Elsevier

International Orthodontics

Volume 18, Issue 3, September 2020, Pages 480-489
International Orthodontics

Original Article
Inter-premolar width changes related to the orthodontic traction of maxillary impacted canines in adolescents and young adults: A retrospective CBCT study

https://doi.org/10.1016/j.ortho.2020.03.006Get rights and content

Summary

Objective

Maxillary canine impaction is directly associated with a narrow maxillary arch, mainly in the inter-premolar widths. This study compared the transverse changes at the level of maxillary premolars after traction of maxillary impacted canines (MICs) in adolescents and young adults through three main goals: to compare unilateral versus bilateral cases, to compare buccally versus palatally MIC cases, and to compare the affected versus non-affected side exclusively in the unilateral group.

Methods

This before and after CBCT study involved 45 MIC orthodontically tractioned until the occlusal plane with a standardized protocol. The sample was classified regarding the impaction type (unilateral versus bilateral), impaction location (palatal versus buccal) and the affected versus unaffected sides in the unilateral cases. MIC characteristics as impaction sector, height, and complexity of the traction, as well as α and β angles, canine root length and area were measured. Moreover, cephalometric characteristics were also evaluated. Mann-Whitney U or Wilcoxon signed-rank tests and multiple regressions were applied (α = 0.05).

Results

Maxillary inter-premolar widths (first or second) expanded approximately 3 mm after traction of unilateral or bilateral MIC (P > 0.05). Changes in hemi-arch widths between palatal (1.67 mm) versus buccal (1.90 mm) MIC were similar (P > 0.05). In unilateral impaction, the transversal changes on the affected side were 2 mm versus almost 1 mm observed in the unaffected side (P < 0.05). Finally, the multiple linear regressions were identified to the ANB angle, the impaction sectors and the distance from middle raphe to the cusp tip of MIC as influential variables.

Conclusion

The maxillary inter-premolar widths increase after traction of MIC without differences between type or location of impaction. In addition, the transverse change in the affected side in unilateral MIC is greater than the unaffected side resolving the earlier transverse asymmetry.

Introduction

There are two main theories to explain the palatal maxillary canine impaction [1], [2], [3]. The first one, the eruption guide theory, associates the lateral incisor root as a key factor to guide the permanent canine eruption; therefore, any alteration in this root could lead to a loss of the eruption pathway of the maxillary canine. The second theory suggests that genetics explains the inadequate dental germ location as an inherited way. Otherwise, for the buccal maxillary canine impaction the most accepted theory is the lack of space for the canine eruption in the maxillary arch because the canine is one of the last teeth to erupt, followed by second and third molars [4], [5]. However, once the canine impaction has occurred, consequences will be generated in the dental arches and these could affect the dentoalveolar development and the smile attractiveness.

One of the consequences of this maxillary canine impaction is the lack of transverse development of the maxillary arch, mainly in the interpremolar widths [6]. For this reason, nowadays the prevention treatments of maxillary impacted canines (MIC) attempt the dental expansion in the upper arch achieving high success percentages [7], [8], [9]. Likewise, in cases of unilateral MIC, the distances from the middle raphe to the cusps of premolars on the affected side are decreased regarding the unaffected control side [10]. This lack of transverse development is a consequence of the absence of the stimulus in the eruption of the maxillary canine that increases the canine eminence and consequently the width of the hemiarch mainly at the premolar level [6], [10].

The traction of MIC allows the recovery of the canine guidance and its implications in obtaining a functional occlusion, efficient for chewing, and tends to be more frequently observed during the complete excursion [11], [12]. Moreover, it also allows the achievement of aesthetics of the canine eminence and consequently, the harmony in the smile [13], [14]. Also, the symmetry in the smile is a critical factor that must be met when finishing the orthodontic treatment. This latter condition allows the patients and orthodontists to obtain a symmetric observation of the negative spaces and adequate buccal corridor size with its positive clinical implications [15], [16]. Therefore, it is important to correct the inter-premolar width asymmetry in these cases with canine impaction.

The orthodontic treatment with conventional or self-ligating brackets generally produces an increase in interpremolar width between 2 mm to 3 mm when arches are coordinated [17], [18], [19], and when the clinics use broad arch wires an increase between 3 mm to 5 mm was achieved [20], [21], i.e. it is almost always expansive and when it was evaluated in the long term did not show any statistically significant relapse, though showing a tendency to restriction, especially for the premolars [22]. The knowledge that the traction of MIC with different impaction condition allows correcting the altered transverse dental dimension mainly at premolars level [6], [10], can be helpful for orthodontists to propose a treatment to correct this transverse deficiency, and that benefits the smile aesthetics of the patients.

