Prevalence of Palatally Displaced Canines and Their Association with Dental and Skeletal Anomalies: A Retrospective Study

Abstract

Maxillary canines have a vital importance in the dental arches, both esthetically and functionally. They are the second most frequently impacted teeth, with palatal impaction being the most common. The purpose of the study was to evaluate the prevalence of palatally displaced canines (PDC) and their association with dental and skeletal anomalies. A retrospective analysis was conducted on 68 patients. A panoramic and a lateral cephalometric radiograph were performed to determine impaction type and patients’ dental and skeletal characteristics. The analysis grouped all PDC cases together and then subdivided them by location (right, left, or bilateral impaction). The most frequent PDC was right-side impaction. When all cases were grouped together, patients showed no family history of PDC (p < 0.05) or presence of dental anomalies (p < 0.05). No relation to skeletal class was observed, but a normodivergent growth pattern did show an association (p < 0.05). When different PDC types were analyzed separately, we observed a relationship with dental midline deviation (F = 17.04, p < 0.05), family history of PDC (F = 12.56, p < 0.05), and lateral incisors anomalies (F = 9.58, p < 0.05). Therefore, an association was found between PDC and dental anomalies when the types of impaction were analyzed separately and with the growth pattern when PDC cases were grouped together.

1. Introduction

Permanent maxillary canines are, after third molars, the teeth most frequently impacted, with a prevalence ranging between 0.92% and 3% in the general population [1,2,3]. These teeth play a crucial role in dental esthetics and function, contributing to the smile arc, upper lip support, and posterior disclusion during lateral mandibular movements [4]. Maxillary canines follow the longest and most complex eruption path in the dentition [5], typically appearing between the ages of 10 and 12 years [6], making them more susceptible to eruption deviations [3,7,8].

Their impaction is more common in females than in males [9,10,11,12,13,14,15,16], and palatal impaction is significantly more frequent than buccal, particularly in the maxilla [16,17]. Unilateral impaction occurs more frequently than bilateral impaction [12,13].

The diagnosis is generally made after the expected eruption period has passed and is based on a combination of clinical and radiological findings [3,18,19,20]. Clinically, an impacted canine is suspected when there is delayed eruption of the permanent canine or prolonged retention of the deciduous canine beyond 14–15 years of age, absence of the canine eminence, presence of a palatal bulge, or delayed eruption, distal inclination, or migration of the lateral incisor [21].

Radiological diagnosis is achieved through traditional methods such as panoramic radiographs [3,18,20,21], occlusal and periapical films [3,21], lateral cephalograms [22], and more recently, cone beam computed tomography (CBCT) [23]. Despite the higher diagnostic value of 3D imaging, panoramic radiographs remain the most commonly used due to their accessibility, lower cost, and reduced radiation exposure [18].

Numerous studies have proposed diagnostic protocols analyzing the anatomical position of the impacted tooth, its relation to adjacent teeth, and the surrounding structures [3,22,23,24] using both 2D and 3D imaging techniques. In recent years, artificial intelligence-based prediction models have been proposed to improve the accuracy and early detection of canine impaction [25].

The etiology of impacted canines is multifactorial [26,27], involving both genetic and environmental factors. Commonly associated dental anomalies include agenesis [28,29,30,31,32,33], the presence of other impacted or supernumerary teeth [32], lateral incisor size or shape anomalies [10,11,26,27,30,31,33,34,35,36], enamel hypoplasia [32], tooth transposition [30,32,37], lack of space or crowding [27], excessive space [29,38], disruptions in the eruptive pathway [8,26,39], or delayed dental development [29,40]. A genetic basis has been strongly suggested for many of these anomalies [9,27,31,35,37,41]. Additionally, associations have also been reported between canine impaction and skeletal dysplasia, specific malocclusion patterns [15,17,42,43,44,45], and even with craniofacial growth patterns [1,9,15,17,43,46].

Despite extensive research, the current literature reflects low methodological quality, often with significant risks of bias [47]. Moreover, there is still no clear consensus regarding the primary etiological factors, which hinders the identification of reliable predictors and the implementation of effective preventive or interceptive strategies [48]. Therefore, further data collection is required to develop reliable predictive models based on patients’ dental, skeletal, and occlusal characteristics, allowing the identification of canine impaction probabilities.

