Physicochemical characterization of experimental resin-based materials containing calcium orthophosphates or calcium silicate.

OBJECTIVE: To evaluate experimental dimethacrylate-based materials containing calcium orthophosphates or calcium silicate particles in terms of their optical, mechanical and Ca2+ release behaviour. METHODS: Dicalcium phosphate dihydrate (DCPD), hydroxyapatite (HAp), beta-tricalcium phosphate (ß-TCP) or calcium silicate (CaSi) particles were added to a photocurable BisGMA/TEGDMA resin (1:1 in mols) at a 30 vol% fraction. Materials containing silanized or non-silanized barium glass particles were used as controls. Degree of conversion (DC) at the top and base of 2-mm thick specimens was determined by ATR-FTIR spectroscopy (n = 5). Translucency parameter (TP) and transmittance (%T) were determined using a spectrophotometer (n = 3). Biaxial flexural strength (BFS) and flexural modulus (FM) were determined by biaxial flexural testing after 24 h storage in water (n = 10). Ca2+ release in water was determined during 28 days by inductively coupled plasma optical emission spectrometry (n = 3). Statistical analysis was performed using ANOVA/Tukey test (DC: two-way; TP, %T; BFS and FM: one-way; Ca2+ release: repeated measures two-way, α = 5 %). RESULTS: CaSi and ß-TCP particles drastically reduced DC at 2 mm, TP and %T (p < 0.001). Compared to both controls, all Ca2+-releasing materials presented lower BFS (p < 0.001) and only the material with DCPD showed significantly lower FM (p < 0.05). The material containing CaSi presented the highest Ca2+ release, while among materials formulated with calcium orthophosphates the use of DCPD resulted in the highest release (p < 0.001). SIGNIFICANCE: CaSi particles allowed the highest Ca2+ release. Notwithstanding, the use of DCPD resulted in a material with the best compromise between optical behaviour, DC, strength and Ca2+ release.

Achieving property enhancements in dental resin composites via reduced concentrations of camphorquinone within a ternary initiator system.

OBJECTIVES: The study aimed to assess the impact of diphenyliodonium hexafluorophosphate (DPI) on the physicochemical properties of experimental resin composites (ECRs) featuring reduced concentrations of camphorquinone (CQ)/amine. METHODS: Five concentrations of CQ (0.125, 0.25, 0.5, 0.75, and 1 mol%) with dimethylaminoethyl amine benzoate (EDAB) in a 1:2 mol% ratio (CQ:EDAB) were incorporated into a 50:50 mass% monomer blend of bisphenol glycidyl methacrylate (BisGMA) and triethyleneglycol dimethacrylate (TEGDMA). An additional 5 groups with the same CQ:EDAB concentrations had 0.5 mol% DPI added. Each resin group contained 60 wt% of 0.7 µm barium-alumino-silicate glass. Light transmission (n = 3), real-time degree of polymerization (n = 3), temperature change during polymerization (n = 5), polymerization shrinkage strain (n = 3), flexural strength, and modulus (n = 12), as well as water sorption and solubility (n = 5), were evaluated. Data were analyzed using two-way ANOVA and Tukey's post-hoc test (α = 0.05). RESULTS: Light transmission was reduced in groups containing 0.125 and 0.25 mol% of CQ without DPI. DPI increased temperature, degree and rate of polymerization, despite the reduction in CQ/amine concentration. Additionally, there was an increase in polymerization shrinkage strain, flexural strength and modulus, and a reduction in water sorption and solubility in ECRs with DPI, even with lower concentrations of CQ/EDAB. SIGNIFICANCE: DPI improved the assessed properties of composites across various concentrations of CQ/EDAB, showing the benefit of reducing the quantity of CQ used without compromising the properties and curing of the resin composites.

Clinical performance of posterior restorations using a universal adhesive over moist and dry dentin: A 36-month double-blind split-mouth randomized clinical trial.

