1、BRITISH STANDARD BS 5189-3: 1975 Specification for Dental casting investments Part 3: Ethyl silicate-bonded investment materials UDC 616.314089.27:661.718.5BS5189-3:1975 This British Standard, having been approved by the Dental Industry Standards Committee,was published underthe authorityof the Exec
2、utive Boardon 27March1975 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference DNMH/4/3 Draft for comment 73/60911 ISBN 0 580 08901 0 Co-operating organizations The Dental Industry Standards Committee, under whose supervision this British Standard was pre
3、pared, consists of representatives from the following Government departments and scientific and industrial organizations: Association of Dental Hospitals of Great Britain and Northern Ireland* British Dental Association* British Dental Trade Association* British Plastics Federation Dental Education
4、Advisory Council Department of Health and Social Security* Department of Industry Laboratory of the Government Chemist* Department of Industry National Engineering Laboratory Ministry of Defence* Royal Society of Medicine Scottish Home and Health Department The Government departments and scientific
5、and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: British Institute of Surgical Technicians Dental Laboratories Association Institute of Dental Surge
6、ry London Dental Study Club Individual expert Amendments issued since publication Amd. No. Date of issue CommentsBS5189-3:1975 BSI 12-1999 i Contents Page Co-operating organizations Inside front cover Foreword ii 1 Scope 1 2 Reference 1 3 Requirements 1 4 Sampling 1 5 Test methods 1 6 Marking 4 Appe
7、ndix A Conversion table 5 Figure 1 Diagram of thermal expansion equipment 6 Figure 2 Mould and former used in thermal expansion test 7 Figure 3 Transverse strength test apparatus 7 Figure 4 Diagram of furnace and lever system suitable for high temperaturetransverse strength tests 8 Publication refer
8、red to Inside back coverBS5189-3:1975 ii BSI 12-1999 Foreword This British Standard forms one of a series on dental equipment and materials, prepared under the authority of the Dental Industry Standards Committee. The technique employed in mixing and using dental casting investments is almost as cri
9、tical as their chemical composition in governing their behaviour and properties under normal laboratory conditions. This fact is known, appreciated and made use of both by those people handling dental investments and by those responsible for their manufacture. It does, however, make the specificatio
10、n of a standardized mixing technique and consistency for use in preparation of the test specimen quite impossible, and reference has therefore been made to the manufacturers instructions. To safeguard the interests of the consumer in this respect, special attention has been paid to the subject of in
11、formation on mixing techniques and expansion, with a requirement that ample data on these items be included in every package of material. Ethyl silicate investment materials have a number of characteristics which set them apart from other dental casting materials. Firstly, there is the critical impo
12、rtance of the particle size distribution in the setting reaction and thermal expansion unless the manufacturer uses a suitable mixture of particle sizes the material will not set and the expansion will be unsatisfactory. As such a deficiency will automatically preclude an investment from even being
13、considered for compliance with the terms of a specification, the committee responsible for this standard decided that the inclusion of the usual sieving test, which features in Parts1 and2, was unnecessary. Another characteristic is the prolonged gelling type of reaction which takes place during set
14、ting. This presents a number of problems in definition and determination of what could be described as a set condition, and in this instance also it was considered that with the safeguard provided by the other requirements for physical properties, there was no immediate need for inclusion of a speci
15、al test just to determine an arbitrary set for these materials. Lastly, it will be noticed that the requirement for high temperature transverse strength in this specification is slightly lower than that set for gypsum and phosphate investment materials. This is because, due to practical difficulties
16、 in actual testing, the strength of ethyl silicate materials is determined at a temperature significantly below that used in actual casting when the maximum strength will be obtained. In preparing this British Standard the opportunity has been taken to use, where applicable, SI metric units. Recogni
17、zing that some of these units may be unfamiliar, a conversion table is included inAppendix A 1)which should provide a sufficient range of equivalent values for the interpretation of the relevant clauses. Certification. Attention is drawn to the certification facilities described on the inside back c
