Flexural strength of a polymethylmethacrylate resin produced by computer-aided design and computer-aided manufacturing system after repeated usage of tungsten carbide burs and thermocyclingBiegefestigkeit eines mit Hilfe von computergestütztem Design und computergestütztem Fertigungssystem hergestellten Polymethylmethacrylat-Harzes nach wiederholter Verwendung von Wolframkarbidfräsern und Thermocycling

Abstract

The purpose of this study was to examine how new and used burs affected the flexural strength of a polymethylmethacrylate resin produced by computer-aided design and computer-aided manufacturing system following thermocycling. A total of 40 rectangular-shaped specimens (14 mmx4 mmx1.2 mm) for flexural strength test were fabricated from one brand of a polymethylmethacrylate resin produced by computer-aided design and computer-aided manufacturing system. Half of the specimens (Group N) were milled using the new tungsten carbide bur set, while the other half (Group U) was milled using the used (250 machining time) tungsten carbide bur set. The specimens were subjected to flexural strength test before and after thermocycling. The One way Analysis of Variance and Duncan tests were used for statistical analysis. Group N had the highest mean flexural strength values, while Group NT (specimens milled with the new bur/before thermal cycling) had the lowest mean flexural strength values. New and used burs have an effect on the flexural strength of a polymethylmethacrylate resin specimens produced by computer-aided design and computer-aided manufacturing system. Thermocycling process have an effect on the flexural strength values of specimens milled with the new tungsten carbide bur. Long-term interim dental restorations produced by computer-aided design and computer-aided manufacturing system must meet certain clinical requirements such as strength. Differences in the characteristics of milling burs, notably those associated to their repeated use, may have a considerable impact on the flexural strength and clinical success of restorations produced by this system.image