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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 52  |  Issue : 1  |  Page : 12-16

A cone beam computed tomography-based evaluation of root length and the frequency of its dilaceration in impacted mandibular canines: A retrospective study


1 Prof, Department of Orthodontics, PDMDCRI, Bahadurgarh, Haryana, Uttar Pradesh, India
2 Senior Consultant, Department of Radiology, BRD Medical College, Gorakhpur, Uttar Pradesh, India

Date of Submission22-Apr-2017
Date of Acceptance02-Nov-2017
Date of Web Publication18-Jan-2018

Correspondence Address:
Dr. Shikha Jain
Flat No. 105, Vasudha Apartments, Rohini, Sector 9, New Delhi - 110 085
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jios.jios_1_17

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  Abstract 

Objective: The aim of this investigation was to evaluate root length and the frequency of its dilaceration in impacted mandibular canines. Materials and Methods: This retrospective, observational, split-mouth study evaluated cone-beam computed tomographic scans of the mandibular dentition of 27 individuals (mean age: 15.7 ± 1.9 years standard deviation) with unilaterally impacted permanent mandibular canines. While unilaterally impacted mandibular canines formed the impaction group (IG), the homonym completely erupted mandibular canines formed the control group. The two groups were compared for the mean root length and the frequency of root dilaceration of the mandibular canines. This was done using paired t-test and Chi-square test (or Fischer's exact test), respectively. Results: The mean root length of the impacted canines was significantly shorter than the homonym teeth (P < 0.05). The incidence of dilaceration was significantly higher in IG (P < 0.05). Conclusion: According to the results of this study, impacted permanent mandibular canines demonstrate developmentally shorter roots and higher incidence of root dilaceration in contrast to the completely erupted homonym canines.

Keywords: Dilaceration, impacted mandibular canine, root length


How to cite this article:
Jain S, Agrawal V. A cone beam computed tomography-based evaluation of root length and the frequency of its dilaceration in impacted mandibular canines: A retrospective study. J Indian Orthod Soc 2018;52:12-6

How to cite this URL:
Jain S, Agrawal V. A cone beam computed tomography-based evaluation of root length and the frequency of its dilaceration in impacted mandibular canines: A retrospective study. J Indian Orthod Soc [serial online] 2018 [cited 2018 Aug 16];52:12-6. Available from: http://www.jios.in/text.asp?2018/52/1/12/223648


  Introduction Top


Successful orthodontic treatment of impacted teeth requires extensive knowledge and appreciation of possible accompanying root anomalies. A variety of developmental factors such as abnormal root length and dilaceration might complicate this type of treatment. Hence, the orthodontist must be very careful when devising the treatment plan and this will require a thorough radiographic examination in addition to the routine clinical examination. Conventionally, the radiographic diagnosis was based on two-dimensional (2D) images. However, 2-D images can be hindered by rotation, distortion, and errors in head positioning causing poor visualization of some anatomic structures. Cone beam computed tomography (CBCT) has been recently introduced in radiographic diagnosis of impacted teeth since it provides 3D information of various structures of interest. This allows for exact assessment of the root apex location and root length; and detection of root dilaceration if any. The advantages of CBCT over conventional computed tomography include low radiation dose, low cost, excellent tissue contrast, elimination of blurring, and overlapping of adjacent teeth and high spatial resolution.[1],[2] This makes the application of CBCT increasingly indispensable in the diagnosis and treatment of impacted teeth.

Studies on impacted mandibular canines were mainly found as case reports, most of which were limited in scope because of sole reliance on 2D radiographic images.[3],[4] In addition, impacted mandibular canine has not yet been evaluated for the length and dilaceration of its root. Therefore, the aim of this retrospective study was to analyze root length and the frequency of its dilaceration in impacted permanent mandibular canines; using 3D CBCT scans of the mandibular dentition.


