Nigerian Journal of Clinical Practice

: 2021  |  Volume : 24  |  Issue : 11  |  Page : 1596--1601

Morphological evaluation of the incisive canal with reference to gender and age: A cone-beam computed tomography study

AI Linjawi, MA Othman, AA Dirham, SH Ghoneim, SR Aljohani, RR Dause, HY A Marghalani 
 Department of Orthodontic, Faculty of Dentistry, King Abdulaziz University, P.O. Box 80209, Jeddah, Saudi Arabia

Correspondence Address:
Dr. A I Linjawi
Department of Orthodontic, Faculty of Dentistry, King Abdulaziz University, P.O. Box 80209, Jeddah - 21589
Saudi Arabia


Background: The incisive canal (IC) is an important anatomical structure in the premaxilla that should be considered during many dental procedures. Aims: The objective of this study is to associate the IC morphology and dimensions with reference to gender and age by means of cone-beam computed tomography (CBCT). Patients and Methods: A retrospective study was conducted using archived CBCT records of patients who sought treatment at the Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia. OnDemand 3D Imaging software was utilized in image reconstruction and measurement determination. The parameters evaluated were the IC shape and dimensions in a sagittal and coronal view at two levels: palatal opening and nasal opening. The variables were compared according to age and gender using one-way Analysis of Variance (ANOVA) and Kruskal Wallis tests. Confidence level was obtained at P < 0.05. Results: Out of the 370 CBCT images assessed, only 100 images fulfilled the inclusion criteria; 50 males and 50 females. No substantial variance in IC shapes was found in both the sagittal and coronal perspectives with reference to age and gender. Likewise, there was no statistical variation in IC dimensions with reference to age. On the other hand, there was a statistical difference in IC length when correlated with gender as the male subjects had longer IC as compared to females (P < 0.01). Conclusion: There is no association between IC morphology, age and gender. However, substantial variation in IC length was observed between genders.

How to cite this article:
Linjawi A I, Othman M A, Dirham A A, Ghoneim S H, Aljohani S R, Dause R R, A Marghalani H Y. Morphological evaluation of the incisive canal with reference to gender and age: A cone-beam computed tomography study.Niger J Clin Pract 2021;24:1596-1601

How to cite this URL:
Linjawi A I, Othman M A, Dirham A A, Ghoneim S H, Aljohani S R, Dause R R, A Marghalani H Y. Morphological evaluation of the incisive canal with reference to gender and age: A cone-beam computed tomography study. Niger J Clin Pract [serial online] 2021 [cited 2021 Nov 28 ];24:1596-1601
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Full Text


The IC, which is similarly referred to as nasopalatine canal (NPC), or anterior palatine canal, is an anatomic structure positioned on the middle plane of the maxillary palatine process behind the maxillary central incisor roots. It is deemed as the most significant anatomical structure situated in the premaxilla as it serves as a gateway amid the nasal and oral cavities.[1] It also links both incisive and nasal foramina (also identified as the foramina of Stenson), which is positioned adjacent to the nasal septum. It is surrounded by dense cortical bone through which the nasopalatine vessels and nerves pass. It comprises the incisive nerve and the sphenopalatine artery, which is the end branch of the downward nasopalatine artery.[2],[3]

The frontal part of the maxilla is an expanse that frequently undertakes dental, orthodontic and maxillofacial surgical procedures, such as periodontal and orthognathic surgery, and surgically aided rapid palatal expansion.[4] Additionally, the frontal maxilla is disturbed by maxillary surgery,[5] neck and trauma,[1],[3],[4] upper central incisor movement,[6] and nasopalatine channel cyst enucleation, impacted teeth extraction or mesiodens.[7] The closeness amid the roots of the upper central incisor and the cortical walls of the nasopalatine canal might lead to incisor root resorption during orthodontic maximum retraction of incisors.[6],[8] To prevent these potential complications, systematic preparation and thorough radiological analysis of IC dimensions and morphology should be accurately assessed prior to any dental procedures with reference to anterior maxillary area in the vicinity of this anatomical structure.

