Kenji Kurashina

Ectopic osteogenesis with biphasic ceramics of hydroxyapatite and tricalcium phosphate in rabbits

Porous calcium phosphate ceramics consisting of hydroxyapatite (HA) and tricalcium phosphate (TCP) with different HA to TCP ratio were implanted intramuscularly in rabbits for six months in order to carry out a comparative study on osteogenic activity of the ceramics. Bone formation was detected only in HT73 (HA to TCP ratio, 7-3) specimens. Other implants, HT28 (2-8) and HT010 (0-10), could not induce bone. After a six-month period of implantation, HT28 and HT010 implants showed obvious degradation of the implants changing their shape and size macro and microscopically. Microscopically, they showed aggregates of fine particles and appearance of multinucleated cells. However, HT73 implants was less degraded and could maintain their original structure macro and microscopically. This study showed that HT73 ceramics can induce bone in rabbit muscle tissue and it is considered that maintenance of porous structure, that is, degradation rate of the materials may be one of the affecting factors in ceramic-induced osteogenesis.

In vivo study of calcium phosphate cements: implantation of an α-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide cement paste

alpha-Tricalcium phosphate (alpha-TCP)/dicalcium phosphate dibasic (DCPD)/tetracalcium phosphate monoxide (TeCP) cement was implanted in paste form into soft tissue (rate subcutaneous sockets) and bone tissue (defects in rabbit mandibles) to evaluate the setting behaviour of the cement and tissue responses to the cement. A histological study of the soft tissue implants revealed thin fibrous capsule formation, the appearance of multinucleated giant cells on and close to the cement surface, and small clusters of the cement near the main part of the set cement which were formed by the migration of the paste while setting. X-ray diffraction (XRD) analysis of the implanted cement showed peaks for hydroxyapatite (HA) which increased as the implant period increased. Histology and microradiography of the bone tissue implants showed well-set cement without migration, active bone formation around the cement and direct bone union to it. However, the cement disappeared from the implant site in 4 of 16 specimens where intense bleeding seemed to wash away the implants while setting. From the results of the present study, we concluded that the cement is well tolerated, especially by bone tissue. This may be related to the fact that the cement sets producing HA. The cement is a promising material as a bone substitute; however, there is a problem of migration while setting in soft tissue and of exclusion from the bone defects by intense bleeding.

In vivo study of a calcium phosphate cement consisting of α-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide

Prehardened calcium phosphate cement consisting of alpha-tricalcium phosphate (alpha-TCP), dicalcium phosphate dibasic (DCPD) and tetracalcium phosphate monoxide (TeCP) was implanted in rabbit mandibles and back muscles, and studied histologically and microradiographically. In the mandibles, new bone formation occurred around the implants and increased in quantity the longer the implant period lasted. Histology, microradiography and scanning electron microscopy (SEM) demonstrated direct contact of bone and cement. Bone response to this cement was essentially the same as to hydroxyapatite (HA) ceramics, known as a biocompatible bone substitute. Material resorption was recognized, which increased with the implant period and was greater in the surface bound by soft tissue than the surface bound by bone tissue. In the back muscles, however, no calcified tissue formation occurred. Resorption proved to be faster than in the case of the mandible implants. It was concluded that the cement, in prehardened form, has good biocompatibility and is a promising material as a bone substitute.

Clinical Significance of Cellular Distribution of Moesin in Patients with Oral Squamous Cell Carcinoma

Purpose: Moesin is a linking protein of the submembraneous cytoskeleton and plays a key role in the control of cell morphology, adhesion, and motility. The aim of the present study was to elucidate the clinical significance of expression patterns of moesin in patients with oral squamous cell carcinoma (OSCC). Experimental Design: Immunohistochemistry for moesin monoclonal antibody was performed on 103 paraffin-embedded specimens from patients with primary OSCC, including 30 patients with locoregional lymph node metastasis, and in the sections from nude mice transplanted with two cell lines derived from a single human tongue cancer (SQUU-A and SQUU-B). Results: Expression patterns of moesin in OSCCs were divided into three groups: membranous pattern; mixed pattern; and cytoplasmic pattern. These expression patterns correlated with tumor size, lymph node metastasis, mode of invasion, differentiation, and lymphocytic infiltration. In about two-thirds of the patients with metastatic lymph node, homogeneous cytoplasmic expression was detected in the metastatic lymph nodes. In addition, SQUU-B with high metastatic potential showed more reduced levels of membrane-bound moesin than SQUU-A with low metastatic potential. A multivariate analysis demonstrated that expression patterns of moesin can be an independent prognostic factor. Conclusions: Our results suggest that moesin expression contributed to discriminating between patients with the potentiality for locoregional lymph node metastasis and those with a better prognosis and might improve the definition of suitable therapy for each.

