A metal frame of a dental product is cast in the mold cavity.

[0002]"Flexural modulus"as used herein refers to results of testing according to ISO-10477 on specimens (2mm by 2mm by 25mm) with a loading rate of 150 N/minute.

[0003]"Flexural toughness"as used herein refers to results of testing according to ASTM D790 (1997), and the test results are analyzed according to the method of ASTM D882 (1997) Appendix A2.

[0004] In order of increasing preference the polymeric material of the invention has a flexural toughness of at least 10; 15; 20; 40; 60; or 90 inch- pound/inch. In order of increasing preference the polymeric material has a flexural modulus of at least 250,000 ; 300,000 ; 350,000 ; 400,000 ; 450,000 ; 500,000 ; 550,000 ; 600,000 ; or 650,000 psi.

[0005] Preferably, the polymeric material of the invention has a flexural toughness of at least 10 inch-pound/inch3 and a flexural modulus of at least 250,000 psi. More preferably, the polymeric material has a flexural toughness of at least 10 inch-pound/inch3 and a flexural modulus of at least 300,000 psi. Most preferably, the polymeric material has a flexural toughness of at least 15 inch-pound/inch3 and a flexural modulus of at least 300,000 psi.

PROCEDURE 1: Preparation of Oligomer [0006] A reactor was charged with 1176 grams of trimethyl-1, 6- diisocyanato-hexane (5.59 mol) and 1064 grams of bisphenol A propoxylate (3.09 mol) under dry nitrogen flow and heated to about 65° C under a positive nitrogen pressure. To this reaction mixture, 10 drops of catalyst dibutyltin dilaurate were added. The temperature of the reaction mixture was maintained between 65°C and 140°C. for about 70 minutes and followed by additional 10 drops of catalyst dibutyltin dilaurate. A viscous paste-like isocyanate end-capped intermediate product was formed and stirred for 100 minutes.

[0007] To this intermediate product, 662 grams (5.09 mol) of 2- hydroxyethyl methacrylate and 7.0 grams of BHT as an inhibitor were added over a period of 70 minutes while the reaction temperature was maintained between 68°C and 90°C. After about five hours stirring under 70°C, the heat was turned off, and oligomer was collected from the reactor as semi- translucent flexible solid and stored in a dry atmosphere.

EXAMPLE 1 [0008] 45 g of the oligomer reaction product of trimethyl-1, 6- diisocyanatohexane, bisphenol A propoxylate and 2-hydroxyethyl methacrylate formed by following the Procedure 1 (TBDMA), 9 g tris (2- Hydroxy ethyl) Isocyanurate triacrylate, 24.664 g 4,13-dioxo-3, 14-dioxa-5, 12- diazahexadecane-1, 16-diol dimethacrylate (HDIDMA), 12 g 4,13-dioxo-3, 14- dioxa-5,12-diazahexadecane-1, 16-diol diacrylate, 0.084 g camphorquinone, 0.252 g ethyl 4-dimethylaminobenzoate, and 9 g sucrose diacetate hexaisobutyrate are melted and then stirred to form a polymerizable burn-out material.

EXAMPLE 1A [0009] 44 g of the oligomer reaction product of trimethyl-1, 6- diisocyanatohexane, bisphenol A propoxylate and 2-hydroxyethyl methacrylate formed by following the Procedure 1 (TBDMA), 14 g tris (2- Hydroxy ethyl) Isocyanurate triacrylate, 33.2 g 4,13-dioxo-3, 14-dioxa-5,12- diazahexadecane-1, 16-diol dimethacrylate (HDIDMA), 8.3 g 4,13-dioxo-3, 14- dioxa-5,12-diazahexadecane-1, 16-diol diacrylate, 0. 12 g camphorquinone, and 0.36 g ethyl 4-dimethylaminobenzoate are melted and then stirred to form a polymerizable burn-out material.

EXAMPLE [0010] 65.5 g of the oligomer reaction product of trimethyl-1, 6- diisocyanatohexane, bisphenol A propoxylate and 2-hydroxyethyl methacrylate formed by following the Procedure 1 (TBDMA), 27 g 4,13-dioxo- 3,14-dioxa-5, 12-diazahexadecane-1, 16-diol dimethacrylate (HDIDMA), 6 g 4,13-dioxo-3, 14-dioxa-5,12-diazahexadecane-1, 16-diol diacrylate, (HDIDA), 0.35g 2,4, 6- trimethylbenzoyldiphenylphosphine oxide made by BASF (Lucirin-TPO) and 1.15 g of a mixture containing 23.02% of MMA (methacrylic acid), 1.3% BHT (butylated hydroxy toluene), 46.05% DMADPA (N, N- dimethylaminoethyl neopentyl acrylate), 16.32 silane (gamma- methacryloxypropyltrimethoxysilane) and 13. 31% camphorquinone (CQ) are melted and then stirred to form a polymerizable burn-out material.