IC morphology was found to be different between people groups with contentious findings regarding the relationship between the incisive canal morphology and age or gender. Nevertheless, limited information about IC dimensions, morphology as well as anatomical variations are presented in literature and are frequently documented as case studies.[9],[10],[11],[12]

Mardinger and colleagues proposed the anatomical organization of the IC profile in the sagittal cross-sections of the skull.[13] IC shape was classified into four key types; banana-like, cylindrical-like, hourglass-like, and funnel-like.[13] Furthermore, the canal in the coronal view was categorized by Bornstein and others[9] into single canal opening (1 oral and 1 nasal foramina), 2 parallel canals (2 oral 2 nasal foramina, with septum that separates the IC), as well as Y-type canal disparities (1 oral and 2 or more nasopalatine foramina). A cylindrical IC shape was found to be the most observed profile as reported by Thakur and colleagues.[14] Analogous findings were also described in many studies on IC morphology.[3],[13],[15],[16],[17],[18],[19],[20] In contrast, the common IC profile for both dentulous (50%) and edentulous maxilla (45%) in Tokyo population was found to be of funnel-like shape according to the research conducted by Fukuda and others.[21] Mraiwa and colleagues,[11] on the other hand, discovered that the Y-shaped profile was common in the coronal view in the UK population.

In terms of IC dimension assessment, mean IC length in the sagittal plane was reported to be approximately 10-12 mm.[5],[7],[14],[19],[20],[21] Even so, several studies observed a longer IC,[4],[18] whereas other researchers reported 8-9 mm IC length, which is deemed shorter as compared to other findings.[3],[11] Remarkably, multiple researches mentioned a shorter IC length for female participants as compared to male counterparts.[3],[4],[6],[8],[14],[19],[20] Likewise, Fernández-Alonso and colleagues[16] reported the association of declining IC length with advancing age, whereas Liang et al.[3] observed direct linear relationship between IC length and age. Yet, some studies observed no connection between the IC length and age.[4],[6]

IC morphology can be evaluated using numerous imaging techniques, such as computed tomography (CT),[5],[9] micro-CT,[22] spiral CT[3],[10] and high-resolution magnetic resonance imaging.[10] Furthermore, CBCT has served as a novel diagnostic leeway in the dentistry field. CBCT is deemed advantageous due to removed superimposition effect and improved resolution in comparison to spiral tomography. Likewise, other advantages include more rapid imaging time, minimal radiation dose[11],[23],[24],[25] as well as detailed three-dimensional assessment of IC profile in the anterior maxilla.[11]


This research aimed to compare the IC morphology and dimensions with reference to age and gender using CBCT.

 Material and Methods

Study design

A retrospective approach was utilized using archived CBCT records of patients who sought treatment at King Abdulaziz University, Faculty of Dentistry, Jeddah, Saudi Arabia. The study was approved by the Ethical Committee of the same institution with Ethical no.: [100-06-19]. The study was approved by the Ethical Committee at King Abdulaziz University, Faculty of Dentistry, Jeddah, Saudi Arabia with Ethical no.: [100-06-19] on July 30, 2019.

Sample selection

Three hundred and seventy archived CBCT records (n = 370) were screened using the following inclusion criteria: (1) CBCT image for at least the maxilla was taken, (2) no record of orthodontic treatment, (3) no lost or supernumerary maxillary incisors, (4) no prosthodontic maxillary incisor treatment, (5) no apparent nasopalatine pathology, (6) no records related to maxillary incisors' trauma and (7) no congenital anomalies such as cleft lip and palate.

CBCT images

All CBCT scans were attained with the following specifications: 1 mm slice breadth as well as exposure settings of 120 kV, 15 mA and 12-inch field. Image reconstruction and measurement was determined using OnDemand 3D Imaging software (Seoul, Korea). The assessed parameters include IC shape and dimensions from the sagittal and coronal view.

Study groups

Two key considerations were established: age and gender. The former was further classified into four groups, <= 20, 21-40, 41-60, and above 60 years of age.

