ABSTRACT
Statement of the Problem: Although all-ceramic restorations are broadly used, there is a lack of information concerning how their fit is affected by fabrication procedure and marginal configuration
Purpose: The purpose of this study was to evaluate the marginal fit of zirconia CAD/CAM ceramic crowns before and after porcelain firing. The influence of finish line configuration on the marginal fit was also evaluated
Materials and Method: Twenty standardized zirconia CAD/CAM copings were fabricated for chamfer and shoulder finish line designs [n=10]. The marginal fit of specimens was measured on 18 points, marked on the master metal die by using a digital microscope. After the crowns were finalized by porcelain veneering, the measurements of marginal fit were performed again. The means and standard deviations were calculated and data were analyzed using student's t-test and paired t-test [alpha=0.05]
Results: There were significant differences between marginal fit of chamfer and shoulder finish line groups before and after porcelain firing [p= 0.014 and p= 0.000, respectively]. The marginal gap of copings with shoulder finish line was significantly smaller than those with chamfer configuration [p= 0.000], but there were no significant differences between the two marginal designs, after porcelain firing [p= 0.341]
Conclusion: Porcelain veneering was found to have a statistically significant influence on the marginal fit of zirconia CAD/CAM crowns. Both margin configurations showed marginal gaps that were within a reported clinically acceptable range of marginal discrepancy
ABSTRACT
Statement of the Problem: Implant-retained overdenture can improve the stability of dentures and prevent bone loss. Overdenture-wearing patients need special hygiene care
Purpose: The aim of this study was to evaluate the effects of various denture cleansers on the retention of Dio orange O-rings
Method and Materials: In this experimental study, 40 Dio orange O-rings were divided into 4 groups [10 O-rings each] and each group was soaked for equivalent of 6 months in the following solutions: 5.25% NaOCl [1:10 dilution], Corega cleanser tabs, Professional cleanser tabs and water [as the control group]. After 6 months, O-rings were tested for 2inch/minutes of tensile force. The peak load-todislodgement was recorded. Data were imported to SPSS18 and were analyzed by One-Way ANOVA and Tukey HSD test [p
Results: Denture cleansing solutions have significant effects on the reduction of retentive value of O-rings [p
Conclusion: This in-vitro study demonstrated that the retention of O-rings was affected when soaked in cleansing solutions. NaOCl caused more reduction in retentive value compared to effervescent cleansers and would not be recommended for cleansing O-rings. These results should be interpreted clinically and the role of other factors in the retention of O-rings should be considered in order to recommend the best cleanser for O-ring overdentures