Comparative analysis of conversion and crosslinking degree in bulk-fill, monochromatic, and ORMOCER composites

Area of Science:

• Restorative Dentistry
• Materials Science
• Polymer Chemistry

Background:

• Bulk-fill, monochromatic, and ORMOCER composites aim to improve clinical efficiency and reduce stress in dental restorations.
• While immediate properties are comparable to conventional composites, long-term behavior and polymer matrix structure require further investigation.

Purpose of the Study:

• To evaluate the degree of conversion and crosslink density of conventional, bulk-fill, monochromatic, and ORMOCER resin composites.
• To assess the impact of ethanol storage on the mechanical properties (flexural strength, elastic modulus, hardness) and material stability (sorption, solubility).

Main Methods:

• Fourier-transform infrared spectroscopy (FTIR) for degree of conversion measurement.
• Three-point bending and Knoop microhardness testing for mechanical properties (dry and after ethanol storage).
• Water sorption and solubility tests following standard protocols.

Main Results:

• Degree of conversion was statistically similar across all tested composite types.
• Ethanol storage caused comparable reductions in mechanical properties for bulk-fill and monochromatic composites from the same manufacturer.
• ORMOCER materials showed different responses to ethanol storage, and sorption/solubility varied, indicating compositional differences.

Conclusions:

• Bulk-fill and monochromatic composites, from the same manufacturer, exhibit similar crosslinking and polymeric structures.
• ORMOCER materials, despite comparable initial properties, do not share the same crosslinking stability as bulk-fill and monochromatic types after ethanol exposure.