Imaging Sci Dent.  2016 Jun;46(2):69-75. 10.5624/isd.2016.46.2.69.

Assessment of the anterior loop of the mandibular canal: A study using cone-beam computed tomography

• do Nascimento EHL
• dos Anjos Pontual ML
• dos Anjos Pontual A
• da Cruz Perez DE
• Figueiroa
• Frazão MA
• Ramos-Perez FMdM

• KMID: 2308869
• DOI: http://doi.org/10.5624/isd.2016.46.2.69

Abstract

PURPOSE
Sufficient area in the interforaminal region is required for dental implant placement, and the anterior loop of the mandibular canal is located within the limits of this area. The aim of this study was to evaluate the prevalence and extent of the anterior loop in a Brazilian sample population using cone-beam computed tomography (CBCT).
MATERIALS AND METHODS
CBCT images from 250 patients (500 hemimandibles) obtained for various clinical indications were randomly selected and evaluated to determine the presence and length of the anterior loop. The length of the anterior loop was then compared based on gender, age, and the side of the mandible. The data were analyzed using the Pearson chi-square test and linear regression analysis.
RESULTS
An anterior loop was identified in 41.6% of the cases, and its length ranged from 0.25 mm to 4.00 mm (mean, 1.1±0.8 mm). The loop had a greater mean length and was significantly more prevalent in males (p=0.014). No significant differences were found between the right and left sides regarding length (p=0.696) or prevalence (p=0.650).
CONCLUSION
In this study, a high prevalence of the anterior loop of the mandibular canal was found, and although its length varied greatly, in most cases it was less than 1 mm long. Although this is a prevalent anatomical variation, safety limits for the placement of implants in this region cannot be established before an accurate evaluation using imaging techniques in order to identify and preserve the neurovascular bundles.

Keyword

Anatomic Variation; Cone-Beam Computed Tomography; Mandible

MeSH Terms

Anatomic Variation
Cone-Beam Computed Tomography*
Dental Implants
Humans
Linear Models
Male
Mandible
Prevalence
Dental Implants

Figure

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  Fig. 1 Assessment of the anterior loop. A. Axial reconstruction rotated towards the side being examined, with the mandibular canal positioned parallel to the sagittal plane (vertical line). B and C. The coronal reconstructions obtained immediately after the most mesial point of the mental foramen show a single (arrow) and double (arrows) hypodense image, respectively.

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  Fig. 2 The course of the mandibular canal, with the absence or presence of an anterior loop. A. The incisive canal and its corresponding image in the coronal reconstruction, with a diameter that must be less than 3 mm. B. The anterior loop and its corresponding image in the coronal reconstruction, which, depending on the place it is obtained, can be represented by a round hypodense area with a diameter of at least 3 mm or by two round hypodense areas.

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  Fig. 3 In coronal reconstructions, the anterior loop can be seen as two round hypodense areas in images 205-208 and as a single round hypodense area (with a diameter of at least 3 mm) in images 209-219. Measurement: 15×0.25=3.75 mm.

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  Fig. 4 The number of cases of anterior loop of the mandibular canal and their respective lengths.

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