Influence of irrigation protocols on the bond strength of fiber posts cemented with a self-adhesive luting agent 24 hours after endodontic treatment.

The aim of this in vitro study was to evaluate the influence of different irrigation protocols on the bond strength, at different root depths, of fiber posts cemented with a self-adhesive cement 24 hours after endodontic treatment. Fifty-six bovine incisor roots were endodontically prepared and separated into 7 groups (n = 8) according to irrigation protocols: group 1, sterile saline (control); group 2, chlorhexidine (CHX) gel 2% and saline; group 3, sodium hypochlorite (NaOCl) 5.25% and saline; group 4, CHX and saline (final irrigation with ethylenediaminetetraacetic acid [EDTA] 17%); group 5, NaOCl and saline (final irrigation with EDTA); group 6, CHX and saline (final irrigation with NaOCl and EDTA); and group 7, NaOCl (final irrigation with CHX and EDTA). No statistically significant difference was found among the groups. Within the limitations of this study, it can be concluded that the different irrigation protocols did not influence the bond strength of self-adhesive resin cement, which presented similar behaviors at the 3 root depths studied.

Effect of low-level laser therapy on odontoblast-like cells exposed to bleaching agent.

The aim of the present study was to evaluate the effect of low-level laser therapy (LLLT) on odontoblast-like MDPC-23 cells exposed to carbamide peroxide (CP 0.01%-2.21 µg/mL of H2O2). The cells were seeded in sterile 24-well plates for 72 h. Eight groups were established according to the exposure or not to the bleaching agents and the laser energy doses tested (0, 4, 10, and 15 J/cm(2)). After exposing the cells to 0.01% CP for 1 h, this bleaching solution was replaced by fresh culture medium. The cells were then irradiated (three sections) with a near-infrared diode laser (InGaAsP-780 ± 3 nm, 40 mW), with intervals of 24 h. The 0.01% CP solution caused statistically significant reductions in cell metabolism and alkaline phosphate (ALP) activity when compared with those of the groups not exposed to the bleaching agent. The LLLT did not modulate cell metabolism; however, the dose of 4 J/cm(2) increased the ALP activity. It was concluded that 0.01% CP reduces the MDPC-23 cell metabolism and ALP activity. The LLLT in the parameters tested did not influence the cell metabolism of the cultured cells; nevertheless, the laser dose of 4 J/cm(2) increases the ALP activity in groups both with and without exposure to the bleaching agent.

The effect of surface treatment and bonding procedures on the bond strength of silorane composite repairs.

OBJECTIVE: The aim of this study was to evaluate the effect of surface treatments and adhesive protocols on the microtensile bond strength of a low-shrinkage composite repair. MATERIALS AND METHODS: Ninety-six blocks of composite resin Filtek LS were prepared using a half-hourglass-shaped silicone matrix. The specimens were storage for 24 h in distilled water and were randomly divided into the experimental (6) and negative control (2) groups (n = 12) according to the surface treatment (diamond bur and aluminum oxide sandblasting) and adhesive protocol (none; Filtek LS adhesive; phosphoric acid + Filtek LS adhesive; and phosphoric acid + silane + Filtek LS adhesive). After the adhesive procedure, the specimens were fixed in an hourglass-shaped silicone matrix and the other half of the specimen was restored. Hourglass shaped specimens (n = 12) were used as positive control (cohesive strength of the resin). The microtensile bonding test was performed at a crosshead speed of 0.5 mm/min. The data were analyzed using ANOVA, Tukey's and Dunnett's tests (α = 0.05). RESULTS: The bond strength values were similar for all experimental groups, except the groups without adhesive application. None of the experimental groups presented results similar to the positive control group. CONCLUSIONS: The repair of silorane restorations is viable; nevertheless, the different bonding procedures tested were incapable to produce bond strengths similar to the cohesive strength of the material.

Influence of photo-curing distance on bond strength and nanoleakage of self-etching adhesive bonds to enamel and dentin.

