Physical and mechanical properties of dual functional cements-an in vitro study.

OBJECTIVES: The aim of this study was to evaluate the physical and mechanical properties of different dual functional cements. MATERIALS AND METHODS: Three dual functional cements (Allcem Core (FGM), Rebilda DC (VOCO), and LuxaCore Z (DMG)), a luting resin cement (Rely X ARC (3 M ESPE)), and a Core Buildup composite resin GrandioSo (VOCO) were used. Flexural strength (n = 10) and film thickness (n = 6) were evaluated according to ISO 4049:2009. Flow (n = 6) was evaluated according to ISO 6876:2001. Degree of conversion (DC) was assessed immediately and 24 h after polymerization (n = 5). For resistance to dislodgment (RD) analysis, bovine teeth were prepared to receive fiber glass posts, and a push-out test (n = 12) was used. RESULTS: Luxacore Z presented lower flexural strength when compared to GrandioSo (p < 0.001). No statistical difference was found between cements for film thickness (p = 0.66). Reduced flow values were found for Allcem Core (p = 0.006). No statistical difference was found for immediate DC for different cements (p > 0.05). After 24 h, DC increased for all groups, except for Luxacore Z (p = 0.054). The RD did not differ from the control Rely X ARC, regardless of the root third (p > 0.05). Luxacore Z showed lower mean values in the apical third compared to the coronal third (p = 0.046). CONCLUSIONS: The dual functional cements (Allcem Core and Rebilda DC) possessed similar physical and mechanical properties of luting resin cement (RelyX ARC) and Core Buildup composite resin (GrandioSo). Hence, they could be used for one-stage post and core buildup restorations. CLINICAL RELEVANCE: The dual functional cements could be used for one-stage post and core buildup restorations since they possess similar physical and mechanical properties of luting resin cements and Core Buildup composite resin.

Calcium phosphates as fillers for methacrylate-based sealer.

OBJECTIVES: The aim of this study was to evaluate the mineral deposition, push-out bond strength, radiopacity, the degree of conversion, film thickness, flow, calcium ion release, and pH of experimental endodontic sealers containing hydroxyapatite (HAp), aflfa-ticalcium phosphate (α-TCP), or octacalcium phosphate (OCP) particles. MATERIALS AND METHODS: Fifty single straight root human premolars were instrumented and divided into five groups (n = 10). Experimental endodontic sealers were formulated by 70 wt% urethane dimethacrylate (UDMA), 15 wt% of glycerol-1,3-dimethacrylate (GDMA), 15 wt% of ethoxylated bisphenol A glycol dimethacrylate (BISEMA), camphorquinone (CQ), N,N-dihydroxyethyl-para-toluidine (DHEPT), and benzoyl-peroxide. 10 wt% of each HAp, α-TCP, or OCP were added to the resin and its properties were assessed. RESULTS: After 7 days, the degree of conversion ranged from 44.69% (GOCP) to 50.74% (Gcontrol) and no statistical difference were observed (p < 0.05). GAHplus showed the highest push-out bond strength 4.91 (± 2.38) MPa at 28 days of analysis (p < 0.05). Film thickness and pH were not statistically different (p > 0.05). Statically lower values of flow were found for GHAp, GOCP, and Gα-TCP (p < 0.05). Calcium deposition values were higher for GHAp at 28 days. CONCLUSIONS: Bond strength, degree of conversion, and film thickness of endodontic sealers with phosphates showed similar results compared with AHplus, but displayed higher amounts of Ca2+ release. CLINICAL RELEVANCE: Phosphate fillers improve the performance of endodontic sealers after 28 days of simulated body fluid.

Effect of nanostructured zirconium dioxide incorporation in an experimental adhesive resin.

