Search

Objective: To evaluate the effects of preheating procedure and polymerization modes on degree of conversion (DC) of resin composites.Methods: Three different types of composites - a conventional (GrandioSO - [GSO]), a bulkfill (GrandioSO x-tra - [GSX]), and a thermoviscous bulkfill (VisCalor bulk - [VCB]) - were investigated. Three specimens were prepared for each combination of the variables (composite type*preheating procedure*polymerization mode). Photo-polymerization was performed using an LED operated in standard (SM), high power plus (HM), and x-tra power (XM) modes. DC was measured with Fourier Transform Infrared Spectroscopy after 5 min and 24 h post-irradiation. Furthermore, three-way analysis of variance followed by a Tukey test at a significance level of P SM > XM.Conclusion: Preheating generally exhibited favorable effects on the DC of all tested composites, with the most significant impact observed in VCB. Additionally, polymerization with x-tra power mode is not recommended to achieve a sufficient DC required for clinically acceptable restorations.Keywords: bulk fill composite; degree of conversion; FTIR; polymerization mode; preheating; thermoviscousity

Copyright of Selcuk Dental Journal is the property of Selcuk Dental Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: A few studies have investigated the effect of the activation mode of adhesive systems on bond strength of fiber posts to root canal dentin. This study investigated the push-out bond strengths of a glass fiber post to different root canal regions with the use of two adhesives with light- and dual-cure polymerization modes. Materials and Methods: In this in vitro study, 40 maxillary central incisors were decoronated at cement-enamel junction with 15 ± 1 mm root length. After root canal therapy and post space preparations, they were randomly divided into four groups. Post spaces were treated with four different adhesives: Excite, Excite Dual cure Single Component (DSC), self-etch adhesive (AdheSE), and AdheSE dual-cure. Then the fiber-reinforced composite (FRC) post, Postec Plus, was cemented with dual-cure resin cement, Variolink II. The roots were cut into three 2-mm-thick slices. Push-out tests were performed with a universal testing machine at a crosshead speed of 0.5 mm/min. The mode of failures was determined under a stereomicroscope. Data were analyzed by three-way analysis of variance (ANOVA) and Tukey test was conducted to compare post hoc with P < 0.05 as the level of significance. Results: The highest bond strength was obtained for AdheSE dual-cure (15.54 ± 6.90 MPa) and the lowest was obtained for Excite light-cure (10.07 ± 7.45 MPa) and only the bond strength between these two adhesives had significant difference (P = 0.02). Bond strength decreased from the coronal to the apical in all groups and this was significant in Excite (group 1) and AdheSE (group 3) (P < 0.001). In apical regions, bond strength of dual-cure adhesives was significantly higher than light-cure adhesives (P < 0.001). Conclusion: Push-out bond strength of fiber post to different regions of root canal dentin was affected by both adhesive systems and their polymerization modes.

