Michiko Yoshizawa

Clinical study on prognostic factors for autotransplantation of teeth with complete root formation

Autotransplantation is often performed to replace a missing tooth, but tooth autotransplantation has been reported in fewer teeth with complete root formation than those with incomplete root formation. The aim of this prospective study was to evaluate the factors that affect the prognosis of autotransplantation of teeth with complete root formation. 109 patients with 117 transplants were studied. Of the 117 transplants investigated, 14 (12%) failed during the observation period. The overall 1-year survival rate was 96%; the 5-year survival rate was 84%. The major causes of failure were unsuccessful initial healing and replacement root resorption with periodontal inflammation. Factors significantly associated with unsuccessful transplantation, in single factor analysis, were age 40 years or more, molar tooth as donor, probing pocket depth to 4mm or more, history of root canal treatment, multi-rooted teeth and fixation with sutures. Pocket depth of 4mm or more and history of root canal treatment appeared to increase the risk of unsuccessful transplantation in multivariate analysis. It is suggested that the pocket depth of the donor tooth and history of root canal treatment are related to the healing of paratransplantal tissue and root resorption.

Histopathological study of lymphatic invasion in squamous cell carcinoma (O-1N) with high potential of lymph node metastasis

The process of lymph node metastasis was studied in an animal model (termed O-1N) that was successfully established using a metastatic tumor to the submandibular lymph node from a chemically induced squamous cell carcinoma of the hamster tongue. The model has been maintained by serial transplantation of metastatic tumors into the buccal pouch. Lymphovascular invasion of transplanted O-1N in the tongue was examined in serial histologic sections. Lymphatic vessels were distinguished from blood vessels by Massons trichrome stain for vascular smooth muscle, BSA-I lectin binding for vascular endothelium, and laminin and type IV collagen immunostaining for the vascular basement membrane. Transplanted tumors enlarged progressively with invasion of surrounding tissues of the tongue and resulted in lymph node metastasis in all animals with successful takes. Local growth of the tumors in the tongue was accompanied by stromal proliferation with abundant dilated lymphatic vessels which contained clusters of tumor cells. On serial sections, the carcinoma cell clusters in lymphatics in the close proximity of tumor nests were in continuity with adjacent tumor nests, whereas such continuity was not recognized in those occurring apart from tumor nests. The formation of isolated carcinoma cell clusters resulting from disintegration of elongated processes of tumor nests with invasion of lymphatics and subsequent transport in lymphatics and deposition in lymph nodes in clusters were well demonstrated in other serial sections. The key step of lymph node metastasis therefore appears to be direct invasion of lymphatic vessels by tumor cells, similar to their invasion of adjacent tissues but different from the way that blood cells escape through vessel walls. Proliferation of lymphatics around tumor nests and transport of tumor cells in clusters would also contribute to the production of metastatic deposits in lymph nodes.

Tetraspanin gene expression levels as potential biomarkers for malignancy of gingival squamous cell carcinoma

Accurate assessment of malignancy in oral squamous cell carcinoma is essential to optimize treatment planning. To detect a biomarker related to malignant propensity in gingival squamous cell carcinoma (GSCC), quantitative gene expression analysis of tetraspanin family genes was conducted. In 73 cases of GSCC, total RNA was extracted from carcinoma tissues, and gene expression was analyzed by quantitative real time‐PCR. Six tetraspanin family genes (CD9, CD63, CD81, CD82, CD151, NAG‐2) were investigated. Housekeeping genes (ACTB and GAPDH), anchor protein genes (JUP and PXN) and an integrin gene (ITGA3) were used as reference genes. Forty‐five gene expression ratios were calculated from these 11 gene expression levels and were analyzed with clinical parameters using multivariate statistical methods. According to the results of the logistic regression analysis subjecting cervical lymph node metastasis as a target variable, CD9/ACTB (p = 0.013) or CD9/CD82 (p = 0.013) in addition to tumor size (p = 0.028) were detected as significant factors. In Cox proportional hazards regression analysis, delayed cervical lymph node metastasis (p = 0.039) and tumor cell positive surgical margin (p = 0.032) in addition to CD151/GAPDH (p = 0.024) were detected as significant factors for death outcome. A Kaplan‐Meier survival curve presented a significantly lower survival rate of the group with a CD151/GAPDH value of 10 or more (log rank and generalized Wilcoxon tests: p = 0.0003). Results of this study present the usefulness of CD9 and CD151 expression levels as biomarkers for assessment of malignancy in GSCC. They also indicate that detection of residual tumor cells at the surgical margin and the biological malignancy of a tumor interdependently affects prognosis.

