Fracture strength of all-ceramic posterior inlay-retained fixed partial dentures.
OBJECTIVE
The purpose of this in vitro study was to compare the quasi-static (QSFS) and fatigue fracture strength of all-ceramic resin-bonded three unit inlay-retained fixed partial dentures (IRFPDs) made from a heat-pressed lithium-disilicate based glass-ceramic (LDGC) and a CAD/CAM-manufactured yttrium-oxide partially stabilized zirconia framework (YPSZ).


METHODS
Identical IRFPD-models of the maxilla were used. They consisted of a second premolar, a missing first molar and a second molar (Co-Cr-Mo alloy) integrated in a low melting alloy base. Roots were covered with a soft silicone-layer to simulate an artificial parodontium. Premolars had an occlusal-distal inlay-preparation and molars a mesial-occlusal inlay-preparation. Thirty-two IRFPDs were made from each ceramic using two different connector dimensions: 3mmx3mm (LDGC_9, YPSZ_9); 4mmx4mm (LDGC_16, YPSZ_16). All IRFPDs were cemented adhesively to the IRFPD-models, using composite resin cement. QSFS was tested in a universal-testing-machine (UTM) for six specimens. The other specimens were fatigued either with cyclic loading at 250N (n=4) in a chewing simulator or at 600N (n=6) using the UTM, and group YPSZ additionally at 1500N.


RESULTS
The medians of QSFS (N) were 960 (LDGC_9), 1316 (LDGC_16), 3180 (YPSZ_9) and 3120 (YPSZ_16). For both QSFS and cyclic loading significant differences were found between LDGC_9 and LDGC_16 (p</=0.03) but not between YPSZ_9 and YPSZ_16 (p>0.05). Differences between LDGC and YPSZ were significant for both connector sizes (p</=0.001).


CONCLUSIONS
Considering the maximum chewing forces in the molar region it seems clinically possible, to use YPSZ as a core material for IRFPDs with a connector size between 9 and 16mm(2).
Wolfart
Stefan
S
Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University at Kiel, Arnold-Heller-Str. 16, 24105 Kiel, Germany. swolfart@proth.uni-kiel.de
Ludwig
Klaus
K
Uphaus
Anja
A
Kern
Matthias
M
D001732:Bite Force; D002516:Ceramics; D017076:Computer-Aided Design; D003776:Dental Porcelain / Q000737:chemistry; D003799:Dental Stress Analysis; D003779:Denture Design; D003781:Denture Retention; D003830:Denture, Partial, Fixed; D007284:Inlays; D018020:Lithium Compounds; D008422:Materials Testing; D003765:Models, Dental; D008963:Molar; D019279:Resin Cements; D015019:Yttrium; D015040:Zirconium
D018020:Lithium Compounds; D019279:Resin Cements; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; D015019:Yttrium; C023506:Glass ceramics; D015040:Zirconium