Abstract : The purpose of this study was to examine the efficacy of essential oils, which are used in aromatherapy, for root canal treatment. Enterococcus faecalis frequently detected in intractable infected root canals was used as an experimental bacterium. Seven types of essential oils were tested : clove, myrrh, Indian sandalwood, patchouli, cedarwood (atlas), juniper and West Indian lemongrass. The antibacterial effect of each essential oil was evaluated by measuring minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC).

 The lowest MIC was that of myrrh, followed by clove and patchouli, and the highest was that of cedarwood. Regarding MBC, clove was the lowest, followed by West Indian lemongrass. Myrrh, Indian sandalwood and cedarwood could not be observed.

 Comprehensively considering MIC and MBC values for Enterococcus faecalis, clove oil, which has long been used in dental practice, is considered to be effective. However, all the experimental essential oils demonstrated antimicrobial effects against Enterococcus faecalis, suggesting their usefulness as root canal medicaments in clinical applications. Myrrh is also effective for single-visit treatment.

Abstract : Purpose : The objective of this study was to determine the influence of the autoclave on the effect of controlled memory files of a martensite (M) Ni-Ti rotary file (NiTi-RF) and austenite (A) NiTi-RF.

 Methods : Two types of NiTi-RFs were selected : M-NiTi-RF (Hyflex EDM One File, n=10) and A-NiTi-RF (ProTaper Universal F2, n=10). Each file was prepared in a simulated artificial root canal. Pre-preparation, post-preparation and post-autoclave images of each file were recorded. Assessment of deformation of the files and their subsequent shape recovery was carried out visually and by comparing the digital images. The data was analyzed using Student's t-tests.

 Results : Visual assessment of files post-preparation revealed that M-NiTi-RF caused more ductile deformation than A-NiTi-RF. As a result of the measurement after autoclaving, M-NiTi-RF was unwound in shape more than A-NiTi-RF due to the shape memory effect.

 Conclusion : Post-preparation files became deformed as a result of use. However, M-NiTi-RF recovered in shape following autoclaving.

抄 録 : 近年, 医療分野での実物大臓器立体モデル (3Dモデル) の活用が進む. 3Dモデルは視覚・触覚による確認が可能であり, PCディスプレイ上の表示と比較して構造物の立体的な位置関係の把握が容易である. 今日では患者説明, 術前治療計画立案, 手術シミュレーション, 教育など幅広い用途に利用されている. これまでわれわれは, CT撮影データから3Dモデルを安価かつ迅速に造形する環境を整備し, 日常歯科臨床でのさまざまな3Dモデルの応用効果について報告してきた. 今回, 舌側に転位した下顎第二小臼歯を移植歯として利用するにあたり術前治療計画および手術シミュレーションに3Dモデルを利用し, 施術においては移植窩の形成にトレフィンバーが有用であった歯牙移植症例を経験したので報告する.

 症例 : 患者は47歳の女性. 舌側に転位する下顎左側第二小臼歯 (＃35歯) の対側第一大臼歯部 (＃46部) の欠損部への移植治療依頼で東京歯科大学千葉病院保存科に紹介来院した. 所定の診査診断を経て, 口内法X線画像検査およびMDCT撮影を行った. 治療では, ＃35歯の抜去に加え, ＃46部の移植窩の形成が必要となるため, 歯内療法医および口腔外科医により歯牙移植術の適否について検討することを目的に＃35歯, ＃46部を含む歯・顎骨3Dモデルを作製した. 歯・顎骨3DモデルはMDCT画像データから構築した3D CADデータおよび熱溶解積層方式デスクトップ3Dプリンタを使用し用途別に複数個の作製を行った. その結果, ＃35歯の形態に有意な異状は認めず, また＃46部は移植を行うにあたり十分な骨幅, 骨高径を有し, 施術に伴う下顎管の損傷リスクは低いと考えた. 移植する＃35歯は補綴学的に長期保存が困難とされる歯冠歯根比となることが予想されたため, 通法より長い固定期間を設定することを計画した. 3Dモデルの観察と手術シミュレーションとを踏まえ, 歯牙移植術が適応可能である旨を患者に説明, 同意を得た. 手術はまず＃35歯を抜去し, 3Dモデルシミュレーションを参考に, トレフィンバーを用いて予定した形態の移植窩を形成した. 同時にチェアサイドで＃35歯歯根を施術設計時に策定した長さで切断し, ただちに移植窩への試適を行った. 移植窩に骨切削追加の必要はなく, 施術設計の位置に植立することが可能であった. 移植後, 接着性レジンメントを用い隣在歯と暫間固定を行った. 施術後, 不快症状の訴えは軽微で臨床経過は良好であった. 術後, 移植した＃35歯の生活反応が認められたため当初予定していた＃35歯の根管治療は延期とした. 術後3カ月で暫間固定を除去, 咬合面のコンポジットレジン修復を行った. 術後のリコールにおいて移植歯は咬合時痛などの不快症状なく咀嚼機能を営み, 歯周ポケットは全周3mm以下で病的動揺も認められなかった. 術後18カ月経過後も歯髄の生活反応が認められている. X線画像検査上も歯根および周囲骨領域に有意な所見は認めないことから, 術後臨床経過は良好と判断した.

