Influence of different GI restorative techniques on microleakage of Cl II sandwich restorations

Sandwich technique with glass ionomer (GI) has been recommended to overcome gingival microleakage. The study objectives were to compare open and closed sandwich techniques and evaluate GI injection in sandwich restorations. Sixty extracted sound premolar teeth were divided into 4 groups (n=15). A Class II cavity with gingival margin below CEJ was prepared on each tooth. Teeth were restored using glass ionomer (Fuji II LC), adhesive (Single Bond) and resin composite (Z250) as follows: Group 1, Open sandwich, GI injection; Group 2, Open sandwich, placing GI by a probe; Group 3, Closed sandwich, GI injection; Group 4, Closed sandwich technique, placing GI by a probe. Dye penetration was performed by using fushin after thermocycling. Teeth were sectioned then dye penetration was evaluated (0-3 scores) under a stereomicroscope. Statistical analysis was conducted using Kruskal Wallis and Mann-Whitney U tests. The least microleakage was observed in closed sandwich technique with GI injection and the most microleakage was observed in open sandwich using GI by a probe. When comparing the handling techniques, it was shown that using a syringe was significantly better than using a probe (P<0.05). There was no statistical difference between open and closed sandwich techniques although the mean dye penetration happened less in closed technique. According to the results of this study, injection of GI into cavity is recommended because of better access and superior adaptation of GI with cavity walls.