Evaluation of Hexametaphosphate-Containing Dentifrice on Root Dentin Erosion-Abrasion

Objectives: We have previously observed that a hexametaphosphate (HMP)-containing dentifrice may reduce erosive-abrasive surface loss on root dentin. In this study we further investigated the mechanisms that could potentially be involved with this protective effect. Methods: Two dentifrices: A. Crest Vivid White (HMP-containing; 1100 ppm F as NaF; RDA: 164.7 standard-deviation [SD] 17.8) and B. Crest Cavity Protection (non-HMP; 1100 ppm F as NaF; RDA: 103.4 SD 5.8) were compared in three different experimental conditions: Erosion-remineralization (Er-Rem) challenge, Abrasion-Remineralization (Abr-Rem) challenge and Erosion-Abrasion-Remineralization (Er-Abr-Rem) challenge. A total of 6 experimental groups (n=8) was generated. Forty-eight root dentin slabs (4x4x2) were cut from human teeth, embedded in acrylic resin and flattened/polished. Adhesive tapes were applied to the dentin surface, leaving an area of 4x1mm exposed for the treatments. The Er-Abr-Rem challenge consisted of immersion in 1% citric acid (pH 3.75) for 2min, remineralizing solution for 60min and of brushing for 150 strokes in an automated brushing machine (200g). This cycle was repeated 3x/day, for 3 days. Similar cycling protocol was used for the Er-Rem and Abr-Rem challenges, except for the brushing and erosion procedures, respectively. Results: Lower surface losses were observed for the Er-Rem cycling followed by the Abr-Rem and by the Er-Abr-Rem, for both dentifrices (p<0.05). HMP-containing dentifrice showed higher surface loss, in the Abr-Rem model (p<0.05), possibly because of its higher abrasive level (RDA). However, no differences on surface loss were observed between dentifrices in the Er-Rem and Er-Abr-Rem cycling (p>0.05). Conclusions: These results suggest that the relative reduction of surface loss observed for the HMP-containing dentifrice may be related to dentin erosion inhibition, although this could not be confirmed by the Er-Rem model. Further investigation using controlled experimental dentifrices is needed to define the role of HMP on the prevention of dentin erosion-abrasion.