Cone-Beam CT Assessment of the Canalis Sinuosus in an Indian Population: A Retrospective Imaging Study

Sample size calculation

Using the statistical parameters obtained from the study by Samunahmetoglu et al.⁵ the sample size was calculated as 245, using the formula where:

z α/2: the critical value from the standard normal distribution corresponding to a significance level of α/2

p: the estimated proportion of the population

e: the desired margin of error.

where p was derived from the prevalence reported in a previous CBCT study of the CS and e represented the desired margin of error.

Image Acquisition: The scans were acquired using Promax 3D Mid (Planmeca Oy, Helsinki, Finland) CBCT unit, with subsequent analysis conducted using the manufacturer’s software, Romexis 4.0.12 R (Planmeca Oy, Helsinki, Finland). The exposure parameters adhered to the standard default settings of the device, which are contingent upon the Field of View (FOV). Specifically, these parameters were set at 90 kVp, 8 mA, 12.5 s. The images were reconstructed using Romexis software version 4.6.2.R.

Medium FOV scan volumes that covered the entire maxilla with voxel size ≦200 μm were selected for the study. Patients above 16 years and without any pathologies in the anterior maxilla up to the molars were included in the study. Conversely, patients who were less than 16 years old, had undergone orthodontic treatment or orthognathic surgery were excluded. Additionally, individuals with cranial anomalies, syndromes, trauma or surgery, or endocrine disorders were also excluded. The presence of impacted teeth retained roots, dental implants, restorations, foreign bodies, or pathological lesions in the anterior maxillary area further disqualified patients from participation. Moreover, low dose CBCT images and images with artifacts were excluded to ensure image quality and accuracy.

All CBCT images were examined in axial, coronal, and sagittal planes for the presence of CS. The distance at which they emerge in relation to the nasal cavity floor, the ridge’s buccal cortical bone and the alveolar ridge crest was measured using CBCT.

Image Evaluation: All the scans were evaluated for the following parameters:

Presence or absence of CS ( Figure 1)

Figure 1. Presence of Canalis Sinuosus.

CS position with respect to lateral incisors in different sections ( Figure 2)

Figure 2. Image shows CS adjacent to the palatine root of the left central incisor in the a) Coronal, b) Sagittal, c) Axial images, d) 3D.

Distance of CS from cortical plates, alveolar crest and nasal floor ( Figure 3)

Figure 3. Measurement of the distance from the opening of the CS to three anatomical landmarks- the alveolar ridge crest, to the buccal cortical margin and to the floor of the nasal cavity in the cross-sectional image.

Diameter of the canal ( Figure 4)

Figure 4. Measurement of the diameter of the CS located near the palate of the left central incisor in axial section.

Statistical analyses were conducted utilizing the Statistical Package for Social Sciences (SPSS 25), SPSS Inc, Chicago, IL. Descriptive statistics for continuous variables were presented using mean, standard deviation, median, and interquartile range, while frequency distribution was employed for categorical variables. The canal dimensions, specifically length and diameter, were compared between sexes using an independent t-test. The presence or absence of canals was assessed using a chi-square test to compare males and females. Additionally, the proximity of the canals to the tooth was evaluated using chi-square test. A p-value of <0.05 was considered statistically significant.

Sample characteristics

A total of 245 individuals were included in the study, with a mean age of 44.46 ± 15.15 years (median: 45). Among them, 134 (54.7%) were females and 111 (45.3%) were males.

Detection of the CS

CS was observed in the study population in 67.3% of the patients, with 137 individuals (55.9%) exhibiting it on both sides and 28 individuals (11.4%) presenting with unilateral presence. The canal was absent in 80 individuals (32.7%). When assessed separately for each side, the CS was observed on the left in 153 individuals (62.4%) and on the right of 149 individuals (60.8%).

