US20120207645A1

US20120207645A1 - Dental alloy for machining by cad/cam system

Info

Publication number: US20120207645A1
Application number: US13/501,176
Authority: US
Inventors: Kyeong-Jun Park; Jeong-Jong Park; Sun-Wook Cho
Original assignee: Ceragem Biosys Co Ltd
Current assignee: Ceragem Biosys Co Ltd
Priority date: 2009-10-14
Filing date: 2010-03-31
Publication date: 2012-08-16
Also published as: KR100979170B1; WO2011046274A1

Abstract

The present invention relates to a dental alloy for machining by a CAD/CAM system. In particular, the dental alloy for machining by a CAD/CAM system features a minimum usage of expensive gold and platinum by comprising gold (Au) in an amount of between 0.1% and 5.0% by weight and platinum (Pt) in an amount of between 0% and 5.0% by weight, in addition to palladium (Pd) in an amount of between 30% and 50% by weight, indium (In) in an amount of between 25% and 50% by weight, silver (Ag) in an amount of between 10% and 40% by weight and iridium (Ir) in an amount of between 0.1% and 0.3% by weight. Accordingly, compared with a conventional dental casting alloy composed of gold in an amount of between 40% and 99% the dental alloy for machining by a CAD/CAM system of the invention can be provided at a lower manufacturing cost, while offering processability equivalent to that of zirconia that can be machined by a conventional CAD/CAM system.

Description

TECHNICAL FIELD

The present invention relates to a dental alloy, and more particularly to a dental alloy for machining by a CAD/CAM system, which is advantageous because of lower manufacturing cost and superior machinability, unlike conventional dental alloys for casting.

BACKGROUND ART

Dental alloys used in the field of dental prosthetics may be classified as precious metal alloys and non-precious metal alloys, depending on the components thereof, and may also be classified as alloys for casting and for metal-ceramics depending on the end uses thereof. Among these, precious metal alloys composed mainly of gold are chemically stable in terms of corrosion resistance, discoloration resistance, etc., in the mouth, and have high cast compatibility. Furthermore, such alloys have color and gloss that only gold has, and do not cause wear of antagonist tooth, but are unfavorably expensive because of the use of gold and platinum group elements as main components.
On the other hand, non-precious metal alloys are widely utilized in devices or tools, and of these, Co—Cr and Ni—Cr alloys for casting have been used as frameworks for partial dentures for a long time, and are being employed in metal-ceramic restorations instead of gold alloys.
Specifically, materials that are the most commonly used to restore a lost tooth in the field of dental prosthetics include dental precious metal alloys composed mainly of gold (Au), platinum (Pt), palladium (Pd), and dental non-precious metal alloys composed mainly of Co—Cr, Ni—Cr, and these play a role in recovering the functions of damaged or lost teeth and imparting patients with esthetic effects and functional efficacy of natural teeth. Hence, the dental alloys are essential in the field of dental prosthetics which functions to replace missing teeth, and may be applied to manufacturing crowns, bridges, removable prostheses and are useful as a material for manufacturing metal coping upon formation of metal-ceramic prostheses that maximize esthetic effects.
However, the price of raw materials for dental alloys, in particular, the price of gold, has been reaching new records in the world market day after day since 2005. Thus, because the price of dental precious metal alloys increases in proportion to an increase in the price of raw materials, economic burdens may be increasingly imposed on practitioners and patients. Accordingly, there is a need to develop dental alloy materials that are more profitable.
Also, a dental prosthesis is generally manufactured using typical precise casting through manual work in dental labs, but this work is disadvantageous in terms of complicated processes and high personnel expenses. Furthermore, casting defects may occur, and casting shrinkage may be caused because of disharmony with materials for wax patterns and casting molds, such as wax, investments. Moreover, because manual work is generally conducted, the degree of perfection of restorations may greatly vary depending on the skill of workers. Particularly in the case of manufacturing implant suprastructures, the size of restorations is comparatively larger than on natural teeth, and thus the cast product may be thick and a large amount of metal may be consumed. Thus, in the course of uniformly melting a large amount of metal, the metal may be easily overheated, and defects such as small holes that cause discoloration and corrosion on the thick portion or surface of the cast product may be generated, undesirably hindering the formation of uniform cast products.
To solve such problems, a CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) system which is of automated machining type has been recently introduced in the manufacturing of dental restorations. Because the CAD/CAM system performs automated machining, a prosthesis manufacturing process is simpler compared to when using a conventional casting process, thus reducing the manufacturing time and the personnel expenses thanks to automation.
A conventional material used in machining by the CAD/CAM system having the above advantages exemplarily includes a ceramic material such as zirconia. In domestic circumstances, it is partially used to manufacture all ceramic restorations using zirconia coping. In the USA or Europe, the formation of restorations using CAD/CAM is gradually increasing compared to using conventional casting.
However, in the case of a ceramic material such as zirconia, it may be broken due to brittleness during machining. Also, because this material is processed in a semi-sintered state and then completely sintered to manufacture a dental prosthesis, compatibility may undesirably decrease attributable to shrinkage of the material. Furthermore, this material is hard to be applied to long span bridges because of sintering shrinkage and inapplicability of post-soldering.
Although the ceramic material such as zirconia has been used when machining with a CAD/CAM system as mentioned above, it is not utilized as a dental alloy material. This is because, in order for dental alloys to be used in machining by a CAD/CAM system, the alloy materials should be inexpensive and should have high processability while the properties of conventional alloys for casting, such as biocompatibility, corrosion resistance, discoloration resistance, etc., which are necessary for dental alloys, are maintained unchanged, but alloy materials suitable for use therein have not yet been developed.