OBJECTIVES: The aim of this study was to evaluate the influence of nanostructured zirconium dioxide incorporation in an experimental adhesive resin. METHODS: ZrO2 particles were characterized by X-ray diffraction (XRD), micro-Raman spectroscopy and Brunauer-Emmett-Teller (B.E.T). Experimental adhesive resins were formulated with 0, 0.5, 1, 4.8, and 9.1% ZrO2 in weight. The adhesives were evaluated based on degree of conversion (DC), radiopacity, softening in solvent and microtensile bond strength (µTBS) 24 h and after 1 year of aging. Mineral deposition at the hybrid layer was assessed with micro-Raman spectroscopy at the baseline and after 14 days. RESULTS: XRD showed monoclinic and tetragonal phases of ZrO2.particles. B.E.T data revealed a surface area of 37.41 m2/g, and typical chemical groups were shown on the Raman spectra. The addition of ZrO2 did not influence the radiopacity. The addition of 4.8% and 9.1 wt.% ZrO2 showed higher initial hardness with increased softening in solvent (P < 0.05) and promoted mineral deposition at the dentin interface. DC was significantly increased in the group with 1% ZrO2 (P < 0.05). The µTBS test showed difference on the group with 9.1 wt.% of ZrO2, with a significant reduction after aging. CONCLUSION: The incorporation of ZrO2 promoted mineral deposition on the adhesive interface and the addition of 1 wt.% caused a significant increase on the DC without compromising the other physicochemical characteristics, which may prove promising for the development of new dental adhesive systems. CLINICAL RELEVANCE: The mineral deposition on the hybrid layer can result in a longer stability of the adhesive, thus delaying the hydrolytic degradation.

Influence of Different Calcium Phosphates on an Experimental Adhesive Resin.

PURPOSE: To formulate adhesive resins with 2 wt% of hydroxyapatite (HAp), α-tricalcium phosphate (α-TCP), or octacalcium phosphate (OCP) and to compare these groups with an unfilled adhesive regarding the degree of conversion, polymerization rate, microshear bond strength and mineral deposition. MATERIALS AND METHODS: The experimental adhesive resin was formulated mixing 66.6 wt% bisphenol A glycol dimethacrylate (bis-GMA), 33.3 wt% 2-hydroxyethyl methacrylate (HEMA), and a photoinitiator system. OCP, α-TCP, or HAp were added in concentrations of 2 wt% to the adhesive, and a group without additional filler was used as the control. Calcium-phosphate particle sizes were determined using a laser-diffraction particle-size analyzer. The degree of conversion (DC) of the adhesives was determined with FTIR-ATR. The polymerization rate (Rp) was determined using differential scanning calorimetry equipped with a photocalorimetric accessory. Adhesive bonding was evaluated using the microshear bond strength test in sound bovine mandibular incisors. Mineral deposition in human third molars affected by caries was evaluated using micro-Raman spectroscopy after selective removal of carious dentin. Data were analyzed by one-way ANOVA and Tukey's test (α = 0.05). RESULTS: HAp presented the highest mean particle size (26.7 nm), while that of α-TCP was 6.03 nm and OCP was 4.94 nm. The DC of all groups was above 50%. The OCP group showed the fastest Rp, with no difference from the control group (p > 0.05). The α-TCP group presented the highest microshear bond strength (p = 0.005) and mineral deposition at the interface. CONCLUSION: Incorporation of α-TCP nanofiller into adhesive resins can improve bond strengths and may be a promising strategy to achieve therapeutic remineralization at the composite-dentin interface.

Effect of indomethacin-loaded nanocapsules incorporation in a dentin adhesive resin.

