Search

Objective: To measure degree of conversion (DC) of a flowable composite, microtensile bond strength (MTBS) to dentine in the snow‐plow technique with/without preheating and temperature in the preheated composite. Materials and Methods: For DC, snow‐plow specimens of Filtek Ultimate Flowable (Flow) and Filtek Bulk Fill (Bulk) (3M) were prepared by light‐curing composites simultaneously in standardized molds while in control groups light‐curing was separate. DC of Flow was measured using micro‐Raman spectroscopy. For MTBS, specimens were prepared on dentine of human extracted molars by simultaneous (snow‐plow) or separate (control) light‐curing. MTBS was measured using a universal testing machine after 24 h and 6 months. Data were analyzed using ANOVA with Tukey's post hoc (α = 0.05). Results: Increased curing time significantly increased DC in snow‐plow from 13.4% ± 11.6% (10 s) to 31.8% ± 4.4% (40 s) albeit significantly lower than controls (p < 0.05). Preheated Bulk improved conversion in snow‐plow (44.3% ± 1.7%) and control (50.5% ± 2.6%) (p < 0.05). No significant differences occurred in MTBS between groups (p > 0.05). MTBS values ranged between 66.7 ± 8.4 MPa (snow‐plow group_21°C_baseline) and 54.1 ± 15.8 MPa (control_21°C_long‐term). Temperature in the preheated Bulk dropped to ~38°C after 30 s. Conclusions: Snow‐plow technique, irrespective of preheating, resulted in lower DC of Flow than separate light‐curing of composite increments. Snow‐plow, irrespective of preheating, resulted in similar initial and long‐term MTBS to dentine. Clinical Significance: Clinicians with preference for flowable composite liners in Class II restorations should be aware that the snow‐plow technique of simultaneous light‐curing of flowable and bulk‐fill composite increments affects monomer‐to‐polymer conversion, albeit no effect on immediate, and long‐term bonding to dentine was detected. Preheating sculptable bulk‐fill composite improves conversion of the flowable liner in the snow‐plow technique but has no detectable effect on bond strength to dentine. [ABSTRACT FROM AUTHOR]

Objective: To analyze the effects of factors 'composite,' 'medium,' and 'time' on color, translucency, and sorption/solubility of sculptable universal composites for enamel layering upon immersion in colored beverages. Materials and methods: Disk‐shaped specimens, 10 mm in diameter and 2 mm thick (n = 5/group), of ultrafine, hybrid composite Essentia (GC), microhybrid Gaenial Anterior (GC), nanofilled Filtek Ultimate Enamel and Body (3M ESPE) were immersed in red wine, coffee, or distilled water for 15 days. CIELab color coordinates were measured and CIEDE2000 (∆E00) and Translucency Parameter differences (∆TP00) were calculated. Sorption and solubility were determined according to ISO 4049:2009. Data were analyzed using the analyses of variance and Tukey's post‐hoc test (α = 0.05). Results: Essentia and Gaenial exhibited the lowest and the highest staining‐dependent color differences, with mean ∆E00 range of 1.7–6.1 and 5.1–11.3, respectively (p < 0.05). ∆TP00 was more pronounced in wine than in coffee (p < 0.05). Sorption and solubility varied between 9.8 and 15.3 μg/mm3 and −1.6 and −5.4 μg/mm3, respectively, with positive correlation between ∆TP00 and sorption (p = 0.005). Conclusions: Total color and translucency differences of sculptable composites for enamel layering were material‐, time‐ and medium‐dependent. Translucency differences positively correlated with sorption. Overall, the ultrafine, hybrid composite exhibited the best results in terms of color stability, sorption and solubility. Clinical significance: Clinicians should be aware of differences in color stability of sculptable composites for enamel layering as these are directly exposed to discoloration in the oral environment and are directly related to patients' long‐term satisfaction and restoration longevity. Ultrafine, hybrid composite may be preferred due to better color stability, lower sorption and solubility compared to nanofilled and microhybrid composites evaluated in this study. [ABSTRACT FROM AUTHOR]