DISCLOSURE

Technical Problem

Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and an object of the present invention is to provide a dental alloy for machining by a CAD/CAM system, wherein the manufacturing cost may be decreased compared to conventional dental alloys, and the manufacturing process may be simplified compared to a casting process that is a conventional alloy manufacturing process, and it is possible to manufacture prostheses having a precise shape, while maintaining the properties of conventional dental alloys such as corrosion resistance, discoloration resistance, biocompatibility, etc., which are necessary for dental purposes.

Technical Solution

In order to accomplish the above object, the present invention provides a dental alloy for machining by a CAD/CAM system, comprising 0.1-5.0 wt % of gold (Au), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), and 0.1-0.3 wt % of iridium (Ir).
In addition, the present invention provides a dental alloy for machining by a CAD/CAM system, comprising 0.1-5.0 wt % of gold (Au), 0.1-5.0 wt % of platinum (Pt), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), and 0.1-0.3 wt % of iridium (Ir).
In addition, the present invention provides a dental alloy for machining by a CAD/CAM system, comprising 0.1-5.0 wt % of gold (Au), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), 0.1-0.3 wt % of iridium (Ir), and 0.01-2.5 wt % of zinc (Zn).
In addition, the present invention provides a dental alloy for machining by a CAD/CAM system, comprising 0.1-5.0 wt % of gold (Au), 0.1-5.0 wt % of platinum (Pt), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), 0.1-0.3 wt % of iridium (Ir), and 0.01-2.5 wt % of zinc (Zn).
In addition, the present invention provides a dental alloy for machining by a CAD/CAM system, comprising 0.1-5.0 wt % of gold (Au), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), 0.1-0.3 wt % of iridium (Ir), and 0.1-1.0 wt % of cobalt (Co).
In addition, the present invention provides a dental alloy for machining by a CAD/CAM system, comprising 0.1-5.0 wt % of gold (Au), 0.1-5.0 wt % of platinum (Pt), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), 0.1-0.3 wt % of iridium (Ir), and 0.1-1.0 wt % of cobalt (Co).
In addition, the present invention provides a dental alloy for machining by a CAD/CAM system, comprising 0.1-5.0 wt % of gold (Au), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), 0.1-0.3 wt % of iridium (Ir), 0.1-1.0 wt % of cobalt (Co), and 0.01-2.5 wt % of zinc (Zn).
In addition, the present invention provides a dental alloy for machining by a CAD/CAM system, comprising 0.1-5.0 wt % of gold (Au), 0.1-5.0 wt % of platinum (Pt), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), 0.1-0.3 wt % of iridium (Ir), 0.1-1.0 wt % of cobalt (Co), and 0.01-2.5 wt % of zinc (Zn).