OBJECTIVES: To evaluate the influence of dentin moisture on the clinical behavior of a universal adhesive on posterior teeth after 36 months of follow-up. METHODS: Forty-five patients participated in this study. Following a split-mouth design, three operators placed 90 Class I/Class II restorations over moist dentin (MD) or dry (DD) (n = 45) with resin composite (Filtek Bulk Fill) and a universal adhesive used in the etch-and-rinse mode (Single Bond Universal). Each restoration was evaluated according to the FDI and USPHS criteria (postoperative sensitivity, fracture and retention, marginal staining, marginal adaptation, and recurrence of caries) at baseline and after 6-, 12-, and 36 months. For statistical analysis, Kruskal Wallis analysis of variance rank (α = 0.05) and Kaplan-Meier survival analysis were used. RESULTS: No significant difference between groups was observed in each FDI criterion after 36 months of clinical evaluation (p > 0.05). The retention rates (confidence interval 95 %) were 97.37 % (86.5 - 99.5) for both MD and DD without significant difference between them (p > 0.05). Eight restorations (MD = 4; DD = 4) showed minimal marginal staining defects (p > 0.05). Two restorations were lost (MD = 1; DD = 1). Fifteen restorations (MD = 8; DD = 7) presented minor marginal discrepancies according to the FDI criteria (p > 0.05). CONCLUSION: The clinical performance of the universal adhesive when applied in etch-and-rinse mode was not influenced by dentin moisture in posterior bulk-fill composite restorations. CLINICAL SIGNIFICANCE: The level of dentin moisture appears not to influence the clinical efficacy of a universal adhesive when applied using the etch-and-rinse technique in posterior composite resin restorations.

The influence of filler load in 3D printing resin-based composites.

OBJECTIVE: To evaluate the influence of the barium glass (BG) filler in 3D printing resin-based composites for restorative structures. METHODS: Experimental 3D printing resin-based composites were formulated with UDMA 70%wt, Bis-EMA 20%wt, and TEGDMA 10%wt. Photoinitiators TPO and DFI (2%wt) were used. BG was incorporated at 40%wt and 50%wt. 0%wt BG was used as negative control and the VarseoSmile Crownplus (Bego) was used as a commercial control. Specimens were printed using a 3D printer. Subsequently, specimens were washed and submitted to post-curing with 405 nm at 60ºC for 2 × 20 min at FormCure (FormLabs). 3D printing resin-based composites were evaluated by flexural strength, degree of conversion, softening in solvent, radiopacity, and cytotoxicity against gingival fibroblasts. Data were statistically analyzed using one-way ANOVA (α = 0.05). RESULTS: No significant differences in flexural strength were showed between BG40% (90.5 ± 5,4 MPa), BG50% (102.0 ± 11.7 MPa) and VA (105.2 ± 11.7 MPa). Addition of 40% and 50% of BG showed no influence in the degree of conversion compared to VA (p > 0.05). All groups showed softening in solvent after immersion in ethanol (p < 0.05). All groups showed more than 1mmAl of radiopacity. BG50% showed significantly higher radiopacity (2.8 ± 0.3 mmAl) than other groups (p < 0,05). Cytotoxicity evaluation showed gingival cell viability higher than 80% for all groups. SIGNIFICANCE: Addition of up to 50%wt of barium glass in experimental 3D printing resin-based composites showed promising results for long-term restorative structures.

Ion release mechanisms in composites containing CaP particles and hydrophilic monomers.

OBJECTIVE: To investigate the effect of hydrophilic/permeable polymer matrices on water sorption/solubility (WS/SL), Ca2+ release, mechanical properties and hydrolytic degradation of composites containing dicalcium phosphate dihydrate (DCPD) particles. METHODS: Six composites were tested, all with 10 vol% of glass particles and either 30 vol% or 40 vol% DCPD. Composites containing 1BisGMA:1TEGDMA in mols (at both inorganic levels) were considered controls. Four materials were formulated where 0.25 or 0.5 of the BisGMA/TEGDMA was replaced by pyromellitic dianhydride glycerol dimethacrylate (PMGDM)/ polyethylene glycol dimethacrylate (PEGDMA). Composites were tested for degree of conversion (FTIR spectroscopy), WS/SL (ISO 4049) and Ca2+ release (inductively coupled plasma optical emission spectroscopy). Fracture toughness (FT) and biaxial flexural strength/modulus (BFS/FM) were determined after 24 h and 60 days in water. The contributions of diffusional and relaxational mechanisms to Ca2+ release kinetics were analyzed using the semi-empirical Salim-Peppas model. Data were analysed by ANOVA/Tukey test (alpha: 0.05). RESULTS: WS/SL was higher for composites containing PMGDM/PEGDMA compared to the controls (p < 0.001). Only at 40% DCPD the 0.5 PMGDM/PEGDMA composite showed statistically higher Ca2+ release than the control. Relaxation diffusion was the main release mechanism. Initial FT was not negatively affected by matrix composition. BFS (both DCPD fractions) and FM (30% DCPD) were lower for composites with hydrophilic/permeable networks (p < 0.01). After 60 days in water, composites with PMGDM/PEGDMA presented significant reductions in FT, while all composites had reductions in BFS/FM. SIGNIFICANCE: Increasing matrix hydrophilicity/permeability significantly increased Ca2+ release only at a high DCPD fraction.

