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Objectives To study the effect of resin matrix and maturation time (1 and 24 h) on the creep deformation of resin-composites, two of which have matrix-forming monomers that are either bis-GMA free or have an ormocer structure between the C C groups. Methods Five resin-composites: four commercial and one experimental were investigated. Six specimens were prepared for each material and were divided into two groups ( n = 3) according to the maturation time and condition. Group A was stored dry at room temperature for 1 h and Group B was stored for 24 h in distilled water to allow post-curing at 37 °C. Each specimen was loaded (20 MPa) for 2 h and unloaded for 2 h. The strain deformation was recorded continuously for 4 h. Statistical analysis was performed using one-way ANOVA and the Bonferroni post hoc test at a significance level of a = 0.05. Results The maximum creep-strain % after 1 h ranged from 1.32% to 2.50% and was reduced after 24 h post-cure to between 0.66% and 1.47%. Also, the permanent set after 1 h ranged from 0.70% up to 1.27% (Group A) and after 24 h ranged from 0.53% up to 1.20% (Group B). Significance Creep deformation and maximum recovery for all resin-composites decreased with time, demonstrating improvement in viscoelastic stability. However, there was no significant difference between the permanent set at different times, except for Herculite XRV Ultra. Composites with novel matrices showed comparable properties to existing bis-GMA based materials. [ABSTRACT FROM AUTHOR]

Objective Since bulk-fill (BF) resin composites should cure efficiently to a depth up to 4 mm, the aim of the study was to determine the time-dependence of degree of conversion (DC) at that depth during 24 h post-irradiation. Methods Eight representative BF resin composites were studied [x-tra base (XTB), Venus Bulk Fill (VBF), Tetric EvoCeram Bulk Fill (TECBF), Sonic Fill (SF), Filtek Bulk Fill (FBF), everX Posterior (eXP), Beautifil-Bulk Flowable (BBF), Beautifil-Bulk Restorative (BBR)]. Specimens were fabricated in white Delrin moulds of 4 mm height and 5 mm internal diameter directly on an attenuated total reflectance (ATR) accessory attachment of an (FTIR) spectrometer (Nicolet iS50, Thermo Fisher, Madison, USA). Upper specimen surfaces were irradiated in situ for 20 s with an LED curing unit (Elipar S10 with average tip irradiance of 1200 mW/cm 2 ). Spectra from the lower surface were recorded continuously in real-time for 5 min and then at 30 and 60 min and 24 h post irradiation. Results Mean ranges of DC 4mm (%) of the materials at 4 mm depth were 39–67; 48–75; 45–74; and 50–72 at 5, 30 and 60 min and 24 h respectively. DCs for XTB, VBF, TECBF, FBF, BBR increased significantly 30 min after irradiation ( p < 0.05) and were not affected by subsequent time up to 24 h ( p > 0.05). DC for SF was not affected by subsequent time after 5 min ( p > 0.05). For eXP and BBF, DC increased 24 h after irradiation ( p < 0.05). The data were described by the superposition of two exponential functions characterising the gel phase (described by parameters a, b) and the glass phase (described by parameters c and d). Significance Post polymerization impact of bulk-fill composites is material dependent. Five materials exhibited their maximum DC 4mm already 30 min after starting the irradiation while DC 4mm for two materials optimized after 24 h. BF materials were found to exhibit after 24 h a DC between 50 and 72% at 4 mm depth under the stated irradiation conditions. [ABSTRACT FROM AUTHOR]

Objective: To study the effect of compositional variables and temperature (25°C and 37°C) on the rheological properties of contemporary resin composites. Methods: Fourteen commercial resin composites with different resin matrices of Bis-GMA and TEGDMA, different filler loading (41–65, v/v) and particle sizes (ranging 5nm to 20μm) were studied using a parallel plate rheometer. Shear sweep measurements were made to determine each composite's viscosity over the angular frequency range of ω =10−4–102 rad/s. Data were analyzed using one way ANOVA, Bonferroni post hoc and t-independent tests (p <0.05). Results: All composites exhibited viscosity reducing with shear rate (pseudoplasticity). Viscosity averages were calculated over the shear rate range. These viscosities increased as the percentage of filler loading (by volume) increased ranging between 0.05–349.33kPas at 25°C and 0.03–132.00kPas at 37°C. Filtek Supreme XTE exhibited the highest viscosity at both temperatures (p <0.05). Filtek Bulk Fill on the other hand, showed the lowest viscosity at both temperatures (p <0.05). Viscosity significantly decreased with the increase in the temperatures for all materials (p <0.05). The reduction ranged from 40.8% (for Venus Diamond Flow) to 92.2% (for Spectrum TPH3). Significances: There was a considerable variation in the resin composite viscosities measured at 25°C as an average value for shear-rate sweep. The factor between the least and highest viscosities was about 7000. The formulation differences that led to such a great variation were primarily: (i) volume fraction of fillers and (ii) particle size, the latter influencing total particle surface area. Rheological properties such as viscosity are key parameters influencing perceived differences in handling behavior of resin composites. [ABSTRACT FROM AUTHOR]

