Publications by authors named "Fabrício Mezzomo Collares"

97 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

Polybutylene-adipate-terephthalate and niobium-containing bioactive glasses composites: Development of barrier membranes with adjusted properties for guided bone regeneration.

Mater Sci Eng C Mater Biol Appl 2021 Jun 19;125:112115. Epub 2021 Apr 19.

Dental Materials Laboratory, School of Dentistry, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil. Electronic address:

This study aimed to develop bioactive guided bone regeneration (GBR) membranes by manufacturing PBAT/BAGNb composites as casting films. Composites were produced by melt-extrusion, and BAGNb was added at 10 wt%, 20 wt%, and 30 wt% concentration. Pure PBAT membranes were used as a control (0wt%BAGNb). FTIR and thermogravimetric analysis characterized the composites. Barrier membranes were produced by solvent casting, and their mechanical and surface properties were assessed by tensile strength test and contact angle analysis, respectively. The ion release and cell behavior were evaluated by pH, cell proliferation, and mineralization. Composites were successfully produced, and the chemical structure showed no interference of BAGNb in the PBAT structure. The addition of BAGNb increased the stiffness of the membranes and reduced the contact angle, increasing the roughness in one side of the membrane. Sustained pH increment was observed for BAGNb-containing membranes with increased proliferation and mineralization as the concentration of BAGNb increases. The incorporation of up to 30 wt% of BAGNb into PBAT barrier membranes was able to maintain adequate chemical-mechanical properties leading to the production of materials with tailored surface properties and bioactivity. Finally, this biomaterial class showed outstanding potential and may contribute to bone formation in GBR procedures.
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http://dx.doi.org/10.1016/j.msec.2021.112115DOI Listing
June 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

Biological Properties of Experimental Methacrylate-Based Sealers Containing Calcium Phosphates.

Braz Dent J 2021 Jan-Feb;32(1):59-66

Department of Conservative Dentistry, School of Dentistry, UFRGS - Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.

This study aimed to evaluate, in vitro and in vivo, the biocompatibility of experimental methacrylate-based endodontic sealers containing α-tricalcium phosphate (α-TCP) or nanostructured hydroxyapatite (HAp). Experimental methacrylate-based dual-cure sealers with the addition of α-TCP or HAp, at 10%wt were formulated and compared to AH Plus (AHP). Cell viability was assessed by 3-(4,5-dimethyl-thiazoyl)-2,5-diphenyl-tetrazolium bromide (MTT), and sulforhodamine B (SRB). Sealers were implanted in rats' subcutaneous tissue and histologically evaluated. Bioactivity was assessed by alkaline phosphatase enzyme activity (ALP) and Alizarin Red (AR), using apical papillary cells (SCAPs), and by the bone deposition measured in surgical cavities on rats' femur filled with AH Plus or α-TCP. In both viability assays, HAp and AHP sealers were similar, and α-TCP presented lower viability compared to the others at MTT assay (p<0.05). A gradual decrease of the inflammatory response according to the periods was observed and AHP was the only that presented giant cells (7-day period). Collagen fibers condensation increased according to the periods, with no differences among sealers. There was an increase at ALP activity and mineralized nodules deposition according to periods. HAp and α-TCP presented higher values for ALP activity at 5 days and at 5, 10, and 15 days for AR and were different from AHP (p<0.05). α-TCP presented superior values at 10 and 15 days compared to HAp and AHP for AR (p<0.05). At 90 days, α-TCP and control (empty cavity) showed high bone deposition compared to AHP (p<0.05). α-TCP and HAp, in a methacrylate-based sealer, presented biocompatibility and bioactivity, with the potential to be used as endodontic sealers in clinical practice. Further investigations are required to gain information on the physicochemical properties of these sealers formulation before its clinical implementation.
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http://dx.doi.org/10.1590/0103-6440202103761DOI Listing
May 2021

Long-term exposure to low doses of aluminum affects mineral content and microarchitecture of rats alveolar bone.