Advantageous Effects

According to the present invention, a dental alloy comprises 0.1-5.0 wt % of gold, compared to a conventional dental alloy for casting comprising 40-99 wt % of gold. Thus, the dental alloy according to the present invention can be manufactured at a lower cost because of a difference in gold content compared to the conventional alloy for casting. Also, a dental alloy for machining by a CAD/CAM system, having equivalent processibility to that of zirconia that can be machined by a conventional CAD/CAM system, can be effectively provided.

DESCRIPTION OF DRAWINGS

FIG. 1( a) is an SEM (Scanning Electron Microscope) image showing the vertical cut surface of a prosthesis manufactured by a casting process using a conventional dental alloy;

FIG. 1( b) is an SEM image showing the vertical cut surface of a prosthesis manufactured by CAD/CAM machining using a dental alloy for machining by a CAD/CAM system according to the present invention;

FIG. 2( c) is a metal microscope image showing the vertical cut surface of the prosthesis manufactured by a casting process using a conventional dental alloy; and

FIG. 2( d) is a metal microscope image showing the vertical cut surface of the prosthesis manufactured by CAD/CAM machining using a dental alloy for machining by a CAD/CAM system according to the present invention.

MODE FOR INVENTION

Hereinafter, embodiments of the present invention will be described in detail while referring to the accompanying drawings. As such, the terms or words used in the specification and claims shall not be construed as being limiting to meanings generally used or defined in dictionaries, and shall be understood as having meanings and concepts adapted for the technical spirit of the present invention on the assumption that inventors may appropriately define the concepts of terms in order to more efficiently explain the invention.
Thus, the embodiments of the present invention and the constructions depicted in the drawings are merely illustrative, but do not represent all of the technical aspects of the present invention, and it will be appreciated that the present invention includes a variety of equivalents and modifications at the point in time of filing it.
Below is a description of a dental alloy for machining by a CAD/CAM system according to embodiments of the present invention.
According to a first embodiment of the present invention, a dental alloy for machining by a CAD/CAM system may comprise 0.1-5.0 wt % of gold (Au), 0-5.0 wt % of platinum (Pt), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), and 0.1-0.3 wt % of iridium (Ir), and may be used to manufacture a variety of fixed restorations and implant suprastructures.
According to a second embodiment of the present invention, a dental alloy for machining by a CAD/CAM system may comprise 0.1-5.0 wt % of gold (Au), 0-5.0 wt % of platinum (Pt), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), 0.1-0.3 wt % of iridium (Ir), and 0.01-2.5 wt % of zinc (Zn), and may be used to manufacture a variety of fixed restorations and implant suprastructures.
According to a third embodiment of the present invention, a dental alloy for machining by a CAD/CAM system may comprise 0.1-5.0 wt % of gold (Au), 0-5.0 wt % of platinum (Pt), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), 0.1-0.3 wt % of iridium (Ir), and 0.1-1.0 wt % of cobalt (Co), and may be used to manufacture a variety of fixed restorations and implant suprastructures.
According to a fourth embodiment of the present invention, a dental alloy for machining by a CAD/CAM system may comprise 0.1-5.0 wt % of gold (Au), 0-5.0 wt % of platinum (Pt), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), 0.1-0.3 wt % of iridium (Ir), 0.1-1.0 wt % of cobalt (Co) and 0.01-2.5 wt % of zinc (Zn), and may be used to manufacture a variety of fixed restorations and implant suprastructures.
In addition, the dental alloy for machining by a CAD/CAM system according to the present invention is designed to have a composition adapted for CAD/CAM processing while satisfying fundamental properties of a conventional dental alloy, such as biocompatibility, corrosion resistance, discoloration resistance, etc.
Specifically, the composition of the dental alloy for machining by a CAD/CAM system according to the first embodiment of the present invention is configured such that p alladium-indium-silver which are metals already used in conventional alloys for casting are provided as main components, the amounts of gold and platinum are minimized, and a small amount of iridium is added, wherein the ratio of palladium and indium is maintained to keep a yellow gold color, and the amount of silver may be set in the range of 0-40 wt %. Using an alloy having no silver as a control, the alloys are designed depending on the amount of silver. The alloy compositions are shown in Table 1 below.
The composition of the dental alloy for machining by a CAD/CAM system according to the second embodiment of the present invention is configured such that palladium-indium-silver which are metals already used in conventional alloys for casting are provided as main components, the amounts of gold and platinum are minimized, and small amounts of zinc and iridium are added, wherein the ratio of palladium and indium is maintained to keep a yellow gold color, and the amounts of silver and zinc may be set in the range of 0-40 wt % and 0.2-2 wt %, respectively. Using an alloy having no silver as a control, the alloys are designed depending on the amounts of silver and zinc. The alloy compositions are shown in Table 2 below.

