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Discoloration of various CAD/CAM blocks after immersion in coffee
Lauvahutanon, Sasipin,Shiozawa, Maho,Takahashi, Hidekazu,Iwasaki, Naohiko,Oki, Meiko,Finger, Werner J.,Arksornnukit, Mansuang The Korean Academy of Conservative Dentistry 2017 Restorative Dentistry & Endodontics Vol.42 No.1
Objectives: This study evaluated color differences (${\Delta}Es$) and translucency parameter changes (${\Delta}TPs$) of various computer-aided design/computer-aided manufacturing (CAD/CAM) blocks after immersion in coffee. Materials and Methods: Eight CAD/CAM blocks and four restorative composite resins were evaluated. The CIE $L^{\ast}a^{\ast}b^{\ast}$ values of 2.0 mm thick disk-shaped specimens were measured using the spectrophotometer on white and black backgrounds (n = 6). The ${\Delta}Es$ and ${\Delta}TPs$ of one day, one week, and one month immersion in coffee or water were calculated. The values of each material were analyzed by two-way ANOVA and Tukey's multiple comparisons (${\alpha}=0.05$). The ${\Delta}Es$ after prophylaxis paste polishing of 1 month coffee immersion specimens, water sorption and solubility were also evaluated. Results: After one month in coffee, ${\Delta}Es$ of CAD/CAM composite resin blocks and restorative composites ranged from 1.6 to 3.7 and from 2.1 to 7.9, respectively, and ${\Delta}TPs$ decreased. The ANOVA of ${\Delta}Es$ and ${\Delta}TPs$ revealed significant differences in two main factors, immersion periods and media, and their interaction except for ${\Delta}Es$ of TEL (Telio CAD, Ivoclar Vivadent). The ${\Delta}Es$ significantly decreased after prophylaxis polishing except GRA (Gradia Block, GC). There was no significant correlation between ${\Delta}Es$ and water sorption or solubility in water. Conclusions: The ${\Delta}Es$ of CAD/CAM blocks after immersion in coffee varied among products and were comparable to those of restorative composite resins. The discoloration of CAD/CAM composite resin blocks could be effectively removed with prophylaxis paste polishing, while that of some restorative composites could not be removed.
Discoloration of various CAD/CAM blocks after immersion in coffee
Sasipin Lauvahutanon,Maho Shiozawa,Hidekazu Takahashi,Naohiko Iwasaki,Meiko Oki,Werner J. Finger,Mansuang Arksornnukit 대한치과보존학회 2017 Restorative Dentistry & Endodontics Vol.42 No.1
Objectives: This study evaluated color differences (ΔEs) and translucency parameter changes (ΔTPs) of various computer-aided design/computer-aided manufacturing (CAD/CAM) blocks after immersion in coffee. Materials and Methods: Eight CAD/CAM blocks and four restorative composite resins were evaluated. The CIE L*a*b* values of 2.0 mm thick disk-shaped specimens were measured using the spectrophotometer on white and black backgrounds (n = 6). The ΔEs and ΔTPs of one day, one week, and one month immersion in coffee or water were calculated. The values of each material were analyzed by two-way ANOVA and Tukey’s multiple comparisons (α = 0.05). The ΔEs after prophylaxis paste polishing of 1 month coffee immersion specimens, water sorption and solubility were also evaluated. Results: After one month in coffee, ΔEs of CAD/CAM composite resin blocks and restorative composites ranged from 1.6 to 3.7 and from 2.1 to 7.9, respectively, and ΔTPs decreased. The ANOVA of ΔEs and ΔTPs revealed significant differences in two main factors, immersion periods and media, and their interaction except for ΔEs of TEL (Telio CAD, Ivoclar Vivadent). The ΔEs significantly decreased after prophylaxis polishing except GRA (Gradia Block, GC). There was no significant correlation between ΔEs and water sorption or solubility in water. Conclusions: The ΔEs of CAD/CAM blocks after immersion in coffee varied among products and were comparable to those of restorative composite resins. The discoloration of CAD/CAM composite resin blocks could be effectively removed with prophylaxis paste polishing, while that of some restorative composites could not be removed.
