This 12-week prospective, randomized, double-blind, two-center trial evaluated the impact of a microcrystalline zinc-hydroxyapatite (mHA) dentifrice on plaque formation rate (PFR) in periodontitis patients. The investigators hypothesized that mHA precipitates cause delayed plaque development when compared to a fluoridated control (AmF/SnF2), and therefore would improve periodontal health.