title: Effect of different gingival margin restorations of class II cavities on microleakage: an in-vitro study.
abstract: BACKGROUND
  Microleakage is one of the important contributing factors in the failure of resin restorations. The aim of this study was to determine the effect of the location of the gingival margin (enamel, dentin, or cementum) on nanohybrid composite resin on the microleakage of Class II posterior restoration.
  
  
  METHODS
  This was an in vitro study done at Al-Farabi College of Dentistry and Nursing in Jeddah (Saudi Arabia). Eighty-one previously extracted human molars were taken from clinics at Al-Farabi College and divided into three main groups (27 each) according to the location of the gingival margin. Group 1: the location of the gingival margin was in the enamel. Group 2: at the cemento-enamel junction. Group 3: in the cementum. Each main group was divided into three subgroups (9 each) according to storage time. Subgroup A: storage time was 24 hours. Subgroup B: storage time was one month. Subgroup C: storage time was three months. Class II cavity was prepared in one proximal surface for each molar following the general principles of cavity preparation. All samples were restored by nanohybridresin composite (TetricEvoCeram). The specimens were stored in distilled water at 37°C and a humidity of 100% in an incubator for one day, one month, and three months, respectively, according to the subgroups. After sealing, the samples were stained with 2.5% methylene blue dye. Each sample was examined microscopically by a stereomicroscope using a computerized image analyzing system. Statistical analysis was done by two-way ANOVA test comparing dye penetration mean values (μm).
  
  
  RESULTS
  The value of dye penetration increased remarkably from enamel, Cemento-enamel junction [CEJ] to cementum, and this was statistically significant (p < 0.001).
  
  
  CONCLUSIONS
  None of the materials tested was able to completely eliminate marginal microleakage at different gingival margins. The least dye penetration was detected at the enamel gingival margin followed by CEJ and then cementum. The least microleakage was observed at the gingival margin located in the enamel.
authors.affiliation: Al-Farabi College of Dentistry and Nursing, Jeddah, Saudi Arabia.
authors.forename: Ahmed Ibrahim
authors.initials: AI
authors.lastname: Mahrous
authors.affiliation: Maghrabi Dental Centers, Jeddah, Saudi Arabia.
authors.forename: Hani Abdulmoniem
authors.initials: HA
authors.lastname: Eltiti
authors.affiliation: Al-Farabi College of Dentistry and Nursing, Jeddah, Saudi Arabia.
authors.forename: Iffat Mirza
authors.initials: IM
authors.lastname: Ahmed
authors.affiliation: Al-Farabi College of Dentistry and Nursing, Jeddah, Saudi Arabia.
authors.forename: Ebaa Ibrahim
authors.initials: EI
authors.lastname: Alagha
keywords: class II restoration; gingival margins; microleakage; nanohybrid composite