Effects of acids used in the microabrasion technique: Microhardness and confocal microscopy analysis

Effects of microabrasion association to at-home bleaching on hydrogen peroxide penetration and color change

PURPOSE

This study aimed to quantify the penetration of hydrogen peroxide (HP) inside the pulp cavity and color change with two different concentrations of HP to at-home bleaching associated or not with enamel microabrasion (MA).

METHODS

Forty healthy premolars were randomly divided in four groups (n = 10): only HP4%, MA + HP4%, only HP10%, MA + HP10%. The concentration (μg/ml) of HP was assessed using UV-Vis spectrophotometry. The color change (ΔEab , ΔE00 and WID ) was evaluated before and one-week after bleaching. Data were evaluated for a two-way ANOVA and the Tukey's test (α = 0.05).

RESULTS

The application of MA increased the amounts of HP inside the pulp chamber when compared to without MA, as well as PH10% when compared to PH4% (p < 0.0001). PH10% showed higher WID when compared to PH4%. No significant difference was observed when ΔEab , and ΔE00 were used.

CONCLUSIONS

The enamel MA before at-home bleaching promotes greater penetration of HP, although this procedure did not significantly affect the color change.

CLINICAL SIGNIFICANCE

Since greater penetration of HP into the pulp chamber was detected when home bleaching was applied immediately after MA, the clinician should not apply home bleaching gels in the same session when MA was performed.

Effects of Microabrasion Prior to In-office Bleaching on Hydrogen Peroxide Permeability, Color Change, and Enamel Morphology

PURPOSE

This study evaluated hydrogen peroxide (HP) diffusion within the pulp chamber, as well as color change and the surface morphology of teeth subjected to various microabrasion (MA) protocols associated or not with in-office (IO) bleaching.

METHODS

Forty sound premolars were randomly divided into the following four groups (n=10): no treatment (NC); IO bleaching only; IO immediately after MA (IMA), and IO seven days after MA (7MA). After treatments, the HP concentration (μg/mL) within the pulp chamber was determined using ultraviolet-visible (UV-Vis) spectrophotometry. The color change (ΔE*) was evaluated using the digital spectrophotometer before and 1 week after bleaching. The surface morphology was evaluated by scanning electron microscope (SEM). Data from each test were submitted to one-way ANOVA and Tukey tests (α=0.05).

RESULTS

All experimental groups exhibited higher HP concentrations compared to the NC group (p<0.00001). However, higher amounts of HP were observed for the IMA group compared to the IO and 7MA groups (p<0.00001). No significant difference in color change was observed among the groups (p<0.001). Pronounced grooves in enamel were found in the IMA and 7MA groups. However, enamel erosion areas were observed only in the 7MA group.

CONCLUSIONS

The association between MA and IO bleaching could significantly affect the amount of HP inside the pulp chamber. Therefore, it is highly recommended to wait for 1 week after MA procedures before performing IO bleaching.

Microabrasion effect on enamel susceptibility to penetration of hydrogen peroxide: an experimental and computational study

To evaluate in vitro transenamel/transdentinal of penetration of H₂O₂ after microabrasive. Computational models were performed to verify peroxide penetration and evaluate if geometric modifications could affect in vitro results. Enamel/dentin blocks from bovine incisors were prepared and randomly divided into groups (n = 15) according with abrasive (35% phosphoric acid and pumice or 6.6% hydrochloric acid and silica) and bleaching agents (16% carbamide peroxide and 35% H₂O₂). From artificial pulp chambers, the H₂O₂ concentration was measured and SEM was used for surface morphology. Numerical models were performed (Abaqus® v6.12) modifying slightly enamel/dentin thickness based on experimental data. All groups presented H₂O₂ penetration, although no significant difference was noted between the control and experimental groups (p > 0.05). The numerical analysis demonstrated the role of dental tissue thickness in the H₂O₂ penetration. Microabrasion is recommended as its association with bleaching procedures and small modifications in thicknesses of enamel/dentin can cause substantial changes in HP penetration. Such diffusion aspect is clinically relevant for the bleaching procedures since very thin enamel could present more peroxide propagation through dental tissues.

Weight-loss and surface roughness of enamel after microabrasion procedure with different agents

Abstract Introduction Enamel microabrasion is achieved by abrasion of the enamel surface and it is a quick, practical and efficient procedure. Objective It was assessed the weight loss and surface aspect of enamel after microabrasion procedures with commercial and mixtures made in-office. Material and method Eighty bovine incisors were divided into four groups (n=10): OpalustreTM (6.6% HCl + silicon carbide); Whiteness RMTM (6% HCl + silicon carbide); 37% H3PO4 + pumice and 10% HCl + pumice. Treatment was performed by 15 applications of 10s duration. The enamel weight loss was determined by the difference in weight before and after the microabrasion. The surfaces were analyzed by a surface roughness equipment and scanning electron microscopy. Data were submitted to paired-T test, one-way ANOVA and Tukey tests (α=0.05). Result It was observed significantly weight loss for all groups. The difference in weight loss ranged from 0.037±0.012 for group 37% H3PO4 and from 0.054±0.009 for group 6,6% HCl. There was a significant increase in surface roughness for all groups and 10% HCl group showed the lower results (0.65±0.09). It was observed different patterns of enamel morphology by SEM images. Conclusion The in-office mixtures resulted in the lowest enamel structure loss (37% H3PO4) and the lowest surface roughness (10% HCl).

Tooth enamel properties and morphology after microabrasion: an in situ study

AIM

This study evaluated the effect of saliva on enamel after microabrasion with different microabrasive compounds under in situ conditions.

METHODS

Enamel/dentin blocks (16 mm² ) from bovine incisors were divided into nine groups (n = 19): one control group (no treatment), four groups treated with microabrasion using 35% phosphoric acid (H₃ PO₄ ) + pumice, and the last four groups treated with microabrasion using 6.6% hydrochloric acid (HCl) + silica. The treated groups were subdivided according to the in situ regimen: without salivary exposure, 1 h, 24 h, or 7 days of saliva exposure. Surface microhardness (SMH) and cross-sectional microhardness (CSMH) were tested. Scanning electron microscopy (SEM) was used to evaluate enamel morphology. Microhardness data were tested by analysis of variance, and Tukey's and Dunnett's tests (α = 0.05).

RESULTS

The SMH analysis revealed that all the microabrasion-treated groups presented significantly-reduced SMH values when compared to the control group (P < 0.05). Treatment with HCl + silica was more prone to the effect of saliva than H₃ PO₄ + pumice, even for CSMH analysis, once the superficial layers reached the same microhardness of that of the control group (P > 0.05). These results were confirmed by SEM, which demonstrated the mineral recovery effect over time.

CONCLUSION

Saliva was effective in promoting the rehardening of enamel after microabrasion, mainly for the surfaces treated with HCl + silica.