The present study aims to analyze the prevalence of palatally displaced canines (PDC) and explore the dental and skeletal factors associated with PDC, thereby contributing to the evidence base for future diagnostic and therapeutic approaches.

2. Materials and Methods

2.1. Sample

A retrospective analysis was conducted on an initial sample of 580 patients, from which 68 were selected. The required sample size for this type of study was estimated using G*Power v.3.1.9.6, assuming a significance level of α = 0.05, a power of 95%, and an effect size of d = 0.5, resulting in 62 participants required. The final sample size is comparable to that of other studies [3,17,29,42], and the power analysis produced a result of 0.966, indicating that the sample size was adequate.

The final sample included 18 males and 50 females. Patients were recruited from the University Polyclinic of the San Pablo CEU University (Madrid, Spain) and had previously been diagnosed with PDC and required treatment. The mean age of the sample was 19.21 ± 7.46 years (range: 12–49 years). A minimum age of 12 years was established, as this is the age after which a canine is considered impacted due to the normal eruption age of the upper canine [3,6].

The inclusion criteria were as follows: (1) all included cases had previously been diagnosed with PDC and needed treatment and there was (2) the presence of any upper impacted canine (unilateral or bilateral), (3) age over 12 years [3,6], (4) no prior orthodontic treatment, (5) inclusion of both genders and (6) any racial background, (7) radiographs taken with the same equipment, and (8) cephalograms including all relevant anatomical structures.

Exclusion criteria included (1) diagnosis of a craniofacial syndrome, (2) severe asymmetries, (3) clinically appreciable congenital malformations, (4) cleft lip and/or palate, (5) sequelae of traumatic injuries to permanent teeth, (6) history of facial trauma or bone fractures, (7) presence of odontomas or (8) cysts or (9) prosthetic restorations, (10) cases where the orthodontist could not confirm palatal impaction, (11) patients under 12 years of age (as maxillary canine eruption may not be complete), (12) patients with prior orthodontic or orthopedic or facial surgical treatment, (13) presence of artifacts on radiographs, and (14) poor-quality radiographs.

All procedures followed the basic principles of the Declaration of Helsinki and Spanish Organic Law 3/2018 on Personal Data Protection and Digital Rights. The protocol was approved by the ethics committee of the Faculty Medicine, CEU Universities, Madrid, Spain (ref: 328/19/16; date: 17 June 2019). Participants received an informational document detailing the study’s purpose and procedures and provided written informed consent. For minors, consent was obtained from their parents or legal guardians.

2.2. Study Design

Panoramic and lateral cephalometric radiographs were analyzed. Since all patients had been previously diagnosed with PDC, no additional radiation exposure was required for the purposes of this study. Panoramic radiographs were obtained using the ORTOPHOS apparatus (Sirona Dental Systems GmbH, Bensheim, Germany). Lateral cephalometric radiographs were acquired with a Wehmer cephalostat (BF Wehmer Co., Lombard, IL, USA) and a Sedecal generator (Sociedad Española de Electromedicina y Calidad S.A., Algete, Madrid, Spain). Both types of radiographs were digitally processed using AGFA DX-S systems and specific software (version STR_1505, Agfa HealthCare, Mortsel, Belgium).

The presence of agenesis, supernumerary teeth, or other inclusions was diagnosed through panoramic radiographs. A cephalometric analysis was performed on each lateral cephalogram to determine the skeletal class and growth pattern. Cephalometric tracings were conducted on a personal computer using DBF-Ceph software (Gioconda OrthoCeph, Diagnóstico Bucofacial, Spain), which provided Ricketts, Steiner, Jarabak, and McNamara cephalometric analyses.

A detailed clinical history and examination were also carried out, focusing on dental anomalies such as a family history of canine impaction or agenesis, presence of conoid or microdontic lateral incisors, generalized microdontia, crossbite, and upper dental midline deviation. The clinical diagnosis of dental anomalies, radiographic analysis, and cephalometric tracings were all performed by a single clinician—an orthodontist with 12 years of experience.