TABLE 1

<Alloy Composition of 1^stEmbodiment>

Element (wt %)

	Au	Pt	Pd	In	Ag	Ir

No. 1	1.00	1.00	48.90	48.90	—	0.20
No. 2	1.00	1.00	38.90	38.90	20.00	0.20
No. 3	1.00	1.00	34.57	33.23	30.00	0.20
No. 4	1.00	1.00	36.59	31.21	30.00	0.20
No. 5	1.00	1.00	36.62	35.18	26.00	0.20
No. 6	1.00	1.00	38.77	33.03	26.00	0.20
No. 7	1.00	1.00	40.12	34.18	23.50	0.20
No. 8	1.00	1.00	39.27	33.53	25.00	0.20
No. 9	1.00	1.00	36.34	30.96	30.50	0.20
No. 10	1.00	1.00	43.47	37.33	17.00	0.20
No. 11	2.00	—	41.36	35.44	21.00	0.20
No. 12	3.00	—	35.10	32.70	29.00	0.20
No. 13	3.00	—	35.70	31.10	30.00	0.20
No. 14	3.00	—	36.77	27.03	33.00	0.20
No. 15	3.00	—	35.03	25.77	36.00	0.20

TABLE 2

<Alloy Composition of 2^ndEmbodiment>

Element (wt %)

	Au	Pt	Pd	In	Ag	Ir	Zn

No. 1	1.00	1.00	48.80	48.80	—	0.20	0.20
No. 2	1.00	1.00	38.80	38.80	20.00	0.20	0.20
No. 3	1.00	1.00	34.32	32.98	30.00	0.20	0.50
No. 4	1.00	1.00	36.34	30.96	30.00	0.20	0.50
No. 5	1.00	1.00	36.62	35.18	25.00	0.20	1.00
No. 6	1.00	1.00	38.77	33.03	25.00	0.20	1.00
No. 7	1.00	1.00	40.12	34.18	22.00	0.20	1.50
No. 8	1.00	1.00	38.77	33.03	24.00	0.20	2.00
No. 9	4.00	—	37.04	31.76	26.00	0.20	1.00
No. 10	3.00	—	32.20	31.10	33.00	0.20	0.50
No. 11	3.00	—	33.70	32.60	30.00	0.20	0.50
No. 12	3.00	—	35.70	30.60	30.00	0.20	0.50
No. 13	3.00	—	36.77	26.83	33.00	0.20	0.20
No. 14	3.00	—	35.03	25.57	36.00	0.20	0.20

