Abstract 
Background: The Mandibular Incisive Canal (MIC) is the mesial extension of the inferior alveolar nerve, frequently encountered during surgical procedures such as implant placement and bone graft harvesting. Thorough radiographic evaluation, particularly using three-dimensional imaging modalities like Cone-Beam Computed Tomography (CBCT), is crucial to prevent nerve injury and related complications. This review summarizes studies that investigated MIC detection using CBCT.
Methods: Following the PRISMA guidelines, an electronic search was performed in PubMed/MEDLINE and Scopus, identifying 45 studies, of which 35 met the inclusion criteria. An electronic search was conducted in August 2023 using PubMed/MEDLINE and Scopus with MeSH terms and keywords: “mandibular incisive canal,” “incisive canal,” “computed tomography, cone beam,” “CBCT,” “inferior alveolar nerve,” and “mental foramen.” Relevant studies published in English up to August 28, 2023, were included.
Results: MIC was detected in 87.11% of the cases examined by CBCT. The canal was more prevalent in females (F:M =1.12:1), with a mean patient age of 45.11 years (range 10-88). The average MIC length and width were 11.30 mm and 1.72 mm, respectively. The mean distances from the MIC to the buccal cortex, lingual cortex, inferior mandibular border, and alveolar crest were 3.71, 4.98, 9.37, and 15.76 mm, respectively. The longest and widest MICs were observed in the Chinese population, whereas the smallest dimensions were found in the Brazilian population. MIC prevalence was highest among Malays (100%) and lowest among Indians (86.22%).
Conclusion: CBCT is a valuable tool for detecting the MIC. Careful assessment of the MIC and interforaminal region is recommended to prevent nerve injury and associated complications such as sensory disturbances and hemorrhage.
Keywords: Brazil, China, Imaging, Mandibular nerve, Mental foramen, Malaysia, Spiral Cone-Beam Computed Tomography

Introduction 
The Mandibular Incisive Canal (MIC) is the mesial extension of the Inferior Alveolar Canal (IAC), housing the incisive nerve and blood vessels responsible for innervating the lower anterior teeth. The MIC is typically less corticated and smaller in diameter compared to the IAC (1-3). Some researchers propose that the incisive nerve passes through intramedullary spaces rather than a defined bony canal, making it difficult to detect using conventional imaging (4). In certain cases, the MIC is not radiographically evident due to its plexiform nature (5).
Olivier first described the anterior course of the inferior alveolar nerve within the IAC until its division at the mental foramen, where the mental nerve exits and the incisive nerve continues mesially within the MIC, parallel to the anterior teeth roots (6,7).
The interforaminal area is commonly used for procedures like implant placement and bone graft harvesting (8,9). Although traditionally considered a safe zone devoid of major anatomical structures, complications such as hemorrhage and neurosensory disturbances have been reported (10,11). Implant placement in this region may risk MIC perforation, leading to epineurium edema, sensory disturbances, paresthesia, and potential osseointegration failure (12,13).
To avoid such complications, careful evaluation of the MIC and anterior loop is essential (14,15). The anterior loop describes the mandibular canal’s curvature before it opens at the mental foramen (16). While conventional radiography is widely used, its limitations in detecting the MIC and anterior loop are well-known. Cross-sectional imaging, particularly CBCT, allows precise identification of these structures (17,18). Although ultrasound may provide information on the mental foramen, it lacks the diagnostic accuracy of CBCT (19,20).
This review investigates the MIC’s anatomical characteristics and its clinical significance, emphasizing variations across populations to aid in preventing surgical complications.

Materials and Methods 
An electronic search was conducted in August 2023 using PubMed/MEDLINE and Scopus with MeSH terms and keywords: “mandibular incisive canal,” “incisive canal,” “computed tomography, cone beam,” “CBCT,” “inferior alveolar nerve,” and “mental foramen.” Relevant studies published in English up to August 28, 2023, were included. Manual cross-referencing supplemented the search. After screening 361 studies, 249 were shortlisted based on titles and abstracts. Studies focusing solely on panoramic imaging or cadaveric assessments were excluded (1,7,21). After full-text review, 35 studies met the inclusion criteria (Figure 1).

Data collected included
- Study authors and year
- Sample size
- Patient demographics (sex and age)
- MIC prevalence
- CBCT device, software, and slice thickness used
- Patient ethnicity
- MIC mean length and width
- Distances from MIC to anatomical landmarks

Statistical analysis used means for continuous variables and percentages for categorical data. Quality assessment was independently conducted by two reviewers, with a third resolving disagreements.

Results
Study selection
Thirty-five studies assessing the MIC via CBCT (published between 2009 and 2023) were included. Study characteristics are detailed in tables 1 and 2.

Demographics
MIC was observed in both sexes, with a higher prevalence among females (F:M=1.12:1). The mean age was 45.11 years (range 10–88) and sample sizes ranged from 50 to 1008.

CBCT examination details
Twelve CBCT units (e.g., i-CAT, NewTom) and 14 software platforms were employed, with slice thicknesses varying from 0.01 mm to 1 mm (mean 0.5 mm). Imaging parameters like kVp (60-120) and mA (1-36) varied across studies.