Objective: To analyze local shrinkage patterns in terms of surface shrinkage strains and z-axis displacements in a novel self-adhering composite and a conventional flowable composite using three-dimensional digital image correlation. Method and Materials: Seven samples of each material were prepared in cylindrical Teflon molds 5 mm in diameter and 2 mm thick. The surface of the composites facing the cameras was sprayed with a fine layer of black paint. The unsprayed surface of each sample, opposite the one facing the cameras, was light cured for 40 seconds using a light-emitting diode unit. Digital images were taken immediately before and after light curing. Shrinkage was calculated as von Mises strains, and z-axis displacements were measured in microns. The data were statistically analyzed using two-way ANOVA at α = .05. Results: No significant difference in strain was observed between the two materials (P > .05). Strain distribution was nonhomogenous-- the outer segments showed significantly higher strains than central parts in each material (P < .05). The opposite was observed for z-axis displacements--significantly greater displacements were found in central parts compared to the outer segments (P < .05). Conclusion: Different shrinkage vectors across the surface of the tested flowable composites showed predominant in-plane shrinkage of the outer surface segments and out-of-plane shrinkage of the inner segments. These complex local deformation patterns in composite materials indicate zones of different types of forces exerted on the tooth-restoration interface in situ. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the study was to compare the ratio of carbon-carbon double bonds (RDB) of two adhesive systems cured by five different light-curing units (LCUs) using micro-Raman spectroscopy. Materials and Methods: Ten samples of an etch-and-rinse (Excite), a two-step self-etching adhesive system (AdheSE) - ie, primer and bond mixed - and AdheSE Bond only were prepared and cured with one of the following LEDs: Elipar Freelight2; Bluephase; SmartLite; Coltolux, each for 10 s; or a conventional halogen Prismetics Lite for 10 s or 20 s. Micro-Raman spectra were obtained from uncured and cured samples of all three groups to calculate the RDB. Data were statistically analyzed using ANOVA. Results: The mean RDB values were 62% to 76% (Excite), 36% to 50% (AdheSE Primer+Bond) and 58% to 63% (AdheSE Bond). At 20 s, Prismetics Lite produced significantly higher RDB in Excite than the other LCUs and Prismetics Lite at 10 s (p < 0.05). Prismetics Lite at 20 s and Elipar produced comparable RDB values of AdheSE Bond and AdheSE Primer+Bond (p > 0.05). Excite showed significantly higher RDB values than AdheSE (p < 0.05) whilst AdheSE Bond showed significantly higher RDB than AdheSE Primer+Bond (p < 0.05). Conclusion: The etch-and-rinse adhesive cured with the halogen LCU for 20 s gave higher conversion than LED LCUs or halogen for 10 s curing time. The highest intensity LED [Elipar] produced higher or comparable conversion compared to the lower intensity LED LCUs for the same curing time. The etch-and-rinse adhesive showed higher RDB than the self-etching adhesive system. The presence of the primer in the self-etching adhesive compromised polymerisation. [ABSTRACT FROM AUTHOR]

Objective: To determine color changes in bulk‐fill composite and universal composite restorations with dissimilar dentin replacement materials in extracted teeth after staining in red wine. Materials and Methods: Cylindrical, 4 mm deep, class I cavities were prepared in 140 human molars. Bottom 2 mm was restored with Biodentine (Septodont), everX posterior (GC) or experimental HAP inserts. Each dentin replacement material was covered with a 2‐mm layer of a universal composite Filtek Z250 or Z550 (3M ESPE) or Gradia Posterior (GC). Groups combining top composite layer and the underlying dentin replacement were designated as "composite_dentin replacement." Filtek Bulk Fill (3M ESPE) and Tetric EvoCeram Bulk Fill (Ivoclar Vivadent) were placed as a single 4‐mm layer. Color measurements were performed using Vita Easyshade 4.0 (Vita Zahnfabrik) initially and after 48‐hours storage in red wine at 37°C. Results: Color differences (ΔEoo) ranged between 2.1 ± 0.7 (Z250_HAP) and 7.8 ± 1.1 (Z550_everX). EverX resulted in higher ΔEoo of the overlying composite than HAP (P < .001) and Biodentine (P = .006). Generally, ΔEoo was affected more by decreasing lightness (ΔL′) than changes in chroma (ΔC′). Conclusions: EverX resulted in higher ΔEoo of the restoration than Biodentine and experimental HAP after staining in red wine. No significant differences in ΔEoo may be expected in different composites with the same underlying dentin replacement material. The same was generally true for bulk‐fill and universal composites. Clinical Significance: Similar extent of color changes may be expected in bulk‐fill and universal composites. Highly translucent everX might exhibit greater color differences irrespective of the capping composite than non‐translucent materials. Clinicians have a wider choice of composite materials to cover a particular dentin replacement material, for example, everX or Biodentine, as similar color differences may be expected in various overlying composite brands. [ABSTRACT FROM AUTHOR]

