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Setting reaction of polyacid modified composite resins or compomers
J L R Arrondo1, M I Collado, Soler I
1Unidad de Biofísica (Centro Mixto CSIC-UPV/EHU) and Departamento de Bioquímica y Biología Molecular, Universidad del País Vasco, Spain. joseluis.arrondo@ehu.es
The Open Dentistry Journal
|October 17, 2009
Summary
Infrared spectroscopy revealed distinct hardening mechanisms in glass-ionomers and compomers. Glass-ionomers undergo acid-base reactions and cross-linking, while compomers utilize free-radical polymerization alongside these processes.
Area of Science:
- Materials Science
- Polymer Chemistry
- Biomaterials Science
Background:
- Dental restorative materials like compomers and glass-ionomers are crucial in clinical practice.
- Understanding their hardening mechanisms is essential for optimizing material properties and longevity.
Purpose of the Study:
- To investigate and differentiate the hardening mechanisms of modified polyacid composite resins (compomers) and glass-ionomers.
- To elucidate the role of acid-base reactions and polymerization in the setting process of these dental materials.
Main Methods:
- Utilized infrared spectroscopy to analyze the chemical changes during the hardening process.
- Employed band narrowing techniques to enhance spectral resolution and identify specific functional groups.
- Studied the acid-base reaction in a glass-ionomer (Ketac-fil) by monitoring specific infrared bands (COOH and COO⁻).
Main Results:
- Identified two maturation steps in glass-ionomers: a rapid acid-base equilibrium followed by polycarboxylate cross-linking with metal ions.
- Described a novel free-radical polymerization reaction in compomers, occurring alongside acid-base related steps.
- Confirmed water's essential role in compomer hardening, noting the absence of an acid-base reaction (no COO⁻ band) but presence of methacrylate polymerization and metal cation chelation.
Conclusions:
- Glass-ionomers harden via a two-step process involving acid-base reactions and cross-linking.
- Compomers exhibit a dual hardening mechanism: free-radical polymerization and acid-base reactions, with water playing a critical role.
- Infrared spectroscopy is a powerful tool for differentiating the complex chemical reactions in dental restorative materials.
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