Background: A few studies have investigated the effect of the activation mode of adhesive systems on bond strength of fiber posts to root canal dentin. This study investigated the push-out bond strengths of a glass fi ber post to different root canal regions with the use of two adhesives with light- and dual-cure polymerization modes. Materials and Methods: In this in vitro study, 40 maxillary central incisors were decoronated at cement-enamel junction with 15 ± 1 mm root length. After root canal therapy and post space preparations, they were randomly divided into four groups. Post spaces were treated with four different adhesives: Excite, Excite Dual cure Single Component (DSC), self-etch adhesive (AdheSE), and AdheSE dual-cure. Then the fiber-reinforced composite (FRC) post, Postec Plus, was cemented with dual-cure resin cement, Variolink II. The roots were cut into three 2-mm-thick slices. Push-out tests were performed with a universal testing machine at a crosshead speed of 0.5 mm/min. The mode of failures was determined under a stereomicroscope. Data were analyzed by three-way analysis of variance (ANOVA) and Tukey test was conducted to compare post hoc with P < 0.05 as the level of significance. Results: The highest bond strength was obtained for AdheSE dual-cure (15.54 ± 6.90 MPa) and the lowest was obtained for Excite light-cure (10.07 ± 7.45 MPa) and only the bond strength between these two adhesives had signifi cant difference (P = 0.02). Bond strength decreased from the coronal to the apical in all groups and this was significant in Excite (group 1) and AdheSE (group 3) (P < 0.001). In apical regions, bond strength of dual-cure adhesives was significantly higher than light-cure adhesives (P < 0.001). Conclusion: Push-out bond strength of fiber post to different regions of root canal dentin was affected by both adhesive systems and their polymerization modes. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To determine the shear bond strength to bovine dentin of dual-cured resin cements cured in different circumstances, the contraction stress and volumetric shrinkage in both polymerization modes, and to review the failure stress distribution at the cement–tooth interface with finite element analysis. Methods: The volumetric shrinkage of RelyX Unicem, Panavia F 2.0 and DC Core Automix was determined by mercury dilatometry. Polymerization contraction stress was determined using a constraint tensilometer set-up. For the shear bond strength test, cement discs on bovine root dentin (self-cured and dual-cured), composite discs cemented to dentin (self-cured and dual-cured), and dentin cemented to dentin (self-cured) specimens were fabricated. Specimens were stored in water for 24h (37°C, 100% humidity) and tested (crosshead speed 1mmmin−1). FE modeling of the specimens was carried out in order to calculate the maximum shear stresses in the cement–dentin interface. Differences between groups were determined using two-way ANOVA with Tukey post hoc tests, and paired samples t-tests (α <0.05). Results: Panavia F2.0 showed significantly lower volumetric shrinkage than the other cements. Dual-curing lead to higher contraction stresses for all tested cements compared to self-curing. RelyX Unicem showed higher volumetric shrinkage when dual-cured. Shear bond strength and maximum shear stress was positively influenced by dual-curing. DC Core Automix performed best and Panavia F2.0 worst in terms of shear bond strength and maximum shear stress. Significance: Curing mode may play an important role in the final bond strength to dentin of indirect restorations, depending on the material used. [Copyright &y& Elsevier]

The aim of this study was to evaluate the influence of different polymerization modes on degree of conversion and micropush-out bond strength of dual-polymerized resin core systems to dentin by using two different adhesive systems. Two resin core systems, Rebilda DC and Build-It FR, were used in combination with total-etch (Adper Scotchbond Multi-Purpose) and self-etch (Clearfil SE Bond) adhesive systems. After treatment of dentin surfaces, resin core systems were applied into the cavities and subjected to different polymerization modes as follows: (1) chemical polymerization; (2) dual polymerization with standard mode of LED (Elipar FreeLight 2 LED); or (3) dual polymerization with exponential mode of LED. The cavities (n=10 per group) were tested in a universal testing machine. Degree of monomer conversion (DC%) was determined by Fourier transform infrared spectroscopy (n=5 cavities per group). ANOVA revealed that resin core (p=0.002), adhesive system (p<0.001), and polymerization mode (p<0.001) had significant effects on bond strength values. The degree of conversion for resin cores decreased significantly (p<0.001) when only chemical polymerization was employed. [ABSTRACT FROM AUTHOR]

