Noritaka Fujii

A histological evaluation on self-setting α-tricalcium phosphate applied in the rat bone cavity

Abstract This study aimed to elucidate the biological effects of a self-setting tricalcium phosphate bone substitute (BIOPEX ® ) applied in rat femoral cortical bone cavities. Narrow penetrations through the cavity and bone marrow were prepared to obtain cellular sources. In the experimental group at day 1, a thin cell layer intruded into a narrow space between the grafted BIOPEX ® and the bottom of the cavity. From days 5 to 10, a range of tartrate-resistant acid phosphatase (TRAPase)-reactive osteoclasts accumulated on the surface of the BIOPEX ® facing the bottom of the cavity, whilst many alkaline phosphatase (ALPase)-positive osteoblasts were localized on the bone surface opposing the BIOPEX ® . However, at day 20, osteoblasts were localized neighboring the osteoclasts on the BIOPEX ® , and deposited bone matrices onto this material, implying a coupling between osteoclasts and osteoblasts. At days 30 and 40 post-operation, small remnants of BIOPEX ® particles were present in the new bone with a profile of compact bone. Thus, BIOPEX ® is resorbed by osteoclasts, and succeeded by osteoblastic bone apposition with a coupling of osteoclasts and osteoblasts at the later stage. In conclusion, the use of BIOPEX ® provides adequate bone regeneration with the profile of compact bone.

Detailed Process of Bone Remodeling After Achievement of Osseointegration in a Rat Implantation Model

Osseointegration is regarded as the most appropriate implant‐bone interface in dental implantation. However, damaged bone with empty osteocytic lacunae driven by implant cavity preparation remains even after the completion of osseointegration. Although previous studies have suggested the occurrence of bone remodeling around implants, information on its detailed process is meager. Our study aimed to examine the fate of bone around titanium implants after the establishment of osseointegration on an animal model using the rat maxilla. Titanium implants were inserted into prepared bone cavities of the rat maxilla. Bone formation and maturation processes were evaluated by double staining for alkaline phosphatase and tartrate‐resistant acid phosphatase, immunohistochemistry for bone matrix proteins, vital staining with calcein, and elemental mapping with an electron probe microanalyzer. Bone with empty osteocytic lacunae or pyknosis remained between the intact preexisting and newly formed woven bones at post 1 month. It gradually decreased to disappear completely by active bone remodeling with a synchronized coordination of alkaline phosphatase‐positive osteoblasts and tartrate‐resistant acid phosphatase‐reactive osteoclasts at post 3 months, thickening to be replaced by compact bone. Dynamic labeling showed two clear lines in the newly formed bone around the implant through this experimental period. Electron probe microanalyzer analysis demonstrated chronologically increased levels of Ca and P in the newly formed bone identical to those in the surrounding bone at post 2.5 months. These findings indicate that continuous bone remodeling after the achievement of osseointegration causes replacement of the damaged bone by compact bone as well as an improvement in bone quality. Anat Rec, 2009.

Use of a Novel Device to Assess Intraoral and Intrapharyngeal Baropressure during Sound Production

Objective: We developed a novel device that simultaneously measures oral and intrapharyngeal baropressure. The transducer has the advantage that it can be placed in any region. We determined the effect of different speech samples on baropressure in these regions. Patients and Methods: Seven healthy individuals produced speech samples comprising vowels and consonants (e.g., /aka/, /apa/, and /ash/). Two transducers were installed into the experimental plate at the incisive papillae and center of the Ah-line; a third transducer was placed in the mid-pharyngeal cavity. During each task, 3 parameters were analyzed: peak pressure, mean pressure, and the temporal relationship between sound signals and pressure changes. Results: The mean pressure did not change during the production of a single vowel; however, the pressure transiently increased during the production of the speech samples, depending on the place of articulation. Moreover, the place of articulation affected the onset and peak timing of pressure changes. Conclusions: These findings indicate that pressure changes during the production of speech samples reflect the functional aspects of speech production. In particular, simultaneous pressure recordings at multiple locations would provide precise information about speech production, compared to pressure studies that used a single pressure transducer.