1、BRITISH STANDARD BS 4284:1981 Specification for Dental impression pastes (zinc oxide type) UDC 616.314 089.28:661.847.12BS4284:1981 This British Standard, having been prepared under the directionof the Dental StandardsCommittee, was published under the authority ofthe Board of BSI and comes intoeffe
2、ct on 30 November 1981 BSI 11-1999 First published March 1968 First revision November 1981 The following BSI references relate to the work on this standard: Committee reference DNS/4 Draft for comment 80/63051 DC ISBN 0 580 12274 3 Cooperating organizations The Dental Standards Committee, under whos
3、e direction this British Standard was prepared, consists of representatives from the following: Association of Dental Hospitals of the United Kingdom* British Dental Association* British Dental Trade Association* British Society for the Study of Prosthetic Dentistry Dental Materials Panel* Departmen
4、t of Health and Social Security* Department of Industry (Laboratory of the Government Chemist)* Department of Industry (National Engineering Laboratory) Department of Industry (National Physical Laboratory) Federation Dentaire Internationale Institute of Dental Surgery Ministry of Defence* Royal Soc
5、iety of Medicine Scottish Health Services Scottish Home and Health Department The organizations marked with an asterisk in the above list, together with the following, were directly represented on the Technical Committee entrusted with the preparation of this British Standard: British Institute of S
6、urgical Technologists British Society for Restorative Dentistry British Society for the Study of Orthodontics Dental Laboratories Association Limited London Dental Study Club Society of University Dental Instructors Amendments issued since publication Amd. No. Date of issue CommentsBS4284:1981 BSI 1
7、1-1999 i Contents Page Cooperating organizations Inside front cover Foreword ii 1 Scope 1 2 References 1 3 Definitions 1 4 Requirements 1 5 Sampling 1 6 Test methods 2 7 Packaging and marking 5 Figure 1 Apparatus for determination of consistency 3 Figure 2 Penetrometer for determination of working t
8、ime 4 Figure 3 Balanced beam instrument for determination of strain incompression 5 Figure 4 Split mould for dimensional stability and detail reproduction 6 Publications referred to Inside back coverBS4284:1981 ii BSI 11-1999 Foreword This British Standard, which was originally published in1968, has
9、 been revised under the direction of the Dental Standards Committee. This standard supersedes the1968 edition, which has now been withdrawn. The main changes from the original edition are as follows. a) The scope has been widened slightly to include types using not only eugenol, but substitutes for
10、eugenol. b) The consistency requirement (disc diameter) has been amended, and the load is applied at90s, not105s. c) Setting time, as such, is not evaluated, since available test methods are unable to define a specific setting time. Test methods requiring the fully set material (i.e.strain in compre
11、ssion and detail reproduction) utilize the minimum time that the manufacturer recommends the impression should be left in the mouth, thus ensuring that all operators use the same time and thereby producing comparable results. d) The working time is measured by a penetrometer, not a rheometer. e) All
12、 tests are undertaken at23 1 C, not20 1 C, to align with current testing practice. 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 itsel
13、f confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to6, 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 indicat
14、ed in the amendment table on the inside front cover.BS4284:1981 BSI 11-1999 1 1 Scope This British Standard specifies characteristics of dental impression pastes, the principal ingredients of which are a base (zinc oxide) and an activator (eugenol or eugenol substitute). 2 References The titles of t
15、he publications referred to in this standard are listed on the inside back cover. 3 Definitions For the purposes of this British Standard the following definitions apply. 3.1 mixing time the time required to produce a uniformly coloured and homogeneous mixture of the components 3.2 working time the
16、period of time between the start of mixing and the effective commencement of setting as determined in6.3 3.3 setting time the period of time, measured from the start of mixing, during which the material has suitable plastic properties that permit an impression to be taken 4 Requirements 4.1 Componen
17、ts. The impression paste shall consist of a base and an activator which, when mixed in accordance with the manufacturers instructions, will react to form a paste suitable for taking oral impressions. The base and activator shall be supplied in contrasting colours in order to give a means of indicati
