LAUSR

AIM To compare the frequency of root filled teeth and quality of root fillings (RFs) in two parallel, Danish cohorts each examined over 10 years and to evaluate factors associated with apical periodontitis (AP) and extraction of root filled teeth. METHODOLOGY Two randomly selected cohorts (C1, C2) from Aarhus (age: 20-64 years), were followed for approximately 10 years, with full-mouth radiographic surveys performed at 5-year intervals (C1: 1997-2003-2008; C2: 2009-2014-2019). Frequency of root filled teeth, quality of RFs and coronal restorations, periapical status, and tooth extraction were registered. Logistic regression analyses compared C1 with C2 for baseline and follow-up periods and assessed variables associated with AP (PAI-based) and extraction of root filled teeth. RESULTS C1 included 330 and C2, 170 individuals, mean age 42.9 and 47.3 years, respectively, who attended all three radiographic examinations. The relative frequency of root filled teeth was lower in C2 than C1 at baseline (C1: 4.7%, C2: 3.6%; p<0.001) and after 10 years (C1: 5.7%, C2: 4.2%; p<0.001). The relative frequency of new RFs was lower in C2 compared to C1 (p=0.02). C2 had fewer short/long RFs at baseline than C1; quality of new RFs or coronal restorations was similar in C1 and C2. The risk of tooth extraction (p=0.93) and risk of AP (p=0.37) at 10-years follow-up was similar between the two cohorts. For both C1 and C2, root filled teeth with AP at baseline had increased risk of having AP (p<0.001) or having been extracted (p<0.001) at follow-up. Risk of extraction was higher for root filled premolars (p=0.01) and molars (p=0.01) than anteriors. Risk of AP at follow-up was higher for root filled molars (p<0.001). Furthermore, inadequate quality of RFs (p=0.02) and coronal restorations (p=0.04) increased the risk of AP at follow-up in C1 and C2. CONCLUSIONS The frequency of root filled teeth and new RFs decreased and little to no change in new RFs' quality, AP, or tooth extraction was seen over time (1997-2019). Root filled molars and teeth with AP at baseline had increased risk of AP and extraction.