Blueshot

The specimens were fabricated in vinyl chloride transparent tubes. The diameter of the tube was 5.0 mm externally and 3.0 mm internally. The length of the transparent tubes was adjusted to 18 mm. The tubes were embedded in an acrylic bar, and the bar was held in the gauge. An auto-mixed composite resin was injected to fill the tubes, and the posts and sleeves were inserted. Subsequently, the specimens were irradiated on the cross-sectional surfaces and all four sides of the acrylic bar using a light-curing unit (Blueshot, Shofu, Kyoto, Japan) with an intensity of 650 mW/cm 2 for 20 s. Prior to the curing process, the light intensity was measured thrice using a spectroradiometer (Jetlight Light Tester, J.Morita USA, CA, USA) to determine the out-put light power.
Twenty-four hours after curing, the tubes were incised, and the specimens were ejected. The length of the specimens was adjusted to 15 mm using a model trimmer (MODEL TRIMMER Y-230, YOSHIDA Trade Dental Distribution, Tokyo, Japan).

First, 40% phosphoric acid (K-Etchant GEL, Kuraray Noritake Dental, Tokyo, Japan) was applied to the FRC post (1.6 mm diameter, fiber post, GC, Tokyo, Japan), which was then washed with water and dried. Subsequently, a silane coupling agent (CERAMIC PRIMER II, GC) was used. A bonding agent (Clearfil ® Universal Bond, Kuraray Noritake Dental) was applied inside the root canal, and after 10 s of mild air blowing, the root canal was irradiated with an LED light-curing unit (Blueshot, SHOFU) for 10 s. Subsequently, the abutment was built up via the direct method using the FRC post and resin composite for abutment and core (Clearfil ® DC Core Automix ® ONE, Kuraray Noritake Dental). The height of the buildup from the margin was set to 3 mm. Light irradiation with an LED lightcuring unit was performed on the occlusal surface and mesiodistal and buccolingual sides for 40 s each. Finally, a diamond point creates a deep chamfer around the abutment with an axial inclination of 6°, using a surveyor for partial denture.