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Objective: Assessment of post surface conditioners [sulfuric acid (SA), Rose Bengal (RB), and sandblasting (SB)] and different luting cements [methyl methacrylate (MMA)-based cement and composite-based cement] on pushout bond strength (PBS) of poly-ether ether-ketone (PEEK) post bonded to canal dentin. Materials and methods: Endodontic treatment was performed on 120 single-rooted human premolar teeth. The preparation of the post space was performed and 4mm of gutta-percha was retained in the apical region of the root. One hundred and twenty PEEK posts were fabricated from a PEEK blank utilizing a Computer aided design-Computer aided manufacture (CAD-CAM) system. The PEEK posts were allocated randomly into four groups based on post surface conditioning (n = 30). Group A: SA, Group B: RB, Group C: SB, and Group D: No conditioning (NC). Each group was further divided into two subgroups based on the luting cement used for bonding (n = 15). Group A1, B1, C1, and D1 specimens were cemented using composite-based resin cement. However, Group A2, B2, C2, and D2 posts were luted with MMA-based resin cement. PBS assessment using a universal testing machine was performed. Failure modes were analyzed under a stereomicroscope. The data relating to the effects of surface treatment and luting types of cement were analyzed using one-way analysis of variance (ANOVA) and Tukey's post hoc test ( p = 0.05). Results: Coronal section of Group B2: RB+Super-Bond C&B [9.61 ± 0.75 megapascals (MPa)] displayed the highest bond scores of PEEK after root dentin. Whereas it was also discovered that Group D1: NC+Panavia®V5 (2.05 ± 0.72 MPa) presented the lowest PBS scores. Intergroup comparison analysis revealed that Group A2: SA+Super-Bond C&B and Group B2: RB+Super-Bond C&B displayed no significant difference in their bond scores. Conclusions: RB and SA possess the potential to be used as a PEEK post conditioner. MMA-based cement displayed better performance than composite-based cement. [ABSTRACT FROM AUTHOR]

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]

Objective. Our study is aimed at preparing an experimental adhesive (EA) and assessing the influence of adding 5-10 wt.% concentrations of zinc oxide (ZnO) nanoparticles on the adhesive's mechanical properties. Methods. Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) spectroscopy were employed to investigate the morphology and elemental distribution of the filler nanoparticles. To examine the adhesive properties, microtensile bond strength (μTBS) testing, an investigation of the rheological properties, degree of conversion (DC), and analysis of the interface between the adhesive and dentin were carried out. Results. The SEM micrographs of ZnO nanoparticles demonstrated spherical agglomerates. The EDX plotting confirmed the incidence of Zn and oxygen (O) in the ZnO nanoparticles. The highest μTBS was observed for nonthermocycled (NTC) 5 wt.% ZnO group (32.11 ± 3.60 MPa), followed by the NTC-10 wt.% ZnO group (30.04 ± 3.24 MPa). Most of the failures observed were adhesive in nature. A gradual reduction in the viscosity was observed at higher angular frequencies, and the addition of 5 and 10 wt.% ZnO to the composition of the EA lowered its viscosity. The 5 wt.% ZnO group demonstrated suitable dentin interaction by showing the formation of resin tags, while for the 10 wt.% ZnO group, compromised resin tag formation was detected. DC was significantly higher in the 0% ZnO (EA) group. Conclusion. The reinforcement of the EA with 5 and 10 wt.% concentrations of ZnO nanoparticles produced an improvement in the adhesive's μTBS. However, a reduced viscosity was observed for both nanoparticle-reinforced adhesives, and a negotiated dentin interaction was seen for 10 wt.% ZnO adhesive group. Further research exploring the influence of more filler concentrations on diverse adhesive properties is recommended. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate the effect of brushing with two whitening dentifrices (Colgate Optic White (COW) and Colgate Optic White Charcoal (COC)) on surface gloss, micro-roughness, and micro-hardness of nanostructured hybrid conventional (Z350) and bulk-fill (Tetric N Ceram bulk-fill) polymer composite. In total, 96 disk samples using two nano-hybrid composite polymers (Z350 and Tetric N Ceram Bulk-fill) were prepared. All specimens were exposed to two different dentifrices (COW and COC), resulting in four main subgroups in the study. Specimens were assessed for surface gloss, micro-roughness (Ra), and micro-hardness using standardized methodology. Means and standard deviations of properties compared using paired t-test, one-way and two-way ANOVA, and post hoc test. The presence of dentifrices did not show any significant difference in micro-hardness values of Z350 (p > 0.05), whereas micro-hardness of bulk-fill composite significantly reduced on dentifrices exposure (p ≤ 0.05). Bulk-fill polymer composite showed significant reduction in gloss after dentifrice exposure (p < 0.05), however, Z350 showed no significant loss of gloss due to dentifrices (p > 0.05). A significant increase in Ra was observed for both resin materials after exposure to dentifrices (COC and COW). Conventional resin composite (Z350) showed comparable surface hardness and gloss before and after dentifrice exposure, however, micro-roughness increased significantly due to dentifrice exposure. Bulk-fill resin (Tetric N Ceram) showed significant loss of micro-hardness and gloss and increase in micro-roughness on dentifrice exposure. Conventional nano-hybrid composite polymer showed better durability in resisting loss of surface properties compared to bulk-fill resin polymer in the present experiment. [ABSTRACT FROM AUTHOR]

