The main goal of this study was to introduce a novel three-dimensional procedure to objectively quantify both inner and outer condylar remodelling on preoperative multi-slice computed tomography (MSCT) and postoperative cone-beam computed tomography (CBCT) images. Second, the reliability and accuracy of this condylar volume quantification method was assessed. The mandibles of 20 patients (11 female and 9 male) who underwent bimaxillary surgery were semi-automatically extracted from MSCT/CBCT scans and rendered in 3D. The resulting condyles were spatially matched by using an anatomical landmark-based registration procedure. A standardized sphere was created around each condyle, and the condylar bone volume within this selected region of interest was automatically calculated. To investigate the reproducibility of the method, inter- and intra-observer reliability was calculated for assessments made by two experienced radiologists twice five months apart in a set of ten randomly selected patients. To test the accuracy of the bone segmentation, the inner and outer bone structures of one dry mandible, scanned according to the clinical set-up, were compared with the gold standard, micro-CT. Thirty-eight condyles showed a significant (P＜0.05) mean bone volume decrease of 26.4%±11.4% (502.9 mm3±268.1mm3). No significant effects of side, sex or age were found. Good to excellent(ICC＞0.6) intra- and inter-observer reliability was observed for both MSCT and CBCT. Moreover, the bone segmentation accuracy was less than one voxel (0.4mm) for MSCT (0.3 mm±0.2 mm) and CBCT (0.4 mm±0.3 mm), thus indicating the clinical potential of this method for objective follow-up in pathological condylar resorption.

Purpose: This study was performed to introduce an in vivo hybrid multimodality technique involving the coregistration of micro-computed tomography (micro-CT) and high-resolution magnetic resonance imaging (HR-MRI) to concomitantly visualize and quantify mineralization and vascularization at follow-up in a rat model. Materials and Methods: Three adult female rats were randomly assigned as test subjects, with 1 rat serving as a control subject. For 20 weeks, the test rats received a weekly intravenous injection of 30 μg/kg zoledronic acid, and the control rat was administered a similar dose of normal saline. Bilateral extraction of the lower first and second molarswas performed after 10 weeks. All rats were scanned once every 4 weeks with both micro-CT and HR-MRI. Micro-CT and HR-MRI images were registered and fused in the same 3-dimensional region to quantify blood flow velocity and trabecular bone thickness at T0 (baseline), T4 (4 weeks), T8 (8 weeks), T12 (12 weeks), T16 (16 weeks), and T20 (20 weeks). Histological assessment was the gold standard with which the findings were compared. Results: The histomorphometric images at T20 aligned with the HR-MRI findings, with both test and control rats demonstrating reduced trabecular bone vasculature and blood vessel density. The micro-CT findings were also consistent with the histomorphometric changes, which revealed that the test rats had thicker trabecular bone and smaller marrow spaces than the control rat. Conclusion The combination of micro-CT and HR-MRI may be considered a powerful non-invasive novel technique for the longitudinal quantification of localized mineralization and vascularization.

Although neurophysiological and psychophysical proof of osseoperception is accumulating, histomorphometric evidence for the neural mechanisms of functional compensation following immediate and delayed implant loading is still lacking. For this randomized split-mouth study, six mongrel dogs randomly received one of four treatment protocols at 36 implant-recipient sites over 16 weeks (third maxillary incisor, third and fourth mandibular premolar): immediate implant placement and immediate loading (IIP+IL); delayed implant placement and delayed loading (DIP+DL); delayed implant placement and immediate loading (DIP+IL); and natural extraction socket healing (control). Histomorphometry was performed in the peri-implant bone and soft tissues within 300 µm around the implants. Immunocytochemistry and transmission electron microscopy were used to confirm the presence of neural structures and to reveal their ultrastructural characteristics, respectively. Myelinated nerve fibres densely populated the peri-implant crestal gingival and apical regions, although they were also identified in the woven bone and in the osteons near the implant threads. Compared with the control group in the mandible, the group that received IIP+IL showed a higher innervation (in N⋅mm⁻², 5.94 ± 1.12 vs. 3.15 ± 0.63, P<0.001) and smaller fibre diameter (in µm, 1.37 ± 0.05 vs. 1.64 ± 0.13, P=0.016), smaller axon diameter (in µm, 0.89 ± 0.05 vs. 1.24 ± 0.10, P=0.009) and g-ratio (0.64 ± 0.04 vs. 0.76 ± 0.05, P<0.001) in the middle region around the implants. Compared with DIP+IL in the mandible, IIP+IL had a higher nerve density (in N⋅mm⁻², 13.23 ± 2.54 vs. 9.64 ± 1.86, P=0.027), greater fibre diameter (in µm, 1.32 ± 0.02 vs. 1.20 ± 0.04, P=0.021), greater axon diameter (in µm, 0.92 ± 0.01 vs. 0.89 ± 0.03, P=0.035) and lower g-ratio (0.69 ± 0.01 vs. 0.74 ± 0.01, P=0.033) in the apical region around the implants. It may be assumed that the treatment protocol with IIP+IL is the preferred method to allow optimized peri-implant re-innervation, but further functional measurements are still required.
Animals ; Dental Implants ; Dogs ; Microscopy, Electron, Transmission ; Nerve Fibers ; Pilot Projects