Experimental cranioplasty and skeletal augmentation using an α-tricalcium phosphate/dicalcium phosphate dibasic/tetracalcium phosphate monoxide cement: a preliminary short-term experiment in rabbits

Calcium phosphate cement consisting of alpha-tricalcium phosphate (alpha-TCP), dicalcium phosphate dibasic (DCPD) and tetracalcium phosphate monoxide (TeCP) was implanted into surgically created full-thickness defects in the cranial bone (bone defect experiment) and directly onto the cranial bone under the periosteum (augmentation experiment). Three months after the implantation, the implants were retrieved with the surrounding tissues and studied histologically and micrographically to evaluate if the cement can be used as a cranioplasty and skeletal augmentation material. In the bone defect experiment, successful reconstruction of the defect was seen in 8 out of 12 specimens. Four specimens, where bleeding control was difficult at the time of implantation, showed partial loss of the cement. Histological and microradiographic studies of the successfully implanted cement revealed that new bone surrounded the implant nearly completely and united directly with the cement surface. In the augmentation experiment, the augmented area maintained the hemispherical shape and was connected tightly with the host bone. Histology and microradiography demonstrated that new bone formation was seen in the gap between the cement and the host bone, and on the outer surface (periosteum side) of the cement at the edge of the implant. From this preliminary short-term study, it could be concluded that the cement is a promising material for cranioplasty and skeletal augmentation with indications that it has good osteoconductivity.

Vital staining with iodine solution in delineating the border of oral dysplastic lesions

OBJECTIVE The borders of dysplastic lesions of the oral mucosa are often vaguely delineated. The purpose of this study was to determine if vital staining with an iodine solution can precisely delineate the boundary of superficial spread of dysplastic or malignant epithelium. STUDY DESIGN Thirty-seven biopsies were obtained from 18 patients with possible malignant lesions of the oral mucosa. Deviations between the clinical boundary obtained with vital staining and the histopathologic boundary determined in hemotoxylin-eosin-and lectin-stained sections were measured with light microscopy. RESULT The clinical boundaries defined with the vital staining agreed well with the pathologic border lines and were in error by less than 3 mm. CONCLUSION This result suggests that vital staining with an iodine solution has great potential in determining the extent and precise borders of the dysplastic epithelium. A 5-mm border of normal tissue peripheral to the iodine-positive area would be adequate for the complete removal of the dysplastic epithelium.

Efficacy of a mandibular manipulation technique in reducing the permanently displaced temporomandibular joint disc

PURPOSE The purpose of this study was to determine whether disc reduction occurred in patients with closed lock after mandibular manipulation (MM) and to analyze the factors that influenced the result. PATIENTS AND METHODS Two hundred fifteen patients with closed lock received MM. Of these, 74 patients (79 joints) were assessed by means of magnetic resonance imaging (MRI) for disc reduction. The results of the MRI were compared with the findings from the clinical and radiographic examinations. RESULTS According to the MRI assessment, only 18% (14 of 79) of the joints had successful disc reduction. The unsuccessfully treated joints had severe joint pain, disc displacement, condylar bone change, and disc deformity. CONCLUSIONS The results of this study suggest that successful reduction of the disc by MM is rare. They also suggest that MM is least effective in the advanced stages of internal derangement, when the disc becomes deformed.

Change of position of the temporomandibular joint disk with insertion of a disk-repositioning appliance

OBJECTIVE We report alteration of the temporomandibular joint disk and the condyle position through the construction of a mandibular full-coverage occlusal appliance (often referred to as a disk repositioning appliance). STUDY DESIGN Forty-five joints with displaced disks with reduction were available for the study. We assessed these joints for disk recapture and the change of disk position with insertion of the appliance using magnetic resonance imaging. RESULTS Of the 41 joints that had a recaptured disk with insertion of the splint, 25 slid in a posterior direction, although the amount of movement was negligible. No disk slid posteriorly in the joints without splint capture. CONCLUSIONS On the basis of our results, we conclude that many of the occasionally displaced disks might have moved backward with successful treatment involving a disk-repositioning splint. However, the amount of the movement was negligible.

Clinical effect of full coverage occlusal splint therapy for specific temporomandibular disorder conditions and symptoms

PURPOSE The purpose of this retrospective study was to evaluate the effect of maxillary full-coverage occlusal splint (stabilization splint) therapy for specific temporomandibular disorders and their symptoms/signs. MATERIAL AND METHODS This study assessed the outcome of 232 patients who were suffering from chronic pain on movements, joint noise except reciprocal clicking, and difficulty of mouth opening. All were treated with the stabilization splint alone. RESULTS The total remission rate was 41% and, including those reporting some improvement, the rate was 84%. The presence of displaced disk significantly decreased the success rate. However, the presence or absence of radiographic changes in the temporomandibular joint did not influence the treatment outcome. CONCLUSION From this study, it is suggested that the stabilization splint therapy may be a useful treatment modality in treatment of temporomandibular disorders, especially for the patients without clinical evidence of displaced disk.

Temporomandibular joint response to mandibular deviation in rabbits detected by 3D micro-CT imaging

PURPOSE Micro-computed tomography enables continuous and dynamic observation of the three-dimensional morphology of small structures. We observed morphological changes of the temporomandibular joint condyle under mandibular deviation continuously in an animal model by micro-computed tomography. METHODS Twelve Dutch rabbits were used (9 as experimental and 3 as control). In the experimental rabbits, the mandible was deviated posteriorly on the left side using an elastic band. Bilateral temporomandibular joints were scanned by micro-computed tomography preoperatively and at 3, 6, and 12 weeks after the operation. Histopathological examination was also carried out to confirm the changes. RESULTS It was shown that mandibular deviation induces condyle resorption in either ipsilateral or contralateral temporomandibular joint, which consequently makes the condyle smaller. Bone resorption settled down earlier in the contralateral joint and the quantity of bone resorption on the contralateral side was smaller than on the experimental side. Histopathological examination also showed destructive bone changes in the condyle, although they could not completely reflect the morphological changes. CONCLUSIONS These results suggested that reduction of the condylar size occurred as an adaptive change to mandibular deviation.