• The highest shear bond strength value was observed in group 1 (non-infected dentin). • The lowest bond strength value was displayed in group 3 (Photodynamic therapy on infected dentin). • Carious dentin showed lower bond strength to composite resin as compared to non-carious dentin. To evaluate the adhesive bond integrity (shear bond strength-SBS) of composite resin bonded to carious dentin using chlorhexidine gluconate (CHX), Er,Cr:YSGG laser (ECYL) and photodynamic therapy (PDT). Thirty carious and ten non-carious mandibular teeth were collected through non-traumatic extraction. All samples were embedded in polyvinyl cross-sections to the cemento-enamel junction. The preparation of caries-affected dentin was performed by grinding the specimens using silicon carbide discs. All specimens were randomly allocated in to four groups (n = 10). Group 1, non-affected dentin with no disinfection; Group 2, caries affected dentin treated with 2% CHX; Group 3, affected dentin disinfected with PDT [100 mg/L methylene blue solution (MBS) and Diode laser]; Group 4, affected dentin treated with ECYL. Self-etch adhesive was smeared on all specimens for 10 s and photopolymerized for 10 s. All specimens were placed in an incubator with humid environment for 24 h at 37 °C followed by positioning in universal testing machine for SBS testing. Failure mode examination of debonded samples was performed by a stereomicroscope. Analysis of variance (ANOVA) was used for inter group comparison through mean and standard deviation of each group. For multiple group comparison Tukey HSD was employed. Level of significance was established at p < 0.05. The highest SBS value was observed in group 1 (24.98 ± 1.59 MPa). Whereas, the lowest bond strength was displayed by group 3 (14.22 ± 1.40 MPa) specimens. Lased dentin in group 4 (15.89 ± 3.22 MPa) exhibited SBS values comparable to group 3 (14.22 ± 1.40 MPa). Group 2 (CHX-18.25 ± 1.29 MPa) exhibited statistically significant difference compared to all experimental groups (p < 0.05). Adhesive bond strength of disinfected carious dentin was higher with CHX treatment as compared to Photodynamic therapy and Er,Cr: YSGG laser treatment. Carious dentin showed lower bond strength to composite resin as compared to non-carious dentin. [ABSTRACT FROM AUTHOR]

• The highest extrusion bond strength was achieved in samples treated with curcumin photosensitizer (PS). • The lowest extrusion bond strength was observed in canal irrigated with conventional 5.25% NaOCl + 17% EDTA. • PS activated with PDT improved extrusion bond strength at all root levels compared to control. To evaluate the effect of different photosensitizer on extrusion bond strength of glass fiber post to radicular dentin. Forty maxillary and mandibular central incisors were disinfected and decoronated. Mechanical instrumentation of canal was performed using protaper NiTi. Shaping and cleaning of canal comprised of S1, S2, SX with finishing files F1 and F2, followed by continuous irrigation. Canals were dried and obturated with gutta percha. Peso reamers were used to prepare post space. Based on the photosensitizers (PS) used, the samples were divided into three groups (n = 10). Group 1: treated with methylene blue photosensitizer (MBP) at 50 mg/l, Group 2: Curcumin photosensitizer (CP) at 500 mg/l, Group 3: canal space was filled with Toluidine blue photosensitizer (TB) at 100 mg/l. All photosensitizers were activated using different lasers. The samples in group 4 (control) were irrigated using 5.25% sodium hypochlorite (NaOCl) + 17% ethylenediamine tetra acetic acid (EDTA). Posts were cemented and teeth were sectioned into coronal, middle and apical sections. All sections were placed in universal testing machine to evaluate extrusion bond strength in megapascal (MPa). Fracture pattern analysis of samples were seen under stereomicroscope at 50x magnification and categorized into adhesive, cohesive and admixed. Assessment of extrusion bond strength was performed by one-way analysis of variance (ANOVA) and Tukey multiple comparison test (p = 0.05). The highest bond strength was achieved in group 2, including samples treated with curcumin photosensitizer (CP) at all three root levels; cervical (9.01 ± 1.62 MPa), middle (7.95 ± 0.75 MPa) and apical (5.81 ± 0.15 MPa). Whereas, the lowest extrusion bond strength was observed in group 4 (canal irrigated with conventional 5.25% NaOCl +17% EDTA) at coronal (6.10 ± 1.77 MPa), middle (5.11 ± 0.75 MPa) and apical one-thirds (3.65 ± 0.14 MPa). Intra group comparison revealed decrease in extrusion bond strength from coronal to apical direction. Moreover, both group 2 and group 3 showed statistically significant difference to samples in control group and group 1. (p < 0.05). TB and CP at concentration of 100 mg/l and 500 mg/l has the potential to be used as an alternate to conventional cleaning regime. TB and CP at this concentration when activated with PDT is likely to improve extrusion bond values. [ABSTRACT FROM AUTHOR]