Stain Removal and Abrasivity of Various Commercial Dentifrices in Vitro

In recent years dentifrice companies have emphasized stain-removal properties in their marketing, adding various terms like "cleaning" or "whitening" to product tradenames, while also citing product gentleness and polishing ability. Enhancement of these properties is attributed to improved abrasive systems and other ingredients.

Objective: To examine the relationship between stain-removal effectiveness and abrasivity of representative commercial dentifrices that have a variety of compositions and are marketed for cleaning, whitening, and/or polishing capabilities.

Methods: Stain removal was assessed by the PCR method (JDR 61:1028, 1982), which correlates with clinical cleaning power of dentifrices. Dentin abrasion was assessed using the RDA method (JDR 55:563, 1976). For PCR stained bovine teeth (n=16) and for RDA irradiated human dentin (n=8) were brushed (V-8 machine, 150-gm) for 800 and 1500 strokes, respectively, using aqueous dentifrice slurries. Stain was assessed as diffuse reflectance absorbance (Minolta CM-503i), and abrasion as slurry radioactivity with a scintillation counter. Both methods used ADA calcium pyrophosphate reference standard. Statistical analyses were performed by t-tests.

Results: All dentifrices removed extrinsic stain and produced dentin abrasion, but scores ranged widely (39-145 for PCR and 51-269 for RDA). The majority contained hydrated silicas, and those with high PCR scores often, but not always, had high RDA scores. Products containing other abrasives (e.g. dicalcium phosphate, sodium bicarbonate, calcium carbonate) generally had lower RDA scores and usually lower PCR scores, but there were exceptions (e.g. refined kaolin) that had high PCR scores and low RDA scores. The Cleaning Efficiency Index (JDR 71:559, Abst. 352, 1992) indicated that other ingredients (e.g. peroxide) also affected stain removal.

Conclusions: Stain-removal ability and abrasivity of dentifrices, especially those containing silicas, was highly variable, and the relationship between these two factors was not necessarily direct. With some exceptions, dentifrices marketed as "whitening" products generally were more abrasive than other products.