Dental investing material

• US 5,820,662 A
• Filed: 07/23/1997
• Issued: 10/13/1998
• Est. Priority Date: 03/31/1997
• Status: Expired due to Fees

• Current Assignee: Taisei Dental Mfg. Co., Ltd.
• Original Assignee: Taisei Dental Mfg. Co., Ltd.
• Inventors: Johshin, Kazuhiko, Kubo, Fuminobu
• Primary Examiner(s): GREEN, ANTHONY J
• Application Number:
  US08/899,046
• Time in Patent Office: 447 Days
• Field of Search: 106/35, 106/38.3, 106/38.2, 106/38.9, 106/692, 106/802, 501/4
• US Class Current: 106/35
• CPC Class Codes: B22C 1/00 Compositions of refractory mould or core materials; Grain structures thereof refractory materials in general C04B35/00; Chemical or physical features in the formation or manufacture of moulds
• CPC Class Codes: B22C 1/02 characterised by additives for special purposes, e.g. indicators, breakdown additives

Abstract

A dental investing material is disclosed which comprises a combination of: (a) quartz and/or cristobalite, (b) a phosphate binder, and (c) aluminous cement, wherein said dental investing material is further added with tridymite and magnesium silicate. The disclosed dental investing material shows minimized expansion during hardening, significant expansion during heating and develops no cracks when heated at a conventional heating rate.

Claims

1. A dental investing material consisting essentially of:

space="preserve" listing-type="tabular">______________________________________ tridymite 5-20 wt. % magnesium silicate 2-20 wt. % aluminous cement 0.05-3 wt. % primary ammonium phosphate 2-8 wt. % magnesium oxide 2-8 wt. % quartz or cristobalite or both the balance. ______________________________________

2. The dental investing material according to claim 1, wherein not less than 60 wt. % of either quartz or cristobalite is contained.

3. The dental investing material according to claim 2, wherein not less than 70 wt. % of either quartz or cristobalite is contained.

4. The dental investing material according to claim 1, wherein not less than 10 wt. % of each of quartz and cristobalite are contained in combination and wherein the combined amount of quartz and cristobalite is not less than 60 wt. %.

5. The dental investing material according to claim 4, wherein said combined amount of quartz and cristobalite is not less than 70 wt. %.