A new method of adhesive system application improves the bond strength between fiber post and root dentin.

This study evaluated a new method of adhesive system application on the bond strength between fiber post and root dentin using two adhesive systems. The canals of sixty bovine incisors were prepared and obturated. The roots were divided into six groups (n=10) according to the adhesive system (Clearfil SE - CSE and Single Bond Universal - SBU) and the application strategy (microbrush - MB; rotary brush - RB; and ultrasonic tip - US). The glass fiber posts were cemented with resin cement (RelyX ARC). The roots were sectioned perpendicularly to their long axis, and three slices per root were obtained. Previously to the push-out test, confocal laser scanning microscopy (CLSM) was performed to illustrate the interfacial adaptation of the cement to the root canal walls. Failure patterns were analyzed with 40x magnification. Shapiro-Wilk indicated a normal distribution of the data. The bond strength values were compared using one-way ANOVA and Tukey's tests. Student's T test analyzed the differences between the adhesive systems within each third and protocol. A significance level of 5% was used. CSE with RB showed higher mean bond strength values compared to MB (conventional technique) (P < 0.05). US application resulted in intermediate bond strength values for CSE (P > 0.05). The application of SBU using RB generated higher mean bond strength values compared to MB and US (P < 0.05). Adhesive failures were predominant (65.5%). CSE and SBU application with the new rotary brush improved the bond strength of fiber posts to root dentin compared to the conventional strategy.

Bisphenol A released and ultrastructural changes in dental composite resins

Dental composite resins may release bisphenol-A or similar molecules affecting patient health and the environment. This study measured bisphenol-A release from three commonly used in patients composite resins (Filtek™ Z350 XT, Filtek™ P60, Filtek™ Bulk Fill) immersed in three liquid mediums (artificial saliva, 0.001 M lactic acid and 15% ethanol) and assessed the changes in the surface micromorphology.The released BPA was measured by HPLC at basal time (t=0), 1 h, 1 d, 7 d and 30 d. Topographic analysis of specimens was performed by scanning electron microscopy (SEM). The data were analyzed using one-way ANOVA and Tukey post-hoc test (P < 0.05). BPA in solution increased significantly in the three DCRs immersed in 0.001 M lactic acid at all times. SEM micrographs of the specimen in 0.001 M lactic acid disclosed more structural defects than others. The surface of the three composite resins was morphologically affected by their immersion in all solutions. SEM evidenced that the dental materials underwent erosion and cracks with filler particles protruding from the surface. The morphological changes in tested dental materials produced by exposure to these solutions are potentially dangerous to patients by causing caries, infections, and partial loss of dental material.

Effect of silver diamine fluoride on the longevity of the bonding properties to caries-affected dentine.