Environ Sci Pollut Res Int 2021 Apr 21. Epub 2021 Apr 21.

Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Pará, Augusto Corrêa, n1, Belém, 66075-110, Pará, Brazil.

Aluminum (Al) is one of the most found elements in nature in many forms, and human exposure can be quite common. Therefore, it is important to investigate the effects of exposure to Al mainly at low doses and for a prolonged period, in order to simulate human exposure in the periodontium, an important structure for support and protection of the teeth. This investigation aimed to study the aluminum chloride (AlCl) toxicological effects in the mineral composition and micromorphology of the alveolar bone of rats. Two groups of eight male Wistar rats were used for the experiment. AlCl group was exposed to AlCl orally at a dose of 8.3 mg/kg/day for 60 days, while the control group received only distilled water. After that, the mandibles were collected and submitted to the following analyses: Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray microtomography analysis; blood was also collected for determination of Al circulating levels. Our data showed that AlCl was capable of increasing Al circulating levels in blood. It was able to promote changes in the mineral content and triggers significant changes in the mineralized bone microstructure, such as number and thickness of trabeculae, being associated with alveolar bone-loss.
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http://dx.doi.org/10.1007/s11356-021-13937-zDOI Listing
April 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

Binge-Like Exposure During Adolescence Induces Detrimental Effects in Alveolar Bone that Persist in Adulthood.

Alcohol Clin Exp Res 2021 01 22;45(1):56-63. Epub 2020 Dec 22.

Laboratory of Functional and Structural Biology, (DS-M, MKMF, RRL), Biological Science Institute, Federal University of Pará, Belém, Pará, Brazil.

Background: Alcohol (EtOH) intake during adolescence has become an important public health issue. Although the detrimental effects of EtOH intake on the musculoskeletal system are well known, only a few studies have investigated its impact on the stomatognathic system of adolescents. This study aimed to investigate the effect of EtOH binge drinking on the alveolar bone and the long-term consequences after abstinence.

Methods: Adolescent female Wistar rats (35 days old) were exposed to 4 cycles of EtOH binge drinking (3 g/kg/d; 3 days On-4 days Off) or distilled water (control group). Alveolar bone micromorphology and vertical bone distance were evaluated at 1, 30, and 60 days after that last EtOH intake through X-ray computed microtomography. The mineral:matrix ratio was assessed through Raman spectroscopy.

Results: A decrease in both trabecular thickness and volume ratio, and an increase in trabecular separation were observed at the 1-day evaluation (immediate withdrawal). After 30 and 60 days, the alveolar bone parameters were found similar to control, except for the mineral:matrix ratio in the long-term abstinence.

Conclusions: EtOH binge drinking during adolescence results in alveolar bone damage that may persist in adulthood, even after abstinence.
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http://dx.doi.org/10.1111/acer.14501DOI Listing
January 2021

Niobium silicate particles as bioactive fillers for composite resins.

Dent Mater 2020 12 29;36(12):1578-1585. Epub 2020 Sep 29.

Dental Materials Laboratory, School of Dentistry, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil. Electronic address:

Objectives: This study aimed to evaluate the influence of niobium silicate (SiNb) particles in the physicomechanical and biological properties of an experimental composite resin.

Methods: The SiNb particles were incorporated (50 wt%) into a polymeric matrix formulated with 70 wt% Bisphenol A-Glycidyl Methacrylate and 30 wt% Triethylene Glycol Dimethacrylate to formulate an experimental composite resin. A control group was formulated with barium silicate glass (SiBa) as filler for the same polymeric matrix. The composite resins were tested for their refractive index, polymerization kinetics, flexural strength, radiopacity, softening in solvent, pH, cytotoxicity and mineral deposition.

