Biomedical subjects

T Suetsugu

Publications and source records attributed to T Suetsugu.

At least 37 records · Page 2Linked to original sources

PubMed1997

Histological comparison of early wound healing following dense hydroxyapatite granule grafting and barrier placement in surgically-created bone defects neighboring implants.

The purpose of this study was to examine early wound healing following grafting of dense hydroxyapatite granules (HA granules) and barrier placement in surgically-created bone defects surrounding implants. Eight healthy adult dogs with an average weight of 15 kg were used in this study. Thirty-two bone defects measuring 4 mm x 4 mm were removed with a surgical bur to form continuous bucco-lingual bone defects and 32 implants (16 titanium [Ti]) and 16 hydroxyapatite-coated [HA]) were then placed into the defects. Four implant groups were created: 1) grafting HA; 2) covering with an expanded polytetrafluoroethylene (ePTFE) membrane; 3) grafting HA and covering with ePTFE membrane; and 4) control (no treatment). Animals were sacrificed 28 days after surgery. Histological sections revealed large amounts of newly-formed bone in all bone defects surrounding the implants treated with ePTFE membranes alone. Fibrous encapsulation of HA granules was observed in the defects of the HA granules grafting group. In the group with grafting of HA granules and covering with ePTFE membranes, small amounts of bone tissue were observed among HA granules, but most HA granules were surrounded with fibrous tissue. Bone defects were completely filled with connective tissue in the control group. There were no differences in the histological findings between Ti and HA-coated implants in all cases. Histomorphometric data disclosed that the presence of HA granules in the bone defects significantly arrested bone formation. Our study suggests that the grafting of dense HA into bone defects surrounding implants will result in fibrous healing during the early healing stage.

Alveolar Bone Loss↗

PubMed1997

A study of the regional distribution of bone formed around hydroxyapatite implants in the tibiae of streptozotocin-induced diabetic rats using multiple fluorescent labeling and confocal laser scanning microscopy.

The present study was designed to compare the amount and regional distribution of bone formation around hydroxyapatite (HA) implants in normal (control) rats with that of animals with diabetes mellitus (DM), induced by streptozotocin 2 weeks prior to implant placement. Calcein (CAL), alizarin complexone (AL), and tetracycline (TC) were injected on the 7th, 14th, and 21st days after implantation, respectively, and the rats were sacrificed on the 28th day after implantation. Seventy-microns undecalcified sections of the HA-bone interface in both groups were then prepared for confocal laser scanning microscopy (CLSM) observation. In both groups, bone formation developed from the HA surface to the endosteum, periosteum, or bone marrow. In the control group, around the HA close to the endosteum and periosteum, the new bone showed an extensive lamination pattern of three color layers (CAL, AL, and TC), but in the DM group the labeling density of TC on the 21st day was low. In contrast, on the lateral part of the HA surface (away from the endosteum and periosteum), there was considerably less bone formation in the control group, and in the DM group it was almost completely suppressed. These findings indicate that bone formation around the HA was initiated from the HA surface in the control group, while in the DM group, bone formation along the lateral part of the HA away from the endosteum and periosteum was almost completely suppressed. Furthermore, it is also suggested that in the new bone along the HA close to the endosteum and periosteum, only calcification on the 21st day was depressed.

Animals↗

PubMed1997

The effects of diabetes on the interface between hydroxyapatite implants and bone in rat tibia.

We examined the influence of diabetes on the implant-bone interface of hydroxyapatite (HA) implants inserted transcortically and extending into the medullary canal of rat tibiae, and quantitatively assessed the differences in bone reaction using an image processing system. Forty male Wistar King A rats (aged 5 weeks) were used in this experiment; they were sacrificed 84 days after implant placement. Toluidine blue-stained undecalcified sections were prepared for histological observation and image analysis, and the labeled sections were observed by confocal laser scanning microscopy. The HA implants in the bone marrow area in the control group were completely encapsulated with a bone layer, and there were some osteoblast-like cells in the bone lacunae apposing the implant surface. The HA implants in the diabetes-induced (DI) group were partially surrounded with a thin bone layer, and there were some fibroblasts running parallel to the implant surface at areas of no bone contact. Quantitative evaluation indicated that the control group showed significantly higher bone contact rate, bone contact thickness, and bone contact area than the DI group. The DI group showed approximately 30% reduction in the percentage of bone contact and 50% reduction in the thickness and the area of surrounding bone tissue.

Animals↗

PubMed1997

Failing hollow implants examined by light microscopy and image processing.

