Preliminary investigation into the effect of a new technique for ultrasonic packing of composite resin

The use of composite resin has been increasingly growing during the last decade. The clinical performance and the properties of the material are greatly influenced by the technique used for packing the material in the prepared cavity. Eighty samples, divided into four equal groups of 20 teeth each, were prepared in Heliotest teflon split die using Durafil composite. Group A samples were packed under constant load of 250 gm. for 10, 20 and 30 seconds. Groups B,C and D were packed under the same constant load but with the application of the ultrasonic energy for 10, 20 and 30 seconds. The tested specimens were evaluated, by two operators separately, for the quality of the line and point angles, number and size of the voids using an Environmental Scanning Electron Microscope [ESEM]. Results revealed superiority of the ultrasonic energy packing over the conventional pressure packing technique regarding all the parameters of the evaluation. A filler free layer [FFL] was observed at the side of ultrasonic energy application and resulted in a matrix rich layer on the surface of the samples. These findings were attributed to the increase in the flow of the composite material due to the acoustic energy applied and though increasing the adaptation of the material and decreasing the number and size of the voids in the originally viscous composite. Further investigations into the effects of ultrasonic packing on physical properties of composite restorative materials are needed

SEM study of glass ionomer cement surface: to ETCH or not to ETCH?

Fifteen specimens of Ketac-Cem GIC were packed in Heliotest teflon split die. They were divided into three equal groups of five teeth each where they were either left untreated [control] or etched using 37% phosphoric acid. The etched samples were either etched after 15 min. or 24 hours from the start of the mix then the GIC surfaces were washed using air water spray for 30" and dried using oil free compressed air. SEM photomicrograph were taken to study the microstructure and the surface roughness of the GIC samples. The micro graphs revealed increased roughness of the samples etched after 24 hours followed by that of the untreated control surface then the 15 min. etched surface of the GIC samples. The GIC surface may be either left unetched to avoid the future deterioration of the surface or to postpone the etching treatment for at least 24 hours to allow the GIC to set undisturbed to avoid the damaging effects of premature etching of the matrix on the GIC surface