OBJECTIVES: The aim of this study was to produce indomethacin-loaded nanocapsules (IndOH-NCs) and evaluate the influence of their incorporation into an adhesive resin. MATERIALS AND METHODS: Indomethacin was encapsulated by the deposition of preformed polymer. IndOH-NCs were characterized by laser diffractometry, Fourier transformed infrared spectrometry, transmission electron microscopy (TEM), scanning electron microscopy, high-performance liquid chromatography (HPLC), and MTT assay. Nanocapsules (NCs) were incorporated into an adhesive in concentrations of 1, 2, 5, and 10 %. The addition was visualized by TEM and drug release was evaluated by HPLC until 120 h of immersion in simulated body fluid (SBF). Drug diffusion through dentin was tested using a Franz diffusion cell apparatus and quantified by HPLC. The degree of conversion (DC), softening in ethanol, and microtensile bond strength (µTBS) were evaluated to determine whether the nanocapsules influenced the adhesive. Data were analyzed using one-way ANOVA and Tukey's post hoc test for DC, softening in ethanol, µTBS, and cytotoxicity, and paired t test for comparison between the initial and final Knoop microhardness. RESULTS: IndOH-NCs, with a spherical shape and a mean diameter of 165 nm, were incorporated into an adhesive. Indomethacin content was 7 mg drug/g powder. IndOH-NCs maintained high cell viability. At 120 h, an amount of 13.83 % of indomethacin was released, and after 7 days, 7.07 % of this drug was diffused through dentin for an adhesive containing 10 % of nanocapsules. No alteration in the DC, softening in ethanol, and µTBS resulted from NC addition. CONCLUSIONS: IndOH-NCs may be incorporated into adhesive systems, without compromising properties, to add an anti-inflammatory drug controlled release for restorative procedures in deep cavities. CLINICAL SIGNIFICANCE: Here is the first step toward the goal of providing agents to act at an inflammatory process of pulp tissue through dental adhesives via encapsulation of drug.

In vitro antibacterial and remineralizing effect of adhesive containing triazine and niobium pentoxide phosphate inverted glass.

OBJECTIVES: White spot lesions are still a concern for orthodontic patients. The objective of this study was to assess the remineralizing and antibacterial effect of a newly developed orthodontic adhesive. METHODS: The compounds 1,3,5-tryacryloylhexahydro-1,3,5-triazine (TAT) and phosphate invert glass containing 10 mol% of niobium pentoxide (PIG-Nb) were added at 20 and 5 wt%, respectively, to an experimental adhesive (75 wt% BisGMA, 25 wt% TEGDMA, 5 wt% fummed silica, and photo-initiator system), called TPN. A group without the addition of these compounds was used as Control and the orthodontic adhesive Transbond XT (TXT) was used for comparison. Antibacterial activity was evaluated through surface biofilm formation, mineral deposition, and degree of conversion (DC) through Raman microscopy, Knoop hardness after softening in solvent, and bracket dislodgement (BD). RESULTS: TPN group presented a reduction in bacterial growth when compared to Control and TXT. Mineral deposits were observed on the surface of TPN adhesive after 14 and 28 days of immersion in artificial saliva. There was an increase in DC after 28 days, whereas TPN group presented the highest DC. All groups underwent some degree of softening. No significant changes were observed in BD after 28 days of immersion in artificial saliva. CONCLUSION: The newly developed orthodontic adhesive, with addition of 20 wt% TAT and 5w% PIG-Nb, exhibited antibacterial activity and was capable to induce mineral deposition on its surface in vitro. CLINICAL SIGNIFICANCE: The orthodontic adhesive developed in this study with antibacterial activity and mineral deposition could be a reliable choice for brackets adhesion.

Thermocompaction decreases long-term push-out bond strength of methacrylate-based sealers.

PURPOSE: The purpose of this study was to evaluate the immediate and long-term bond strengths to root dentin of Epiphany/Resilon and AH Plus/gutta-percha fillings, after using either lateral condensation or Tagger's hybrid thermomechanical compaction techniques. MATERIALS AND METHODS: Eighty human single-rooted teeth were used. The root canals were prepared by means of hand crown-down technique up to a #45 K-file and irrigation with 1% sodium hypochlorite was performed. Samples were randomly divided into eight (n=10) experimental groups divided according to filling material (gutta-percha/AH Plus and Resilon/Epiphany), obturation technique (Lateral compaction and Tagger's hybrid thermomechanical compaction) and storage time (24 h and 6 months). During storage, the samples were kept at 37°C and 100% humidity. After the two experimental periods, each root was sectioned perpendicular to its long axis into three serial slices and push-out tests were carried out using a universal testing machine. Statistical significant differences were set by ANOVA and Tuckey post-hoc (p<0.05). RESULTS: Using thermocompaction technique, the samples filled with Epiphany/Resilon decreased significantly the bond strength after a 6 months storage-period (p<0.05) and the ones filled with AH Plus/gutta-percha presented a tendency to lower values of the push-out test, although not statistically significant. For both materials, dentin bond strength of the specimens filled by means of lateral condensation remained stable throughout the experimental periods. CONCLUSION: Under the limitations of the current study, it can be concluded that the thermocompaction technique and the storage time can influence push-out bond strength when used with methacrylate-based sealers.

