[Effect of prism length on the notchless triangular prism fracture toughness test].
OBJECTIVE
The purpose of this study was to clarify the effect of holding condition with different prism length on the Notchless Triangular Prism (NTP) fracture toughness test and to define the prism length as a measuring condition.


METHODS
Two kinds of NTP prism (ceramic and composite resin) were fabricated by CAD/CAM and each prism was adjusted to one of three lengths (8.0 mm, 12.0 mm, 16.0 mm). NTP was conducted for prism specimens made under six different conditions. The displacement of prism specimen holder gap (Delta d) and maximum fracture load (Pmax) were recorded and then a fractogram of each prism was inspected by SEM.


RESULTS
Inclined stable fracture propagation was observed on the fractogram of the 8.0-mm prism. Both Delta d and Pmax of the 8.0-mm prism were significantly higher than those of the other lengths.


CONCLUSIONS
A prism length of at least 12.0 mm is needed for the NTP because the 8.0-mm prism did not have a sufficient holding condition. The fracture toughness of the ceramic (3.68+/-0.09 MPa.m(1/2)) was significantly higher than that of the composite resin (2.38+/-0.20 MPa.m(1/2)).
Takamura
Miyuki
M
Department of Crown and Bridge, The Nippon Dental University School of Dentistry at Niigata, 951-8580 Niigata.
Akiike
Shigenori
S
Komatsu
Shigeki
S
Hata
Yoshiaki
Y
D002516:Ceramics / Q000592:standards*; D003188:Composite Resins / Q000592:standards*; D006245:Hardness Tests; D013314:Stress, Mechanical
D003188:Composite Resins