Dental Changes Following the Traction of Impacted Maxillary Canines

Overview

The impaction of maxillary canines is a challenge for orthodontists. Recently, new methods have been proposed to accelerate canine withdrawal. The associated dental changes between the conventional and accelerated methods of canine traction have not yet been assessed.

Impacted canines are defined as those that have not erupted within 6 six months after completing the formation of their roots or that were not present within the dental arch during their eruption phase. Upper Impacted canines are present in 2% of the general population and occur in females at a rate of 1.17%, which is almost twice the incidence in males. The incidence of palatal impaction ranges from 60% to 80% and is present bilaterally with a rate of 75-95%. The upper canines usually erupt at an average age of 10.5 years in females and 11.5 years in males, with an individual difference of 3-4 years. Eruption failure of the upper canines occurs because of hard or soft tissue obstructions or an abnormal eruption pathway. The most important causes of palatally impaction of upper canines are dental arch length deficiency, over-retained primary teeth, and trauma during the canine formation stage. One local mechanical cause is a decrease in the width of the upper dental arch. McConnell et al. reported that patients with upper impacted canines had a reduction in dental arch width, especially in the anterior region. On the other hand, unilateral or bilateral upper canine impaction can affect upper dental arch width and alter smile symmetry. The impaction of the upper canine is also considered as one of the causes that lead to a lack of transverse development of the maxillary dental arch, especially the inter-premolar width. This is supported by the functional matrix theory, which considers that the presence of the organ stimulates bone growth. Thus, the natural eruption of the canine stimulates the normal transverse growth of the dental arch. Many treatment strategies were used to treat impacted canine cases, but orthodontic traction after surgical exposure was the most commonly recommended method in the literature, given the great aesthetic and functional value of the upper canines. Two main surgical methods are used for this purpose: the open and closed surgical approaches. Several mechanical means have been used to obtain the traction force. However, choosing the appropriate mechanical method that produces the least undesirable effects on adjacent teeth was a challenge for the clinical practitioner. Many factors could result in unwanted changes in the spatial position of the adjacent teeth, such as the use of an open coil spring, direct reliance on these teeth to tract the impacted canine, the type of baseline orthodontic archwire used, and the type of orthodontic anchorage means. These side effects on adjacent teeth can be minimized by using techniques such as the segmented archwire technique and temporary anchorage devices (TADs).

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