The diagnostic challenge of 2D projection: a case of anatomical mimicry

When planning the avulsion of mandibular third molars, managing neurological risk is at the heart of the concerns for the implantologist and the oral surgeon. This case report documents the management of a 28-year-old patient referred to the Geneva University Hospitals for recurrent pericoronitis. The initial panoramic radiographic (PAN) examination revealed a subtle radio-opaque image, superimposed on the apices of tooth 38 and the path of the inferior alveolar canal (IAC), suggesting an imminent and complex nerve conflict.

The precise objective of this clinical presentation is to demonstrate the intrinsic limitations of two-dimensional imaging in evaluating the anatomical relationships of the posterior mandible. The authors illustrate how superposition phenomena can distort the interpretation of the tooth-nerve relationship, directly impacting surgical planning.

L'examen approfondi repose sur la confrontation entre la suspicion de conflit radiculaire issue de la 2D et la réalité anatomique révélée par le Cone-Beam Computed Tomography (CBCT). L'analyse tridimensionnelle a ici permis de rejeter l'hypothèse d'un contact direct entre la troisième molaire et le nerf alvéolaire inférieur, identifiant à la place une ostéosclérose idiopathique bien définie, adjacente au canal mais distincte des racines dentaires. Ce cas souligne que le CBCT demeure l'examen de choix pour transformer une incertitude diagnostique en un plan de traitement sécurisé.

Diagnostic methodology and imaging protocol

This case report documents the diagnostic approach applied to a 28-year-old patient, managed within the Oral Surgery and Implantology Unit of the Geneva University Hospitals. The clinical protocol was initiated following recurrent episodes of pericoronitis motivating the avulsion of the mandibular third molars.

The investigation methodology was based on a sequential analysis of medical imaging:

• Two-dimensional imaging: A panoramic radiograph (PAN) was initially performed to evaluate the position of the third molars. The analysis focused on a subtle radio-opaque image projected over the path of the inferior alveolar canal and the apices of tooth 38, suggesting a neurovascular conflict.
• Three-dimensional imaging: Due to the ambiguity of anatomical relationships on 2D images, a cone beam computed tomography (CBCT) scan was performed to obtain increased spatial resolution.

The comparative radiological analysis aimed to discriminate the nature of the lesion and its actual proximity relationships. The CBCT allowed for a precise three-dimensional evaluation of the structures, facilitating the differentiation between the dental roots, the inferior alveolar nerve (IAN) canal, and the radiopaque mass. This approach confirmed the absence of direct contact between the molar and the nerve, while identifying an adjacent but distinct idiopathic osteosclerosis.

Results of the radiographic investigation

The diagnostic evaluation of this 28-year-old patient, initially referred for the extraction of the mandibular third molars, revealed a major divergence between two-dimensional and three-dimensional imaging regarding tooth 38.

Qualitative and differential observations

Detailed analysis using Cone-Beam Computed Tomography (CBCT) has resolved the ambiguity caused by the superposition of structures on the panoramic radiograph. The results highlight:

• Root independence: Contrary to the 2D warning signs, the osteosclerosis lesion is not linked to the root system of the third molar.
• Anatomical localization: The radiopaque mass is located in the immediate vicinity of the inferior alveolar canal, mimicking a nerve conflict which, in reality, does not exist with the tooth itself.
• Diagnostic precision: CBCT rectified the treatment plan by confirming that the pathology was idiopathic osteosclerosis, an anatomical variant or a benign lesion not requiring the same surgical precautions as a true dento-neural conflict.

This case study demonstrates that panoramic radiography can mislead the practitioner in the posterior region of the mandible due to projection phenomena, making 3D imaging essential whenever doubt persists regarding the path of the inferior alveolar nerve.

Clinical case analysis and the contribution of 3D imaging

This clinical case involving a 28-year-old patient perfectly illustrates the limitations of panoramic radiography (2D) in assessing complex anatomical relationships. Initially, the image suggested a direct conflict between the apices of tooth 38 and the inferior alveolar nerve (IAN) canal. However, the transition to Cone-Beam (CBCT) radically modified the diagnosis: no contact existed between the tooth and the nerve. The radiopaque lesion, which appeared superimposed on the roots, proved to be a distinct idiopathic osteosclerosis, located near the mandibular canal but unrelated to the third molar.

Implications for differential diagnosis

The study highlights that idiopathic osteosclerosis can simulate root impingement when projected onto the path of the IAN. The authors point out that this entity must be differentiated from other lesions such as condensing osteitis, cementoblastoma, or fibro-osseous dysplasias. Although this case report is limited by its unique nature (n=1), it highlights a risk of overtreatment or poor assessment of neurological risk if the practitioner relies exclusively on two-dimensional imaging when faced with equivocal signs.

Study summary

Ce rapport de cas clinique portant sur un patient de 28 ans démontre qu’une image radiopaque superposée au trajet du nerf alvéolaire inférieur (NAI) sur une panoramique 2D peut simuler un conflit radiculaire inexistant. L'examen CBCT a infirmé tout contact direct entre la dent 38 et le nerf, identifiant précisément une ostéosclérose idiopathique adjacente mais distincte des racines dentaires.

In concrete terms, for the practitioner:

• Beyond 2D: In the event of equivocal radiological signs of proximity between the roots of the third molar and the mandibular canal, switching to CBCT is imperative to avoid overestimating the risk of nerve injury.
• Refine your differential diagnosis: Consider idiopathic osteosclerosis when faced with an isolated radiopaque lesion, even if it appears projected over the nerve pathway or the dental apex.
• Secure the surgical procedure: Use 3D precision to plan the extraction without unnecessarily compromising the IAN or to reassure the patient regarding the absence of actual anatomical conflict.

Technical lexicon of the study

Idiopathic osteosclerosis: Focal, well-defined, and asymptomatic radiopaque bone lesion of unknown etiology. It is distinguished from inflammatory or neoplastic lesions by the absence of a radiolucent halo and normal adjacent medullary bone structure.

CBCT (Cone-Beam Computed Tomography): Cone-beam three-dimensional imaging technique offering high spatial resolution. It eliminates the superposition phenomena inherent in 2D radiography to accurately evaluate real anatomical relationships.

Inferior alveolar nerve (IAN): Branch of the mandibular nerve running through the inferior alveolar canal. Its proximity to the apices of the mandibular third molars represents a major risk of neurosensory deficit during extraction procedures.

Pericoronitis: Inflammation of the soft tissues surrounding the crown of a partially impacted or erupting tooth. In this clinical case, recurrent episodes of pericoronitis motivated the decision to extract teeth 38 and 48.

Radiographic superposition: Optical phenomenon in two-dimensional imaging (PAN) where two structures located on different antero-posterior planes appear merged, falsely simulating anatomical contact or conflict.

Nerve-tooth conflict: Relationship of immediate proximity or interference between the dental roots and the mandibular canal, suggested by radiographic examination and requiring confirmation by sectional imaging to secure the surgical procedure.

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