Ishiguro, Masateru,Kuroda, Daisuke,Hanayama, Hidekazu,Takahashi, Jun,Hasegawa, Sunao,Sarugaku, Yuki,Watanabe, Makoto,Imai, Masataka,Goda, Shuhei,Akitaya, Hiroshi,Takagi, Yuhei,Morihana, Kumiko,Honda, IOP Publishing 2015 ASTROPHYSICAL JOURNAL LETTERS - Vol.798 No.2
<P>We report a new observation of the Jupiter family comet 209P/LINEAR during its 2014 return. The comet is recognized as a dust source of a new meteor shower, the May Camelopardalids. 209P/LINEAR was apparently inactive at a heliocentric distance r(h) = 1.6AU and showed weak activity at r(h) <= 1.4AU. We found an active region of <0.001% of the entire nuclear surface during the comet's dormant phase. An edge-on image suggests that particles up to 1 cm in size (with an uncertainty of factor 3-5) were ejected following a differential power-law size distribution with index q = -3.25 +/- 0.10. We derived a mass-loss rate of 2-10 kg s(-1) during the active phase and a total mass of approximate to 5 x 10(7) kg during the 2014 return. The ejection terminal velocity of millimeter- to centimeter-sized particles was 1-4ms(-1), which is comparable to the escape velocity from the nucleus (1.4ms(-1)). These results imply that such large meteoric particles marginally escaped from the highly dormant comet nucleus via the gas drag force only within a few months of the perihelion passage.</P>
MONITORING OBSERVATIONS OF THE JUPITER-FAMILY COMET 17P/HOLMES DURING ITS 2014 PERIHELION PASSAGE
Kwon, Yuna Grace,Ishiguro, Masateru,Hanayama, Hidekazu,Kuroda, Daisuke,Honda, Satoshi,Takahashi, Jun,Kim, Yoonyoung,Lee, Myung Gyoon,Choi, Young-Jun,Kim, Myung-Jin,Vaubaillon, Jeremie J.,Miyaji, Takes American Astronomical Society 2016 The Astrophysical journal Vol.818 No.1
<P>We performed a monitoring observation of a Jupiter-family comet, 17P/Holmes, during its 2014 perihelion passage to investigate its secular change in activity. The comet has drawn the attention of astronomers since its historic outburst in 2007, and this occasion was its first perihelion passage since then. We analyzed the obtained data using an aperture photometry package and derived the Af rho parameter, a proxy for the dust-production rate. We found that Af rho showed asymmetric properties with respect to the perihelion passage: it increased moderately from 100 cm at the heliocentric distance of r(h) = 2.6-3.1 AU to a maximal value of 185 cm at r(h) = 2.2 AU (near the perihelion) during the inbound orbit, while dropping rapidly to 35 cm at r(h) = 3.2 AU during the outbound orbit. We applied a model for characterizing dust-production rates as a function of r(h) and found that the fractional active area of the cometary nucleus had dropped from 20%-40% in 2008-2011 (around the aphelion) to 0.1%-0.3% in 2014-2015 (around the perihelion). This result suggests that a dust mantle would have developed rapidly in only one orbital revolution around the Sun. Although a minor eruption was observed on UT 2015 January 26 at r(h) = 3.0 AU, the areas excavated by the 2007 outburst would be covered with a layer of dust (less than or similar to 10 cm depth) which would be enough to insulate the subsurface ice and to keep the nucleus in a state of low activity.</P>
KISO/KWFC Observation of the Dust Ejecta Associated with the 2007 Outburst of 17P/Holmes
Masateru Ishiguro,Yuki Sarugaku,Daisuke Kuroda,Hidekazu Hanayama,Yoonyoung Kim,Yuna Kwon,Hiroyuki Maehara,Jun Takahashi,Tsuyoshi Terai,Fumihiko Usui,Jeremie J.Vaubaillon,Tomoki Morokuma,Naoto Kobayash 한국천문학회 2015 天文學會報 Vol.40 No.2