2.3. Statistical Analysis

The analysis was performed by first grouping all PDC cases together (

Table 1. Prevalence and descriptive data of the sample (N = 68).

		Prevalence	Percent
Gender	Female	50	73.5
	Male	18	26.5
	Total	68	100.0
Ectopic	Left unilateral	24	35.3
	Right unilateral	26	38.2
	Bilateral	18	26.5
	Total	68	100.0
Family history of canine impaction	Yes	16	23.5
	No	52	76.5
	Total	68	100.0
Presence of agenesis	Yes	9	13.2
	No	59	86.8
	Total	68	100.0
Family history of agenesis	Yes	1	1.5
	No	67	98.5
	Total	68	100.0
Conoid or microdontic lateral incisors	Yes	23	33.8
	No	45	66.2
	Total	68	100.0
Other inclusions	Lateral incisor	1	1.5
	Lower canine	1	1.5
	Premolars	1	1.5
	Molars	1	1.5
	Third molars	7	10.2
	No	57	83.8
	Total	68	100.0
Supernumerary teeth	Yes	1	1.5
	No	67	98.5
	Total	68	100.0
Microdontic dentition	Yes	1	1.5
	No	67	98.5
	Total	68	100.0
Crossbite	Yes	21	30.8
	No	47	69.1
	Total	68	100.0
Upper dental midline deviation	Yes	27	39.7
	No	41	60.3
	Total	68	100.0
Growth pattern	Hypodivergent	25	36.8
	Normodivergent	30	44.1
	Hyperdivergent	13	19.1
	Total	68	100.0
Malocclusion	Class I	18	26.47
	Class II	25	36.76
	Class III	25	36.76
	Total	68	100.0

) and then dividing them into groups based on the location of impaction (right, left, or bilateral) (

Table 2. Relationship between variables and type of canine impaction.

Palatally Displaced Canines
		13–23	13	23	Total	Fisher	p-value
Gender	Female	28.0%	34.0%	38.0%	100%	1.38	p = 0.51
	Male	22.2%	50.0%	27.8%	100%
Upper dental midline deviation	Right	11.1%	83.3%	5.6%	100%	17.04	p < 0.05 *
	Left	0%	18.2%	81.8%	100%
Family history	No	28.8%	26.9%	44.2%	100%	12.56	p < 0.05 *
	Yes	18.8%	75.0%	6.3%	100%
Agenesis	No	26.8%	39.3%	33.9%	100%	0.36	p = 0.92
	Yes	25.0%	33.3%	41.7%	100%
Conoid incisors	No	33.3%	44.4%	22.2%	100%	9.58	p < 0.05 *
	Yes	13.0%	26.1%	60.9%	100%
Crossbite	No	27.6%	42.6%	29.8%	100%	2.07	p = 0.36
	Yes	23.8%	28.6%	47.6%	100%
Growth pattern	Hypodivergent	31.2%	37.5%	31.3%	100%	2.11	p = 0.76
	Normodivergent	27.2%	45.5%	27.2%	100%
	Hyperdivergent	14.3%	28.6%	57.1%	100%

* Statistically significant (p < 0.05).

).

Data were analyzed using SPSS 15 software. Descriptive statistics included frequency tables for qualitative variables. Fisher’s exact test, which is equivalent to the chi-square test, was used to examine relationships between qualitative variables. The chi-square test was also used to test hypotheses regarding population proportions. A significance level of 0.05 was used throughout

Table 1 and Figure 1 show the prevalence of the studied variables. Among the participants, 73.5% were females (50), and 26.5% were males (18).

3. Results

3.1. Prevalence of PDC

The sample consisted of 68 cases, with a mean age of 19 years (range: 12–49 years). Most participants were Caucasian, except for one Ecuadorian patient. The most frequently impacted tooth was the upper right canine (26 cases, 38.2%), followed by the upper left canine (24 cases, 35.3%). Bilateral impaction was the least frequent (18 cases, 26.5%), making unilateral impaction the most common (73.5%). However, this difference was not statistically significant.

