Maxillary canine position of patients with non-syndromic craniofacial disorder – a retrospective evaluation of panoramic radiographs

Abstract

Objectives

The study objective was to evaluate the tooth position of maxillary permanent canines in German orthodontic patients with non-syndromic cleft lip and/or palate and Robin sequence compared to a control group without.

Materials and Methods

A total of 116 panoramic radiographs were included and divided into group 1 craniofacial disorder (n = 50) and group 2 without (n = 66). In order to evaluate the position of maxillary canines, radiographic parameters (sector subdivision; inclination angle) were used. Additionally, clinical records, parameters like sex, cleft localization, interobserver reliability were evaluated.

Results

The canine position in sector subdivision showed no position in sector 1 and 2. The most common canine sector position in group 1 was sector 5 in the first quadrant and sector 4 in the second and group 2 sector 5 in both quadrants. Inclination angle showed statistically significant displacement tendency (p = 0.015) of 11 cases in group 1 and 6 in group 2 of the right sided canines. There was a significantly difference in (p = 0.0259 (χ2))between cleft and non-cleft side in the inclination of the maxillary canine. In total four cases showed a displacement tendency of the maxillary canine, two in the cleft and two in the non-cleft side. Success rate of orthodontic alignment was 100%.

Conclusion

Displacement tendency of the maxillary canine in patients with craniofacial disorder is higher.

Clinical Relevance

Radiographic evaluation enables the diagnosis of displaced teeth. A rigorous monitoring of canine eruption position is imperative and important to consider in the long lasting and comprehensive orthodontic treatment planning in craniofacial disorder patients.

Introduction

Cleft lip and/or palate (CL/P) is one of the most common hereditary malformations. The prevalence is estimated at about 1 in 600 newborns [1]. The etiology of cleft malformations is multifactorial, including endogenous and exogenous factors [2]. According to geographic location, socioeconomic status, sex and ethnicity the incidence varies strongly [3]. The cleft formation can occur in different combinations and be of varying severity. An association with some syndromes such as Robin sequence (RS) is known. In 80-90%, RS is associated with a cleft palate (CP) [4, 5]. This malformation involves the triad of mandibular retrognathia, glossoptosis and resultant upper airway obstructions [6] with a prevalence of 11.3:100 000 live births [7]. Cleft formation is associated with restrictions in oral hygiene, dental arch form deformation, oro-nasal fistulas, distinctive skeletal discrepancies between the jaws and velopharyngeal insufficiencies. This might lead to multiple functional disorders like hearing and speech problems. Furthermore, dental anomalies, especially affecting the teeth adjacent to the cleft, are common in patients with craniofacial disorders. Variations of tooth shape and structure, microdontia and supernumerary teeth of both dentitions adjacent to the cleft are observed [8, 9]. The teeth show eruption disorders and could change in position. 

In 1-2% of the population, the permanent maxillary canine is displaced and impacted [10, 11]. It is the most frequently impacted tooth[12]. Initially, the germ of the maxillary canine is located in the infraorbital region and inclined distally. It only erupts into the oral cavity after straightening mesially and has a curved dentition path measuring approximately 22 mm. There are two theories about the occurrence of tooth impaction of the maxillary canine. The first is the guidance theory that the lateral incisor is a significant guard rail. This is the case in a mandibular retrognathia and the maxillary anterior teeth is very steep often caused by a very narrow apertura piriformes. This results in very narrow roots of the maxillary incisors. The root tip of the canine is in close anatomic to the mesially tilted root of the external incisor and this causes the guardrail effect [13, 14]. If this is missing the canine is located palatally, this placement is in 85% of the cases [15, 16]. The other theory is the genetic condition with the accompanying family burden. The western population and the female sex are more affected. There are frequent variations in tooth size or shape, specifically   of the lateral incisor [17–20]. Furthermore, in 47.5% of the cases impacted maxillary canines are associated with other dental anomalies, e. g.   microdontia, supernumerary teeth, enamel hypoplasia and transposition of teeth [21, 22].

In patients with CL/P the prevalence of ectopic and impacted canines is ten to twenty times higher compared to patients without a craniofacial disorder [23–28]. Thus, it is important for both dentists and orthodontists to be aware of the signs and symptoms to identify this dental anomaly. Screening for canine impaction and the associated dystopia should be performed between the age of 8 and 10 years and should include palpation,   comparison in symmetry of the opposite quadrant, pronounced tipping of the lateral incisor and, if indicated a follow-up radiographic evaluation [29]. Therefore,  early diagnosis is important and can significantly reduce complications like root resorption of the lateral incisor (in 12% of the cases), ankylosis and/or the necessity to surgically remove the affected tooth [30–32]. It can give the dentists and orthodontists the opportunity for early orthodontic alignment and the possibility to adjust the tooth in the dental arch [33]. In specific cases it can be useful to remove the primary maxillary canine in order to create room and provide a guidance for the eruption of the permanent tooth [34]. Introduction of computed tomography in dentistry has contributed to a more exact localization of ectopic teeth and led to a more exact treatment planning [35, 36]. 