  Materials and Methods Top


Following the approval of the Institutional Ethical and Review Board (dated December 22, 2012; protocol No. PCDS/Acad./2012-13/3820); a retrospective, observational, split-mouth study was undertaken at the Department of Orthodontics, People's College of Dental Sciences, India. This study was designed in accordance with the Declaration of Helsinki (2012–2013) and STROBE guidelines. We selected 27 Indian subjects (mean age 15.7 ± 1.9 standard deviation; males: females, 1:2) with unilaterally impacted mandibular canine who presented either to the orthodontic department in the above mentioned dental college or to any of the private practices in the city of Bhopal, between September 2013 and September 2015. The inclusion criteria were subjects with (1) full clinical documentation including medical and dental history, (2) presence of unilaterally impacted mandibular canine, defined so (a) if it was unerupted and showed radiographic evidence of complete root formation,[5] (b) if it was identified to be prevented from erupting either by a physical barrier or because of its orientation in a position other than vertical within the alveolus,[5] and/or, (c) when it remained in the jaw 2 years after the expected mean age of its eruption;[6] and (3) CBCT of mandibular dentition taken for the purpose of evaluation of impacted mandibular canine that was previously detected by panaromic and periapical radiographs, (4) homonym canine completely erupted. Specifically excluded were the individuals with (1) serious oral and maxillofacial diseases (including syndromic abnormalities) other than impacted mandibular canine; (2) any history of systemic disease (e.g., congenital dental developmental disturbances and/or general malformations); or trauma. While 27 unilaterally impacted mandibular canines formed the impaction group (IG), their homonym completely erupted mandibular canines formed the control group (CG).

All CBCT images of the mandibular dentition were obtained using Kodak 9000 CBCT unit. The typical imaging protocol was as follows: 10 mA and 70 kV, and the exposure time was 32.4 s. The field of view was 4 cm × 4 cm, 6 cm × 6 cm, or 8 cm × 8 cm and the voxel size was 200 μ. The data generated in DICOM format were imported into the CS3D imaging software for 3D reconstruction. Sagittal slices were evaluated where the mandibular canine was widest labiolingually.[7]

The landmarks were identified, and the measurements were made for the assessment of root length and its dilaceration are described below:

Assessment of root length

Root length was expressed as mean deviations from zero and associated standard deviations. The reference points used for the root length assessment are shown in [Figure 1]. For the assessment of root length in nondilacerated teeth, two lines were drawn: Line a, touching the outermost part of the root and forming a tangent to the root apex point; and line m, through the midpoint of the line between the cementoenamel junction (CEJ) on the the labial (CEJlb) and lingual sides (CEJlg). Root length was measured along the perpendicular line from line a to line m [Figure 1]a.[8] For dilacerated teeth, the method modified from Sun et al. was followed [Figure 1]b.[7] Total root length in dilacerated tooth was expressed as sum of the length of nondilacerated (a) and dilacerated (b) portion of the root. Length of nondilacerated portion of the root was measured as a distance between the midpoint of the line joining CEJlb and CEJlg, i.e., CEJm and the midpoint of the line joining the point of dilaceration on the labial (DPlb) and the lingual side (DPlg), i.e., DPm. Length of the dilacerated portion was measured as a distance between DPm and root apex.
Figure 1: Reference points for assessment of root length of nondilacerated tooth (a) and dilacerated tooth (b)

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Assessment of root dilaceration

Root dilaceration is defined as a deviation of 20° or more in the apical part of the root.[9] In our study, root dilaceration was considered present if the angle (dilaceration angle) between the long axis of the nondilacerated (CEJm to DPm, line a) and dilacerated or an angulated portion (DPm and root apex, line b) of the root was ≥20°. Thereafter, the frequency of root dilaceration was evaluated for each group [Figure 2].
Figure 2: Root dilaceration of right permanent canine, as observed in the sagittal section and measurement of dilaceration angle using the reference points described in Figure 1

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Two weeks later, the same examiner (SJ) undertook duplicate measurements of root length and observations on dilaceration of root on all the canines under evaluation. A double determination method was used to compare the intraexaminer error or agreement in relevance to root length measurements and observations on dilaceration.

The data were collected and entered into a spreadsheet (Excel 2000, Microsoft Corporation, Redmond, WA, USA). It was, then, analyzed using SPSS (version 18, Chicago, IL, USA).

Statistical analysis

The paired t-test assessed the difference in mean root length between the two groups. The Chi-square test (or Fischer's exact test) was used for significance testing of the intergroup comparison of the frequency of root dilaceration. Given the statistical significance, odds ratios (IG/CG) were evaluated as an approximation of the relative risk that impacted mandibular canine held for dilaceration. The observed probability was calculated for each comparison, and P < 0.5 was considered as statistically significant.


  Results Top


[Table 1] summarizes the distribution of impacted mandibular canines studied. Of 27 unilaterally impacted canines, 55.56% (15) occurred on the right side.
Table 1: Distribution of impacted mandibular canines

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The double determination method revealed that the root length of mandibular canine, both in the IG as well as the CG had a mild (0.002 mm) but statistically insignificant intraexaminer error of measurement. Reproducibility was 100% for the assessment of dilaceration.