The composition of the dental alloy for machining by a CAD/CAM system according to the third embodiment of the present invention is configured such that palladium-indium-silver which are metals already used in conventional alloys for casting are provided as main components, the amounts of gold and platinum are minimized, and a small amount of iridium is added, wherein the ratio of palladium and indium is maintained to keep a yellow gold color, and the amount of silver may be set in the range of 0-40 wt %. Furthermore, the amount of cobalt may be set in the range of 0-0.9 wt % to enhance bondability with porcelain, and using an alloy having no cobalt as a control, the alloys are designed depending on the amounts of silver and cobalt. The alloy compositions are shown in Table 3 below.
The composition of the dental alloy for machining by a CAD/CAM system according to the fourth embodiment of the present invention is configured such that palladium-indium-silver which are metals already used in conventional alloys for casting are provided as main components, the amounts of gold and platinum are minimized, and small amounts of zinc and iridium are added, wherein the ratio of palladium and indium is maintained to keep a yellow color, and the amounts of silver and zinc may be set in the range of 0-40 wt % and 0.2-2 wt %, respectively. Furthermore, the amount of cobalt may be set in the range of 0-0.9 wt % to enhance bondability with porcelain, and using an alloy having no cobalt as a control, the alloys are designed depending on the amounts of silver, cobalt, and zinc. The alloy compositions are shown in Table 4 below.

TABLE 3

<Alloy Composition of 3^rdEmbodiment>

Element (wt %)

	Au	Pt	Pd	In	Ag	Ir	Co

No. 1	1.00	1.00	48.90	48.90	—	0.20	—
No. 2	1.00	1.00	49.41	47.49	—	0.20	0.90
No. 3	1.00	1.00	46.89	40.01	10.00	0.20	0.90
No. 4	1.00	1.00	44.31	42.59	10.00	0.20	0.90
No. 5	1.00	1.00	46.22	39.38	11.50	0.20	0.70
No. 6	1.00	1.00	44.55	37.95	15.00	0.20	0.30
No. 7	1.00	1.00	44.63	38.02	15.00	0.20	0.15
No. 8	1.00	1.00	43.55	37.10	17.00	0.20	0.15
No. 9	1.00	1.00	43.47	37.03	17.00	0.20	0.30
No. 10	2.00	—	41.36	35.24	21.00	0.20	0.20
No. 11	3.00	—	35.10	32.40	29.00	0.20	0.30

TABLE 4

<Alloy Composition of 4^thEmbodiment>

Element (wt %)

	Au	Pt	Pd	In	Ag	Ir	Zn	Co

No. 1	1.00	1.00	48.80	48.80	—	0.20	0.20	—
No. 2	1.00	1.00	49.16	47.24	—	0.20	0.50	0.90
No. 3	1.00	1.00	46.39	39.51	10.00	0.20	1.00	0.90
No. 4	1.00	1.00	43.81	42.09	10.00	0.20	1.00	0.90
No. 5	1.00	1.00	46.22	39.38	10.00	0.20	1.50	0.70
No. 6	1.00	1.00	43.47	37.03	15.00	0.20	2.00	0.30
No. 7	1.00	1.00	43.55	37.10	15.00	0.20	2.00	0.15
No. 8	4.00	—	37.04	31.56	26.00	0.20	1.00	0.20
No. 9	3.00	—	32.20	30.90	33.00	0.20	0.50	0.20
No. 10	3.00	—	33.70	32.40	30.00	0.20	0.50	0.20
No. 11	3.00	—	35.70	30.40	30.00	0.20	0.50	0.20
No. 12	3.00	—	36.77	26.63	33.00	0.20	0.20	0.20
No. 13	3.00	—	35.03	25.37	36.00	0.20	0.20	0.20

