Cone-Beam Computed Tomography-Based Comparative Analysis of Maxillary Canine Morphometry and Morphology Between Saudi and Spanish Populations

Abstract

Background: The maxillary canine is considered a cornerstone tooth that plays an important role in aesthetics and function. This study compared the morphometric measurements and morphology of maxillary canines between Saudi and Spanish populations using cone-beam computed tomography (CBCT). Methods: A total of 100 CBCT scans (50 patients from King Khalid University, Saudi Arabia, and 50 patients from University of Barcelona Dental Hospital, Spain) were analyzed in this retrospective cross-sectional study conducted between May and September 2025. The study examined root length, mesiodistal and buccopalatal dimensions, root canal curvatures, apical foramen position, and canal morphology. Results: Canines from the Spanish population were significantly longer than those from the Saudi population (16.9 ± 2.2 mm vs. 13.2 ± 2.5 mm, p < 0.0001). No significant differences were observed in mesiodistal and buccopalatal dimensions. Both groups primarily exhibited mild root canal curvatures and buccally placed foramina. However, the prevalence of palatal foramina (20% vs. 8%, p = 0.04) and oval/ribbon morphologies (52%/12% vs. 22%/6%, p = 0.01) was higher in the Spanish population. The Saudi population showed a greater prevalence of round or irregular canals. The Spanish group was identified as an independent predictor of root length (β = +3.7 mm, p < 0.001), oval canal morphology (odds ratio = 3.8, p = 0.005), and palatal foramina (relative risk ratio = 2.5, p = 0.04). Conclusion: The Spanish population exhibited longer canine roots, associated with oval or ribbon-shaped canal morphologies. In contrast, the Saudi canines displayed shorter length, with more rounded or irregular morphologies.

1. Introduction

The maxillary canine, often referred to as the “cornerstone” of the dental arch, is crucial for occlusion, anchorage, and aesthetics [1]. Its long root provides stability and resistance to occlusal forces, and its position contributes to facial harmony [2]. Differences and variations in root length, canal shape, and curvature directly impact orthodontic biomechanics, endodontic therapy, and surgical outcomes.

Traditionally, the assessment of tooth morphology relies on two-dimensional imaging techniques, including intraoral radiography and orthopantomography (OPG). However, limitations such as magnification, superimposition, and image distortion cannot be overlooked. Cone-beam computed tomography (CBCT) is a three-dimensional imaging modality widely used in dental practice that can provide clinically useful, reproducible linear measurements and improved visualization of root canal anatomy compared with two-dimensional radiography. However, CBCT spatial resolution is constrained by voxel size and image artifacts, including beam hardening and partial-volume effects, which may limit the detection of fine anatomical details. Consequently, micro-computed tomography (micro-CT) provides higher spatial resolution and is appropriately used as an ex vivo reference standard in root canal morphology research and for validating CBCT-derived tooth models [3,4].

CBCT has transformed endodontic and orthodontic imaging, surgical planning, and pathology mapping. Unlike conventional radiography, it provides three-dimensional visualization of root length, root curvature, canal cross-sections, and apical foramina [5,6,7]. Its accuracy makes it a standard tool for assessing tooth morphology [8,9]. Most CBCT morphometric studies have focused on molars and premolars, while few have investigated canines across different populations [10,11,12,13]. CBCT has also been used to investigate within-population anatomic variation related to vertical facial pattern, which can impact dentoalveolar structures such as alveolar bone thickness [14].

CBCT-based studies have reported variability in maxillary canine root length and canal morphology across different populations, emphasizing the need for population-specific anatomic data [15,16,17,18]. Furthermore, the apical foramina exhibit geographic variations; for example, a predominance of buccal forms has been observed in samples from Turkey and Saudi Arabia [19,20]. To the best of our knowledge, no study has compared the morphology and morphometrics of maxillary canines between Saudi and Spanish subpopulations using CBCT. We hypothesized that the morphometric and morphological features of the maxillary canines differ significantly between these two populations.

