Lustre changes on teeth. The use of laser light for reflexion measurements on the tooth surface--in vivo.

Lustre changes on teeth in vivo were studied with the use of equipment based on a helium-neon gas laser. Variations of the intensity of laser light reflected from the tooth surface were measured under different conditions of accumulation and removal of deposits, which were assumed to consist mainly of the pellicle. The possibility of using fluoride varnish as an artificial surface layer in this kind of investigation was also tested but rejected. Measurements were made after toothbrushing with water alone and with two toothpastes possessing different degrees of abrasivity. Teeth that had been left without toothbrushing for 24 hours showed statistically significant (p less than 0.05) lower light reflexion values than those recorded immediately after the teeth had been brushed with a toothpaste. During a period of seven months, persons brushing their teeth with water alone generated lower intensity values than did those brushing with the two toothpastes. The more abrasive paste yielded the highest intensity values, indicating a more polished or cleaner surface. The results suggest that the use of a toothpaste containing abrasives contributes to the cleaning effect of toothbrushing.