In vitro permeability and scanning electron microscopy study of acid-etched and ground enamel surfaces protected with dental adhesive coating

Clinical procedures, such as acid etching and reshaping of the teeth suppor ting removable partial dentures by grinding off some enamel surface, increa se the permeability of dental enamel. Teeth take several months in vivo to partially recover from such damage. In the meantime, the tooth is more susc eptible to carious decay. To prevent this the ground or etched enamel shoul d be effectively protected. Using electron paramagnetic resonance (EPR) and a two-chamber diffusion cell the authors studied the influence of adhesive resin applied to the ground and acid-etched enamel surfaces on the diffusi on of spin label TMAPO (2,2,6-6 tetramethyl-4-acetamidopiperidine-1-oxyl) m olecules through the enamel. The enamel permeability was measured in sample s exposed to 1-min etching with 37% phosphoric acid, in samples etched for 5 min, and in samples ground with a diamond bur. Next, all the treated enam el surfaces were coated with Scotch-bond Multi-Purpose Plus(R) dental adhes ive system and the permeability measurements repeated. Scanning electron mi croscopy (SEM) was used to study the porosity of enamel surfaces. The adhes ive resin film covering the etched or ground enamel surfaces was found to d ecrease significantly the diffusion through dental enamel. This finding con firms the clinical value of dental adhesives used to protect ground or acci dentally acid-etched enamel surfaces. SEM analysis showed that adhesive res in covers the porous surface of the acid-etched and ground enamel tightly.