title: Evaluation of stresses developed in different bracket-cement-enamel systems using finite element analysis with in vitro bond strength tests.
abstract: BACKGROUND
  The purpose of this study was to determine the bond strength of different orthodontic bracket materials (ceramic, stainless steel, and titanium) as well as stresses developed in bracket-cement-enamel systems using finite element (FE) analysis.
  
  
  METHODS
  One hundred and thirty-five extracted human caries-free upper central incisors were divided into three groups (n = 45/group) according to the type of orthodontic bracket materials (stainless steel, ceramic, and titanium). Each group was further subdivided into three subgroups (n = 15/group) according to the bond strength test loading mode (shear short side, shear long side, and tensile). After debonding, the fractured specimen was examined, and the adhesive remnant index (ARI) was determined. FE analysis models analyzed the stress distribution within the cement and enamel. Bond strengths were analyzed using ANOVA and Tukey's test, and the ARI scores were analyzed using chi-square (χ2) test.
  
  
  RESULTS
  Shear loading at the short side of the bracket resulted in the highest bond strength and lowest maximum principal stress both on cement and enamel compared with the other loading modes (P < 0.05). Ceramic brackets presented with higher bond strength and lower maximum principal stress than metallic brackets (P < 0.05). There was a significant difference for ARI scores between the type of brackets (χ2 = 64.852, P < 0.001).
  
  
  CONCLUSIONS
  The findings suggest that the manner of loading orthodontic brackets and the selection of orthodontic bracket materials affect the bond strength and stresses developed both on cement and enamel.
authors.affiliation: Department of Dental Biomaterials, Faculty of Dentistry, Mansoura University, Mansoura 35516, Egypt. shaymanaghy@mans.edu.eg.
authors.forename: Shaymaa E
authors.initials: SE
authors.lastname: Elsaka
authors.forename: Shaza M
authors.initials: SM
authors.lastname: Hammad
authors.forename: Noha F
authors.initials: NF
authors.lastname: Ibrahim
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000268:Adhesiveness; D002516:Ceramics / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D001840:Dental Bonding; D003738:Dental Cements / Q000737:chemistry*; D003743:Dental Enamel / Q000648:ultrastructure*; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D020342:Finite Element Analysis; D006801:Humans; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D019279:Resin Cements / Q000737:chemistry; D033081:Shear Strength; D013193:Stainless Steel / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength; D014025:Titanium / Q000737:chemistry
chemical_list: D003188:Composite Resins; D003738:Dental Cements; D003764:Dental Materials; D019279:Resin Cements; C477790:Transbond XT; C516047:Transbond XT Light Cure Adhesive Primer; D013193:Stainless Steel; D014025:Titanium