Focus on leveling the hidden: managing impacted maxillary canines
Tooth impaction is defined as a condition in which the tooth remains embedded in the oral mucosa or intraosseous structures after its natural eruption. When a permanent tooth fails to erupt within one year after its physiological period, it is considered impacted. The long pathway that the canines take as they emerge into the maxillary arch makes them vulnerable to disruption during their natural emergence time, at the age of 11-12 years, and after the third molars, canines are the most frequently impacted teeth, with a frequency of 1-3%. Early detection and intervention, along with coordinated surgical and orthodontic treatments, can guide impacted maxillary canines (IMC) to a proper position in the dental arch. The traditional approach to orthodontic-surgical management of IMC typically involves the surgical exposure of the tooth, utilizing either the open exposure or closed exposure techniques, followed by the intraoperative bonding of an orthodontic button linked to a chain, which is then attached to the archwire of the fixed appliance. However, the actual procedure is much more complex. The process of planning treatment for IMC presents significant challenges, underscoring the need for careful consideration and expertise. Thus, the aim of the present article is to throw light on these complexities, by discussing clinical cases involving IMC, providing insights into the intricacies of their management. 

Localization of IMC position is essential for accurate orthodontic treatment as well as prognosis. The first step in managing IMC is accurate diagnosis, to determine the position and path of eruption of the canine, its effect on adjacent teeth, and the overall dental health of the patient. This involves clinical  and imaging examination. Clinical signs of IMC include delayed eruption of the canine, retention of the deciduous canine, absence of the labial bulge, presence of a palatal bulge, and tipping of the adjacent incisor. The absence of a canine bulge by age 11 might not always mean impaction. Palpating the alveolar process near the lateral incisor can help assess the canine’s position before it emerges. A missing labial bulge in 9- or 10-year-olds should raise concerns, leading to radiographic evaluations for a definitive diagnosis. The use of cone beam computed tomography (CBCT)  enables a more precise assessment of the exact position, and the intimate relation between the canine crown and the neighboring teeth is of special interest during orthodontic treatment planning for IMC, minimizing potential complications. In situations in which CBCT is not available at the dental practice, panoramic radiography  can aid in the localization of IMCs. 

The conventional method of orthodontic-surgical treatment of IMC consists in surgical tooth exposure, using the open exposure, a surgical procedure to reveal the tooth , followed by the direct bonding of an orthodontic attachment, which is connected to the arch of the fixed appliance or to the aligners. When the canine is located near the surface, the open exposure method is preferred. Conversely, closed exposure is employed to guide the movement of the tooth within the bone and gingival tissues without immediate exposure ( and ). For canines situated deeper within the bone, the closed exposure approach is more suitable. An inadequate exposure technique due to a lack of understanding or communication with the professional performing the exposure can lead to outcomes that complicate the traction phase. In , both canines were positioned too deep, and neither a chain nor a hook was used. For very deep cases, creating a perforation in the crown is a reliable method to prevent the need for a second surgical procedure. In , the canines were positioned close to the level of the gingiva, eliminating the need for sutures or closed exposure. In , the stainless steel wire was excessively thin and fractured during the initial traction process, requiring a second exposition. There is some evidence suggesting that there are no significant differences in outcomes between open and closed surgical exposures for IMC; however, the quality of this evidence is considered low. Additionally, the closed exposure technique is associated with a higher incidence of ankylosis, which occurs in 14.5% of cases, as opposed to 3.5% in the open exposure technique. Orthodontists commonly refer patients to oral surgeons or periodontists for the exposure and alignment of impacted teeth. Although these procedures might also be performed by other specialists, orthodontists have a legal responsibility for obtaining informed consent. It is recommended that orthodontists use an informed consent form to maintain ethical and legal diligence in such cases. 

The traction of palatally IMC is one of the greatest challenges of orthodontic treatment, and success depends on many factors: incisor overlap, vertical height, angulation, and apex position. In patients with IMC, no dental crossbite, and lack of space in the maxillary arch, maxillary expansion results in significant improvement of the sector in which the canine is positioned, and decreases the need for major orthodontic intervention in the long term, compared to extraction of deciduous canine or a wait-and-see attitude. Essential factors in the biomechanical strategies used in orthodontic movement of IMCs - such as the direction of applied forces, which may be light and continuous, the nature of anchorage, and the sequence of orthodontic movements - are fundamental to successful outcomes. The specific biomechanical approach can vary significantly, being individualized to the unique requirements of each case. There is a variety of orthodontic interventions for managing IMCs, ranging from non-intervention , interceptive treatments , extraction , maintenance of the deciduous canine , and autotransplantation. For palatally IMC, the recommended approach involves initially tractioning the tooth downward, followed by moving it toward the labial side. The multiloop arch with double helix is efficient for moving the canine to the occlusion line when it is positioned palatally and in crossbite, eliminating the necessity of a bite block . In contrast, for canines positioned labially, whether facing mesially or distally, the first step is to align the tooth within the dental arch, followed by vertical traction, to position it correctly in occlusion. When only a mesial or distal inclination correction is needed in the first phase, the use of temporary anchorage devices (TAD) provides more effective biomechanical control, and is particularly effective, as shown in . 

