title: Bonding of contemporary glass ionomer cements to different tooth substrates; microshear bond strength and scanning electron microscope study.
abstract: OBJECTIVE
  This study was conducted to evaluate the microshear bond strength (μSBS) and ultramorphological characterization of glass ionomer (GI) cements; conventional GI cement (Fuji IX, CGI), resin modified GI (Fuji II LC, RMGI) and nano-ionomer (Ketac N100, NI) to enamel, dentin and cementum substrates.
  
  
  METHODS
  Forty-five lower molars were sectioned above the cemento-enamel junction. The occlusal surfaces were ground flat to obtain enamel and dentin substrates, meanwhile the cervical one-third of the root portion were utilized to evaluate the bonding efficacy to cementum substrate. Each substrate received microcylinders from the three tested materials; which were applied according to manufacturer instructions. μSBS was assessed using a universal testing machine. The data were analyzed using two-way analysis of variance (ANOVA) and Tukey's post-hoc test. Modes of failure were examined using stereomicroscope at ×25 magnification. Interfacial analysis of the bonded specimens was carried out using environmental field emission scanning electron microscope.
  
  
  RESULTS
  Two-way ANOVA revealed that materials, substrates and their interaction had a statistically significant effect on the mean μSBS values at P values; ˂0.0001, 0.0108 and 0.0037 respectively. RMGI showed statistically significant the highest μSBS values to all examined tooth substrates. CGI and RMGI show substrate independent bonding efficiency, meanwhile; NI showed higher μSBS values to dentin and cementum compared to enamel.
  
  
  CONCLUSIONS
  Despite technological development of GI materials, mainly the nano-particles use, better results have not been achieved for both investigations, when compared to RMGI, independent of tooth substrate.
authors.affiliation: Department of Conservative Dentistry, Faculty of Dental Medicine, Modern Sciences and Arts University, Cairo, Egypt.
authors.forename: Aliaa Mohamed
authors.initials: AM
authors.lastname: El Wakeel
authors.affiliation: Department of Operative Dentistry, Faculty of Oral and Dental Medicine, Misr International University, Cairo, Egypt.
authors.forename: Dina Wafik
authors.initials: DW
authors.lastname: Elkassas
authors.affiliation: Department of Operative Dentistry, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt.
authors.forename: Mai Mahmoud
authors.initials: MM
authors.lastname: Yousry
keywords: Cementum; conventional glass ionomer; dentin; enamel; microshear bond strength; nano-ionomer; resin-modified glass ionomer