# Factors Contributing to Complications and Failures of Impacted Canines Undergoing Surgical Orthodontic Treatment: A Retrospective Cohort Study

## TL;DR

This study identifies factors that increase the risk of complications and failure in treating impacted canines with surgery and orthodontics.

## Contribution

The study provides new insights into anatomical and procedural risk factors for treatment failure in impacted canine eruption.

## Key findings

- Central crown position and proximity to a cortical plate increase treatment failure rates.
- Lateral incisor root resorption is a significant predictor of treatment complications.
- Open surgical exposure improves eruption success but increases gingival complications.

## Abstract

Objectives: This study aims to assess the prevalence of complications and failures associated with impacted canine eruption in a specialized referral center, with the goal of identifying factors that contribute to these outcomes. Methods: This retrospective cohort study included cases of impacted canines treated at the School of Dental Medicine between 2010 and 2020. Clinical and radiographic data were collected and evaluated for failures and complications by two independent clinicians (MK, MG). In addition, specialists in oral and maxillofacial surgery and orthodontics (YM, TS, NS) independently assessed all complications and failures. Results: Among the 214 impacted maxillary canines included, 23 (10.7%) failed to erupt following initial surgical–orthodontic treatment and required re-intervention. Eruption difficulty was attributed to orthodontic factors in 43.5% of cases, surgical factors in 13.0%, and combined factors in the remainder. Following a second procedure, 15 canines erupted successfully, while 8 did not, resulting in an overall failure rate of 3.7%. Treatment failure was significantly associated with both anatomical and procedural factors. Canines with centrally positioned crowns exhibited a significantly higher failure rate than those with buccal or palatal positions (χ2 test, p = 0.025). Failure was also more common when the canine root apex was located in close proximity to a cortical plate. Lateral incisor root resorption was significantly associated with treatment complications (p = 0.030). In the multivariable logistic regression analysis, root resorption remained an independent predictor of treatment failure, increasing the odds of failure approximately fourfold (OR = 0.255, CI = 0.077–0.843, p = 0.025). Timing and surgical technique were also significantly associated with treatment outcome. Surgical exposure performed shortly after diagnosis was linked to an increased risk of treatment complications (p = 0.006). Closed surgical exposure demonstrated a significantly higher failure rate compared with open exposure (Pearson exact test, p = 0.009). Although open exposure was associated with a greater likelihood of successful eruption, it was also significantly associated with increased gingival morbidity (Fisher’s test, p = 0.030). Conclusions: Failure of impacted maxillary canine eruption following combined surgical–orthodontic treatment is uncommon but is significantly associated with distinct anatomical and procedural risk factors. Central crown position, cortical plate involvement, lateral incisor root resorption, early surgical exposure, and the use of closed exposure techniques all increase the likelihood of treatment failure and complications. Although open exposure enhances the probability of successful eruption, it may also negatively affect gingival outcomes, underscoring the need for individualized, multidisciplinary treatment planning.