Effect of different light curing methods on mechanical and physical properties of resin-cements polymerized through ceramic discs

OBJECTIVE: The aim of this study was to compare the polimerization ability of three different light-curing units (quartz tungsten halogen, light-emitting diodes and plasma arc) and their exposure modes (high-intensity and soft-start) by determination of microhardness, water sorption and solubility, and diametral tensile strength of 5 dual-curing resin cements. Material and methods: A total of 720 disc-shaped samples (1 mm height and 5 mm diameter) were prepared from different dual-curing resin cements (Duolink, Nexus, Bifix-QM, Panavia F and RelyX Unicem). Photoactivation was performed by using quartz tungsten halogen (high-power and soft-up modes), light-emitting diode (standard and exponential modes) and plasma arc (normal and ramp-curing modes) curing units through ceramic discs. Then the samples (n=8/per group) were stored dry in the dark at 37°C for 24 h. The Vickers hardness test was performed on the resin cement layer with a microhardness tester (Shimadzu HMV). For sorption and solubility tests; the samples were stored in a desiccator at 37°C and weighed to a constant mass. The samples were weighed both before and after being immersed in deionized water for different periods of time (24 h and 7 days) and being desiccated. The diametral tensile strength of the samples was tested in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by nonparametric Kruskal Wallis and Mann-Whitney U tests at 5% significance level. RESULTS: Resin cement and light-curing unit had significant effects (

The cytotoxicity of resin composites cured with three light curing units at different curing distances

Objective: The purpose of this study was to compare the effect of light curing distance on the cytotoxicity of five resin composites cured with three high-power light curing units. Study design: Seven cylindrical discs of each material (Grandio ®, Voco; Filtek ? Z250, 3M ESPE; Clearfil ? AP-X, Kuraray Co. Ltd.; Aelite ? LS, Bisco Inc. and Simile ®, Pentron) were cured. For curing, soft-up mode of quartz-tungsten-halogen, exponential mode of light emitting diode for 20 s, and ramp-curing mode of plasma arc light curing units for 6 s were used. The curing tip distances were determined as 2 and 9 mm and controlled via the use of metal rings. After ageing the samples for 24 and 72 hours in Dulbecco?s Modified Eagle Medium/Ham?s F12 (DMEM/F12), cytotoxicity of the extracts to cultured fibroblasts (L 929) was measured by using MTT (tetrazolium salt 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay. The degree of cytotoxicity for each sample was determined according to the reference value represented by the cells in a pure culture medium. Statistical significance was determined using multifactorial analysis of variance. Results: The type of resin composite (p<0.05), light curing unit (p<0.05), curing tip distance (p<0.05) and evaluation period factor (p<0.05) had statistically significant cytotoxic effects on L?929 mouse fibroblast cells. However, when the tested materials polymerized at both distances (2 mm and 9 mm) in both evaluation periods (24h and 72h), there was no significant difference in the mean CSR% values obtained when the quartz-tungsten-halogen, light emitting diode and plasma arc light curing units were used (p=0.184, F=1.448). Conclusions: The results of this study suggest that the light curing units and resin composites should be harmonized to one another and the curing distance between the tip of the light curing unit and the restoration surface should be as close as possible in order to achieve maximal biocompatibilit

The effect of light curing units and modes on cytotoxicity of resin-core systems

Objective: The aim of this study was to compare the cytotoxic effects of various resin-based core materials that were cured with three light curing units (LCUs) in different modes on L?929 mouse fibroblast cells over 24 h and 72 h periods. Study design: Eighty-four cylindrical discs (2 mm in thickness and 6 mm in diameter) of each material (Rebilda, Voco; Build-It FR, Pentron; Clearfil DC Core, Kuraray and Bis-core, Bisco) were cured by QTH LCU (soft-up and high-power modes), LED LCU (exponential and standard modes) and PAC LCU (normal and ramp-curing modes). Then the samples were aged for 24 and 72 hours in Dulbecco?s Modified Eagle Medium/Ham?s F12 (DMEM/F12). After each ageing interval, cytotoxicity of the extracts to cultured fibroblasts (L 929) was measured by MTT assay. The degree of cytotoxicity for each sample was determined according to the reference value represented by the cells with a pure culture medium. Statistical significance was determined by a multifactorial analysis of variance followed by one-way ANOVA and Tukey?s post-hoc test or independent t tests. Results: Data showed that there are significant differences among resin based core materials, LCUs, curing modes and time factors (p < 0.001). The test materials cured with the QTH and LED demonstrated statistically higher cell survival rates when compared with those cured with the PAC (p < 0.001). Conclusions: Differential toxic effects of the resin-based core materials cured with QTH, LED and PAC on the fibroblast cells may prove to be very important when suitable resin-core systems, LCUs and curing modes are used for operative restorations

