Introduction
Canines are the cornerstones that determine the beauty of the face. Its position in the arch is crucial for both esthetics and functional aspects.1 There are various etiologies for maxillary canine impaction, like absence of eruption guidance from an anomalous lateral incisor, long and tortuous path of eruption, hypodontia, agenesis, aplasia and supernumerary teeth.2 Canine impactions are also associated with conditions such as malnutrition, anemia, rickets and cleft lip and palate and certain syndromes such as cleidocranial dysplasia, Down’s syndrome etc.3
An impacted tooth is defined as a tooth that has failed in its eruptive movement, from its development location in the alveolar process to its position in dental arch within its normal period of growth and development, and that it won’t apparently full erupt based on clinical or radiographic assessment.4 Many methods for canine localization using two dimensional dental radiographs like orthopantomogram (OPG), lateral cephalography etc. have been described in the literature, but none of those methods alone has 100% accuracy, when compared with computed tomography (CT) and cone-beam computed tomography (CBCT).5, 6 Proper treatment requires accurate diagnosis of the localization of impacted maxillary permanent canine tooth in relation to adjacent structures, assessment of root resorption and change in root morphology. 7
OPG provides an overview of the oral cavity, and may help in assessing mesio-distal impaction of teeth, however it has limitation in assessing labio-palatal position of impacted canines, whereas, CBCT can identify and locate the position of impacted canines accurately and can also assess damage to the roots of adjacent teeth and amount of bone surrounding each tooth.8
Therefore, this study was conducted to determine the usefulness of OPG for correct localization of impacted maxillary canine with the aid of CBCT as a confirmatory radiographic modality.
Materials and Methods
Data collection
The present study group comprised of 100 impacted maxillary canines, radiographed with a digital panoramic radiograph and cone-beam computed tomography scan, using purposive sampling technique. The radiographs were collected from the archives in the department of oral medicine and radiology. Diagnostic and clinical information for each patient was retrieved including general systemic disease, ongoing medication, developmental disturbances, history of orthodontic/orthognathic treatments, facial trauma/skull surgery and dentoalveolar surgery.
Inclusion criteria
Collected data set should have the impacted canines, unilateral or bilateral with age of 18 years and above whose OPG and CBCT both were taken.
Exclusion criteria
Any patient data set with missing central incisors, developmental anomalies, gross abnormalities of dental arches, craniofacial syndromes, systemic condition affecting tooth structures of canine, cysts and tumours involving the maxillary impacted canine, history of orthodontic/orthognathic treatments, facial trauma or surgery or any other associated lesion with impacted maxillary canine was excluded from the study.
Method of evaluation
For each subject OPG and CBCT (cone-beam computed tomography) scans taken by cone-beam computed tomography machine (CBCT) machine (Carestream CS 9000, Carestream Dental, Atlanta, Ga) were retrieved in DICOM format.
Each OPG was evaluated using angulation method which involves measuring the angulation of the impacted maxillary canine with the occlusal plane. The angle formed between a horizontal line drawn from the mesiobuccal cusps of right and left maxillary first molars and another line along the long axis of the impacted maxillary canine was measured. The impacted canine is diagnosed to be buccally placed when this angle is greater than 65o while it is diagnosed to be palatally placed when the angle is lesser than 65o. (Figure 1)
The CBCT data volumes were reconstructed using Ez3D2009 CBCT software and the labiopalatal position of impacted canines were assessed in static cross-sectional reformatted images. (Figure 2) In assessing CBCT studies, examiner reviewed the entire volume and was allowed to reformat images. The labiopalatal position of canines was classified as labial, mid-alveolus and palatal, depending on the relative position of the canine crown to adjacent teeth.
Statistical analysis
The readings were analyzed by the statistical expert in SPSS (statistical package for social sciences) 22.0 version software. Statistical procedure was carried out in two steps, data compilation and presentation and statistical analysis. The total data was distributed meaningfully and presented as individual tables. The predicted positions of impacted canines were compared using the Student t test with p value < 0.05 was considered statistically significant.
Results
Table 1
Gender wise distribution of impacted maxillary canines
|
Male |
28 (28%) |
|
Female |
72 (72%) |
|
Total |
100 (100%) |
Table 2
Side wise distribution of impacted maxillary canines
|
Right |
46 (46%) |
|
Left |
54 (54%) |
|
Total |
100 (100%) |
Table 3
Angulation ofimpacted maxillary canines
|
|
OPG (n=100) |
CBCT (n=100) |
Concordance w.r.t CBCT |
Student t test |
||
|
n |
% |
n |
% |
|||
|
Palatal |
54 |
54% |
52 |
52% |
100% |
0.0001* |
|
Mid Alveolus |
10 |
10% |
11 |
11% |
91% |
|
|
Buccal |
36 |
36% |
37 |
37% |
100% |
|
Figure 1
Analysis of OPG showing angulation of impacted maxillary canine of right and left side. Angle is formed between the long axis of canine and occlusal plane.