OBJECTIVES: To assess the influence of light-curing unit tip distance on the microtensile bond strength (µTBS) and nanoleakage of self-etching adhesives to enamel and dentin. MATERIALS AND METHODS: Flat buccal surfaces were prepared on 198 bovine incisors. The teeth were randomly assigned into nine groups for µTBS (n = 8) and nanoleakage (n = 3) testing according to the adhesive system (Clearfil Protect Bond, Clearfil Tri-S Bond or One Up Bond F Plus) and distance from the light-curing tip (0, 3 or 6 mm). The bonded samples were tested in tension (0.5 mm/min) and nanoleakage was analyzed using SEM. RESULTS: Clearfil Protect Bond exhibited the highest tensile strength on both enamel and dentin. Leakage was higher in samples exposed at a distance of 6 mm on enamel and 0 mm on dentin. One Up Bond F Plus experienced the greatest amount of nanoleakage on both substrates. CONCLUSIONS: Light-curing unit distance did not influence the µTBS of the adhesives, but nanoleakage increased on enamel samples when photoactivation occurred at a distance of 6 mm.

Effect of light curing protocol on degree of conversion of composites.

OBJECTIVE: To evaluate the degree of conversion (DC) of two light-cured composites with different protocols of light curing. MATERIALS AND METHODS: One hundred and ninety two specimens (n = 8) were prepared (5 mm × 2 mm) according to experimental groups: two composite resins (Filtek Supreme and four seasons); three light curing protocols [20 s with the tip of the light curing unit (LCU) device touching composite surface (C); 20 s with the tip of the LCU at 8 mm distant from composite surface (D); and tip of the LCU at 8 mm distant from composite surface and polymerization time required to obtain a radiant exposure of 16 J/cm(2) (DS)]. Four LCUs (Bluephase 16i, Ultralume LED 5, XL 3000 and Optilux 501C) were used. DC of the bottom and top surface of specimens were measured using a FTIR spectrometer. Data were statistically analyzed by 3-way split splot ANOVA and Tukey's test (alpha = 0.05). RESULTS: The results showed that DC of the top surface was higher than the bottom at all experimental conditions (p < 0.0001). Overall, the curing at 8 mm of distance did not affect conversion rate on the top surface (p > 0.05), but bottom surfaces showed DC reduction (p < 0.05). The highest monomer conversion values were observed for C and DS situations. CONCLUSION: The distance between the LCU and material surface and radiant exposure can affect the DC. Polymerization at distance should be performed with curing units with higher light power and/or extended exposure time.

Evaluating antimicrobial, cytotoxic and immunomodulatory effects of glass ionomer cement modified by chitosan and hydroxyapatite.

OBJECTIVES: This study aimed to assess antimicrobial efficacy, cytotoxicity, and cytokine release (IL-1b, IL-6, IL-10, TNF-α) from human dental pulp stem cells (hDPSCs) of chitosan (CH) and hydroxyapatite (HAp)-modified glass ionomer cements (GIC). METHODS: GICs with varied CH and HAp concentrations (0 %, 0.16 %, 2 %, 5 %, 10 %) were tested against S. mutans for 24 h or 7 days. Antimicrobial activity was measured using an MTT test. Cytotoxicity evaluation followed for optimal concentrations, analyzing mitochondrial activity and apoptosis in hDPSCs. Cytokine release was assessed with MAGPIX. Antimicrobial analysis used Shapiro-Wilk, Kruskal-Wallis, and Dunnett tests. Two-way ANOVA, Tukey, and Dunnett tests were applied for hDP metabolism and cytokine release. RESULTS: CH 2 % and HAp 5 % significantly enhanced GIC antimicrobial activity, especially after seven days. In immediate analysis, all materials showed reduced mitochondrial activity compared to the control. After 24 h, CH demonstrated mitochondrial metabolism similar to the control. All groups exhibited mild cytotoxicity (∼30 % cell death). Only IL-6 was influenced, with reduced release in experimental groups. SIGNIFICANCE: CH 2 % and HAp 5 % were most effective for antibacterial effects. GIC-CH 2 % emerged as the most promising formula, displaying significant antibacterial effects with reduced hDPSC toxicity.

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.

Toxic effects of daily applications of 10% carbamide peroxide on odontoblast-like MDPC-23 cells.