2. Materials and Methods

2.1. Study Design and Settings

This retrospective cross-sectional study was conducted from May 2025 to September 2025, following the STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) standards. Ethical approval was obtained from the scientific committees of the University of Barcelona Dental Hospital (HOUB) (protocol number: 25/2025) and King Khalid University (protocol number: ECM#2025-504). Archived CBCT images of 100 patients who attended the HOUB and King Khalid University College of Dentistry (COD) were randomly extracted and analyzed. Our predetermined inclusion criteria were as follows: fully erupted maxillary canines with intact roots free from restorations, anomalies, or carious lesions. CBCT images that were free of errors, such as beam hardening or cupping artifacts, and had a diagnostically acceptable quality were included. The exclusion criteria included prior endodontically treated maxillary canines, the presence of pathology, and poor quality of the CBCT images. The analysis of CBCT images was conducted by importing the Digital Imaging and Communications in Medicine (DICOM) files to 3D On Demand Software^® version 1.0 (Build 1.0.10.7462) (x64 Edition).

2.2. Imaging Protocol

The CBCT images were obtained using standardized protocols, with parameters set at 90–100 kVp, 8–10 mA, and a voxel size of 0.2–0.3 mm. The scans of the Saudi cohort were obtained using a KaVo OP 3D Pro CBCT machine (Planmeca, Biberach, Germany). On the other hand, the scans of the Spaniards were obtained using a Planmeca Promax^® 3D Mid-CBCT unit (Helsinki, Finland). Since CBCT images were obtained in two different centers, the inclusion of the images was restricted to those with comparable voxel sizes (0.2–0.3 mm) and acceptable diagnostic quality. All measurements were subsequently performed using the same software after standardized tooth reorientation in multiplanar reconstruction. However, scanner- and protocol-specific differences, such as noise and artifact profiles, may still introduce variability that could be regarded as a limitation. Images were analyzed using CBCT (3D Dental On Demand^®) software. The examiners were calibrated and trained on 20% of the images. Three calibrated examiners conducted all the measurements following a standardized protocol. Prior to formal data extraction, the examiners conducted joint training on tooth orientation in multiplanar reconstruction and on the operational definitions used for each variable. The calibration protocol involved repeating the evaluation of a randomly selected 20% subset within a month interval to assess the interobserver repeatability. The disagreements were resolved by consensus, with confirmation by an experienced oral and maxillofacial radiologist required [21]. The final analysis was conducted on the total samples and repeated at one-month intervals. Where discrepancies were encountered, consensus was reached, and confirmation was obtained from an experienced oral and maxillofacial specialist.

2.3. Variables Analyzed

All measurements were conducted in reoriented multiplanar reconstruction (MPR) after standardizing tooth orientation. For each canine, the volume was rotated so that (i) the long axis of the tooth was aligned vertically in the sagittal and coronal planes, and the cementoenamel junction (CEJ) level was consistently identified circumferentially. Linear measurements were performed using the software measurement tool (3D On Demand Software^®) as follows:

(1)

Root length (coronoapical length) was measured as the linear distance from the midpoint of the CEJ to the most apical point of the root along the long axis of the tooth (Figure 1).

(2)

Regarding buccopalatal diameter, it was measured at the level of CEJ by a line bisecting the tooth on the axial plane (Figure 2).

(3)

Mesiodistal diameter was measured at the CEJ level on the axial plane (Figure 3).

(4)

Since root length was recorded as a straight-line distance, it may slightly underestimate true anatomic length in teeth with pronounced curvature; standardized reorientation was used to capture the maximum tooth length on the plane of measurement. Root canal curvature (angulation) was assessed by scrolling through sagittal and coronal planes. The curvature angle was measured using a Schneider-type approach: a first line was drawn parallel to the canal in the coronal third, and a second line was drawn from the point where the canal began to deviate to the apical foramen; the acute angle between these lines was recorded (Figure 4 and Figure 5). The curvature was categorized as mild (≤5°), moderate (5–20°), or severe (>20°) [22].

(5)

Apical foramen position was evaluated on the axial plane at the level where the major apical foramen was first visible. A buccopalatal reference line was drawn between the external buccal and palatal root surface, and the midpoint of this line was used as the reference. The foramen was classified as buccal if it lay buccal to the midpoint, palatal if it lay palatal to the midpoint, and central if it lay at (or immediately adjacent to) the midpoint (Figure 6).

