Role of fluoridated dentifrices in root caries formation in vitro.

Purpose: To evaluate in vitro root caries formation in human permanent teeth and to determine the effects of commercially available dentifrices containing different amounts of fluoride, while employing a well-tested artificial caries system using an acidified gel.
Methods: Root surfaces from caries-free human permanent teeth (n = 10) underwent debridement and fluoride-free prophylaxis. The tooth roots were sectioned into six portions, and acid-resistant varnish was placed with two sound root surface windows exposed on each tooth portion. Each portion from a single tooth was assigned to a treatment group: (1) No treatment control; (2) Denticious 5000 dentifrice (5,000 ppm F + xylitol); (3) PreviDent 5000 (5,000 ppm F); (4) AIM dentifrice (1,500 ppm F); (5) Listerine dentifrice (1,300 ppm F); and (6) Crest Regular Paste (1,500 ppm F). Tooth portions were treated with fresh dentifrice twice daily for 180 seconds, followed by fresh synthetic saliva rinsing over a 7-day period. Controls were exposed twice daily to fresh synthetic saliva rinsing over a 7-day period. In vitro root caries were created using an acidified gel (pH 4.25, 21 days). Longitudinal sections (three sections/tooth portion, 30 sections/group; 60 lesions/group) were evaluated for mean lesion depths (water imbibition, polarized light). Statistical analyses were performed using ANOVA and Duncan's Multiple Range test.
Results: Mean lesion depths were 389 +/- 43 microm for No treatment - control, 223 +/- 33 microm for Denticious 5000 dentifrice, 242 +/- 42 microm for Prevident 5000, 337 +/- 29 microm for AIM dentifrice, 297 +/- 37 microm for Listerine dentifrice, and 282 +/- 34 microm for Crest Regular Paste dentifrice. All treatment groups had mean depths significantly less than the No treatment - control group (P < 0.05). Denticious 5000 and PreviDent 5000 had significantly reduced mean depth compared with the other dentifrice treatment groups (P < 0.05).