Shear bond strength (SBS) testing is a commonly used method for evaluating different dental adhesive systems. Failure mode analysis provides valuable information for better interpretation of bond strength results. The aim of this study was to evaluate the influence of specimen dimension and loading technique on shear bond strength and failure mode results. Eighty macro and micro flowable composite cylindrical specimens of 1.8 and 0.8 mm diameter, respectively, and 1.5 mm length were bonded to dentinal substrate. Four study groups were created (n = 20): Macroshear wireloop, Gp1; Microshear wireloop, Gp2; Macroshear chisel, Gp3; and Microshear chisel, Gp4. They were tested for SBS using chisel and wireloop loading devices followed by failure mode analysis using digital microscopy and SEM. Two- and one-way ANOVA were used to compare stress at failure values of different groups while the Kruskal–Wallis test was used to compare between failure modes of the tested groups. Gp4 recorded the highest mean stress at failure 54.1 ± 14.1 MPa, and the highest percentage of adhesive failure in relation to the other groups. Specimen dimension and loading technique are important parameters influencing the results of shear bond strength. Micro-sized specimens and chisel loading are recommended for shear testing.

Background: There is tendency for unavoidable sealer extrusion in some clinical cases. This might adversely affect host stem cells and affect healing. This study aimed to investigate the effect of different sealers on the cytocompatibility and osteogenic potential of human periodontal ligament stem cells (hPDLSCs). Methods: The cytotoxic effect of the extracted elutes of VDW.1Seal (VDW.1), Endosequence BC Sealer HiFlow (ES), GuttaFlow-2 (GF), and ADSeal (AD-S) on the hPDLSCs was determined using the MTT assay. Cell proliferation and migration were assessed by the scratch wound healing assay. Osteogenic differentiation potential was assessed. Measurement of pH values and calcium ions release was performed. Results: GF had a significantly higher percentage of viable cells. The cell migration assay showed that GF demonstrated the lowest open wound area percentage. GF and AD-S showed the highest calcium nodule deposition. GF demonstrated higher ALP activity than ES. Expression of RUNX2 and OC genes was similar for all sealers, while OPG gene expression was significantly higher for VDW.1 and GF. ES and AD-S displayed the highest pH values on day 1. Calcium ion release of ES and VDW.1 was significantly the highest. Conclusions: GuttaFlow-2 and VDW.1Seal sealers have favorable behavior toward host stem cells.

Background: This study was designed to investigate the in vitro bioactivity of a new dual cured calcium silicate cement (TheraCal PT) compared to its light cured (TheraCal LC) and chemically set (Biodentine) counterparts. Materials and Methods: The study is an in vitro original research article. Prepared cements discs were immersed in deionized water. Ca²+ release was evaluated using inductively coupled plasma-optical emission spectrometry while pH was assessed using a pH meter after 1, 14, and 28 days. Discs for surface characterization were immersed in phosphate-buffered saline (PBS) and were examined using an environmental scanning electron microscope with energy dispersive X-ray (ESEM/EDX), immediately after setting and at 1, 14, and 28 days intervals after that. Attenuated total reflectance (ATR)/Fourier transform infrared (FTIR) and Raman spectroscopy analyses were performed after setting and after 28 days storage in PBS. Statistical analysis was performed using the two-way repeated measure analysis of variance test followed by Bonferroni test for multiple comparisons (P < 0.05). Results: Biodentine exhibited the highest mean values for Ca²+ release (792,639,278 ppm) and pH (10.99, 12.7, 11.54) at all time intervals. ESEM/EDX displayed a continuous layer of calcium phosphate formed by Biodentine and TheraCal LC while TheraCal PT developed scarce interrupted precipitates after immersion in PBS. ATR/FTIR and Raman spectroscopy for the formed precipitates confirmed the presence of phosphate and Ca (OH) ₂ in Biodentine, TheraCal LC and TheraCal PT. Conclusion: TheraCal PT exhibited limited in vitro bioactivity which may limit its prognosis in clinical applications for vital pulp therapy. TheraCal LC is considered a potential bioactive calcium silicate cement despite its lower Ca²+ release compared to Biodentine. Highest bioactivity was observed in Biodentine.