Knowledge about the influence of fillers in denture base resin is vague. This systematic review aimed to report the reinforcing effect of fillers on the mechanical properties of denture base resin by following PRISMA guidelines. Two electronic databases (Pubmed/Medline & Web of Science) were searched for articles using the keywords: fibers in denture base, fillers in denture base, and reinforcement of denture base. Laboratory studies complying with the inclusion criteria were reviewed according to the set protocol. The established focus question was: "Do reinforcing fillers positively influence the mechanical properties of polymethyl methacrylate (PMMA) heat polymerized denture base material?" A total of twenty-nine relevant papers qualified for final inclusion. Of these, 24 were determined to have a moderate risk of bias. Micron or nano-sized metal/metal oxides particles and glass fibers were the frequently used reinforcing agents. The trend of evaluating fractural strength (FS) was common. Most of the studies limited the use of reinforcing agents up to 5 wt.%. FS, fracture toughness (FT), and impact strength (IS) tend to increase if the fillers are chemically bonded and well-dispersed in denture base resin. Though fillers with a higher elastic modulus increase the hardness of the reinforced denture base resin, they compromise other mechanical properties. Well-dispersed lower filler loading PMMA denture base resin can enhance the FS, FT, and other related mechanical properties. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to evaluate marginal fit of yttrium tetragonal zirconia polycrystals (Y-TZP)' copings with different finish line designs fabricated with various digital scanners and milling systems. Methods: Three model plastic teeth were prepared with three finish line designs: Design-1, continuous chamfer; Design-2, chamfer with shallow depression; Design-3, chamfer with deep depression. The "master models" were replicated using elastomeric polyvinyl siloxane impression material and poured in type IV stone generating 90 dies, 30 dies for each design. Dies were scanned and copings were milled utilizing three digital scanners and computer-aided design/computer-aided manufacturing (CAD/CAM) systems: System-1, InEos Red Scan (Sirona Dental Systems, Germany), Vitablocks® Mark II (VITA, Germany) copings milled by Cerec® inLab (Sirona Dental Systems, Germany); System-2, Cerec® AC Connect with BlueCam (Sirona Dental Systems, Germany), Vitablocks® Mark II (VITA, Germany) copings milled by Cerec® inLab (Sirona Dental Systems, Germany); and System-3, NobleProcera™ Optical Scanner (NobleBiocare™), procera zirconia coping milled by a Noble Procera™ milling machine (NobleBiocare™). Copings were seated on their respective "master models" and secured with uniform force. Eight measurements per coping were performed at pre-established points, with a metallurgical microscope (Zeiss, Germany) connected to a high precision digital video-micrometer (Javelin JV6000, California, USA) at 200 × magnification. Results: The tested systems demonstrated marginal gaps ranging from 12.4 to 26.6 µ m. Results for marginal fit of milled copings fabricated using three systems with different finish line designs differed significantly (p < 0.05). Procera zirconia copings scanned and milled with NobleProcera™ exhibited significantly lower marginal gaps compared to other specimen groups. However, InEos Red Scan/Vitablocks® Mark II/Cerec® inLab showed maximum marginal gaps among the study specimens. Conclusions: CAD-CAM manufactured Y-TZP' copings exhibited marginal gaps ranging from 12.49 to 26.6 µ m. The CAD-CAM fabrication system was a significant factor influencing the marginal misfit of Y-TZP' copings. Margin design exhibited system dependent influence on the marginal misfit. Marginal misfit observed for all systems were within clinically acceptable parameters. [ABSTRACT FROM AUTHOR]

