Harald Essig

Bacterial biofilm formations on dental implant–bone borders risk the development of periimplantitis (PI). Treatment, ranging from conservative to invasive options, is effective but associated with significant patient burden. In vitro Photodynamic Inactivation (PDI) waveguided by zirconium dioxide ceramic (ZrO₂) dental implants shows promising bactericidal effects and is envisioned to function as an additive treatment reducing patient burden while maintaining therapy outcomes. To facilitate clinical application, this study mathematically quantified the expected waveguiding abilities of ZrO₂ implants in a computed tomography (CT)-based Monte Carlo Simulation of Radiation Transport (MCRT). The latter implemented previously photographically determined optical properties from human and porcine jawbone tissues. ZrO₂ implants displayed effective light propagation beyond the implant–bone border, with power-per-area values above a minimum baseline for effective PDI of 10 mW/cm², thus delivering enough light power to reach bactericidal levels in a standard PDI regimen. Modifying the implant design and light-source placement influenced the topographic distribution of the light power around the implant, eventually allowing to target case-specific changes in biofilm distribution. No major interspecies difference was observed, which fosters the transferability of potential mammal testing. All findings therefore support the envisioned application of waveguiding ZrO₂ dental implants in PDI to target oral health issues.

Background: Oral and cranio-maxillofacial (OCMF) surgery is a complex specialty that requires detailed anatomical knowledge and, in fracture care, the ability to interpret imaging accurately. Mixed reality (MR) may improve spatial understanding in anatomy-based disciplines, but its value for teaching mandibular fracture classification remains uncertain. Methods: Medical and dental students at the University of Zurich were randomized 1:1 to classify four unilateral mandibular fractures using either MR or conventional two-dimensional (2D) imaging. Primary outcomes were perceived usefulness, ease of use, learning, and user satisfaction, assessed with a 15-item usability questionnaire. Secondary outcomes were fracture-classification accuracy and time to fracture classification. Results: Forty medical and dental students were included. Baseline characteristics were comparable between groups, and overall fracture-classification accuracy did not differ significantly between MR and 2D. Both groups became faster across successive cases, indicating a learning effect, although the 2D group completed classifications more quickly overall. MR participants reported higher scores for learning and user satisfaction, whereas the 2D group rated ease of use more favorably. Conclusions: MR increased user satisfaction but did not improve fracture-classification accuracy compared with 2D imaging. When integrated thoughtfully into OCMF education, MR may complement, rather than replace, conventional imaging approaches.

To assess the diagnostic performance of photon-counting detector computed tomography (PCD-CT) and cone-beam computed tomography (CBCT) at dose-matched radi

Husain AA, et al. Imaging Sci Dent. 2025 Nov;55:e64. https://doi.org/10.5624/isd.20250216

Purpose: To compare the diagnostic performance of computed tomography (CT) and magnetic resonance imaging (MRI) for surgically relevant parameters in mandibular trauma, evaluating five in-house-optimized MRI protocols with a dedicated 15-channel mandibular coil. Methods: Fifteen patients with 30 acute mandibular fractures underwent 3T MRI using five optimized protocols: UTE, StarVIBE, Dark Bone, DESS, and STIR. Three independent observers qualitatively rated image quality, fracture line visibility, cortical delineation, and bone-to-soft-tissue contrast on a five-point visual analog scale (5 = best, 1 = lowest). Quantitative analysis included measurement of the maximum distance of the fracture gap. Descriptive statistics and inter-observer agreement (Krippendorff’s α) were calculated. Results: CT enabled rapid and accurate fracture detection in all cases. Among MRI protocols, UTE (85% of fractures correctly identified and accurately diagnosed) and StarVIBE (75%) demonstrated the best diagnostic performance, with excellent fracture line visibility, sharp cortical delineation, and strong inter-observer agreement (α = 0.7–1.0.7.0). Dark Bone and DESS provided variable results, while STIR was the least suitable for fracture depiction despite good soft-tissue contrast. Quantitative assessment of fracture gap distance showed the highest accuracy with StarVIBE, demonstrating minimal deviation compared to CT (0.13–0.21 mm; p > 0.05). Conclusion: While CT remains the standard in emergency settings and for delineating complex osseous pathologies, MRI, combining CT-like and water-sensitive sequences, offers a promising radiation-free alternative for simultaneous visualization of hard and soft tissues. This approach may facilitate comprehensive radiation-free trauma evaluation, improve detection of concomitant injuries, and further support individualized clinical decision-making. Trial registration number: Swiss National Clinical Trials Portal: SNCTP000006343, ClinicalTrials.gov ID: NCT07012850.

