Efficacy of MI Paste Plus in protecting overdenture abutments

Objectives: Overdenture abutment teeth are at high risk for caries and the current protective protocol includes the daily application of fluoride. This study examined the efficacy of MI Paste (GC America) and MI Paste Plus (GC America) in preventing demineralization on the root surface and cut dentin of overdenture abutments. Methods: Premolars and canines (n=60, 5 groups of 12) were prepared as overdenture abutments and coated with acid resistant varnish leaving a 1x3mm window open on the root surface and cut dentin. For 30 minutes per day, teeth were treated with one of the following: MI Paste Plus (A), 1,100ppm fluoride dentifrice (Crest Cavity Protection, Procter and Gamble) (B), 5,000ppm fluoride gel (Colgate PreviDent Gel, Colgate-Palmolive Company) (C), and water as a control (D). After each treatment, teeth were rinsed clean then cycled for 6 hours in demineralizing solution (pH 4.3) and 17.5 hours in remineralizing solution (pH 7.0) for 20 days. In addition, a fifth group was treated with MI Paste (E) which was left on the teeth during the acid challenge. Sections 100±10µm were cut and photographed using polarized light microscopy and mean lesion depths were measured. Results: For root surface lesions, A and E did not offer protection from demineralization when compared to the distilled water control (lesion depths of 226±33µm, 203±23µm, and 222±24µm respectively). B (121±15µm) and C (90±21µm) outperformed and were significantly different than controls (p<0.05). On cut dentin, B (76±12µm) and C (81±12µm) were significantly different from the control (p<0.05). A (284±41µm) and E (288±41µm) did not offer significant protection when compared to the distilled water control (299±28µm). Conclusions: Under this model, treatment A applied before acid challenge did not offer significant protection against demineralization for the root surface or cut dentin of overdenture abutments, nor did treatment E when left on teeth during acid challenge. Supported by NIH/NIDCR T32 DEO14678.