OBJECTIVE: This study investigated the influence of photoinitiator types on degree of conversion (DC), rate of polymerization (RP), flexural strength (FS), flexural modulus (FM), and light transmittance (LT) of filled and unfilled light-curable resin cements through different thicknesses and shades of lithium disilicate ceramics.
METHODS: Lithium disilicate ceramic discs (IPS Emax Press, background [0.0], 0.5, 1.0, 2.0, 3.0, and 4.0 mm, shades A1 and BL3) were prepared. Experimental resin-based cements [TEGDMA/BisGMA (50/50 mass%)] were prepared using either camphorquinone (CQ)/amine (0.44/1.85 mol%) or TPO (0.44 mol%)], and a micro and nanofiller loads of nil (unfilled); 40/10 mass%; and 50/10 mass%). Resin cements (0.2 mm thick) were placed on the lower surface of the ceramic specimens and light-activated for 30 s from the upper surface using a Bluephase Style curing light (exitance at tip: 1236 mW/cm2 ± 1.20). LT and distribution of irradiance through the ceramics were measured using a UV-vis spectrometer and a beam profile camera, respectively (n = 3). The DC and RP were measured in real-time using mid infrared spectroscopy in attenuated total reflectance (ATR) mode (n = 3). FS and FM were measured using a universal testing machine (n = 5). Statistical analyses were performed on LT, DC, RP, FS, and FM data using a general linear model, and supplementary ANOVA and post hoc Tukey multiple comparison test were also performed (α = .05).
RESULTS: Thicknesses, shades, photoinitiator type, and fillers load significantly influenced the optical and mechanical characteristics of the resin-based materials (p < 0.05). The BL3 shade ceramic provided higher values of DC, RP, FS, FM, and LT compared with the A1 shade (p < 0.05). Increasing ceramic thickness decreased the properties of the resin-based materials (p < 0.05). Generally, TPO improved mechanical properties of the resin cement compared with CQ (p < 0.05).
CONCLUSIONS: The luting process of indirect restorations may be improved by using high molar absorptivity, more reactive, and more efficient photoinitiators such as TPO, as opposed to conventional CQ. The use of such initiator may allow the placement of thicker and more opaque indirect restorations.

The effect of polyamide 11 (PA11) on the thermal stability and light transmittance properties of silicone-based thermoplastic vulcanizates (TPVs) has been investigated. The blends were prepared through a dynamic vulcanization process by adding 15, 30, and 45 wt% PA11 to the silicon-based TPVs, respectively. The effect of PA11 on the dispersion of silicone rubber in the TPVs after dynamic vulcanization was characterized by a scanning electron microscope (SEM), the thermal stability of the compounds was evaluated through the changes in mechanical performance in the thermo-oxidative aging process, and the light transmittance of TPVs was measured by a haze meter. The results showed that adding PA11 to silicone-based TPVs caused a decrease in the size of the silicone rubber particles after dynamic vulcanization, resulting in improved dispersion. Due to this, by increasing the compatibility between the segments through silicone\'s effective dispersion, the amount of light absorption was reduced, and the amount of light transmittance was increased. Finally, according to the results of the thermal aging test, it was found that TPVs with 30 and 45 wt% PA11, respectively, showed outstanding thermal resistance after aging at 160 °C and 168 h and did not melt down.

Transparency to UV-Vis light and radiopacity of dental resin composites containing zirconia (ZrO2) fillers were investigated. The transparency of the resin composite containing porous ZrO2 spheres was much higher than that containing irregularly shaped ZrO2 particles. Calcination of the porous ZrO2 spheres at high temperatures led to dramatically reduced specific surface areas and pore volumes. The transparency of the resin composite containing the calcined porous ZrO2 spheres drastically decreased as the calcination temperature increased. Then, the enhanced UV-Vis transmittance of the resin composite containing porous ZrO2 spheres is attributed to the concentration and physical characteristics of the pores. The radiopacity of the resin composites containing porous ZrO2 spheres increased slightly with increasing calcination temperature. This study revealed that the internal structure of the ZrO2 fillers mainly influenced in the UV-Vis light transmittance of the resin composites.

