Optimum post and tooth root diameters for a cast post-core system.
OBJECTIVE
To investigate the optimum diameter for the tapered post of a cast alloy post-core system relative to the root diameter, when measured at the root face, that is required to minimize both post and root failures.


METHODS
32 extracted maxillary central incisor teeth were each decoronated perpendicular to the long axis at a point 2.0 mm occlusal to the labial cemento-enamel junction. Following endodontic canal obturation, the teeth were assigned randomly to four equal groups for different diameter tapered post space preparations. Then 1.10, 1.50, 1.70, and 2.00 mm diameter cast Ni-Cr alloy post-cores and complete crowns without ferrules were fabricated. Each root was embedded in a large gypsum stone block and the crown loaded palatally at 135 degrees from the long axis in a universal testing machine at a crosshead speed of 1.0 mm/minute until failure. Results were analyzed using one-way ANOVA with Tukey-Kramer post hoc tests, and Fisher's exact test, with alpha = 0.05 for statistical significance.


RESULTS
Mean failure resistance loads were: 0.60, 0.91, 1.00, and 1.38 kN (P < 0.001). All of the 1.10 mm posts failed, without any root fractures. Conversely, none of the 2.00 mm posts failed, but all of the roots fractured. The optimum post to root diameter ratio to minimize failures was approximately 1:4.
Mou
Yong-Bin
YB
Dental Research Institute, Nanjing Medical University, Nanjing, PR China.
Chen
Ya-Ming
YM
Smales
Roger J
RJ
Yip
Kevin H K
KH
D000368:Aged; D002858:Chromium Alloys / Q000737:chemistry; D003442:Crowns; D003734:Dental Casting Investment / Q000737:chemistry; D017267:Dental Prosthesis Design; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000033:anatomy & histology; D006801:Humans; D008422:Materials Testing; D008875:Middle Aged; D009811:Odontometry; D011176:Post and Core Technique / Q000295:instrumentation*; D018915:Root Canal Preparation / Q000379:methods; D013314:Stress, Mechanical; D013499:Surface Properties; D014082:Tooth Fractures / Q000503:physiopathology; D014092:Tooth Root / Q000033:anatomy & histology / Q000293:injuries
D002858:Chromium Alloys; D003734:Dental Casting Investment