Hiroshi Kato

Hokkaido University, Sapporo-shi, Hokkaido, Japan

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Publications (31)14.66 Total impact


  • No preview · Article · Jun 2006 · Journal of Periodontal Research
  • Tsutomu Sugaya · Masamitsu Kawanami · Hiroshi Kato
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    ABSTRACT: The purpose of this study was to compare an ultrasonic furcation tip with an ultrasonic conventional tip and a hand scaler on accessibility to furcation areas of mandibular first and second molars. The study was conducted on 360 artificial molars that were replicated from 30 mandibular first molars and 30 second molars with silicone impression material and resin. The furcation areas of each molar were coated with red nail colour for artificial calculus. The root areas from the cement-enamel junction apically were covered with silicone rubber simulating gingival tissue. Then the models were instrumented on the buccal or lingual aspects by an experienced operator with each of the following instruments: an ultrasonic furcation tip, an ultrasonic conventional tip and a hand scaler. After instrumentation the percentage of the furcation area with residual artificial calculus was assessed using a computerised imaging system. Results showed that when the horizontal pocket depth was less than 2mm, all three instruments showed good accessibility. When the horizontal pocket depth was more than 2mm, the ultrasonic conventional tip and the hand scaler showed less removal of artificial calculus than the ultrasonic furcation tip (P < 0.01). Efficiency of the ultrasonic furcation tip was fairly satisfactory for the horizontal pocket up to the ridge of the furcation roof.
    No preview · Article · Nov 2002 · Journal of the International Academy of Periodontology
  • Tsutomu Sugaya · Masamitsu Kawanami · Hiroshi Kato
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    ABSTRACT: The purpose of this study was to evaluate the clinical effects of closed debridement with an ultrasonic furcation tip in degree II furcation involvement of mandibular molars. Fifteen patients with degree II furcation involvement in mandibular first and/ or second molars participated in the study. All patients were given oral hygiene instruction. Plaque score, probing depth, probing attachment level and bleeding on probing were recorded at baseline, 1, 4, 8 and 12 weeks. Following a baseline examination, a single episode of supra- and subgingival debridement was provided using an ultrasonic furcation tip in the test group, and an ultrasonic conventional tip and hand scalers under local anesthesia in the control group. At baseline, the mean horizontal probing depth in the test group was 6.35 mm and in the control group 6.06 mm. These values decreased to 4.88 mm and 5.29 mm respectively after 12 weeks. There were horizontal probing attachment gains of 1.29 mm in the test group and 0.59 mm in the control group after 12 weeks (P < 0.01). The bleeding scores were 1.0 in the test group and 0.88 in control group at baseline. These scores were improved to 0.12 in the test group and 0.59 in the control group after 12 weeks (P < 0.01). The results suggest that ultrasonic debridement with a furcation tip has a significantly better potential in treating degree II furcation involvement of mandibular molars.
    No preview · Article · Nov 2002 · Journal of the International Academy of Periodontology
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    ABSTRACT: The purpose of this study was to evaluate whether hard tissue might be formed on dentin surfaces applied with recombinant human bone morphogenetic protein-2 (rhBMP-2) in palatal connective tissue. Fifty-eight dentin blocks were prepared from rat roots, demineralized with 24% EDTA (pH 7.0), applied with 0, 50 and 100 microgram/ml rhBMP-2, and labeled as groups 0, 50 and 100. The dentin blocks were then transplanted into palatal connective tissue of rats, and specimens were prepared at two and four weeks after surgery for histologic and histomorphometric examinations. The results showed that the percentage of newly formed hard tissue in relation to the total dentin block surface length in groups 0, 50 and 100 was 0.0%, 2.8% and 4.4% at two weeks, and 0.0%, 1.6% and 12.8% at four weeks, respectively. New hard tissue formation in groups 50 and 100 was significantly promoted as compared to group 0 (p < 0.01). These findings thus indicate that rhBMP-2 application to dentin enhanced new hard tissue formation on dentin surfaces in the connective tissue of the palate.
    No preview · Article · Jun 2002 · Journal of Periodontal Research
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    ABSTRACT: The purposes of this study were to develop and verify the a portable nocturnal bruxism monitoring and analysis device equipped with a microcomputer, and to clinically apply the device to know the actual conditions of bruxism patients. EEPROM was installed in the device for the data recording, and after the data collection, the recorded data was entered into a personal computer via serial port. After confirming the accuracy of the device, a total of 30 subjects were enrolled in this study to monitor their bruxism activities for 3 nights. Bruxism self-aware group consisted of 14 subjects, 7 males and 7 females, and unaware group consisted of 16 patients, 8 males and 8 females. Most of the subjects reported that the new device was easy to handle. The average bruxism time per hour and the average bruxism lasting time were 223.8 +/- 112.0 and 3.9 +/- 2.9 s in the self-aware group, and 49.3 +/- 38.3 and 0.8 +/- 0.7 s in the unaware group, respectively. The bruxism self-aware group showed statistically longer average bruxism time per hour and the average bruxism lasting time. It was confirmed that the new bruxism monitoring and analysis device is practical for clinical application to monitor and analyze the electromyographic activities.
    No preview · Article · Feb 2002 · Frontiers of Medical & Biological Engineering