There are radiographic signs identifiable in panoramic radiographs (PAN) allowing to predict the position of the maxillary canine. Those signs include the angulation between the vertical distance of the crown tip to the occlusal plane, the tooth axis and the midline, the anteroposterior position of the root point relative to the center line, and the degree of overlap between the angular tooth crown tip and the lateral incisor. Ericson and Kurol defined examination criteria of ectopically erupting maxillary canines for PAN in 1987 [31, 32, 37, 38]. Currently, there is limited data available on this topic in the German population.

The aim of this study was to evaluate the position and displacement tendency of the maxillary canine of German orthodontic patients with non-syndromic CL/P and RS. This patient group was compared to a healthy control group of orthodontic patients without craniofacial disorder. In addition, the association of the tooth position between tooth agenesis, the cleft side and sex was determined. 

Materials And Methods

Study design

This cross-sectional cohort study was designed to be retrospective and monocentric at the Department of XX. Prior to the start of the study, the protocol was approved by the institutional ethics committee of XX (approval number: XX). 

Patients

In total, the PAN of 116 patients of the Department of XX at the XX were included in the study. The data were obtained from the records of patients of the Department of XX at XX. The sample size was calculated with a two-sided two-sample t-test method by a statistician during the study planning. The composition of the sample size for the group of patients with craniofacial disorder is oriented to the current patient cases of the Department of XX at XX. The timeline of participants' recruitment was from April to October 2019. It consisted of Caucasian male and female patients. 

The following inclusion criteria were used for recruitment:

• Current orthodontic treatment in our department.
• Age between 4 and 18 years. 
• Non-syndromic craniofacial malformations such as CL/P and RS. The diagnosis was confirmed by the neonatal picture or pre-operative record.
• Patients with a PAN according to the ALARA (as low as reasonably achievable) principles with an indication justifying radiation exposure within the course of orthodontic treatment.

The exclusion criteria were defined as follows: 

• Additional associated complex congenital malformations (syndromes) or mental retardation, due to the fact that some syndromes are associated with dislocation, impaction and malposition of (maxillary) canines.
• Patients younger than 4 years and older than 18 years. Patients younger than four years were excluded because the position of the canine cannot reliably determined.
• Radiographs of insufficient quality for diagnostic purposes, e. g. overexposure.

The patients were divided into two groups:

1. Group one – patients with craniofacial disorders, i. g. CL/P and RS
2. Group two – patients without craniofacial disorder; healthy control group.

The inclusion criteria for group one represented the presence of a non-syndromic craniofacial malformation, e. g. at least a cleft of the soft palate. Therefore, this group is composed of patients with CL/P and RS.

Instruments for assessment

Sector subdivision of the maxillary canine tooth

To assess the position of the maxillary canine the projection of canines’ cusp was divided into five zones according to the sector subdivision shown in the schematic illustration of the PAN in Figure 1. Sector 1 is oriented to the midline of the maxilla mesial to the central incisor. Sector 2 is defined by the longitudinal axis of the central incisor. Sector 3 forms the distal root surface of the central incisor. Sector 4 is the distal root surface of the lateral incisor and sector 5 is oriented towards the mesiodistal protrusion of the future place of each tooth in the tooth row. An indication of the dislocation tendency of the canine is when the tip of the canine is in sectors 1 and 2.

Inclination angle of the maxillary canine 

Angle α is defined by the intersection of the canine axis and the center line of the maxilla between central incisors. Angle ß is defined by the intersection of the canine axis and the tooth axis of the lateral incisor. An indication of a dislocation tendency of the maxillary canine is given when angle α is exceeding 30° and angle β measures more than 39°.

Reliability measurement

To assess the interobserver reliability 37 of the total 116 PAN were evaluated by two experienced examiners (XX, XX) applying the sector subdivision and the inclination angle α and β. One of these examiners assessed already in total 116 PAN and observed the 37 radiographs twice. The examination of the radiographs was independently between both examiners, spatially and temporally separated. 