Discussion
The most critical point in the prevention of possible maxillary canine impaction is early diagnosis, to predict the subsequent failure of eruption. The best time to begin assessing potential impaction is during the early mixed dentition period, because the early diagnosis of one dental anomaly may indicate an increased risk for later appearance of other.4, 9 Since CBCT is a 3-D imaging system, it can determine the actual position of impacted canine, along with its relation to its adjacent structures. However, from the panoramic view, impaction of maxillary canine is an occasional but significant finding. It could be advantageous if this single film could be reliably used for localization of the unerupted teeth. 3, 10 Also, the current UK and European guidelines have suggested using the small FOV CBCT for assessing impacted canine only in selected cases where conventional radiographs fail to provide sufficient information to construct a treatment plan. However, the British Orthodontic Society – Orthodontic Radiographs guidelines have reported that there is no indication for the routine use of CBCT to detect impacted maxillary canines as the CBCT technique is associated with a higher overall effective dose of ionizing radiation than the conventional radiography. 11
In the present study (Table 1), the female to male ratio was 2.57:1, which is in accordance with many studies which showed that these impactions are more common in females, compared to males, with a ratio of 2:1.1, 3 However, a study conducted by Pico et al. found the number of male and female patients in a ratio of 1:1 and justified that by their reduced sample size (only 28 impacted canines in 20 patients).4
Based on the results of the present study, it was found that 46% of maxillary canines were impacted on the right side and 54% were impacted on the left side, stating a slightly higher prevalence on left side (Table 2). This is similar to the findings of Al Zoubi et al., who also reported a higher prevalence of impacted maxillary canines on left side, compared to the right side.12 However, an almost equal distribution of impacted maxillary canines was found by a study conducted by El Beshlawy DM et al., with 51% canines impacted on the right side and 50% impacted on the left side. There is no scientific evidence to clarify the higher prevalence of left side.13
In the current study, out of 100 impacted canines on OPG, 54 (54%) were placed palatally, 10 (10%) were placed in the mid-alveolus region and 36 (36%) were placed buccally. Whereas, on CBCT, 52 (52%) were placed palatally, 11 (11%) were placed in the mid-alveolus region and 37 (37%) were placed buccally (Table 3). Our prevalence of impacted canines is similar to that reported by Katsnelson A et al, who reported that 55% of canines were impacted palatally and 45% were impacted buccally. 14 In general, 85% of patients have presented with a palatal inclination and 15% with a buccal inclination. Caprioglio et al reported a ratio of 1:3 for buccal to palatal displacement. 14
A canine can be palatally impacted because extra space is available in the maxillary bone. This space can be provided by (1) excessive growth in the base of the maxillary bone, (2) space created by agenesis or peg-shaped lateral incisors, or (3) stimulated eruption of the lateral incisor or the first premolar. In those conditions the canine is free to "dive" in the bone and to become palatally impacted. 15
A study conducted by Ahad M et al compared 4 methods for localization of impacted canines and concluded that in angulation method, the palatal sensitivity was 57% and buccal sensitivity was 100%, whereas for horizontal parallax method, the palatal specificity was 66% and buccal specificity was 100%. Their results showed that horizontal parallax and angulation method are better in excluding the palatal located maxillary canine diagnosis as compared to other methods but all the methods are same to exclude the diagnosis of buccally located maxillary canine. 5 This is in accordance with the present study which shows that angulation method is 100% accurate for diagnosis of buccally and palatally impacted maxillary canine.
According to Ericson and Kurol, the absence of the "canine bulge" at earlier ages should not be considered as indicative of canine impaction. In their evaluation of 505 schoolchildren between 10 and 12 years of age, they found that 29% of the children had nonpalpable canines at 10 years, but only 5% at 11 years, whereas at later ages only 3% had nonpalpabte canines. Therefore for an accurate diagnosis the clinical examination should be supplemented with a radiographic evaluation. 16
Conclusion
Delayed diagnosis of impacted canines may lead to complex and expensive surgical procedures to manage them. Moreover, these procedures may take a long duration and cause damages to adjacent teeth, like root resorption and gingival recession of adjacent teeth. Therefore, early diagnosis will help to avoid the abovementioned complications.
Based on the results of the present study, it may be concluded that panoramic radiographs are useful for predicting the location of impacted maxillary canines when compared against the confirmatory radiographic modality like CBCT. CBCT has demonstrated to be an effective and competent method for determination of position of maxillary impacted canine and has to be reserved for extremely complex and multi-quadrant impaction cases.
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