Incisive canal shape assessment

Anatomical features of the IC were assessed on the sagittal reconstruction according to the following classification [Figure 1]a, [Figure 1]b, [Figure 1]c, [Figure 1]d[13]:{Figure 1}


In the case of no shape resemblance for the nasopalatine canal, the subject was categorized as ''others.''

On the coronal reconstruction, the canal was classified according to its type as follows [Figure 2]a, [Figure 2]b, [Figure 2]c, [Figure 2]d[9]:{Figure 2}

Single canal (1 nasopalatine and 1 incisive foramina),2 parallel canals (2 nasopalatine and 2 incisive foramina, with a bony septum present in the NPC), andY-type canal disparities (1 incisive foramen with >=2 nasopalatine foramina).

Incisive canal dimensions

The horizontal reference plane in determining the orientation of the axial plane is the Frankfort-horizontal (FH) plane. The sagittal plane was determined to be upright with reference to the axial plane and parallel with reference to the plane that passes through the posterior and anterior nasal spines.

Linear and area measurements were then determined on the sagittal reconstruction. The dimensions measured were [Figure 3]:{Figure 3}

The IC surface area (mm2)The IC length: by drawing a line parallel to the incisive canal angulation and extends from the IC palatal opening to the IC nasal opening.The IC width at the palatal openingThe IC width at the nasal opening.

Measurement error

More than one examiner, including an associate professor, who were trained, calibrated and experienced in identifying landmarks and structures related to the area of interest. Intra- and inter-examiner error were attained by repetitive measurements within a 2-week interval on 10 arbitrarily selected subjects. The intra- and inter-examiner reliability were then computed using the intra-class correlation coefficient. However, in order to increase reliability and decrease bias and variations related to calibration in between the observers, it was decided that a single observer (most experienced) will continue the measurements.

Statistical analysis

IC shape data were presented as frequencies and percentages. Descriptive and group comparison for IC shape was computed using Mann Whitney U and Kruskal Wallis tests. Descriptive and group comparison for IC linear and area measurements were calculated using one-way ANOVA proceeded by Post Hoc Tukey's test and independent sample t-test. The obtained data were tabulated in an Excel sheet and statistical analysis at 95% confidence level was performed with the aid of IBM SPSS statistics for Windows, version 22.0 (IBM Corp., Armonk, NY).


One hundred archived CBCT images, which comprised of 50 male and 50 female participants, was able to fulfill the inclusion criteria out of the 370 images assessed by the examiner. A high correlation (intra-examiner r = 1.000; inter-examiner r = 0.8) was reported for IC shape assessment in the coronal view, whereas an acceptable correlation (intra-examiner r = 0.8; inter-examiner r = 0. 0.646) were obtained for that in the sagittal view.

In terms of IC shape in the sagittal view, about 36% of the total participants had a funnel-shaped IC, which were mostly females and aged between >20 and 40 years. Second, a cylinder-like IC shape was common in every 3 out of 10 participants, which were mostly males. Hourglass-shaped IC was found in 28% of the subjects with a 1:1 ratio for male to female. Lastly, banana-like IC shape was found in only 6% of the sampling population, which were aged between >20 and 40 years. Statistical analysis revealed no association between IC shape, age and gender [Table 1].{Table 1}

Single palatal IC shape in the coronal view was found to be present in 71% of the sampling population as to which majority were females and aged between >20 and 40 years. This is followed by the Y-type canal at 27%, which is commonly present in male subjects aged >20 and 40 years old. The remaining 2% were accounted for 1 male and 1 female subjects with 2 parallel canals. At 95% confidence level, there is no substantial relationship between IC shape, age and gender [Table 2].{Table 2}

In terms of IC dimensions, male subjects were determined to have a higher surface area, length and width at both palatal and nasal openings. However, there is a substantial variation in the IC length of male subjects when compared to the female counterparts. On the other hand, a larger surface area was obtained for those aged between >40 and 60 years. Longer IC length of 12.69 was reported for subjects aged less than and equal to 20 years. Lastly, IC thickness at both palatal and nasal openings were reported to be higher for participants who were at least 60 years of age. Statistical analysis provided no substantial association between each IC dimension and age [Table 3].{Table 3}