The manufacture of alloys thus designed and the evaporation of properties thereof are described below.
1. Manufacture of Alloy
1) Vacuum induction melting
A raw material for an alloy, having a purity of 99.9% or more, was used to minimize the effects of trace components. The melting was conducted using a typical vacuum induction melting furnace. Specifically, the raw material was placed in the melting furnace and the inside of the melting furnace was vacuum evacuated up to 5.0×10⁻⁵Torr in order to prevent the effects of oxygen and impurities in the melting furnace on alloys during melting, after which the melting furnace was filled with argon gas, following by performing melting.
2) Heat Treatment
In order to solve non-uniformity problems of melted cast alloys and to relieve stress, heat treatment was conducted at 800° C. for 1 hr in an electric furnace.
3) Cutting
The heat treated ingot was cut to an appropriate size using a cutting machine for CAD/CAM, thus forming ingot blocks.
4) Machining
The cut ingot blocks were installed onto a milling machine (Ener-mill) of a CAD/CAM system, and a prosthesis model to be manufactured was scanned using a scanner. The scanned data and processing conditions were adjusted and input to a computer of the CAD/CAM system, followed by performing processing at steps of rough cut, intermediate cut, and finishing cut.
2. Evaluation of Properties of the Alloys
1) Measurement of Hardness
In order to evaluate changes in surface hardness of the dental alloys for machining by a CAD/CAM system according to the present invention, the hardness was measured before and after heat treatment using a micro-hardness tester. The hardness was determined by applying a load of 4.903 N for 10 sec, observing indentations, and measuring the lengths of the X axis and the Y axis of the indentation diagonal line. The test was conducted a total of ten times on different measurement portions. Eight measurement values, excluding the highest numeral value and the lowest numeral value, were averaged. To evaluate the processing difficulty, these values were converted into Rockwell hardness values.
Table 5 below shows the hardness measurement results of the alloys of the first embodiment, Table 6 below shows the hardness measurement results of the alloys of the second embodiment, Table 7 below shows the hardness measurement results of the alloys of the third embodiment, and Table 8 below shows the hardness measurement results of the alloys of the fourth embodiment. As is apparent from these tables, the alloys of the first to fourth embodiments of the present invention had a Rockwell hardness distribution in the range of 3-23.3 after heat treatment under conditions of an appropriate ratio of Pd and In and the addition of Ag. Accordingly, the alloys of the first to fourth embodiments of the present invention can be seen to have hardness that is appropriate for mechanical cutting. Also, because the lifetime of processing tools decreases at higher hardness, the use of an alloy having lower hardness is favorable in terms of profitability.

TABLE 5

<Hardness Measurement Results of Alloy of 1^stEmbodiment>

Measurement Results

Before Heat Treatment

After Heat Treatment

Micro-	Rockwell	Micro-
hardness (Hv)	(HRC)	hardness (Hv)	Rockwell (HRC)

No. 1	200	11	198	10.3
No. 2	235	21.8	188	7.2
No. 3	198	11	171	3.3
No. 4	189	8.2	166	3.0
No. 5	215	14.3	179	4.8
No. 6	206	12.8	174	3.7
No. 7	203	12.4	172	4.1
No. 8	205	12.7	173	4.3
No. 9	201	11.0	168	3.1
No. 10	198	10.5	190	7.9
No. 11	190	7.7	185	6.8
No. 12	192	8.1	180	5.0
No. 13	188	7.3	172	4.2
No. 14	186	6.9	174	4.0
No. 15	190	7.6	175	3.8

TABLE 6

<Hardness Measurement Results of Alloy of 2^ndEmbodiment>

Measurement Results

Before Treatment

After Heat Treatment

Micro-	Rockwell	Micro-
hardness (Hv)	(HRC)	hardness (Hv)	Rockwell (HRC)

No. 1	203	11	196	10
No. 2	240	20	185	7
No. 3	200	11	168	3
No. 4	191	8.6	171	3.9
No. 5	219	14.4	177	5
No. 6	209	13.1	172	3.8
No. 7	208	12.7	175	4.5
No. 8	207	12.6	171	4.3
No. 9	201	11.2	182	7.8
No. 10	197	10.3	179	6.0
No. 11	205	11.8	185	5
No. 12	198	10.5	178	5.6
No. 13	203	11.2	185	7.9
No. 14	196	10.1	176	4.8

TABLE 7

<Hardness Measurement Results of Alloy of 3^rdEmbodiment>

Measurement Results

Before Heat Treatment

After Heat Treatment

Micro-	Rockwell	Micro-
hardness (Hv)	(HRC)	hardness (Hv)	Rockwell (HRC)