OBJECTIVES: This study aimed to evaluate the adhesive properties in dentine after the application of silver diamine fluoride (SDF) on carious dentine lesions immediately and after 2 years of water storage. METHODS: 96 human molars used were subjected to artificial dentine caries production, and then randomly divided into 12 experimental groups according to 1. application of an SDF solution (carious dentine lesion without SDF treatment [control], with 12 % silver diamine fluoride [SDF 12 %] or 38 % silver diamine fluoride [SDF 38 %]); 2. Universal adhesives (Clearfil Universal Bond Quick [CUQ] and Single Bond Universal [SBU]); 3. adhesive strategy (etch-and-rinse [ER] and self-etch [SE]). After restoration, the specimens were sectioned and submitted to the microtensile bond strength test (µTBS) and energy-dispersive X-ray spectrometry analysis (SEM/EDX). All tests were performed immediately and after 2 years of water storage. Data from the µTBS were analyzed using four-way ANOVA and Tukey's test (α = 0.05). RESULTS: Only the interaction of factors 'SDF' vs 'time' was significant (p = 0.03). After 2 years of storage, the groups where SDF was applied showed higher µTBS values compared to the control group. No significant decrease in µTBS values was observed for SBU when comparing immediate and 2-year results, but a significant reduction in µTBS values was observed after 2 years for CUQ. CONCLUSION: Independent of the adhesive strategy, the use of SDF may be a promising alternative to maintain the bonding of universal adhesives to carious dentinal lesions. CLINICAL SIGNIFICANCE: This study may clarify and support clinicians regarding the longevity of resin-based restoration in caries-affected dentine treated with silver diamine fluoride.

Cytotoxicity evaluation, antibacterial effect, and degree of conversion of QAM-containing adhesives.

The aim of this study was to evaluate the influence of adding quaternary ammonium methacrylates (QAMs) to experimental adhesives by assessing the degree of conversion (DC), cytotoxicity against keratinocytes and fibroblasts, and antibacterial activity against biofilm formation. Two QAMs were added to an experimental adhesive: dimethylaminododecyl methacrylate bromododecane (DMADDM) or dimethylaminododecyl methacrylate bromohexadecane (DMAHDM) at three concentrations each: 1, 2.5, and 5 wt.%. Experimental adhesive without QAMs (control group) and commercially available Transbond XT Primer (3M Unitek, Monrovia, California, USA) were used for comparisons. The adhesives were tested for DC, cytotoxicity against keratinocytes and fibroblasts, and antibacterial activity against biofilm formation. DC, cytotoxicity against fibroblasts, and antibacterial activity were analyzed using one-way ANOVA and Tukey's multiple comparisons. Cytotoxicity against keratinocytes was evaluated using the Kruskal Wallis and Dunn's post-hoc (α = 5%) tests. Transbond showed lower DC as compared to 5% DMAHDM, 1% DMADDM, and 5% DMADDM (p < 0.05). However, all groups presented proper DC when compared to commercial adhesives in the literature. In the evaluation of cytotoxicity against keratinocytes, Transbond induced higher viability than 2.5 wt.% groups (p < 0.05). Against fibroblasts, Transbond induced higher viability as compared to 5 wt.% groups (p < 0.05). DMAHDM at 5 wt.% reduced biofilm formation when compared to all the other groups (p < 0.05). Despite their cytotoxic effect against keratinocytes, gingival fibroblasts showed higher viability. DMAHDM at 5 wt.% decreased Streptococcus mutans viability. The incorporation of DMAHDM at 5 wt.% may be a strategy for reducing the development of white spot lesions.

Effect of elastomeric urethane monomer on physicochemical properties and shrinkage stress of resin composites.

This study aimed to evaluate the effect of an elastomeric urethane monomer (Exothane-24) in different concentrations on physicochemical properties, gap formation, and polymerization shrinkage stress of experimental resin composites. All experimental composites were prepared with 50 wt.% of Bis-GMA and 50 wt.% of TEGDMA, to which 0 wt.% (control), 10 wt.%, 20 wt.%, 30 wt.%, and 40 wt.% of Exothane-24 were added. Filler particles (65 wt.%) were then added to these resin matrixes. Ultimate tensile strength (UTS: n = 10), flexural strength (FS: n = 10), flexural modulus (FM: n = 10), hardness (H: n = 10), hardness reduction (HR: n = 10), degree of conversion (DC: n = 5), gap width (GW: n = 10), and polymerization shrinkage stress in Class I (SS-I: n = 10) and Class II (SS-II: n = 10) simulated configuration. All test data were analyzed using one-way ANOVA and Tukey's test (α = 0.05;  = 0.2). Exothane-24 in all concentrations decreased the H, HR, DC, GW, SS-I, and SS-II (p < 0.05) without affecting the UTS, and FS (p > 0.05). Reduction in FM was observed only in the Exothane 40% and 30% groups compared to the control (p < 0.05). Exothane-24 at concentrations 20% and 30% seems suitable since it reduced GW and polymerization SS without affecting the properties of the composite resins tested, except for H.

