Dentinal Tubule Occlusion with Stannous Fluoride and KNO3/Gantrez Dentifrices

Dentifrices with proven clinical desensitization efficacy include formulations which form smear layers to block patent tubuli (stannous fluoride) as well as those which provide efficacy through nerve desensitization (KNO₃). Rates of desensitization can be influenced by these different mechanisms of action (Ayad, J Clin Dent 20, 115 2009).  Objectives: This study examined dentinal tubule occlusion effects of commercial stannous fluoride and KNO₃ dentifrices and their mechanical and chemical durability in vitro. Methods: Etched coronal dentin specimens were prepared from extracted human third molars. Specimens were randomized for average patent tubule diameter and density allocated to dentifrice treatment groups (N=6) including sodium fluoride/Gantrez/KNO3 (Colgate® Pro Relief, US formula – CPR-US) and stannous fluoride/hexametaphosphate (Crest® Pro-Health SNF2).  Specimens were brushed with dentifrice for 5 brushing-cycles comprised of 2 minute paste applications followed by 1 hour saliva immersion. Post-brushing (PB) samples were gently agitated 16-hours in saliva to test smear layer physical durability (SW). Following saliva agitation specimens were challenged with acidic cola beverage for 1 minute to examine chemical durability (AW)). Surfaces were imaged by light microscopy after 60 sec (PB1/2), 1 brushing cycle (PB1), 5 brushing cycles (PB5), saliva wash (SW) and acid wash (AW). Specimens were graded blind to treatment on a 6-point scale from : 0: open tubuli to 5: no open tubuli, intact smear layer (Zsiska, IADR San Diego 2011, Poster 2634) Results: PB1/2: SNF2: 2.21a CPR-US 0.51b; PB1: SNF2: 2.43a CPR-US 1.94b; PB5: SNF2: 3.56a CPR-US 2.36b; SW: SNF2: 2.72a CPR-US 2.22b; AW: SNF2: 2.36a CPR-US 1.89b (a≠b p < 0.05 Students t comparison). Conclusions: Stannous fluoride containing dentifrices produced more rapid onset of tubule occlusion than Gantrez/KNO3 dentifrice.  Likewise, SnF₂ smear layers were durable to physical and chemical challenge. These results point to clear mechanism differences in sensitivity relief provided by commercial formulations.