K Yoshida’s research while affiliated with Nagasaki University and other places

Radiological specialists from Nagasaki University have served on the medical relief team organized at Fukushima Medical University Hospital (Fukushima City) ever since the accident at the Fukushima Dai-ichi nuclear power plant. Furthermore, we have conducted the radiation crisis communication efforts by spreading correct information on the health effects of radiation as 'advisors on radiation health risk control'. Nagasaki University has been assisting the reconstruction efforts of Kawauchi Village in Fukushima Prefecture, which was the first village to declare that residents could safely return to their homes because radiation doses were found to be at comparatively low levels. In April 2013, Nagasaki University and the Kawauchi government office concluded an agreement concerning comprehensive cooperation toward reconstruction of the village. As a result, we established a satellite facility of the university in the village. In conclusion, training of specialists who can take responsibility for long-term risk communication regarding the health effects of radiation as well as crisis communication in the initial phase of the accident is an essential component of all such recovery efforts. Establishment of a training system for such specialists will be very important both for Japan and other countries worldwide.

Objective: The purpose of this study was to evaluate the color stability of the final shade of indirect composites and the effect of luting cements. Methods: Three different indirect composites were prepared in the study (Ceramage/Shofu, Estenia C&B/Kuraray Noritake, Gradia Forte/GC). 2.0-mm thick indirect composites with attaching tape were placed on zirconia (groups without cement, each n=3), or they were luted with dual-cured resin cements (ResiCem/Shofu, Clearfil Esthetic Cement/Kuraray Noritake, G-CEM LinkAce/GC) on zirconia (groups with cement, each n=3). The indirect composites and the dual-cured resin cements were obtained from the same manufacturer. Specimens were stored in dark box at 37ºC for 24 h. Color measurements were performed using a spectrophotometer before and after immersion in deionized water at 37ºC in dark condition for 4 weeks. Change in color (ΔE*, before and after immersion) were obtained using the CIE L*a*b*system. The results were analyzed by one-way ANOVA, and identical letters indicated no significant differences in post-hoc Tukey’s compromise test for each factor (p>0.05). Results: All indirect composites luted with or without dual-cured resin cements showed varying changes in color. The ΔE*s of the groups ranged from 0.26 to 1.13. The highest discoloration was attributed to Ceramage without cement, while the lower discoloration was found in Estenia C&B luted with Clearfil Esthetic Cement. Conclusions: All indirect composites luted with resin cement evaluated were considered clinically acceptable (ΔE*<3.3). Dual-cured resin cements may not affect color stability of 2.0-mm thick indirect composites. Indirect Dual-cured Before immersion in water After immersion in water ΔE* composite resin cement L* a* b* L* a* b* Ceramage without 71.18 (0.12)a 0.83 (0.01)b 18.22 (0.13)e 70.46 (0.32)a 1.24 (0.04)c 17.46 (0.14)c 1.13 (0.32)b with 71.21 (0.09)a 0.91 (0.03)b 17.22 (0.27)b 70.59 (0.11)a 1.26 (0.03)c 16.79 (0.14)b 0.81 (0.19)b Estenia C&B without 71.95 (0.14)c -1.10 (0.04)a 17.86 (0.16)d 71.68 (0.14)c -0.98 (0.05)b 17.72 (0.15)d 0.34 (0.05)a with 71.74 (0.08)b -1.22 (0.02)a 17.60 (0.08)c 71.52 (0.09)c -1.09 (0.03)a 17.55 (0.09)c,d 0.26 (0.08)a Gradia Forte without 72.21 (0.09)d 1.53 (0.24)c 17.25 (0.17)b 71.61 (0.18)c 1.77 (0.21)d 16.91 (0.24)b 0.74 (0.16)b with 72.28 (0.17)d 1.68 (0.07)d 16.58 (0.30)a 71.24 (0.12)b 1.81 (0.03)d 16.29 (0.27)a 1.10 (0.08)b