(6)

Regarding root canal shapes, they were recorded as round, oval, ribbon, teardrop, hourglass, or irregular shape in accordance with previously published reports (Figure 7) [23,24].

2.4. Study Sample

We calculated the sample size of 50 per group using a power calculation targeting a 2–3 mm root-length difference (SD 2.5 mm, α = 0.05, power = 0.8), emphasizing that the primary comparisons achieved a minimum of 90% power. The primary risk of bias encountered in this study was the variation in imaging between the two centers.

2.5. Statistical Analysis

Data were statistically analyzed through IBM SPSS Statistics (SPSS; version 26) and imported into Microsoft Excel 2023 for Microsoft 365 (Microsoft Corp., Redmond, WA, USA), version 2509. Continuous variables, such as root length and transverse dimensions, are represented as means ± standard deviation. Welch’s t-test was used for group comparisons. Categorical variables, including the canal curvature’s severity and the foramina’s shapes, are reported as frequencies (%). The chi-square or Fisher’s exact test was employed, and the p-value was set at <0.05 for the level of significance. Additionally, linear regression was conducted to evaluate root length as a function of population, age, and sex; logistic regression was performed to assess predictors of oval canal morphology; and multinomial regression was conducted to examine predictors of apical foramen position.

3. Results

3.1. Demographics

A total of 100 patients were included, equally divided between Saudi (n = 50) and Spanish (n = 50) populations. The average age of patients from Saudi Arabia was significantly lower than that of patients from Spain (p = 0.003). There was no significant difference in the distribution of sexes (p = 0.23) (

Table 1. Demographic characteristics.

Variable	Saudi (n = 50)	Spanish (n = 50)	p-Value
Age (yrs, mean ± SD)	38.1 ± 14.3	47.1 ± 14.8	0.003 *
Sex (M/F)	30 (60%)/20 (40%)	24 (48%)/26 (52%)	0.23

n, number of patients. * p < 0.05.

). Although sex distribution did not differ significantly between the two cohorts, Spaniards were older than the Saudi cohort (Table 1; p = 0.003). Therefore, age was regarded as a covariate in all multivariable models.

3.2. Continuous Morphometric Measurements

Canines of the Spanish group were considerably longer than those of the Saudi group (p < 0.0001). The mesiodistal dimensions showed a trend toward higher values in Saudis that was not statistically significant (p = 0.07), while the buccopalatal dimensions remained the same (p = 0.28) (

Table 2. Continuous morphometric measurements.

Variable	Saudi Mean ± SD	Spanish Mean ± SD	p-Value
Root length (mm)	13.2 ± 2.5	16.9 ± 2.2	<0.0001 *
Mesiodistal dimension (mm)	6.0 ± 0.7	5.7 ± 0.6	0.07
Buccopalatal dimension (mm)	8.3 ± 0.7	8.1 ± 0.7	0.28

SD, standard deviation. * p < 0.05.

).

3.3. Morphological Characteristics

Both groups exhibited predominantly mild sagittal and coronal curvatures. The apical foramina’s position differed significantly, with a buccal predominance in Saudis (78%). The prevalence of palatally placed foramina was higher in the Spanish population (20%) than in the Saudi population (8%). Canal morphology differed significantly (p = 0.01), with round/irregular shapes primarily present in Saudis and oval/ribbon shapes in Spaniards (

Table 3. Morphological characteristics (categorical variables).

Variable	Category	Saudi n (%)	Spanish n (%)	p-Value
Sagittal curvature	Mild	37 (74)	33 (66)	0.32
	Moderate	13 (26)	17 (34)
Coronal curvature	Mild	41 (82)	38 (76)	0.45
	Moderate	9 (18)	12 (24)
Apical foramen	Buccal	39 (78)	29 (58)	0.04 *
	Central	7 (14)	11 (22)
	Palatal	4 (8)	10 (20)
Canal morphology	Round	18 (36)	10 (20)	0.01 *
	Oval	11 (22)	26 (52)
	Irregular	13 (26)	6 (12)
	Ribbon	3 (6)	6 (12)
	Teardrop	3 (6)	1 (2)
	Hourglass	2 (4)	1 (2)

n, number of patients. * p < 0.05.