Statistical analyses

The patient data was collected from our electronic database, clinical records and pseudonymized form saved in an Excel® sheet (Microsoft Inc., Redmond, Washington, USA). The statistical evaluation, descriptive statistics and analysis were performed using JMP (Version 15.2.0, SAS Institute Inc., Cary, USA). In order to assess the reliability of the interrater measurements, Cohen’s kappa coefficient was used. The distributions of the maxillary canine inclination and sector division were studied applying Pearsons Chi-square χ2 analysis. The differences of the mean values between and in the two groups were evaluated using Student’s t-test. In addition, factors including tooth agenesis, craniofacial disorder, cleft side and patient sex were statistically analyzed. The level of statistical significance was set up at 5 % (α = .05).

Results

Characteristics of patients

In total, 116 patients (50% male, 50% female) were included. According to the inclusion criteria, the patients were divided into the craniofacial disorder group 1 (n = 55) and the healthy control group 2 without any craniofacial disorder (n = 66). The mean age of all patients was 9.73 ± 2.87 years. Between the groups, the mean age slightly differed (group 1: 8.32 ± 2.27 years vs.  group 2: 10.80 ± 2.82 years). The detailed data of the patients included in the study is shown in Table 1.

Table 1: Characteristics and distribution of patients in group 1 and group 2

Abbreviations: SD = Standard deviation, CL/P = Cleft lip and/or palate, RS = Robin Sequence

Interrater reliability measurement

The values of Cohen’s kappa coefficient are shown in Table 2. The interrater measurements of the canine inclination in the first quadrant (Q1) of angle β showed a value of 1.0 indicating a very good degree of agreement. The canine inclination in the second quadrant (Q2) of angle β with a kappa-value of 0.65 indicated a good degree of agreement. The remaining radiographic factors had moderate degree of agreements for both examiners.

Table 2: Results of the evaluation of the interrater reliability between the two examiners (XX, XX).

Abbreviations: Q1 = First quadrant, right upper jaw; Q2 = Second quadrant, left upper jaw 

Sector subdivision and inclination of the canine tooth in group 1 and 2

The examinations of sector subdivision showed no position of the maxillary canines in sectors 1 and 2 in all patient groups. An indication of the displacement dislocation tendency of the maxillary canine in sector subdivision was not evaluated. Comparing group 1 to group 2, the most frequent canine position of group 2 was in sector 5. Group 1 showed in the first quadrant sector 5 the most frequent position and in the second quadrant on the left side sector 4. The correlation χ² between group 1 and 2 of the sectors in the first quadrant was 0.3477 and in the second quadrant 0.0241. The inclination of the maxillary canine showed the indication of displacement tendency in correlation χ2 between group 1 and 2 of canine inclination in the first quadrant showed 0.0138 and in the second quadrant 0.0379. There was no statistical significance in the inclination and sector division of the canine in group 2 in the different craniofacial disorders and cleft locations. In group 1 in five cases and in group 2 in one case had an increased angulation of the right sided canines with a displacement tendency. There was a statistically significant difference in the inclination of the right maxillary canine between group 1 and 2 (p = 0.0150). On the left side there were six cases in group 1 and five in group 2. However, this was not statistically significant.

Table 3: Sector division and inclination of the canine in the first and second quadrant of group 1 and 2

* Statistical significancy (p < .05)

Abbreviation: Q1 = First quadrant, right upper jaw; Q2 = Second quadrant, left upper jaw 

Relationship between tendency of the maxillary canine and tooth agenesis in patients with craniofacial disorder

The relationship of displacement tendency and tooth agenesis of group 1 showed in the first quadrant two patients with a displacement tendency and tooth agenesis. In addition, three patients had a displacement tendency without tooth agenesis. The Pearsons χ² had a value of 0.8462. In the second quadrant, three patients had a tooth agenesis and a displacement tendency, two patients showed a displacement tendency without an agenesis. The Pearsons χ² had a value of 0.7694. 

Comparison of cleft and non-cleft side in displacement tendency of the maxillary canine in patients with unilateral cleft lip and palate

Table 4 shows the comparison of cleft and non-cleft side in sector division and inclination angle of the maxillary canine in patients with unilateral CLP of group 1. There was no statistically significant correlation (p = 0.8580 (χ2)) of the sector position of the canine between cleft and non-cleft side. Most canines were in sector 5 of the cleft side and showed no displacement tendency. There was a statistically significant difference (p = 0.0259 (χ2)) between cleft and non-cleft side considering the inclination of the maxillary canine. In total, four cases showed a displacement tendency of the maxillary canine, two on the cleft side and two on the non-cleft side. 