Proper assessment and understanding of IC anatomy are deemed critical prior to any orthodontic treatment due its closeness to the roots of central incisors.[26] CBCT is deemed advantageous as it provides a precise imaging of the anatomic features[5],[27],[28] before determining the exact location of the implant.[29]

This research evaluated the IC morphology and dimensions with reference to age and gender using CBCT. Similar to the findings of many studies, the funnel- and cylinder-like IC shapes were the most common shapes.[1],[14],[15],[16],[17],[18],[19],[20] Also, similar to the findings of Thakur and colleagues,[14] Nasseh and others[17] and Safi and colleagues,[19] banana-shaped IC was found to be the least frequent in the current study.

Regarding the coronal view, the variation in the shape from having the single canal as the most common and the two parallel canals to be the least common, which is similar to the findings of many other studies.[1],[18]

The variations in the IC shape are explained by Bornstein et al.[9] as representing the IC development and coalescence at the nasal and palatal openings.[30] However, the IC shape was found to vary widely among different ethnicities.[30]

The larger surface area, length and width at palatal opening of the IC in males when compared to females was also reported in many studies.[1],[14],[17],[19],[31],[32] The age group of 60 years old or more had higher values for surface area and thickness at both palatal and nasal openings which might be related to the cumulative growth they achieved during aging. On the other hand, the longer IC length was found to be in the younger age group (<=20 years old) which can be explained by the fact that they have not experienced enough remodeling at the nasal and oral cavity which can shorten the IC length.[19]

Methodologic variations,[14],[29] such as determination of specified areas of interest, CBCT positioning standardization as well as the number of examiners are the common variations observed from related studies. For example, the incisive foramen opening, which describes the bottom portion of the NPC, was attained via a flat line that matches the nasopalatine foramen, as stated in the study conducted by Mardinger and others.[13] On the other hand, Bornstein and colleagues[9] measured the anatomic incisive foramen opening. Nonetheless, deviating results from various literature could possibly be due to varying age groups as well as the presence of edentulous subjects.[9],[11],[13] To avoid such variations, patients involved in this research were completely dentate in the anterior maxillary region.[32] Potential bias correlated to alveolar bone resorption was eliminated as all subjects had their upper central incisors.[13]

Population variation also served as an indispensable consideration in the varying results. As such, understanding morphologic NPC patterns in various populations is deemed important due to clinical implication during implant placement procedures as well as upper central incisor root movement. This study was focused on Saudi patients, who have different morphologic patterns as compared to subjects from other countries such as Malaysia[29] and Japan.[12]

The age groups in the current study were classified into four groups (below and equal to 20, 21-40, 41-60 and above 60 years), compared to the three age groups used by Thakur et al.[14] (20-34, 35-49 and equal to or above 50 years old). The objective was to include younger and older age groups to represent the aging effects on bone remodeling and anatomical structure dimensional changes. However, the working groups of the collected samples is limited due to the stringent inclusion criteria such as no record of orthodontic treatment, no lost or supernumerary maxillary incisors and no prosthodontic maxillary incisor treatment. These are usually the main reasons for taking CBCTs in the anterior maxilla; therefore, the number was limited as they were excluded from our study. Thus, the generalizability of the results is limited, and further work is needed to have a larger sample size in each age group.


Based from the findings, age does not play a vital role in the IC morphology as well as its dimensions. However, statistical analysis revealed the influence of gender on IC length. As such, gender may not be a key factor when IC morphology is considered, although most studies suggested a longer IC length for male subjects as compared to the female counterparts.

The canal shape as well as its anteroposterior proportions is deemed as a crucial factor prior to implant placement in the maxillary incisor area. Failures attributed to treatment might bring upon clinical circumstances possibly modified via implant removal and succeeding tissue augmentation procedures. Osseointegration failure and sensory dysfunction can potentially exist during implant contact with neural tissue. To counteract these possible difficulties, NPC morphology and dimensions must be appropriately assessed prior to dental implant placement or any dental operations in the locality of this anatomic assembly.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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