A hybrid-type composite eESTENIA' (Kuraray Medical Inc.) is a crown and veneering material which has a high mechanical strength that can be used for posterior jacket crown without metal support. Recently, we have developed a new composite material (named eES-H') which had a high transparency while having a high mechanical strength equal to ESTENIA. Objectives: The purpose of this study was to evaluate mechanical properties and transparency of ES-H, and to prove possessing a high mechanical strength equal to ESTENIA. Methods: The flexural strength, the compressive strength, and the transparency were measured. The polymerization procedure was optical irradiation for 5 min by alphalightII (J.Morita Corp.) and 110 degrees Celsius heating for 15 min. For the flexural strength, square pillar specimens of 2x2x30mm were made, and an Autograph (Shimadzu Corp., AG-100kNI type) was used at cross head speed 1mm/min by the lower span 20mm. For the compressive strength, a columnar specimens of 4mm (in diameter) and 4mm(in height) were made, and an Autograph (ditto) was used at cross head speed 2mm/min. The transparency was evaluated from the value of edeltaL*(w/b)' (= L*(w)-L*(b)) of the polymerized disk with 1mm thickness using spectrum colorimetry meter "CM-3610d" (Minolta Ltd.) under santdardized light D65/2. eL*(w)' means the value of lightness on a white background, and eL*(b)' on a black background. The greater the value of deltaL*(w/b) is, the higher the transparency of the resin disk is. Results: eES-H' had a high mechanical strength(flexural strength: 190MPa, compressive strength: 595MPa), and a high transparency (deltaL* = 31.6, ESTENIA' deltaL* = 23.8) enough to be used in the most upper layer of the jacket crown. Conclusion: eES-H' was expected to be used in the more esthetic treatment than ESTENIA.

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