Table 4: Comparison of sector division and inclination of the maxillary canine by cleft versus non-cleft side in patients with unilateral CLP (n = 31) of group 1

* Statistical significancy (p < .05)

Conspicuousness of the maxillary canine in patients with craniofacial disorder 

The clinical records showed in six of fifty patients of group 1 conspicuousness of the maxillary canine. In two patients the tooth 53 showed a persistency, in one patient 63 was persistent and in one case 53 and 63 showed a persistency. In one patient, there was a palatal displacement of the canine and in one patient a vestibular This was neither conspicuous in the sector classification nor in the inclination angle when evaluating the PANs. The success rate of the orthodontic alignment of both displaced teeth was 100%.

Table 5: Conspicuousness of the maxillary canines of group 1

Discussion

The aim of this study was to evaluate the position of the maxillary canines and the associated displacement tendency in a population of German orthodontic patients with a non-syndromic craniofacial disorder compared to a healthy control group without any craniofacial disorder in the Department of Orthodontics at XX. This is a novel approach regarding the group of patients with craniofacial disorders like RS and CL/P in Germany. Regarding the maxillary canine position evaluated according to the sector subdivision, both patients with and without craniofacial disorder showed no displacement tendency. Regarding the assessing method of the inclination angle, there was a statistically significant higher displacement tendency in patients with craniofacial disorder of the maxillary canine. When comparing both evaluation methods they showed different results in displacement tendency, potentially due to the fact that the methods differ from each other extensively and already have been described controversially in literature. Warford et al. showed that the sector building is the reliable value of malpositioned and impacted teeth and the angulation is a robust parameter for this purpose [39]. Several groups had shown that the sector score parameter in combination with the angulation of the canine to the lateral incisor and the midline were powerful and reliable values [38, 40]. Thus, it is recommended that the linear angle measurement in PAN, like in this study, should be combined with the additional assessment of the canine sector position [28, 41]. In the present study, there were no significant connection between the two parameters. As already mentioned, only the inclination angle showed a statistically significant result between the craniofacial disorder group and the healthy ones. This could be due to the fact of the presence of a CL/P. In the current literature, the alpha angle according to Ericson and Kurol is the most commonly used parameter to determine the angulation of the canine in patients with CL/P [24, 42]. Hereman et al. set the predictive cut-off value in patients with CL/P at an angle between the canine and the midline larger than 23.8 degrees [43]. Westerlund et al. determined a value larger than 30 degrees, likewise [44]. The group of Russel and McLeod even decreased this value with an angle more than 45 degrees [45]. Rizell et al. used a modification of the angulation and sector measurements of Ericson and Kurol adapted to dental anomalies occurring in patients with CL/P [38, 46]. They have shown that cleft canines requiring surgical exposure had an increased angulation and canines on the cleft side had an increased angulation angle. These results are in accordance with our study, observing a statistically increased angulation in canines of the cleft side compared to the non-cleft side. This showed that the canines of the cleft side have a higher risk for dislocation and malposition compared to the canines of the non-cleft side.

Due to the fact that this study showed conspicuous parameters of the craniofacial disorder group were the inclination angle in combination with the assessment TAC, this relationship has been statistically evaluated. The results showed that five patients had a displacement tendency and additionally, a tooth agenesis: Five patients showed a dislocation tendency without tooth agenesis. There was a close association between tooth agenesis and a dislocation tendency. These findings are consistent with the literature. Several authors described that displacement and impaction coincides with tooth agenesis, specifically the lateral incisor [28, 45, 47]. This tooth has a crucial role in guiding the maxillary canine to its correct position according to the guidance theory. On the other hand, it is to consider, that the absence of the lateral incisor is frequently associated with the occurrence of a cleft, certainly on the cleft-side. This tooth agenesis is more a characteristic sign of a craniofacial disorder and could lead to a displacement of the canine. 

In the current literature, limitations of two-dimensional radiographic images have been extensively discussed, specifically considering magnification, distortion, high radiation dose and positioning errors in the anterior maxilla an overestimation of the distance of the tooth from the midline and of the angulation of the canine in PAN is described [48]. Nonetheless, the dental PAN is a valuable evaluation tool, providing an overview of the entire dentition. Furthermore, the patient is exposed to a lower radiation dose compared to a full-mouth series of intra-oral radiographs [49]. As a part of the clinical orthodontic routine, it is recommended to assess the localization of dislocated and impacted canines [50]. However, three-dimensional radiographic techniques, e. g. cone beam computed tomography, allow a much more precise determination of the teeth’s position and its relationship to adjacent tissue with a radiation dose comparable to PAN [51]. 

