Esraa A. Attar

The aim of this study was to investigate the effect of repeated pressing of lithium disilicate ceramic on the shear bond strength (SBS) of three types of resin cement. Methodology: A lithium disilicate ceramic (IPS e.max^® Press) was first heat-pressed to form rectangular disk specimens. Then, leftovers were used for the second and third presses. A total of 90 specimens were prepared and separated, according to the number of pressing cycles, into three groups: 1st, 2nd, and 3rd presses (n = 30). Each group was further subdivided into three groups (n = 10) according to the type of resin cement used, as follows: Multilink N (MN), Variolink Esthetic DC (VDC), and Variolink Esthetic LC (VLC). All the cement was bonded to the ceramic surface, which was etched with hydrofluoric acid and primed with Monobond Plus. All samples were light-cured and stored for 24 h. Shear bond strength was tested on a universal testing machine. Results: A two-way ANOVA was used to evaluate the influence of repeated pressing cycles and cement type as well as their interaction. The results indicated that cement type has a significant impact (p < 0.001) but not the number of pressing cycles (p = 0.970) or their interaction (p = 0.836). The Bonferroni post-hoc test showed that the SBS of MN was significantly higher than that of VDC and VLC in the first press and second press cycles, respectively. The SBS of MN was significantly higher than that of VDC and VLC cements in the third pressing cycle. There was no significant difference in the SBS between VLC and VDC in all three pressing cycles. Conclusion: The results of the current study did not report a detrimental effect of repeated pressing up to three cycles on the shear bond strength of the IPS e.max^® Press. Multilink resin cement showed the highest SBS to IPS e.max^® Press at the third pressing cycle. For all types of cement and heat pressing cycles, the majority of cement failures were adhesive. No cohesive failures occurred in any of the tested resin cements, regardless of the cement type or the number of heat pressing cycles tested.

Objective The purpose of this in vitro study is to compare the flexural strength and Weibull modulus of 5 different monolithic computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics. Methods A total of 50 specimens were fabricated, 10 from each of the following materials: lithium disilicate-based ceramic (IPS e.max CAD), zirconia -reinforced lithium-silicate ceramic (Vita Suprinity), leucite-based glass ceramic (IPS Empress CAD), and two zirconia-based ceramics (Zenostar and CopraSmile). The specimens were 4 mm wide, 2 mm thick, and 16 mm long. Flexural strength test was executed using a universal testing machine (Model 5980, Instron Industrial Products, Norwood, MA, USA). The two-parameter Weibull distribution function was used to analyze the variability of flexural strength values. Statistical analysis was performed on SPSS Version 23 (IBM Corp., Armonk, NY, USA) using one-way analysis of variance (ANOVA) and post-hoc Tukey’s test. Results Suprinity had the highest Weibull modulus value, while Empress CAD displayed the lowest value. One-way ANOVA showed significant difference in the flexural strength between the different materials tested (p<0.05). Post-hoc analysis revealed significant differences among all the test groups in terms of flexural strength. Zenostar presented the highest mean flexural strength value (1033.90 MPa), while Empress CAD had the lowest value. Conclusion High-translucency zirconia had superior flexural properties than translucent zirconia, lithium disilicate ceramics, zirconia-reinforced lithium silicate ceramics, and leucite-based glass ceramics.

The objective of this study was to synthesize and assess unfilled and filled (silica nanoparticles) dentin adhesive polymer. Methods encompassing scanning electron microscopy (SEM)—namely, energy dispersive X-ray spectroscopy (EDX), micro-tensile bond strength (µTBS) test, Fourier transform infrared (FTIR), and micro-Raman spectroscopy—were utilized to investigate Si particles’ shape and incorporation, dentin bond toughness, degree of conversion (DC), and adhesive–dentin interaction. The Si particles were incorporated in the experimental adhesive (EA) at 0, 5, 10, and 15 wt. % to yield Si-EA-0% (negative control group), Si-EA-5%, Si-EA-10%, and Si-EA-15% groups, respectively. Teeth were set to form bonded samples using adhesives in four groups for µTBS testing, with and without aging. Si particles were spherical shaped and resin tags having standard penetrations were detected on SEM micrographs. The EDX analysis confirmed the occurrence of Si in the adhesive groups (maximum in the Si-EA-15% group). Micro-Raman spectroscopy revealed the presence of characteristic peaks at 638, 802, and 1300 cm⁻¹ for the Si particles. The µTBS test revealed the highest mean values for Si-EA-15% followed by Si-EA-10%. The greatest DC was appreciated for the control group trailed by the Si-EA-5% group. The addition of Si particles of 15 and 10 wt. % in dentin adhesive showed improved bond strength. The addition of 15 wt. % resulted in a bond strength that was superior to all other groups. The Si-EA-15% group demonstrated acceptable DC, suitable dentin interaction, and resin tag formation.

The aim was to evaluate the effect of ceramic lumineers on inflammatory periodontal parameters, gingival crevicular fluid (GCF) flow rate and cytokine profile. Patients were provided with lumineers using standardized technique including minimal to no preparation. Ceramic lumineers were etched with hydrofluoric acid and teeth with phosphoric acid followed by adhesive cementation. Periodontal parameters (Plaque index (PI), bleeding on probing (BOP), periodontal pocket depth (PPD), and clinical attachment loss (CAL)) were recorded at baseline and after 4, 12, and 24 weeks of lumineer cementation. Assessment of GCF flow rate and levels of IL-6 and TNF-α was made using enzyme linked immunosorbent assay (ELISA). The statistical significance was determined by the t-test, analysis of variance and post hoc Tukey’s test. It was found that PI, BOP, PPD, and CAL at baseline and 24 weeks were comparable (p > 0.05). The GCF volume at baseline was comparable to the GCF at week 24 (p > 0.05). The IL-6 levels at baseline (5.4 ± 3.6) were similar to those at 24 week (7.4 ± 5.2) (p > 0.05). The TNF-α at week 4 (65.3 ± 16.2), 12 (25 ± 10.2), and 24 (21.3 ± 7.6) was higher than the baseline (13.7 ± 5.8) (p < 0.05). Clinical periodontal parameters and GCF volume among patients treated with ceramic lumineers at baseline and twenty-four week follow-up were comparable. The GCF TNF-α levels significantly increased after ceramic lumineer cementation at 24-week follow-up.

Dental laboratories (LABs) are integral to the performance of a dentist in providing successful oral rehabilitation. The aim of this study was to compare the adaptation, contour, contacts, and shade matching of different government and commercial dental LABs in the fabrication of porcelain fused to metal (PFM) crowns. Thirty-two dental LABs were selected to fabricate PFM crowns (one PFM crown each). Marginal adaptation, contour, proximal contacts, and shade matching were evaluated. Evaluation of the crowns’ quality was performed following modified USPHS/FDI criteria. Visual and colorimeter assessments were employed to evaluate shade matching. Differences between groups were examined by Pearson’s Chi-square and Fisher’s exact test. The quality of marginal adaptation of crowns was good in 81.25%, however the quality of contours, contacts, and shade matching was compromised in 43.75%, 59.38%, and 39% of all LABs, respectively. Visual and colorimeter shade matching was acceptable in 62.5% and 80% of LABs in the cervical third and middle third regions of crowns, respectively, however in the incisal third the shade matching was unacceptable in nearly 60% of LABs. Commercial laboratories showed significantly better contours and shade matching, but not marginal adaptation. However, no significant differences were found in comparison of proximal contacts between the groups.