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    ABSTRACT: Vertical root fractures lead to advanced periodontal breakdown with deep periodontal pockets and vertical bone defects. The purpose of this study is to evaluate clinically the periodontal healing of root fracture treatment using adhesive resin cement. In 22 patients, 23 teeth with vertical root fractures were treated with 4-META/MMA-TBB resin cement. Eleven fractured roots were bonded through the root canal (group A) and 12 fractured roots were bonded extra-orally and replanted (group B). All teeth were then restored with full cast crowns (n=20) or coping (n=3). Mean probing depth was 6.6 mm at pre-treatment and 4.4 mm 6 months after the treatment in group A, and 7.4 mm and 4.6 mm, respectively, in group B. Bleeding scores were 100% at pre-treatment and 36.4% after 6 months in group A and 91.7% and 8.3%, respectively in group B. Radiographic bone level was 56.8% at pretreatment and 59.1% after 6 months in group A, and 18.8% and 29.2%, respectively, in group B. Two roots of group A and three roots of group B were extracted due to refracture, deterioration of periodontal inflammation, mobility, and luxation. The remaining roots (n=18) presented no discomfort to the patients and there was no deterioration of periodontal conditions over a mean period of 33 months (range 14-74 months) in group A and over a mean period of 22 months (range 6-48 months) in group B. There was no ankylosed teeth nor was any root resorption detected. The results suggested that the treatment of vertical root fracture using 4-META/MMA-TBB resin has good prognostic possibilities.
    No preview · Article · Sep 2001 · Dental Traumatology
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    ABSTRACT: The purpose of the study was to evaluate periodontal healing after replantation of intentionally rotated teeth with healthy and denuded root surfaces. Ten teeth with hopeless prognoses because of extensive alveolar bone loss and deep pockets extending to the apexes only on one or two surfaces, but with a healthy periodontal apparatus on the other surfaces, were selected. A mucogingival flap was elevated and the teeth were extracted carefully so as not to damage the healthy remnant of the periodontal membrane remaining on the root surfaces. Thorough extra-oral debridement was performed on the contaminated root surface and the remnant was carefully conserved. Retrofilling was also done to eliminate an endodontic cause of attachment loss. The teeth were horizontally rotated and then replanted so that the healthy root would face the connective tissue at the initially periodontally involved sites, and the root planed surfaces, which had been periodontally involved, would face the surfaces of the alveolar sockets at initially healthy sites. The teeth were splinted with adjacent teeth. Clinical parameters and radiographic examination were performed pre-operatively, and at 3 or 6 months, 1, 2, and 3 years postoperatively. One tooth was extracted 1.5 years postoperatively due to reduced support and the treatment strategy of the patient. The other nine teeth were well maintained without any discomfort for the whole maintenance period of 3 years. In all teeth, areas that previously had no pocketing but were now against denuded root surfaces maintained the previous pocket depth readings. In areas where a deep pocket was present but now had a root surface with healthy periodontium, a distinct decrease of mean pocket depth was observed at the first reexamination 3 months postoperatively. The mean radiographic alveolar bone level increased from 0.3% to 45.3% in 2 years and was thereafter maintained for the entire observation period. Loss of periodontal space and possible root resorption were observed in only one case without other ankylotic symptoms. These results suggest that the healing without ankylosis of an extensive denuded root surface may occur by mechanisms other than the maintenance of a viable periodontal ligament on the root surface.
    No preview · Article · Jul 2001 · Dental Traumatology
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    ABSTRACT: This study aimed to evaluate quantitatively the migrated, attached, and oriented human periodontal ligament cells (HPLC) to periodontally diseased cementum and dentin after demineralization with low and neutral pH etching solution. Human teeth, extracted due to periodontal diseases, were scaled and root planed so that cementum remained on one longitudinal half of the root and dentin was exposed on the other half. Forty root slices of 200 microm thickness, obtained from the mid-third of these roots, were divided into four groups: group 1, demineralized with a saturated solution of citric acid (pH 1.20); group 2, with 24% EDTA (pH 7.04); group 3, with tetracycline HCl 100 mg/ml (pH 2.00); and group 4, only scaled and root planed (control). Root slices were placed over the confluent HPLC in 35 mm culture dishes and incubated. Phase contrast microscopic photographs of attached and oriented refractile HPLC to root surfaces were taken at days 1, 3, and 7. Quantitative analysis of attached and oriented HPLC from these photographs was done using special software. The results showed no significant difference in the attachment and orientation index of HPLC to cementum compared to dentin in any method of demineralization at each time point (P >0.05), although there was a significantly higher cell attachment and orientation index to demineralized dentin with EDTA and citric acid than to non-etched dentin and to all 3 demineralized cementum surfaces compared to non-etched cementum (P<0.05). EDTA and citric acid demineralization may enhance HPLC attachment and orientation to the root surface, and it is not always necessary to remove excessive cementum when the demineralizing procedure is used.
    No preview · Article · Aug 2000 · Journal of Periodontology
  • Ryuji Sakagami · Hiroshi Kato
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    ABSTRACT: The purposes of this study were to evaluate the geometric and densitometric reproducibility of a newly developed standardized X-ray system and to examine the radiographic changes after scaling/root planing as shown by this device. The system was comprised of three parts: an acrylic bite piece for the individual patient, an aluminum wedge-equipped holder, and a holder-connecting device. The experiment was performed at 32 sites of premolar and molar areas in 19 patients. Radiographs were retaken 6 weeks after scaling/root planing and the reproducibility and radiographic changes were examined. The vertical and horizontal geometric reproducibility of the system at 32 sites in 19 patients were 1.0% and 1.8%, respectively. Of 351 scaled sites, 39 (11.1%) exhibited bone regeneration, and 6 (1.7%) exhibited bone loss. These results indicate that the newly developed system has high accuracy and clinical usefulness. Early bone remodeling can be observed radiographically after 6 weeks with our standardized X-ray system.
    No preview · Article · May 2000 · Oral Radiology
  • Hideshi Yabuta · Ryuji Sakagami · Hiroshi Kato

