title: The effects of dentin bonding agent formulas on their polymerization quality, and together with tooth tissues on their microleakage and shear bond strength: an explorative 3-step experiment.
abstract: OBJECTIVE
  Bonding agents (BA) are the crucial weak link of composite restorations. Since the commercial materials' compositions are not disclosed, studies to formulize the optimum ratios of different components are of value. The aim of this study was to find a proper formula of BAs.
  
  
  METHODS
  This explorative experimental in vitro study was composed of 4 different sets of extensive experiments. A commercial BA and 7 experimental formulas were compared in terms of degree of conversion (5 experimental formulas), shear bond strength, mode of failure, and microleakage (3 experimental formulas). Statistical analyses were performed (α=.05). The DC of selected formula was tested one year later.
  
  
  RESULTS
  The two-way ANOVA indicated a significant difference between the shear bond strength (SBS) of two tissues (dentin vs. enamel, P=.0001) in a way that dentinal bonds were weaker. However, there was no difference between the four materials (P=.283). The adhesive mode of failure was predominant in all groups. No differences between the microleakage of the four materials at occlusal (P=.788) or gingival (P=.508) sites were detected (Kruskal-Wallis). The Mann-Whitney U test showed a significant difference between the microleakage of all materials (3 experimental formulas and a commercial material) together at the occlusal site versus the gingival site (P=.041).
  
  
  CONCLUSIONS
  A formula with 62% bisphenol A-glycidyl methacrylate (Bis-GMA), 37% hydroxy ethyl methacrylate (HEMA), 0.3% camphorquinone (CQ), and 0.7% dimethyl-para-toluidine (DMPT) seems a proper formula for mass production. The microleakage and SBS might be respectively higher and lower on dentin compared to enamel.
authors.affiliation: Department of Pharmaceutics, School of Pharmacy, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mohmmad
authors.initials: M
authors.lastname: Erfan
authors.affiliation: Iranian Tissue Bank and Research Center, Department of Dental Materials, Faculty of Dentistry, Research Center for Sciences and Technology in Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Tahereh Sadat
authors.initials: TS
authors.lastname: Jafarzadeh-Kashi
authors.affiliation: Pharmacist in private practice, Tehran, Iran.
authors.forename: Malihe
authors.initials: M
authors.lastname: Ghadiri
authors.affiliation: Iranian Tissue Bank and Research Center, Tehran University of Medical Sciences, Tehran, Iran. ; Department of Dental Anatomy and Morphology, Dental Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Rakhshan
keywords: Degree of conversion; Dentin bonding agents; FT-IR spectroscopy; H-NMR spectroscopy; Microleakage; Mode of failure; Polymerization; Shear bond strength