Alginate impressions for fixed prosthodontics. A 20 year follow up study

The aim of this study was to estimate whether the survival ratios after 20 years of fixed prosthodontics made of alginate impressions was higher, equivalent or lower, compared to the survival ratios, shown in studies, where different impression materials were used. 151 females and 104 males were screened regarding the condition and age of the restorations at the annual check-up in one of the author's surgeries. Average ages were 55 and 54 years respectively, when the fixed prosthodontics were seated. A total of 1.271 units were produced during the twenty years, 911 abutment teeth and 360 pontics. The type of prosthetic work was divided into three groups: 1) larger fixed prosthodontics 6-14 units (469), 2) smaller fixed prosthodontics 2-5 units (541) and 3) single crowns (261). The results show that alginate impressions can produce fixed prosthodontics with survival ratios similar to those presented in other studies, after 5 years (99%), 1o years (93-96%) and 15 years (74-96%). After 20 years the survival ratio was 61-63%. In conclusion, fixed prosthodontics made according to the syringe-tray alginate impression method may have the same success rates after 20 years compared to that of fixed prosthodontics presented in previous longitudinal clinical studies where other impression materials had been used. In this study, caries and root fractures were the main reasons for removing abutment teeth and pontics.