Effect of application of desensitizers before bleaching on change of tooth shade

The aim of this in vitro study was to evaluate the effects of desensitizer pre-treatment on in-office bleaching using an artificial discoloration tooth model. The stained specimens were divided into four groups (n=10); without application (Control group), Shield Force plus (SF group), UltraEz (UE group) and Teeth Mate AP paste (TM group) applied before bleaching. Each group was bleached by an in-office bleaching agent. The CIE L*a*b* values were measured by a colorimeter before and after ten consecutive bleaching treatments and the color difference (∆E) was calculated. There was no statistical difference among ∆E values of Control, UE, and TM groups (p>0.05). There was a significant difference between SF and Control groups (p<0.001). It was concluded that application of TM and UE did not affect the change of tooth shade while SF application impeded the bleaching effect.

Effect of Calcium-phosphate Desensitizers on Staining Susceptibility of Acid-eroded Enamel

OBJECTIVE

To investigate the effect of calcium-phosphate-based desensitizers, Teethmate AP paste (TMAP) and Teethmate Desensitizer (TMD) (Kuraray Noritake Dental, Tokyo, Japan), on the prevention of staining on acid-eroded enamel.

METHODS AND MATERIALS

Forty polished enamel samples (4×4×1 mm) from bovine incisors were randomly divided into five groups (n=8). After immersion in 50 mL of 0.5% citric acid (pH 2.5) for 15 minutes to form acid-eroded surfaces, the surfaces were subjected to different treatments with TMAP, TMD, and NaF (0.21% means 950 ppm) for five minutes. Another eroded group was not treated with desensitizer. For the control group, the samples were not eroded or treated. All the samples were stored in artificial saliva (AS) at pH 7.2 for 24 hours at 37°C. The TMAP, TMD, or NaF was reapplied at eight and 16 hours during the 24 hours of storage time. The surface roughness (Sa) was evaluated following ISO 25178 for surface texture using confocal laser scanning microscopy (VK-X 150 series, Keyence, Osaka, Japan) before acid erosion, after acid erosion, and after 24 hours of incubation in AS. Afterward, the color difference was measured with a dental colorimeter (Shade Eye NCC, Shofu, Kyoto, Japan) before and after staining with tea solution.

RESULTS

One-way repeated measures analysis of variance showed that acid erosion significantly increased Sa (p<0.001). TMAP- and TMD-treated groups exhibited lower Sa values than the NaF group and the no-desensitizer treatment group. The greatest staining was observed in the NaF group and the no-desensitizer group, while the TMAP and TMD groups significantly decreased the formation of stains.

CONCLUSIONS

Acid-eroded enamel increased surface roughness and tended to absorb more stains. However, the application of TMAP and TMD moderated the roughness and thus prevented the formation of extrinsic stains.

Effect of sodium fluoride pretreatment on the efficacy of an in-office bleaching agent: An in vitro study

This in vitro study evaluated the effect of sodium fluoride (NaF) on the bleaching efficacy using an artificial discolored bovine tooth model. Twenty specimens were prepared from bovine teeth by staining with black tea extract and were divided into two groups (n = 10). In control group, specimens were immersed in distilled water for 30 min. In NaF group, specimens were applied with 0.2% NaF for 30 min. Then, the specimens in each group were bleached by an in-office bleaching material (Shofu Hi-Lite, Shofu, Kyoto, Japan). The CIE L*a*b* values were measured by a dental colorimeter before and after 10 consecutive bleaching treatments, and the color difference (ΔE) was calculated. Brightness and color difference (ΔE) increased in both groups per bleaching cycle. There were no statistical differences in ΔE values between both groups (p > 0.05). It was concluded that the application of NaF before bleaching did not interfere with the bleaching effect.