Depiction of marrow edema and soft tissue inflammatory change

A major contribution of dental MRI was its ability to depict tissue compartments that radiographic methods cannot show directly. Geibel et al. compared non-contrast T₁-weighted and T₂-weighted MR images (refer to Supplementary Material for basic MRI principles and dentistry-related MR sequences). They reported heterogeneous lesion contrast on T₂-weighted images and described a well-circumscribed hyperintense signal near the apical foramen in four patients (Geibel et al., 2015). In their illustrated cases, fluid-rich cystic lesions tended to appear relatively hypointense on T₁-weighted and more hyperintense on T₂-weighted images, often with a fibrotic or low-signal rim. In contrast, granulomatous lesions were more homogeneous across weightings. The 2017 Geibel case series extended this observation by showing that MRI could depict cyst fluid, fibrotic capsule, cholesterol-containing low-signal foci, sinus mucosal involvement, and cortical perforation in a manner that was not possible for CBCT scans (Geibel et al., 2017). Pigg et al. (2014) likewise interpreted increased MRI signal as reflecting high water content and edema, whereas radiographic methods reflected mineral loss after inflammation had already affected bone. This distinction suggests that conventional dental MRI had already opened the possibility of detecting inflammatory change that was biologically relevant but not fully captured by radiographic density loss.

Lesion characterization

The most important pre-ddMRI advance was lesion characterization, particularly in the differentiation between cystic and granulomatous lesions. Lizio et al. (2018) examined 34 surgically enucleated periapical lesions and found strong inter-rater agreement between MRI diagnosis and histopathology. In that study, differentiation between cysts and granulomas by MRI was possible based on signal intensity, signal homogeneity, lesion margins, a low-intensity outline, and contrast distribution pattern. Juerchott et al. (2018) refined this question further in a pilot study with histological confirmation. They identified six MRI features that differentiated cysts from granulomas. These features were lesion margin, peripheral rim texture on contrast-enhanced T₁-weighted images, lesion-center texture on fat-saturated T₂-weighted images, surrounding tissue involvement on both MR sequences, and peripheral rim thickness. Figure 3 illustrates these differentiating MRI features. Cysts had well-defined margins, homogeneous lesion centers, no surrounding tissue involvement, and a thin peripheral rim. Granulomas had ill-defined margins, inhomogeneous lesion centers, surrounding tissue involvement, and a thicker peripheral rim. There was very high reproducibility of the MRI evaluations. The 2017 Geibel case series pointed in the same direction. Scans performed with CBCT showed similar lesion appearance across cases, whereas multi-contrast MRI produced histology-consistent differentiation of cysts and granulomas (Geibel et al., 2017). Taken together, these studies show that dental MRI had already moved beyond simple lesion detection before the emergence of ddMRI.

The ddMRI era: task-specific imaging for endodontic diagnosis

Greiser et al. (2024) introduced ddMRI using the MAGNETOM Free.Max Dental Edition platform. This is a dental-dedicated 0.55 T MRI system developed by Siemens Healthineers (Forchheim, Germany) for dentomaxillofacial imaging (Dentsply Sirona & Siemens Healthineers, 2024). In a subsequent endodontic feasibility study, Johannsen et al. (2026) used the imaging platform with a seven-channel dental-dedicated radiofrequency surface coil (Dental Coil, RAPID Biomedical, Rimpar, Germany).

This platform differs from earlier dental MRI studies because the scanner, coil, field of view, and sequence selection were configured specifically for dental imaging (Greiser et al., 2024). The low-field 0.55 T design is relevant in the oral cavity, where restorations, crowns, posts, implants, and orthodontic hardware may produce susceptibility-related artifacts on higher-field MRI systems (Bohner et al., 2022). The lower intrinsic signal of low-field imaging is partly addressed by the dedicated dental coil, which receives signal close to the teeth, jaws, and adjacent soft tissues (Greiser et al., 2024; Johannsen et al., 2026). 

Image quality in ddMRI depends on the balance among signal-to-noise ratio, contrast-to-noise ratio, spatial resolution, field of view, and acquisition time imaging (Dentsply Sirona & Siemens Healthineers, 2024). The clinical challenge in ddMRI is to balance these competing demands in a way that is useful for dentistry. The ddMRI platform reported by Greiser et al. (2024) addressed this problem by separating protocols according to diagnostic task. Large-field 3D scout imaging and orthodontic protocols were used when broader anatomic coverage was required. Conversely, high-resolution 2D and small-volume 3D acquisitions were reserved for localized assessments. According to the protocol, reconstructed resolution ranged from 1.4×1.4×1.0 mm for scout imaging to 0.2×0.2×2.5 mm voxel size for localized dentoalveolar tasks. 