 考察 : 歯牙移植術において3Dモデルの利用は, 施術の確実性向上および予知性向上に大いに寄与したと考える. 特に移植歯の形態把握とそれに適合する移植窩形成の設計にはきわめて有用であった. 施術にあたっては, 移植歯の切断部の面積を広めに確保することを心がけたことに加え, トレフィンバーの使用により窩底周囲の血流が得られたことが歯髄の生活反応を持続させたと推測した. 渉猟しうるかぎり, 本症例のように歯牙移植に3Dモデルを活用した報告はきわめて少ない. 今回用いたデスクトップ3Dプリンタは造形コストが低いため用途に応じて任意の形状の3Dモデルを複数個造形することが容易であり, 経済性の観点からも享受できる利点は大きいと考える. また本3Dプリンタの造形分解能を鑑み, 本手術で要求される寸法精度はCTの空間分解能とほぼ同程度であることからは臨床応用上は必要十分であると考えた.

 結論 : 複数の術者が協同する治療において, 各種の画像に加え3Dモデルの活用は術者間の共通理解の確立に貢献すると考えられた. 転位歯を用いた歯牙移植症例を通じて, デスクトップ3Dプリンタで造形した3Dモデルは移植歯の形態や周囲解剖学的構造の立体的な把握, 診断と処置方針立案, 治療シミュレーションならびに患者のインフォームドコンセントでの有用なツールとして活用できることを経験した.

Abstract : In contrast to deciduous teeth, root resorption does not normally occur in permanent teeth. However, it may be triggered by damage to the precementum on the surface of the root, causing inflammatory external root resorption. We investigated whether a patient with trauma-induced external root resorption of the maxillary lateral incisor could be successfully treated by performing endodontic micro-surgery. A 34-year-old man had undergone pulp extirpation after traumatic injury when he was young. Apical periodontitis and inflammatory external root resorption subsequently developed, and apicoectomy of the maxillary left lateral incisor was performed under surgical microscopy. The lesion and granulation tissue were removed completely, and the malacic tooth substance at the resorption site was mechanically removed. Retrograde cavity preparation was conducted, and the cavity and resorption site were filled with MTA cement. Two years post-treatment, the patient had no clinical symptoms and X-rays showed scar healing at the site of the resorption-induced bone defect. Surgical removal of the granulation tissue at the resorption site, mechanical removal of the tooth substance, and filling with a highly biocompatible cement stopped the progress of resorption and successfully saved the tooth. This case suggests that endodontic micro-surgery may be a useful treatment method for inflammatory external root resorption.

Abstract : When treating a mandibular first premolar, an important point to consider is the potential existence of two root canals. Double root canals appear at a rate of about 20%. Clinicians should take care to avoid ledge formation due to a fracture caused by the tip of the file biting into a severely curved root canal or excessive rotational torque. Ledge formation can prevent cleaning to the root apex. Since the root canal diverges at the center of the root and the lingual root canal branches from the buccal root canal at an angle close to vertical, it may be difficult to prepare an inverted Y-shaped root canal (h type) (Vertucci classification V) and to clearly indicate the root canal orifice.

 Accurate access cavity preparation is needed when performing root canal treatment. If the presence of a lingual canal is suspected, the lingual cavity can be approached by extending access cavity preparation to the area near the buccal cusp. Of course, clinicians must take care to prevent overcutting and must complete root canal preparation without deviating from the original anatomy of the root canal.

 This case report describes the diagnosis, treatment, and evaluation of prognosis in a case involving the treatment of an inverted Y-shaped (h type) root canal.