The aim of this study was to optimize the concentration of 2,4,6-trimethylbenzoylthphenylphosphine oxide (Lucirin® TPO) in unfilled and filled composite resins in relation to the degree of conversion (DC). Increasing concentrations of Lucirin®TpO between 0.05-- 4.97 wt% were added to equimolar mbtaires of Bis-GMA/TEGDMA. Filled resins contained 75 wt% fillers. Standardized samples were cured using a polywave LED light-curing unit (bluephase® G2, Ivoclar Vivadent). Increased initiator concentrations increased logarithmically the DC of unfilled and flllsd resins The DC of unfilled resins was in the range of 73--91% at the top and 63--81% at the bottom surfaces and that of filled resins was in the range of 53--81% at the top and 47--70% at the bottom surfaces. The DC in unfilled and filled resins reached a plateau at 1 03 wt% and 1.50 wt% Lucirin® TPO, respectively. Fillers significantly reduced conversion but had no effect on the logarithmic relationship between initiator concentration and the DC. [ABSTRACT FROM AUTHOR]

Background/purpose: Monomer to polymer conversion is important for optimal mechanical properties and resistance to biodegradation of resin-based materials. Incomplete conversion of fissure sealants may account for lower retention and fracture resistance as well as elution of teachable components. The objective of this study was to determine the degree of conversion (DC) of three fissure sealants cured using a conventional quartz-tungsten halogen (QTH) or a high power light-emitting diode (LED) Light-curing unit using micro-Raman spectroscopy. Materials and methods: Delton Opaque and Helioseal Opaque and Helioseal Clear were applied to 60 noncarious permanent molars and cured with the QTH or the LED. Micro-Raman spectra were obtained from the top and the bottom surface of each sample. Three-way analysis of variance (α = 0.05) was used for data analysis. Results: Top surface DC values were significantly higher than bottom surface in each material irrespective of the light-curing unit (P < 0.05). LED produced significantly higher DC values than the QTH with all three materials (P < 0.05). Helioseal Opaque showed significantly lower DC values than Helioseal Clear (P < 0.05). DC values for Delton and Helioseal Clear were comparable (P>0.05). Conclusion: Higher DC is achieved with the LED with less exposure time compared with the conventional QTH at top and bottom surfaces of the three fissure sealants, although a lower conversion may be expected in opaque materials. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To determine the degree of conversion (DC) over 48h post-curing of resin mixtures containing trimethylbenzoyl-diphenylphosphine oxide (TPO) initiator cured by a polywave or a monowave LED light-curing unit (LCU). Methods: In resin mixtures based on equal weight percent (wt%) of BisGMA and TEGDMA the following initiators were added: 0.2wt% camphorquinone (CQ)+0.8wt% ethyl-4-dimethylaminobenzoate (EDMAB) (Group 1); 1wt% TPO (Group 2) and 0.1wt% CQ+0.4wt% EDMAB+0.5wt% TPO (Group 3). Half of the samples in each group (n =5) were cured using a polywave (bluephase® G2, Ivoclar Vivadent) or a monowave LED LCU (bluephase®, Ivoclar Vivadent). The DC was measured using micro-Raman spectroscopy within 5min and then 1, 3, 6, 24 and 48h post-irradiation. The data were analysed using general linear model and two-way ANOVA for the factors ‘time’, ‘material’, ‘surface’ and ‘LCU’ at α =0.05. Results: The initial DC values obtained upon light curing remained similar over a 48h period. bluephase® G2 produced the highest DC in Group 2 followed by Group 3, and Group 1. bluephase® resulted in the highest DC in Group 1, followed by Group 2 and Group 3 (p <0.05). Conclusions: Unfilled resin materials containing both TPO– and CQ–amine initiators are effectively cured using bluephase® G2. Resin mixture with the same wt% of initiators is better cured when TPO is the only initiator, compared to CQ–amine only or combined TPO and CQ–amine system. After initial light cure, no additional conversion of uncured monomers was detected in an unfilled resin material over 48h at 37°C. [Copyright &y& Elsevier]