18、over of this standard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages T
19、his document comprises a front cover, an inside front cover, pagesi andii, pages1 to8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. 1) Info
20、rmation on the international (SI) system of Units is given in BS3763 “The International System of units (SI)” and PD5686 “The use of SI units”. Tables of conversions are given in BS350“Conversion factors and tables”, Part1 “Basis of tables. Conversion factors”.BS5189-3:1975 BSI 12-1999 1 1 Scope Thi
21、s British Standard specifies requirements for ethyl silicate-bonded investment materials supplied as two or more components for use in dental casting procedures. 2 Reference The title of the British Standard referred to in this standard is given on the inside back cover. 3 Requirements 3.1 Component
22、s. The manufacturer or supplier of the investment powder shall also supply the ethyl silicate component and give full information on all other components required (see3.5). 3.2 Powder. The investment powder shall be free from undesirable extraneous material and lumps. Colouring matter shall not be r
23、egarded as extraneous material. 3.3 Expansion. The mixed investment, when tested not less than24h after the first contact of investment and binder liquid as described in5.2, shall exhibit a total expansion (covering air setting and thermal behaviour) of not less than1.5%. (Seealso further reference
24、to expansion in3.5.) 3.4 Transverse strength 3.4.1 Low temperature (green strength). The transverse strength of the set investment test pieces24h after the commencement of mixing, determined at a temperature of23 2 C and in the manner described in5.3, shall be not less than0.4MN/m 2 . 3.4.2 High tem
25、perature. The transverse strength of the set investment test pieces, determined at1000 C and in the manner described in5.3, shall be not less than0.4MN/m 2 . 3.5 Information to be provided by the manufacturer. Adequate instructions and information on the items listed ina) tof) shall accompany each c
26、ontainer. This information shall also be readily available to a prospective purchaser on demand. a) Full details of the proportioning and mixing technique, including the powder, binder liquid, additives, mixing apparatus and information on variables intended to affect the physical properties of the
27、mixed investment for specific purposes. b) Relevant information on the timing of the mixing-setting-firing sequence. c) Full details of the firing cycle, including preheating of the mould, the temperature of the furnace during the firing period, the minimum time recommended for ensuring complete bur
28、n out of a wax pattern and a temperature range within which a mould may be used for casting. d) A clear warning regarding the risk of explosion if these materials are heated in an unvented furnace. e) Full details of the following expansion characteristics of the material: 1) thermal expansion at th
29、e recommended firing temperature; 2) casting range (for definition see5.2.4). The figures quoted for these characteristics shall be to the accuracy specified under the conditions of test in clause5. f) A reference to the short shelf life of mixed binder liquid. The details given for itemsa) toc) sha
30、ll be sufficiently precise for use in preparing test specimens. 4 Sampling The method of sampling shall be agreed between the parties concerned. The interval of time between sampling and testing shall be kept as short as possible. 5 Test methods 5.1 Mixing, general 5.1.1 Temperature and humidity. Al
31、l mixing of investment shall, unless stated otherwise, be carried out at a temperature of23 2 C and a relative humidity of505%. 5.1.2 Apparatus. The following apparatus shall be used for mixing the investment in all test procedures. All apparatus and instruments listed shall be clean, dry and free f
32、rom particles of set investment. Mixing apparatus and instruments which have been used previously for other types of investment shall not be used. Before starting mixing all materials and apparatus shall be brought to a temperature of23 2 C. 5.1.2.1 A flexible bowl of suitable material (such as rubb
33、er) and size. 5.1.2.2 A dental “plaster” spatula with a curved stainless steel blade of approximately110mm 25mm 2mm.BS5189-3:1975 2 BSI 12-1999 5.1.3 Binder liquid. Refer to the manufacturers instructions for information on how to prepare the binder liquid from the ethyl silicate component. Use wate
34、r complying with the requirements of BS3978 unless stated otherwise. Use the same binder liquid for all the tests. Store at a temperature below5 C (but warm to room temperature before use) if it is intended to use the same mixed liquid over a period of more than24h. 5.1.4 Procedure. Follow the manuf