Aim: The aim of the study was to investigate the shear bond strength (SBS) and compressive strength (CS) of Er Cr YSGG laser (ECL) treated, re-bonded lithium disilicate (LD) ceramic in comparison to standard conventional conditioning (hydrofluoric acid (HFA) and silane). Methods: One hundred LD ceramic disks were divided equally for SBS and CS testing. Eighty samples were conventionally surface treated and bonded to resin cement followed by de-bonding of the cement build-up. All de-bonded specimens were divided into four groups based on re-bonding surface treatments (HFA, primer, adhesive, and ECL). Resin cement build-ups were performed in 40 specimens for SBS testing (universal testing machine); however, the remaining 40 specimens were tested for CS. Ten specimens each were used as controls (surface treatment was performed once and no primary resin cement bonding) for SBS and CS assessment. Surface topography was assessed using a scanning electron microscope. Results: The maximum and minimum SBS values were shown by groups: control (33.42 ± 3.28 megapascals (MPa)); and ECL (17.50 ± 2.22 MPa) respectively. The maximum and minimum CSs were displayed by specimens in the ECL group (439.45 ± 70.68 MPa) and the control group (237.28 ± 19.96 MPa), respectively. For ECL specimens, SBS was significantly lower and CS was significantly higher as compared to control specimens. Conclusions: Application of the Er Cr YSGG laser significantly improved the CS of de-bonded ceramic specimens. However, it did not show a positive influence on the bond integrity of re-bonded ceramics in comparison to conventional surface treatment regimes. [ABSTRACT FROM AUTHOR]

Objective: The aim was to compare restorative marginal integrity of ceramic crowns luted with bioactive and resin cements using micro-computed tomography (micro-CT) microleakage evaluations and bond strength assessment. Methods: Thirty molar teeth were prepared by sectioning and polishing for dentin exposure for resin cement build-ups. Teeth were randomly divided among three groups of cements: (1) bioactive (ACTIVA); (2) glass ionomer cement (GIC; Ketac Cem); and (3) resin luting agent (Nexus 3). Bonding regime and build-ups (4 mm × 2 mm) were performed using the recommended protocol. For microleakage assessment, 30 premolar teeth were prepared for dentin-bonded crowns using lithium disilicate ceramic and the computer-aided design and computer-aided manufacturing technique. Crowns were cemented with standard load, cement amount, and duration using three cements (Group A: bioactive; Group B: GIC; Group C: resin) and photopolymerized. Cemented crowns were evaluated for volumetric infiltration using micro-CT (Skyscan, Bruker 1173- at 86 kV, 93 µA, 620 ms) after immersion in 50% solution of silver nitrate (AgNO3) (24 hours). Shear bond strength (SBS) was assessed by fracture of cement build-ups at a cross-head speed of 0.5 mm/min in a universal testing machine. Results: Mean SBS among bioactive (21.54 ± 3.834 MPa) specimens was significantly higher than that for GIC (14.08 ± 3.25 MPa) specimens (p < 0.01), but they were comparable to resin samples (p > 0.05) (24.73 ± 4.32 MPa). Microleakage was significantly lower in crowns luted with bioactive (0.381 ± 0.134) cement compared to GIC (1.057 ± 0.399 mm3) (p < 0.01) and resin (0.734 ± 0.166 mm3) (p = 0.014) cemented crowns. The type of luting agent had a significant influence on the microleakage of crowns and bond strength to dentin (p < 0.05). Conclusion: Bioactive cement exhibited less microleakage and comparable SBS to resin luting agents in in vitro conditions. [ABSTRACT FROM AUTHOR]