(12) United States Patent (10) Patent No.: US 6,187,701 B1 Sekino Et Al
USOO61877O1B1 (12) United States Patent (10) Patent No.: US 6,187,701 B1 Sekino et al. (45) Date of Patent: Feb. 13, 2001 (54) DENTAL PORCELAIN 5,304,516 4/1994 Clifford .................................. 501/66 5,614,330 3/1997 Panzera et al. ........................ 501/21 (75) Inventors: Masato Sekino, Tsukuba; Hiroyuki Nakagawa, Shimotsuma; Osamu * cited by examiner Iwamoto, Tsukuba; Masaaki Ushioda, Shimodate, all of (JP) Primary Examiner-C. Melissa Koslow (73) Assignee: Tokuyama Corporation, (74) Attorney, Agent, or Firm Wenderoth, Lind & Ponack, Yamaguchi-ken (JP) LLP. (*) Notice: Under 35 U.S.C. 154(b), the term of this (57) ABSTRACT patent shall be extended for 0 days. Provided is a porcelain which is Suitable as a dental porce lain capable of being fired on a ceramics core and has a low (21) Appl. No.: 09/321,551 firing temperature and a low thermal expansion coefficient and which is excellent in a chemical durability. The above (22) Filed: May 28, 1999 dental porcelain comprises glass containing Silicon oxide, (30) Foreign Application Priority Data aluminum oxide, boron oxide, Zinc oxide, Sodium oxide and lithium oxide as principal components. The contents of these May 29, 1998 (JP) ................................................. 10-1494O2 respective components in the above glass are 57 to 65% by (51) Int. Cl. ............................. C03B 8/04; CO3B 3/093; weight of SiO, 8 to 18% by weight of Al-O, 15 to 25% by A61C 13/083 weight of BO, 0.1 to 2% by weight of ZnO, 3 to 7% by (52) U.S. Cl. ................................. 501/67; 501/17; 501/21; weight of NaO and 2 to 8% by weight of LiO respectively 501/66; 501/68; 501/69; 106/35 in terms of a percent by weight based on the total of the (58) Field of Search .................................
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