A 14-year old boy with pronounced facial asymmetry was referred for [ ^99m Tc]Tc-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) single-photon emission computed tomography / computed tomography (SPECT/CT) of the jaw. The initial clinical suspicion of causative fibrous dysplasia in the retromolar region was ruled out through both imaging and bone biopsy. Instead, [ ^99m Tc]Tc-DPD-SPECT/CT confirmed the presence of hemimandibular hyperplasia. Cinematic rendering provided photorealistic images, effectively visualizing the asymmetry of the mandible and teeth, and the underlying increased condylar bone turnover.

Purpose: To assess postoperative fracture reduction and visualization of titanium-based and bioresorbable osteosynthesis materials in maxillofacial trauma surgery using ultra-high-resolution photon-counting detector computed tomography (PCD-CT) compared with cone-beam computed tomography (CBCT). Methods: Fractures were induced in six cadaveric pig mandibles at the angle, body, and parasymphysis and were stabilized using various titanium and bioresorbable plate systems. Specimens were scanned with CBCT and dose-matched PCD-CT in the ultra-high resolution mode, applying standard and low-dose protocols. Two observers assessed fracture reduction and implant delineation using a 5-point visual analog scale. Fracture gap and osteosynthesis materials were quantitatively measured and compared to ground-truth values. Descriptive statistics and inter-reader agreement (weighted κ) were calculated. Results: PCD-CT enabled excellent assessment of fracture reduction and visualization of osteosynthesis materials, with perfect inter-observer agreement (Median = 5, IQR, 5–5; κ = 1.0, p < 0.001), whereas low-dose CBCT showed reduced image quality and lower reproducibility (Median = 4, IQR, 4–4; κ = 0.92; p < 0.001). Bioresorbable plates were not directly visible using either scanner, but the associated screw drill holes were reliably delineated. PCD-CT achieved the smallest measurement deviations of fracture gap and osteosynthesis materials compared with ground truth, and with superior reproducibility (κ = 0.74–0.84; ICC = 0.95–0.99; all p < 0.001), outperforming CBCT across most parameters. Conclusions: Ultra-high resolution PCD-CT combines superior visualization and precise measurements compared with CBCT even at low radiation dose. With further clinical validation, these findings highlight PCD-CT’s strong potential for perioperative imaging in maxillofacial trauma, particularly benefiting younger patients who require repeated scans.

Purpose: To assess the effectiveness and feasibility of MRI-based delineation of fracture-prone regions in the oral and maxillofacial region using Black Bone and CT-like MRI protocols optimized for dentomaxillofacial imaging with a dedicated 15-channel mandibular coil. Methods: In this prospective study, healthy volunteers underwent 3T MRI using five protocols: DESS, SPACE STIR, SPACE SPAIR, T1-VIBE Dixon, and UTE. Eight trauma-prone regions, including the nasal septum, orbit, naso-orbito-ethmoidal (NOE) complex, zygomaticomaxillary complex, Le Fort regions, mandible, condyle, and dentoalveolar complex, were assessed. Image quality, artifacts, anatomical delineation, and bone-to-soft-tissue contrast were rated on a five-point Likert scale by three independent observers. Descriptive statistics and inter-rater agreement (intraclass correlation coefficients (ICCs)) were calculated. Results: Sixteen participants (37.2 ± 12.9 years; 12 males, 4 females) were included, resulting in 80 MRI volumes and 640 regions for evaluation. UTE and VIBE-DIXON sequences achieved the highest ratings for image quality, artifact susceptibility, and anatomical delineation across most fracture-prone regions (ICC: 0.793–1; all p < 0.001). UTE excelled in visualizing NOE and Le Fort regions, while VIBE-DIXON performed best in mandibular and orbital imaging. Bone-to-soft-tissue contrast was highest in UTE and VIBE-DIXON, highlighting their diagnostic potential in simultaneous soft and hard tissue imaging. Inter-rater agreement was consistently high (ICC: 0.772–0.976; all p < 0.001). Conclusion: Dedicated trauma-specific MRI protocols show promising potential as a radiation-free modality for maxillofacial trauma imaging, particularly in young adults and pediatric patients. The strengths of each protocol highlight the need for tailored sequence selection to optimize diagnostic accuracy and personalized care. Trial registration number : Swiss National Clinical Trials Portal: SNCTP000005246.