Effect of aging and bleaching on the color stability and surface roughness of a recently introduced single-shade composite resin.

OBJECTIVES: To assess the effects of aging and bleaching procedures on the color stability and surface roughness of a new single-shade composite versus multi-shade composite resins. METHODS: A single-shade composite resin (Charisma Diamond One, CDO) and 3 multi-shade composite resins (Tetric NCeram, Filtek Z350 XT, Clearfil Majesty Posterior) were tested. Thirty specimens of each material were subjected to one of the aging procedures respectively: immersion in distilled water (12 days/37 °C), immersion in coffee (12 days/37 °C), or water thermocycling (10,000 cycles/5-55 °C). All specimens underwent in-office bleaching after aging. Kruskal-Wallis tests and analysis of variance were used for statistical analysis (α=0.05). RESULTS: All materials exhibited a change of color (ΔE00), translucency (RTP), whiteness (WID) and surface roughness parameters (Sa,Sv) after aging and bleaching procedures. CDO showed the highest ΔE00 among all resins with the highest RTP value, regardless of the aging procedures. Immersion in coffee led to the significantly highest ∆E00 values and lowest RTP values for nearly all resins. Positive ΔWID1 (WID(bleaching)-WID(baseline)) values were found in distilled water immersion and thermocycling groups, while negative ΔWID1 values were found in the coffee immersion group for all materials. Besides, positive ΔWID2 (WID(bleaching)-WID(aging)) values were found in all aging groups for nearly all materials. All materials showed an increasing trend in Sa and Sv after bleaching. CONCLUSIONS: CDO showed more pronounced discoloration than multi-shade composite resins. Although the whiteness of all resins increased after bleaching, none was completely restored in the coffee immersion group. Bleaching significantly increased the surface roughness of all materials. CLINICAL SIGNIFICANCE: Charisma Diamond One is more susceptible to discoloration, which may affect its long-term success rate. Bleaching could partially reduce the color change of the composite resins but did not return them completely to their original state. The roughness of the resins increased after bleaching, prompting dentists to repolish them after bleaching.

Reaction-Driven Dynamic and Reversible Transformations of Au Single Atoms and Au-Zr Alloys on Zirconia for Efficient Acetylene Hydrochlorination.

Catalysis involving gold supported on metal oxides has undergone extensive examination. However, the nature of the catalytic site under actual reaction conditions and the role of the support continue to be vigorously debated. This study addresses these issues through experimental investigations and theoretical simulations. We explore a novel catalytic mechanism that employs dynamic single-atom catalysis for the hydrochlorination of acetylene. This catalytic mechanism occurs in defective ZrO2-supported Au-Zr single-atom alloys. Specifically, the dynamic single-atom catalysis is a result of the mobility of the gold cation, which is accelerated by Cl radicals and strongly couples with the abundant unsaturated surface sites of ZrO2 in a synergistic manner. As a result, the Au electronic structure dynamically evolves, leading to a decrease in the addition reaction energy barrier. Notably, the Au cation can detach from the Au-Zr alloy structure to catalyze the hydrochlorination of acetylene near the Zr-Ov-Zr sites and then reintegrate back into the Au-Zr alloy structure upon completion of the reaction. This study underscores the significance of dynamic active sites under reaction conditions and their pivotal role in catalysis.

Fully digital workflow for replicating treatment dentures: A technique for jaw relation transfer and dynamic occlusal adjustment.

This technique report presents a novel method of digitally replicating a treatment denture and converting it into a definitive denture. The procedure accurately duplicates the appearance of the mucosal surface and border of the treatment dentures, mounts the jaw relation on a virtual articulator to arrange artificial teeth, and optimizes the occlusion based on recorded mandibular motion tracks. This technique uses personalized jaw relation transfer and dynamic occlusal adjustment to establish balanced occlusion, which accomplishes the digital duplication of the treatment denture with high accuracy and minimal effort.

Comparative study on the impact-sliding wear behaviour of CAD/CAM resin-ceramic materials and tooth enamel.

