Degenretive changes of various nerve terminals in the intradental tissues of dog canine teeth after cavity preparation, acid-etching and restoration with composite resin.

Abstract

The degenerative changes of the sensory and autonomic nerve terminals in the odontoblast layer and in the predentin of dog canine teeth were examined ultrastructurally at 5, 10, 20, 30 and 60 days following the class V cavity preparation, acid-etching with 30% phosphoric acid applied to enamel periphery and dentin, and restoration with composite resin.For the sensory nerve terminals, mitochondria in the Schwann cells and in the terminal axons showed severe degenerative changes following dental treatment throughout the experimental periods. In addition, no neurofilaments were clearly observed in cross-sections of the degenerated axon. For the adrenergic nerve terminals, uniform and electron-very dense granular vesicles, so-called granular vesicles, often changed into light-staining granular vesicles, so-called agranular vesicles. For the cholinergic nerve terminals, agranular vesicles, smaller than electron-dense granular vesicles characteristic for the adrenergic nerve terminals, showed severe degenerative changes after dental treatment throughout the experimental periods.