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It has not been previously possible to observe bone formation in undecalcified sections with titanium implants at high magnification because of the difficulty in sectioning bone together with implants. A method for examining the bone-implant interface in undecalcified sections is described in which implants are left in situ and confocal laser scanning microscopy (CLSM) is used to examine both the implant surface and adjacent bone. Pulsing of animals at different times with the fluorescent dyes calcein and alizarin red permitted assessment of temporal patterns of bone formation by CLSM. Reflectivity of the polished implant surface permitted accurate assessment of the position of the implant relative to labeled bone. The analysis showed that bone first formed as thin processes towards and across the implant surface, followed by further bone formation behind these processes. The interface between calcified bone tissue and the implant surface was characterized by a 10-microm space. The CLSM technique enabled detailed observations of new bone formation at the titanium implant interface.

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Autogenous bone grafting involves a second surgery and is limited by the availability of collectable bone. Coral products commercially available as bone grafts are composed of corals in their natural form. Cultured corals are recommended as a substitute to overcome the threat of extinction of natural corals. The purpose of this study was to investigate the potential of cultured coral scaffolds for periodontal tissue regeneration in class II furcation defects in dogs. The cultured coral used for this study was characterized using scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. Twelve mandibular premolar teeth from two female beagle dogs were used. Furcation defects of three left mandibular premolar teeth of each dog received the cultured coral. A control group consisting of the right mandibular premolar teeth from each dog received no implant material within the furcation defects. The dogs were then sacrificed 8 weeks post-surgery, and healing was evaluated histologically and radiologically using micro-computed tomography analysis. SEM micrographs showed a tri-dimensional ceramic structure with pore size ranging 50-250 mm. The surface of the cultured coral particles was covered with numerous rough, porous processes. XRD and FTIR results showed that the cultured coral exhibited both aragonite and calcite phases, referred to as dimorphism. The cultured coral particles implanted into the defects were completely resorbed and replaced by bone with either a Haversian structure or without any inflammatory reaction. A well-organized periodontal ligament bridging the new bone and cementum was regenerated to the top of the furcation space. Histopathological evaluation suggests that cultured coral scaffolds have the potential to regenerate periodontal tissue in class II furcation defects in dogs.

Abstract:The progenitor cells of odontoblasts have been considered to be undifferentiated dental pulp cells positive for α-smooth muscle actin (α-SMA). α-SMA is also expressed in vascular smooth muscle cells, which are well-known to differentiate into osteoblastlike cells. The osteogenesis is up-regulated under hyperglycemic conditions. Proliferation and differentiation of dental pulp cells are also considered to be upregulated under high-glucose conditions. The present study was designed to clarify the relation among human dental pulp cells (HDPCs), odontoblast progenitors and odontogenesis. Differentiation of HDPCs into odontoblasts was confirmed by examining ALP activity and calcified nodules as well as gene expressions of osteocalcin and dentin sialoprotein. The endothelial cell marker eNOS and mural cell markers, NG2, calponin and α-SMA, were immunostained. Both proliferation and differentiation of HDPCs were up-regulated in high-glucose media. NG2 and calponin proved to be more suitable markers for odontoblast progenitors than α-SMA. Odontogenesis may be related to endothelial cells.

: To assess the usefulness of confocal laser scanning microscopy (CLSM) in the examination of enamel caries, we prepared ground sections of carious teeth, stained them with fuchsin, observed them with CLSM and then compared the results with light microscopy and contact microradiography findings. The following results were obtained : 1 ) Sound enamel could not be visualized using CLSM. 2 ) In enamel caries, a surface layer, the body of the lesion and a dark zone were observed, but a translucent zone was hardly observed with CLSM. 3 ) Subsurface decalcification, which was observed with CLSM, appeared as destruction of the enamel rods, slightly toward the dentin side from the surface layer. 4) In the areas adjoining the lesion, disruption at the center or the margin of enamel rods was seen. 5) Lesions were also present alongside enamel lamella-like structures that had formed in the enamel close to the dentin. These lesions had extended laterally, engulfing the center or the margin of enamel rods near the enamel lamellalike structures. The lesions were also enlarged in the dentin adjacent to the structure. However, these lesions were not observed by light microscopy or contact microradiography. In summary, observation of enamel caries by CLSM revealed that it can give the same sort of findings as conventional histological visualization.In addition, it may also be possible to obtain three-dimensional findings with CLSM that are difficult to observe by conventional means.Therefore, we conclude that CLSM is useful for observing enamel caries.

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