Location of CS

The analysis of the CS’s proximity to specific teeth revealed distinct patterns. On the left side, the canal was predominantly associated with the lateral incisor, accounting for 68 cases (44.7%), followed by the central incisor with 63 cases (41.4%), and the canine with 21 cases (13.8%). Conversely, on the right side, the lateral incisor showed the highest association with 76 cases (50.3%), followed by the central incisor at 50 cases (33.1%), and the canine at 25 cases (16.6%). Further examination of the spatial relationship between the CS and adjacent teeth indicated that, on the left side, the canal was positioned palatally in 81 cases (53.3%), disto-palatal in 49 cases (32.2%), and mesio-palatal in 22 cases (14.5%). A similar distribution was observed on the right side, with the canal located palatally in 75 cases (49.7%), disto-palatal in 40 cases (26.5%), and mesio-palatal in 36 cases (23.8%). Statistical analysis using Pearson’s Chi-square test confirmed a significant correlation between the CS location and tooth proximity on both the left (χ² = 18.164, df = 4, p = 0.001) and right sides (χ² = 9.521, df = 4, p = 0.049).

Metric evaluation

The mean diameter of the CS near the alveolar crest was measured at 0.76 mm (±0.27) on the left side and 0.80 mm (±0.27) on the right side. The distance from the CS to the alveolar crest was recorded as 9.23 mm (±3.58) on the left side and 9.22 mm (±3.39) on the right side. The distance from the CS to the buccal cortical plate was 7.19 cm (±1.65), with a median of 7.18 cm, on the left side and 6.82 cm (±1.74) on the right side. Additionally, the distance from the CS to the floor of the nasal cavity was 11.4 cm (±3.78) on the left side and 11.6 cm (±3.64) on the right side ( Figure 5).

Figure 5. Diameter and location of the CS in both sexes.

Gender-based evaluation

The presence of the CS did not demonstrate a statistically significant association with sex (χ² = 3.247, p = 0.197). It was absent in 35.1% of females and 29.7% of males, present unilaterally in 8.2% of females and 15.3% of males, and present bilaterally in 56.7% of females and 55% of males. The presence of the CS on the left side revealed no significant sex-based difference, being absent in 38.1% of females and 36.9% of males, and present in 61.9% of females and 63.1% of males. Similarly, on the right side, there was no significant difference between sexes in its presence, with absence rates of 40.3% in females and 37.8% in males, and presence in 59.7% of females and 62.2% of males.

The analysis of tooth proximity on the left side revealed no significant association with sex (χ² = 0.225, p = 0.894). The highest frequency of proximity was observed near the lateral incisor (45.8% in females, 43.5% in males), followed by the central incisor (39.8% in females, 43.5% in males), and the lowest frequency was near the canine (14.5% in females, 13% in males). Similarly, on the right side, no significant difference was detected (χ² = 0.658, p = 0.720). The lateral incisor exhibited the highest frequency of proximity (47.6% in females, 53.6% in males), followed by the central incisor (34.1% in females, 31.9% in males), and the canine (18.3% in females, 14.5% in males).

The spatial orientation of the CS in relation to the tooth exhibited no statistically significant differences based on sex, on either the left side (χ² = 0.554, p = 0.758) or the right side (χ² = 3.057, p = 0.217). On the left side, the canal was predominantly located palatally (50.6% in females, 56.5% in males), followed by a disto-palatal position (33.7% in females, 30.4% in males) and a mesio-palatal position (15.7% in females, 13% in males). Similarly, on the right side, the palatal location was most prevalent (53.7% in females, 44.9% in males), succeeded by the disto-palatal (28% in females, 24.6% in males) and mesio-palatal (18.3% in females, 30.4% in males) positions.

In general, males exhibited larger measurements in both diameter and distance from various CS landmarks compared to females. Notably, the diameter on the left side was significantly larger in males (0.8 ± 0.29) than in females (0.7 ± 0.23), with a p-value of 0.008. Although the right side showed a similar pattern, the difference was not statistically significant. The distance from the CS to the alveolar crest was similar for both genders. However, the distance from the CS to the buccal cortical plate was significantly greater in males, measuring 7.78 mm on the left and 7.53 mm on the right, with a p-value of less than 0.001. Furthermore, the distance from the CS to the floor of the nasal cavity was significantly greater on the right side, with males having a mean value of 12.44 mm compared to 10.89 mm in females, and a p-value of 0.011 ( Table 1)

Overall, notable differences were found in the diameter near the alveolar crest (left), the distance from the CS to the buccal cortical plate (both sides), and the distance from the CS to the floor of the nasal cavity (right), all of which were greater in males. Although these sex-related differences are modest in absolute magnitude, they suggest that a uniform safety margin may not be appropriate for all patients, particularly in anterior maxillary regions with limited bone volume. Other parameters did not exhibit statistically significant differences between the two groups.