Objectives: The purpose of this study was to evaluate the Knoop hardness (KHN) and bond strength of self-adhesive resin cement (SA Luting, Kuraray Noritake) polymerized by three light-irradiation protocols. Methods: The three light-irradiation protocols were as follows: irradiation for 4 s; irradiation for 20 s; and irradiation for 4 s, removal of semi-cured excess cement in a 60-s interval, and irradiation for 20 s (24 s of irradiation). A composite resin column was placed on a zirconia surface with a cement-filled circular hole and polymerized by one of the three light-irradiation protocols. KHN of the cement surfaces was recorded 0.5 h and 24 h after irradiation (n = 5). Shear tests were also performed using composite resin columns bonded to the zirconia ceramic with resin cement. Specimens were evaluated at 0.5 h, 24 h, and/or 5,000 thermal cycles after irradiation (n = 10). Data were analyzed by two-way ANOVA, and identical letters indicated no significant differences in post-hoc Tukey's compromise test for each property (p > 0.05). Results: The KHN value at 24 h after irradiation was higher than that at 0.5 h, regardless of the light-irradiation protocol. At both post-irradiation times, KHN values for the 20-s and 24-s light-irradiation protocols were significantly higher than that for the 4-s irradiation. The bond strength of resin cement at 24 h after irradiation was higher than that at 0.5 h after irradiation, regardless of the light-irradiation protocol. However, the bond strength of the resin cement irradiated for 4 s decreased significantly after 5,000 thermal cycles. Conclusions: An initial 4-s irradiation followed by removal of semi-cured excess cement and a second 20-s irradiation yielded better KHN values than that achieved with initial irradiation only. The durable zirconia-bonding strength of dual-cured self-adhesive resin cement polymerized by this light-irradiation protocol is favorable for clinical use. Light-irradiation condition Knoop hardness (KHN) Shear bond strength (MPa) Post-irradiation time Storage condition 0.5 h 24 h 0.5 h 24 h TC 5,000 Irradiation for 4 s (4-s) 15.5 (1.6)a 22.5 (1.3)b 7.0 (2.1)A 14.6 (2.2)C,D 8.3 (1.4)A Irradiation for 20 s (20-s) 21.5 (1.5)b 28.7 (1.6)c 11.3 (2.9)B 12.2 (1.7)B,C 10.9 (1.4)B 24 s of irradiation (24-s) 25.1 (2.2)c 27.7 (1.6)c 9.1 (1.7)A,B 11.4 (1.7)B 10.8 (1.9)B

Objectives: This study evaluated the shear bond strengths of four auto-mixing self-adhesive resin cements {Maxcem Elite (Kerr), SpeedCEM (Ivoclar Vivadent), RelyX Unicem 2 Automix (3M ESPE), and GAM-200 (GC)} between dual-cured resin composite for core build-up (UniFil Core EM, GC) and partially-stabilized zirconia ceramic (GC). Methods: Zirconia disk specimens were sanded with grit #600 Silicon-carbide paper (SiC), treated with phosphoric acid gel (PAG, Kuraray) for 5 s, rinsed, and then air-dried (Control) Other specimens were treated with PAG after air-abrading with 50 µm alumina particles (AB). Composite disk specimens were sanded with #600SiC and then treated with PAG. Zirconia and composite disks were bonded together with each self-adhesive resin cement, and then photo-polymerized with a visible-light-curing unit for 40 s. Specimens were stored in water at 37ºC for 24 hrs and/or performed thermal cycling of 10,000 times before shear bond strength testing. Means and SDs (in parenthesis) of shear bond strength (MPa) are listed in Table. Data were analyzed by three-way ANOVA and identical letters were not significantly different by Tukey-Compromise test (p>0.05, n=7). Results: The bond strengths of four self-adhesive resin cements between resin composite and alumina-blasting zirconia were higher than those of control groups before thermal cycling. After thermal cycling, two of four resin cements to alumina-blasting zirconia showed insignificantly decrease of bond strength. Conclusions: These results suggest that bond durability is different between brands and alumina-blasting is necessary for durable bonding of zirconia to resin composite for core build-up with self-adhesive resin cement. Self-adhesive Zirconia Thermal Cycling Resin Cement Surface Treatment 0 10,000 Maxcem Elite Control 8.6 (1.5)b,c 3.0 (0.7)a AB 17.9 (3.4)e,f 5.5 (0.6)a,b SpeedCEM Control 13.3 (3.8)d,e 6.7 (2.7)a,b AB 22.5 (2.7)f,g 23.3 (2.0)g RelyX Unicem 2 Automix Control 11.9 (2.9)c,d 5.5 (2.0)a,b AB 13.9 (2.8)d,e 7.0 (2.3)a,b GAM-200 Control 21.4 (3.4)f,g 16.2 (2.6)d,e AB 26.2 (2.1)g 24.7 (1.3)g