    No preview · Article · Jan 2000 · Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology)

  • No preview · Article · Jan 2000 · Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology)
  • Ryuji Sakagami · Tomoomi Odajima · Hiroshi Kato
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    ABSTRACT: 「付着歯肉の獲得を目的とした低侵襲歯肉結合組織移植術」を考案し, その臨床応用を試みた。新たに開発した手術器材は3種類で (1) 14ゲージ吸上針の先端をシャープニングした歯肉採取器, (2) 小型ディスポーザブルメスに, 把持用のプラスチック板を取り付けた移植片切断用メス, (3) 18ゲージの注射針を改造した移植. 床形成剥離子である。術式は, (1) まず供給側の口蓋部に歯肉採取器を回転しながら10mm程度押し進め, (2) 次に移植片切断用メスを口蓋歯肉に刺入して歯肉採取器の中に入った結合組織を周囲の組織から離断する。 (3) さらに受容側の歯肉歯槽粘膜境にメスで小切開を加えた後, そこから移植床形成剥離子を骨膜上に挿入して, 歯肉歯槽粘膜境に並行にトンネル状の移植床を形成し, (4) 採取した移植片を小型ピンセットを用いて挿入し, 小切開部を縫合する。本術式を臨床応用した症例では,(1) 術中と術後の出血や, 患者の疼痛はわずかで, 創傷の治癒も早く, 外科的な侵襲はきわめて少なかった。(2) 手術は短時間で終わり, 手技も簡単であった。(3) 新術式は付着歯肉と角化歯肉を獲得できた。 付着歯肉は術後2週で観察されたが, 上皮の角化は初期には起こらず術後6週頃から観察され始め, 1年後には角化が明確になったことから, 上皮の角化充進には時間が必要であった。以上より, 従来の上皮下結合組織移植術等の歯肉歯槽粘膜手術に比較して, 新術式は低侵襲で付着歯肉と角化歯肉をともに作製できる有効な手術方法であることが示唆された。
    No preview · Article · Jan 2000 · Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology)
  • Kiyoshi Kimura · Tsutomu Sugaya · Hiroshi Kato

