The Influence of Condensing Technique and Accelerator Concentration on Some Mechanical Properties of an Experimental Bioceramic Dental Restorative Material

摘要

In this paper the influence of condensing technique and accelerator concentration on hardness and dimensional stability of an experimental version of the bioceramic filling material Doxa?T is tested. In addition a simple test of the setting time depending on accelerator concentration has also been done together with a test showing the temperature increase experienced in the bottom of a cavity when condensing with ultrasonic tips and varying the amplitude. In order to achieve early age hardness (after 4 hours) an addition of lithium to the hydration liquid is necessary if condensing is made manually. The ultrasonic vibrations bring the filler grains closer together yielding a denser end product where the maximum pore size is decreased as compared with a manually condensed sample. When using ultrasonic condensing no lithium is needed. The ultrasonic tip also transfers extra energy, mainly in the form of heat, to the material, which may speed up the hydration giving improved early age properties. Condensing withthe ultrasonic device also gives higher long-term (64 days) hardness than the manual condensing. The samples condensed with the ultrasonic device and with 0 and 18mM LiCl both showed a hardness of about 150 HV(100g) after 64 days. Both for manual and ultrasonic condensing the highest hardness is achieved by using no or low additions of lithium. Regarding the dimensional stability no differences could be seen either for the different accelerator concentrations or for the different condensing!! techniques. The setting time is roughly the same for the three different accelerator concentrations and undetectable with this method when not using any lithium. The temperature rise in the filling when condensing with the ultrasonic device is dependent on the amplitude of the vibrations and the contact time between tip and filling.