Transdentinal cytotoxicity of resin luting cements using the bovine and human dentin barrier.

STATEMENT OF PROBLEM: Based upon ethical questions and because of the difficulty of obtaining intact human teeth, researchers have used bovine teeth to assess the physical and mechanical properties of different dental materials. However, data from transdentinal cytotoxicity tests showing that the bovine dentin barrier is similar to the human dentin barrier is lacking. PURPOSE: The purpose of this in vitro study was to evaluate whether the bovine dentin barrier produces similar results to those obtained when the human dentin barrier is used to assess the transdentinal cytotoxicity of resin luting cements. MATERIAL AND METHODS: The number and diameter of dentinal tubules present in the human dentin barrier and bovine dentin barrier were evaluated and assessed with a t test (α=.05). After inserting the standardized dentin barriers into artificial pulp chambers, murine dental papilla-derived cells (MDPC-23) were seeded on the pulpal surface of the specimens, and the luting cements were applied to their occlusal surfaces. Then, the following groups were established for both human and bovine dentin barriers: no treatment (negative control); Single Bond Universal; RelyX Luting 2; RelyX U200; and RelyX Ultimate. After 24 hours, the viability (alamarBlue) and morphology (scanning electron microscopy) of the cells were evaluated with a 2-way analysis of variance and the Tukey honest significance test (α=.05). RESULTS: Dentinal tubules with larger diameters were observed in bovine dentin (P<.05), but the number of tubules was similar (P>.05). A reduction in viability and notable changes in the morphology of MDPC-23 cells occurred in the Single Bond Universal and RelyX Luting 2 groups in comparison with the negative control (P<.05). The RelyX U200 and RelyX Ultimate groups were statistically similar to the negative control (P>.05). No difference was found in cytotoxicity when the same luting cement was applied on human or bovine dentin barriers (P>.05). CONCLUSIONS: For transdentinal cytotoxicity tests of resin luting cements, the bovine dentin barrier proved similar results to the human dentin barrier.

Effect of preheating on mechanical properties of a resin-based composite containing elastomeric urethane monomer.

This study investigated the effect of preheating an elastomeric urethane monomer (Exothane-24) experimental resin composite on its physicochemical properties. Two resin matrices were formulated: (a) 50 wt% Bisphenol-glycidyl methacrylate (Bis-GMA) and 50 wt% triethylene glycol dimethacrylate (TEGDMA); and (b) 20 wt% Exothane-24, 40 wt% Bis-GMA and 40 wt% TEGDMA. A photoinitiator system (0.25 wt% camphorquinone and 0.50 wt% ethyl-4-dimethylamino benzoate) and 65 wt% of the inorganic filler (20 wt% 0.05 µm silica and 80 wt% 0.7 µm BaBSiO2 glass) were added to both matrices. These formulations were then assigned to four groups: Exothane-24 (E); Exothane-24 plus preheating (EH); no Exothane-24 (NE); and no Exothane-24 plus preheating (NEH). NEH and EH were preheated at 69 °C. The dependent variables were as follows: film thickness (FT); polymerization shrinkage stress (PSS); gap width (GW); maximum rate of polymerization (Rpmax); and degree of conversion (DC). Data were statistically analyzed by two-way ANOVA and Tukey's test (α = 0.05). Preheating reduced FT for both composites. PSS and GW were significantly lower for EH, when compared with E. The DC for EH and NEH and the Rpmax for EH increased significantly. Preheating improved most of the physicochemical properties (FT, PSS, GW, and DC) of the experimental resin composite containing Exothane-24.

Release of leachable products from resinous compounds in the saliva of children with anterior open bite treated with spur.