3.2. Association of PDC with Dental Anomalies

A statistically significant relationship was found between the presence of PDC and the absence of a family history of PDC (chi-square 19.06, p < 0.05). Most patients (76.5%) did not have a family history of PDC. Similarly, a significant relationship was observed between canine impaction and the absence of agenesis (p < 0.05), with 86.8% of patients showing no agenesis. Four patients presented agenesis of one or more third molars, and four others had agenesis of other teeth. Only one case involved agenesis of an upper left incisor.

A significant association was also found between the absence of conoid or microdontic lateral incisors and the presence of PDC (chi-square 7.12, p < 0.05). Sixty-six percent of the sample (45 patients) did not have this alteration. Among the remainder, 19.1% had microdontic lateral incisors, 19.1% had both lateral incisors with a conoid shape, 4.4% had a conoid-shaped right lateral incisor, and only one patient had a conoid-shaped left lateral incisor.

No significant association was found between PDC and a family history of agenesis, with 98.5% of the sample having no such history. Similarly, no significant association was observed with dental inclusions of lateral incisors, canines, premolars, or molars (83.8% had no other inclusions except for the PDC); supernumerary teeth; or microdontic dentition (only one patient had a supernumerary tooth, and one patient had microdontic dentition).

3.3. Association of PDC with Skeletal Anomalies

From an occlusal standpoint, no significant associations were found between PDC and posterior crossbite (69.1% did not present this condition) or with dental midline deviation (60.3% showed no deviation). Similarly, no association was observed with skeletal class, where the distribution was similar across the three groups (Class I—26.47%; Class II—36.76%; Class III—36.76%).

However, a significant relationship was identified between PDC and normodivergent facial growth patterns, with a lower proportion of hyperdivergent patterns (chi-square = 6.74, p < 0.05). Normodivergent growth patterns were the most common (30 cases, 44.1%), followed by hypodivergent patterns (25 cases, 36.8%) and hyperdivergent patterns (13 cases, 19.1%).

3.4. Analysis of PDC by Type of Impaction

The relationship between qualitative variables and the type of canine impaction (bilateral, unilateral right, or unilateral left) is described in Table 2, where no significant association was found between gender and the prevalence of different types of canine impaction (F = 1.38, p = 0.51). However, it appears that in females, bilateral impaction is the least frequent (28%), with similar prevalence for unilateral impaction (34% right and 38% left). In males, unilateral right impaction was the most common (50%).

In contrast, a significant relationship was found between dental midline deviation towards the side of the missing canine (F = 17.04, p < 0.05).

Additionally, a significant association was detected between the type of impaction and the presence of a family history of impaction (F = 12.56, p < 0.05). The pattern of relationship showed that unilateral right impaction was particularly common among those with a family history of impaction (75%), whereas in patients without a family history, the distribution of impaction types was more balanced.

A significant association was also found between the type of canine impaction and alterations in the lateral incisors (F = 9.58, p < 0.05). Left unilateral impaction showed a significantly higher proportion of conoid lateral incisors (60.9%) compared to other types of impaction, where the most common scenario was the absence of conoid incisors (33.3% in bilateral and 44.4% in right unilateral impaction).

However, no relationship was observed between the prevalence of a specific type of impaction and the presence of agenesis (F = 0.36, p = 0.92) or crossbite (F = 2.07, p = 0.36) or the predominance of a specific growth pattern (F = 2.11, p = 0.76).

4. Discussion

The study of the association between PDC and specific craniofacial characteristics and other dental anomalies is of great clinical relevance [9]. Numerous studies have sought to determine predictive models based on dental, occlusal, and skeletal characteristics in patients [9,47,49].

Identifying the possibility of canine impaction has important clinical implications in dentistry, such as early diagnosis and preventive planning [50]. Understanding the predictors of canine impaction allows the clinician to make the correct decision as to whether to monitor canine eruption or to intervene. Thus, early intervention, such as extraction of deciduous canines [50] or maxillary expansion [50,51], can minimize the possibility of complications arising from tooth impaction, such as root resorption [52], and could reduce treatment time or avoid more complex or surgical treatment [50,53].

Most reviewed studies reported a predominance of unilateral impaction over bilateral [2,12,13,14]. Similarly, our study found that bilateral canine impaction was less frequent (26.5%) compared to unilateral impaction, with similar percentages to other studies reporting bilateral impaction rates between 17% and 28% [29]. Other authors reported lower rates of bilateral impaction (around 2%) [2] or, conversely, higher rates (45.4%) [10], with some even finding bilateral impaction more common than unilateral [15].