In the current study, the location of canines was assessed using visual diagnosis of the examiners, without an exact standardized scaling of the PAN. Regarding in the present study, the kappa values of the canine inclination of angle β in the first quadrant showed a very good degree of agreement and in the second quadrant showed a good degree. The remaining radiographic assessed parameters had moderate degrees of agreement for both examiners. Compared to a study about evaluation of the tooth agenesis of patients with CL/P or RS assessed by the same two examiners, like in the current study, the kappa value showed a moderate degree of agreement, likewise [52]. This study was performed under the same conditions as the current one. The PANs were obtained by both examiners independently of each other, in separate rooms and at different times. In order to assess the exact canine position, regardless of the reliability and bias of the examiner, three-dimensional images seem to be the reliable and ideal radiographic technique. In patients with CL/P, three-dimensional images are performed routinely to evaluate the dimensions of bone in the alveolus and palatal cleft. Indications for three-dimensional radiographic imaging are the assessment of bone volume before and after bone grafting or setting skeletal bone anchorage screws for an orthodontic appliance [53]. In combination to these examinations, it is useful to assess the position and the potential agenesis of the teeth to avoid additional images, increased an extra radiation and costs. This means that an interdisciplinary therapy can be planned based on one three-dimensional image and providing benefit to the patient and therapists. 

The clinical records of this study showed in six out of fifty patients with a craniofacial disorder conspicuousness’s in form of persistence of a deciduous canine or a clinical displacement of the permanent maxillary canine. Even though this was not observed with the examination parameters of the PANs. In the current literature, there is no information about persistence of deciduous canines in patients with craniofacial disorder. Regarding the dentition, this might be a sign of an ectopic or impacted canine, due to the fact that there was no resorption of the deciduous canine root. In patients with CL/P it can be helpful to preserve the deciduous canine to avoid a mesial drift of teeth of the lateral segment. However, for the treating orthodontist or dentist it is important to know the right timeframe for removing the deciduous canine to provide space to the permanent tooth and a guide rail to erupt to the occlusal plane. 

Considering the study design, there are certain limitations. This is a cross-sectional retrospective study which has already limitations and a reduced informative value in the results compared to a prospective study. That was reflected by data obtained from the clinical records in evaluating of the final canine displacement and in case of a spontaneously eruption or an orthodontically adjusted maxillary. Ideally, that parameters could be evaluated in a prospective study to assess the location of the canine at the beginning of the observation period and in a final step to evaluate the eruption position and the potential occurrence of a displacement. The age of the patients included in this study could have been better delimited depending on the eruption age of the canine tooth. This was not considered in order to eliminate the bias of too small patient groups. Here, the limitation of a small sample size is shown like it often happens in comparative monocentric studies with low prevalence’s of the disease patterns, e. g. craniofacial disorders and, specifically RS. In addition, a cross-sectional design had to be used. Further shortcomings were the possible overestimation in the anterior maxilla of the distance of the tooth from the midline and of the angulation of the canine in PAN. This has to be considered in the examination of the PANs. In general, a prospective longitudinal multicenter study with adjusted sample sizes and corresponding control groups should be performed to get further and comparable results. This should demonstrate to other practitioners the difficulty in treating patients with craniofacial malformations, the importance of a multiple interdisciplinary therapy, and the sense to recognize and treat possible other dental anomalies that may occur at the right timepoint.

Conclusion

In conclusion, the assessing method of the inclination angle showed differences between the craniofacial disorder and the healthy control group. The position of the maxillary canine in patients with craniofacial anomaly had a statistically significant higher displacement tendency. There is a significantly difference of the inclination between cleft and non-cleft side and an increased tendency of displacement. Therefore, we recommend a rigorous monitoring of cleft canine position as advocated. The clinical examination, certainly in the transitional dentition when the canine is expected to erupt combined with a radiographic image is crucial in these patients.

Declarations

Conflict of interest

The authors declare no conflict of interest.

Acknowledgements

We would like to thank the team from the Department of Oral and Maxillofacial Surgery, Institute for Clinical Epidemiology and Applied Biometry, as well as the team from the Department of Orthodontics at XX. We especially thank XX. Our thanks also go to XX for producing the orthodontic appliances for the patients with craniofacial disorder. We are grateful for our entire team, for the good and close interdisciplinary cooperation in which conscientious patient care is paramount.

Funding

No funding was obtained for this study.

Ethics approval

Approval was given by the institutional ethics committee of XX (approval number: XX). The conduct of the study was performed according to the Declaration of Helsinki.

Informed consent

Not Applicable.

Author Contributions

MS and CW drafted the manuscript. ML and CW recruited the patients. CW made the statistical analysis. BK, ML and CW participated in manuscript. MS participated in manuscript and coordination. All authors read and approved the final manuscript.

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