BACKGROUND: To evaluate the release of bisphenol-A glycidyl methacrylate (BisGMA), triethylene glycol dimethacrylate (TEGDMA), bisphenol A (BPA), and phthalates of the composite resin used in the bonding of spurs applied in the treatment of children with anterior open bite and its effects on human keratinocytes. METHODOLOGY: Saliva samples of 22 children were collected before spur attachment (baseline) and 30 minutes (min) and 24 hours (h) after spur bonding. Analysis was performed using high-performance liquid chromatography (HPLC) coupled to tandem mass spectrometry (HPLC-MS/MS) and gas chromatography coupled to mass spectrometry (GC-MS). Standardized resin increments were added to three different dilutions of the cell culture medium. Keratinocytes (HaCaT) were cultivated in the conditioned media and evaluated for cell viability (MTT) and cell scratch assay. RESULTS: The levels of BisGMA (1.74±0.27 µg/mL), TEGDMA (2.29±0.36 µg/mL), and BPA (3.264±0.88 µg/L) in the saliva after 30 min, in comparison to baseline (0±0 µg/mL, 0±0 µg/mL, and 1.15±0.21 µg/L, respectively), presented higher numbers. After 24 h, the levels of the monomers were similar to the baseline. Phthalates showed no significant difference among groups. HaCat cells showed increased viability and reduced cell migration over time after exposure to methacrylate-based resin composites. CONCLUSION: Resin composites, used to attach spurs in children with anterior open bite during orthodontic treatment, release monomers after polymerization and can influence the behavior of human keratinocytes, even at very low concentrations. Orthodontists should be aware of the risks of the resinous compounds release and preventive procedures should be held to reduce patient exposure.

Orthodontic resins loaded with niobium silicate particles: Impact of filler concentration on the physicochemical and biological properties.

OBJECTIVES: White spot lesions (WSL) are prevalent in patients using orthodontic appliances. The presence of ion-releasing compounds in the tooth-appliance interface may limit enamel demineralization to control WSL incidence. Thus, this study aims to evaluate the mineral formation on SiNb-containing experimental orthodontic resins and the influence of these fillers on the physicochemical and biological properties of developed materials. MATERIALS AND METHODS: The SiNb particles were synthesized via the sol-gel route and characterized by their molecular structure and morphology. Photopolymerizable orthodontic resins were produced with a 75 wt% Bis-GMA/25 wt% TEGDMA and 10 wt%, 20 wt%, or 30 wt% addition of SiNb. A control group was formulated without SiNb. These resins were tested for their degree of conversion, softening in solvent, cytotoxicity in fibroblasts, flexural strength, shear bond strength (SBS), and mineral deposition. RESULTS: The addition of 10 wt% of SiNb did not impair the conversion of monomers, cytotoxicity, and flexural strength. All groups with SiNb addition presented similar softening in solvent. The presence of these particles did not affect the bond strength between metallic brackets and enamel, with SBS values ranging from 16.41 to 18.66 MPa. The mineral deposition was observed for all groups. CONCLUSION: The use of niobium silicate as filler particles in resins may be a strategy for the adhesion of orthodontic appliances. The 10 wt% SiNb concentration resulted in a material with suitable physicochemical and biological properties while maintaining the bond strength to tooth enamel and promoting mineral deposition.

Development of functional fillers as a self-healing system for dental resin composite.

OBJECTIVES: To evaluate the incorporation of repairing capsules containing different monomers and polymerization modulators on the self-healing efficiency of an experimental photopolymerizable resin-based composite. METHODS: Self-healing capsules containing different monomers and polymerization modulators were prepared by emulsion polymerization: TCDHEPT (TEGDMA and DHEPT), BTCDHEPT (Bis-GMA, TEGDMA, and DHEPT), and BTCBPO (Bis-GMA, TEGDMA, and BPO). The capsules were analyzed through Fourier transform infrared spectroscopy and scanning electron microscopy. The capsules were added into experimental photopolymerizable resin composites establishing the following groups: ER (Control without capsules), ER+BPO, ER+BPO+TCDHEPT, and ER+BTCBPO+BTCDHEPT. Filtek Z350 resin composite (3 M ESPE) was used as a commercial reference. The materials were tested for degree of conversion (DC), flexural strength (σf), elastic modulus (Ef), fracture toughness (virgin KIC), self-healing efficiency (healed KIC), and roughness. For statistical analysis, the significance value was established at an a = 0.05 level. RESULTS: When compared to the control material, the incorporation of repairing capsules did not affect DC, σf, and Ef. Fracture toughness was statistically similar between the experimental groups (p ≤ 0.05). Healed KIC was statistically different between the groups ER+TCDHEP and ER+BTCBPO+BTCDHEPT; the self-healing efficiency was higher for ER+TCDHEPT. Surface roughness was statistically similar among all groups. CONCLUSIONS: The use of self-healing capsules promoted repair of the material. Studies with material aging after the self-healing process are necessary to better demonstrate the effectiveness of this system. CLINICAL SIGNIFICANCE: The self-healing system seemed to be a promising technology to be used in self-repaired restorative materials, which may prevent restoration fractures.