Enamel decalcification around brackets is sometimes observed during and after orthodontic treatment. Reports in the literature suggest that the preventive advantage of fluoride-releasing adhesive resins may be compromised by an increased incidence of bond failure. The purpose of this study was to determine the effects on shear debonding of incorporating fluoride into the bracket bonding system. Another purpose was to determine the effect of polymerization mode on debonding. Orthodontic brackets were bonded to bovine enamel using one of three types of adhesive resin—no-mix, chemically cured, or light-cured—each formulated with and without fluoride. The teeth were stored in artificial saliva for 24 hours or 30 days and then debonded in shear. Data analysis was performed using ANOVA followed by post-hoc multiple comparison between group pairs. It was found that: (1) fluoride had either no effect or it increased the bond value; (2) the no-mix adhesive demonstrated the lowest bond value; (3) the duration of storage in artificial saliva had no effect on the bond value of the chemically cured and light-cured adhesives but did affect the no-mix adhesive; and (4) the no-mix adhesive released significantly less fluoride than the two other products. Thus, the presence of fluoride in the bonding adhesive does not reduce the force required to debond in shear, and chemically or light-cured adhesives provide consistently higher bond values over extended immersion times than the no-mix product. [ABSTRACT FROM AUTHOR]

Background: Residual monomers released from composite resins have cytotoxic, mutagenic, and estrogenic effects. Mode of polymerization and application thickness are important for monomer release., Aims: The aim of this study was to investigate the effects of different modes of a third-generation light-curing unit (LCU) and layer thickness on residual monomer released from two different bulk-fill composite resins. A total of 80 samples were prepared for each bulk-fill composite using a mold. Each bulk-fill composite was divided into four groups according to polymerization mode (standard and extra power) and layer thickness (2 and 4 mm). In addition, four groups were divided into four subgroups according to time periods (1 h, 24 h, 3 days, and 7 days)., Methods and Material: The samples were polymerized with VALO LED device. The amount of residual monomer was measured with High-Performance Liquid Chromatography (HPLC). All statistical analyses were processed using SPSS Version 23.0. The normal distribution of data was confirmed using Kolmogorov-Smirnov Normal Distribution Test and Shapiro-Wilk Normal Distribution Test. When the distribution was normal, parametric tests, Student's t test and one-way ANOVA, were used. When the distribution was not normal, non-parametric tests, Mann-Whitney U test, and Kruskal-Wallis testwere used., Results: It was found that the standard mode of LCU produced lower amounts of TEGDMA, Bis-GMA, and UDMA in both composite materials. In addition, when the layer thickness increased, TEGDMA, Bis-GMA, and UDMA releases increased, too., Conclusions: This study revealed that the amount of residual monomers released from bulk-fill composites was affected by layer thickness and polymerization time., Competing Interests: None

Background: A few studies have investigated the effect of the activation mode of adhesive systems on bond strength of fiber posts to root canal dentin. This study investigated the push-out bond strengths of a glass fiber post to different root canal regions with the use of two adhesives with light- and dual-cure polymerization modes., Materials and Methods: In this in vitro study, 40 maxillary central incisors were decoronated at cement-enamel junction with 15 ± 1 mm root length. After root canal therapy and post space preparations, they were randomly divided into four groups. Post spaces were treated with four different adhesives: Excite, Excite Dual cure Single Component (DSC), self-etch adhesive (AdheSE), and AdheSE dual-cure. Then the fiber-reinforced composite (FRC) post, Postec Plus, was cemented with dual-cure resin cement, Variolink II. The roots were cut into three 2-mm-thick slices. Push-out tests were performed with a universal testing machine at a crosshead speed of 0.5 mm/min. The mode of failures was determined under a stereomicroscope. Data were analyzed by three-way analysis of variance (ANOVA) and Tukey test was conducted to compare post hoc with P < 0.05 as the level of significance., Results: The highest bond strength was obtained for AdheSE dual-cure (15.54 ± 6.90 MPa) and the lowest was obtained for Excite light-cure (10.07 ± 7.45 MPa) and only the bond strength between these two adhesives had significant difference (P = 0.02). Bond strength decreased from the coronal to the apical in all groups and this was significant in Excite (group 1) and AdheSE (group 3) (P < 0.001). In apical regions, bond strength of dual-cure adhesives was significantly higher than light-cure adhesives (P < 0.001)., Conclusion: Push-out bond strength of fiber post to different regions of root canal dentin was affected by both adhesive systems and their polymerization modes.