[Table 2] shows that the mean root length of the impacted teeth (14.34 ± 0.44 mm) was significantly shorter than that of the homonym teeth (16.01 ± 0.57 mm) (P < 0.05). Chi-squared tests indicated that the incidence of dilaceration was higher in the IG compared to the CG [P < 0.05, [Table 3]. However, the odds ratio (95% confidence interval) was insignificant (P = 0.12).
Table 2: Root length in impaction group versus control group

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Table 3: Percentages of dilaceration in the impaction group versus control group

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  Discussion Top


By definition, an impacted tooth is the one that fails to erupt into the dental arch within a specific period.[10] Failure of eruption of the mandibular canine is an unusual event.[11] The documented prevalence rates of permanent mandibular canine impaction vary from 0.05% to 1.29%.[12],[13],[14],[15],[16]

Several reports have indicated that an impacted tooth can be brought into proper alignment in the dental arch.[17],[18] However, treatment of impacted teeth accompanying dental anomalies such as short root and dilaceration pose a great challenge for the orthodontist. It is well accepted that fully developed, but short root has poor stability after orthodontic treatment. Short root may influence anchorage and tooth mobility too.[7] When considering orthodontic management of a dilacerated impacted tooth, careful planning is required to avoid any ankylosis or progression of root dilacerations and resorption through treatment.[17] Hence, we attempted to evaluate the root length and its dilaceration in particular reference to impacted mandibular canines using CBCT. The results are likely to contribute to the diagnosis and treatment planning of such orthodontic problems.

Short teeth, in general, may occur due to injury to the permanent tooth germ during odontogenesis. This results in irritation of Hertwig's epithelial root sheath and temporary arrest of root development, followed by restored growth activity, and repositioning for a period.[19] According to this study, the roots of the impacted canine were significantly shorter than those of the homonym teeth [P < 0.5, [Table 2]. One possible explanation could be that owing to limited space in the adjacent alveolar area, there may not be enough space for the root to develop adequately in impacted teeth.

Two factors might be responsible for dilaceration, in general. First, an acute mechanical injury to the deciduous teeth can transfer the force through the root to calcified portions of the permanent teeth, resulting in a twist between the calcified and noncalcified portions of the permanent tooth germ, eventually contributing to dilaceration.[20] Second, an idiopathic developmental disturbance may be the cause.[21] In our study, dilaceration occurred in 14.81% (4 in number) of the impacted mandibular canines whilst not even a single normally erupted homonym canine presented with dilacerated root. Intergroup comparison yielded statistically significant result [P < 0.5, [Table 3]. This was contrary to the CBCT findings of impacted upper canines wherein no relationship was found between the impacted canine and root dilacerations.[11] Furthermore, it is noteworthy that all four subjects showed mild dilaceration at the apical third of the root. It was also noted that the root apex of impacted teeth with root dilaceration was not only near the lingual cortical plate but also pointed labially or labio-distally [Figure 2].

Owing to the limited sample size, meaningful interpretation of the data may be difficult in the present study. However, a sample size of 27 may be acceptable for a study investigating a relatively unusual anomaly of mandibular canine impaction and for a study which is the first to carry an investigation with the above objective in any population. Furthermore, since the inter-group differences in the root length as observed in the present study may be small to be clinically acknowledged, our findings must be considered preliminary, and further verification in a more extensive study is recommended.


  Conclusion Top


Within the confines of this study, we conclude that not only impacted mandibular canines have developmentally shorter roots but also higher frequency of root dilacerations; in contrast to the completely erupted homonym canine. Hence, the risk of these accompanying root anomalies should not be neglected while treating impacted mandibular canines orthodontically and/or surgically. We also suggest that clinicians use CBCT to diagnose such root anomalies before the formulation of treatment plan to avoid future complications.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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da Silva Santos LM, Bastos LC, Oliveira-Santos C, da Silva SJ, Neves FS, Campos PS, et al. Cone-beam computed tomography findings of impacted upper canines. Imaging Sci Dent 2014;44:287-92.  Back to cited text no. 10
    
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Lin YT. Treatment of an impacted dilacerated maxillary central incisor. Am J Orthod Dentofacial Orthop 1999;115:406-9.  Back to cited text no. 18
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20.
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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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