title: Effect of hybrid layer and thickness on stress distribution of cervical wedge-shaped restorations.
abstract: OBJECTIVE
  The aim of this finite elemental stress analysis study was to evaluate the effect of a hybrid layer and the hybrid layer thickness on the shear stress distribution in mandibular premolar teeth under occlusal loading.
  
  
  METHODS
  The mandibular premolar tooth was selected based on the anatomical measurements suggested by Wheeler. The analysis was performed with a computer with the SAP 2000 structural analysis program. Three different mathematical models were evaluated; 1) composite restoration without a hybrid layer 2) composite restoration with a 1.5 mum thick hybrid layer and 3) composite restoration with a 3 mum thick hybrid layer. A total of 200 N of occlusal loading force was simulated from the buccal tubercule and central fossa of the premolar tooth. The findings were drawn by the Saplot program.
  
  
  RESULTS
  In model B, the output showed that hybrid layer reduced the shear stress concentration especially on gingival margin of the composite. Similarly shear stress intensity was decreased by a thick hybrid layer in model C, especially on the gingival margin of the composite.
  
  
  CONCLUSIONS
  The hybrid layer and its thickness plays an important role on stress distribution and intensity in cervical restorations.
authors.affiliation: DDS, PhD, Assistant Professor, Department of Operative Dentistry and Endodontics, School of Dentistry, University of Yuzuncuyil, Van, Turkey.
authors.forename: Evrim
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authors.lastname: Eliguzeloglu
authors.forename: Oguz
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authors.lastname: Eraslan
authors.forename: Huma
authors.initials: H
authors.lastname: Omurlu
authors.forename: Gurcan
authors.initials: G
authors.lastname: Eskitascıoglu
authors.forename: Sema
authors.initials: S
authors.lastname: Belli
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