Occlusion effect of dentinal tubules of the dentifrice containing sodium metasilicate

Exposed dentine with patent tubules allows the movement of tubule fluid leading to dentine sensitivity. Occlusion of patent dentinal tubules effectively reduces the state of dentine hypersensitivity. Strontium chloride (SrCl ₂) has been well known as a component of desensitizing dentifrice. Recently, new dentifrice containing sodium metasilicate was on the market for desensitizing dentifrice. The aim of this in vitro study was to compare the occlusion effect of dentinal tubule between the sodium metasilicate and the existing desensitizing dentifrices. Sixty-four human dentine specimens were embedded into a Teflon mold and were grinded with the use of silicone carbide papers to expose the surface of dentin. The dentin surface was etched with 37% phosphoric acid for 60 seconds and was treated with ultrasonic washing for 1 hour. The dentifrices used in the study are classified into four groups: G1-dentifrice containing Sodium metasilicate, G2-dentifrice containing Strontium chloride, G3-dentifrice containing Hydroxyapatite and G4-BSI reference dentifrice (control group). Toothpaste slurries were prepared as 20 gram of toothpaste in 80 ml of distilled water. Thirty-two specimens were brushed with the toothpaste slurries using V8 Cross Brushing Machine. Tooth-brushing was performed 5,000 times using a back-and-forth stroke. The pictures of the sizes of dentinal tubules were taken by scanning electron microscopy (×3000) and changes of tubule sizes were analyzed by digital analysis. The results showed that the difference of tubule size in descending order: G1-3.30±1.80, G2-2.82±1.73, G3-1.49±1.14, G4-1.04±0.94. The dentifrice containing Sodium metasilicate (22.5%) showed the highest dentinal tubule occlusion. Moreover, the dentifrice containing Sodium metasilicate statistically significantly increased occlusion of dentinal tubule as compared to BSI reference dentifrice (p<0.05). Thus, new desensitizing dentifrice containing sodium metasilicate was more effective than existing desensitizing dentifrice on occlusion of dentin tubules.