The relative motion between the tooth and alveolar bone is facilitated by the soft-hard tissue interfaces which include periodontal ligament-bone (PDL-bone) and periodontal ligamentcementum (PDL-cementum). The soft-hard tissue interfaces are responsible for attachment and are critical to the overall biomechanical efficiency of the bone-tooth complex. In this study, the PDLbone and PDL-cementum attachment sites in human molars were investigated to identify the structural orientation and integration of the PDL with bone and cementum. These attachment sites were characterized from a combined materials and mechanics perspective and were related to macro-scale function.High resolution complimentary imaging techniques including atomic force microscopy, scanning electron microscopy and micro-scale X-ray computed tomography (Micro XCT™) illustrated two distinct orientations of PDL; circumferential-PDL (cir-PDL) and radial-PDL (rad-PDL). Within the PDL-space, the primary orientation of the ligament was radial (rad-PDL) as is well known. Interestingly, circumferential orientation of PDL continuous with rad-PDL was observed adjacent to alveolar bone and cementum. The integration of the cir-PDL was identified by 1 to 2 μm diameter PDL-inserts or Sharpey's fibers in alveolar bone and cementum. Chemically and biochemically the cir-PDL adjacent to bone and cementum was identified by relatively higher carbon and lower calcium including the localization of small leucine rich proteins responsible for maintaining soft-hard tissue cohesion, stiffness and hygroscopic nature of PDL-bone and PDLcementum attachment sites. The combined structural and chemical properties provided graded stiffness characteristics of PDL-bone (E r range for PDL: 10 -50 MPa; bone: 0.2 -9.6 GPa) and PDL-cementum (E r range for cementum: 1.1 -8.3 GPa), which was related to the macro-scale function of the bone-tooth complex.

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Purpose: The morphometry of the pulmonary acini in the murine (C57Bl/6) lung were studied using high resolution microCT (HRµCT) scans. Previous studies investigated the morphometry of the acinus of rats and rabbits using silicon rubber casts of the lungs [Weibel et al, 1987] and set a standard for morphologic parameters of the acinus. New technological innovations allow non−destructive sub−sample (3D) of the lung with 1−2µm/voxel. Methods: Preparation: Lungs were fixed in situ via instillation using a Heitzman solution. Lungs were excised and dried for radiographic assessment. Imaging: An XRadia MicroCT scanner (microXCT), capable of ∼1µm/voxel was used for non−destructive 3D image acquisition within the fixed lungs. Morphometry: Following a whole lung scan (50µm/voxel) for determining sample locations within the lung, a HRµCT scan was gathered. Intraacinar airways were segmented from within the HRµCT imaged volume. From this we calculate the following parameters similar to microscopic assessment of Weibel et al.: volume of acinus; branching pattern, segment lengths, inner and outer diameter of acinar airways; number of terminal alveolar sacs; acinar airway pathlength distribution.[figure1]Results and Conclusions: Non−destructive imaging allows for partitioning parenchyma into individual acini and assess their morphometry quantitatively. Our future goals are to characterize the normal murine lung across strains. This abstract is funded by: NIH R01−HL−080285. Am J Respir Crit Care Med 179;2009:A1055 Online Abstracts Issue

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