Fracture toughness of cross-linked and non-cross-linked temporary crown and fixed partial denture materials.
OBJECTIVE
Temporary crowns and fixed partial dentures are exposed to considerable functional loading, which places severe demands on the biomaterials used for their fabrication (= temporary crown & bridge materials, t-c&b). As the longevity of biopolymers is influenced by the ability to withstand a crack propagation, the aim of this study was to investigate the fracture toughness of cross-linked and non-cross-linked t-c&bs.


METHODS
Four different t-c&bs (Luxatemp AM Plus, Protemp 3 Garant, Structur Premium, Trim) were used to fabricate bar shaped specimens (2mmx5mmx25mm, ISO 13586). A notch (depth 2.47mm) was placed in the center of the specimen using a diamond cutting disc and a sharp pre-crack was added using a razor blade. 60 specimens per material were subjected to different storage conditions (dry and water 37 degrees C: 30min, 60min, 4h, 24h, 168h; thermocycling 5-55 degrees C: 168h) prior to fracture (3-point bending setup). The fracture sites were inspected using SEM analysis. Data was subjected to parametric statistics (p=0.05).


RESULTS
The K(IC) values varied between 0.4 and 1.3MPam(0.5) depending on the material and storage time. Highest K(IC) were observed for Protemp 3 Garant. Fracture toughness was significantly affected by thermocycling for all dimethacrylates (p<0.05) except for Structur Premium. All dimethacrylates showed a linear-elastic fracture mechanism, whereas the monomethacrylate showed an elasto-plastic fracture mechanism.


CONCLUSIONS
Dimethacrylates exhibit a low resistance against crack propagation immediately after curing. In contrast, monomethacrylates may compensate for crack propagation due to plastic deformation. However, K(IC) is compromised with increasing storage time.
Balkenhol
Markus
M
Department of Prosthetic Dentistry, Justus-Liebig-University, Schlangenzahl 14, D-35392 Giessen, Germany. markus.balkenhol@dentist.med.uni-giessen.de
Köhler
Heiko
H
Orbach
Katharina
K
Wöstmann
Bernd
B
D000180:Acrylic Resins / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry; D003442:Crowns; D003764:Dental Materials / Q000737:chemistry*; D003794:Dental Restoration, Temporary; D003830:Denture, Partial, Fixed; D003833:Denture, Partial, Temporary; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D011109:Polymethacrylic Acids / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
D000180:Acrylic Resins; D003188:Composite Resins; D003432:Cross-Linking Reagents; D003764:Dental Materials; D008689:Methacrylates; D011109:Polymethacrylic Acids; C098586:luxatemp; D014867:Water; C091347:vinyl ethyl methacrylate; D017438:Bisphenol A-Glycidyl Methacrylate; C069714:Protemp