The effect of mechanical and thermal cycling of ultra-high molecular weight polyethylene [UHMWPE] fibres on the flexural strength and fracture resistance of indirect dental composite was investigated.
The UHMWPE fibres are increasingly being used for the reinforcement of laboratory fabricated resin composite crown and bridgework. The aim of this study was to assess the effect of mechanical and thermal cycling commonly occurring intraorally on the in vitro strength of beam shaped specimen simulating a three-unit fixed bridge. Six groups [15 specimens per group] of Artglass dental composite were prepared for flexural strength testing after reinforcement with UHMWPE fibres. All test groups were stored in distilled water for 24 hours at 37¬∞C between fabrication and testing. Before flexural testing [within the same 24 hours period of storage], four groups were exposed to a mechanical cycling regime [each cycle consists of minimum load 20 N, and maximum load 90 N, frequency 1.9 hertz / dry at room temperature] ranged from 500, 1.000, 2.000 and 5.000 cycles. The remaining two groups were exposed to thermal cycling. The specimens were thermal-cycled as follows: the temperature baths were 6¬∞C and 65¬∞C with a dwell time of 13 seconds at each temperature and a transfer time of 10 seconds. The specimens were tested in flexion at a cross-head speed of 1 mm / minute using a universal testing machine [Instron]. Means and standard deviations of flexural strength MPa were calculated. Data were analysed by one-way analysis of variance followed by post hoc companion Tukey tests [P < 0.05]. ANOVA test showed that there is no significant difference between all the tested groups [P>0.05]. However othere is a trend for thermal [3.000 cycles] with mechanical cycling [5.000 cycles] to reduce the flexural strength. SEM examination showed proper bonding between the fibre and the overlying composite
Khalid Al Abidi ,
Influence of mechanical and thermal cycling on the flexural strength of fibre reinforced indirect dental composite,
Egypt. Dent. J. 2006;
1875-1879 Views : 0