An MR sequence is a predefined pattern of radiofrequency pulses, gradient applications, and timing parameters that determine how image contrast is generated, and which tissues are emphasized (Han et al., 2025). In its current form, ddMRI relies mainly on PD-weighted imaging, conventional T₁- and T₂-weighted imaging, short tau inversion recovery (STIR), and a volumetric scout sequence (Supplementary Material) (Greiser et al., 2024). Johannsen et al. (2026) applied the MAGNETOM platform with specific MR sequences selected for pulp vitality and apical periodontitis assessment, including proton density-weighted turbo spin-echo (PD-TSE; Supplementary Material) and STIR acquisitions.

Early ddMRI evidence for periapical diagnosis and pulp vitality

The first endodontic feasibility evidence for ddMRI was provided by Johannsen et al. (2026). The study evaluated pulp vitality and apical periodontitis in 18 teeth from nine patients. The sample included vital teeth, necrotic teeth, and teeth after root canal treatment with or without suspected apical periodontitis. The ddMRI protocol used six pulse sequences with a scan time of approximately 18 min per tooth. Observers evaluated root tip visibility, periapical bone, lamina dura, pulp signal, and periapical fluid or edema-like hyperintensity. All relevant anatomic structures were visible in all cases. Figure 4 illustrates how ddMRI can depict both pulp signal and periapical inflammatory signal in the same endodontic case, while periapical radiography and CBCT primarily show the mineralized tissue component of the lesion.

For pulp vitality, ddMRI showed intermodality agreement of kappa 0.77 and diagnostic accuracy of 0.88. For apical periodontitis, intermodality agreement was kappa 0.87, diagnostic accuracy was 0.94, sensitivity was 1.0, and specificity was 0.92. These early findings suggest that ddMRI can evaluate pulpal status and periapical inflammatory change within one non-ionizing examination. These findings should be interpreted with caution because the data remains preliminary. The sample size was small, the design was non-randomized, and the reference standard relied on clinical and radiographic consensus instead of histopathology. Future studies require larger cohorts, standardized diagnostic thresholds, and more refined definitions of pulp vitality and apical periodontitis before ddMRI can be employed for routine endodontic decision-making.

What ddMRI changes compared with dental MRI

Dental-dedicated MRI does not replace the biological discoveries made by dental MRI. Instead, it changes the imaging environment in which those discoveries may be translated. The main change is standardization. Historical studies showed that MRI could detect periapical lesions, visualize pulp signal, and characterize lesion content. However, they did so by using heterogeneous scanners, coils, fields of view, and acquisition protocols. Dental-dedicated MRI offers a more coherent platform in which scanner design, coil geometry, field of view, and pulse sequences are selected together for dental use (Dentsply Sirona & Siemens Healthineers, 2024).

The second change is task alignment. In dental MRI, the dental target often had to fit the limitations of a medical system. In ddMRI, the protocol is built around clinical questions such as pulp vitality, periapical fluid signal, periodontal assessment, extraction follow-up, orthodontic anatomy, or temporomandibular joint evaluation (Greiser et al., 2024). This shift is clinically relevant because periapical diagnosis depends on both mineralized anatomy and soft-tissue inflammatory change.

The third change is translational relevance. Dental-dedicated MRI brings MRI closer to the workflow requirements of dental imaging by narrowing the imaging target and reducing unnecessary acquisition scope. Current evidence is still too early to position ddMRI as a routine replacement for CBCT. However, the Johannsen feasibility data suggest that ddMRI may become a non-ionizing adjunct for selected endodontic questions, particularly when pulp status, early inflammatory change, or repeated imaging is clinically relevant (Johannsen et al., 2026).

