PHYSICOCHEMICAL CHANGE OF TOOTH STRUCTURE AND CLINICAL PROBLEMS IN DENTAL ESTHETIC BLEACHING

2004 Fiscal Year Final Research Report Summary

• Project/Area Number: 15592014
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Conservative dentistry
• Research Institution: Hokkaido University
• Principal Investigator: TANAKA Toru OKKAIDO UNTV., GRADUATE SCHOOL OF DENTAL MEDICINE, INSTRUCTOR, 大学院・歯学研究科, 助手 (90179771)
• Co-Investigator(Kenkyū-buntansha): IKEDA Takatsumi OKKAIDO UNTV., GRADUATE SCHOOL OF DENTAL MEDICINE, INSTRUCTOR, 大学院・歯学研究科, 助手 (90222885) ; KAWAKAMI Susumu OKKAIDO UNTV., HOKKAIDO UNIVERSITY HOSPITAL, LECTURER, 病院・講師 (20125305)
• Project Period (FY): 2003 – 2004
• Keywords: BLEACHING / TITANIUM DIOXIDE / SODIUM PEROXIDE / MICRO-SHEAR BOND STRENGTH / DYE PENETRATION

Research Abstract

Enamel or dentin was bleached by the bleaching agent containing 6% sodium peroxide and titanium dioxide that is visible-light-responsive photocatalyst.
Immediately or 1 day after bleaching the adhesive system (Clearfil MEGA Bond) was applied and a cylinder(φ0.79mm, height 1mm) of composite resin (Clearfil AP-X, A3) was bonded on each surface. After 30 days the micro-shear bond strength test was performed in a universal-testing machine (EZ test). Specimens without bleaching procedure were prepared as controls.
Immediately or 1 day after bleaching the same adhesive system was applied and cylinder (φ3.18mm, height 3mm) of the same composite resin was bonded on each surface. These specimens were immersed in 0.5% basic fuchsine. The marginal leakage test was performed in a dye penetration. Specimens without bleaching procedure were prepared as controls.
The results were followed :
1.The enamel micro-shear bond strengths were 48.38±13.93MPa(control),54.72±15.21MPa(1day after bleaching) and 37.55±12.92MPa (immediately after bleaching), and retuned after 1 day of storage after bleaching.
2.The dentin micro-shear bond strengths were 44.16±13.13MPa (control),44.16±9.55MPa (1day after bleaching) and 35.71±12.21MPa (immediately after bleaching), and retuned after 1 day of storage after bleaching.
3.The marginal leakage test showed the frequency of dye penetration increased in the order of immediately after bleaching, 1day after bleaching and control. This order was clear in enamel surface.
4.1 day of storage after bleaching might not decrease the dye penetration.
5.Marginal troubles of restorations cause many clinical problems, so the result of marginal leakage test is important for clinic.