Abstract
Objective: This study aims to establish the anatomical relationship between the mandibular canal and the third molars, based on analysis by Cone Beam Computed Tomography. Methodology: Computed Tomography analysis of 67 third molars was performed using Blue Sky Plan 4 virtual planning software. The anatomical dispositions of the third molars and mandibular canal were evaluated, as well as the factors that favor the contact between these structures. Result: There was a prevalence of 76.1% for biradicular third molars, 52.2% for class 1 and 71.6% class A. Vertical and mesioangulated teeth had a higher prevalence, with 38.8% and 35.8% respectively. Sicher and Tandler's classification presented 41.8% of the canals as type I, while in the buccal-lingual positioning, 89.5% of the canals were located through the buccal. 44.8% of the teeth had contact with the canal and the factors with statistical significance were: female gender (p = 0.019), number of roots (p = 0.019), class 3 (p = 0.004) and C (p = 0.012) teeth and lingual positioning of the mandibular canal (p = 0.016). About the anatomical delimitations, the mean diameter of the canal was 3.14 mm and the distances related to the dental roots, lingual, buccal and inferior cortical bony were 2.77, 3.53, 4.56 and 8.32 milimeters, respectively. Conclusion: Therefore, the assessment of third molars by computed tomography is essential during preoperative planning, as it identifies anatomical relationships that favor contact between the tooth and the mandibular canal and helps to reduce the incidence of sensorineural disorders.
Highlights
The extraction of mandibular third molars is the most commonly performed oral and maxillofacial surgery procedure in clinical practice
Numerous studies point to the risk of injuries to the lower alveolar nerve in the postoperative period, due to the proximity between the dental roots and the mandibular canal (Cheung et al, 2013; Valmaseda-Castellon et al, 2001; Monaco et al, 2004), an adequate preoperative evaluation is necessary to identify the anatomical relationships between the mandibular third molar and the lower alveolar nerve and the potential risk of injuries
Panoramic radiography is an image exam most commonly requested for preoperative radiographic evaluation of the third molars, it provides only two-dimensional images and is unable to identify the adequate buccal-lingual relationship between the mandibular canal and the third molar (Monaco et al, 2004; Sedatghafar et al, 2005; Maegawa et al, 2003)
Summary
The extraction of mandibular third molars is the most commonly performed oral and maxillofacial surgery procedure in clinical practice. Panoramic radiography is the most requested image exam for preoperative evaluation in extractions of third molars, due to its low cost and greater accessibility It provides only a two-dimensional image, with wide overlapping of structures and difficulties in the precise determination of the buccal-lingual position of the third molars (Deshpand P et al, 2013; Monaco et al, 2004; Sedaghatfar et al, 2005). Cone Beam Computed Tomography (CBCT) has been widely used due to its high spatial resolution, three-dimensional capacity with the possibility of reconstruction in axial, coronal and sagittal sections It provides the precise anatomical location of the mandibular canal in the buccal-lingual and anteroposterior directions (Deshpand et al, 2013; Kim and Lee, 2014). The aim of this work is to establish the three-dimensional anatomical relationship between the mandibular canal and the third mandibular molars, based on the analysis of Cone Beam Computed Tomography, in order to guide the elaboration of an adequate surgical planning, identifying anatomical relationships that favor contact between the roots and the lower alveolar nerve and may increase the risk of nerve damage during surgery
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