Vascular invasion in squamous cell carcinomas of human oral mucosa

The process of vascular invasion of human oral squamous cell carcinomas was histologically and immunohistochemically studied in surgical and autopsy specimens. Hematoxylin-eosin, Massons trichrome, and immunohistochemical stainings for Ulex europaeus I lectin binding, CD31, and type IV collagen were done to differentiate lymphatic and blood vessels and to demonstrate basement membranes in vascular walls and around carcinoma cell nests was observed. With growth of tumor, there was mechanical disruption of vascular walls and endothelial cells by carcinoma cell nests. After disrupting vascular walls, they invaded into the lumen as clusters, not as single cells. At the blood vessel invasion sites, inflammatory reactions were seen around carcinoma cell nests inside as well as outside lumina with microthrombotic reactions due to endothelial injury. At the lymphatic invasion sites, carcinoma cell nests maintained their volume inside the lumen and the cells adhered tightly to each other, and inflammatory reaction was scarcely seen. These findings showed that mechanical pressure has an important role in the vascular invasion of human oral squamous cell carcinoma.

Changes in overnight arterial oxygen saturation after mandibular setback

Mandibular setback reduces space in the pharyngeal airway, and it has been suggested that it might induce sleep-disordered breathing. We report on its effects on space in the pharyngeal airway and respiratory function during sleep. We studied 78 patients (29 men and 49 women) in whom skeletal class III malocclusions had been corrected. The mean (range) age at operation was 24 (16-38) years and body mass index (BMI) 21.4 (16.1-30 .9)kg/m(2). Morphological changes were evaluated on lateral cephalograms taken three times: preoperatively, a few days postoperatively, and more than 6 months postoperatively. Overnight arterial oxygen saturation (SpO2) was measured by pulse oximetry 6 times: preoperatively, and on days 1, 3, 5, and 7, and 6 months postoperatively; oximetric indices were calculated. Those immediately after mandibular setback were significantly worse than those preoperatively, although they gradually improved. There were positive correlations between BMI and oximetric indices, and little association between changes in mandibular position and oximetric indices. There was no evidence of sleep-disordered breathing 6 months after mandibular setback because most patients adapt to the new environment for respiratory function during sleep. However, some (particularly obese) patients may develop sleep-disordered breathing just after mandibular setback. In such patients attention should be paid to respiratory function during sleep in the immediate postoperative period, and careful postoperative follow-up is needed.

Prognostic factors for autotransplantation of teeth with complete root formation.

OBJECTIVES The aim of the present study was to evaluate the factors affecting the prognosis of the autotransplantation of teeth with complete root formation. STUDY DESIGN A total of 259 transplanted teeth were studied. The significance of each of the prognostic factors was examined in 2 ways, first in a univariate analysis and then in a multivariate analysis. The comprehensive risk combining these factors that remained after multivariate analysis was calculated. RESULTS Among 259 transplanted teeth, 27 (10.4%) were judged as unsuccessful cases. In the multivariate analysis, history of root canal treatment of donor tooth, multirooted, maxillary tooth as a donor, and duration of tooth absence at recipient site remained significantly associated with unsuccessful transplantation. Multifarious combination of the significant prognostic factors can decrease the comprehensive risk. CONCLUSIONS Minimizing the comprehensive risk by combining significant prognostic factors improved the prognosis of autotransplantation of teeth with complete root formation.

Keratinocytes of Tissue-Engineered Human Oral Mucosa Promote Re-Epithelialization After Intraoral Grafting in Athymic Mice

PURPOSE The objective of this study was to investigate the role of grafted oral keratinocytes in a transplanted ex vivo-produced oral mucosa equivalent (EVPOME) in the regeneration and/or healing process of the oral mucosa at the recipient site. MATERIALS AND METHODS The EVPOME was developed in a serum-free defined culture system without a feeder layer. EVPOME is composed of a stratified layer of human oral keratinocytes that are seeded onto a human cadaveric dermis, AlloDerm (LifeCell, Branchburg, NJ). Intraorally grafted EVPOMEs in athymic mice (BALB/c) were excised, contiguous with the surrounding oral mucosa, on days 5, 7, 14, and 21 after grafting. Serial sections were stained with hematoxylin-eosin and immunohistochemically analyzed for cytokeratin 17 (CK17) expression to distinguish the human-cultured EVPOME epithelial keratinocytes from murine oral keratinocytes. RESULTS All EVPOME epithelial cells showed intense immunoreactivity for CK17, whereas mouse buccal mucosal epithelial cells did not show CK17 immunoreactivity. The grafted EVPOME maintained a stratified epithelial layer for up to 5 days after grafting. By day 7 after grafting, a portion of the EVPOME epithelial layer peeled away from the AlloDerm, and a thin, CK17-immunonegative epithelial layer extended from the adjacent thick epithelial layer of the mouse and contacted the CK17-immunopositive EVPOME epithelium. From days 14 to 21 after grafting, the stratification of the CK17-immunonegative continuous mouse epithelium increased compared with earlier time points and showed a similar appearance to the epithelium of the adjacent mouse mucosa. In contrast, no epithelial coverage of the AlloDerm that was grafted without keratinocytes was observed for up to 21 days after grafting. The grafted AlloDerm without cells resulted in tissue necrosis that was accompanied by a dramatic infiltration of inflammatory cells by day 14. CONCLUSIONS These findings suggest that grafting of EVPOME with viable oral keratinocytes onto an intraoral mucosal wound plays an active role in promotion of re-epithelialization of the oral wound during the subsequent healing process.