    No preview · Article · Jan 2000 · Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology)
  • Hirofumi Miyaji · Tsutomu Sugaya · Hiroshi Kato

    No preview · Article · Jan 2000 · Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology)
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    ABSTRACT: 本研究は, 坂上らが考案した「付着歯肉の獲得を目的とした低侵襲歯肉結合組織移植術」の治癒過程と組織学的変化を明らかにする目的で行った。実験動物には健康な成ネコ (雑種) 10頭を用い, 実験部位には下顎犬歯と第三前臼歯の唇・頬側歯槽 (可動) 粘膜部を用いた。角化歯肉と付着歯肉をあらかじめ除去した実験部位に, 坂上らの歯肉結合組織移植術を行った。なお, 本研究では, 坂上らの用いた移植片と異なり移植片から上皮組織を取り除くのが困難であったため, 上皮を含んだままの移植片を用いた。観察期間は2日, 1, 4, 6, 8週とし, 臨床的および病理組織学的に観察した。臨床的観察では, 術後感染, 粘膜の壊死, 移植片の脱落などはなく, 治癒経過は良好で, 術後の体重減少もなく実験動物に与えたストレスは極めて小さいと思われた。臨床的付着歯肉の幅は, 術後2週には移植部位に一致して増加し, 観察期間終了まで維持された。病理組織学的観察では, 移植組織は密な結合組織線維に富んだ口蓋歯肉の組織学的特徴を維持し, 経時的に歯槽骨骨膜と結合が強固になるのが観察された。移植組織に含まれていた上皮は, 消失することなく経時的に増殖し角質の落屑などを起こした。以上の結果より, 坂上らが考案した歯肉結合組織移植術は, 低侵襲で付着歯肉の獲得に有効であることが示唆された。なお, 移植組織中の上皮は増殖するので, 上皮を取り除いて移植する必要があると思われた。
    No preview · Article · Jan 2000 · Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology)
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    ABSTRACT: 急速な歯周組織破壊につながると考えられる歯周炎急性症状 (急性歯周膿瘍) に対する, 塩酸ミノサイクリン歯科用軟膏の歯周ポケット内局所投与の効果について, 対照群と比較した臨床的, 細菌学的な評価を行った。被験者は, 口腔内の単一部位において急性歯周膿瘍を有し処置が必要な患者100名を対象とした。被験者の急性歯周膿瘍を示すポケットに2%塩酸ミノサイクリン歯科用軟膏を1回投与し, 0日目 (処置前), 3日目および7日目に臨床診査を行った。0日目および7日目においては, 細菌サンプルの採取も行った。被験者に対し, 基本処置群 (C群: ポケット内洗浄処置のみ) と試験薬剤群 (T群: ポケット内洗浄処置+2%塩酸ミノサイクリン歯科用軟膏ポケット内注入) の2群を, 盲験的な方法で比較した。本研究を行うに当たり, 医薬品の臨床試験の実施に関する基準 (GCP) を遵守した。術前術後において両群とも痛み等の臨床症状の改善が認められたが, T群の方がC群と比べ, より高い改善が見られた。プロービング深さや, アタッチメントレベルの変化に関してもT群の方が, 高い改善が見られた。歯肉縁下プラーク細菌の総菌数に対しては, 両群とも減少したが, T群の方がより大きな減少が見られた。歯周病原性細菌の検出率に関しては, T群のみ, B. forsythus, P. gingivalis, T. denticolaの減少がみられた。T群は臨床的にも細菌学的にもC群以上に改善がみられた。以上の結果から, 塩酸ミノサイクリン歯科用軟膏は急性歯周膿瘍の改善に有効であることが示された。
    No preview · Article · Jan 1999 · Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology)
  • Tomoomi Odajima · Okito Hongo · Hiroshi Kato
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    ABSTRACT: 本研究は, rhBMP-2を, 担体にポリ乳酸グリコール酸共重合体/ゼラチンスポンジ複合体 (PGS) を用いてルートプレーニングした根面に移植した場合のセメント質, 歯根膜, 歯槽骨の誘導再生, および歯根吸収と骨性癒着の発現の危険性を検討する目的で, イヌに開窓状歯槽骨欠損 (5×5mm) を作製し骨欠損周囲のセメント質と歯根膜に電気メスを用いて損傷を与えた後, 対照群には担体のみを移植し, 実験群にはrhBMP-2を配合比率0.4μg/mm3で移植し, 病理組織学的観察と組織学的計測を行つた。観察期間は13~16週とした。対照群では術後4週に2部位に炎症を伴う腫脹が生じたが, 実験群は観察期間終了時まで良好であった。骨の再生率は, 実験群約97%, 対照群約81%で統計学的有意差 (p<0.05) がみられ, 骨が再生した部位には歯根膜様軟組織が生じていた。一方, セメント質の再生率は約54%と約44%で統計学的有意差はみられなかった。歯根吸収は表面吸収型のみが観察され, 歯根吸収率は実験群約29%, 対照群約'41%であった。骨性癒着は両群ともに観察されなかった。以上の結果から担体にPGSを用いてrhBMP-2を根面に移植すると, 担体のみの移植に比べ歯槽骨と歯根膜様軟組織の再生は明らかに多くなり, セメント質の再生も多くなる傾向を示し, 骨性癒着は生じないことが示唆された。
    No preview · Article · Jan 1999 · Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology)
  • Takehito Okumura · Tsutomu Sugaya · Hiroshi Kato

