['This study was a randomized, controlled, examiner-blind, four-period crossover design that examined the prevention of induced stain deposition through the use of chewing gums containing either 2.0% or 3.0% sodium hexametaphosphate (Na Hex).', 'The test treatments were an experimental chewing gum containing 2.0% Na Hex, a second experimental chewing gum containing 3.0% Na Hex, a placebo chewing gum (0.0% Na Hex) and no chewing gum. The study was carried out over a four-week period, with each treatment period lasting two days. Treatment periods were separated by a washout period of three to five days. Twelve subjects who met the inclusion and exclusion criteria were given a thorough dental prophylaxis limited to the anterior twelve teeth, and then underwent a baseline digital imaging assessment (DIA) procedure. Each treatment period involved two days of stain induction, which consisted of rinsing for 60 seconds with 10 ml of 0.12% chlorhexidine, followed by chewing with two pellets of the assigned chewing gum for five minutes or by no gum chewing, followed by rinsing with 10 ml of cold tea solution for 60 seconds. This regimen was repeated eight times throughout the day, approximately once an hour. Imaging was completed at baseline and at the end of day 2 of the induced stain regimen. Subjects refrained from any oral hygiene during the two-day stain induction periods.', 'Average baseline L* scores ranged from 76.30 to 76.57. At the end of the two-day stain induction regimen (eight hourly cycles per day) when no gum was chewed ("no gum"), subjects\' teeth were 5.18 units darker on average than they were at baseline. At the end of the two-day regimen when the placebo gum was chewed, subjects\' teeth were 4.54 units darker on average than they were at baseline. The difference between "no gum" and placebo gum was statistically significant (p = 0.017), and represented a 12.4% reduction in tooth darkness for the placebo gum treatment. Use of the 2.0% Na Hex gum resulted in teeth 3.64 units darker on average versus baseline, and the 3.0% Na Hex gum resulted in teeth 4.02 units darker. Both the 2.0% and 3.0% Na Hex gums resulted in teeth that were statistically significantly less dark (p < or = 0.042) than both the "no gum" and placebo gum treatments. On average, the reduction in tooth darkness for the 2.0% Na Hex gum was 29.7% versus "no gum" and 19.8% versus the placebo gum. The 2.0% Na Hex and 3.0% Na Hex gum treatments did not differ significantly (p = 0.114).'] Do the prevention of induced stain using two levels of sodium hexametaphosphate in chewing gum?