This case-series study examined canal morphology and common factors for endodontic
failure in maxillary first and second premolars that were referred for retreatment
owing to clinical symptoms or radiographic signs.
Records were retrospectively searched using Current Dental Terminology codes to identify
maxillary first and second premolars with endodontic failure. Periapical and cone-beam
computed tomographic images were examined to determine Vertucci classifications and
suspected factors related to treatment failure.
A total of 235 teeth from 213 patients were included for evaluation. The following
Vertucci classification of canal configurations were observed for maxillary first
and second premolars: type I (1-1) (4.6% and 32.0%, respectively), type II (2-1) (15.9%
and 27.9%, respectively), type III (2-2) (76.1% and 36.1%, respectively), type IV
(1-2) (0% and 2%, respectively), and type V (3) (3.4% and 2%, respectively). More
treatment failures were noticed in maxillary second premolars than first premolars
and in females than in males. The 4 most common factors related to failure were inadequate
filling, restorative failure, vertical root fracture, and missed canals. Missed canals
were more frequently identified in maxillary second premolars (21.8%) than first premolars
(11.4%) (P = .044).
Multiple factors are associated with primary root canal treatment failures in maxillary
premolars. Variations in canal morphology appear to be underappreciated in maxillary
Maxillary second premolars have more complicated canal configurations than first premolars.
Besides adequate filling, clinicians should give extra attention to anatomic variability
in second premolars owing to higher failure incidence.