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INTRODUCTION: The anatomical variations of the mandibular canal have been described according to the number of additional branches it presents, bifid and trifid. Within the bifids we can also find subtypes of variations such as the retromolar mandibular canal. These anatomical variations can have important clinical implications for the work of dental professionals. METHODS: A systematic search of the literature was carried out in different databases that met the following criteria: articles published between 2000 and 2020, and articles that established a clinical correlation with variations in the mandibular canal. RESULTS: After applying inclusion and exclusion criteria, 32 articles were obtained, in which the variations of the mandibular canal were identified, their prevalence and incidence, which was very varied between the different articles, it was also found that the CBCT was the main technique to identify the anatomical variations of the mandibular canal. Lastly, the anatomical variations of the mandibular canal have a direct clinical correlation with pre-surgical, intra-surgical and postsurgical complications in pathologies that require surgical intervention. CONCLUSIONS: The anatomical variations of the mandibular canal have a high incidence, so knowing them is of vital importance both for clinicians and anatomy professors who provide morphological training. We believe that research should focus on describing and diagnosing the causes of these anatomical variations. That said, there is also a continuous challenge for all health professionals to learn about the different anatomical variations that the human body presents and how these can affect clinical practice.

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BACKGROUND: Morphological variations of the mandibular canal (MC) have been described in literature, so the clinician must be able to recognise them and adapt their treatment accordingly. The aim of this study was to determine the prevalence of morphological variations of the MC using digital panoramic radiographs (DPR) of Chilean patients. MATERIALS AND METHODS: A retrospective study in which 1400 DPR were analysed to identify cases of bifid, trifid and retromolar MC. The radiographs were analysed independently by two examiners who had previously been trained by a specialist in oral and maxillofacial radiology. Inclusion and exclusion criteria were applied to reach a final sample. RESULTS: Nine hundred and twenty-five radiographs were included (599 female, 326 male; mean age 36.1 ± 15.54 years). The prevalence of bifid MC was 11% (n = 102), with no significant differences by sex (p = 0.069). Proportion of bifid MC was higher among younger patients (p = 0.038). Prevalence of morphologi- cal variations of type 1 bifid MC was 7.4% (n = 69), type 2 was 2.3% (n = 23), type 3 was 0% (n = 0) and type 4 was 1.1% (n = 10). Prevalence of retromolar canal was 0.9% (n = 8), with no significant differences by sex (p = 0.893) or age (p = 0.371); of these, 2 (0.2%) cases were forward type and 6 (0.6%) cases were retromolar type. No cases of trifid MC were found. CONCLUSIONS: Digital panoramic radiographs are useful for detecting morphological variations of the MC; we were able to identify three types of bifid MC as well as retromolar canals. Proper identification of these variations by an easily accessible examination is important for avoiding possible complications in clinical-surgical practice.

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SUMMARY: The retromolar canal (RMC) is a collateral branch of the mandibular canal. This branch seems to be involved in the innervation of the third molar, retromolar trigon and part of the buccal mucosa and fibres of the buccinator and temporalis muscles. The prevalence of RMC in osseous and CBCT studies was reported between 1.7 %-72 %. This study aims to investigate the prevalence of RMCs in a Turkish population using cone beam CT. 340 CBCT images of hemimandibles of 170 patients, with a mean age of 37 (range, 16-80), that clearly identified the course of the mandibular canal in the posterior mandible were selected retrospectively from the archived records of our Oral and Maxillofacial Radiology Department. The sagittal, coronal, axial and pseudopanoramic images were used for assessing the RMCs. This variant was found in 19 out of 170 patients (11 %). Of the 340 CBCT examinations in 170 patients, 20 showed the presence of a RMC (5 %). It was present unilaterally in 18 patients (95 %) and bilaterally in one patient (5 %). There was no difference in the presence of RMCs with regard to sex and sides of the mandible (p>0.05). Clinicans should be aware of RMC and this anatomical variance should be taken into consideration while planning surgery around this region. When there is any suspicion of the RMC presence CBCT is the best imaging modality to visualize the three-dimensional structure of this variant.

RESUMEN: El canal retromolar (CRM) es una rama colateral del canal mandibular. Esta rama parece estar comprometida en la inervación del tercer molar, el trígono retromolar parte de la mucosa oral y de las fibras de los músculos buccinador y temporal. La prevalencia de CRM se ha reportado entre el 1,7 % -72 % en estudios óseos y de tomografía computarizada. Este estudio tuvo como objetivo investigar la prevalencia de CRM en una población turca utilizando tomografía de haz de cono. Se seleccionaron 340 imágenes TCHC de los registros de nuestro Departamento de Radiología Oral y Maxilofacial, de mandíbulas de 170 pacientes con una edad media de 37 años (rango, 16-80), las que identificaban el trayecto del conducto mandibular en la parte posterior de la mandíbula. Se utilizaron las imágenes sagital, coronal, axial y pseudo panorámica para evaluar los CRM. La variante se encontró en 19 de los 170 pacientes (11 %). De los 340 exámenes realizados con TCHC en 170 pacientes, en 20 de éstos se observó la presencia de un CRM (5 %); se observó unilateralmente en 18 pacientes (95 %) y bilateralmente en un paciente (5 %). No hubo diferencias en la presencia de CRM con respecto al sexo y los lados de la mandíbula (p> 0,05). Los clínicos deben considerar el CRM y tener en cuenta esta variación anatómica al planificar la cirugía en esta región. Cuando existe alguna sospecha de la presencia CRM, la TCHC es la mejor modalidad para visualizar la estructura tridimensional de esta variante.

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PURPOSE: The aim of this study was to analyze the presence of the RMF in mandibles, considering gender and ethnic group. The RMC was also analyzed using periapical radiography. METHODS: Eighty-six mandibles from adult individuals of both sexes, of white and black skin colours were analyzed. The presence of RMF (bilateral or unilateral) was observed, with the side and the number of foramina in each hemimandible. Five mandibles were selected for RMC evaluation by periapical radiography. RESULTS: We observed at least 1 RMF in 16 mandibles out of a total of 86 (18.60%) and in 21 out of 172 sides (12.20%). The percentages were 27% in black individuals, 15.6% in white individuals, 23.8% in females and 13.8% in males. CONCLUSIONS: The RMF is a reasonably frequent anatomical variation and shows no differences between sexes or ethnic group, can be unilateral or bilateral and presents no side preference. The RMC presents different types of course and can even establish contact with the alveolar cortical, which might further complicate surgical and anaesthetic procedures in this region.