Effect of methacrylated-based antibacterial monomer on orthodontic adhesive system properties.

INTRODUCTION: Antibacterial adhesives were developed to reduce the incidence of white spot lesions in orthodontic patients. Compounds that contain triazine are known as effective antibacterial agents. The aims of this study were to develop an experimental orthodontic adhesive containing 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAT) and to characterize it. METHODS: TAT was added in 3 concentrations (10%, 15%, and 20%) to the experimental orthodontic adhesive. Antibacterial activity was assayed by brain-heart infusion broth dilution against Streptococcus mutans. The degree of conversion was measured using Fourier transform infrared spectroscopy, and solvent degradation was evaluated by Knoop microhardness before and after immersion in ethanol for 2 hours. The shear bond strength of metal brackets bonded to bovine enamel surface was assessed. RESULTS: All experimental adhesives reduced bacterial growth. The addition of 15% and 20% TAT increased the degree of conversion compared with the control group (0%) and the 10% group. All groups showed a decrease in hardness after ethanol immersion, and there was also a decrease in the percentage of variation of Knoop hardness in the experimental adhesives containing TAT, whereas the shear bond strength increased. CONCLUSIONS: Orthodontic adhesives containing TAT are promising antibacterial materials, especially those with 15% and 20% TAT.

Caregivers' attitudes regarding oral health in a long-term care institution in Brazil.

BACKGROUND AND OBJECTIVE: The number of elderly living in long-term care (LTC) institutions has been increasing in many countries. The objective of this study was to evaluate the caregivers' attitudes and considerations regarding oral health and oral health practices in an LTC institution in Porto Alegre, Brazil. MATERIALS AND METHODS: The population comprised the caregivers (n = 27) at an LTC in Porto Alegre, Brazil. Participants answered a questionnaire assessing the time of work at the LTC, number of elderly under their responsibility, their previous training to perform general and oral healthcare, availability of oral hygiene supplies and oral hygiene tasks they performed. RESULTS: A total of eighteen (75%) and 23 (95.8%) of the caregivers answered they performed teeth and denture brushing as part of their routine. When asked about performing hygiene of the mucosa with gauze, 21 (87.5%) participants stated that they did so. However, when asked if they would motivate the independent elderly to perform oral hygiene, only 10 (41.7%) of the caregivers responded positively. CONCLUSION: Caregivers' oral health practices are in accordance with good oral health methods and are not associated with difficulties in performing oral hygiene. However, the high number of elderly people in their care could possibly overwhelm caregivers' practices. Future qualitative assessment of these issues is needed.

Influence of endodontic irrigants on resin sealer bond strength to radicular dentin.

The present study evaluated the influence of 2% chlorhexidine and 2.5% sodium hypochlorite on the resin sealer/dentin interface bond strength of AH Plus/gutta-percha and Epiphany/Resilon. Seventy-two extracted bovine incisors were randomly distributed into 6 groups according to irrigant and sealers: G(S+AH)=physiologic saline solution+AH Plus/gutta-percha; G(S+Ep)=physiologic saline solution+Epiphany/Resilon; G(H+AH)=2.5% sodium hypochlorite (NaOCl)+AH Plus/gutta-percha; G(H+Ep)=2.5% NaOCl+Epiphany/Resilon; G(C+AH)=2% chlorhexidine (CHX)+AH Plus/gutta-percha; and G(C+Ep)=2% CHX+Epiphany/Resilon. After 7 days at 37°C and 100% humidity, the roots were cut transversally on the long axis of the tooth in 0.8 mm (±0.09)-thick slices; these slices were then subjected to the push-out test. Data were analyzed using a 2-way ANOVA and Tukey tests at 5% significance. The AH Plus/gutta-percha groups showed significantly higher bond strength than the Epiphany/Resilon groups, regardless of the irrigant used (p<0.001). Sodium hypochlorite adversely affected bond strength in the AH Plus group, whereas chlorhexidine did not influence the push-out bond strength of either sealer (p<0.05). Two percent chlorhexidine did not adversely affect the bond strength of the sealers, whereas 2.5% sodium hypochlorite solution damaged AH Plus/gutta-percha bond strength.

