Interventions for impacted maxillary canines: A systematic review of the relationship between initial canine position and treatment outcome.

Background: The objective of this review was to critically assess the existing literature on the relationship between the initial position of impacted canines and treatment outcomes.

Methods: We performed a systematic review of the available literature until February 2020 using the MEDLINE, Cochrane Central, Web of Science and PubMed databases. Prospective and retrospective studies (randomized controlled trials [RCTs], cohort studies, longitudinal follow-up studies) considering impacted maxillary canines that were orthodontically and/or surgically treated, and clearly reporting the initial position using 2D and/or 3D classifications, were included if they assessed at least one of the following: treatment success, treatment duration, number of treatment visits, radiographic outcome, periodontal health, esthetics and/or treatment complications. The included studies were assessed for risk of bias according to the Cochrane guidelines.

Results: Seventeen studies were reviewed (2 RCTs and 15 non-RCTs). The included studies enrolled a total of 1247 patients with an average age of 14.1 years and a total of 1597 impacted canines. Various causal relationships were detected between the success of treatment modalities and the initial state of the impacted canine (bucco-palatal position, vertical position, canine angulation, root development).

Discussion: Evidence, though limited, suggests that a higher alpha angle, higher vertical position and more mesial sector of the impacted canine are related to less successful interceptive and active treatment solutions, prolonged treatment time and inferior outcomes.