Dental-dedicated MRI compared with CBCT for periapical diagnosis

Diagnostic target visualization

Cone beam computed tomography and ddMRI can answer different diagnostic questions in periapical disease. The former is strongest when the diagnostic target is mineralized tissue. Issues of interest include disruption of the cortical plate, cancellous bone loss, root morphology, root filling extent, resorptive defects, and relation to adjacent anatomical structures including proximity to the maxillary sinus (Kruse et al., 2019; Patel et al., 2012; Venskutonis et al., 2014; Chogle et al., 2020; Kalogeropoulos et al., 2022; Tay et al., 2022; Park et al., 2023). Conversely, ddMRI is strongest when the diagnostic target involves pulp status, bone marrow edema, periapical fluid accumulation, soft tissue swelling or edema-like change (Greiser et al., 2024; Johannsen et al., 2026). The difference between the two imaging modalities reflects their contrast mechanisms: CBCT depicts X-ray attenuation, whereas ddMRI depicts proton-based signal behavior. Magnetic resonance imaging forms images by detecting signals from hydrogen protons after they interact with a static magnetic field and a radiofrequency pulse applied perpendicular to the magnetic field (Berger, 2002). Hydrogen is abundant in biological tissues, particularly in water and organic compounds (Remick & Helmann, 2023). Soft tissues such as dental pulp, periodontal ligament, gingiva, bone marrow, nerves, and inflammatory exudates contain abundant mobile hydrogen and can therefore generate measurable MR signals (Han et al., 2025; Vaddi et al., 2025).

Cone beam computed tomography remains the more mature modality for routine osseous mapping. It provides high spatial resolution, multiplanar reconstructions, and clinically established interpretation pathways (Patel et al., 2012; Venskutonis et al., 2014; Chogle et al., 2020; Kalogeropoulos et al., 2022; Tay et al., 2022; Park et al., 2023). In contrast, ddMRI is less established for fine mineralized detail. Nevertheless, ddMRI may add diagnostic information when the clinical question involves the biological activity of the periapical tissues (Johannsen et al., 2026).

Detection of early inflammatory changes

Apical periodontitis begins as an inflammatory disease, but radiographic visibility depends on mineralized tissue change [30]. CBCT improves detection compared with conventional 2D radiography. However, CBCT still depicts the structural consequences of inflammation instead of inflammation per se (Patel et al., 2012; Venskutonis et al., 2014; Kruse et al., 2019). In this context, ddMRI may narrow this diagnostic gap by showing fluid accumulation, edema-like hyperintensity, and altered marrow signal before a lesion becomes clearly expressed as cortical or cancellous destruction (Johannsen et al., 2026).

This distinction can potentially be clinically important when symptoms, sensibility testing, and radiographic findings do not align. In the early ddMRI feasibility study, apical periodontitis was evaluated using periapical fluid accumulation or edema-like hyperintense signal (Johannsen et al., 2026). This approach may be valuable in selected cases in which the clinician suspects active inflammatory change, and CBCT findings are equivocal or difficult to interpret. The present evidence remains early, as intensity thresholds for edema-like signals have not yet been firmly established even for medical MRI (Maraghelli et al., 2021).

Cortical bone versus cancellous bone and marrow assessment

The preferred modality for cortical bone assessment is CBCT. It shows cortical plate perforation, thinning, expansion, fenestration, and the relation of the lesion to the maxillary sinus floor or the mandibular canal with high geometric clarity (Patel et al., 2012; Venskutonis et al., 2014; Chogle et al., 2020; Kalogeropoulos et al., 2022; Tay et al., 2022; Park et al., 2023). These features are critical for differential diagnosis, surgical planning and risk assessment before intervention. In contrast, ddMRI is better suited for cancellous marrow and soft tissue signal (Greiser et al., 2024; Johannsen et al., 2026). This may become useful when the clinical question is whether the marrow around the root apex shows inflammatory or fluid-related change. For periapical diagnosis, the two modalities should therefore be viewed as complementary.

Lesion extent and boundary delineation

The osseous boundary of a periapical lesion can be delineated by CBCT. It is especially useful when the clinician needs to estimate lesion proximity to adjacent roots, the maxillary sinus, the nasal floor, or the mandibular canal. However, the boundary seen on CBCT is a boundary of mineralized tissue loss. It may not fully match the extent of inflammatory change in the bone marrow or adjacent soft tissue.

Dental-dedicated MRI may depict a broader inflammatory field when edema-like or fluid-rich changes extend beyond the radiographically visible defect (Johannsen et al., 2026). This difference should be interpreted carefully. A larger MR signal abnormality does not automatically mean a larger destructive lesion. It may represent marrow reaction, inflammatory fluid, granulation tissue, or post-treatment tissue change. Therefore, ddMRI should not be used as a simple size substitute for CBCT. Its value lies in separating osseous lesion extent from biological tissue response.

