What is plaque and why is it so harmful?

Dental plaque. Treatment for dental plaque will reduce the risk for dental caries (cavities) and gingivitis. Regular brushing and flossing reduces that chance that plaque will damage the tooth enamel. Professional dental cleaning removes plaque and tartar that cannot be removed by brushing and flossing. Professional cleaning, performed once or twice a year, lso can prevent the build-up of plaque.
Dental, vascular or? Are you asking about dental, vascular, brain or skin plaques? A variety of diseases are caused by plaques: sweet's syndrome, alzheimer's disease, psoriasis, carotid artery disease, arteriosclerosis, are but a few.