Statement of the Problem: Light-curing of resin-based composites (RBCs) is associated with temperature increase in the pulp chamber, which may have a detrimental effect on the vital pulp. Purpose: The purpose of the study was to evaluate temperature changes of silorane-, ormocer-, and dimethacrylate-based RBCs at the bottom surface of the RBC and in the pulp chamber roof dentin (PCRD) during curing. Materials and Methods: In part A, temperatures were measured for Filtek LS (3M ESPE, St. Paul, MN, USA), Admira (Voco GmbH, Cuxhaven, Germany), and Herculite XRV (Kerr Corp., Orange, CA, USA) with a high-power light-emitting diode (LED) unit by placing thermocouples in contact with the bottom surface of the material in standardized acrylic molds. In part B, temperature changes in PCRD were measured in extracted molars during light-curing of adhesives and RBCs in 2-mm-deep cavities with a remaining dentin thickness (RDT) of 1 mm. Results: Filtek LS showed a different temperature curve compared with Admira and Herculite XRV. Significantly higher temperatures were recorded for Filtek LS ( p < 0.001) than for Admira and Herculite XRV in acrylic molds. Temperature rises recorded in PCRD for adhesives and RBCs were between 4.1 and 6.4°C. No significant differences in PCRD temperatures were found between the three groups during adhesive curing and RBC curing ( p > 0.05). Conclusions: Filtek LS showed a different heat-generation pattern from and significantly higher temperatures than Admira and Herculite XRV when the materials were tested in acrylic molds. Similar temperatures were recorded in the PCRD during curing of adhesives and RBCs. CLINICAL SIGNIFICANCE Although a substantial temperature rise in the bulk material occurred during light-curing of the three resin-based composites, a remaining dentin thickness of 1 mm caused a significant reduction in pulp chamber roof dentin temperatures. Temperatures measured in the pulp chamber roof dentin corresponding to the zone occupied by the postmitotic odontoblast layer were not statistically different for the three types of resin-based composites. [ABSTRACT FROM AUTHOR]

Objective To study the effect of a low-shrinkage methacrylate monomer and monoacylphosphine oxide photoinitiator on color, translucency, and color stability of model resin-based composites (RBCs). Methods Four micro-hybrid RBCs were prepared containing barium-glass fillers in bisphenol A-glycidyl-methacrylate (BisGMA) and triethyleneglycol-dimethacrylate (TEGDMA) or urethane-based low-shrinkage monomer FIT-852 (FIT; Esstech Inc.) and TEGDMA matrix. Camphorquinone (CQ)/amine or Lucirin TPO were used as photoinitiators. Commercial low-shrinkage RBCs (Charisma Diamond, Heraeus Kulzer and N’Durance, Septodont) and conventional RBCs (Tetric EvoCeram, Ivoclar Vivadent and Filtek Z250, 3M ESPE) were used as controls. Color and translucency were measured using Thermo Scientific Evolution (Thermo Fisher Scientific) and SpectroShade™ Micro (MHT Optic Research) spectrophotometers. Color stability was evaluated after immersion in black tea (pure, with milk or lemon) and distilled water. Data were analyzed using analyses of variance with Tukey's post-test ( α = 0.05). Results Photoinitiators had no significant effect on baseline color. Initially whiter FIT-based RBCs showed greater staining in all staining solutions than BisGMA-based RBCs. TPO-containing RBCs showed better color stability than CQ-containing RBCs irrespective of the base monomer. Tea and tea with lemon induced greatest color changes. Adding milk to tea significantly reduced material staining. Significance Urethane-based low-shrinkage monomer FIT and conventional BisGMA affected color, translucency and color stability of their respective RBCs. Despite being used in posterior teeth, low-shrinkage RBCs are expected to have favorable optical and esthetic properties. Manufacturers are urged to provide information on optical properties of monomers and monomer mixtures in their low-shrinkage RBCs to allow understanding of interaction with fillers and photoinitiators. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To study monomer elution from four resin-based composites (RBCs) cured with different light sources. Methods: Twenty-eight premolars were randomly allocated to four groups. Standardized cavities were prepared and restored with a nanohybrid (Filtek Supreme XT or Tetric EvoCeram), an ormocer (Admira) or a microhybrid RBC (Filtek Z250) which served as control. Buccal restorations were cured with a halogen and oral restorations with an LED light-curing unit. Elution of diurethane dimethacrylate (UDMA), Bisphenol A diglycidylether methacrylate (BisGMA), triethylene glycol dimethacrylate (TEGDMA) and 2-hydroxyethyl methacrylate (HEMA) was analyzed using high-performance liquid chromatography (HPLC) 1h to 28 days post-immersion in 75% ethanol. Data were analyzed using multivariate and repeated measures analysis of variance (α =0.05). Results: The greatest elution of UDMA and BisGMA occurred from Tetric EvoCeram and the least from Filtek Z250 (p <0.05). LED and halogen light-curing units gave similar results for all RBCs (p >0.05) except Tetric EvoCeram which showed greater elution for the LED unit (p <0.05). TEGDMA was below the limit of quantification. HEMA eluted in similar concentrations from Filtek Supreme and Tetric EvoCeram (p >0.05). Significance: : The two nanohybrid RBCs eluted more cross-linking monomers than the ormocer and the control microhybrid RBC. Continuous elution over 28 days indicates that RBCs act as a chronic source of monomers in clinical conditions. Light source may affect monomer elution since differences were found for one out of four RBCs. Mathematical models for elution kinetics of UDMA and BisGMA indicated two elution mechanisms. [Copyright &y& Elsevier]