Effect of Thermocycling on Flexural Strength and Weibull Statistics of Machinable Glass–Ceramic and Composite Resin

Abstract

To evaluate the durability of machinable dental restorative materials, this study performed an experiment to evaluate the flexural strength and Weibull statistics of a machinable lithium disilicate glass-ceramic and a machinable composite resin after being thermocycled for certain cycles. A total of 40 bar-shape specimens of were prepared with the dimension of 20 mm × 4 mm × 2 mm, which were divided into four groups of 10 specimens. Ten specimens of machinable lithium disilicate glass-ceramic (IPS e.max CAD, Ivoclar Vivadent, Liechtenstein) and 10 specimens of machinable composite resin (Paradigm MZ 100, 3M ESPE, USA) were subjected to 3-point flexural strength test. Other 10 specimens of each material were thermocycled between water temperature of 5 and 55 °C for 10,000 cycles. After that, they were tested using 3-point flexural strength test. Statistical analysis was performed using two-way analysis of variance and Tukey multiple comparisons. Weibull analysis was performed to evaluate the reliability of the strength. Means of strength and their standard deviation were: thermocycled IPS e.max CAD 389.10 (50.75), non-thermocycled IPS e.max CAD 349.96 (38.34), thermocycled Paradigm MZ 100 157.51 (12.85), non-thermocycled Paradigm MZ 100 153.33 (19.97). Within each material group, there was no significant difference in flexural strength between thermocycled and non-thermocycled specimens. Considering the Weibull analysis, there was no statistical difference of Weibull modulus in all experimental groups. Within the limitation of this study, the results showed that there was no significant effect of themocycling on flexural strength and Weibull modulus of a machinable glass-ceramic and a machinable composite resin.

A Comparative Study on the Mechanical Properties of a Polymer-Infiltrated Ceramic-Network Material Used for the Fabrication of Hybrid Abutment

“…In the present study, thermocycling did not cause significant decrease in the flexural-strength values of the LDS and PICN specimens. This finding was in agreement with previous studies that reported that LDS [ 25 ] and PICN are not influenced by thermocycling [ 26 , 27 ]. Thermal cycling or storing resin-based materials in water were reported to cause polymer softening due to water penetrating the resin matrix [ 28 ].…”

Influence of Storage Condition on Flexure Properties of Nano-Composite

“…However, these results were in agreement with another investigation in which prolonged water storage influenced flexure strength of some tested materials and did not influence the flexure modulus of all tested composite materials and another investigation was confirming the present results in which thermo-cycling did not influence flexure properties of nano-filled composite [17,30].…”

“…However, in literatures, there are variable techniques of sample storage before mechanical testing. Composite test samples may be stored at room temperature, body temperature, or thermo-cycled to represent temperature variation in the oral cavity [7][8][9][10][11][12][13][14][15]17]. In addition, water was used as an aging solution in several studies to mimic the wet environment in the oral cavity [4,[18][19][20].…”

Effect of Food Simulating Liquids and Thermo-cycling on flexural strength and surface hardness of a Resin Nano-Ceramic CAD/CAM Material

“…Moreover, many authors (18)(19)(20)(21)(22) noticed a decrease in the surface micro-hardness of composite resins after immersion of food simulating liquids. This is related to the susceptibility of polymeric matrix to sorption of different liquids.…”