Comparison of retention forces with various fabrication methods and materials in double crowns

PURPOSE: The purpose of this study was to analyze the retention force changes and wear behaviours of double-crown systems over long-term use. MATERIALS AND METHODS: Ten groups, each consisting of six samples, were evaluated. Specifically, casting gold alloy primary crown - casting gold alloy secondary crown (AA), laser sintering primary crown - laser sintering secondary crown (LL), casting Cr alloy primary crown - casting Cr alloy secondary crown, (CC) zirconia primary crown - electroformed secondary crown (ZA), and CAD/CAM titanium alloy primary crown - CAD/CAM titanium alloy secondary crown (TT) groups were evaluated at cone angles of 4° and 6°. The samples were subjected to 5,000 insertion-separation cycles in artificial saliva, and the retention forces were measured every 500 cycles. The wear levels were analyzed via SEM at the beginning and end of the 5,000 cycles. RESULTS: In all samples, the retention forces increased when the conus angle decreased. The highest initial and final retention force values were found in the LL-4° group (32.89 N-32.65 N), and the lowest retention force values were found in the ZA6° group (5.41 N-6.27 N). The ZA groups' samples showed the least change in the retention force, and no wear was observed. In the other groups, wear was observed mostly in the primary crowns. CONCLUSION: More predictable, clinically relevant, and less excursive retention forces can be observed in the ZA groups. The retention force values of the LL groups were statically similar to those of the other groups, except the ZA groups.

Complication rates and patient satisfaction with removable dentures

PURPOSE: The purpose of this clinical study was to evaluate the frequency and type of prosthetic complications in relation to type and properties of removable dentures and to investigate the influence of these complications and several data about the existing dentures on patient satisfaction. MATERIALS AND METHODS: Ninety nine patients (44 males and 55 females) wearing removable dentures have been included in the study. The complications of the patients were recorded; patient satisfaction was determined with a Visual Analog Scale (VAS) and the relationship of complications and patient satisfaction with several data about the dentures such as denture age, type of denture, centric relation and vertical dimension was investigated. Kruskal Wallis, Mann Whitney U and Chi square tests were used for statistical analyses. The results were evaluated statistically at a significance level of P<.05. RESULTS: Need for addition of artificial teeth for dentures with correct centric relations was found to be significantly lower than dentures with wrong centric relations (P<.01). Loss of retention, ulcerations and high vertical dimension affected the VAS chewing ability scores negatively and ulcerations affected the VAS phonation scores negatively (P<.05). CONCLUSION: Considering the results of this study, it can be concluded that loss of retention, ulcerations and high vertical dimension caused patient dissatisfaction. Additionally, dentures with wrong centric relations caused need for addition of artificial teeth.