OBJECTIVE: The aim of this in vitro study was to evaluate the light transmission through five different resin-matrix composites regarding the inorganic filler content.
METHODS: Resin-matrix composite disc-shaped specimens were prepared on glass molds. Three traditional resin-matrix composites contained inorganic fillers at 74, 80, and 89 wt. % while two flowable composites revealed 60 and 62.5 wt. % inorganic fillers. Light transmission through the resin-matrix composites was assessed using a spectrophotometer with an integrated monochromator before and after light curing for 10, 20, or 40s. Elastic modulus and nanohardness were evaluated through nanoindentation\'s tests, while Vicker\'s hardness was measured by micro-hardness assessment. Chemical analyses were performed by FTIR and EDS, while microstructural analysis was conducted by optical microscopy and scanning electron microscopy. Data were evaluated using two-way ANOVA and Tukey\'s test (p < 0.05).
RESULTS: After polymerization, optical transmittance increased for all specimens above 650-nm wavelength irradiation since higher light exposure time leads to increased light transmittance. At 20- or 40-s irradiation, similar light transmittance was recorded for resin composites with 60, 62, 74, or 78-80 wt. % inorganic fillers. The lowest light transmittance was recorded for a resin-matrix composite reinforced with 89 wt. % inorganic fillers. Thus, the size of inorganic fillers ranged from nano- up to micro-scale dimensions and the high content of micro-scale inorganic particles can change the light pathway and decrease the light transmittance through the materials. At 850-nm wavelength, the average ratio between polymerized and non-polymerized specimens increased by 1.6 times for the resin composite with 89 wt. % fillers, while the composites with 60 wt. % fillers revealed an increased ratio by 3.5 times higher than that recorded at 600-nm wavelength. High mean values of elastic modulus, nano-hardness, and micro-hardness were recorded for the resin-matrix composites with the highest inorganic content.
CONCLUSIONS: A high content of inorganic fillers at 89 wt.% decreased the light transmission through resin-matrix composites. However, certain types of fillers do not interfere on the light transmission, maintaining an optimal polymerization and the physical properties of the resin-matrix composites.
CONCLUSIONS: The type and content of inorganic fillers in the chemical composition of resin-matrix composites do affect their polymerization mode. As a consequence, the clinical performance of resin-matrix composites can be compromised, leading to variable physical properties and degradation.

Edible coating and film from chitosan and incorporating it with the action of ZnONPs on active phenol compounds from extracts of pomegranate peel (PPE) The physical and chemical properties of edible films composed of zinc oxide ZnONPs and active phenol compounds extracted from pomegranate peel (PPE) were investigated. Adding ZnONPs with active phenol compounds from extracted pomegranate peel(PPE) to chitosan films can provide safe edible films, decrease microbial growth and consequently prolong the shelf life of pomegranates, as well as improve the physiochemical stability of the pomegranate. The substances used in this experiment were film with a (A) extract of pomegranate peels (PPE), 5% (0.1%), (B)ZnONPs 1% (0.02%), (C) ZnONPs 2% (0.04%), (D) ZnONPs 3% (0.06%), (E) ZnONPs 1%/PPE1% (0.02%), (F) ZnONPs 2%/PPE2% (0.04%), (G) ZnONPs 3%/PPE3% (0.06%) wt% of chitosan on quality attributes and prolonging the shelf life of pomegranates were stored in plastic containers at 2 °C and 90-95% relative humidity for 20 days. The treatments of (G) ZnONPs 3%/PPE3% (0.06%) loaded on chitosan as well as chitosan and (D) ZnONPs 3% (0.06%) reduced the weight loss, had excellent microbial count until 20 days of storage, and recorded the lowest microbial count and mould & yeast colonies. Other chemical properties, such as total soluble solids content, acidity, anthocyanin content, firmness, and ascorbic acid, were investigated. Results indicated that ZnONPs 3%/PPE3% (0.06%) loaded on chitosan or ZnONPs 3% (0.06%) are the best treatments for preserving pomegranate arils. It was found that the best measurements were that the film-forming nan emulsion solutions decreased by E% 110 nm and B% 134 nm. Nano followed treatment, F% 188.7 nm, compared to nano edible films, which were A 0% 1312 nm.

In dentistry, clinicians mainly use dual-cured or light-cured resin-matrix cements to achieve a proper polymerization of the organic matrix leading to enhanced physical properties of the cement. However, several parameters can affect the polymerization of resin-matrix cements. The main aim of the present study was to perform a scoping review on the degree of conversion (DC) of the organic matrix, the polymerization, and the light transmittance of different resin-matrix cements used in dentistry. A search was performed on PubMed using a combination of the following key terms: degree of conversion, resin cements, light transmittance, polymerization, light curing, and thickness. Articles in the English language published up to November 2022 were selected. The selected studies\' results demonstrated that restorative structures with a thickness higher than 1.5 mm decrease the light irradiance towards the resin-matrix cement. A decrease in light transmission provides a low energy absorption through the resin cement leading to a low DC percentage. On the other hand, the highest DC percentages, ranging between 55 and 75%, have been reported for dual-cured resin-matrix cements, although the polymerization mode and exposure time also influence the DC of monomers. Thus, the polymerization of resin-matrix cements can be optimized taking into account different parameters of light-curing, such as adequate light distance, irradiance, exposure time, equipment, and wavelength. Then, optimum physical properties are achieved that provide a long-term clinical performance of the cemented restorative materials.

