Contraction gaps in Class II restorations with self-cured and light-cured resin composites

Area of Science:

• Restorative Dentistry
• Dental Materials Science
• Biomaterials

Background:

• Marginal gap formation in composite restorations can lead to secondary caries and pulpal issues.
• The use of intermediate layers of autopolymerizing composite aims to improve marginal integrity in Class II restorations.

Purpose of the Study:

• To evaluate in vitro the cervical gap formation in composite restorations.
• To compare the efficacy of two different dentin bonding systems (All-Bond and Superbond D) when an autopolymerizing composite increment is interposed between the bonding agent and light-cured composite.

Main Methods:

• Class II cavities with gingival margins in dentin/cementum were prepared.
• An autopolymerizing composite (Palfique or Bisfil 2B) was placed between a dentin bonding system (All-Bond or Superbond D) and light-cured composite (Palfique Estelite).
• Dye penetration was assessed using toluidine blue and optical microscopy, followed by SEM analysis after 1-4 months of water storage.

Main Results:

• All-Bond/Bisfil 2B demonstrated excellent marginal adaptation.
• Superbond D/Bisfil 2B showed the highest incidence of marginal gap formation.
• A significant difference (P<0.001) in gap formation was observed between All-Bond and Superbond D treatments.
• Hygroscopic expansion after water storage reduced gap formation, diminishing significant differences between treatments.

Conclusions:

• The choice of dentin bonding system significantly impacts marginal adaptation in composite restorations when using an intermediate autopolymerizing layer.
• All-Bond appears to be a more reliable bonding agent in this context compared to Superbond D.
• Long-term water storage can mitigate initial marginal discrepancies due to hygroscopic expansion of restorative materials.