Enamel Polish Evaluation in Vitro of Various Commercial Dentifrices

Objective: This laboratory study evaluated enamel polishing effectiveness of toothbrushing with 26 dentifrices which are currently marketed for whitening and/or polishing capabilities and have an assortment of different compositions.

Methods: Labial surfaces of bovine, permanent incisors were leveled with a surface grinder to produce, flat surfaces suitable for optical measurements. Enamel polish was measured before/after treatment by taking specular reflectance readings (60°) with a Rhopoint Novo-Curve™ Glossmeter. Before treatment, specimens were etched in 0.5M HCl (30 sec) to provide dull baseline surfaces. Treatments were performed on a V-8 cross-brushing machine using dentifrice slurries (5:8 dentifrice/water ratio) and ADA nylon-bristle toothbrushes at 300 gm pressure for 2000 strokes. 26 commercial dentifrices were tested with RDA calcium pyrophosphate (1:5 with 0.5% CMC) as a reference standard. Results are reported as percentage of white carrara glass standard (mean, n=8). Between-treatment comparisons were performed by ANOVA and SNK test.

Results: Brushing with all dentifrices increased reflectance readings of acid-dulled teeth, but mean polish scores ranged widely among products. The most effective dentifrice contained refined kaolin clay and provided a polish score of 97, which was significantly better than the reference standard (67) and all other dentifrices (38-86). The majority of products contained hydrated silica abrasive systems, but their polish scores varied extensively from (38-80). Products containing other abrasives, e.g. dicalcium phosphate, sodium bicarbonate, and calcium carbonate, provided polish scores that fell within the range of hydrated silica-containing products, although one containing fuller's earth was slightly better (86).

Conclusion: Enamel polishing ability of dentifrices, especially those containing silicas, was highly variable, and did not correspond directly with abrasive systems as listed on the labels. With the exception of a product containing refined kaolin clay, dentifrices marketed for imparting luster or sheen to teeth were no more effective than other products.