18、on when a homogeneous mix has been achieved. When supplied in tubes, the components shall be capable of being extruded, without difficulty, at a temperature of18 C to25 C. 4.2 Irritation and freedom from toxicity. The mixed paste, when used in accordance with the manufacturers instructions, shall ne
19、ither cause irritation of the normal oral mucosa, nor contain poisonous ingredients in sufficient concentration to be harmful to human beings. NOTEBS5828 gives guidance on the assessment of such biological hazards. 4.3 Consistency. When tested in accordance with6.2, the mean diameter of the discs sh
20、all be30mm to45mm. The mixed paste shall be free from foreign material, granules and crystals. 4.4 Working time. The working time, determined in accordance with6.3, shall be not less than2.5min or the time stated by the manufacturer, whichever is the greater. 4.5 Strain in compression. The strain in
21、 compression, when tested in accordance with6.4, shall not exceed12%. 4.6 Dimensional stability. When tested in accordance with6.5, the length shall not show a variation of more than 0.2%. 4.7 Detail reproduction. When tested in accordance with6.5, the set paste shall take a satisfactory impression
22、of the longitudinal groove of0.025mm width, when examined under low angle illumination and without magnification. 4.8 Compatibility with gypsum. Either dental artificial stone or dental laboratory plaster, when poured against the surface of the set paste, shall reveal no surface defect nor adhere to
23、 the paste when separated from it. The model shall have a smooth non-friable surface and, for the full width of the specimen, shall reproduce the0.050mm groove. The0.025mm groove shall also be readily visible. 4.9 Manufacturers instructions. Adequate and accurate instructions for use shall accompany
24、 each package. These instructions shall include the following information: a) instructions for the preparation and mixing of the component pastes; b) the type of mixing apparatus; c) the conditions for mixing; d) the ratio of the base paste to activator paste, by mass; e) the mixing time; f) the wor
25、king time; g) the minimum time the impression should be left in the mouth. 5 Sampling Representative samples of the component pastes, sufficient to produce250g of paste when mixed in accordance with the manufacturers instructions, are required for testing. The method of procurement shall be the subj
26、ect of agreement by the parties concerned.BS4284:1981 2 BSI 11-1999 6 Test methods 6.1 Testing conditions. Prepare all specimens and conduct all tests at a temperature of23 1 C, except for the water bath which shall be maintained at a temperature of32 1 C (see6.4.1.5), and relative humidity of505%.
27、Mix the paste in accordance with the manufacturers instructions. Proportion all test pastes by mass to a tolerance of 0.1g. 6.2 Consistency 6.2.1 Apparatus 6.2.1.1 Load, of1 500 2g mass, mounted in a loading device, such as that shown inFigure 1, in such a manner as to allow essentially frictionless
28、 movement of the movable column in the vertical direction. 6.2.1.2 Glass delivery tube, of approximately10mm internal diameter, designed to deliver0.5 0.02ml, by means of a plunger. 6.2.1.3 Two glass plates, approximately60mm square and of mass202g each. 6.2.1.4 Polyethylene sheet, 0.025mm thick. 6.
29、2.2 Procedure. Using the delivery tube, dispense0.5ml of the mixed paste onto a polyethylene sheet on one of the glass plates. Gently lower the second glass plate, faced with a polyethylene sheet, and the1 500g load onto the material,90s after the start of mixing. NOTEDuring the testing procedure it
30、 is essential that the glass plates be maintained parallel and that no rotational movement be allowed to take place. After15s, remove the load and measure the diameter of the paste disc to the nearest0.5mm, across two diameters at right angles to each other. Calculate the mean of these two measureme
31、nts for each specimen. Record the average of three determinations to the nearest millimetre. 6.3 Working time 6.3.1 Apparatus 6.3.1.1 Penetrometer, with a cylindrical indentor of4.0mm diameter exerting a total vertical load of0.49N (50gf), and a dial gauge accurate to0.01mm, as shown inFigure 2. 6.3
32、.1.2 Smooth and flat base plate made of glass or metal 6.3.1.3 Metal ring, of30mm internal diameter,34mm outside diameter and3mm height. 6.3.2 Procedure. Place the base plate under the tip of the indentor and record the fiducial reading. Place the ring on the base plate and fill with paste, mixed ac
33、cording to the manufacturers instructions. Strike the top surface level and, at2min from the start of mixing, apply the tip of the indentor to the surface of the material and release. Read the dial gauge10s after release and record the thickness of the material under the indentor. Repeat the test at