Results: The SiBa group presented refractive index results between 1.50 and 1.52 and the SiNb between 1.43-1.45. No statistically significant difference in the degree of conversion, flexural strength, and softening in solvent was observed between different groups. Radiopacity was lower for SiNb, while the addition of these particles increased cell viability. The pH was increased for all groups after immersion. The mineral deposition analysis resulted in increased deposition above specimens after the immersion in SBF.

Significance: Niobium silicate particles may be used as an alternative inorganic filler to achieve an adequate balance between physical-chemical and biological properties for the development of bioactive composite resins.
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http://dx.doi.org/10.1016/j.dental.2020.09.010DOI Listing
December 2020

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

Niobium silicate as a filler for an experimental photopolymerizable luting agent.

J Prosthodont Res 2021 Feb 9;65(1):25-30. Epub 2020 Sep 9.

Dental Materials Laboratory, School of Dentistry, Federal University of Rio Grande do Sul, Rua Ramiro Barcelos, 2492/4th floor, Porto Alegre, RS.

Purpose: To synthesize niobium silicate particles (SiNb) and incorporate into resin-based luting agents.

Methods: SiNb particles were synthesized and characterized by x-ray diffraction, FTIR spectroscopy, particle size, and specific surface area. Luting agents were formulated with 50 wt% BisGMA, 30 wt% TEGDMA and 20 wt% UDMA. BAPO was used as a photoinitiator in 1mol%. The SiNb particles were incorporated into the agents at concentrations of 50 wt% (SiNb50%) or 65% wt% (SiNb65%). Barium glass particles at the same concentrations were used as controls (SiBa50% and SiBa65%). Refractive index, degree of conversion (DC), polymerization kinetics, softening in solvent, radiopacity, film thickness, color stability, flexural strength (FS) and micro shear bond strength (µSBS) were evaluated.

Results: SiNb particles were successfully synthesized with an adequate structure to be applied as inorganic fillers. SiNb groups had higher DC, lower %ΔKHN, greater film thickness and greater radiopacity than the SiBa groups. Color stability was greater for SiNb50% and SiNb65% after six months of storage, as demonstrated by ΔE00. ΔWID values were lower for the SiBa groups. FS results decreased over time, and lower values were found for SiNb. In µSBS, the values of SiNb65% were higher at 24 h (45.22 MPa) and at six months (36.83 MPa), with statistically differences from values for the SiBa groups.

Conclusions: SiNb particles were successfully synthesized using the sol-gel method, and their incorporation into luting agents at a concentration of up to 65% improved the physicomechanical characteristics and color stability of these agents.
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http://dx.doi.org/10.2186/jpr.JPOR_2019_420DOI Listing
February 2021

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

Prolonged caffeine intake decreases alveolar bone damage induced by binge-like ethanol consumption in adolescent female rats.

Biomed Pharmacother 2020 Oct 9;130:110608. Epub 2020 Aug 9.

Laboratory of Functional and Structural Biology, Biological Science Institute, Federal University of Pará, Belém, Pará, Brazil.

Ethanol consumption has been reported to negatively impact on periodontal disease. In particular, oral cavity disorders occur upon ethanol exposure during adolescence, a life period associated with particular patterns of short and intense ('binge-like') ethanol consumption that is most deleterious to oral health. The hazardous central effects of ethanol have been linked to the overfunction of adenosine receptors, which are antagonized by caffeine, a bioactive substance present in numerous natural nutrients, which can also modify bone metabolism. The aim of this study was to investigate the effects of caffeine on alveolar bone damage induced by an ethanol binge drinking paradigm during adolescence. Female Wistar rats (35 days old; n = 30) were allocated to six groups: control (vehicle), ethanol (3 g/kg/day; 3 days On-4 days Off challenge), caffeine (10 mg/kg/day), caffeine plus ethanol, SCH58261 (0.1 mg/kg/day, an antagonist of A receptors), and SCH58261 plus ethanol. Bone micromorphology and vertical bone loss were analyzed by computed microtomography. Our data showed that ethanol binge drinking reduced alveolar bone quality, with repercussion on alveolar bone size. This ethanol-induced alveolar bone deterioration was abrogated upon treatment with caffeine, but not with SCH58261. This shows that caffeine prevented the periodontal disorder caused by ethanol binge drinking during adolescence, an effect that was not mediated by adenosine A receptor blockade.
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http://dx.doi.org/10.1016/j.biopha.2020.110608DOI Listing
October 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

Ethanol binge drinking exposure affects alveolar bone quality and aggravates bone loss in experimentally-induced periodontitis.