OBJECTIVES: To compare the impact-sliding wear of different CAD/CAM resin-ceramic materials and tooth enamel, and explore the corresponding wear damage mechanism. METHODS: Human tooth enamel (EN), Vita ENAMIC (Vita, VE), Lava Ultimate (3 M, LU), and GC CERASMART (GC, CS) were used in this study. The hardness, elastic modulus, and roughness values of the samples were measured. Further, impact-sliding wear tests were performed in a ball-on-flat configuration with spherical zirconia antagonists and the coefficients of friction (CoF) were recorded simultaneously. Additionally, a white light interferometer was used to determine the volume losses and scanning electron microscopy was used to observe the wear morphology of the wear scars and the damage feature in the vertical sections to clarify the damage mechanism during the impact-sliding wear test. RESULTS: EN exhibited the highest elastic modulus and CoF, followed by VE, LU, and CS. The hardness and roughness of EN and VE were similar and were higher than those of LU and CS. Throughout the wear tests, VE exhibited the highest volume loss, whereas CS exhibited the lowest. The wear damage characteristics of VE were similar to those of EN, displaying brittle fractures of inorganic substances and plastic deformation of organic substances in the impact part, exhibiting plough marks in the sliding parts. In the case of LU and CS, the entire wear areas displayed plastic deformation of the resin matrix, exfoliation of the filler particles, and plough marks. SIGNIFICANCE: Enamel and polymer-infiltrated ceramic network materials exhibit similar wear damage modes. Additionally, the high-density nanocomposite resin material is the most resistant to impact-sliding wear from a tribological perspective.

Effects of Hydrofluoric Acid Concentration and Etching Time on the Bond Strength to Ceramic-coated Zirconia.

PURPOSE: To evaluate the effects of different hydrofluoric acid (HF) concentrations and etching times on the surface topography, roughness, and resin bond strength to ceramic-coated zirconia (CC), and to compare them with the effects of alumina air-abrasion combined with 10-MDP (AA). MATERIALS AND METHODS: AA and CC specimens were divided into 12 groups (N = 10). The CC groups were etched with HF at different concentrations (5% or 9.5%) for various durations (0 min, 1 min, 2 min, 3 min, 5 min or 10 min). The surface morphology was analyzed using SEM. Energy-dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD) were performed for chemical and crystalline-phase analyses. Surface roughness (Ra) and shear bond strength (SBS) were recorded and statistically analyzed. RESULTS: The SBS of CC groups initially increased, but then decreased with etching time for both HF acid concentrations. The 9.5% HF group displayed more marked topographical changes and higher Ra compared with the 5% HF group for the same etching period. Mean SBS was lower in the AA group compared with the CC groups etched with 5% HF for 2-10 min and 9.5% HF for 1-3 min (p < 0.05). CONCLUSIONS: Different HF concentrations and etching times influenced the surface topography, roughness, and resin bond strength of/to ceramic-coated zirconia. Etching with 5% HF for 5 min and with 9.5% HF for 2 min, respectively, provided the highest SBS.

Effect of Airborne-Particle Abrasion Protocols and MDP-based Primer on the Bond Strength of Highly Translucent Zirconia.

PURPOSE: To evaluate the effects of airborne-particle abrasion and MDP (methacryloyloxydecyl dihydrogen phosphate)-based primer treatment on the strength of resin bonds to highly translucent zirconia. MATERIALS AND METHODS: Eight groups (n = 20 per group) of specimens were prepared with airborne-particle abrasion treatments (0.1-, 0.3-, or 0.6-MPa pressure) or not (untreated control) and MDP-based primer (treated) or not (untreated). Shear bond strength (SBS) tests were performed on the composite-to-ceramic bonded specimens either with or without thermocycling. After airborne-particle abrasion, the surface topography was evaluated by white light interferometry, and a phase analysis was conducted with x-ray diffraction (XRD). Surface roughness (Ra), surface energy (SE), and SBS measurements were statistically analyzed using either Tukey's HSD or the Kruskal-Wallis test, based on applicability. Lastly, the failure mode was observed by optical microscope and scanning electron microscope. RESULTS: Airborne-particle abrasion resulted in significantly larger Ra (p < 0.05), especially with higher treatment pressures. Treatment with MDP-based primer caused significantly higher SE and SBS than airborne-particle abrasion alone (p < 0.05), both with and without aging. CONCLUSION: MDP-based primer can enhance the bond strength and reduce hydrolytic aging of the bonded interface for highly translucent zirconia, exceeding the effects of airborne-particle abrasion. It is recommended that MDP-based primer treatment be applied with a composite cement containing adhesive phosphate monomer.

Boron-doped carbon nanodots dispersed on graphitic carbon as high-performance catalysts for acetylene hydrochlorination.

Boron-doped carbon nanodot materials, comprising evenly distributed BC3-nanodots in a layered carbon matrix, are prepared through a pre-assembly assisted carbonization synthetic strategy. The prepared materials are endowed with high electron affinity and distortion resistance, which provides a stable framework while generating affinity to substrates.