Position of CS

While CS can present in various anatomical locations in the anterior maxilla, it predominantly occurs in the region adjacent to the palate in the incisor and canine areas.¹⁹ This distribution aligns with the findings of our study and corroborates the observations documented by Manhães Júnior LR et al.² as well as Anatoly A et al.¹³ and Samunahmetoglu E et al.⁵

Metric evaluation

Diameter: The mean diameter of the CS is generally reported to be around 1 mm.^14,19,20 However, in our study, we observed a mean diameter slightly less than 1 mm, which is consistent with the findings of Ghandourah AO et al.¹² and Khojastepour L,¹⁵ although other studies have documented measurements exceeding 1 mm.^4,5,21,22 While the precise relationship between canal diameter and the likelihood of complications remains uncertain, it is noteworthy that a larger neurovascular bundle may increase the risk of surgical issues, particularly bleeding. Furthermore, an increased canal diameter can potentially lead to misinterpretation of periapical lesions on standard radiographs.⁵

Distance from Adjacent Structures: In our study, the distance measured from the CS to the alveolar crest was slightly over 9 mm, closely aligning with the findings of Manhães et al.² In contrast, Gürler et al. reported a significantly greater distance of 16.81 mm.¹⁸ Meanwhile, Samunahmetoğlu E. and Kurt MH⁵ found a distance of 7.71 mm, and Beyzade Z et al.¹⁶ reported 5.87 mm, both slightly less than our result. The distance from the CS to the buccal cortical plate was over 7 mm, consistent with the findings of Manhães et al.² However, Beyzade Z¹⁶ and Samunahmetoğlu, E. and Kurt, M.H.⁵ found it to be less than 5 mm in their study. In our study, the distance measured between the CS and the nasal cavity exceeded 11.4 mm, aligning with the observations reported by Manhães et al.²

Occurrence

The presence or absence of CS, as well as its lateral positioning, did not demonstrate a statistically significant association with sex. In both male and female subjects, the proximity of CS was closest to the lateral incisor, followed by the lateral incisor and the canine on both sides, which was statistically insignificant. The location of CS relative to the tooth also exhibited no significant differences based on sex, with it most frequently positioned palatally, followed by disto-palatal and then mesio-palatal. In the analysis of CS in relation to sex, no statistically significant correlations were identified concerning its presence, position, proximity to teeth, or location. These findings are consistent with the results reported by Aoki R et al.¹⁴

Gender-based evaluation

The CS exhibited a larger diameter near the alveolar crest in males compared to females. This difference was statistically significant on the left side, while no significant variation was observed on the right side. Gurler et al., Machado et al., and Shan et al. found that the diameter was greater in males.^18,20,23 Gurler suggested that the increased diameter in males could be attributed to generally wider anatomical structures.¹⁸ However, this observation contrasts with the findings of Samunahmetoglu, E., Kurt, M.H., and Von Arx, who reported no correlation between diameter and sex.^5,22 Our study revealed that the distance from the CS to the alveolar crest was greater in males than in females on both sides, though this difference was not statistically significant. However, the distance of CS to the buccal cortical plate was significantly larger in males on both sides and was statistically significant. Despite the overall trend of larger measurements in males, a study by Manhães reported a statistically significant difference in the distance from the CS to the buccal cortical plate in females.² Furthermore, the distance from the CS to the floor of the nasal cavity on the left side was slightly greater in males than in females on both sides. However, this difference did not reach statistical significance. These findings are consistent with the observations made by Manhães and Samunahmetoglu, E., and Kurt, M.H., who also reported that all measured parameters tended to be greater in males, in line with our study results.^2,5

Overall, significant differences were observed in the diameter near the alveolar crest (left), distance from the CS to the buccal cortical plate (both sides), and distance from the CS to the floor of the nasal cavity (right), all of which were larger in males. Between the two groups, no statistically significant differences were observed.

Limitations and future directions

This study has several limitations. First, its retrospective, single-centre design and purposive sampling may limit the generalizability of the findings to other Indian or South Asian populations. Second, the analysis relied solely on CBCT imaging and was not correlated with clinical outcomes, such as the occurrence of CS-related complications after implant placement. Third, only patients with intact maxillary incisors and canines were included, which may introduce selection bias. Future multi-centre studies that combine CBCT evaluation with clinical follow-up could help validate and further refine the morphometric parameters reported here.