Studies on Dental Stains Induced by Antibacterial Agents and Rational Approaches for Bleaching Dental Stains

Abstract

Extrinsic stain resides in the dental pellicle and can be caused by introduction of chromogenic materials or therapeutic agents into the oral cavity. In contrast, intrinsic tooth stain is found within the tooth structure and can be caused by a variety of agents, including hematological and developmental abnormalities and drugs such as tetracycline. The mechanisms of extrinsic stain formation differ with respect to the causative agent. For example, stain induced by chlorhexidine (CH) can be explained by an increased rate in the non-enzymatic browning reactions occurring at the pellicle surface, while food stains are retained on the surface via ion exchange mechanisms. Although most extrinsic dental stain can be removed by abrasive and/or surface-active materials, removal of certain types of surface stain, e.g., staining due to cationic antimicrobial agents, requires specific agents such as aminoguanidine to reduce the stain. A broad-spectrum approach to reduce both intrinsic and extrinsic dental stains clinically requires oxygenating agents. To evaluate this approach and understand the mechanisms of stain removal, we developed a spectroscopic method for measuring stain in vivo. A series of clinical studies was performed to evaluate stain removal by the agents. The results showed that carbamide peroxide in combination with surfactants and anti-redeposition agents, e.g., sodium pyrophosphate, was more effective in bleaching dental stain compared with carbamide peroxide alone. A detailed examination of the tooth structure by microhardness measurements, x-ray photoelectron spectroscopy, and scanning electron microscopy showed that stain decolorization with this system did not have any adverse effects.