PLoS One 2020 30;15(7):e0236161. Epub 2020 Jul 30.

Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Pará (UFPA), Belém, Pará, Brazil.

Background: Periodontitis is a multifactorial inflammatory disease of tooth supporting tissues caused by oral biofilms, influenced by environmental and genetic factors, among others. Ethanol consumption has been considered a factor that enhances alveolar bone loss, especially in high doses. The present study aims to investigate the changes promoted by ethanol binge drinking per se or associated with ligature-induced periodontal breakdown on alveolar bone loss.

Materials And Methods: Thirty-two Wistar rats were randomly allocated into four groups: control (C), ethanol (3g/kg/day; 3 days On-4 days Off protocol by gavage for 28 days, EtOH), experimental periodontitis (EP) and experimental periodontitis plus ethanol administration (EP+EtOH). On day 14th, periodontitis was induced by ligatures that were placed around the lower first molars. On day 28th, the animals were euthanized and mandibles were submitted to stereomicroscopy for exposed root area analysis and micro-computed tomography (micro-CT) for the evaluation of alveolar bone loss and microstructural parameters.

Results: The results revealed that ligature-induced alveolar bone loss is aggravated by ethanol binge drinking compared to controls (1.06 ± 0.10 vs 0.77 ± 0.04; p<0.0001). In addition, binge drinking per se altered the alveolar bone quality and density demonstrating a reduction in trabecular thickness, trabecular number parameter and bone density percentual. Periodontal disorder plus ethanol binge drinking group also demonstrated reduction of the quality of bone measured by trabecular thickness.

Conclusions: In conclusion, intense and episodic ethanol intake decreased alveolar bone quality in all microstructural parameters analyzed which may be considered a modifying factor of periodontitis, intensifying the already installed disease.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0236161PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7392256PMC
September 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

Blood Oxidative Stress Modulates Alveolar Bone Loss in Chronically Stressed Rats.

Int J Mol Sci 2020 May 25;21(10). Epub 2020 May 25.

Laboratory of Functional and Structural Biology, Institute of Biological Sciences, Federal University of Para, Belem 66075-900, PA, Brazil.

We aimed to investigate the effects of chronic stress (CS) on experimental periodontitis (EP) in rats. For this, 28 Wistar rats were divided into four groups: control, ligature-induced experimental periodontitis (EP), chronic stress (CS; by physical restraint model) and CS+EP (association of chronic stress and ligature-induced periodontitis). The experimental period lasted 30 days, including exposure to CS every day and ligature was performed on the 15th experimental day. After 30 days, the animals were submitted to the behavioral test of the elevated plus maze (EPM). Next, rats were euthanized for blood and mandible collection in order to evaluate the oxidative biochemistry (by nitric oxide (NO), reduced-glutathione activity (GSH), and thiobarbituric acid reactive substance levels (TBARS)) and alveolar bone characterization (by morphometric, micro-CT, and immunohistochemistry), respectively. The behavioral parameters evaluated in EPM indicated higher anxiogenic activity in the CS and CS+EP, groups, which is a behavioral reflex of CS. The results showed that CS was able to change the blood oxidative biochemistry in CS and CS+EP groups, decrease GSH activity in the blood, and increase the NO and TBARS concentrations. Thus, CS induces oxidative blood imbalance, which can potentialize or generate morphological, structural, and metabolic damages to the alveolar bone.
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http://dx.doi.org/10.3390/ijms21103728DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7279478PMC
May 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