Objectives: To investigate the effect of three different calcium silicate-based materials (CSBM) on the biological behavior of human periodontal ligament stem cells (hPDLSCs). Methods: Eluates of Biodentine, NeoPutty and TheraCal PT prepared at 1:1, 1:2, and 1:4 ratios were extracted under sterile conditions. The cytotoxicity of the extracts to the hPDLSCs was assessed using the MTT assay. Scratch wound healing assay was utilized for assessing cell migration. Scanning electron microscopy was used to detect cell attachment and morphology. Calcium ion release was measured using inductively coupled plasma-optical emission spectrometry; the pH-value was evaluated with a pH-meter. ANOVA with post hoc Tukey test was used for statistical analysis. Results: Cell viability was significantly higher for Biodentine and NeoPutty at day 1 with all dilutions (p < 0.05), while at day 3 and day 7 with dilutions 1:2 and 1:4; all materials showed similar behavior (p > 0.05). Biodentine had the highest percentage of cell migration into the scratched area at day 1 for all dilutions (p < 0.05). Stem cells were attached favorably on Biodentine and NeoPutty with evident spreading, and intercellular communications; however, this was not shown for TheraCal PT. Biodentine showed the highest pH values and calcium ion release (p < 0.05). Conclusions: The resin-free CSBM showed better performance and favorable biological effects on hPDLSCs and were therefore considered promising for usage as endodontic repair materials. Clinical significance: Proper selection of materials with favorable impact on the host stem cells is crucial to ensure outcome in different clinical scenarios.

Background: Controversial properties and performance of commercially available 3D-printed resin composite for permanent restorations. So, the purpose of this study was to assess the flexural strength, microhardness, wear, and color stability of 3D-printed versus milled nanohybrid resin composites for permanent restoration. Methods: A total of 70 samples of nanohybrid resin composites were used; 38 bar-shaped (14 mm ⋅ 2 mm ⋅ 2 mm) and 32 disc-shaped samples (10 mm ⋅ 2 mm) of Tetric CAD^™ blocks (TC) and Flexcera Smile Ultra plus^™ (FSU) were fabricated (n = 35). Flexural properties were tested using 3-point bending test. The Vickers test was used for microhardness evaluation. Volumetric wear analysis and color changes were assessed after simulated aging via Geomagic Control X software and a Vita Easyshade spectrophotometer, respectively. Color changes were calculated via the CIEDE2000 formula. A paired t-test was used for dependent variable analysis, and the Mann‒Whitney U test was used for independent variables (α = 0.05). Results: TC resulted in significantly higher flexural strength (247.7 ± 29.1 MPa) and microhardness (94.6 ± 3 gf/um²) than did FSU (97.2 ± 10.2 MPa and 31 ± 4.6 gf/um^2, respectively) (P < 0.0001). Compared with FSU (–36.3 mm³), TC resulted in significantly lower wear rates (–17.6 mm³)(P < 0.0001). TC had a ΔE00 value of 2.4 ± 0.5, whereas FSU had a value of 2.1 ± 0.7 (P = 0.532), with no significant difference between the groups, but both values were above the acceptability limit (1.8). Conclusions: Compared with 3D-printed nanohybrid resin composites, milled nanohybrid resin composites have better flexural strength, microhardness and wear properties. Clinical relevance: Milled nanohybrid resin composites exhibit superior flexural strength, microhardness, and wear resistance, making them potentially more durable for clinical dental restorations compared to 3D-printed nanohybrid resin composites.

The objective of this in vitro study was to examine the impact of different endodontic chelating agents on the flexural strength and microhardness of root dentin. Fourty dentin sticks of (1 mm × 1 mm × 12 mm) were obtained from 10 single-rooted premolars and divided into four groups (n = 10). One stick from each tooth was assigned to one of the experimental groups and was soaked in one of the experimental chelating solutions for 5 min 17% ethylenediaminetetraacetic acid (EDTA), 2.5% phytic acid (PA), 18% etidronic acid, or saline (control group). Following the 5-min soak, the sticks' flexural strength was evaluated using a 3-point loading test using the universal testing machine, and the surface microhardness was tested using a Vickers's microhardness tester. PA (2.5%) and etidronic acid (18%) showed no significant detrimental effect on either the flexural strength or the surface microhardness of radicular dentin compared to the control. EDTA (17%) exhibited a significant drop in the flexural strength and microhardness of radicular dentin compared to the other groups. PA and etidronic acid chelators do not compromise the surface and bulk mechanical properties of radicular dentin.