Laboratory and FEA evaluation of dentin-to-composite bonding as a function adhesive layer thickness

Area of Science:

• Dental materials science
• Biomaterials engineering
• Adhesive dentistry

Background:

• The thickness of the adhesive layer in dental restorations can influence bond strength.
• Understanding this relationship is crucial for optimizing composite restoration longevity.

Purpose of the Study:

• To investigate the hypothesis that microtensile bond strength is inversely proportional to dentin-composite adhesive layer thickness.
• To compare the behavior of two different adhesive systems under varying layer thicknesses using mechanical testing and finite element analysis.

Main Methods:

• Microtensile bond strength testing was performed on 18 human molars using two adhesive systems (Single Bond and Clearfil SE Bond) with varying layer thicknesses (40, 40-80, 80-120 microm).
• Finite element analysis (FEA) was used to determine maximum principal stresses (MPS) at different adhesive layer thicknesses (20, 50, 100 microm).

Main Results:

• Single Bond showed significantly higher bond strength with thinner adhesive layers (0-40 microm) compared to thicker layers.
• Clearfil SE Bond exhibited no statistical difference in bond strength across all tested adhesive layer thicknesses.
• FEA indicated that maximum principal stresses increased with increasing adhesive layer thickness.

Conclusions:

• The hypothesis was supported only for Single Bond, where increased adhesive thickness led to reduced bond strength.
• A correlation between microtensile testing and FEA was observed for Single Bond but not for Clearfil SE Bond.
• Adhesive system type influences the effect of layer thickness on bond strength and stress distribution.