Zirconia ceramic surface alterations following toothbrushing with different dentifrices
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Toothbrushing with toothpaste is the most commonly practiced oral hygiene procedure. However, regular toothbrushing has been considered an etiological factor in gingival recession and tooth wear. It is also one of the factors that might affect the surface texture of the materials inside the patient's mouth, such as creation of surface alteration. This in vitro study aims to evaluate the surface morphology of toothbrushed zirconia surfaces. Furthermore, the physical and mechanical effects of different abrasivity of toothpastes on zirconia were investigated. Methods: Zirconia was provided by the manufacturer as discs of 100 mm x 16 mm (Zirlux FC ®, FCZ 101, Ivoclar Vivadent). Each disc was sectioned into specimens of 12.14 mm x 18.09 mm, 1 mm thickness. Specimens were then divided into 6 groups with 8 samples each. In the first group, which was the control, specimens were brushed with water. The other 5 experimental groups were brushed with different types of dentifrices. All the baseline readings and measurements were recorded before the brushing procedure. Four of the toothpastes in this study were commercial products and are typical of products widely available in many countries. Included in the study was a polishing toothpaste called Proxyt (Ivoclar Vivadent). These pastes are used for the removal of light plaque and polishing in office. The simulated toothbrushing (Sabri Dental, Illinois) machine was set at 300 cycles / 3 minutes. This was to mimic the clinical use equal to 1 year, with 73,00 cycles, and 3 years with 21,900 cycles. Before and after brushing, the surface gloss (Gl) with a glossmeter was measured. Two tests were used to evaluate the surface characteristics: one qualitative (surface reflectance) and one quantitative, in which the profilometry was used. SEM (Hitachi, S-3400N) was used to evaluate the specimens before and after toothbrushing. The pH of the slurry before and after 7300 cycles of brushing was measured. Before and after simulated toothbrushing, the contact angle of the water on zirconia surfaces was measured using VCA Optima XE, Ivoclar. The statistical analysis was performed. The data for gloss changes, contact angles, and surface roughness were analyzed with a paired parametric t- test. The level of statistical significance was set at P< 0.01. To differentiate between toothpaste used in the study, one- way ANOVA analysis with post hoc Tukey was used. The level of statistical significance was set at P< 0.05. Results: This study showed that: 1) Except for the control group, the surface gloss of zirconia surfaces in all toothpastes groups was significantly increased by simulated toothbrushing (P < 0.01). 2) The profilometry showed no statistically significant difference in the mean roughness before and after brushing in all groups. 3) in the SEM pictures and surface plots, the surface looked smoother after three years brushing with some variation between the groups. Conclusion: Within the limitations of this study: * Zirconia became smoother and glossier after three years brushing while there was no change in the surface roughness regardless of the pH of the slurry. * The surfaces that were brushed with each type of toothpastes showed overall increased hydrophilicity. Thus, the surface wettability can be maintained by toothbrushing.