BACKGROUND: bleaching has been widely studied, mainly due to the possible undesirable effects that can be caused by this esthetic procedure. The cytotoxicity of the bleaching agents and its components to pulp cells has been demonstrated in several researches. The aim of this study was to evaluate the toxic effects of successive applications of 10% carbamide peroxide (CP) gel on odontoblast-like cells. MATERIALS AND METHODS: Enamel-dentin discs obtained from bovine incisors were adapted to artificial pulp chambers (APCs). The groups were formed as follows: G1: Without treatment (control group); G2: 10% carbamide peroxide, CP (five applications/one per day); G3: 10% CP (one unique application); and G4: 35% hydrogen peroxide, HP (three applications of 15 min each). After treatment, cell metabolism (MTT), alkaline phosphatase (ALP) activity and plasma membrane damage (flow cytometry) were analyzed. RESULTS: Reductions in cell metabolism and alkaline phosphatase activity along with severe damage of the cytoplasmic membrane were noted in G2. In G3, no damage was observed, compared to the control group. Intermediary values of toxicity were obtained after 35% HP application. CONCLUSION: It can be concluded that one application of 10% CP did not cause toxic effects in odontoblast-like cells, but the successive application of this product promoted severe cytotoxic effects. The daily application of the bleaching agents, such as used in the at-home bleaching technique, can increase the damages caused by this treatment to the dental pulp cells.

Knoop hardness and effectiveness of dual-cured luting systems and flowable resin to bond leucite-reinforced ceramic to enamel.

PURPOSE: The aim of this study was to evaluate the Knoop microhardness and microshear bond strength (MSBS) of dual-cured luting systems and flowable resin bonded to leucite-reinforced ceramics and enamel. MATERIALS AND METHODS: Eighty bovine incisors were randomly divided into four groups per test (microhardness and microshear; n = 10) according to the bonding procedure: Excite DSC/Variolink, Clearfil SE Bond/Panavia F, Adper Scotchbond Multi-Purpose Plus/RelyX ARC, and Adper Single Bond 2/Filtek Z350 Flow. For the KHN measurement, the cement was applied on the enamel surface and light-cured through a ceramic disk (5 mm diameter × 1.2 mm thick). Five indentations were performed in each specimen and measured at HMV-2. For the microshear test, two cylinders of a leucite-reinforced ceramic (1 mm diameter × 2 mm height) were bonded to the enamel substrate in accordance with the bonding procedures previously established. One cylinder was tested 24 hours after cementation, and the other was subjected to thermocycling (2000 cycles) and then submitted to an MSBS test. The data from the hardness and bond strength tests were subjected to one- and two-way repeated-measures analysis of variance (ANOVA), respectively, and to Tukey's test (α= 0.05). RESULTS: Scotchbond/RelyX ARC presented higher values of bond strength, while Single Bond/Z350 Flow showed lower values. The thermocycling promoted a reduction in the bond strength values for all groups. Panavia F presented higher values of KHN, and the flowable resin presented the lowest. RelyX ARC and Variolink presented intermediate values on hardness evaluation. CONCLUSIONS: For ceramic cementation, dual-cured resin luting systems promoted more reliable bonding and microhardness values than the flowable resin.

A complete esthetic approach with multiple diastemata in anterior teeth: 1-year follow-up.

Anterior diastemata and discolored teeth may interfere with the harmony of a person's smile. This article presents a case involving multidisciplinary intervention for esthetic treatment utilizing integrated microabrasion, dental bleaching, and restorative solutions. The relevant aspects of etiology and treatment planning are discussed.

Effect of surface sealants on microleakage of Class II restorations after thermocycling and long-term water storage.

PURPOSE: To evaluate interface degradation leading to marginal microleakeage in Class II restorations that had received an application of surface sealant at the tooth/restoration interface or not. MATERIALS AND METHODS: Eighty bovine incisors were used, and the teeth were split obliquely, 10 mm from the amelodentinal proximal junction, and finished with water abrasive papers to obtain a smooth, flat incisal surface. Cavities were made to simulate Class II preparations (8 mm high, 4 mm wide and 1.5 mm deep), and the restorations were performed with a composite resin. Teeth were then randomly allocated into 8 groups according to the surface sealant (none, Fortify, Single Bond 2, or Scothbond MP Plus) and aging process (none or thermocycling and storage for 6 months). Microleakage was then evaluated using a dye penetration method immediately after the restoration or after aging. The samples were triturated and assessed by spectrophotometer. RESULTS: Microleakage was statistically similar in all groups when assessed immediately after the restorative procedure. After aging, teeth sealed with Fortify presented better results than the other groups. CONCLUSION: Aging causes interface degradation and increased microleakage. Surface sealant can reduce these effects and decrease microleakage in Class II restorations.

