Evaluation of 3D MRI for early detection of bone edema associated with apical periodontitis

Abstract

Objectives: To detect and evaluate early signs of apical periodontitis using MRI based on a 3D short-tau-inversion-recovery (STIR) sequence compared to conventional panoramic radiography (OPT) and periapical radiographs in patients with apical periodontitis.

Materials and methods: Patients with clinical evidence of periodontal disease were enrolled prospectively and received OPT as well as MRI of the viscerocranium including a 3D-STIR sequence. The MRI sequences were assessed for the occurrence and extent of bone changes associated with apical periodontitis including bone edema, periradicular cysts, and dental granulomas. OPTs and intraoral periapical radiographs, if available, were assessed for corresponding periapical radiolucencies using the periapical index (PAI).

Results: In total, 232 teeth of 37 patients (mean age 62±13.9 years, 18 women) were assessed. In 69 cases reactive bone edema was detected on MRI with corresponding radiolucency according to OPT. In 105 cases edema was detected without corresponding radiolucency on OPT. The overall extent of edema measured on MRI was significantly larger compared to the radiolucency on OPT (mean: STIR 2.4±1.4 mm, dental radiograph 1.3±1.2 mm, OPT 0.8±1.1 mm, P=0.01). The overall PAI score was significantly higher on MRI compared to OPT (mean PAI: STIR 1.9±0.7, dental radiograph 1.3±0.5, OPT 1.2±0.7, P=0.02).

Conclusion: Early detection and assessment of bone changes of apical periodontitis using MRI was feasible while the extent of bone edema measured on MRI exceeded the radiolucencies measured on OPT.

Clinical relevance: In clinical routine, dental MRI might be useful for early detection and assessment of apical periodontitis before irreversible bone loss is detected on conventional panoramic and intraoral periapical radiographs.

Keywords: Magnetic resonance imaging; Periapical osteolysis; Periodontal disease; Root canal.

Fig. 1

64-year-old patient with known periodontitis. a OPT and b dental radiograph of the tooth 46 after root canal treatment showing no distinct radiolucency. c Sagittal and d coronal reconstruction of a 3D STIR sequence showing a bright edema periapical around the root of the treated tooth. The alveolar bone edema on MRI (white arrows) indicates an inflammatory process but might be also associated with physiological changes. Therefore, findings have to be evaluated together with the results from patient anamnesis and clinical examination

Fig. 2

53-year-old patient with symptomatic periodontitis of the tooth 41. A distinctive periapical radiolucency (white arrows) can be seen on OPT (a) and dental radiograph (b). The coronal (c) and axial (d) reconstructions of a 3D STIR sequence show a larger bone marrow edema around the periapical lesion, indicating a larger inflammatory reaction (white arrows)

Fig. 3

a OPT of a 66-year-old patient with a carious lesion and periodontal disease of the tooth 36. Note the small periapical lesion on the conventional OPT (white arrow). On the sagittal reconstruction of the 3D STIR sequence (b), an extensive alveolar bone marrow edema (arrows) is detected which might indicate a markedly larger extent of the inflammation. Compared to MRI, the extent of inflammatory reaction may be underestimated by conventional OPT

Fig. 4

a OPT of a 67-year-old patient with root canal treatment of the tooth 21. Note that the roots of the teeth 12 to 21 are not assessable due to superimposition of the nasal cavity and sinuses. On the coronal (b) and axial (c) reconstructions of the 3D STIR sequence, a distinct periapical cyst/abscess (white arrows) can be detected next to the root of the tooth 21, which would have been missed on conventional radiography

Fig. 5

a OPT of a non-symptomatic 58-year-old patient. There are no periapical radiolucencies detected on conventional OPT. In contrast, the sagittal reconstruction of the 3D STIR sequence (b) shows a bright periapical bone marrow edema around the root of the tooth 37, indicating the formation of an inflammatory complex that has contact to the adjacent roots (white arrows). The missing radiolucency in the OPT may indicate that it is an early-stage inflammation without osteolysis of the alveolar bone