35、acturers instructions for preparing all test specimens. Unless the instructions state otherwise, always transfer the mixed investment immediately to the moulds or testing apparatus. Even if not specifically covered by the manufacturers instructions, the use of a mechanical method of mixing is permit
36、ted provided it can be established that the specimen so produced does not differ in its properties from that of one prepared using a manual method. 5.2 Thermal expansion 5.2.1 Apparatus. The following apparatus is required. 5.2.1.1 A linear thermal expansion measuring system of the vitreous silica d
37、ilatometer tube type illustrated inFigure 1 which comprises the following. a) A silica tube ST located in the “hot zone” of a tube furnace F. b) A silica rod SR which rests on top of a specimen contained within the tube ST. c) A displacement transducer DT the core of which is directly connected to t
38、he rod SR. The maximum restraint on the specimen shall not exceed1kN/m 2 A dial gauge is not recommended since it may result in excessive force (above1kN/m 2 ) being applied to the specimen, but any other device (magnetic, capacitative, optical) may be used provided that length changes are reliably
39、measured as specified. d) An automatic recording device coupled directly to the transducer DT. Alternatively, an instrument which will permit an operator to plot the expansion of the test specimen to an accuracy of 0.001mm may be used instead of an automatic recording device. e) A water jacket to pr
40、otect the mounting assembly from excessive temperature changes. The use of parts made from a suitable iron/nickel alloy 2)is also recommended to eliminate ambient temperature effects. The performance of the expansion apparatus shall be calibrated and checked periodically using a fused vitreous silic
41、a rod of the same dimensions as the test specimen (10mm diameter 100mm length). The apparatus itself shall not exhibit any change in excess of0.01mm as the temperature is varied over the intended operating range. 5.2.1.2 A metal former and tube as illustrated inFigure 2 for preparing the test specim
42、en mould. 5.2.2 Preparation of agar mould. Assemble the former (F) and tube (T) as illustrated inFigure 2(a). Heat some agar gel duplicating material in accordance with the manufacturers instructions, stirring continuously, until completely molten and free from lumps. Allow to cool to the temperatur
43、e recommended by the manufacturer for pouring and then fill the metal former/tube mould. Leave to set for40min at room temperature. Remove the metal former without disturbing the agar gel in the tube. Seal the top of the tube with a sheet of wax. 5.2.3 Procedure. Mix the investment in accordance wit
44、h the manufacturers instructions and fill the agar mould from the funnel end seeFigure 2(b) using vibration. Pour off surplus liquid in accordance with the manufacturers instructions. Free the specimen from the mould24h from the commencement of mixing. Surface the ends of the specimen flat and paral
45、lel so that it finishes with a length of1002mm. Ensure that the end surfaces of the specimen and contact surfaces of the expansion apparatus are clean and free from extraneous investment particles. Also take care to ensure good seating of the specimen. Place the specimen in the test apparatus with t
46、he furnace at room temperature, then heat to100 C. After holding this temperature for1h, heat at a rate of5 2 C/min until the manufacturers recommended temperature for casting is reached. 2) “Invar” alloy is known to be suitable.BS5189-3:1975 BSI 12-1999 3 Record the expansion at intervals of50 C if
47、 an automatic device is not used. Measure and record the temperature during the thermal expansion tests by placing the hot junction of a thermocouple as close as possible to the outside of the silica tube containing the specimen. In order to correlate the true temperature of the test specimen with t
48、hat of the measuring thermocouple, prepare an investment specimen in which a platinum/rhodium-platinum thermocouple is embedded and take this through the full heating cycle. The temperature lag of the specimen behind that of the measuring thermocouple will then be known and a correction can be appli
49、ed when reporting the results. 5.2.4 Test result. Report the test result in a linear percentage expansion using the mean of at least three determinations. Repeat the whole test if any individual value differs by more than10% from the mean. Use the results from this test procedure to record the casting range see3.5 d). For the purposes of this British Standard the casting range is defined as the range of temperature( 10 C), within which the actual expansion does not fall below0.025mm of the maximum recorded expansion. 5.3 Transve
