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Microtensile Specimen Attachment and Shape—Finite Element Analysis

¹ Biomechanics group, School of Dentistry, Federal University of Uberlândia, Av. Pará 1720, Bloco 2B, sala 2B24, 38400-902, Uberlândia, MG, Brazil; and
² Department of Operative Dentistry, College of Dentistry, University of Iowa, Iowa City, USA

^* corresponding author, carlosjsoares{at}umuarama.ufu.br

Microtensile bond strength values are influenced by specimen shape and attachment method to the gripping device during testing. We hypothesized that stress distribution inside the testing specimen is affected by microtensile specimen shape and attachment method. Rectangular, hourglass-, and dumbbell-shaped specimens, all with a 1 mm² cross-sectional testing region, were modeled as indirect ceramic restorations luted to dentin. Three specimen attachments were investigated: (1) posterior surface; (2) posterior, superior, and lateral surfaces; and (3) all surfaces. Qualitative and quantitative analyses were carried out according to von Mises’ criteria. Stress analysis showed a direct correlation between attachment modes and stress distribution, with shear stresses observed in models with less surface attachment. Increasing the number of faces for specimen attachment to the metallic gripping device resulted in a more homogeneous and regular distribution of stress, with tensile stress concentrated at the adhesive interface. Dumbbell-shaped specimens showed improved stress distribution compared with rectangular and hourglass-shaped specimens.

KEY WORDS: finite element analysis • microtensile testing • stress distribution