Flexural Performance of Direct Resin Composite Restorative Materials Past Expiration Date

Objective This study' s purpose was to examine the flexural properties of five direct restorative resin composites stored up to 30 months after the expiration date. Materials and Methods Ambient-stored materials had pre-expiration date baseline flexure strength values as per ISO 4049 (n = 20). All materials were used per manufacturer guidelines, photopolymerized on both sides using a LED-based visible light curing unit, and stored in 0.2M phosphate buffered saline. At 24 hours, specimens were stressed to failure in three-point bend at a 0.5 mm/min cross head speed. Additional samples were made at 3, 6, 9, 12, 15, 18, 24, and 30 months past expiration date. Young’s modulus (flexural) was ascertained using the linear slope of the stress-stain curve. Statistical Analysis The mean data was found to contain a non-normal distribution and irregular variance which was compared using Kruskal–Wallis with Dunn’s posthoc testing.Also, Pearson’s correlation analysis was used to identify possible similar degradation behavior between products within both flexure strength and modulus determinations. A 95% level of confidence (α = 0.05) was used. Results Materials maintained similar to baseline flexure strength and modulus for up to 15 months past expiration date with two materials being similar at 30 months. However, clinicians were still advised to follow expiration dates, as resin composite degradation mechanisms are complex and vital constituents might degrade that are not overtly identified by clinical handling characteristics. No dental shelf life standards exist and manufacturers are requested to provide protocol information used in determining shelf life expiration.

Synthesis, Characterization, and Visible Light Curing Capacity of Polycaprolactone Acrylate

Polycaprolactone (PCL) is drawing increasing attention in the field of medical 3D printing and tissue engineering because of its biodegradability. This study developed polycaprolactone prepolymers that can be cured using visible light. Three PCL acrylates were synthesized: polycaprolactone-530 diacrylate (PCL530DA), glycerol-3 caprolactone triacrylate (Glycerol-3CL-TA), and glycerol-6 caprolactone triacrylate (Glycerol-6CL-TA). PCL530DA has two acrylates, whereas Glycerol-3CL-TA and Glycerol-6CL-TA have three acrylates. The Fourier transform infrared and nuclear magnetic resonance spectra suggested successful synthesis of all PCL acrylates. All are liquid at room temperature and can be photopolymerized into a transparent solid after exposure to 470 nm blue LED light using 1% camphorquinone as photoinitiator and 2% dimethylaminoethyl methacrylate as coinitiator. The degree of conversion for all PCL acrylates can reach more than 80% after 1 min of curing. The compressive modulus of PCL530DA, Glycerol-3CL-TA, and Glycerol-6CL-TA is 65.7±12.7, 80.9±6.1, and 32.1±4.1 MPa, respectively, and their compressive strength is 5.3±0.29, 8.3±0.18, and 3.0±0.53 MPa, respectively. Thus, all PCL acrylates synthesized in this study can be photopolymerized and because of their solid structure and low viscosity, they are applicable to soft tissue engineering and medical 3D printing.

Perbandingan Kekasaran Permukaan Resin Komposit Nanofiller pada Perendaman Saliva pH Asam

Nanofiller resin composite is a material used for dental restoration which will be in oral cavity so that interacted with the saliva. Saliva pH changes influenced by several factors, including bacteria in the oral cavity, enzymes, hormones and diet. Acid saliva can cause degradation in the composite, this degradation affects the surface roughness of resin composite. The purpose of this study is to compare surface roughness of nanofiller resins composite for 7 and 10 days of immersion in acid saliva.The samples used in this study were cylindrical mould dimension of diameter 5mm x 2mm, then polymerized with a visible light curing unit for 20s. Specimens immersed in acid artificial saliva (pH ± 4) for 7 and 10 days(4 specimens each group)and then stored in incubator at the temperature of 37ºC. The instrument used to measure surface roughness of resin composite was Surface Roughness Measuring Instrument (Surfcom 120A) that expressed in units of µm.Data were analyzedand the result obtainedwas p = 0.263 (p> 0.05), which mean there were no significant differences in the mean roughness of nanofillerresins compositesurface that were immersed in acidic pH for 7 and 10 days. The conclusion of this study was thatthe surface roughness of nanofiller resins composite immersed in acid saliva for 10 days is not rougher than which immersed for 7days.

A synergistic effect of a ferrocenium salt on the diaryliodonium salt-induced visible-light curing of bisphenol-A epoxy resin

Diaryliodonium and ferrocenium salts undergo photo-electron transfer (PET) to initiate photopolymerizations under a halogen lamp.