Polymerization stress development in dental composites: Effect of cavity design factor

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Polymerization stress development (PSD) is a critical factor in the longevity of resin composite restorations.
• The cavity design factor (C-factor) relates the bonded area to the unbonded surface area of a restoration, potentially influencing stress generation.

Purpose of the Study:

• To investigate the effect of the cavity design factor (C-factor) on polymerization stress development (PSD) in experimental and commercial resin composites.
• To compare PSD and degree of conversion (DC) between an experimental remineralizing composite (BT/ACP) and a commercial composite (TPH).

Main Methods:

• Experimental resin (BT resin) and BT/ACP composite (with amorphous calcium phosphate filler) were prepared. Commercial TPH composite served as control.
• C-factor was varied (0.8–6.0) by altering specimen height. PSD was measured using cantilever beam tensometry.
• Degrees of vinyl conversion (DC) were measured using near-infrared spectroscopy.

Main Results:

• Polymerization stress development (PSD) increased with increasing cavity design factor (C-factor) for both BT/ACP and TPH composites.
• The experimental BT/ACP composite exhibited higher measured and calculated PSD values compared to the commercial TPH composite.
• The BT/ACP composite showed a higher degree of conversion (DC) (69.5%) than the TPH composite (57.5%) at 2 hours post-cure.

Conclusions:

• The cavity design factor (C-factor) significantly influences polymerization stress development (PSD) in resin composites.
• Composite composition, including resin and filler types and amounts, also plays a crucial role in PSD and degree of conversion (DC).
• Understanding the interplay between C-factor and material composition is essential for minimizing stress in dental restorations.