Enhanced mechanical properties, anti-biofilm activity, and cytocompatibility of a methacrylate-based polymer loaded with native multiwalled carbon nanotubes.

OBJECTIVES: We aimed to optimize the mechanical and biological properties of a conventional methacrylate-based dental polymer by loading it with double- and triple-walled carbon nanotubes as growth (DTWCNTG). METHODS: A formulation of bisphenol A-glycidyl methacrylate and triethylene glycol dimethacrylate (mass ratio = 2:1) was mixed with DTWCNTG at concentrations of 0.0% (control), 0.001%, 0.005%, and 0.010%. The concentrations were physicochemical and morphologically evaluated, and antibacterial activity was assessed by seeding a Streptococcus mutans strain (ATCC 25175) on the experimental polymeric surfaces. Cellular survival and osteodifferentiation were evaluated in epithelial (HaCat) and preosteoblast cells (MC3T3-E1). RESULTS: The 0.001% DTWCNTG concentration yielded higher compressive strength, elastic modulus, flexural strength, flexural modulus, water sorption, and solubility than the control. The degree of conversion and color did not significantly change with a low amount of DTWCNTG incorporated into the polymer. Antibacterial activity significantly improved when tested on the 0.001% DTWCNTG discs. No groups showed cytotoxicity in a short-term analysis and adding DTWCNTG favored MC3T3-E1 mineralization over the control, particularly in the 0.001% formulation. SIGNIFICANCE: The micro-addition of 0.001% DTWCNTG confers mechanical resistance, antimicrobial properties, and bioactivity to methacrylate-based polymers without significantly compromising color. Incorporating DTWCNTG improved dental composite properties and could be a biomodified material for minimally invasive procedures.

Consultorio de Salud Ambiental en un Hospital Privado de Comunidad de la Ciudad de Buenos Aires / Environmental Health consulting office in a Private Community Hospital of the Buenos Aires City

En los últimos años surge el concepto de Una Sola Salud que reconoce la interdependencia sistémica al observar que los cambios en la salud humana se expresan de manera sincrónica e indivisible de la salud del ambiente. Nuevas enfermedades y daños crónicos inespecíficos ocurren a la par de la pérdida de biodiversidad y vitalidad. En las últimas décadas venimos observando el surgimiento de "adaptaciones sistémicas" que requieren un abordaje desde la clínica y la toxicología a nivel individual y desde la epidemiología de la complejidad a nivel poblacional. Luego de un largo recorrido de investigaciones, el Hospital Italiano formalizó el consultorio de Salud Ambiental con la intención de brindar respuesta a la demanda de pacientes que atribuyen síntomas y signos a la polución ambiental. (AU)

In recent years, the concept of One Health has emerged, recognizing the systemic interdependence and the changes in human health that are expressed synchronously and indivisible from the environment. New diseases and nonspecific chronic damage are occuring in parallel with the loss of biodiversity and vitality.In recent decades we have observed the appearance of "systemic adaptations" that require a clinical and toxicological approach at the individual level, and address the population level from an epidemiological and complexity science paradigm. After many years of research, the Hospital Italiano de Buenos Aires formalized the Environmental Health consulting office and the measurement of glyphosate levels, giving answer to the demand of patients who associate their signs and symptoms to environmental pollution. (AU)

Comparison of a resin-based sealant with a nano-filled flowable resin composite on sealing performance of marginal defects in resin composites restorations: a 36-months clinical evaluation.