).

3.4. Regression Models

Linear regression analysis indicated that being Spanish was independently associated with the root length of the canine (+3.7 mm; 95% confidence interval [CI]: 2.5–4.9; p < 0.001). No significant effect of age or sex was observed (

Table 4. Linear regression: predictors of root length.

Predictor	β (SE)	95% CI	p-Value
Spanish vs. Saudi	+3.7 (0.6)	2.5–4.9	0.001 *
Age (per year)	+0.02 (0.01)	−0.01–0.05	0.18
Sex (Male vs. Female)	+0.3 (0.5)	−0.7–1.3	0.55

β, beta coefficient; SE, standard error of mean; CI, confidence interval. * p < 0.05.

).

For the regression analysis, canine morphology was classified into oval and non-oval forms. Being of Spanish heritage significantly increased the probability of exhibiting an oval morphology (odds ratio [OR], 3.8; 95% CI, 1.5–9.4; p = 0.005); however, age and sex were not recognized as significant predictors (

Table 5. Logistic regression: oval canal morphology.

Predictor	OR (95% CI)	p-Value
Spanish vs. Saudi	3.8 (1.5–9.4)	0.005 *
Age (per year)	1.01 (0.98–1.05)	0.42
Sex (Male vs. Female)	0.9 (0.4–2.1)	0.81

OR, odds ratio; CI, confidence interval. * p < 0.05.

).

A multinomial regression model was utilized to analyze the placement of the apical foramen, with the buccal position as a reference point. Individuals of Spanish origin had a higher risk of experiencing palatal canal positioning (

Table 6. Multinomial regression for analyzing the position of the apical foramen.

Predictor	Central RR (95% CI)	p-Value	Palatal RR (95% CI)	p-Value
Spanish vs. Saudi	1.6 (0.6–4.2)	0.35	2.5 (1.0–6.6)	0.04
Age (per year)	1.01 (0.98–1.04)	0.52	0.99 (0.96–1.02)	0.60
Sex (Male vs. Female)	1.2 (0.5–3.0)	0.65	1.0 (0.4–2.8)	0.91

RR, relative risk ratio; CI, confidence interval.

), while no significant difference was observed in the positioning of the central foramen. Age and sex were considered non-significant predictors.

4. Discussion

The present study provides a comparative assessment of maxillary canine morphometry and morphology in populations from Saudi Arabia and Spain using CBCT. The findings indicate that the maxillary canine typically possesses a single robust root and a straightforward canal system, although the two groups exhibited very different root lengths, canal shapes, and positions. The variations between the two cohorts regarding root length and canal morphology may reflect a combination of true biologic variation and study-level factors. These potential factors include genetic background, environmental influences, age distribution, inclusion criteria, and methodological differences in landmark definition and measurement. In our study, age differed between the two populations, as age-related dentin deposition may influence canal geometry and cross-sectional appearance. Although we employed harmonized inclusion criteria and standardized post-processing, CBCT acquisition across the two different centers may contribute to variability in image noise and artifact profiles. These factors could partially explain the discrepancies observed between the cohorts and indicate the need for larger, prospective, multicenter studies. Age is a potential confounder in morphometric and endodontic morphology studies because secondary dentin deposition and canal calcification progress over time. In the present sample, the Spanish group was older on average; therefore, we adjusted all regression models for age and sex. While age was not a statistically significant predictor in the adjusted models, the confounding remains possible and should be considered when interpreting the findings between populations. These findings highlight the importance of CBCT in revealing meticulous changes in anatomy and provide insights into population-based data. The permanent maxillary canines are among the strongest teeth in the anterior segment; they exhibit long roots and prominent crowns. Radiographic studies across populations have consistently reported that the coronoapical length of maxillary canines is the greatest among the anterior teeth, averaging approximately 25–27 mm, with minor variations depending on the population and measurement method [25,26]. The reliable measurements of root length of permanent maxillary canines across populations can be obtained from radiographic and CBCT-based studies. A large Chinese study, which conducted a morphological analysis of the anterior permanent dentition using CBCT, reported mean root lengths of 16.78 ± 1.94 mm on the right and 16.54 ± 2.11 mm on the left for maxillary canines [15]. Similarly, a Pakistani CBCT-based study reported the average root length of the maxillary canine to be approximately 15.49 mm [27]. An Indian study utilizing CBCT reported that the average anatomical root length for maxillary canines is 16.82 mm [2]. An analysis of an Italian anatomical series of anterior teeth reported mean canine root lengths of approximately 16.4 mm (right) and 16.6 mm (left), measured from the CEJ to apex [28]. The Spanish population in the current study had significantly longer roots than the Saudi population (p < 0.001), which is clinically valuable for predicting the working length in endodontics, particularly when CBCT or other precise imaging is available.

