Methods: Twenty sound premolars of similar size were utilized. Standardised ultraconservative proximal slot-type preparations were completed mesially in each tooth using an ultrasonic technique (SONICflex®, KaVo, Germany). Teeth were restored with Z250 (3M ESPE, St. Paul, MN, USA) and SureFil (Dentsply, Germany) resin composites using a hand instrumentation placement technique. The marginal adaptation of the restorations was assessed visually and with a probe. Five teeth were randomly selected, impressions taken and epoxy resin replicas produced. The replicas were tested by SEM to assess marginal adaptation. The restored teeth were embedded in epoxy resin and sectioned axially. Specimens were immersed in 0.5% basic fuchsin for 60s, rinsed, dried and examined (X10) by a stereomicroscope (S Wild M3Z, Heerbrugg Ltd, Switzerland). Digital micrographs were transferred to a computer for image analysis using SigmaScan Pro 5.0 software. The tooth/restoration interface was examined and the percentage tooth/restoration interface occupied by voids was calculated. Data obtained were analyzed by an independent-sample t-test.
Results: All restorations exhibited overfilled margins of the overlapping type. However, a significant difference was found between the two restorative materials in relation to percentage tooth/restoration interface occupied by voids (P<0.001). Z250: Mean (s.d.): 49.1 (±10.1); SureFil: Mean (s.d.): 64.1 (±3.9).
Conclusion: The findings indicate that the restorations of the injectable resin composite tested are better adapted than the restorations placed using the condensable resin composite tested.