OBJECTIVES: Our goal was to evaluate the clinical behavior of resin-based composite (RBC) restorations with sealed marginal defects using nano-filled flowable RBCs (FRS) compared with resin-based sealant (RBS); this work used marginal adaptation, marginal staining, and secondary caries according to the World Dental Federation (FDI) criteria. MATERIALS AND METHODS: This was a prospective, randomized, double-blind, controlled trial. Fifty-four patients who met the inclusion criteria (older than 18 years old; with high cariogenic risk determined by Cariogram software; and restorations with marginal defects, 3 and 4 according to FDI criteria) were randomly divided into three groups. There were three defective RBC restorations per patient and were repaired (n = 162). The groups were RBS-marginal sealing using a resin-based sealant (Clinpro Sealant, 3 M ESPE, MN, USA) plus adhesive (Single Bond Universal, 3 M ESPE, MN, USA); FRS-sealing using flowable resin (Filtek Flow Z350XT, 3 M ESPE, MN, USA) plus adhesive (Single Bond Universal, 3 M ESPE, MN, USA); and control-no repair treatment. All procedures were performed under complete isolation. Evaluations were evaluated at 1-week post treatment (baseline) as well as at 18 and 36 months after treatment regarding marginal adaptation, marginal staining, and secondary caries according to FDI criteria. The data were analyzed using the Wilcoxon test (α = 0.05) to compare the differences in each treatment group at different evaluation times. RESULTS: Marginal adaptation of micro-repaired RBC restorations were seen in patients with a high risk of caries using flowable resin composite or resin-based sealants. There were differences (P < 0.001) when baseline was compared at 18 and 36 months. Marginal staining showed differences when baseline was compared to 18 months (P < 0.001) and 36 months (P = 0.001) for both treatments. Secondary caries parameters for RBS treatment showed differences when baseline was compared to 36 months (P = 0.025) and when 18 months was compared to 36 months (P = 0.046). CONCLUSIONS: Micro-repair of RBC restorations resulted in clinical deterioration of marginal adaptation and marginal staining. Nano-filled flowable resin composites were sealed on defective restorations; 3 and 4 FDI marginal defects have better clinical performance to prevent secondary caries than resin-based sealants after 36 months. CLINICAL RELEVANCE: Micro-repair with RBS does not seem to be an effective treatment to prevent secondary caries.

Photopolymerizable dental composite resins with lower shrinkage stress and improved hydrolytic and hygroscopic behavior with a urethane monomer used as an additive.

This work reports the synthesis of a monomer 2-((2-(3-(prop-1-en-2-yl)phenyl)propan-2-yl)carbamoyl)oxy)ethyl methacrylate (MVTPM) and the evaluation of its performance as an additive in the formulation of Bis-GMA/TEGDMA based composite resins. Experimental composite resins formulated with the MVTPM monomer were compared with a control reference. Double bond conversion, polymerization kinetics, shrinkage and associated stress, sorption, and aqueous solubility, cell viability, as well as mechanical properties were evaluated according to international measurements standards. The experimental composite resins show comparable mechanical properties with the control reference and improvements in other properties, such as better hydrolytic and hygroscopic behavior and lower shrinkage stress, are reported. This makes MVTPM monomer potentially useful in the formulation of dental composite resins.

Evaluation of the dentinal tubule penetration of an endodontic bioceramic sealer after three final irrigation protocols

Introduction: This study aimed to evaluate the dentinal tubule penetration of an endodontic bioceramic sealer, Sealer Plus BC, after three final irrigation protocols. Methods: Thirty distobuccal roots of maxillary molars were selected. Root canal preparation was performed up to an #40.06 instrument (X1 Blue) under 2.5% sodium hypochlorite irrigation. Specimens were randomly divided into three groups (n=10), according to the final irrigation protocol: G-NaOCl (2.5% sodium hypochlorite + PUI), G-SS (0.9% saline solution + PUI) and G-H20 (Deionized water + PUI). After final irrigation protocols, all specimens were irrigated with phosphate buffer solution. Root canal obturation was performed using the single cone technique and Sealer Plus BC, stained with a specific fluorophore. Specimens were transversely sectioned and each root third was evaluated in a confocal scanning laser microscopy. Images obtained were analyzed for sealer penetration in the dentinal tubules. Results: Dentinal tubule penetration of Sealer Plus BC was not observed in any root third, regardless of the final irrigation protocol investigated. Conclusions: Sealer Plus BC dentinal tubule penetration was not observed after none of the protocols tested. Dentinal tubule penetrability of Sealer Plus BC may be related to other factors rather than the final irrigation protocol.