Lesion characterization

Cone beam computed tomography can show the shape, border, size, cortical expansion, and relationship of periapical radiolucencies to adjacent structures. However, it has limited ability to distinguish cystic, granulomatous, fibrotic, or fluid-rich tissue composition with confidence (Juerchott et al., 2018; Geibel et al., 2015, 2017; Lizio et al., 2018). To date, lesion characterization with ddMRI remains more of a promise than a validated diagnostic endpoint. Historical dental MRI studies showed that MRI can distinguish cystic and granulomatous patterns when compared with histology. However, the early ddMRI evidence has focused mainly on pulp vitality and apical periodontitis detection (Johannsen et al., 2026). Future ddMRI studies will require histopathological correlation before this imaging modality can be claimed to characterize lesion type reliably in clinical practice.

Artifacts from dental materials

Artifacts affect both imaging modalities, but their appearance differs. Cone beam computed tomography is vulnerable to beam hardening and streak artifacts from dense restorative and endodontic materials (Schulze et al., 2011). These artifacts may obscure root apices, root filling margins, cracks, and adjacent cortical bone. In contrast, ddMRI is vulnerable to susceptibility-related distortion and signal loss from metallic materials, especially ferromagnetic alloys, orthodontic appliances, and some implant-supported restorations (Bohner et al., 2022).

The mechanism behind many of these MRI artifacts is magnetic susceptibility mismatch (Astary et al., 2013; Imai et al., 2013). When materials with different magnetic properties are placed in the main magnetic field, local field homogeneity is disturbed. This alters proton precession (rotation) and disrupts spatial encoding, which may result in signal loss or geometric distortion in the reconstructed image (Öcbe et al., 2025). Stainless steel orthodontic brackets are the best-documented source of clinically relevant artifacts in head and neck MRI (Bohner et al., 2022). Titanium and ceramic materials generally introduce fewer artifacts than stainless steel, with titanium implants producing greater magnetic field distortion than zirconia (Johannsen et al., 2025).

The low-field design of ddMRI may reduce susceptibility-related artifacts compared with higher-field MRI, but it does not eliminate them (Bohner et al., 2022; Greiser et al., 2024). Sequence choice, material composition, object geometry, and distance from the target influence artifact severity (Johannsen et al., 2026). For periapical diagnosis, this means ddMRI may be advantageous when CBCT streaking limits interpretation. Common endodontic materials are MRI-compatible. However, this advantage may be limited when MR signal loss occurs near crowns, posts, implants, or orthodontic components (Bohner et al., 2022).

Radiation exposure, workflow, accessibility, and cost

Radiation exposure is the clearest advantage of ddMRI. Because CBCT involves ionizing radiation (Coşkun Albayrak & Özdemir, 2025), its use should be justified by clinical need and dose optimization principles (American Association of Endodontists & American Academy of Oral and Maxillofacial Radiology, 2016; Wong et al., 2025). Dental-dedicated MRI avoids ionizing radiation, which may be attractive for younger patients, repeated follow-up, or cases in which soft tissue inflammatory information is central to the diagnostic question (Greiser et al., 2024; Johannsen et al., 2026). 

Workflow currently favors CBCT because it is widely available in dental settings, relatively fast, and familiar to clinicians. For ddMRI, scan times, cost, access, contraindications, sequence selection, and interpretation training still limit routine use (Greiser et al., 2024). The Johannsen feasibility study reported a scan time of approximately 18 min per tooth. This scan time is clinically meaningful but still longer than typical CBCT acquisition and reconstruction workflows (Johannsen et al., 2026).

At this stage, ddMRI should not be considered a routine replacement for CBCT. Cone beam computed tomography remains the first-line 3D imaging modality when the diagnostic task is bone-dominant. Dental-dedicated MRI is better positioned as a non-ionizing adjunct for selected cases in which pulpal status, early inflammatory change, marrow edema, soft tissue extension, or repeated imaging is clinically important.

Evidence gaps and future research

The ddMRI evidence base for periapical diagnosis remains early. Current clinical data are limited by small cohorts, feasibility designs, and reference standards based mainly on clinical and radiographic consensus rather than histopathology. Future studies should use standardized acquisition protocols, predefined diagnostic criteria, and blinded observer evaluation across multiple centers. Larger cohorts are required to determine sensitivity, specificity, interobserver agreement, and diagnostic thresholds for pulp vitality, periapical fluid signal, marrow edema, and lesion characterization. Outcome-based studies are also required to determine whether ddMRI changes treatment decisions, reduces unnecessary intervention, or improves follow-up compared with CBCT. Histology-linked studies are crucial for testing whether ddMRI can reliably distinguish cysts, granulomas, scar tissue, and active inflammatory lesions. Future research should also evaluate scan time, cost, patient tolerance, artifacts, and workflow before ddMRI can be recommended for routine endodontic use.