Avaliação do canal incisivo mandibular através de tomografia computadorizada de feixe cônico: revisão sistemática e estudo multicêntrico retrospectivo

Abstract

The mandibular incisive canal (MIC) is an intraosseous pathway of the mandibular canal after the mental nerve emerges from the mental foramen, being responsible for the innervation and vascularization of the canine, lower incisors, and first premolars teeth, as well as the surrounding mucosa. Some complications have been associated with MIC during and after surgical procedures in the anterior mandibular bone region, such as sensorineural disturbances and bleedings. These facts may occur due to the possible anatomical variations of the CIM, which their reforces the need for its identification and visualization in the planning of invasive procedures such as chin bone grafting in this region. Actually, there is no established protocols regarding the placement of dental implants in the anterior mandible bone region in relation to the presence of MIC and eventual anatomic variations. Conventional radiographic exams do not allow visualization of the MIC in several situations; on the other hand, concomitant computed tomography (CBCT) as a three-dimensional examination that allows the manipulation of images in the axial, sagittal and coronal axes is the tomographic modality indicated for the planning of surgical interventions in the interforaminal region of the mandible. In addition, the CBCT has provided that studies on the MIC are performed in different populations, which has shown a high prevalence of this anatomical structure. In this context, the present work has two chapters that aim, respectively: 1) to carry out a systematic review on studies that evaluated the MIC through CBCT; 2) to describe topographic aspects of the CIM using CBCT from four imaging centers. In Chapter 1, a systematic review registered on the PROSPERO platform under number 42017056619 was carried out according to the recommendations of the PRISMA guide. The results of this study showed that geographically there are studies in 4 continents, being a high prevalence of MIC independently of the studied population; in addition, the bilateral occurrence was statistically significant. In Chapter 2, a multicenter retrospective study was performed using CBCT from 4 imaging centers located in Fortaleza, Brazil, two universities and two private clinics. The sample consisted of 847 patients, rendering 1694 hemimandibles, being 320 men and 527 women (age ranging from 18 to 69 years). After applying the eligibility criteria, the included scans were evaluated for gender, age, frequency of visible MIC, laterality and linear measures performed at its beginning and end. A prevalence of 76.3% and no statistical difference between the sexes (p=0.934) was observed between the fourth and sixth decades of life (p <0.001), bilateral occurrence (p 13 <0.001), and mean length of 7.7 ± 3.7mm. Spearman correlation and logistic regression model showed linearity between age and measurements (p <0.05). Linear measurements (mm) varied between the onset and end of the MIC up to the alveolar cortical (16.37 ± 5.9 and 18.6 ± 3.51), buccal (2.6 ± 1.27 and 3.96 ± 1.43) and lingual (5.13 ± 1.7 and 4.61 ± 1.65) cortical, and mandibular border (9.32 ± 1.92 and 8.76 ± 2.07). As conclusions of both studies, we have: (1) The prevalence of MIC was significant among the studies included in a systematic review that, for the most part, presented heterogeneous methodologies. In addition, there was apparently no prevalence as to sex and its occurrence was more significant in adults between the fourth and sixth decades of life; (2) In a multicenter study, the prevalence of CIN was 76.3%. The main findings of this anatomical repair in this study were an occurrence in individuals of both sexes between the fourth and sixth decades of life, mostly bilateral, mean length of 7.7 mm, as well as a course with inferior and lingual direction as it becomes anterior.