Comparison of Fluoride Release in Conventional Glass-Ionomer Cements with a New Mechanical Mixing Cement.

PURPOSE: The aim of this paper was to compare three conventional hand mixing glass-ionomer cements (GICs) and a new mechanical mixing glass-ionomer cement. MATERIALS AND METHODS: Samples were measured on days 1, 2, 6, 10, 31, 90 and 180. After 32 and 181 days of monitoring, the samples were recharged by using 1 ml of 2% sodium fluoride gel. RESULTS: The fluoride release started in high concentration during the first day for all GICs, with a value for GIII of 32.6 ppm. From the 2nd day, a slow, steady decline, with the exception of GII, which showed a marked decline to a value of 3.2 ppm. Analysis of variance (ANOVA) test showed statistically significant differences between the amounts of fluoride of the four materials in the first 24 h. Student t test was used to compare the fluoride release between the first and second recharge in each one of the study groups. Statistically significant differences were found when we compared the fluoride release in groups I (t = -16.95, p = 0.000) and IV (t = -2.644, p = 0.26). CONCLUSIONS: A mechanical mixing was the material with the more constant fluoride release and after recharge showed the highest fluoride release which make it an important benefit for clinicians.

Effect of airborne-particle abrasion and, acid and alkaline treatments on shear bond strength of dental zirconia.

The surface roughness, morphology and shear bond strength (SBS) of dental zirconia using three different surface treatment techniques were evaluated. Three groups of sintered zirconia blocks were treated as follow, 1) Airborne-particle abrasion (APA) group (G1-APA), 50-µm Al2O3; 2) APA and 9% hydrofluoric acid etching (G2-HF); 3) APA and Sodium Hydroxide (G3-NaOH). The specimens were evaluated for roughness [atomic force microscope (AFM)], morphology [Scanning Electron Microscope (SEM)] and for SBS in the universal testing machine. The AFM revealed changes in the roughness after the surface treatments, however there was not Ra difference between groups, SEM analysis revealed changes in surface morphology for all surface treated specimens. For SBS, significant difference was found between G1-APA=8.4±2.7 MPa and G2-HF=3.3±0.6 MPa (p<0.05) and G2-HF and G3-NaOH=9.0±3.0 MPa (p<0.05). The main fracture mode was mixed failure (63%) for G1-APA and G3-NaOH groups. G2-HF showed 100% adhesive failure. SBS was improved with NaOH, however application of HF significantly decreased SBS.