Abstract
Biomechanics play a critical role in influencing the clinical applications of all-ceramic dental restorations. The restorative biomaterials have to demonstrate mechanical durability in the oral environment because they are always exposed to a variety of oral environments. This study was designed to evaluate the effect of soaking time, notch and saliva pH values on the impact energy of three commonly used all-ceramic materials for CAD/CAM. The leucite-reinforced glass ceramic (ProCAD), lithium disilicate glass ceramic (IPS e.max CAD) and zirconia-based ceramic materials (IPS e.max ZirCAD) were used. The experimental results indicated that the impact energy of ProCAD decreased with an increase in soaking time, but not for IPS e.max CAD and IPS e.max ZirCAD. The impact energy of the zirconia system was higher than leucite-reinforced and lithium disilicate-based ceramic systems. When subjected to preformed 0.5 mm U-shape notch on the bar specimen of 3 mm thick, the impact energy of the all-ceramic restorations revealed a markedly reduction of about 80%–90%, almost irrespective of dental compositions, which indicated the effect of flaw to a great degree. No statistically significant influence (p > 0.05) of pH values (4, 7 and 9) on impact energy was found for each group. It is concluded that the no matter which all-ceramic materials were used, it was appreciably sensitive to the presence of notches. The ceramic composition and microstructure have been shown to affect mechanical durability.
Highlights
All-ceramic restorations have been used in dentistry due to their unique properties, such as a very translucent and natural appearance, high resistance to wear and distortion, chemical stability, thermal stability and excellent biocompatibility [1,2,3]
All-ceramic materials have a high strength and fracture toughness, the dental clinical researches have reported that the main reason for failure originates from the restoration fracture, such as veneering porcelain, ceramic coping, and the connector for fixed partial denture prosthesis (FPDPs) [7,8,9,10]
The effect of soaking time periods on the variations in the impact energy demonstrated no significant differences (p > 0.05) for either control specimens or notched specimens. We found this to be the case for IPS e.max ZirCAD (Figure 5), the impact energy had the highest values among the three all-ceramic specimens under the same experiment conditions
Summary
All-ceramic restorations have been used in dentistry due to their unique properties, such as a very translucent and natural appearance, high resistance to wear and distortion, chemical stability, thermal stability and excellent biocompatibility [1,2,3]. The dental restorations have been used for numerous clinical applications, including inlays, crowns, veneers, three- and four-unit bridges, and implants [2,3,4,5]. All-ceramic materials have a high strength and fracture toughness, the dental clinical researches have reported that the main reason for failure originates from the restoration fracture, such as veneering porcelain, ceramic coping, and the connector for fixed partial denture prosthesis (FPDPs) [7,8,9,10]. The flaws may be the predominant cause for reduction of mechanical strength and lifetime. The effect of the existed damage or flaws on mechanical properties is worth evaluating from the viewpoint of clinical investigation
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