The purpose of this study was to evaluate the radiologic, histologic, and histometric findings of three failing hollow implants. On periapical radiographs, these implants showed vertical bone loss up to the hollow portion around the implant. Examination of the histologic sections disclosed that the hollow portions of all the implants were almost filled with bone tissue, although slight bone resorption and presence of granulation tissue infiltrated with inflammatory cells was observed coronal to the hollow portion. Histometric analysis disclosed that the average percent bone contact was 93.1% in case 1, 90.9% in case 2, and 84.3% in case 3 and the average percent bone filling was 42.1%, 50.5%, and 33.8%, respectively. Consequently, there seems to be some potential for successful treatment of these implants because the destructive changes were limited to the coronal aspects of the implant.

Alveolar Bone Loss↗

PubMed1997

Abscess formation around a hydroxyapatite-coated implant placed into the extraction socket with autogenous bone graft. A histological study using light microscopy, image processing, and confocal laser scanning microscopy.

The purpose of this study was to evaluate the radiologic, histologic, and histometric findings for a retrieved hydroxyapatite (HA)-coated implant which had been placed into a fresh extraction socket with autogenous bone graft 3 months previously. A periapical radiography disclosed a vertical bone loss around the implant cervix. Examination of histologic section disclosed that granulation tissue including bone chips around the cervix, and newly-formed bone tissue around the grafted bone tissue on the HA coated surface. In the confocal laser scanning microscopic findings toluidine blue-negative bone tissue showed autofluorescence. Histometric analysis indicated that the average percent bone contact was 29.2% (ranged 26.4% to 34.1%). Suspected reasons for failure were an early exposure of the barrier membrane, its early removal, the implant placement into an infected site, inadequate antibiotic premedication, and/or poor control of infections around teeth prior to implant surgery and around implants before and after placement of barrier membrane.

Abscess↗

PubMed1997

Various designs of ceramometal crown for implant restorations.

The posterior design of the implant superstructure (the ceramometal crown) was classified into four categories: a ceramometal crown with an access hole on top; a cemented ceramometal crown; a ceramometal crown retained with a lingual screw; and a telescopic ceramometal crown. Cemented ceramometal crowns and telescopic ceramometal crowns are considered simpler, more esthetic, and more resistant to fracture among the four models.

Bicuspid↗

PubMed1996

Light and electron microscopic studies of bone-titanium interface in the tibiae of young and mature rats.

Bone-titanium contact was examined in young and mature rats on various days after insertion of pure titanium into the tibia. Under light microscopy, on the 14th day, lamellar mature bone was initially formed, and was seen to make direct contact with the titanium in both groups. In young rats on the 28th day, bone-titanium contact was greater than that in mature animals. On 1-micron sections, an amorphous zone 0.5-1.0 micron thick was found around the titanium, and a slender cell layer lay parallel to the implant, forming the superficial layer of the amorphous zone. Ultrastructurally, these slender cells were identified as osteoblastlike cells and made direct contact with the implant via a 20-50-nm thin amorphous zone. Below this cell layer, a collagen-containing, poorly mineralized zone was present and bordered by lamellar bone with a lamina limitans-like structure. However, this cell layer was absent in places, and therefore the thick amorphous zone without slender cell layer consisted ultrastructurally of a 20-50-nm thin amorphous zone and a poorly mineralized zone bordered by the lamellar bone. Sometimes this poorly mineralized zone was absent, and in such cases, the lamellar bone contacted the titanium by the thin amorphous zone formed on the lamina limitans-like structure. Thus, although bone was seen to make contact with the titanium implant, ultrastructurally a 20-50-nm thin amorphous zone, a slender cell layer, and/or a poorly mineralized zone were interposed between the bone and titanium.

Animals↗

PubMed1996

The relationship between inclination of the occlusal plane and jaw closing path.

The occlusal plane is determined according to morphologic guides such as Camper's plane and the position of the retromolar pad. However, there is no information available about the functional orientation of the occlusal plane. The purpose of this study was to investigate the relationship between the inclination of the occlusal plane and jaw closing movement path in the sagittal plane. Data from 38 young dentate subjects were obtained with a system that measures jaw movements. It was found that the occlusal plane and the masticatory closing path were consistent in maintaining an almost perpendicular relationship regardless of the variation in the inclination of the occlusal plane. This finding appears to be based on the functional formation of the occlusal plane according to the growth and change of masticatory muscles. The correlation between the inclination of the occlusal plane and masticatory closing movement could serve as the background for the functional significance of the occlusal plane.

Adult↗

PubMed1996

Accurate presurgical determination for implant placement by using computerized tomography scan.

