Measuring bond strength between fiber post and root dentin: a comparison of different tests.
OBJECTIVE
the aim of this study was to evaluate the ability of bond strength tests to accurately measure the bond strength of fiber posts luted into root canals.


METHODS
the test methods studied were hourglass microtensile (HM), push-out (PS), modified pushout (MP), and pull-out (PL). The evaluated parameters were: bond strength values, reliability (using Weibull analysis), failure mode (using confocal microscopy), and stress distribution (using finite element analysis). Forty human intact single-rooted and endodontically treated teeth were divided into four groups. Each group was assigned one of the test methods. The samples in the HM and PS groups were 1.0 ± 0.1 mm thick; the HM samples were hourglass shaped and the PS samples were disk shaped. For the PL and MP groups, each 1-mm dentin slice was luted with a fiber post piece. Three-dimensional models of each group were made and stress was analyzed based on Von Mises criteria.


RESULTS
PL provided the highest values of bond strength, followed by MP, both of which also had greater amounts of adhesive failures. PS showed the highest frequency of cohesive failures. MP showed a more homogeneous stress distribution and a higher Weibull modulus.


CONCLUSIONS
the specimen design directly influences the biomechanical behavior of bond strength tests.
Department of Biomaterials and Oral Biochemistry, Dental School, University of Sao Paulo, São Paulo, SP, Brazil. carina@usp.br
Carina Strano
CS
Castellan
Paulo César
PC
Santos-Filho
Paulo Vinicius
PV
Soares
Carlos José
CJ
Soares
Paulo Eduardo
PE
Cardoso
D000134:Acid Etching, Dental / Q000379:methods; D000268:Adhesiveness; D002484:Cementation / Q000379:methods; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000648:ultrastructure*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000592:standards* / Q000706:statistics & numerical data; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D020342:Finite Element Analysis; D005898:Glass / Q000737:chemistry*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008422:Materials Testing; D018613:Microscopy, Confocal; D010756:Phosphoric Acids / Q000737:chemistry; D011176:Post and Core Technique / Q000295:instrumentation*; D015203:Reproducibility of Results; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013718:Tensile Strength; D019246:Tooth Preparation / Q000379:methods; D019553:Tooth, Nonvital / Q000628:therapy
D003764:Dental Materials; D017220:Dentin-Bonding Agents; D010756:Phosphoric Acids; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; C009753:fiberglass; C103502:Variolink; C030242:phosphoric acid