No. 1	240	20.7	225	17.2
No. 2	246	22.8	250	22.9
No. 3	241	20.6	231	17.8
No. 4	239	19.7	228	17.4
No. 5	215	15.5	202	11.3
No. 6	216	15.3	206	11.8
No. 7	215	15.4	205	12.1
No. 8	213	14.0	201	11.2
No. 9	208	12.2	198	10.3
No. 10	210	13.7	200	10.8
No. 11	202	11.5	194	9.7

TABLE 8

<Hardness Measurement Results of Alloy of 4^thEmbodiment>

Measurement Results

Before Thermal Treatment

After Thermal Treatment

Micro-		Micro-	Rockwell
hardness (Hv)	Rockwell (HRC)	hardness (Hv)	(HRC)

No. 1	245	21.0	227	17.6
No. 2	248	22.0	256	23.3
No. 3	239	20.1	229	17.6
No. 4	238	19.8	230	17.9
No. 5	219	15.3	203	11.5
No. 6	219	15.2	204	12.0
No. 7	219	15.3	208	12.8
No. 8	214	15.0	200	10.5
No. 9	208	12.7	198	10.1
No. 10	205	11.9	193	8.9
No. 11	201	10.8	195	10.0
No. 12	198	10.3	186	8.2
No. 13	194	9.7	183	7.7

2) Measurement of Processing Time
In the processing of the alloys for machining by a CAD/CAM system according to the present invention, the alloys of the first and second embodiments were processed in such a manner that zirconia blocks and single crown models were scanned and then machined by means of the computer-aided milling machine (Ener-mill) that is the same as above. As such, the processing time values were measured and compared. The results are shown in Table 9 below.
Also, the alloys of the third and fourth embodiments were processed in such a manner that zirconia blocks and single coping models were scanned and then machined by means of the computer-aided milling machine (Ener-mill) that is the same as above. As such, the processing time values were measured and compared. The results are shown in Table 10 below.
Alloy processing using a milling machine and end mills for exclusive use of metal was conducted by using different end mills at steps of rough cut, intermediate cut, and finishing cut as in processing of conventional zirconia. Because the processing time is regarded as important to determine productivity and profitability, the processing time of the alloy was compared with the processing time of conventional zirconia. As a result, the dental alloys for machining by a CAD/CAM system according to the present invention, for example, the alloys of the first and second embodiments, can be seen to have a processing time of 20-40 min based on CAD/CAM machining, which is similar to 25 min that is the processing time of conventional zirconia.
Furthermore, the alloys of the third and fourth embodiments can be seen to have a processing time of 18-30 min based on CAD/CAM machining, which is similar to 15 min that is the processing time of conventional zirconia.

TABLE 9

<Processing Time Comparison of Alloys of 1^stand 2^ndEmbodiments and
Zirconia>

Alloy of 1^st	Alloy of 2^nd
Embodiment	Embodiment	Zirconia

No. 1	40 min	No. 1	40 min	25 min
No. 2	35 min	No. 2	35 min
No. 3	20-25 min	No. 3	20-25 min
No. 4	20-25 min	No. 4	20-25 min
No. 5	20-25 min	No. 5	20-25 min
No. 6	20-25 min	No. 6	20-25 min
No. 7	20-25 min	No. 7	20-25 min
No. 8	20-25 min	No. 8	20-25 min
No. 9	20-25 min	No. 9	20-25 min
No. 10	20-25 min	No. 10	20-25 min
No. 11	20-25 min	No. 11	20-25 min
No. 12	20-25 min	No. 12	20-25 min
No. 13	20-25 min	No. 13	20-25 min
No. 14	20-25 min	No. 14	20-25 min
No. 15	20-25 min

