Comparison of effects of bleach and cleansing tablet on reflectance and surface changes of a dental alloy used for removable partial dentures.

Proper hygienic care of removable partial dentures is important for maintaining a healthy oral mucosa. A daily home care routine is the responsibility of the patient to maintain oral hygiene. A dentist must inform the patient about denture cleansers used for plaque control. Common denture cleansers may negatively affect the surface of alloys used to make partial dentures. The purpose of this study was to evaluate whether bleach and cleansing tablet have deleterious effects on the surface of a dental alloy used to fabricate removable partial dentures. Nineteen test specimens were prepared from CoCr dental alloy. The specimens were cast into 10 mm long x 10 mm wide x 1 mm thick. Fresh solutions made from a commercial bleach and a commercial cleansing tablet were used for each treating. Three groups (commercial denture cleansing tablet, bleach and tap water) were tested. Six specimens were immersed in 200 mL of tap water containing a single denture cleansing tablet. Two spoons of the commercial bleach was added to 200 mL of tap water. Seven specimens were treated. The control specimens were immersed in 200 mL of tap water. Six specimens were the control group. Each specimen was immersed for 30 min per day in the solution for a period of 30 days. The specimens were analyzed for reflectance with a spectrophotometer, for surface changes with a light microscope and weight which was measured with sensitive balance before and after treatment. The SPSS program was used for the statistical analysis. The Kruskal-Wallis Test and Wilcoxon Signed Ranks Test was used. No significant changes of reflectance was shown in the Kruskal-Wallis Test (p > 0.05). The Wilcoxon Signed Ranks Test was performed for comparison into groups. The difference between before and after treatment was statistically significant for the commercial denture cleansing tablet and the commercial bleach (p = 0.028) (p < 0.05). Reflectance was decreased after treatment. Within the limitations of this study, the commercial cleaning solutions had influenced the decrease of reflectance on the surface of the dental alloy. This solutions should not be limitlessly used on dentures with metal components, because they caused clinically significant reflectance changes on the surface of the alloy after 30 days.