Aim: The aim of this study was to determine the prevalence and frequency of apical periodontitis and root fillings in 450 institutionalized Indian elderly population. Methodology and Results: The teeth with apical periodontitis were assessed using the Periapical Index (PAI) score. A total of 942 teeth were evaluated in 98 subjects (57 females and 41 males) with mean age of 74 years. The observed frequency of total edentulous subjects was high (76%) in this population. A total of 126 teeth showed root fillings, of these only 46 (36.5%) were scored as having adequate quality. Apical periodontitis was found in 114 teeth (12.1%) in 42 (42.9%) subjects. 80 (70.2%) inadequate root-filled teeth showed apical periodontitis. There was a significant correlation between the presence of periapical pathology and inadequate root-filled teeth. Inadequate root-filled teeth were associated with an increased prevalence of apical periodontitis in these subjects. This fact may result in increased endodontic retreatment needs for this population. Conclusion: In conclusion, based on the data of the present study, inadequate root filling was associated with an increased prevalence of AP in the institutionalized elderly population. This fact may result in a greater demand for endodontic treatment in this population.