 90035-003, Brazil. Electronic address:

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.NTf).

Methods: The experimental orthodontic adhesives were formulated with methacrylate monomers, photoinitiators and silica colloidal. The ionic liquid BMIM.NTf was synthesized and characterized. BMIM.NTf was added at 5 (G), 10 (G) and 15 (G) wt.%. One group contained no BMIM.NTf to function as control (G). 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.NTf showed the characteristic chemical peaks. The polymerization kinetics were different among the groups. G and G showed higher DC (p < 0.05). G and G 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. All groups with BMIM.NTf showed antibacterial activity compared to G (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.NTf) 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.
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http://dx.doi.org/10.1016/j.dental.2019.05.010DOI Listing
August 2019

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

Braz Oral Res 2019 Mar 18;33:e019. Epub 2019 Mar 18.

Universidade Federal do Rio Grande do Sul - UFRGS, School of Dentistry, Dental Materials Laboratory, Porto Alegre, RS, Brazil.

The aim of this study was to evaluate the influence of polyhexamethylene guanidine hydrochloride (PHMGH) in the physico-chemical properties and antibacterial activity of an experimental resin sealant. An experimental resin sealant was formulated with 60 wt.% of bisphenol A glycol dimethacrylate and 40 wt.% of triethylene glycol dimethacrylate with a photoinitiator/co-initiator system. PHMGH was added at 0.5 (G0.5%), 1 (G1%), and 2 (G2%) wt.% and one group remained without PHMGH, used as control (GCTRL). The resin sealants were analyzed for degree of conversion (DC), Knoop hardness (KHN), and softening in solvent (ΔKHN), ultimate tensile strength (UTS), contact angle (θ) with water or α-bromonaphthalene, surface free energy (SFE), and antibacterial activity against Streptococcus mutans for biofilm formation and planktonic bacteria. There was no significant difference for DC (p > 0.05). The initial Knoop hardness ranged from 17.30 (±0.50) to 19.50 (± 0.45), with lower value for GCTRL (p < 0.05). All groups presented lower KHN after immersion in solvent (p < 0.05). The ΔKHN ranged from 47.22 (± 4.30) to 57.22 (± 5.42)%, without significant difference (p > 0.05). The UTS ranged from 54.72 (± 11.05) MPa to 60.46 (± 6.50) MPa, with lower value for G2% (p < 0.05). PHMGH groups presented no significant difference compared to GCTRL in θ (p > 0.05). G2% showed no difference in SFE compared to GCTRL (p > 0.05). The groups with PHMGH presented antibacterial activity against biofilm and planktonic bacteria, with higher antibacterial activity for higher PHMGH incorporation (p < 0.05). PHMGH provided antibacterial activity for all resin sealant groups and the addition up to 1 wt.% showed reliable physico-chemical properties, maintaining the caries-protective effect of the resin sealant over time.
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http://dx.doi.org/10.1590/1807-3107bor-2019.vol33.0019DOI Listing
March 2019

Halloysite nanotubes loaded with alkyl trimethyl ammonium bromide as antibacterial agent for root canal sealers.

Dent Mater 2019 05 1;35(5):789-796. Epub 2019 Mar 1.

Departamento de Odontología, Facultad de Ciencias de la Salud, Universidad CEU-Cardenal Herrera, C/Del Pozos/n, Alfara del Patriarca, 46115 Valencia, Spain. Electronic address:

Objective: This study aimed at evaluating the effects of experimental endodontic sealers containing halloysite nanotubes (HNT) doped with alkyl trimethyl ammonium bromide (ATAB).

Methods: An experimental dual-cure resin sealer was formulated and used as control material. This resin was also filled with ATAB and HNT at different ratios (GATAB:HNT 1:1; 1:2; 2:1) generate three experimental resin sealers. The ATAB:HNT filler was characterized through transmission electron microscopy (TEM). While, the experimental and control sealers were evaluated for degree of conversion, softening ration, radiopacity, flow, film thickness, antibacterial activity for biofilm and planktonic bacteria and cytotoxicity in human pulpal cells.

Results: GATAB:HNT significantly increased the immediate DC (p < 0.05), although no difference was encountered between the groups after 24 h (p > 0.05). All the experimental cements (ATAB/HNT) showed relatively low initial Knoop hardness (p < 0.05), but with no significant reduction (p > 0.05) after storage in ethanol (softening ratio). The radiopacity of all groups achieved at least 3 mm of aluminum. All groups showed more than 17 mm of flow, with a film thickness lower than 50 μm (ISO 6876:2012). All the experimental ATAB:HNT cements showed antibacterial activity against E. faecalis; the higher the ATAB ratio, the greater the antibacterial activity (p < 0.05). Cell viability was higher than 70% with no significant difference between the groups (p > 0.05).