Influence of 2-hydroxyethyl methacrylate concentration on polymer network of adhesive resin.

PURPOSE: To evaluate the effect of variations in 2-hydroxyethyl methacrylate (HEMA) concentrations in an experimental comonomer blend on degree of conversion, water sorption, solubility, and ultimate tensile strength of adhesive resin. MATERIALS AND METHODS: The effect of HEMA content (0, 15, 30, and 50%wt - control, G15, G30, and G50 groups, respectively) was tested in an experimental comonomer blend of bis-GMA, bis-EMA, TEG-DMA, and HEMA. The degree of conversion, polymerization rate, ultimate tensile strength, water sorption, and solubility of the adhesive resin blends were determined. RESULTS: At 40 s of light activation time, groups G30 and G50 showed a decrease of 30% and 61%, respectively, in degree of conversion compared to control. Water sorption and solubility differed for all groups, and was statistically higher in G50. For ultimate tensile strength, the control and G15 groups showed statistically higher values than the other groups (p < 0.05). CONCLUSION: Higher HEMA content increases dental adhesive resin degradation.

Influence of a peracetic acid-based immersion on indirect composite resin.

The aim of this study was to evaluate the influence of immersion in a 0.2% peracetic acid-based disinfectant on the three-point flexural strength, water sorption and water solubility of an indirect composite resin. Specimens were produced according to ISO 4049:2000 specifications and were divided in two groups: Control group, with no disinfection and Disinfected group, with three 10 min immersions in the peracetic acid intercalated with 10 min immersions in sterile distilled water. All evaluations were conducted in compliance with ISO specifications. Three-point flexural strength, water sorption and solubility of indirect composite resin before and after immersion showed no statistical significant differences (p > 0.05) and met ISO standard requirements. Immersion in peracetic acid solution showed no influence in indirect composite resin tested properties.

Niobium containing bioactive glasses as remineralizing filler for adhesive resins.

OBJECTIVE: The aim of this study was to incorporate sol-gel-derived bioactive glass as filler into experimental adhesive resins and evaluate the influence of glass composition on the physicochemical and biological properties of the developed adhesives. MATERIALS AND METHODS: Sol-gel particles were produced with or without the addition of niobium (BAGNb or BAG, respectively). The produced particles were incorporated (2wt%) into experimental adhesive resins formulated with 66wt% bisphenol A-glycidyl methacrylate and 33wt% hydroxyethyl methacrylate. Ethyl dimethyl-4-aminobenzoate and camphorquinone were used as photoinitiator system. Two experimental groups were produced: ABAGNb and ABAG. The adhesive without particles was used as control (ACG). The materials were tested for their degree of conversion, softening in solvent, and cytotoxicity. The mineral deposition was analyzed by Raman spectroscopy. Flexural strength and immediate and 1-year microtensile bond strength were evaluated. RESULTS: No statistical difference was found in degree of conversion. ABAGNb showed reduced softening and higher mineral deposition than ACG and ABAG after 28 days. ABAG and ABAGNb resulted in higher cell viability and lower flexural strength when compared to ACG. After 1-year, ABAGNb and ABAG presented statistically significant lower µTBS values. SIGNIFICANCE: Sol-gel-derived bioactive glasses promoted increased mineral deposition and cell viability for experimental adhesives with increased phosphate content and longitudinal µTBS values for the ABAGNb group. These results suggest the potential of the studied particles to be applied as bioactive fillers for dental adhesives. Reductions in longitudinal µTBS and flexural strength, however, were observed for both glasses compositions and must be considered.

Wollastonite as filler of an experimental dental adhesive.

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 ß-CaSiO3 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.