In the present study, the mesiodistal widths of the maxillary canines in the Saudi and Spanish populations were 6.0 ± 0.7 mm and 5.7 ± 0.6 mm, respectively, suggesting a non-significant tendency toward larger values in the Saudi population (p = 0.07). The crown’s mesiodistal breadth, typically ranging from 7.0 to 8.0 mm, has been documented in multiple investigations, including those employing CBCT and digital model analysis, which confirm its relatively consistent dimensions across diverse ethnic groups [23,24]. A recent study by Aldhuwayhi et al. [29] reported mesiodistal widths of 8.12 ± 0.58 mm for the maxillary left canine and 8.00 ± 0.81 mm for the maxillary right canine, as measured using digital calipers. The buccopalatal dimension, generally larger than the mesiodistal measurement, averages 8.0–9.0 mm [30]. Similar findings regarding root curvature were observed in the current study, wherein the mean values were 8.3 ± 0.7 mm and 8.1 ± 0.7 mm in the Saudi and Spanish populations, respectively. Together, these morphometric characteristics highlight the maxillary canines’ functional and aesthetic significance. Radiographic investigations across different populations underscore the relative stability of its dimensions, with only minor regional variations.

Studies on the curvature of maxillary canine roots, particularly in sagittal and coronal planes, indicate that the curvatures are generally mild. Despite some variations, most roots maintain a relatively straight trajectory from the coronal to apical thirds. According to Sahebi et al., root dilacerations in maxillary canines are rare in the Iranian population, with mild distal curvatures most frequently observed in the apical third [31]. Similar findings were observed in the current study, with no significant differences between the Saudi and Spanish populations. Collectively, these findings underscore that while maxillary canine roots are predominantly straight, mild distal or apical curvatures can occur, thus emphasizing the importance of preoperative imaging for accurate treatment planning.

CBCT and other imaging modalities have been used to study the position of the apical foramen in maxillary canines, revealing that it is most frequently located slightly buccally relative to the anatomical apex [32,33,34]. In the current study, significant differences in the positions of the apical foramina were observed, with a buccal predominance in the Saudi population compared to the Spanish population. Conversely, the prevalence of a palatally placed foramen was higher in the Spanish population (20%) compared to the Saudi population (8%). In a recent micro-CT study of maxillary anterior teeth, the apical foramen was most frequently located in the mesiobuccal region of the canines [35]. Another morphometric analysis of the apical foramina in extracted maxillary anterior teeth revealed that the apical foramen in maxillary canines was most frequently located in the palatal region, followed by the central position [36]. These findings indicate that though the apical foramen is typically located near the root apex, slight buccal or distal deviations can occur, which is clinically relevant for endodontic treatment planning, as it guides the direction of canal instrumentation and minimizes the risk of procedural errors.

The cross-sectional root canal morphology of maxillary canines can influence endodontic treatment strategies. Razumova et al. [37] used CBCT to examine the root canal’s cross-sectional shape at various levels among residents in Moscow and reported that it remains consistently oval along the root length. A recent CBCT study of 330 patients in the Middle East evaluated the root canal cross-sectional shapes in maxillary canines and reported that the dominant shape in the coronal third was oval, transitioning to circular in the middle and apical thirds [38]. Interestingly, the morphology of the canal differed significantly (p = 0.01) between the two groups in the present study, with round/irregular shapes predominating in the Saudis and oval/ribbon shapes predominating in the Spaniards. These findings emphasize the complexity and variability of maxillary canine root canal morphology. Understanding these variations is crucial for endodontists to develop effective treatment plans and select appropriate instruments to navigate the diverse canal anatomies encountered in clinical practice.