Significance: The incorporation of ATAB/HNT into the experimental resin sealers induced antibacterial activity against biofilm and planktonic E. faecalis without affecting the pulp cell viability or the chemo-mechanical properties.
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http://dx.doi.org/10.1016/j.dental.2019.02.018DOI Listing
May 2019

Triclosan-loaded chitosan as antibacterial agent for adhesive resin.

J Dent 2019 04 19;83:33-39. Epub 2019 Feb 19.

Dental Materials Laboratory, School of Dentistry, Federal University of Rio Grande do Sul, Rua Ramiro Barcelos, 2492, Rio Branco, 90035-003, Porto Alegre, RS, Brazil. Electronic address:

Objectives: The aim of this study was to formulate and to evaluate the immediate and long-term physical, chemical and antibacterial properties of an experimental adhesive resin with chitosan or triclosan-loaded chitosan.

Materials And Methods: Chitosan, triclosan and triclosan-loaded chitosan were evaluated for scanning electron microscopy (SEM) and micro-Raman spectroscopy. An experimental adhesive resin was formulated with methacrylate monomers and photoinitiators. Chitosan or triclosan-loaded chitosan were added at 2 (G and G) or 5 (G and G) wt.% in the base resin. The base resin was used as control (G). The adhesives were evaluated for degree of conversion (DC), Knoop hardness (KHN), softening in solvent (ΔKHN), immediate and long-term microtensile bond-strength (μ-TBS) and antibacterial activity.

Results: SEM indicated triclosan sticks and chitosan porosity. Triclosan-loaded chitosan presented structures on chitosan. Micro-Raman indicated no chemical interaction between chitosan and triclosan. There was no difference among groups for DC (p > 0.05). Initial KHN ranged from 17.36 (±1.56) to 20.38 (±1.72), with higher value for G compared to G (p < 0.05). G presented the lowest ΔKHN% (p < 0.05). There were no differences in the immediate or long-term μ-TBS (p > 0.05). G and G decreased the μ-TBS after storage (p < 0.05). Chitosan groups showed higher biofilm formation (p < 0.05). Triclosan-loaded chitosan groups presented lower biofilm formation (p < 0.05). There was no activity against planktonic bacteria regardless the time of evaluation (p > 0.05).

Conclusion: Triclosan-loaded chitosan at 5 wt.% addition in an experimental adhesive resin showed reliable properties, with the highest antibacterial activity immediately and after six months, and induced dentin/adhesive interface stability over time.

Clinical Significance: Triclosan-loaded chitosan groups showed antibacterial activity immediately and over time and induced dentin/adhesive interface stability, may positively affecting long-lasting marginal sealing.
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http://dx.doi.org/10.1016/j.jdent.2019.02.002DOI Listing
April 2019

Tantalum oxide as filler for dental adhesive resin.

Dent Mater J 2018 Nov 26;37(6):897-903. Epub 2018 Jul 26.

Dental Materials Laboratory, School of Dentistry, Federal University of Rio Grande do Sul, Rua Ramiro Barcelos.

The purpose of this study was to formulate and evaluate an adhesive resin with tantalum oxide. TaO was evaluated by scanning electron microscopy and laser diffraction. The adhesive was formulated with methacrylate monomers and photoinitiators. TaO was added into the adhesive at 1, 2, 5 and 10 wt%. One group remained without filler (control group). TaO distribution, radiopacity (n=5), degree of conversion (DC) (n=3), softening in solvent (n=5) and ultimate tensile strength (UTS) (n=10) were evaluated. Data were analyzed by one-way ANOVA and Tukey's test (α=0.05). Spherical nanometric TaO was arranged in 3.35 µm particles. The groups over 5 wt% presented higher radiopacity (p<0.05). The DC ranged from 61.78 (±1.19)% to 67.35 (±1.40)%, with statistical difference from control group over 5 wt% addition (p<0.05). There was no difference in softening in solvent (p>0.05) and UTS (p>0.05). Tantalum oxide is a promising alternative for adhesive formulation and it could be further tested for biomimetic remineralization.
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http://dx.doi.org/10.4012/dmj.2017-308DOI Listing
November 2018

Influence of zinc oxide quantum dots in the antibacterial activity and cytotoxicity of an experimental adhesive resin.

J Dent 2018 06 10;73:57-60. Epub 2018 Apr 10.

Dental Materials Laboratory, School of Dentistry, Federal University of Rio Grande do Sul, Rua Ramiro Barcelos, 2492, Rio Branco, 90035-003, Porto Alegre, RS, Brazil. Electronic address:

Objective: To evaluate the influence of zinc oxide quantum dots (ZnO) into an experimental adhesive resin regarding the antibacterial activity against Streptococcus mutans and the cytotoxicity against pulp fibroblasts.