Effect of bleaching treatment and reduced application time of an antioxidant on bond strength to bleached enamel and subjacent dentin.

PURPOSE: To evaluate the influence of bleaching on bond strength to enamel and subjacent dentin, and to determine whether a reduced application time (1 min) of the antioxidizing agent can obviate the compromised bond strength after bleaching. MATERIALS AND METHODS: One hundred twelve bovine incisors were obtained, and the enamel and dentin surfaces were standardized to a thickness of 1 mm. The specimens were divided into two control groups (enamel and dentin without treatment) and 12 experimental groups (n = 10), based on the concentration of bleaching agents (carbamide peroxide 16% and hydrogen peroxide 35%), time interval between bleaching and restorative procedures (24 h; 24 h + sodium ascorbate (SA) 10%/1 min; 14 days), and substrate (enamel or dentin). All samples were submitted to the bleaching treatment on enamel. After the stipulated interval, a microshear test was performed. RESULTS: The bleaching treatment compromised the bond strength to the enamel when the restoration was performed 24 h after the end of bleaching. The bond strength to dentin was not affected by bleaching. CONCLUSIONS: The SA 10% application for 1 min obviates the detrimental effect of bleaching on bond strength. The bleaching performed on enamel does not affect the bond strength to the subjacent dentin.

Evaluation of dentin hardness and bond strength at different walls of class II preparations.

PURPOSE: The aim of this study was to evaluate the Knoop hardness number (KHN) of dentin and the microtensile bond strength (microTBS) at different walls of MOD preparations, and the correlation between microTBS and the KHN of dentin. MATERIALS AND METHODS: Human molars with MOD preparations were allocated into 3 groups according to the preparation wall (axial, gingival, pulpal). Each tooth was sectioned into halves, resulting in two similar preparation walls: one was used for measuring the KHN of dentin and the other for microTBS testing. Flat surfaces of the respective walls were obtained by cutting away adjacent walls. For the KHN measurement, twelve indentations were performed along the preparation wall (50 g/15 s). For microTBS testing, specimens were distributed into 3 groups according to the adhesive system (Adper Single Bond Plus/SB, Clearfil SE Bond/SE, Adper Prompt/AP). Composite blocks were built over surfaces; specimens were sectioned (3 slabs/wall) and trimmed to an hourglass shape (1 mm(2)). RESULTS: The KHN of dentin walls was significantly different (ANOVA/Tukey); pulpal wall > axial wall > gingival wall. The effect of preparation walls on microTBS was dependent on the bonding system (2-way ANOVA/Tukey's test). SB had higher bond strength than the other systems at the gingival wall; and higher than SE at the axial wall. At the pulpal wall, SE presented a higher mean compared to AP. A significant negative correlation between microTBS and KHN was observed at the gingival wall. CONCLUSION: It could be concluded that dentin structure can affect bond strengths, but the impact of the substrate varies according to the type of adhesive system.

Effect of the diffusion of bleaching agents through enamel on dentin bonding at different depths.

PURPOSE: To evaluate the influence of two concentrations of bleaching agents applied over enamel surfaces on the dentin bonding at different depths. METHODS: Twenty-four bovine incisors were sectioned, obtaining three fragments per tooth (4x4 mm). Each fragment presented a 0.7 mm enamel thickness; and the dentin thickness varied according to the experimental group: 0.5 mm, 1 mm or 1.5 mm. Fragments from each dentin-thickness were allocated into three groups (n=8): G1: Control (no bleaching); G2: 16% carbamide peroxide (6 hours/14 days); G3: 35% hydrogen peroxide (three 15-minute treatments). 24 hours after enamel bleaching, the adhesive system was applied and dentin surfaces were restored with resin composite cylinders (2 mm diameter and 1 mm height). The micro-shear testing was performed immediately after restorative procedures, at a speed of 0.5 mm/minute until failure. Bond strength values, in MPa, were statistically analyzed (split-plot ANOVA/Tukey alpha=0.05). RESULTS: Means obtained were: G1-0.5 mm: 13.5, G1-1 mm: 9.48, G1-1.5 mm: 9.01; G2-0.5 mm: 9.64, G2-1 mm: 9.44, G2-1.5 mm: 9.27; G3-0.5 mm: 11.68, G3-1 mm: 11.64, G3-1.5 mm: 7.63. Regardless of the dentin thickness, bleached groups presented bond strengths similar to that of control groups. Nevertheless, significant differences among dentin depths were detected (P=0.02); and the lowest bond strength was observed on the deepest dentin (1.5 mm). The diffusion of bleaching agents through enamel surfaces did not affect the bond strength to dentin, which is highly dependent on the morphology/depth of the substrate.

