Langzeitbewährung von in klinischen Behandlungskursen durchgeführten prothetischen Versorgungen mit Doppelkronen Eine retrospektive Qualitätsanalyse

Double crown-retained removable dentures are one of the most common treatment options for partially edentulous patients in Germany. The aim of this retrospective study was to evaluate the survival rates of double crown-retained dentures and the corresponding abutment teeth. The aspects examined included parameters influencing survival of double crown-retained dentures and abutment teeth. It was hypothesized that number and endodontical state of the abutment teeth have a significant influence on survival probability and that patients gender and age as well as jaw location of the denture do not have an impact. Furthermore, type and number of follow-up treatment measures were assessed. The data of 559 patients who had been treated with 759 double crown-retained dentures on 2145 abutment teeth based on the Marburg double crown system was analysed. All dentures were inserted between 1990 and 2016 in clinical student courses under strict supervision of experienced dentists in the Department of Prosthodontics at the University of Marburg. The mean observation period was 4.2 years and ranged from 1-26 years. Survival analysis was performed using the Kaplan-Meier method and multivariate Cox-Regression. During the observation period 14.8% of the double crown-retained dentures lost their function and 7.5% of the abutment teeth were extracted. The corresponding 5-year survival rates were 88% for dentures and 92% for abutment teeth, respectively. The hypothesis that the survival rates correlate with the number of abutment teeth per denture can be accepted. Significantly better survival probability was observed for a higher number of abutment teeth. The 5-year survival rates for double crown retained dentures were 66%, 88%, 92% and 97% for dentures with one, two, three and four or more abutment teeth, respectively. For abutment teeth the 5-year survival rate was 85% for one abutment with two, three and four or more abutments having survival rates of 88%, 89% and 96% after five years. The hypothesis that the patient´s age and gender as well as the jaw location of the denture do not affect the long-term success has to be partially rejected.  Survival rates for dentures and abutment teeth were found to be significantly higher in younger patients. However, gender and jaw location of the denture did not correlate with survival rate. Vital abutment teeth showed significantly higher success rates compared to endodontically treated abutment teeth. Therefore, the hypothesis that the endodontic state of the abutment teeth impacts their survival time can be accepted. Double crown-retained dentures required a large amount of follow-up measures with 75.0% of the dentures and 23.3% of the abutment teeth needing at least one follow-up treatment measure during the period of function. Most follow-up treatment measures were comparatively simple and therefore, quick and cost-effective. The most common follow-up treatment measures for dentures were removal of pressure spots, occlusal corrections and relining. For abutment teeth recementation of primary crowns was the most common measure, followed by repair of facings and treatment of fractured abutment teeth. The findings of this study show that oral rehabilitation with double crown-retained removable dentures is a viable longterm treatment option for partially edentulous patients. The survival rates found in this study were mostly comparable to those reported in the literature. Initial treatment with double crowns is more complex and expensive than treatment with clasp-retained removable partial dentures however, costs and effort for follow-up treatments and after loss of abutment teeth are considerably lower for double crown-retained removable dentures.