Evaluation of fracture resistance and color stability of crowns obtained by layering composite over zirconia and polyetheretherketone copings before and after thermocycling to simulate oral environment: An in vitro study

Abstract

A BSTRACT Background: Most common material used for the fabrication of an implant restoration is full-ceramic crown or an all-ceramic crown. Frequent chipping of the ceramic under occlusal load has posed a great problem to the clinician and the patient. Composites have been layered over zirconia successfully in the recent past to overcome this problem. This study, thus, aimed to evaluate and compare the fracture resistance and color stability of crowns obtained by layering composite over zirconia and polyetheretherketone (PEEK) copings before and after thermocycling to simulate oral environment. Materials and Methods: A total of 40 crowns (20 per group) were obtained by layering composite of A3 shade over computer-aided design/computer-aided milling milled zirconia and PEEK copings. Thermocycling of the 10 out of the 20 crowns was performed in a thermocycler (5000 cycles, in water temperature of 5°C and 55°C with dwell time of 30s), and then they were kept in hot and cold beverages for 24h each, to simulate oral environmental conditions. After thermocycling, the crowns were divided into four groups of 10 samples each: Group Z, ZT, P, and PT. Shade evaluation of all the crowns was performed using digital shade guide (VITA Easyshade ® Advance; VITA Zahnfabrik, Bad Säckingen, Germany) and VITAPAN classical (VITA Zahnfabrik). Fracture strength was tested for all the crowns in a universal testing machine. Fracture strength in megapascal and the applied occlusal load in kilograms were recorded. Data obtained were statistically evaluated by one-way analysis of variance and post hoc test. Results: The final shade of the crowns obtained by layering A3 shade composite in the groups Z was A3, ZT was B3, P was C3, and PT was D2. The value of mean fracture strength of crowns of groups Z was 1142.3MPa, ZT was 1034.57MPa, P was 2134.64MPa, and PT was 1765.01MPa. Conclusion: Thermocycling affected the shade of all the crowns. The mean fracture strength of the crowns having PEEK copings was significantly higher than that of zirconia copings. Thermocycling did not have a significant effect on the mean fracture strength.

An Invitro Chewing Simulation Study Comparing the Wear Resistance Behavior of Polyetheretherketone-Layered Composite Crown and Ceramic-Layered Zirconia Crown

“…To evaluate the color stability of restorative material in simulation with an oral environment, a study was conducted on zirconia and PEEK copings veneered with an indirect composite under thermocycle and concluded that shades of the crowns have been affected by thermocycling, which is not in correlation with our study [7]. Various studies were conducted on the color stability of feldspathic porcelain and zirconia under different exposures of oral simulations and proved that these effects were higher on natural teeth and zirconia with feldspathic porcelain as least affected [11,12].…”

“…The Zirconia (CaroZiir S, UK) was then sintered at 1450°C for 60 minutes. The Zirconia copings were layered with feldspathic porcelain (Ivoclar Emax, Ivoclar Vivaden, US), and PEEK crowns were layered with indirect composite (Bredent), which were then polished with polishing paste and rubber wheel according to the manufacturer's protocol [6,7]. A putty template was taken before the tooth preparations, and the same template was used to veneer porcelain and indirect composite over the samples to eliminate any bias toward the thickness of the veneer and maintenance of its natural anatomy.…”

Qualitative SEM analysis of fracture surfaces for dental ceramics and polymers broken by flexural strength testing and crown compression

“…We understand that the clinical indications of PEK and PEEK materials used presently are very limited-they can be applied clinically as a core design and must be covered by composite resin for esthetic reasons. 36 The purpose of the present study was not to simulate the clinical oral environment, as the CTC test does not consistently result in clinically observed failures. The values for the flexural strength and fracture loads for the bar and disc specimens used presently were published elsewhere, with the current focus being qualitative assessment of fracture surfaces.…”

“…The crowns were not exposed to artificial aging (thermocycling) to make the study more clinically relevant and to be consistent with the bar specimens, for which thermocycling is not recommended by the ISO standard for testing flexural strength. We understand that the clinical indications of PEK and PEEK materials used presently are very limited—they can be applied clinically as a core design and must be covered by composite resin for esthetic reasons 36 . The purpose of the present study was not to simulate the clinical oral environment, as the CTC test does not consistently result in clinically observed failures.…”

Relation of Crown Failure Load to Flexural Strength for Three Contemporary Dental Polymers

“…PEEK is manufactured through computer-aided design and computer-aided manufacturing (CAD/CAM) technology, while PEKK may also be heat-pressed [9]. PEEK was initially applied to frameworks for fixed partial dentures [10][11][12] and removable partial dentures [13], implant abutments [14,15], surgical membranes [16], post cores [17], and implant bodies [18].…”