Ja-Uk Gu

NDE of the Internal Hole Defect of Dental Composite Restoration Using Infrared Lock-In Thermography

The purpose of this study was to detect the pin hole defect of dental composite restoration using lock-in thermography method. Amplitude and phase images of the composite resin specimens were analyzed according to the lock-in frequency and the diameter of defect area. Through the amplitude image analysis, at lock-in frequency of 0.05 Hz, defect diameters 2-5 mm exhibited the highest amplitude contrast value between defective area and sound area. The lock-in frequency range of 0.3-0.5 Hz provided good phase angle contrast for the defect area. At lock-in frequency range of 0.5 Hz, defect diameter of 5 mm exhibited the highest phase contrast value. It is concluded that the infrared lock-in thermography method verified the effectiveness for detecting the pin hole defect of dental composite restoration.

A NOVEL HEMISPHERICAL MICROBOND SPECIMEN FOR EVALUATING THE INTERFACIAL SHEAR STRENGTH OF A SINGLE FIBER COMPOSITE

In this paper, a novel hemispherical microbond specimen is proposed for evaluating the interfacial shear strength of fiber-reinforced composites. A hemispherical microbond specimen was developed with the insertion of a pin-holed, Teflon film into a droplet matrix surrounding a single fiber. This experimental test offered more reliable strength data in the hemispherical specimen. Thus, the hemispherical microbond specimen is recommended to be suitable for evaluation of interfacial shear strength as a convenient alternative for the cylindrical pull-out test.