Ethnic variations
MIC prevalence differed across ethnicities, ranging from 83.1% (Americans) to 100% (Malays). Chinese subjects had the longest (12.96 mm) and widest (2.5 mm) canals, while Brazilian populations had the smallest measurements.

Table 1. Reported articles of MIC presence and its characteristics in various ethnicities in the literature up until August 2023

Table 1. Reported articles of MIC presence and its characteristics in various ethnicities in the literature up until August 2023

*Distance A: Distance of the initial portion of the Mandibular Incisive Canal (MIC) to the buccal table.

 Distance B: Distance of the initial portion of the Mandibular Incisive Canal (MIC) to the lingual table.

 Distance C: Distance of the initial portion of the Mandibular Incisive Canal (MIC) to the inferior mandibular border.

 Distance D: Distance of the initial portion of the Mandibular Incisive Canal (MIC) to the alveolar canal.

 Distance E: Distance of the final portion of the Mandibular Incisive Canal (MIC) to the buccal table.

 Distance F: Distance of the final portion of the Mandibular Incisive Canal (MIC) to the lingual table.

 Distance G: Distance of the final portion of the Mandibular Incisive Canal (MIC) to the inferior mandibular border.

 Distance H: Distance of the final portion of the Mandibular Incisive Canal (MIC) to the alveolar canal.

 Distance I: Distance of the Mandibular Incisive Canal (MIC) to the buccal table.

 Distance J: Distance of the Mandibular Incisive Canal (MIC) to the lingual table.

 Distance K: Distance of the Mandibular Incisive Canal (MIC) to the inferior mandibular border.

 Distance L: Distance of the Mandibular Incisive Canal (MIC) to the alveolar canal

 Table 2. Demographic characteristics and variables of the articles

Mandibular Incisive Canal (MIC).

Table 3. Ethnic characteristics and variables of the studies

Mandibular Incisive Canal (MIC).

MIC prevalence
The average MIC prevalence was 87.11% (range 24.4-100%). CBCT was consistently recommended for preoperative assessment. Buccal canal positioning was most common, with a single study reporting a lingual position.

Anatomical variations
The average MIC length was 11.30 mm and the diameter 1.72 mm. Mean distances from the canal to anatomical landmarks were:
- Buccal cortex: 3.71 mm
- Lingual cortex: 4.98 mm
- Inferior mandibular border: 9.37 mm
- Alveolar crest: 15.76 mm
Measurements varied between the initial and terminal portions of the MIC.

Discussion
The MIC is a critical anatomical structure extending from the IAC, housing neurovascular elements supplying the anterior mandible. First documented in 1928 (6), its presence was later corroborated by anatomical and radiographic studies (1,43). CBCT has significantly improved MIC visualization (8). Anatomical assessments on cadavers have detected MIC in up to 90% of the cases (5,7).
Typically, the MIC courses inferiorly and lingually from the mental foramen, become indistinct near the central incisors as it merges into a neurovascular plexus (29,40). This plexus facilitates midline cross-innervation. The incisive nerve is now considered a prominent structure rather than a mere anatomical variation (22).
Detection rates vary due to ethnic differences, imaging methods, and examiner expertise (32). Prevalence ranged from 24.4 to 100% (19), with Malays showing the highest and Indians the lowest detection rates (2,4,9,25,31). Visibility is influenced by factors like canal cortication, age-related bone changes, and skeletal development (40,44).
While some studies reported no sex-based difference in MIC prevalence (14,15,22,26,29,39), others noted a higher prevalence in females or males, particularly among Chinese cohorts (36). Laterality also varied, with some studies showing right-side dominance (29,32), others left-side (39,41), and some reporting bilateral symmetry (3,5,14). Bilateral presentation was generally more common (26,31,38).
Most studies identified a buccal canal position, although a Brazilian study noted lingual placement (27). Implant placement should account for MIC location to prevent complications (3,33). Ethnic, age, and sex differences underline the need for preoperative CBCT (40).
Accurate measurements of MIC dimensions and positions are vital for safe surgical planning. Direct trauma may cause sensory disturbances; indirect trauma (e.g., hematoma) may exert pressure on the nerve (1). Implants near the MIC can cause neurosensory damage, edema, and osseointegration failure. Arterial injury within the MIC can result in severe bleeding during surgery (12).
A MIC diameter exceeding 2 mm may impair implant stability and increase complication risks (14,23). The average MIC diameter in studies was 1.72 mm, with larger diameters noted in Chinese and Indian populations.
Panoramic radiography underestimates MIC detection due to inherent limitations like distortion (46). CBCT, with superior cross-sectional imaging, provides reliable preoperative assessment (33). High-resolution MRI has been proposed for detailed analysis but remains impractical due to cost and availability (33). CBCT remains the recommended tool for identifying the MIC.

Conclusion
Given its high prevalence, clinicians should recognize the MIC’s anatomical significance to prevent nerve injury, sensory disturbances, and intraoperative bleeding. With an 87.11% detection rate, CBCT is invaluable for mapping the MIC, anterior loop, and mental foramen. The variability among populations underscores the necessity of individualized CBCT assessment before interforaminal surgical interventions. Further research is essential to better understand anatomical variations and optimize patient outcomes.

Funding
This study received no specific financial support. 

Conflict of Interest
There was no conflict of interest in this manuscript.