PubMed · 3857686
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G Basting. 1985. [Toothpastes].. https://pubmed.ncbi.nlm.nih.gov/3857686/
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The increasing emphasis on dental aesthetics has made tooth whitening an important function of a dentifrice. This laboratory study investigated the whitening effect of toothbrushing with sodium bicarbonate-based dentifrices compared with standard dentifrices that do not contain sodium bicarbonate. Six dentifrices and a distilled water control were tested for their ability to whiten teeth with intrinsic stain. The dentifrices contained different abrasive systems: (1) 45% NaHCO3; (2) 65% NaHCO3 (Arm and Hammer Dental Care); (3) 94% NaHCO3; (4) 94% NaHCO3 + 1.5% H2O2; (5) silica (Crest Regular Toothpaste); and (6) dicalcium phosphate (Colgate Regular Toothpaste). After a thorough rubber cup cleaning with a pumice slurry, the intrinsic color of the test teeth with a Vita shade of A3 or darker was measured with a spectrophotometer using the standard L*a*b* color scale. Measurements were taken on a total of 12 teeth per test dentifrice before treatment, and after 30, 60, 90 and 120 minutes of mechanical toothbrushing. No changes in L* (lightness/brightness) or a* (red-green hue) occurred, but significant differences in b* (yellow-blue hue) were observed over time. Compared to baseline tooth color, all four sodium bicarbonate-based dentifrices were significantly effective in removing the yellow intrinsic tooth stain, while the water control, silica dentifrice, and dicalcium phosphate dentifrice demonstrated no significant change. Between-group comparisons showed that the four dentifrices containing sodium bicarbonate were significantly more effective than the water and dicalcium phosphate dentifrice groups. The commercial dentifrice containing 65% sodium bicarbonate was also more effective than the commercial silica dentifrice. Although continued toothbrushing from 30 to 120 minutes resulted in additional stain removal, most of the tooth whitening by the sodium bicarbonate-based dentifrices occurred in the first 30 minutes of brushing. In the studies conducted, dentifrices containing high concentrations of sodium bicarbonate were more effective at removing intrinsic tooth stain than dentifrices that do not contain sodium bicarbonate.
The effect of Sensodyne dentifrice, which contains strontium chloride hexahydrate, on the occlusion of dentinal tubules was studied in vivo and in vitro. Eight premolar teeth scheduled for extraction for orthodontic purposes were used. Four of the teeth were extracted before Sensodyne application (in vitro). The other four teeth were treated in vivo and then extracted. A patch of enamel was removed from all the teeth to expose the dentinal surfaces, and the smear layer over the exposed area was removed. In the in vivo test, the patients were instructed to brush their teeth for 1 minute, twice a day, for 2 weeks. The teeth were then extracted and kept in distilled water until examined by scanning electron microscope. The in vitro teeth were brushed in the same manner and kept in distilled water between brushings. Most of the in vitro dentinal tubules were found to be open, whereas most of the in vivo dentinal tubules were occluded.
Toothbrush bristles with sharp edges have been postulated to represent a greater threat to dental tissues than end-rounded bristles. This study evaluated the effect of both in vivo and laboratory use on bristle wear rate, tip geometry and in vitro abrasivity. Three soft manual brushes (Oral-B P40, Crest Complete and Butler GUM) and one powered brush (Rota-dent) were tested. The results of this study show that the wear rate varied directly with brushing load and amount of dentifrice, and inversely with bristle diameter. Despite the initial geometry, a flat tip with rounded rims was typically observed after only 30 minutes of manual or Rota-dent brush use. There was no statistical difference in in vitro abrasion for new brushes versus used brushes.