The Effect of Irradiation Distance on Microhardness of Resin Composites Cured with Different Light Curing Units

Objectives: The aim of this study was to compare the microhardness of five different resin composites at different irradiation distances (2 mm and 9 mm) by using three light curing units (quartz tungsten halogen, light emitting diodes and plasma arc). Methods: A total of 210 disc-shaped samples (2 mm height and 6 mm diameter) were prepared from different resin composites (Simile, Aelite Aesthetic Enamel, Clearfil AP-X, Grandio caps and Filtek Z250). Photoactivation was performed by using quartz tungsten halogen, light emitting diode and plasma arc curing units at two irradiation distances (2 mm and 9 mm). Then the samples (n=7/per group) were stored dry in dark at 37°C for 24 h. The Vickers hardness test was performed on the resin composite layer with a microhardness tester (Shimadzu HMV). Data were statistically analyzed using nonparametric Kruskal Wallis and Mann-Whitney U tests. Results: Statistical analysis revealed that the resin composite groups, the type of the light curing units and the irradiation distances have significant effects on the microhardness values (P<.05). Conclusions: Light curing unit and irradiation distance are important factors to be considered for obtaining adequate microhardness of different resin composite groups.PubMe

PENAMBAHAN LIMBAH KALENG BEKAS DENGAN BENTUK SERAT BERGELOMBANG PADA CAMPURAN BETON TERHADAP SIFAT MEKANIS BETON

Beton merupakan salah satu elemen penting yang digunakan dalam suatu konstruksi. Misalnya untuk bangunan gedung, penempatan beton biasanya digunakan pada elemen balok, kolom maupun plat lantai. Tidak hanya itu beton juga dapat digunakan dalam fungsi lain contohnya jika kita menenggunakan beton dalam bangunan air seperti gorong-gorong, drainase, bendungan dan lain sebagainya. limbah kaleng bekas merupakan limbah anorganik dan tidak dapat terurai dan tentunya membawa dampak negative bagi lingkungan terutama bagi Kesehatan manusia oleh sebab itu di perlukan penanganan pada limbah padat ini. Limbah kaleng bisa berupa limbah dari kaleng bekas makanan,kaleng susu,cat dan lain lain yang sangat banyak kita jumpai di sekitar kita. Limbah dari kaleng dapat di jadikan serat kaleng yang di modifikasi menjadi serat serat ukuran tertentu dan dapat di jadikan alternatif untuk peningkatan mutu beton. Untuk mengetahui pengaruh dari ditambahkannya limbah kaleng bekas minuman terhadap mutu beton dengan variasi limbah kaleng minuman 0%, 0,05%, 0,075%, 0,100% dan 0,125%. Dengan bentuk serat bergelombang dengan ukuran serat 60 mm X 3 mm dengan serat berbentuk gelombang, Untuk pengujian kuat tekan dan kuat tarik menggunakan benda uji silinder dengan ukuran 15 x 30 cm, hari sedangkan untuk kuat lentur menggunakan benda uji balok dengan ukuran 15 x 15 x 60 cm, Semua sampel di uji saat beton berusia 28 . Dari hasil penelitian beton campuran serat kaleng aluminium didapatkan hasil nilai optimum kuat tekan beton sebesar 0,065% dengan nilai 21,17 MPa, kuat tarik belah sebesar 0,066% dengan nilai 2,45 MPa, dan kuat tarik lentur sebesar 0,060% dengan nilai 5,88 MPa. Dari pengujian Kuat Tekan. Kuat Tarik Belah dan Kuat Tarik Lentur menunjukan mengalami kenaikan mutu dalam persentase 0,05%, 0,075% dan mengalami penuruan mutu di persentase 0,100% dan 0,125%,Uji hipoteris membuktikan bahwa terdapat pengaruh dari penggunaan serat kaleng aluminium pada beton berserat

Light transmittance of zirconia as a function of thickness and microhardness of resin cements under different thicknesses of zirconia