Effects of 3% sodium ascorbyl phosphate on the hardness and bond strength of human enamel bleached with 10% carbamide peroxide.

For this study, 120 fragments obtained from human third molars were randomly separated into 12 groups (n = 10). Four groups were used for measuring the Knoop hardness number (KHN) of enamel, while the other eight were used for testing the microtensile bond strength (muTBS) of two adhesive systems (Single Bond and Prime & Bond NT). All groups presented statistically similar KHN values. According to bond strength results, bleached enamel without antioxidant application demonstrated the lowest values of all groups. Based on these results, it could be concluded that the bleaching agents used in the present study (with or without sodium ascorbyl phosphate) did not affect human enamel hardness and that sodium ascorbyl phosphate is able to reverse the compromised bonding in bleached human enamel.

Chemistry of novel and contemporary resin-based dental adhesives.

The chemistry of resin-based dental adhesives is critical for its interaction with dental tissues and long-term bonding stability. Changes in dental adhesives composition influences the materials' key physical-chemical properties, such as rate and degree of conversion, water sorption, solubility, flexural strength and modulus, and cohesive strength and improves the biocompatibility to dental tissues. Maintaining a suitable reactivity between photoinitiators and monomers is important for optimal properties of adhesive systems, in order to enable adequate polymerisation and improved chemical, physical and biological properties. The aim of this article is to review the current state-of-the-art of dental adhesives, and their chemical composition and characteristics that influences the polymerisation reaction and subsequent materials properties and performance.

Bis(4-methyl phenyl)iodonium as an alternative component to diphenyliodonium in camphorquinone-based ternary initiating systems.

OBJECTIVE: To evaluate the influence of different co-initiators (diphenyliodonium hexafluorophosphate - DPI - and bis(4-methyl phenyl)iodonium hexafluorophosphate - BPI) on chemical and mechanical properties of resins. METHODS: Nine experimental resins (50% Bis-GMA and 50% TEGDMA, w/w) with 60 wt% filler particles were formulated. The initiating system used was camphorquinone (CQ-1 mol%) and ethyl dimethylaminobenzoate (EDAB-2 mol%). Experimental groups were established according to DPI and BPI quantities (0.25, 0.5, 0.75, and 1 mol%). The control group was a resin containing only CQ-EDAB. Light transmission through the resin during polymerisation was analysed with a UV-vis spectrophotometer. Real-time polymerisation of the systems was evaluated using an FTIR spectrometer. Real-time polymerisation shrinkage strain was evaluated, and the flexural strength and modulus of materials were obtained by 3-point bending. Experimental groups were statistically analysed by Analysis of Variance and Tukey's test (α = 0.05). Dunnett's test was applied to compare experimental groups with control. RESULTS: Light transmission rapidly increased initially for resins containing DPI or BPI. After 30 s cure, the irradiance on the lower surface of resin specimens was similar for all groups. After 10 s of light irradiation, groups containing DPI and BPI had higher conversion than the control. However, conversion after 120 s post-irradiation was similar for all groups. The rate of polymerisation, shrinkage strain, and the maximum strain rate were higher for groups containing DPI/BPI. The use of iodonium salts increased the flexural strength and flexural moduli of resins. SIGNIFICANCE: DPI and BPI increased resin reactivity similarly. Increased rate of polymerization influenced light transmission through the resin in the first seconds of polymerisation and increased resin shrinkage and rate of shrinkage, as well as flexural strength and moduli.

The influence of nanofillers on the properties of ethanol-solvated and non-solvated dental adhesives.