    No preview · Article · Jan 1998 · Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology)
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    ABSTRACT: The purpose of this study was to investigate the proliferation and mineralization activity of the human gingival and periodontal ligament cells in relation to the nature of the dentin surface. Three types of bovine dentin blocks were used: 1) Rp group: dentin block was root planed by hand scaler, 2) CA group : dentin block was treated by citric acid pH 1 for 3 mins and 3) Na group : citric acid treated block was further exposed to 10% Na0Cl for 3 mins. Besides this, hydroxyapatite (HA) blocks were taken as 4 th group. Human gingival cells (HGC) and periodontal ligament cells (HPLC) were seeded on the blocks and cultured. Alkaline phosphatase (ALP) activity and protein concentration of the attached cells on blocks were measured at the 1, 3, 5, 7, 10 and 14 days interval. Furthermore, HGC and HPLC were cultured in DMEM and the blocks were kept on the cell sheet after becoming confluent, media was changed to a-MEM supplemented with 100 nM dexamethasone and 10 mM β-glycerophosphate. Mineralized nodules were stained weekly for 3 weeks by von-Kossa method and the area was measured in relation to the margin of blocks.The results of the protein concentration of the HGC was higher than the HPLC in the 4 groups. Among the 4 groups, protein concentration of HPLC increased at a faster rate in CA group and in HGC, protein concentration increased at a slower rate in Na group. HGC expressed very low ALP activity and was significantly lower than the HPLC. HPLC showed the highest activity in relation to CA group, and lowest activity was observed in relation to Na and HA group. Regarding the mineralized nodule; HPLC formed larger area of nodule than HGC. CA group formed the largest area of nodule in HPLC but there was no difference among the 4 groups in the HGC. The results suggest that the nature of the dentin surface could influence the cellular proliferation and mineralization activity of HPLC, and also the proliferation of HGC. As HGC are able to show mineralization activity in this study though it is very low, it can be suggested that HGC have the potentiality to torm calcitied tissue.
    No preview · Article · Jan 1998 · Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology)
  • Akira Ninomiya · Tomotoshi Iwanami · Hiroshi Kato

    No preview · Article · Jan 1998 · Nihon Shishubyo Gakkai Kaishi (Journal of the Japanese Society of Periodontology)