TABLE 10

<Processing Time Comparison of Alloys of 3^rdand 4^thEmbodiments and
Zirconia>

Alloy of 3^rd	Alloy of 4^th
Embodiment	Embodiment	Zirconia

No. 1	30 min	No. 1	30 min	15 min
No. 2	35 min	No. 2	35 min
No. 3	25 min	No. 3	25 min
No. 4	25 min	No. 4	25 min
No. 5	18-20 min	No. 5	18-20 min
No. 6	18-20 min	No. 6	18-20 min
No. 7	18-20 min	No. 7	18-20 min
No. 8	18-20 min	No. 8	18-20 min
No. 9	18-20 min	No. 9	18-20 min
No. 10	18-20 min	No. 10	18-20 min
No. 11	18-20 min	No. 11	18-20 min
		No. 12	18-20 min
		No. 13	18-20 min

3) Analysis of Pore Distribution of Prosthesis
The prosthesis manufactured by a casting process using a conventional dental alloy and the prosthesis manufactured by CAD/CAM machining using the dental alloy for machining by a CAD/CAM system according to the present invention were vertically cut to analyze the distribution of pores in the prostheses. These pores were observed using a scanning electron microscope (SEM) and compared to those of the prosthesis manufactured by casting.
FIG. 1( a) is an SEM image showing the vertical cut surface of the prosthesis cast from the conventional dental alloy.
FIG. 1( b) is an SEM image showing the vertical cut surface of the prosthesis manufactured by CAD/CAM machining using the dental alloy for machining by a CAD/CAM system according to the present invention.
FIG. 2( c) is a metal microscope image showing the vertical cut surface of the prosthesis cast from the conventional dental alloy.
FIG. 2( d) is a metal microscope image showing the vertical cut surface of the prosthesis manufactured by CAD/CAM machining using the dental alloy for machining by a CAD/CAM system according to the present invention.
As shown in FIGS. 1( a), 1(b), 2(c), and 2(d), the prosthesis manufactured by CAD/CAM machining using the dental alloy for machining by a CAD/CAM system according to the present invention had a smaller number of pores and a more uniform structure compared to the prosthesis cast from the conventional dental alloy.
In accordance with the embodiments of the present invention, the dental alloy includes palladium, indium, and silver (Ag) as main components, thus reducing the manufacturing cost, unlike conventional casting alloys composed mainly of expensive gold (Au). Also, the dental alloy for machining by a CAD/CAM system having equivalent processibility to that of zirconia that can be machined using a conventional CAD/CAM system can be provided, thus enabling automated machining by a CAD/CAM system upon prosthesis manufacturing. Therefore, prostheses can be more precisely and uniformly manufactured compared to when using a conventional casting process, and the manufacturing process of the prostheses can be simplified, thereby reducing the manufacturing time and the personnel expenses due to automation.

Claims

1. A dental alloy for machining by a CAD/CAM system, comprising 0.1-5.0 wt % of gold (Au), 30-50 wt % of palladium (Pd), 25-50 wt % of indium (In), 10-40 wt % of silver (Ag), and 0.1-0.3 wt % of iridium (Ir).

2. The A dental alloy for machining by a CAD/CAM system, of claim 1, further comprising 0.1-5.0 wt % of platinum (Pt).

3. The A dental alloy for machining by a CAD/CAM system, of claim 1, further comprising 0.01-2.5 wt % of zinc (Zn).

4. The dental alloy of claim 1, further comprising 0.1-5.0 wt % of platinum (Pt) and 0.01-2.5 wt % of zinc (Zn).

5. The dental alloy of claim 1, further comprising 0.1-1.0 wt % of cobalt (Co).

6. The dental alloy of claim 1, further comprising 0.1-5.0 wt % of platinum (Pt) and 0.1-1.0 wt % of cobalt (Co).

7. The dental alloy of claim 1, further comprising 0.1-0.3 wt % of iridium (Ir), 0.1-1.0 wt % of cobalt (Co) and 0.01-2.5 wt % of zinc (Zn).

8. The dental alloy of claim 1, further comprising 0.1-5.0 wt % of platinum (Pt), 0.1-1.0 wt % of cobalt (Co), and 0.01-2.5 wt % of zinc (Zn).