title: Comparison of in-vitro bond strengths between resin-modified glass ionomer, polyacid-modified composite resin, and giomer adhesive systems.
abstract: BACKGROUND
  The purpose of this in-vitro study was to compare the shear bond strength of orthodontic brackets bonded to tooth enamel with 4 adhesives: a commercially available giomer material, a polyacid-modified composite resin (PMCR), a resin-modified glass ionomer (RMGI), and a standard resin-based composite (RBC) adhesive.
  
  
  METHODS
  Eighty extracted human molars were collected and divided into 4 groups (n = 20). Two stainless steel premolar brackets were bonded to each tooth with 1 of the 4 adhesives, according to each manufacturers' instructions. One bracket was tested for shear bond strength at 1 hour and the other at 7 days. A shear force was applied to the bracket/tooth interface with a chisel-shaped rod attached to a universal testing machine at a crosshead speed of 0.5-mm per minute until bracket failure. The force in newtons was recorded. Debonded enamel surfaces were examined under a stereomicroscope to assess the amount of residual adhesive.
  
  
  RESULTS
  A 2-factor analysis of variance detected significant differences among adhesive types and time of load test. The Tukey HSD test determined that the RBC and the RMGI adhesives had significantly higher shear bond strength than the giomer and the PMCR materials at both 1 hour and 7 days. The chi-square test detected a significant difference in adhesive remnant index scores. The bracket/resin interface was the most common site of failure for all groups except the RMGI group.
  
  
  CONCLUSIONS
  RMGI orthodontic cement provides acceptable bond strength in vitro. Further clinical research is needed to validate this laboratory finding.
authors.affiliation: Tri-service Orthodontic Residency Program, Lackland AFB, San Antonio, Texas, USA.
authors.forename: Deepti
authors.initials: D
authors.lastname: Chitnis
authors.forename: William J
authors.initials: WJ
authors.lastname: Dunn
authors.forename: David A
authors.initials: DA
authors.lastname: Gonzales
mesh_terms: D000180:Acrylic Resins; D000538:Aluminum Silicates; D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate; D016009:Chi-Square Distribution; D020770:Compomers; D003188:Composite Resins; D001840:Dental Bonding; D003743:Dental Enamel; D003799:Dental Stress Analysis; D005899:Glass Ionomer Cements; D006801:Humans; D008422:Materials Testing; D008963:Molar; D016910:Orthodontic Brackets; D019279:Resin Cements; D033081:Shear Strength; D018709:Statistics, Nonparametric
chemical_list: D000180:Acrylic Resins; D000538:Aluminum Silicates; C508973:Beautifil FL-Bond; C470433:Beautifil composite resin; D020770:Compomers; D003188:Composite Resins; C088486:Dyract; C095451:Fuji Ortho LC; D005899:Glass Ionomer Cements; D019279:Resin Cements; C477790:Transbond XT; D017438:Bisphenol A-Glycidyl Methacrylate