ISO 17304:2013 pdf free
ISO 17304:2013 pdf free.Dentistry一Polymerization shrinkage: Method for determination of polymerization shrinkage of polymer-based restorative materials
The immersion depth of the lower weighing pan of the density determination apparatus (4.4.2) shall be at least 20 mm to ensure complete immersion. Immersion depth is measured from the upper edge of the weighing pan to the meniscus of the buoyancy medium.
For flowable materials, the specimen and the dish shall be completely immersed.
NOTE The density determination apparatus supplied by various manufacturers differ with regard to the height and diameter of their water bowls. It is necessary to establish a standard immersion depth for the lower weighing pan in the buoyancy medium to ensure complete immersion.
NOTE 1 This solution can be stored for four weeks at room temperature.On the day of the test, pour the necessary amount of buoyancy medium into the water bowl of the determination apparatus in accordance with the distance specifications in 4.5.1 and place it in the desiccator (4.4.6).
Degas the buoyancy medium by evacuating the desiccator at a temperature of (23±2) °C using the vacuum pump (4.4.5). Immediately after a vacuum pressure of (50±10) mbar is attained, close the desiccator vacuum port. After (20±5) min, carefully ventilate the dessicator.
NOTE 2 This pressure was chosen so that the water does not boil.
Afterwards, the buoyancy medium shall be kept at a temperature of (23±2) °C for at least 2 h.Read the density of the buoyancy medium for the current measuring temperature from Table 1.
NOTE 3 The density of water is applied instead of the precise density of the buoyancy medium. The dependence on temperature will thereby be taken into account. The accuracy of the measured polymerization shrinkage will thereby not be impaired because the differences in the respective densities balance each other out.
Tare the balance (4.4.1) with the density determination apparatus (4.4.2) in place. Place two of the test specimens in position 1 of the measuring apparatus and measure their total mass and record this measurement as mc,1. Remove the test specimens from the balance.Measure the temperature of the buoyancy medium and record this value.
Tare the balance again. Place the same two test specimens in position 2 of the measuring apparatus and measure their total mass in the buoyancy medium; record this value as mc,2. Carefully remove any adhering air bubbles during this procedure.Repeat the test five times with further pairs of test specimen for each test. Discard the specimens after the tests.ISO 17304 pdf download.