Therefore, this study had three main objectives:

  • to compare the transverse changes at the level of maxillary premolars after traction of unilateral versus bilateral MICs in adolescents and young adults;

  • to compare the transverse changes at the level of maxillary premolars after traction of MICs located in buccal versus palatal position;

  • and to compare the transverse changes at the level of maxillary premolars after traction of unilateral MICs between the affected and non-affected side.

Finally, this paper tries to test the null hypotheses that there is no significant difference in the interpremolar width changes after traction of unilateral versus bilateral MICs neither when they have a different position, nor between the affected or unaffected side, this latter comparison specifically in unilateral impactions.

Section snippets

Materials and methods

This retrospective study with before and after design was approved by the Ethics and Research Committee of the Científica del Sur University with approval code No. 00006 and by the Research Commission of Dentistry Faculty of the Federal of Rio Grande do Sul University (UFRGS) under the number 33610. The sample involved 45 consecutive MICs orthodontically tractioned until the occlusal plane, treated with a standardized protocol by one experienced and trained orthodontist (G.A.R.M.) at two

Results

Table I describes the initial characteristics of the sample. The changes in the maxillary premolar-widths (first and second) after impacted canine traction did not show significant differences between unilateral versus bilateral impactions (P = 0.917, P = 0.724 respectively), such changes in both groups were approximately 3 mm (table II). When changes in hemi-arch widths between palatal versus buccal and bicortical MICs were compared, no significant differences were found (at the level of first

Discussion

The orthodontic treatment is frequently expansive using conventional or self-ligated brackets, this expansion in the premolars-width ranges between 2 to 5 millimeters [17], [18], [19], [20], [21]. Nevertheless, these inter-premolar width changes after traction of MICs have not yet been evaluated in the scientific literature. These modifications could produce different results regarding conventional orthodontic treatments because the MICs present different types and positions in the alveolar

Conclusions

The maxillary premolar expansion occurs after traction of MIC without differences between impaction type (unilateral or bilateral) or impaction location (palatal versus buccal). Moreover, in unilateral MIC condition the inter-premolar width changes in the affected side are greater than in the unaffected side allowing resolving the earlier transverse asymmetry.

Disclosure of interest

The authors declare that they have no competing interest.

References (42)

  • A. Lucchese et al.

    Transverse and torque dental changes after passive self-ligating fixed therapy: a two-year follow-up study

    Am J Orthod Dentofacial Orthop

    (2019)
  • L.E. Arriola-Guillen et al.

    Influence of impacted maxillary canine orthodontic traction complexity on root resorption of incisors: a retrospective longitudinal study

    Am J Orthod Dentofacial Orthop

    (2019)
  • L.E. Arriola-Guillen et al.

    Root resorption of maxillary incisors after traction of unilateral vs bilateral impacted canines with reinforced anchorage

    Am J Orthod Dentofacial Orthop

    (2018)
  • C. Steiner

    Cephalometrics for you and me

    Am J Orthod

    (1953)
  • Y.H. Kim et al.

    Anteroposterior dysplasia indicator: an adjunct to cephalometric differential diagnosis

    Am J Orthod

    (1978)
  • M.L. Moss

    The functional matrix hypothesis revisited. 2. The role of an osseous connected cellular network

    Am J Orthod Dentofacial Orthop

    (1997)
  • F. Amini et al.

    Associations between occlusion, jaw relationships, craniofacial dimensions and the occurrence of palatally-displaced canines

    Int Orthod

    (2017)
  • F. Ghaffar et al.

    Association between maxillary transverse discrepancy and occurrence of potentially impacted maxillary canines in mixed dentition patients

    Int Orthod

    (2019)
  • L.E. Arriola-Guillén et al.

    Influence of maxillary canine impaction characteristics and factors associated with orthodontic treatment on the duration of active orthodontic traction

    Am J Orthod Dentofacial Orthop

    (2019)
  • T. Baccetti

    A controlled study of associated dental anomalies

    Angle Orthod

    (1998)
  • G. Richardson et al.

    A review of impacted permanent maxillary cuspids—diagnosis and prevention

    J Can Dent Assoc

    (2000)
  • Cited by (5)

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