Marginal hybrid layer in Class V restorations

Area of Science:

• Dental Materials Science
• Restorative Dentistry
• Biomaterials

Background:

• The hybrid layer is crucial for the micromechanical retention of adhesive restorations.
• Understanding hybrid layer morphology at the cementoenamel junction (CEJ) is vital for long-term restoration success.
• Variability in bonding systems may influence hybrid layer formation and integrity.

Purpose of the Study:

• To evaluate the morphology and thickness of the marginal hybrid layer at the CEJ of Class V restorations.
• To compare the effects of different bonding systems and post-etching treatments on hybrid layer formation.
• To assess the impact of noninfiltrated collagen on the sealing capability of dental adhesives.

Main Methods:

• Class V restorations were prepared in vitro on extracted third molars at the CEJ.
• Three bonding systems (Scotchbond 1, Scotchbond MP, Clearfil Liner Bond 2V) were used.
• SEM analysis was performed after treatment with phosphoric acid and/or NaOCl gel to evaluate hybrid layer morphology and thickness.

Main Results:

• Scotchbond MP and Scotchbond 1 exhibited marginal hybrid layer thicknesses of 1.5-2.5 microns.
• Clearfil Liner Bond 2V showed a variable hybrid layer thickness (0.0-12.0 microns) with increased porosities, especially after NaOCl treatment.
• Enamel margins lacked a hybrid layer in all tested groups.

Conclusions:

• Collagen fibrils at the CEJ are not completely infiltrated by adhesive resin, irrespective of the bonding system.
• Incomplete infiltration and porosities in the hybrid layer may compromise the sealing ability of the restoration.
• The findings suggest potential long-term durability issues for Class V restorations at the CEJ due to inadequate hybrid layer formation.