OBJECTIVES: The aim of this study was to evaluate the influence of different concentrations of nanofillers on the chemical and physical properties of ethanol-solvated and non-solvated dental adhesives. MATERIALS AND METHODS: Eight experimental adhesives were prepared with different nanofiller concentrations (0, 1, 2, and 4 wt%) and 2 solvent concentrations (0% and 10% ethanol). Several properties of the experimental adhesives were evaluated, such as water sorption and solubility (n = 5, 20 seconds light activation), real-time degree of conversion (DC; n = 3, 20 and 40 seconds light activation), and stability of cohesive strength at 6 months (CS; n = 20, 20 seconds light activation) using the microtensile test. A light-emitting diode (Bluephase 20i, Ivoclar Vivadent) with an average light emittance of 1,200 mW/cm2 was used. RESULTS: The presence of solvent reduced the DC after 20 seconds of curing, but increased the final DC, water sorption, and solubility of the adhesives. Storage in water reduced the strength of the adhesives. The addition of 1 wt% and 2 wt% nanofillers increased the polymerization rate of the adhesives. CONCLUSIONS: The presence of nanofillers and ethanol improved the final DC, although the DC of the solvated adhesives at 20 seconds was lower than that of the non-solvated adhesives. The presence of ethanol reduced the strength of the adhesives and increased their water sorption and solubility. However, nanofillers did not affect the water sorption and strength of the tested adhesives.

Increased rates of photopolymerisation by ternary type II photoinitiator systems in dental resins.

To evaluate the effects of Type I and Type II photoinitiator systems on curing efficiency, degree of conversion (DC) and chemico-physical properties of resin based materials. A comonomer base containing 50%wt 2.2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (bis-GMA) and 50%wt triethyleneglycol dimethacrylate (TEGDMA) was formulated with either 0.5 or 1mol% of Type II camphoroquinone (CQ), Type I monoacylphosphine oxide (MAPO) or bis-acylphosphine oxide (BAPO) photoinitiators. The Type II system was either a binary (1: 2 CQ:amine) or ternary system (1: 2 CQ:amine + 0.5 mol% DPI). Degree and rate of polymerization was measured by Fourier Transform Infrared Spectroscopy (FTIR). Knoop micro-hardness prior to and following ethanol immersion was assessed. Flexural strength and modulus was measured under three-point bend test. Water sorption and solubility was also evaluated. The photoinitiator absorption spectra and the total absorbed energy per unit volume (Eabs) for 0.5mol% photoinitiator in each material was calculated. Despite the reduced total absorbed energy per unit volume for CQ based systems, ternary Type II system significantly improved curing efficiency (P < 0.05) compared to both Type I photoinitiators and degree of conversion compared to MAPO only, whilst exhibiting comparable mechanical and physical properties compared to both Type I based materials at equivalent molar concentrations of photoinitiator (P > 0.05). Ternary Type II systems is an efficient alternative to improve the polymerization of resin materials, promoting similar or even better properties than Type I initiators. DPI can increase the reactivity of CQ systems and promote polymerization rates superior than Type I photoinitiators.

Influence of light-curing unit on the network structure and mechanical properties of model resin cements containing diphenyliodonium compared with a commercial reference.

OBJECTIVE: To evaluate the effects of dyphenyliodonium hexafluorophosphate (DPI) on crosslink density (CLD), flexural strength (FS), and flexural modulus (FM) of a light-cured experimental resin cement compared with a commercial dual-cured cement. MATERIALS AND METHODS: Bis-GMA combined with TEGDMA (50-50%) was used as resin matrix. Silanated barium-aluminum-silica glass was used as inorganic filler. Camphorquinone (CQ) - 1 mol%, 2-(dimethylamino)ethyl methacrylate (DMAEMA) - 2 mol%, and two concentrations of DPI (0 or 0.5 mol%) were used as the photoinitiator system. Two light-curing units (LCUs) were used (a single-peak (Radii-Cal) and a polywave (Bluephase)). The CLD was indirectly assessed in a softening test by Knoop hardness indentation; FS and FM were measured by means of a three-point bending test. RESULTS: DPI positively influenced Knoop hardness when compared with experimental resin without DPI. The flexural strength of experimental cements was lower than that found with Variolink II. The crosslinking density (obtained by reduction of Knoop hardness) of cement with 0.5% DPI was similar to that of dual - cured Variolink II. CONCLUSIONS: DPI showed an improvement in some of the properties tested but was inferior to the commercial dual-cured resin cement. The LCUs had no influence on the flexural strength of the resin cements.