Purpose : Recently, adhesive resin cements are widely used in clinical practice. However, their color stability significantly affects esthetics outcomes for metal-free restoration. This study aimed to evaluate the color changes of four adhesive resin cements after immersion for 1 week and 4 weeks in purified water and black tea using a chroma meter.

  Methods : Four adhesive resin cements were used : a self-adhesive resin composite type resin cement : SA Luting Multi (SA, Kuraray Noritake Dental) ; two traditional resin composite type resin cements : PANAVIA V5 (PV, Kuraray Noritake Dental) and Calibra Ceram (CC, Dentsply Sirona) ; and a 4-META/MMA-TBB resin cement : Super-Bond (SB, Sun Medical). Each cement was filled into a ⌀15×3 mm mold and was polymerized. The disc-shaped cement specimens were polished with silicon-carbide paper up to #2000 grit. Then, the baseline color data was measured by a chroma meter. Half of the specimens were immersed in purified water (W), and the other half of the specimens were immersed in black tea (T). The color of each specimen was measured at 1 week (1 w) and 4 weeks (4 w) after immersion. The ΔE*ab data was calculated and analyzed statistically by 2-way ANOVA, Tukey’s q-test, and paired t-test.

  Results : Focusing on the immersion period, significant differences were observed between 1 w and 4 w values in SA, CC, and SB in the W group. On the other hand, all systems indicated a significant difference in the T group. In terms of the effect of adhesive resin cement, significant differences were indicated between SB and other cements, CC-SA and -PV for the 1 w value in the W group. For the 4 w value in the W group, significant differences were indicated between SB and other cements. On the other hand, in the T group, significant differences were indicated between SB and other cements at 1 w. At 4 w in the T group, significant differences were indicated between SA-CC and -SB.

  Conclusion : It was considered that the color change of adhesive resin cement was influenced by the absorption of solution used for immersion, filler content and employed monomers of each adhesive resin cement, and types of solutions for immersion.

  Purpose : This study was performed to assess the current state of tooth bleaching practices by examining the interest and approaches of dentists and dental hygienists at Showa University Dental Hospital. Given the increasing demand for tooth bleaching, the growing patient base, and the recent approval and release of new bleaching materials, the study sought to provide insights to inform future education and training efforts. The findings may also aid in enhancing the operations of the hospital’s whitening outpatient clinic, as well as in advancing the knowledge and skills of dentists and dental hygienists.

  Materials and Methods : A questionnaire survey was administered to 120 dentists and 32 dental hygienists affiliated with Showa University Dental Hospital. The questionnaire included the following questions : Q1. Have you ever been consulted by a patient about the color of his/her teeth? Q2. Have you ever referred a patient to an outpatient tooth-bleaching clinic? Q3. Have you ever recommended tooth bleaching to a patient? Q4. Have you ever performed tooth bleaching? Q5. Are you familiar with the materials used for tooth bleaching and their costs? Q6. What qualifications do you hold as a tooth-bleaching coordinator with the Japanese Academy of Esthetic Dentistry (JAED)? Q7. Have you attended any workshops or seminars on tooth bleaching? Q8. How would you rate your knowledge and skill level regarding tooth bleaching? Q9. Would you be interested in attending future tooth-bleaching seminars at the hospital? Q10. What would you like to see from other professionals involved in clinical tooth-bleaching practices?

  Results : Approximately 80％ of respondents reported having been consulted by patients about the color of their teeth (Q1), and approximately 45％ had recommended tooth bleaching to a patient (Q3). Only a few respondents indicated that they possessed substantial skills and knowledge related to tooth bleaching (Q8). A large number expressed interest in attending future tooth-bleaching seminars (Q9).

  Discussion and Conclusion : The findings highlight the current levels of interest and commitment to tooth bleaching among dentists and dental hygienists at Showa University Dental Hospital. The study also reveals a strong willingness among dental professionals to expand their knowledge and skills in tooth bleaching, suggesting potential areas for targeted educational initiatives.

  Purpose : This study evaluated the impact of ultra-highly translucent zirconia thickness on the final prosthetic color, specifically examining variations in transparency and abutment tooth color.

  Methods : Ultra-highly translucent zirconia disks (Shofu Disk ZR Lucent Ultra, Shofu) in two shades (A2, W3) were used. Dental CAD-CAM equipment was employed to fabricate samples of approximately 11 mm×11 mm in width and length, and thicknesses of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm (±0.01 mm) (n＝12 per thickness). The transparency of the specimens was measured with a spectrophotometer, and transparency parameter (TP) was analyzed in terms of thickness differences. To assess the influence of background color, two types of resin plates simulating healthy dentin (ND3) and discolored dentin (ND9) were used. Color measurements for L*, a*, and b* were obtained using a spectrophotometer, with the color difference (ΔE₀₀) calculated against a 3.0 mm-thick zirconia reference. TP and ΔE₀₀ were statistically analyzed using one-way ANOVA followed by the Tukey-Kramer HSD multiple comparison test, with the significance level set at 5％ (JMP Pro 17.0.0, SAS).

  Results : Regarding the transparency for different thicknesses, TP values ranged from 8.1 to 24.7 for A2 and 7.6 to 25.2 for W3, showing a reduction in TP with increasing thickness in both shades. Statistically significant differences were observed at each thickness level. Regarding ND3 abutment tooth color, ΔE₀₀ values ranged from 3.74 to 5.01, with no significant changes in ΔE₀₀ for different zirconia thicknesses. However, for ND9, ΔE₀₀ values ranged from 6.86 to 10.63, with a trend toward decreased ΔE₀₀ as zirconia thickness increased. Significant thickness-dependent differences were observed within the same abutment color group (p＜0.05).

  Conclusion : The transparency of ultra-highly translucent zirconia was influenced by its thickness. Additionally, the final color of the zirconia was affected by the color of the abutment tooth. In cases with significantly discolored teeth or metal abutment structures, it is suggested that thinner zirconia may more readily allow the underlying abutment color to impact the overall appearance.