EXAMPLE 2: PARTIAL DENTURE [0011] A cast of a patient's mouth is formed by taking an alginate impression of the patient's mouth and poring plaster into the impression to form a cast. A polymerizable burn-out material made by following the procedure of EXAMPLE 1 is shaped on the cast and light cured for 10 minutes using a Triad 2000 curing light to form a polymeric model of polymeric burn-out material having a shape of a frame of a partial denture.

The polymeric burn-out material has a flexural modulus of 450,000 psi. The cured polymeric model of the frame and the cast are immersed in water at 45°C and 2 bar gauge pressure. The cured polymeric model is removed from the cast and invested in an ethanol slurry of Vitallium 2000 investment material sold by Dentsply International. The ethanol slurry of Vitallium 2000 investment material is a mixture of silica and ethanol in a weight ratio of about 6 to 1. Some of the ethanol separates from the silica and evaporates. The silica forms a shaped refractory material. The polymeric material is burned out of the shaped refractory material to form a mold cavity having the shape of a frame of a partial denture in the refractory material. Molten titanium alloy is poured into the mold cavity and cooled to form a solid metal frame of a partial denture. The refractory material is broken away from the metal frame.

[0012] A partial denture is formed by positioning the metal frame and artificial teeth in a partial denture mold cavity of a mold. The partial denture mold cavity is filled with denture base material to form a partial denture. The mold is then broken away from the partial denture.

[0013] As shown in the following table, the flexural modulus of the cured burn-out material of the invention is superior compared to the flexural modulus of cured commercially available burn-out materials. Also, the combination of the flexural modulus and flexural toughness of the cured burn-out material of the invention is superior compared to the flexural modulus and flexural toughness of cured commercially available burn-out materials. Beneficially, the cured burn-out material of the invention effectively retains its shape during investment, resulting in a superior fit of the frame to the patient, compared to cured commercially available burn-out materials.

TABLE POLYMERIC FLEXURAL FLEXURAL fit of the BURN-OUT MODULUS TOUGHNESS frame to the MATERIAL (psi) (inch-pounds/inch3) patient EXAMPLE 1 532,000 93.3 good EXAMPLE 1A 571,000 104 EXAMPLE 550,000 112 sold by PRIMOTEC 227,000 5.8 marginal sold by MOLTEN 120,000 156.2 poor [0014] Polymeric burn-out material sold by PRIMOTEC has a flexural modulus of 227,000 psi and its use results in a marginally acceptable fit of the frame to the patient. Polymeric burn-out material sold by MOLTEN has a flexural modulus of 120,000 psi and its use results in a poor fit of the frame to the patient.

EXAMPLE 3 : BRIDGE [0015] A cast of a patient's mouth is formed by taking an alginate impression of the patient's mouth and poring plaster into the impression to form a cast. A polymerizable burn-out material made by following the procedure of EXAMPLE 1 is shaped on the cast and light cured for 10 minutes using a Triad 2000 curing light to form a polymeric model of polymeric burn-out material having a shape of a frame of a bridge. The polymeric burn-out material has a flexural modulus of 450,000 psi. The cured polymeric model of the frame and the cast are immersed in water at 45°C and 2 bar gauge pressure. The cured polymeric model is removed from the cast and invested in an aqueous slurry of PH3 phosphate investment material, sold by Dentsply International. The aqueous slurry of PH3 phosphate investment material is a mixture of ammonium phosphate, silica and water in a weight ratio of about 8 to 1. The mixture of ammonium phosphate, silica and water forms a refractory material. The polymeric material is burned out of the refractory material to form a mold cavity having the shape of a frame of a bridge. Molten gold palladium alloy is poured into the mold cavity and cooled to form a solid metal frame of a bridge. The refractory material is broken away from the metal frame. A bridge is formed by positioning artificial teeth on the metal frame.

EXAMPLE 4: CROWN [0016] A cast of a patient's mouth is formed by taking an alginate impression of the patient's mouth and poring plaster into the impression to form a cast. A polymerizable burn-out material made by following the procedure of EXAMPLE 1 is shaped on the cast and light cured for 10 minutes using a Triad 2000 curing light to form a polymeric model of polymeric burn-out material having a shape of a frame of a crown. The polymeric burn-out material has a flexural modulus of 450,000 psi. The cured polymeric model of the frame and the cast are immersed in water at 45°C and 2 bar gauge pressure. The cured polymeric model is removed from the cast and invested in an aqueous slurry of PH3 phosphate investment material, sold by Dentsply International. The aqueous slurry of PH3 phosphate investment material is a mixture of ammonium phosphate, silica and water in a weight ratio of about 8 to 1. The mixture of ammonium phosphate, silica and water forms a refractory material. The polymeric material is burned out of the refractory material to form a mold cavity having the shape of a frame of a crown. Molten gold-palladium alloy is poured into the mold cavity and cooled to form a solid metal frame of a crown. The refractory material is broken away from the metal frame. A crown is made by forming an artificial tooth on the metal frame.

[0017] It should be understood that while the present invention has been described in considerable detail with respect to certain specific embodiments thereof, it should not be considered limited to such embodiments but may be used in other ways without departure from the spirit of the invention and the scope of the appended claims.