Materials And Methods: ZnO were synthesized by sol-gel process and were incorporated into 2-hydroxyethyl methacrylate (HEMA). An experimental adhesive resin was formulated by mixing 66.6 wt.% bisphenol A glycol dimethacrylate (BisGMA) and 33.3 wt.% HEMA with a photoinitiator system as control group. HEMA containing ZnO was used for test group formulation. For the antibacterial activity assay, a direct contact inhibition evaluation was performed with biofilm of Streptococcus mutans (NCTC 10449). The cytotoxicity assay was performed by Sulforhodamine B (SRB) colorimetric assay for cell density determination using pulp fibroblasts. Data were analyzed by Student's t-test (α = 0.05).

Results: The antibacterial activity assay indicated statistically significant difference between the groups (p = 0.003), with higher values of biofilm formation on the polymerized samples of control group and a reduction of more than 50% of biofilm formation on ZnO group. No difference of pulp fibroblasts viability was found between the adhesives (p = 0.482).

Conclusion: ZnO provided antibacterial activity when doped into an experimental adhesive resin without cytotoxic effect for pulp fibroblasts. Thus, the use of ZnO is a strategy to develop antibiofilm restorative polymers with non-agglomerated nanofillers.

Clinical Significance: ZnO are non-agglomerated nanoscale fillers for dental resins and may be a strategy to reduce biofilm formation at dentin/restoration interface with no cytotoxicity for pulp fibroblasts.
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http://dx.doi.org/10.1016/j.jdent.2018.04.003DOI Listing
June 2018

Influence of Different Calcium Phosphates on an Experimental Adhesive Resin.

J Adhes Dent 2017 ;19(5):379-384

Purpose: To formulate adhesive resins with 2 wt% of hydroxyapatite (HAp), α-tricalcium phosphate (α-TCP), or octacalcium phosphate (OCP) and to compare these groups with an unfilled adhesive regarding the degree of conversion, polymerization rate, microshear bond strength and mineral deposition.

Materials And Methods: The experimental adhesive resin was formulated mixing 66.6 wt% bisphenol A glycol dimethacrylate (bis-GMA), 33.3 wt% 2-hydroxyethyl methacrylate (HEMA), and a photoinitiator system. OCP, α-TCP, or HAp were added in concentrations of 2 wt% to the adhesive, and a group without additional filler was used as the control. Calcium-phosphate particle sizes were determined using a laser-diffraction particle-size analyzer. The degree of conversion (DC) of the adhesives was determined with FTIR-ATR. The polymerization rate (Rp) was determined using differential scanning calorimetry equipped with a photocalorimetric accessory. Adhesive bonding was evaluated using the microshear bond strength test in sound bovine mandibular incisors. Mineral deposition in human third molars affected by caries was evaluated using micro-Raman spectroscopy after selective removal of carious dentin. Data were analyzed by one-way ANOVA and Tukey's test (α = 0.05).

Results: HAp presented the highest mean particle size (26.7 nm), while that of α-TCP was 6.03 nm and OCP was 4.94 nm. The DC of all groups was above 50%. The OCP group showed the fastest Rp, with no difference from the control group (p > 0.05). The α-TCP group presented the highest microshear bond strength (p = 0.005) and mineral deposition at the interface.

Conclusion: Incorporation of α-TCP nanofiller into adhesive resins can improve bond strengths and may be a promising strategy to achieve therapeutic remineralization at the composite-dentin interface.
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http://dx.doi.org/10.3290/j.jad.a38997DOI Listing
January 2019

Influence of niobium pentoxide addition on the properties of glass ionomer cements.

Acta Biomater Odontol Scand 2016 Dec 5;2(1):138-143. Epub 2016 Oct 5.

Dental Materials Laboratory, Department of Conservative Dentistry, Federal University of Rio Grande do SulPorto AlegreBrazil.

To determine the influence of niobium pentoxide (NbO) addition on the physical and chemical properties of glass ionomer cements (GICs). Five, 10 or 20 wt.% of NbO were incorporated into commercial GICs (Maxxion R, Vitro Molar, Vitro Fil R) and one group of each GIC remained without NbO (control groups). The GICs were evaluated by Knoop hardness, compressive strength, acid erosion, particle size and radiopacity. Data were analyzed by two-way ANOVA followed by Tukey's test. The addition of 10% and 20% reduced the microhardness of two GICs ( < .05). Compressive strength showed no difference among groups ( > .05). NbO did not influence Maxxion R and Vitro Fil R regarding the acid erosion test ( > .05). Vitro Molar increased its acid erosion with 10% of NbO ( < .05). Maxxion R presented 15.78 μm, while Vitro Molar and Vitro Fil R showed 5.14 μm and 6.18 μm, respectively. As the NbO concentration increased, the radiopacity increased for all groups. Vitro Molar and Vitro Fil R did not present significant difference to at least 1 mm aluminum ( > .05). The addition of 5 wt.% NbO did not affect the tested physical and chemical properties of the GICs and improved the radiopacity of one of the cements. These materials are therefore suitable for further testing of biomimetic remineralization properties.
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http://dx.doi.org/10.1080/23337931.2016.1239182DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5433193PMC
December 2016