title: Influence of voids in the hybrid layer based on self-etching adhesive systems: a 3-D FE analysis.
abstract: The presence of porosities at the dentin/adhesive interface has been observed with the use of new generation dentin bonding systems. These porosities tend to contradict the concept that etching and hybridization processes occur equally and simultaneously. Therefore, the aim of this study was to evaluate the micromechanical behavior of the hybrid layer (HL) with voids based on a self-etching adhesive system using 3-D finite element (FE) analysis.
  
  
  METHODS
  Three FE models (Mr) were built: Mr, dentin specimen (41x41x82 μm) with a regular and perfect (i.e. pore-free) HL based on a self-etching adhesive system, restored with composite resin; Mp, similar to M, but containing 25% (v/v) voids in the HL; Mpp, similar to Mr, but containing 50% (v/v) voids in the HL. A tensile load (0.03N) was applied on top of the composite resin. The stress field was obtained by using Ansys Workbench 10.0. The nodes of the base of the specimen were constrained in the x, y and z axes. The maximum principal stress (σmax) was obtained for all structures at the dentin/adhesive interface.
  
  
  RESULTS
  The Mpp showed the highest peak of σmax in the HL (32.2 MPa), followed by Mp (30 MPa) and Mr (28.4 MPa). The stress concentration in the peritubular dentin was high in all models (120 MPa). All other structures positioned far from voids showed similar increase of stress.
  
  
  CONCLUSIONS
  Voids incorporated into the HL raised the σmax in this region by 13.5%. This behavior might be responsible for lower bond strengths of self-etching and single-bottle adhesives, as reported in the literature.
authors.affiliation: Dental School of Araçatuba, UNESP, SP, Brazil.
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Martini
authors.forename: Rodolfo Bruniera
authors.initials: RB
authors.lastname: Anchieta
authors.forename: Eduardo Passos
authors.initials: EP
authors.lastname: Rocha
authors.forename: Amilcar Chagas
authors.initials: AC
authors.lastname: Freitas Junior
authors.forename: Erika Oliveira de
authors.initials: EO
authors.lastname: Almeida
authors.forename: Renato Herman
authors.initials: RH
authors.lastname: Sundfeld
authors.forename: Marco Antonio
authors.initials: MA
authors.lastname: Luersen
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods*; D045662:Dental Etching; D003799:Dental Stress Analysis; D003804:Dentin / Q000737:chemistry* / Q000648:ultrastructure; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D003188:Composite Resins; D017220:Dentin-Bonding Agents