There are inherent uncertainties in treating IMC, such as variations in response to orthodontic forces, potential relapse, and patient-specific factors, like age and oral hygiene. These uncertainties demand a flexible and adaptive treatment approach, often individualized to the individual patient’s needs. Ankylosis is a potential complication in treating impacted canines. The risk increases with the age of the patient and the duration of impaction, the anatomic position of the canine’s root apex and its adjacent anatomic structures. The apicotomy surgical technique can be an effective option as an adjunctive treatment for ankylosed or dilacerated IMC after the failure of conservative orthodontics biomechanics , . The duration of the surgical/orthodontic treatment, ranging from 18 to 30 months, is a particularly troubling clinical problem, because it prolongs the orthodontic treatment duration. This is related to many factors, including: the patients’ age, the severity of dental crowding, the initial inclination of the IMC, the buccolingual IMC’s position, the distance from the occlusal plan and the periodontal health. The patient should be informed of the possibility of failure, a factor that, together with the increased treatment time, must be brought into the decision-making process from the outset. It is essential that patients -or their legal guardians, in the case of minors- are comprehensively briefed about the proposed treatment strategies, the associated risks, and the viable alternatives. Patient adherence to treatment protocols, particularly in the use of orthodontic devices such as elastics, is essential for achieving successful results. Moreover, maintaining optimal oral hygiene is critical to avoid periodontal issues and cavities, which can pose challenges due to the brackets and wires used in orthodontic treatments. Non-compliance by the patient can hinder the quality of the final outcome, as illustrated in . After replacing the maxillary canine with the reshaped first premolar, occlusal balance must be established, and the lateral guidance on the canine should be well-dimensioned. illustrates a gingival recession with cervical abrasion on the maxillary right premolar associated with improper brushing technique. 

Managing IMC often demands a multidisciplinary approach, involving collaboration among orthodontists, oral surgeons, and, in some instances, periodontists. This teamwork is important for complex cases in which surgical exposure, orthodontic alignment, and periodontal health must be concurrently managed to attain optimal aesthetic outcomes . 

After achieving successful alignment of an IMC, implementing long-term retention strategies is necessary to preserve tooth positioning and reduce relapse chances. The use of fixed retainers, when appropriate, plays a significant role in maintaining alignment. Additionally, scheduling routine follow-up visits is essential for evaluating treatment stability and efficiently managing any arising complications, thereby ensuring the effectiveness of the orthodontic treatment. 

In the treatment of IMC, early detection and preventive strategies are important. When tooth impaction occurs, a coordinated approach involving orthodontic treatment and surgical exposure is recommended for proper alignment, necessitating a synergistic effort between orthodontists and oral surgeons. IMC often is undiagnosed, due to the seemingly correct alignment of anterior teeth, leading to delayed orthodontic referrals until the eruption of second molars. The timing of intervention and the patient’s age are fundamental in influencing the success of treatment. Intervention during adolescence is advantageous due to the lower bone density and better orthodontic treatment response. The American Association of Orthodontists recommends early orthodontic evaluations to detect any dental problems, ideally by the age of 7, when enough permanent teeth are present for an assessment. Radiographic examinations are critical for early detection and to avoid complications such as root resorption. There are various methods to treat an ankylosed IMC, with luxation being the most common, despite its low success rate and associated risks. Surgical repositioning is an alternative, though it is less favored due to high morbidity. The last attempt is the apicotomy. The complexity and duration of orthodontic treatment for severe IMC underscore the importance of early detection to employ interceptive methods, which can prompt spontaneous correction and normal eruption of the IMC. The management of IMC often involves a prolonged treatment duration, emphasizing the need for diligent monitoring to ensure the health of the tooth and surrounding structures. The main complication arising from IMCs is adjacent teeth’s root resorption, which tends to stabilize long-term after correctly positioning the canine. While orthodontic treatment may have side effects such as mild discomfort and gingival recession, the advantages of successfully aligning an IMC, such as improved functionality, aesthetics, and prevention of further dental issues, are significant. 

Managing impacted maxillary canines (IMC) in orthodontics is complex, and requires accurate diagnosis, careful use of CBCT, and choosing between open and closed exposure methods. Understanding orthodontic biomechanics and being aware of risks like ankylosis and root resorption are crucial. Success also depends on teamwork across disciplines, considering patient-specific factors, and clear communication about possible side effects. Coordination with the professional performing the canine exposure is essential. 

