In vitrostudy of fracture strength of provisional crown materials

Abstract

PURPOSEThe purpose of this report was to evaluate the effect of the fabrication method and material type on the fracture strength of provisional crowns.MATERIALS AND METHODSA master model with one crown (maxillary left second premolar) was manufactured from Cr-Co alloy. The master model was scanned, and the data set was transferred to a CAD/CAM unit (Yenamak D50, Yenadent Ltd, Istanbul, Turkey) for the Cercon Base group. For the other groups, temporary crowns were produced by direct fabrication methods (Imident, Temdent, Structur Premium, Takilon, Systemp c&b II, and Acrytemp). The specimens were subjected to water storage at 37℃ for 24 hours, and then they were thermocycled (TC, 5000×, 5-55℃) (n=10). The maximum force at fracture (Fmax) was measured in a universal test machine at 1 mm/min. Data was analyzed by non-parametric statistics (α=.05).RESULTSFmax values varied between 711.09-1392.1 N. In the PMMA groups, Takilon showed the lowest values (711.09 N), and Cercon Base showed the highest values (959.59 N). In the composite groups, Structur Premium showed the highest values (1392.1 N), and Acrytemp showed the lowest values (910.05 N). The composite groups showed significantly higher values than the PMMA groups (P=.01).CONCLUSIONComposite-based materials showed significantly higher fracture strengths than PMMA-based materials. The CAD-CAM technique offers more advantages than the direct technique.

Comparison of Flexural Strength of Different CAD/CAM PMMA‐Based Polymers

“…Therefore, direct comparison to other studies is not possible. The improved FS of CAD/CAM PMMA‐based polymers compared to bis‐acrylate and conventional PMMA found in this study are in agreement with previous studies . Karaokutan et al evaluated the fracture strength of seven interim crown materials after 5000 thermocycles.…”

“…Higher FS is essential for achieving clinical success with interim prostheses. Parallel with the results of the current study, in previous studies, bis‐acrylate composite resin had higher FS than conventional PMMA resins . Balkenhol et al evaluated the FS of different interim resins at different storage times after mixing, and reported that the FS of the materials are dependent on the storage time.…”

“…Ten thousand thermocycles were applied to the specimens to correspond to 1 year of physiological aging, and a dwell time of 30 seconds was selected to prevent extreme thermal stress . FS tests were used in the present study because of their proven advantages in evaluating the mechanical properties of materials . Although the FS test may not completely simulate the oral environment, it helps to compare materials under controlled conditions …”

“…Interim prostheses are an important part of fixed prosthodontic treatment and generally fabricated from conventional interim resin materials such as poly(methyl), poly(ethylene), and bis‐acrylate composite resins. These materials have different chemical structures, mechanical properties, and polymerization techniques …”

“…CAD/CAM PMMA‐based polymers have different mechanical properties depending on monomer and chemical composition and have a highly cross‐linked structure, which may offer advantages over conventionally polymerized interim resins . Structural properties of CAD/CAM PMMA‐based polymers may overcome the conventional resins’ well‐reported shortcomings such as low mechanical stability due to porosity, voids, and polymerization shrinkage that occur during mixing, packing, and setting . CAD/CAM PMMA‐based polymers may decrease residual monomer release, improve color stability and optical properties, and simplify the production of interim prostheses with easy machining .…”