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

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 (CeO2) and investigate the effects of different loadings of CeO2 on their radiopacity and degree of conversion for the first time. CeO2 was characterized by X-ray diffraction analysis, Fourier transforms infrared spectroscopy, and laser diffraction for particle size analysis. Experimental dental adhesives were formulated with CeO2 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 CeO2 in the polymerized samples, degree of conversion, and radiopacity. CeO2 presented a monoclinic crystalline phase, peaks related to Ce-O bonding, and an average particle size of around 16 µm. CeO2 was dispersed in the adhesive, and the addition of these particles increased the adhesives' radiopacity (p < 0.05). There was a significant decrease in the degree of conversion with CeO2 loadings higher than 1.44 vol.%. However, all materials showed a similar degree of conversion in comparison to commercially available adhesives. CeO2 particles were investigated for the first time as a promising compound to improve the radiopacity of the dental adhesives.

Mineral deposition promoted by resin-based sealants with different calcium phosphate additions.

The aim of this study was to evaluate the influence of different calcium phosphates (CaPs) on the physical, biological, and remineralizing properties of experimental resin-based sealants (RBSs). Triethylene-glycol dimethacrylate (90wt%) and bisphenol A-glycidyl methacrylate (10wt%) were used to produce resin-based sealants. Hydroxyapatite (SHAp), α-tricalcium phosphate (Sα-TCP) and octacalcium phosphate (SOCP) were added to the sealants in a 10wt% concentration. One group without CaPs was used as the control group (SCG). The degree of conversion (DC) was assessed with Fourier-transformed infrared spectroscopy, whereas cytotoxicity was tested with the HaCaT keratinocyte cell line. The ultimate tensile strength (UTS) was used to assess the mechanical strength of the experimental RBSs. Sealed enamel was used for colorimetric assay. Mineral deposition was assessed with Raman spectroscopy after 7, 14, and 28 days of sample immersion in artificial saliva. Scanning electron microscopy was used to analyze the surface morphology after 28 days of immersion. The addition of 10wt% of fillers significantly reduced the DC of sealants. SOCP groups showed reduced cell viability. Higher UTS was found for Sα-TCP and SHAp. The color analysis showed that SGC and demineralized teeth presented higher mismatches with the sound tissue. Mineral deposition was observed for SHAp and Sα-TCP after 7 days, with increased phosphate content and mineral deposits for SHAp after 28 days. RBS with the addition of 10% HAp promoted increased mineralization in vitro after 28 days, and did not affect cell viability, DC, mechanical properties, or RBS color in the enamel.

Influence of N-(2-hydroxyethyl)acrylamide addition in light- and dual-cured resin cements.

OBJECTIVE: To develop experimental light-cured (L) and dual-cured (D) resin cements containing N-(2-hydroxyethyl)acrylamide and evaluate the physicochemical and optical properties. METHODS: Experimental resin cements were formulated using bisphenol A-glycidyl dimethacrylate (70%) and 2-hydroxyethyl methacrylate (30%), in the control groups, and, bisphenol A-glycidyl dimethacrylate (70%) and N-(2-hydroxyethyl)acrylamide (30%). Polymerization kinetics were evaluated by differential scanning calorimetry (n = 3), softening in solvent (ΔKHN) evaluated by the difference of Knoop microhardness before (KHN1) and after (KHN2) ethanol solution immersion (n = 5), radiopacity in mmAl (n = 5), film thickness (n = 3) and color stability were evaluated. Mechanical properties as ultimate tensile strength (UTS) and micro-shear bond strength (µSBS) were analyzed immediately and after 6 months. Results were analyzed using ANOVA, Tukey's test and Student's t-test (α = 0.050). RESULTS: The LHEAA1 group had no statistical difference from the control group regarding polymerization kinetics, KHN1, ΔKHN and color stability (p > 0.050). In dual-cured cements, the acrylamide groups presented a lower degree of conversion and higher ΔKHN than the DHEMA0.6 group, which obtained a higher rate of polymerization (p < 0.050). There was no statistical difference in radiopacity and film thickness (p > 0.050). Dual-cured cements with N-(2-hydroxyethyl)acrylamide showed higher color change than methacrylates. Immediate mechanical properties were lower for acrylamide groups (p < 0.050), with higher hydrolytic stability. CONCLUSIONS: The addition of N-(2-hydroxyethyl)acrylamide negatively affected the properties of the dual-cured resin cements. LHEAA1 did not differ in physicochemical and optical properties from the control, with higher hydrolytic stability. CLINICAL SIGNIFICANCE: The results of the study indicate that acrylamides increased mechanical properties over time independently of the curing system mode, with more hydrolytic stability. The clinical performance of experimental resin cements should be evaluated.