A regression analysis was conducted using the primary clinically relevant variables in this study—the root length, canal morphology, and the position of the apical foramen. Being Spanish was independently associated with the canine’s root length (p < 0.001); no significant effects of age or sex were observed. Several population-based radiographic and CBCT studies have examined factors influencing the root length of permanent maxillary canines. Sex has been shown to significantly affect root dimensions, with males generally exhibiting slightly longer roots than females by about 0.5–1.0 mm on average [2,39]. Population origin is another important factor; comparative analyses indicate variations in canine root length across ethnic and geographic groups, with Chinese and Indian samples averaging around 16–17 mm and European samples reporting similar but slightly variable means depending on the measurement technique [11,40]. Collectively, these findings suggest that despite root length being a relatively stable anatomical feature, sex and origin consistently emerge as predictors.

In the present study, multinomial regression was employed to evaluate predictors of apical foramen position, allowing for the assessment of the relative contributions of sex, age, and root dimensions. Individuals of Spanish origin had a higher risk of experiencing palatal canal positioning, while no significant difference was observed in the positioning of the central foramen. Regarding clinical implications, knowledge of canine morphology in different populations can provide an evidence-based practice for endodontic planning. Longer roots may require careful working-length control and selection of instruments appropriate to the canal length and taper. The described shapes of oval, ribbon, and irregular are clinically relevant, as the non-round spaces may be insufficiently approached by standard rotary instrumentation. This would increase the reliance on effective irrigation when indicated and obturation approaches that adapt to non-circular anatomy. Additionally, the awareness of apical foramen position may assist in reducing over-instrumentation and improving apical control during shaping and obturation.

The study’s findings are broadly consistent with earlier descriptive reports, thus strengthening the evidence that apical foramina in maxillary canines are frequently eccentric and not always centrally located.

Limitations: Considering the limitations of our study, the study included 50 canines per cohort, which is regarded as adequate for the prespecified comparisons. However, this may not fully represent the entire population. Therefore, larger multicenter samples would improve generalizability. Furthermore, we acknowledge that age represents a potential confounder in morphometric and endodontic morphology studies since secondary dentin deposition and canal calcification progress over time. In the present study, the mean age of Spaniards was older; therefore, we adjusted all regression models for age and sex. While age was not a statistically significant predictor in the adjusted models, the confounding remains possible and should be considered when interpreting between-population differences. Additionally, some outcomes required categorical morphology classification, which may introduce observer subjectivity. To minimize this, we used a standardized protocol with examiner calibration and repeated assessment of a randomly selected 20% subset within a one-month interval. Furthermore, the CBCT data were retrieved from two different centers; despite harmonized inclusion criteria and standardized post-processing, inter-device and protocol differences could have influenced measurement precision. Finally, while CBCT enables in vivo assessment, it has lower spatial resolution in comparison to micro-CT and may therefore be less accurate for fine structures at the root apex. This should be considered when interpreting subtle differences. In relation to future direction, future work should include larger and prospectively harmonized cohorts with standardized CBCT acquisition parameters. Also, it is recommended that additional covariates be included, such as craniofacial pattern. Regarding protocols, future studies should report observer agreement for both continuous and categorical outcomes. Studies linking these anatomic findings to clinical outcomes such as treatment difficulty, procedural errors, and healing would further clarify clinical relevance. Regarding root canal measurements, they were measured in our study using a two-dimensional linear approach. However, a three-dimensional approach utilizing CBCT can improve accuracy for length measurements in curved canals compared with simple 2D approaches. Consequently, it is recommended that such an approach be applied in future studies, particularly when canal length or curvature is a target [41].

5. Conclusions

To the best of our knowledge, this is the first study to conduct a comparative analysis of the morphology and morphometrics of the maxillary canines between Saudi and Spanish subpopulations using CBCT. The findings demonstrate notable inter-population differences in certain dimensional and anatomical features, underscoring the influence of genetic and developmental factors on tooth morphology. These results have practical implications for clinical procedures, such as endodontics, orthodontics, and forensic identification, emphasizing the importance of considering population-specific anatomical variations in treatment planning and anthropological assessments.