Wonjoon Moon

Calcium silicate-based cements (CSCs) play a pivotal role in endodontic applications due to their favorable properties. This study investigates how blood contamination, a common clinical challenge during endodontic procedures, affects the bonding performance and hydration of CSCs. Tooth specimens were filled with four CSC-containing products (ProRoot MTA: PM, Endocem MTA: EC, iRoot BP Plus: IB, and TheraCal LC: TC) and placed in either distilled water or blood for 7 days at 37 ℃. The push-out test and evaluations using an inverted microscope and scanning electron microscope (SEM) were performed to measure the bond strength and fracture mode. Energy-dispersive X-ray spectroscopy (EDS) was used to measure the elemental composition and the Ca/Si ratio. ²⁹ Si magic angle spinning nuclear magnetic resonance spectroscopy ( ²⁹ Si MAS NMR) analysis was conducted to investigate the structures of the calcium silicate, and the mean silicate length (MCL) was calculated. Blood contamination significantly reduced bond strength for PM and increased bond strength for IB; no significant changes were observed with EC or TC. Blood contamination increased the Ca/Si ratio of each specimen, which was associated with decreased hydration and MCL values. It also influenced cohesive, mixed, and adhesive fractures among different groups. Blood contamination impaired the mechanical reliability of most hydration-dependent CSCs due to disrupted silicate polymerization, with the exception of IB, which exhibited an anomalous increase in push-out bond strength. From a clinical standpoint, these findings highlight the importance of hemostasis before CSC placement and suggest that future CSC formulations should improve resistance to blood contamination to enhance patient care.

Objective: This study aims to evaluate the influence of opalescence in the color matching ability of dental composites. Methods: Single-disc samples were prepared using 10 commercially available composites (6 conventional, 3 simplified-shade, and 1 single-shade). Dual-color samples were created using Omnichroma, Ceram.X Sphere TEC (A3 shade), and DenFil (B2/C2 shade), with various cavity diameters in the center, which were then filled with the aforementioned 10 composites. Additionally, single-color samples were prepared using the 4 base composites mentioned above. The ΔE_Single-Dual were calculated as differences between single and dual samples. The color coordinates (CIE L ^* a ^* b ^* ) of the samples were measured using a spectrophotometer. The results of translucency parameters (TP) and opalescence parameters (OP) of the 10 composites were compared with ΔE measurement samples. Results: TP and OP generally had a linear correlation, and ΔE_Single-Dual mostly increased with cavity diameter. Regarding the correlation between ΔE_Single-Dual and TP, little correlation was observed in the conventional composite bases, but higher correlations were observed in the simplified- or single-shade composite bases. Regarding the correlation between ΔE_Single-Dual and OP, inverse correlations were observed in the conventional composite bases and simplified composite bases, but the single-shade composite base showed the linear correlations with OP. Conclusions: These findings highlight a potentially greater role for opalescence in the color matching ability of dental composites than previously acknowledged.

With the advent of 3D printing technologies in dentistry, the optimization of printing conditions has been of great interest, so this study analyzed the accuracy of 3D-printed temporary restorations of different sizes produced by digital light processing (DLP) and liquid crystal display (LCD) printers. Temporary restorations of 2-unit, 3-unit, 5-unit, 6-unit, and full-arch cases were designed and printed from a DLP printer using NextDent C&B or an LCD printer using Mazic D Temp (n = 10 each). The restorations were scanned, and each restoration standard tessellation language (STL) file was superimposed on the reference STL file, by the alignment functions, to evaluate the trueness through whole/point deviation. In the whole-deviation analysis, the root-mean-square (RMS) values were significantly higher in the 6-unit and full-arch cases for the DLP printer and in the 5-unit, 6-unit, and full-arch cases for the LCD printer. The significant difference between DLP and LCD printers was found in the 5-unit and full-arch cases, where the DLP printer exhibited lower RMS values. Color mapping demonstrated less shrinkage in the DLP printer. In the point deviation analysis, a significant difference in direction was exhibited in all the restorations from the DLP printer but only in some cases from the LCD printer. Within the limitations of this study, 3D printing was most accurate with less deviation and shrinkage when a DLP printer was used for short-unit restorations.

The purpose of this study was to observe whether the repetitive firing of dental zirconia caused changes in surface characteristics, S. mutans viability, and optical properties of zirconia. Dental zirconia blocks were sintered and randomly distributed into seven experimental groups: F0–F6. Except for F0, which only went through sintering, the additive firing was performed in order for F1–F6. Surface roughness, contact angle, S. mutans viability by fluorescence, and translucency parameter were measured. They were all highest after sintering (F0) and decreased after additive firings (F1–F6). The additive firing of zirconia after sintering decreased surface roughness, contact angle, S. mutans viability, and translucency. The number of firings after the first firing was not found to be critical in surface characteristics, S. mutans viability, and optical property. Changes in surface characteristics might have led to a decrease in S. mutans viability, while the change of translucency was not clinically significant. This implies that additive firing may prevent secondary caries under zirconia restorations, not compromising esthetic appearance.

This study compares the color stability of dental reinforced computer-aided design/computer-aided manufacturing (CAD/CAM) hybrid composite blocks to that of regular blocks. One hundred fifty disc-type specimens (n = 15) were prepared from five sets of hybrid composite blocks (Cerasmart-200/Cerasmart-300, KZR-CAD HR/KZR-CAD HR3, Estelite Block/ Estelite-P Block, Avencia Block/Avencia-P Block, Mazic Duro/Duro Ace). The specimen color and translucency parameter (TP) were assessed using a spectrophotometer before and after immersion in staining solutions (water, 10% ethanol, simulated red wine). Changes in color (ΔE) and translucency (ΔTP) of specimens were calculated. The data were analyzed using the analysis of variance (ANOVA) and Tukey’s post hoc test (p < 0.05). Microstructural features of the hybrid composite blocks were also examined using FE-SEM. Immersion in deionized water or 10% ethanol made no significant color or translucency changes (except for Avencia-P Block); however, the simulated red wine caused significant changes to the color and translucency of almost all specimens, especially after 4 weeks of immersion. The reinforced hybrid blocks (except for Estelite-P Block and Duro Ace) showed lower color stability than corresponding regular blocks. Avencia-P Block showed significantly reduced color stability compared to Avencia Block. Even in deionized water and 10% ethanol, Avencia-P Block showed perceptible ΔE and decreased translucency. Estelite Block/ Estelite-P Block and Mazic Duro/Duro Ace showed better color stability than the other materials tested.

The purpose of this study is to evaluate the shear bond strength (SBS) of a primer-treated ceramic bracket on dental zirconia and to compare it with conventional ceramic bracket bonding on surface-treated zirconia. Sintered and finished dental zirconia was sandblasted. Samples were divided according to the treated surfaces: no treatment (X), ceramic primer on zirconia (Z), ceramic primer on bracket base (B), and ceramic primer on both zirconia and bracket base (ZB). The ceramic bracket was bonded on zirconia and SBS was measured before (T₀) and after 10,000 cycles of thermocycling (T_f). The failed surfaces were examined under field emission scanning electron microscope (FE-SEM), and adhesive remnant index (ARI) was evaluated. SBS was significantly higher in ZB and significantly lower in X in both T₀ and T_f. There was no significant difference between Z and B. In X and B, adhesive failure occurred while ZB showed mixed failures. There was no apparent change in the zirconia surface except for the existence of some adhesive and resin remnants. The application of ceramic primer on the bracket base increased the bonding strength to the level of conventional bonding with fewer adhesive remnants. The highest bonding strength was obtained when the primer-treated bracket was bonded on the primer-treated zirconia.