In vitro evaluation of visible light-activated titanium dioxide photocatalysis for in-office dental bleaching.

The evaluation of the photocatalysis of visible light activated titanium dioxide employed in hydrogen peroxide (H2O2) was carried using seven H2O2 solutions (3.5 and 35%) and/or methylene blue (MB), with or without light irradiation (LI); the absorbance of MB was the bleaching indicator. Color analysis was performed on bovine teeth (n=12) using two different concentrations of H2O2, 6 and 35% associated with titanium dioxide (TiO2). Data were analyzed with one and two-way ANOVA, and significance level of p<0.05. Solutions containing MB, H2O2 at 3.5 or 35%, and TiO2, followed by LI, showed significant difference when compared with other groups. Greater MB reduction was found in 35% concentration. H2O2 35%+TiO2 gel showed no difference in comparison to control group. All groups for the color analysis assay showed ΔE higher than 3.3. In conclusion, TiO2 and H2O2 association is a promisor alternative for reducing the clinical time of in-office dental bleaching.

Nanoneedle-like zinc oxide as a filler particle for an experimental adhesive resin.

AIM: The aim of this study was to develop an experimental adhesive resin with nanoneedle-like zinc oxide (N-ZnO), an inorganic filler, that could avoid particle agglomeration and lead to a homogeneous stress distribution within the material and characterize it. MATERIALS AND METHODS: N-ZnO particles obtained by a thermal evaporation technique were characterized regarding size and surface area and added at 0 (control), 1, 2, 5, and 10 wt%, to an experimental adhesive resin. The following experimental adhesive resins' properties were assessed: radiopacity, contact angle to conditioned enamel and dentin, color, degree of conversion, flexural strength, resistance to degradation, and cytotoxicity. Statistical analysis was performed using one-way ANOVA and Tukey's post hoc test and paired Student's t-test. RESULTS: Particles presented a mean particle size of 40 nm and a specific surface area of 16 m2/g. N-ZnO10%showed an increased radiopacity when compared to N-ZnO0%. Contact angles were significantly higher for N-ZnO10%at enamel and N-ZnO2%, N-ZnO5%, and N-ZnO10%at dentin. All groups showed color change when compared to N-ZnO0%. Higher the N-ZnO concentration, lower the degree of conversion. There were no significant differences between the groups for flexural strength and resistance to degradation. The addition of N-ZnO showed no difference in cytotoxicity when compared to positive control, N-ZnO0%, and all groups showed higher values than negative control. CONCLUSIONS: N-ZnO possibly exceeded potential limitations due to particles' agglomeration and improved the transference and distribution of stress within the material. It could be effectively used as a filler for adhesive resins.

Boron Nitride Nanotubes as Filler for Resin-Based Dental Sealants.

The aim of this study was to evaluate the influence of boron-nitride nanotubes (BNNTs) on the properties of resin-based light-curing dental sealants (RBSs) when incorporated at different concentration. RBSs were formulated using methacrylate monomers (90 wt.% TEGDMA, 10 wt.% Bis-GMA). BNNTs were added to the resin blend at 0.1 wt.% and 0.2 wt.%. A Control group without filler was also designed. Degree of conversion, ultimate tensile strength, contact angle, surface free energy, surface roughness and color of the RBSs were evaluated for the tested materials. Their cytotoxicity and mineral deposition ability (Bioactivity) were also assessed. A suitable degree of conversion, no effect in mechanical properties and no cytotoxic effect was observed for the experimental materials. Moreover, the surface free energy and the surface roughness decreased with the addition of BNNTs. While the color analysis showed no difference between specimens containing BNNTs and the control group. Mineral deposition occurred in all specimens containing BNNTs after 7d. In conclusion, the incorporation of BNNTs may provide bioactivity to resin-based dental sealants and reduce their surface free energy.