A template is often used for the presurgical planning of implant placement. However, a major drawback is that the CT image of the radiopaque marker is not often clear. This article describes a method of fabricating a template with a stainless steel tube sprue for accurate radiographic evaluation and implant placement. Stainless steel tube sprues are inexpensive, indicate the eventual implant inclination, and facilitate precise placement, from the CT scan without any interference from scattered radiation.

Dental Implantation, Endosseous↗

PubMed1996

Histologic investigation of hollow implants retrieved for psychological reasons.

OBJECTIVE: The purpose of this study was to radiologically, histologically, and histometrically evaluate bone in the hollow portion of three implants retrieved for psychological reasons. STUDY DESIGN: Three hollow implants retrieved from two patients were studied. We investigated the radiologic and histologic changes of these implants with the use of radiographs, light microscopy, image processing, and fluorescent microscopy. RESULTS: There were no radiologic and histologic degeneration around the implants. Histometric analysis of the hollow indicated that the average percentage of bone contact rate was 33.5% in case 1, 74.5% in case 2, and 18.4% in case 3; the average percentage of bone filling was 25.1%, 33.9%, and 6.6%, respectively. There was a great variation among the three cases in bone to implant contact and bone filling. CONCLUSION: The hollow portion in case 1 that penetrated into the maxillary sinus was encapsulated with fibrous tissue. The amount of bone tissue in the hollow portion seems to depend on the initial bone quality of the recipient sites.

Adaptation, Psychological↗

PubMed1996

A histologic evaluation of retrieved hydroxyapatite-coated blade-form implants using scanning electron, light, and confocal laser scanning microscopies.

We histologically examined seven hydroxyapatite-coated (HA) blade implants removed from patients. Four of them radiologically showed severe bone loss and were easily removed with an elevator. Three radiologically showed vertical bone loss and were removed by surgical procedure. Our histological evaluation indicated that coating separation from the HA implants had occurred, and HA coating resorption by bone tissues was suspected in an implant left in situ for 8 years. Several multinucleated giant cells were seen with a few released particles of HA coating at the point lacking bone contact with the HA coating. The presence of microorganisms on and in the HA coating layer was also noted.

Adult↗

PubMed1996

Fractures of hydroxyapatite-coated blade implants connected with natural teeth. A histological study using SEM, light microscopy, and an image processing system.

A clinical study was conducted of 59 patients treated with 78 hydroxyapatite (HA)-coated blade implants from August 1986. Five implants in 5 patients were broken at the neck portion, and one implant in one patient was removed from the jaw bone. The histological findings around a broken implant which was removed from the mandible are presented. These sections showed good adaptation of the bone to the implant without a fibrous layer. Histomorphometric evaluation of bone-to-implant contact showed 73.5%. The scanning electron microscopy image of the fractured surface revealed a fatigue fracture. The suspected cause of the fracture was stress concentration at the cervix portion, because of excessive mobility or deleterious change of abutment teeth. Consequently, the osseointegration/biointegration implants should not be connected with natural teeth.

Aged↗

PubMed1995

High susceptibility to paraquat-driven lipid peroxidation of cultured hepatocytes loaded with linolenic acid.

Rat hepatocytes cultured without (normal cells) and with 1 mM alpha-linolenic acid-bovine serum albumin complex (alpha-linolenic acid [LNA]-loaded cells) for 12 hr were challenged with paraquat at concentrations ranging from 0.01 to 5 mM. The addition of paraquat to normal hepatocytes induced a relatively low level of lipid peroxidation as measured by the accumulation of malondialdehyde in the medium, even at a high paraquat concentration that caused severe cell injury. LNA-loaded hepatocytes markedly underwent lipid peroxidation on addition of paraquat, with a rise in the malondialdehyde accumulation beginning at the lowest concentration used (0.01 mM). The enhanced lipid peroxidation induced in LNA-loaded hepatocytes by the addition of paraquat was accompanied by the occurrence of cell injury at noncytotoxic paraquat concentrations for normal cells. Of further importance was that in LNA-loaded cells, lipid peroxidation promptly occurred after the addition of paraquat and was followed by the loss of cell viability. Addition of antioxidants such as N,N'-diphenyl-p-phenylenediamine and alpha-tocopherol with paraquat prevented lipid peroxidation in both normal and LNA-loaded hepatocytes but protected only the latter cells from cell injury. Neither lipid peroxidation nor cell injury in either group of hepatocytes was prevented by the presence of .OH scavengers such as mannitol and dimethyl sulfoxide. In addition, paraquat-driven lipid peroxidation in LNA-loaded hepatocytes was promoted by the addition of ascorbate but was rather suppressed by the addition of H2O2. In conclusion, it is likely that the addition of paraquat induced Fe(++)-lipid hydroperoxide-dependent lipid peroxidation that led to lethal cell injury in LNA-loaded hepatocytes.