Objectives: This study assessed the influence of sandblasting with alumina (AB) or silicon carbide (SiC) and application of MDP primer (MDP) and/or silane coupler (SC) on the shear bond strength of self-adhesive resin cement (SA Luting, Kuraray Medical) between zirconia and dual-cured resin composite for core build-up (Clearfil DC Core Automix, Kuraray Medical). Methods: The zirconia specimens (Toso) were divided into six groups with different surface treatments {non-treatment (NT), AB, SiC, SiC/MDP, SiC/SC, and SiC/MDP+SC}. The dual-cured resin composite disk specimens were also prepared using laboratory-curing unit. The zirconia specimens were treated with one of five methods or untreated, bonded to resin composite with dual-cured self-adhesive resin cement, and then photo-polymerized with a visible-light-curing unit. Specimens were stored in water at 37ºC for 24 hrs and/or thermocycled 10,000 times before shear bond strength testing. Means and SDs (in parenthesis) of shear bond strength (MPa) are listed in Table. Data were analyzed by two-way ANOVA and identical letters were not significantly different by Tukey Compromise test (p>0.05, n=7). Results: At thermocycle 0, all treatments, in particular, SiC/MDP and SiC/MDP+SC, were significantly effective for improving shear bond strength of self-adhesive resin cement between zirconia and resin composite compared with NT. However, all treatments except SiC/SC decreased significantly shear bond strength after 10,000 thermal cycling. Conclusion: These results suggest that the treatment of blasting with silicon carbide followed by application of silane coupler appears to be effective for durable bonding of dual-cured self-adhesive resin cement between zirconia and dual-cured resin composite for core build-up. Surface Thermal Cycling Treatment 0 10,000 NT 8.0 (0.9)b 3.6 (0.8)a AB 13.2 (1.1)d,e 8.2 (1.4)b SiC 15.6 (1.0)e 9.5 (1.5)b SiC/MDP 19.3 (1.4)f 10.3 (0.7)b,c SiC/SC 14.5 (1.9)d,e 12.5 (1.2)c,d SiC/MDP+SC 20.0 (2.2)f 12.3 (1.7)c,d

Objectives: This study assessed the influence of alumina-blasting (AB) and adhesive primer (AP) on the shear bond strength of self-adhesive resin cement between zirconia and dual-cured resin composite for core build-up. Methods: The specimens were divided into 18 groups with three dual-cured self-adhesive resin cements {Maxcem Elite (ME, Kerr), RelyX Unicem Clicker (RUC, 3M ESPE) G-Luting (GL, GC)}, three different surface treatments {non-treatment (NT), AB, and AB+AP (Metal Primer II (GC)}, and two thermal cyclings (TC). The dual-cured resin composite (Unifil Core EM, GC) disk specimens were also prepared using laboratory-curing unit. The zirconia (GC) specimens were treated with one of three methods, bonded to resin composite with one of three resin cements, and then photo-polymerized with a visible-light-curing unit. Specimens were stored in water at 37ºC for 24 hrs and/or thermocycled 20,000 times before shear bond strength testing. Means and SDs (in parenthesis) of shear bond strength (MPa) are listed in Table. Data were analyzed by three-way ANOVA and identical letters were not significantly different by Tukey Compromise test (p>0.05, n=7). Results: At TC 0, AB and AB+AP were significantly effective for improving shear bond strength of self-adhesive resin cement between zirconia and resin composite compared with NT. All groups except treatment with AB+AP and bonding with GL, decreased significantly shear bond strength after TC 20,000. Conclusion: These results suggest that the treatment of alumina-blasting followed by application of adhesive primer on the zirconia surface is preferable to obtain durable bonding of dual-cured self-adhesive resin cement between zirconia and resin composite. Self-adhesive Surface Thermal Cycling (TC) Resin Cement Treatment 0 20,000 ME NT 10.0 (0.7)d,e,f 3.7 (1.7)a,b ME AB 17.3 (3.1)h,i 5.3 (1.9)a,b,c ME AB+AP 17.0 (2.0)h,i 6.2 (1.5)b,c,d RUC NT 11.2 (1.9)e,f,g 2.5 (0.9)a,b RUC AB 15.0 (2.9)g,h 8.9 (1.6)c,d,e RUC AB+AP 18.6 (2.8) h,i 11.9 (2.3) e,f,g GL NT 10.5 (1.6)d,e,f,g 1.1 (0.4)a GL AB 20.0 (3.8)i 13.9 (1.0)f,g,h GL AB+AP 21.7 (3.5)i 18.1 (3.6)h,i

