The polymerization in thin films on smooth tooth surfaces was assessed for four conventional bonding and pit and fissure sealants and one new acetone-containing sealant. A routine bonding procedure was followed up to the stage of bracket placement. The sealants were allowed to polymerize buccally and lingually on forty-four premolars, which were then carefully extracted and analyzed clinically and in the stereomicroscope. For thirty-eight surfaces, a soluble ultraviolet dye (sodium fluorescein) was added to the universal resin, and these teeth were examined by fluorescence microscopy of ground sections. On the remaining fifty surfaces a chemical analysis of polymerized sealant was made after demineralization in 10 percent hydrochloric acid and included infrared spectroscopy, refractive index, and combined gas chromatography and mass spectrometry.
The results demonstrated that, despite some individual variation, all four conventional sealants failed to produce a thin protective film to cover the entire etched enamel surfaces. This was mainly due to nonpolymerization caused by oxygen inhibition and to sealant flow before setting. The chemical analyses indicated a large amount of unreacted methacrylate groups where these sealants had polymerized. In contrast, the acetone-containing sealant polymerized to a thin film with less remaining methacrylate groups.
The need for improved sealants for orthodontic bonding purposes was discussed
Problems with sealants for bracket bonding.
Zachrisson BU, Heimgård E, Ruyter IE, Mjör IA.
Am J Orthod. 1979 Jun; 75(6): 641-649.