Objective: The objective of this study was to compare microhardness of resin cements under different thicknesses of zirconia and the light transmittance of zirconia as a function of thickness. Study design: A total of 126 disc-shaped specimens (2 mm in height and 5 mm in diameter) were prepared from dual-cured resin cements (RelyX Unicem, Panavia F and Clearfil SA cement). Photoactivation was performed by using quartz tungsten halogen and light emitting diode light curing units under different thicknesses of zirconia. Then the specimens (n=7/per group) were stored in dry conditions in total dark at 37°C for 24 h. The Vicker's hardness test was performed on the resin cement layer with a microhardness tester. Statistical significance was determined using multifactorial analysis of variance (ANOVA) (alpha=.05). Light transmittance of different thick - nesses of zirconia (0.3, 0.5 and 0.8 mm) was measured using a hand-held radiometer (Demetron, Kerr). Data were analyzed using one-way ANOVA test (alpha=.05). Results: ANOVA revealed that resin cement and light curing unit had significant effects on microhardness (p < 0.001). Additionally, greater zirconia thickness resulted in lower transmittance. There was no correlation between the amount of light transmitted and microhardness of dual-cured resin cements (r = 0.073, p = 0.295). Conclusion: Although different zirconia thicknesses might result in insufficient light transmission, dual-cured resin cements under zirconia restorations could have adequate microhardnes

Biomechanical behavior of cavity configuration on micropush-out test : a finite-element-study

Objective: The objective of this study was to simulate the micropush-out bond strength test from a biomechanical point of view. For this purpose, stress analysis using finite element (FE) method was performed. Study design: Three different occlusal cavity shapes were simulated in disc specimens (model A: 1.5 mm cervical, 2 mm occlusal diameter; model B: 1.5 mm cervical, 1.75 mm occlusal diameter; model C: 1.5 mm cervical, 1.5 mm occlusal diameter). Quarter sizes of 3D FE specimen models of 4.0×4.0×1.25 mm3 were constructed. In order to avoid quantitative differences in the stress value in the models, models were derived from a single mapping mesh pattern that generated 47.182 elements and 66.853 nodes. The materials that were used were resin composite (Filtek Z250, 3M ESPE), bonding agent (Adper Scotchbond Multi-Purpose, 3M ESPE) and dentin as an isotropic material. Loading conditions consisted of subjecting a press of 4 MPa to the top of the resin composite discs. The postprocessing files allowed the calculation of the maximum principal stress, minimum principal stress and displacement within the disc specimens and stresses at the bonding layer. FE model construction and analysis were performed on PC workstation (Precision Work Station 670, Dell Inc.) using FE analysis program (ANSYS 10 Sp, ANSYS Inc.). Results: Compressive stress concentrations were observed equally in the bottom interface edge of dentin. Tensile stresses were observed on the top area of dentin and at the half of lower side of composite under the loading point in all of the FE models. Conclusions: The FE model revealed differences in displacement and stress between different cavity shaped disc specimens. As the slope of the cavity was increased, the maximum displacement, compressive and tensile stresses also increased

Efficacy of different devices in removing calcium hydroxide from the root canal

Objectives: The aim was to compare the efficiency of removing calcium hydroxide (CH) with different devices and irrigants. Materials and Methods: Ten roots were served as positive and negative controls, the remaining roots (n=75) were assigned into 5 respect to the removal techniques: Group (G) I, Master apical file- manual needle irrigation (MNI); GII, Canal Brush (CB)-MNI; GIII, RinsEndo; GIV, Self-adjusting file(SAF)-Vatea; GV, CB+MNI, followed by SAF+Vatea. The roots were grooved longitudinally and split into halves.  Three specimens from each group were randomly selected to evaluate CH remnants under the SEM. A digital camera acquired images of each half of the canal. A scoring system was used to assess amount of residue. Data were analyzed using Kruskal–Wallis and Mann–Whitney U tests (p &lt; 0.05). Results: Remnants of CH were found in all experimental groups. Examining the efficacy of CH removal from the each third of the canal showed that there was a statistically significant difference between the middle (p=0,003) and cervical (p=0,006) thirds. Conclusions: None of the techniques removed the CH medicament completely; the use of the RE and SAF facilitated removal of CH especially from the cervical third

A Discussion of Malware Attacks Targeting Smart Homes and Connected Devices: Investigating Cybersecurity Risks in Everyday Living

Computer technology has advanced with the digital age. Software for several platforms is crucial to streamlining human work with computers. This software is essential for many user tasks, including IoT ones. Through data exploitation and communication technologies, the Internet of entities (IoT) connects physical and virtual entities to the global web. This technology aims to make it easier for humans to interact with objects and let them communicate. In daily life, numerous specialized gadgets use the Internet of Things (IoT), especially Smart Homes. Smart Homes integrate networked communication networks with home devices for remote control, monitoring, and access. The name "Smart" in Smart Homes suggests intelligence, however IoT devices have limitations. Malware is purposely designed to disrupt or gain unauthorized access to computer systems without the system owner's knowledge or agreement. Malware threatens smart home security widely. Malware can also quickly regenerate and adapt as technology advances. It's often integrated into popular online apps. This study examines how malware assaults affect IoT and Smart Home devices. The study's conclusions include an analytical report on IoT and Smart Home malware mitigation in legal perspectives