34、30s intervals, cleaning the indentor between tests, until the depth of paste beneath the indentor is greater than0.25mm. Plot the thickness of the material against time (from the start of mixing), and calculate the working time as that time when the thickness of the material is exactly0.25mm. Record
35、 the working time as the average of three determinations, to the nearest30s. 6.4 Strain in compression 6.4.1 Apparatus 6.4.1.1 Metal split mould, which allows easy removal of the test specimen of20.0 0.2mm length and12.5 0.2mm diameter. 6.4.1.2 Two flat metal plates, measuring approximately50mm squa
36、re and3mm thick. 6.4.1.3 Small G clamp 6.4.1.4 Compression testing instrument, capable of applying the required strain quickly and accurately. The balanced beam instrument shown inFigure 3 is a suitable instrument for this test, consisting essentially of a rigid beam approximately1m long and pivoted
37、 about its centre point on ball races. At one end of the beam is mounted the platen A, on the rod B, so that the platen is totally submerged in water, and the distance between the lower surface of the platen and the base of the water bath is approximately20mm, when the beam is horizontal. The dial g
38、auge is mounted above the rod B, and is used to ascertain the position of the beam at any time; the positioning is made more precise by the electrical contacts C and associated circuit. The screw D is used to make this reading. Preliminary balancing of the beam is achieved with the sliding weight, J
39、, whilst the screw E is used for finely balancing the beam. Maintain the water bath at a temperature of32 1 C. Before the test, place a500g and a5g mass on the pan G, and balance the beam accurately.BS4284:1981 BSI 11-1999 3 6.4.1.5 Water bath, controlled at32 1 C, in addition to the water bath desc
40、ribed in6.4.1.4. 6.4.2 Procedure. Place the mixed paste in the split mould using a spatula, and place a metal plate at each end of the mould. Bring the plates into contact with the ends of the mould by means of the G clamp, thus exuding excess material from the mould. At the working time (as determi
41、ned in6.3), place the assembly in the water bath (6.4.1.5). The mould shall remain in the water bath for the minimum time recommended by the manufacturer for removing the impression material from the mouth see4.9 g). At the end of this time, open the mould under water at32 1 C, transfer the test spe
42、cimen to the water bath of the balanced beam instrument and align vertically under the platen. Remove the5g mass from pan G,105s after removal of the test specimen from the water bath, thus exerting a force of0.05N (5gl) on the test specimen.15s later, take a reading X on the dial gauge. Immediately
43、 remove the500g mass, thus exerting a load of4.9N (500gf) on the test specimen.5min after this stress is applied, take a second reading Y. Record the strain in compression as the average of three determinations, to the nearest0.1%. 6.5 Dimensional stability and detail reproduction 6.5.1 Apparatus 6.
44、5.1.1 Split mould and a metal base plate, as shown inFigure 4. 6.5.1.2 Travelling microscope, accurate to0.01mm. NOTEThis is not necessary for6.5.3.1. 6.5.1.3 Polyethylene sheet, 0.025mm thick. 6.5.1.4 Flat metal plate, sufficiently large to cover the mould. 6.5.1.5 Flat glass plate, sufficiently la
45、rge to cover the mould. 6.5.1.6 A water bath, maintained at32 1 C. 6.5.2 Preparation of test specimen. Lubricate the mould and base plate with a mould release agent, ensuring that no excess lubricant is left in the grooves of the base plate. Slightly overfill the mould with freshly mixed paste. Plac
46、e the sheet of polyethylene over the material, and use the metal plate to press out the excess paste. Transfer the whole assembly to the water bath at the working time (as determined in6.3). The mould shall remain in the water bath for the minimum time recommended by the manufacturer for removing th
47、e impression from the mouth see4.9 g). At the end of this time, remove the assembly from the water bath and separate the specimen from the mould in such a way as to minimize distortion of the specimen. 6.5.3 Procedure NOTEIt is not necessary to prepare separate test specimens for6.5.3.1 and6.5.3.2,
48、as both tests may be carried out on the same specimen. 6.5.3.1 Detail reproduction. View the test specimen with the impression of the grooves uppermost and using low angle illumination. Figure 1 Apparatus for determination of consistency Strain in compression %() XY 20 -100 =BS4284:1981 4 BSI 11-199
49、9 Figure 2 Penetrometer for determination of working timeBS4284:1981 BSI 11-1999 5 6.5.3.2 Dimensional stability. Place the test specimen, with the lines formed from the base plate uppermost, on the glass plate which has been dusted with talc.5min after removal from the water bath, measure the distance between the crosses, formed from the intersection of the centre longitudinal and the two transverse lines of the base plate, using the travelling microscope and take a reading X mm. Take a second reading,