The residual stress phenomenon in the injection process of an optical lens affects the quality of optical components, and the refractive error caused by geometric errors is the most serious, followed by the degradation of the accuracy and function of optical components. It is very important to ensure that the lens geometry remains intact and the refractive index is low. Therefore, a parameter design method for an optical liquid silicon injection molding was proposed in this study. Wavelet analysis was applied to the noise reduction and feature extraction of the cavity pressure/pressure retaining curve of the injection molding machine, and multiple identifiable performance evaluation methods were used to identify and optimize the parameters of the molding process. Taking an automotive LED lens as an example, Moldex3D simulation software was used to simulate the molding of an LED lens made of LSR material, and two key injection molding factors, melt temperature and V/P switching point, were analyzed and optimized. In this paper, the transmittance and volume shrinkage of LED lenses are taken as quality indexes, and parameters are optimized by setting different V/P switching points and melt temperature schemes. The experimental results show that the residual stress is negatively correlated with transmittance, and the higher the residual stress, the lower the transmittance. Under the optimum process parameters generated by this method, the residual stress of plastic parts is significantly optimized, and the optimization rate is above 15%. In addition, when the V/P switching point is 98 and the melt temperature is 30 °C, the product quality is the best, the volume shrinkage rate is the smallest, and the size is 2.895%, which also means that the carbon emissions are the lowest.

BACKGROUND: This study aimed to evaluate the color matching, light transmittance, and reflectance characteristics of the novel flowable resin composite OCF-001 (OCF).
METHODS: Fifty-four resin composite molds were made with simulated class I cavities of A2, A3, and A4 shades by filling the rubber mold interspace with Estelite Sigma Quick (ESQ), Gracefil Putty (GP) and Filtek Supremme Ultra (FSU). After applying the adhesive, three different flowable resin composites (n = 6), OCF, Gracefil LoFlo (GLF), and Supreme Ultra Flowable (SUF), were used to fill the cavities. A colorimeter was used to measure the color parameters (CIEDE2000). The color measurements were taken immediately and after 28 days. Data were analyzed using the nonparametric Kruskal-Wallis (α = 0.05) and Wilcoxon tests. The light transmittance and reflection characteristics were measured with a black background using a spectrophotometer under D65 illumination.
RESULTS: The ΔE00, and ΔC of OCF was lower than other tested materials in A2 and A3 shades both immediately and after 28 days. OCF showed the highest transmittance characteristic, and a relatively stable reflectance curve in all the wavelengths.
CONCLUSIONS: OCF showed better shade matching with the surrounding shades of A2 and A3, a relative uniform reflectance and higher light transmission properties.

OBJECTIVE: A crucial step in the preparation of yttria-stabilized zirconia materials (YSZ) is the final sintering step. Sintering parameters affect phase composition, grain growth and porosity of the material which, in turn, influence both mechanical and optical properties. Discrepancies of + /- 5% are common between actual and displayed firing temperatures depending on sintering furnace brand and condition. The aim of this study was therefore to investigate how such sintering temperature deviations in dental furnaces compared to the recommended firing protocols affected certain material properties of different yttria-stabilized zirconia materials.
METHODS: Disc-shaped specimens were made from four different translucent and high translucent YSZ-powders and analysed regarding crystal structure; unit cell volume for the c, t, and t\' -phases along with the tetragonality for the t and t\' phases. Biaxial flexure strength and the spectral transmittance through the ceramic specimens were also measured.
RESULTS: Deviations of 5% from the sintering temperature recommended for YSZ materials with different yttria content influenced material properties such as light transmittance, flexural strength, crystal phase fractions, tetragonality, and grain growth. Too low temperature resulted in decreased strength for some of the translucent zirconia materials, while others where less affected. Light transmittance varied depending on several factors such as grain size, crystal phase fractions and binder content in the start material prior to pre-sintering.
CONCLUSIONS: The use of high quality, wellcalibrated furnaces is crucial when sintering YSZ materials to avoid unwanted material changes.
CONCLUSIONS: Deviations of 5% from the sintering temperature recommended for YSZ materials with different yttria content influence material properties such as light transmittance, flexural strength, crystal phase fractions, tetragonality, and grain growth. Too low temperature results in decreased strength for some translucent zirconia materials, while others are less affected. Light transmittance varies depending on several factors such as grain size, crystal phase fractions and binder content in the start material prior to pre-sintering. Consequently, the use of high quality, well-calibrated furnaces is crucial when sintering YSZ materials to avoid unwanted material changes.

Cryogen spray cooling (CSC) is widely applied in laser dermatologic surgery to minimize the risk of non-specific epidermal thermal damage caused by the competitive laser energy absorption of epidermal melanin. However, the light absorption and attenuation by cryogen film and subsequent frost formation on the skin surface during CSC are needed to be investigated by using R-134a, R-404A, and R-32. A spray system equipped with an integrating sphere-based light collection apparatus was constructed to evaluate the time-resolved laser transmittance and spectral absorption characteristics induced by R-134a, R-404A, and R-32 sprays, under the clinical-used 755-nm and 1064-nm laser irradiations. No obvious light absorption peaks exist in the wavelengths of 370-1400 nm. R-404A produces the largest average light absorbance (0.089), as compared to those of R-134a (0.066) and R-32 (0.068) in the near-infrared range (780-1400 nm). Given the lowest boiling point and highest latent heat of R-32, the evaporation of liquid film and melting of subsequent frost are promoted, leading to smallest light attenuation. R-32 spray shows great potential in clinics owing to its high light transmittance, small light absorption, and high cooling capability. For R-32 spray, the durations between spurt termination and laser irradiation are recommended to be 8-100 ms and 13-100 ms with average light transmittances of 86% and 95% under 755-nm and 1064-nm laser irradiations.