Ivoclar Vivadent (Liechtenstein)

Color stability is crucial for dental materials to ensure they perfectly match a patient's tooth color. This is particularly challenging in photoresist-based additive manufacturing. Although some studies have addressed this issue, the exact causes of discoloration and ways to minimize it remain unclear. In this study, the intrinsic causes of discoloration in materials intended for 3D printing are investigated by examining thin-film samples (1200 µm) of various compositions, which are stored under different conditions. The samples are evaluated by measuring the UV-Vis absorption spectra at regular intervals to monitor changes. The findings reveal that both the composition of the formulations and the storage conditions significantly influence the discoloration behavior. Furthermore, methods have been developed to reduce or completely prevent discoloration. The use of photoinitiators with sterically demanding benzoyl moieties, as well as the addition of stabilizers, effectively decreases the intensity of emerging discoloration. Furthermore, incorporating the oxidizing agent cumene hydroperoxide (CHP) results in materials that maintain color stability.

Giri ve Ama: Tek kitle (bulk-fill) rezin kompozitler, tabakalama teknii ile uygulanan rezin kompozitlere gre avantajlar nedeniyle tercih edilmektedir. almamzn amac, farkl yerletirme tekniklerinin ve nlama srelerinin rezin kompozitlerin mikrosertlii

Abstract Lithium disilicate glass‐ceramics were discovered in the 1950s, and the evolution of the main target phase of these materials is well known. However, the lithium disilicate system is still an area of active research, especially when a secondary phase is introduced since the phase evolution of secondary phases is not currently understood. The present study examines the main target phases, as well as a secondary phase of lithium tantalate, via X‐ray diffraction. A large data set is obtained to investigate the evolution of all phases. It is found that the nucleation of the precursor lithium metasilicate phase is coupled to both the nucleation of the primary target phase, lithium disilicate, and the nucleation of lithium tantalate. A reaction equation describing this relationship is proposed.

Waste production associated with the use of non-degradable materials in packaging is a growing cause of environmental concern, with the polyurethane (PU) class being notorious for their lack of degradability. Herein, we incorporate photosensitive ortho-Nitrobenzyl units into PUs to achieve controllable photodegradability. We performed their photolysis in solution and thin films which can inform the design of degradable adhesives.

Tetraacylgermanes are known as highly efficient photoinitiators. Herein, the synthesis of mixed tetraacylgermanes 4 a–c and 6 a–e with a nonsymmetric substitution pattern is presented. Germenolates are crucial intermediates of these new synthetic protocols. The synthesized compounds show increased solubility compared with symmetrically substituted tetraacylgermanes 1 a–d. Moreover, these mixed derivatives reveal broadened n–π* absorption bands, which enhance their photoactivity. Higher absorption of these new compounds at wavelengths above 450 nm causes efficient photobleaching when using an LED emitting at 470 nm. The quantum yields are in the range of 0.15–0.57, depending on the nature of the aroyl substituents. On the basis of these properties, mixed‐functionalized tetraacylgermanes serve as ideal photoinitiators in various applications, especially in those requiring high penetration depth. The synthesized compounds were characterized by elemental analysis, IR spectroscopy, NMR and CIDNP spectroscopy, UV/Vis spectroscopy, photolysis experiments, and X‐ray crystallography. The CIDNP data suggest that the germyl radicals generated from the new tetraacylgermanes preferentially add to the tail of the monomer butyl acrylate. In the case of 6 a–e only the mesitoyl groups are cleaved off, whereas for 4 a–c both the mesitoyl and the aroyl group are subject to α‐cleavage.

Cyclopolymerizable monomers (CPMs) are rarely described as cross-linkers, as their most prominent feature is the ability to form soluble polymer chains. In this study, we design a dimalonate-based ...

Aim: To examine the relation wear resistance and microhardness of composite block, hybrid block, resin composite to provide convenient argument to clinical usage of materials. Methods: Conventional resin composite (IPS Empress direct, Ivoclar Vivadent), hybrid ceramic block (Enamic, Vita) and composite blocks (Lava Ultimate, 3M), (Hc block, Shofu), (BrilliantCrios, Coltene), (Cerasmart, GC) were investigated. Specimens (n=12 for each group) (n=12 for each group) were loaded in a chewing simulator together a thermal cycling (49 N force, 240.000 cycles, 1.5 mm lateral movement, 1.7 Hz frequency). Specimens were scanned with a Las-20 (Laserscanner, SD Mechatronic) and Vickers microhardness (VHN) was determined (200 grf, 10 s). Statistical analysis was performed with using spearman correlation coefficient. Results: A negative correlation determined for all groups (r=- 0.83). Correlation was observed only composite block group between microhardness and wear resistance and no correlation was found hybrid block and resin composite. Conclusion: Correlation has found between surface microhardness and abrasive wear resistance of the IPS Empress direct,Enamic, Brilliant Crios, Hc block, Cerasmart, Lava Ultimate materials.