Objectives: This study assessed the influence of sandblasting with alumina (AB) or zirconia (ZB) and application of zirconate coupling agent (ZCA) on the shear bond strength of self-adhesive resin cement (Clearfil SA Cement, Kuraray Medical) between zirconia and dual-cured resin composite for core build-up (Clearfil DC Core Automix, Kuraray Medical). Methods: The zirconia specimens (Toso) were divided into five groups with different surface treatments {non-treatment (NT), AB, ZB, AB+ZCA, ZB+ZCA}. The dual-cured resin composite disk specimens were also prepared using laboratory-curing unit. The zirconia specimens were treated with one of four methods or untreated, bonded to resin composite with dual-cured self-adhesive resin cement, and then photo-polymerized with a visible-light-curing unit. Specimens were stored in water at 37ºC for 24 hrs and/or thermocycled 10,000 times before shear bond strength testing. Means and SDs (in parenthesis) of shear bond strength (MPa) are listed in Table. Data were analyzed by three-way ANOVA and identical letters were not significantly different by Tukey-Kramer test (p>0.05, n=7). Results: At thermocycle 0, sandblasting with alumina (AB) or zirconia (ZB) and ZCA (AB+ZCA or ZB+ZCA) were significantly effective for improving shear bond strength of self-adhesive resin cement between zirconia and resin composite compared with NT. All treatments except AB+ZCA decreased significantly shear bond strength after 10,000 thermal cycling. Conclusion: These results suggest that the treatment of blasting with alumina followed by application of zirconate coupling agent appears to be effective for greatly bonding of dual-cured self-adhesive resin cement between zirconia and dual-cured resin composite for core build-up. Surface Thermal Cycling Treatment 0 10,000 NT 8.1 (0.9)b 3.7 (0.7)a AB 13.1 (1.3)e,f 8.3 (1.5)b,c ZB 10.6 (1.2)c,d 3.6 (0.4)a AB+ZCA 11.5 (1.5)d,e 14.2 (1.7)f ZB+ZCA 11.2 (0.7)d,e 3.7 (0.7)a

To improve the physical properties of the pure titanium surface, thin titanium nitride (TiN) films were deposited by means of ion-beam-assisted deposition. Film structure was confirmed as TiN by X-ray diffraction analysis. Surface hardness and abrasion resistance were significantly improved on TiN-coated specimens. Five combinations of oral hygiene instruments and materials were applied to the specimens as simulations of the oral environment. Treatment with the metal scaler and ultrasonic scaler severely changed the surface features and significantly increased the surface roughness parameters on pure titanium controls, whereas only small scratches and dull undulations were seen on the TiN-coated specimens. Profilometric tracings and scanning electron micrographs demonstrated the improved abrasion resistance of the TiN-coated specimens.

The purpose of this study was to evaluate the shear bond strengths of three dual-cured resin luting cements (Linkmax HV, Panavia Fluoro Cement, and RelyX ARC) to glass-infiltrated alumina-reinforced ceramic material and the effect of four silane coupling agents (Clearfil Porcelain Bond, GC Ceramic Primer, Porcelain LinerM, and Tokuso Ceramic Primer) on the bond strength. The two type-shaped of In-Ceram alumina ceramic glass-infiltrated specimens were untreated or treated with one of the four ceramic primers and then cemented together with one of the three dual-cured resin luting cements. Half of the specimens were stored in water at 37 degrees C for 24 h and the other half thermocycled 20,000 times before shear bond strength testing. Surface treatment by all silane coupling agents improved the shear bond strength compared with non-treatment. The specimens treated with Clearfil Porcelain Bond showed significantly greater shear bond strength than any of the other three silane coupling agents regardless of resin luting cements and thermocycling except for the use of Panavia Fluoro Cement at 20,000 thermocycles. When the alumina-reinforced ceramic material was treated with any silane coupling agent except GC Ceramic Primer and cemented with Linkmax HV, no significant differences in bond strength were noted between after water storage and after 20,000 thermocycles. After 20,000 thermocycles, all specimens except for the combined use of Clearfil Porcelain Bond or GC Ceramic Primer and Linkmax HV and GC Ceramic Primer and Panavia Fluoro Cement showed adhesive failures at the ceramic-resin luting cement interface.

The objective of this study was to examine the joint strength of titanium laser-welding using several levels of laser output energy [current (A)]. Cast titanium plates (0.5 x 3.0 x 40 and 1.0 x 3.0 x 40 mm(3)) were prepared and perpendicularly cut at the center of the plate. After the cut halves were fixed in a jig, they were laser-welded using a Nd: YAG laser at several levels of output energy in increments of 30A from 180 to 300A. The penetration depths of laser to titanium were measured under various conditions for output energy, pulse duration, and spot diameter to determine the appropriate conditions for these parameters. Based on the correlation between the results obtained for penetration depth and the size of the specimens (thickness: 0.5 and 1.0 mm, width: 3.0 mm), the pulse duration and spot diameter employed in this study were 10 ms and 1.0 mm, respectively. Three laser pulses (spot diameter: 1.0 mm) were applied from one side to weld the entire joint width (3.0 mm) of the specimens. Uncut specimens served as the non-welded control specimens. Tensile testing was conducted at a crosshead speed of 2 mm/min and a gage length of 10 mm. The breaking force (N) was recorded, and the data (n=5) were statistically analyzed. For the 0.5 mm thick specimens, the breaking force of the specimens laser-welded at currents of 240, 270, and 300A were not statistically (P>0.05) different from the non-welded control specimens. There were no significant differences in breaking force among the 1.0mm thick specimens laser-welded at currents of 270 and 300A, and the non-welded control specimens. Under appropriate conditions, joint strengths similar to the strength of the non-welded parent metal were achieved.