Histological examination of bone regeneration achieved by combining grafting with hydroxyapatite and thermoplastic bioresorbable plates

In this study, we present a novel guided bone regeneration (GBR) concept that consists of combining Boneject, a bone substitute containing atelocollagen and bovine hydroxyapatite particles, with thermoplastic, bioresorbable plates (DeltaSystem) known to resist mechanical loading. In rat calvariae, standardized bone defects were filled with Boneject and covered with a convex DeltaSystem plate. Tissue from rats at 1, 2, 4, 8, and 12 weeks postoperation were fixed with an aldehyde solution, and the new bone formed at the defects was histologically assessed. At 1 week, alkaline phosphatase (ALP)-negative cells deriving from the bottom region of the defect could be found up to half the height of the cavity. Boneject particle surfaces in the bottom region revealed an intense osteopontin immunopositivity whereas those in the upper region did not. Tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts accumulated on the surfaces of osteopontin-coated particles. A newly formed, woven-like bone featuring ALP-positive osteoblasts extended from the native bone. At the second week, the newly formed woven bone had surrounded the Boneject particles. Cement lines, which indicate active bone remodeling, could be observed in the new bone despite its immaturity. Four weeks after surgery, the new bone had reached the height of the DeltaSystem plate, and just beneath it a periostin-positive fibrous layer covered the mix of new bone and Boneject particles. By then, despite having acceptable histological features, electron probe microanalyzer (EPMA) and transmission electron microscope (TEM) analyses revealed that the new bone could not be regarded as compact bone. At 8 and 12 weeks, the new bone showed compact bone-like features according to TEM and EPMA assessments. Summarizing, the combination of a bone substitute such as Boneject and a rigid, bioresorbable plate appears to be osteoconductive and to promote bone remodeling, leading to the genesis of a tissue similar to the one that is regarded as the “gold standard” for bone regeneration: the compact bone.

III–1 Vertical Distraction Osteogenesis of a Reconstructed Mandible with a Free Non-Vascularized Iliac Bone Garft Combined with LIPUS Treatment: A Case Report

Introduction: We report a patient who underwent vertical distraction osteogenesis of a reconstructed mandible. Treatment involved a free non-vascularized iliac bone graft combined with LIPUS treatment, followed by dental implant treatment. Case: The patient was a 37-year-old female who underwent mandibular resection for treatment of a benign ameloblastoma. The postoperative course was uneventful, and dental implant treatment was planned in the reconstructed mandible. However, bone height in the reconstructed mandible was insufficient for ideal prosthetic rehabilitation. Therefore, we performed vertical distraction osteogenesis of the reconstructed mandible, resulting in a total distraction length of 14 mm. LIPUS was performed to accelerate bone healing in the distracted area for 3 months during the consolidation period. After that, there was a bone defect between the native bone and the mesial side of the transport segment. The patient underwent grafting of bone harvested from the distal ridge of the transport segment and the mandibular ramus, to obtain sufficient volume of the alveolar ridge. Bone was held in position with titanium mesh. CT images demonstrated that density of the iliac bone in the reconstructed mandible was sufficient for implant treatment. Eventually, the patient received dental implant prosthetic rehabilitation in the reconstructed mandible. Discussion and Conclusion: Bone density of an iliac bone graft is often less than that of native bone. In this case, we performed vertical distraction osteogenesis combined with LIPUS to generate sufficient bone height and density. The patient successfully received adequate esthetics and function of the implant-supported prosthesis.

A Case of Bone Resorption Following Augmentation Genioplasty with a Silicone Implant

There are two types of operation for chin augmentation. One is augmentation genioplasty by means of horizontal osteotomy, and the other is implantation with alloplastic materials, such as silicone implants and hydroxyapatite blocks. Augmentation genioplasty with silicone implants is easy and can be performed under local anesthesia. However, augmentation genioplasty with silicone implants tends to produce post-operative infection, bone resorption of the chin, and malposition of implants. We report a case of mandibular resorption and infection following augmentation genioplasty with a silicone implant.A 50-year-old female underwent augmentation genioplasty with silicone implantation about 8 years ago in Korea. At 7 years post-operation she noticed swelling and paresthesia in the mental region and so consulted our department. An abscess and an operative scar were observed in the intraoral mandibular incisor region. An implant was observed in the mental region, and some absorption of the bone beneath the implant radiographically. The implant was removed surgically. The implant surrounded by granulation tissue caved in the surface of the chin bone which was absorbed irregularly. These findings suggested that the resorption of surface bone under silastic implant was caused by the continuous pressure of musculus mentalis.