RESUMO
The purpose of this in vitro study was to invent a testing device similar to curved canals to investigate the cyclic fatigue of 0.04 and 0.06 Profile system by recording the time lapsed from the beginning of rotation until separation occurred. Revolution number and length of separated pieces were also determined. A metal device was designed and 120 Profile were tested after dividing them randomly into 2 equal groups from size 15-40 of the same taper either 0.04 or 0.06. The result demonstrated that the smaller size significantly resist fracture and take longer time and more revolution to separate when compared to larger sizes. The mean length of separated pieces was significantly longer [P<0.001] and near the end of the cutting section for the Profiles 0.04 when compared to those of 0.06. This may indicate that smaller diameter Profiles considered safer and stronger in clinical practice
RESUMO
A comparison was made between the apical microleakage of retrograde fillings with amalgam and with a chemically activated resin-modified glass ionomer cement using a dye penetration technique. Forty instrumented and obturated human teeth were divided into four groups of 10 teeth each. Each root was apically resected. Nail polish was applied to the tooth surfaces of the first 3 groups, and then standardized apical cavity preparations were performed. The retropreparations were filled either with zinc free amalgam [group I], chemically activated resin-glass ionomer [group II], or only covered with nail polish [group III]. In group IV, no retrofillings were made and no nail polish was applied. The specimens were suspended in 2% methylene blue dye for 7 days. The teeth were sectioned longitudinally and the depth of linear dye penetration was measured. The results demonstrated that group II significantly had the least microleakage of all [P < 0.05]. It was concluded that chemically activated resin-glass ionomer should be considered as an alternative retrofilling material