In vitro evaluation of five core materials.
OBJECTIVE
This in vitro study determined the fracture strength of five core materials supported by two different endodontic dowels. Diametral tensile strength and microhardness of the three resin composite core materials used in this study were also tested.


METHODS
The fracture strength study used one lanthanide-reinforced flowable resin composite (Ti-Core Auto E), one titanium- and lanthanide-reinforced composite (Ti-Core), one lanthanide-reinforced composite (Ti-Core Natural), and two metal-reinforced glass ionomer core materials (Ketac Silver and GC Miracle Mix). Two types of dowels were used: a multitiered, split-shank threaded dowel with a flange (#1 Flexi-Flange) and one without a flange design (#1 Flexi-Post). The specimens were divided into ten groups. Each tooth/dowel and core specimen was placed in a special jig at 45 degrees and subjected to a load by a universal testing machine. The diametral tensile strength and the microhardness of the three resin composite core materials were measured by a universal testing machine and Barcol hardness tester, respectively. All test groups contained ten specimens.


RESULTS
The fracture strength value of the resin composite core materials was significantly larger ( p < 0.0001) than those for the metal-reinforced glass-ionomer core materials. Analysis of variance (ANOVA) also showed that the Flexi-Flange dowel interacted with Ti-Core and Ti-Core Auto E to significantly ( p < 0.0013) increase the fracture strength relative to the Flexi-Post. One-way ANOVA revealed that there were no significant differences between them in terms of diametral tensile strength. The Barcol hardness values of the composite core materials were statistically different ( p < 0.0001), with the Ti-Core the highest, followed by Ti-Core Natural, then Ti-Core Auto E.


CONCLUSIONS
Resin composite core material performed better than glass ionomer material in this in vitro study. The flowable composite core material performed about the same in terms of fracture strength and diametral tensile strength compared with nonflowable composites. Combined with certain core materials, the flange design increased the fracture strength of the tooth/dowel and core combination.
Gu
Steven
S
Essential Dental Labs, South Hackensack, NJ 07606, USA. sgu@edsdental.com
Rasimick
Brian J
BJ
Deutsch
Allan S
AS
Musikant
Barry L
BL
D016722:Cermet Cements / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003722:Dental Alloys / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D005899:Glass Ionomer Cements / Q000737:chemistry; D006244:Hardness; D006801:Humans; D028581:Lanthanoid Series Elements / Q000737:chemistry; D008422:Materials Testing; D011176:Post and Core Technique / Q000295:instrumentation*; D012834:Silver / Q000737:chemistry; D013314:Stress, Mechanical; D013718:Tensile Strength; D014025:Titanium / Q000737:chemistry; D014783:Viscosity
D016722:Cermet Cements; D003188:Composite Resins; D003722:Dental Alloys; D003764:Dental Materials; D005899:Glass Ionomer Cements; D028581:Lanthanoid Series Elements; C078801:Miracle Mix; C079578:Ti-Core composite resin; D012834:Silver; D014025:Titanium