The aim of this study was to examine the technical quality of root canal fillings performed in a dental school and to investigate the associated effect on the survival/retention of root-filled teeth. A review of case notes of patients who had root canal treatment performed in the department of Restorative Dentistry, University Dental School and Hospital, Cork, Ireland was carried out. The technical quality of the root canal filling was described according to its relationship with the radiographic apex on a post-treatment radiograph. Tooth status at review was defined as 'tooth present' or 'tooth absent' based on the presence or absence of the root-filled tooth recorded in the treatment records at a review appointment following placement of the root canal filling. One hundred and forty-eight teeth (129 patients) were considered. Of these, 69.6% (n = 103) were of acceptable technical quality, 23.6% (n = 35) were under-extended, and 6.8% (n = 10) were over-extended. An increased number of intra-treatment radiographs to confirm the relationship of the canal preparation to the radiographic apex and operator experience were significant predictors of adequate root canal fillings (P < 0.05). Eighty-three per cent (n = 123) of teeth were present at a review appointment held an average of 40 months following completion of treatment (12-60 months). The technical quality of the root canal filling was the only significant factor in predicting tooth survival (P < 0.05), while the presence of pre-treatment periapical pathology had no significant effect on survival of the root-filled tooth. Determination and maintenance of the working length of the canal system is an important feature in producing good quality root canal fillings, which in turn, is associated with increased likelihood of survival/retention of root-filled teeth.