Animals↗

PubMed1995

Comparative stress analyses of fixed free-end osseointegrated prostheses using the finite element method.

We investigated the designs of osseointegrated prostheses in cases of free-end partial edentulism using comparative stress analyses interpreted with the two-dimensional finite element method. Seven free-end fixed osseointegrated prosthesis models with various connection designs (i.e., rigidly connected to an abutment tooth, not connected to an abutment tooth, connected to an abutment tooth with a non-rigid attachment) were studied. The stress values of the seven models loaded with vertical force were analyzed. When the prosthesis was not connected to natural abutment tooth but was supported instead by two free-standing implant abutments, lowest levels of stress in bone were noted. On the other hand, non-rigid attachments, when incorporated into a prosthesis, did not significantly reduce the level of stress in bone.

Alveolar Process↗

PubMed1994

Alpha 1-adrenoceptors in the conduction system of rat hearts.

1. We have characterized alpha 1-adrenoceptor in the conduction systems of the rat heart by quantitative autoradiography. 2. Consecutive 20 micron thick sections from a single rat heart containing the sinoatrial (SA) node and atrioventricular (AV) node were incubated with increasing concentrations of [3H]-prazosin with or without 10 microM phentolamine. After exposure to 3H-Ultrofilm, optical densities corresponding to the SA node and AV node were determined by computerized densitometry after comparison with 3H standards. 3. The SA node and AV node were stained heavily for cholinesterase and they contained a higher concentration of alpha 1-adrenoceptors than the adjacent myocardium without a significant change in the affinity. 4. These results support the hypothesis that alpha 1-adrenoceptors may play an important role not only in inotropism but also in chronotropism of rat hearts.

Animals↗

PubMed1994

Responses of beta-adrenoceptor in rat soleus to phosphorus compound levels and/or unloading.

Responses of beta-adrenoceptor (beta-AR) in rat soleus to gravitational unloading and/or changes in the levels of phosphorus compounds by feeding either creatine or its analogue beta-guanidinopropionic acid (beta-GPA) were studied. A decrease in the density of beta-AR (about -35%) was induced by 10 days of hindlimb suspension, but the affinity of the receptor was unaffected. Suspension unloading tended to increase the levels of adenosine triphosphate and phosphocreatine and decrease inorganic phosphate. Even without unloading, the beta-AR density decreased after an oral creatine supplementation (about -20%), which also tended to elevate the high-energy phosphate levels in muscle. However, an elevation of beta-AR density was induced (about +36%) after chronic depletion of high-energy phosphates by feeding beta-GPA (about +125%). Data suggest that the density of beta-AR in muscle is elevated if the high-energy phosphate contents are chronically decreased and vice versa. However, it may not be directly related to the degree of muscle contractile activity.

Animals↗

PubMed1993

Tissue reaction to alumina implants inserted into the tibiae of rats.

We examined the tissue reaction to three alumina implants--single-crystal alumina (SA), dense polycrystal alumina (DPA), and porous polycrystal alumina (PPA)--inserted transcortically, extending into the medullary canal of rat tibiae, and assessed the quantitative differences in bone reaction using an image processing system. There was no difference in the degree of maturation of newly formed bone around the three kinds of alumina. SA and DPA were encapsulated with a continuous bone layer, but some bone tissue was attached focally around PPA. Bone trabeculae in the control site diminished in size and number chronologically. Multinucleated giant cells were observed on the surface of DPA and PPA, but not on SA. Tabulation of the quantitative evaluation indicated that SA showed the highest, DPA a lower, and PPA the lowest in bone contact rate, bone contact thickness, and bone contact area. These data suggest that SA is superior to the other two as an implant material.

Aluminum Oxide↗

PubMed1990

Two-dimensional FEM analysis of hydroxyapatite implants: diameter effects on stress distribution.

The effect of the diameter of hydroxyapatite (HAP) implants on stress distribution in alveolar bone was analyzed by two-dimensional finite element methods (FEM), with use of a 100-N vertical and lateral load. Since HAP is considered a bioactive material, the alveolar bone was assumed to be bonded directly to the HAP implant in the FEM model. The analysis showed that the stresses in cortical bone were generally higher than those in cancellous bone, and that the stress concentration occurred mainly in cortical bone around the neck of the implant with both vertical and lateral load. The stresses in cortical bone with lateral load were especially high-twice those in vertical load. Stresses in cortical bone decrease in inverse proportion to the increase in implant diameter with both vertical and lateral load. The results suggested that an implant with a large diameter is favorable from the standpoint of stress distribution.

Alveolar Process↗