There is no consensus in the literature regarding a predominance of impaction on one side. Some authors reported higher left-side impaction [54], while others reported higher right-side impaction [29]. In our study, the most common impaction was the right upper canine, although the distribution was fairly uniform.

Several studies have observed a relationship between maxillary canine impaction and other dental anomalies [8,26,28,29,30,31,32,33,35,37,38,39].

The relationship between lateral incisor agenesis and canine impaction has been documented by numerous authors [28,29,30,31,32,33], who observed frequent cases of agenesis associated with impacted canines [12]. However, in our study, canine impaction did not appear to be associated with agenesis. Moreover, no relationship was found between the type of canine impaction and a higher prevalence of dental agenesis.

Additionally, most patients with impacted canines in our study did not present other dental inclusions. The most common inclusion was that of third molars, which has been found to be more frequent in the general population [2,8]. This suggests that there may be no relationship between PDC and the presence of other dental inclusions.

Some authors attribute palatal displacement of canines to the absence of an eruption guide from the lateral incisor root during physiological canine eruption, particularly in cases with upper lateral incisor anomalies [11,26,30,34,35,36]. In our sample, a higher proportion of patients did not present conoid or microdontic lateral incisor alterations.

Various studies have associated PDC with genetically determined dental anomalies, such as agenesis or conoid or microdontic lateral incisors [11,27,31,41]. Kolokitha et al. [48] found that the presence of conoid lateral incisors can be an important early risk indicator for maxillary canine impaction, as it manifests before canine eruption. Although we did observe a relationship between patients with left unilateral impaction and a significantly higher proportion of conoid or microdontic lateral incisors, when all the cases of canine impaction were grouped together, a significant association was found between the absence of conoid or microdontic lateral incisors and PDC. In this regard, in our study, a significant relationship was observed between PDC and the absence of agenesis, and no association was found with family history of agenesis when all the cases of canine impaction were grouped together. Furthermore, a significant relationship was found between PDC and the absence of family history of PDC in this study when all the cases of PDC were grouped together.

However, we did find a relationship between right canine impaction and family history of impaction when PDC types were studied separately. These findings support the results of other studies [9,27,37,41], which suggest a possible genetic component.

Regarding malocclusions, some studies have observed an association between PDC and smaller maxillary volumes [53] or with sagittal skeletal discrepancies [15,17]. In contrast, our study found no association between skeletal class and canine impaction (with a similar distribution across Class I, Class II, and Class III) or with dental midline deviation, as in other studies [55]. However, when analyzing the types of canine impaction separately, a relationship was observed with dental midline deviation towards the side of the missing canine, as has been observed in other studies when premature loss of the deciduous canine occurs [56].

Finally, our study identified normodivergent growth patterns as the most common among patients with PDC. This contrasts with other studies reporting a predominance of hypodivergent growth patterns [9,15].

Given the controversy in the literature, it is not yet possible to establish a predictive model for canine impaction based on dental anomalies or sagittal and vertical skeletal patterns. Further research is needed [47] to develop a predictive model for early diagnosis and treatment of canine impaction to reduce the need for complex treatment or surgical interventions.

Study Limitations and Future Research

Our final sample of 68 patients with PDC, selected from an initial pool of 580, could be expanded. Future studies could analyze comparisons with buccally displaced canines to assess differences or variables such as changes in dental class, which are expected to happen. Additionally, investigating genetic and molecular variables may help to better understand the etiological processes of canine impaction.

5. Conclusions

The results of this study suggest that bilateral impaction is less prevalent than unilateral impaction. In cases of unilateral impaction, no significant prevalence of one side over the other was observed. When the different PDC groups were analyzed separately, associations were found with dental midline deviation, the presence of a family history of PDC, and lateral incisor anomalies. Additionally, there appears to be an association between PDC and a higher prevalence of a normodivergent growth pattern when PDC cases were grouped together. Given the controversy among researchers, further studies are required to establish a predictive model for canine impaction based on these factors.