抄 録：痛みは，最も重要な医療課題の一つである．歯内治療においても，患者の痛みの解決のために医療者たちは日々取り組んでいる．痛みとは組織損傷を知らせる大切な感覚であり，その部位の何かしらの病変を示す．しかし幻肢痛やがんの痛み，帯状疱疹後神経痛などの痛みは，従来の解釈では説明ができなかった．その後，痛みの研究が進み，末梢組織の病変による「侵害受容性疼痛（Nociceptive Pain）」と，脊髄やさらに上位中枢での神経伝達の変調による「神経障害性疼痛（Neuropathic Pain）」に分類された．さらに近年，第3の痛みとして「痛覚変調性疼痛（Nociplastic Pain）」が提唱され，痛みはこの3要素で形作られていると現在は考えられている．

 口腔領域の痛みは，国際口腔顔面痛分類に準拠して整理されている．遷延する歯の痛みは，歯原性の痛みと筋筋膜痛や神経障害性疼痛など非歯原性歯痛が混在する症例が多い．したがって，根管治療の際に非歯原性歯痛の要素があれば並行して治療することが望ましい．

 診断や治療が適切でも，慢性化する症例も少なくない．痛みの定義を換言すれば「感覚的・情動的不快感」であり，単純な感覚的な要素だけではないことが示される．そのため，痛みを訴える「患者」の傾向を捉えることも重要である．この場合は，気分障害，発達障害，パーソナリティ障害などの心身医学的疾患群などが挙げられる．対人交流も重要になる．このような慢性疼痛患者に対して，動機付け面接（Motivational Interview）と共同意思決定（Shared Decision Making）の技術を用いて，良好な関係を構築して対処することが重要である．

抄 録：近年では，根管洗浄による化学的清掃の重要性が再評価されている．特に，Er：YAGレーザーを用いた洗浄液の攪拌法が物理学的および組織学的観点から注目されている．本稿では，Er：YAGレーザーにより発生するキャビテーションの物理的機序，これまでの研究報告，臨床応用の実際，および今後の展望について考察する．

Abstract : Introduction : Mineral trioxide aggregate (MTA) is considered effective for retrograde root canal filling, but in Japan, its use for this purpose is considered off-label under the Act on Securing Quality, Efficacy and Safety of Products Including Pharmaceuticals and Medical Devices. We are conducting a specified clinical trial using resin-modified MTA as a retrograde root canal filling material. We report on one case from this research.

 Case overview : Patient ; 22-year-old female. Diagnosis ; Chronic apical periodontitis and radicular cyst of the maxillary right lateral incisor. Symptoms ; History of spontaneous pain and palatal gingival swelling. X-ray imaging findings ; A radiolucent area 10 mm in diameter was observed at the apical region.

 Course of treatment : 1. Root canal treatment was performed over several times. 2. Following root canal filling, a radiolucent area remaining at the apical region was observed, so apicoectomy was performed. 3. Resin-modified MTA was used for retrograde root canal filling. 4. The postoperative course was good for over 20 months.

 Discussion : In Japan, the application of MTA cement for retrograde root canal filling constitutes off-label use. Therefore, we are evaluating the efficacy of MTA cement in retrograde root canal filling as a specified clinical trial. We hope this research will contribute to the evidence demonstrating that retrograde root canal filling with MTA is a safe and effective treatment method.

 Conclusion : This case, using resin-modified MTA as a retrograde root canal filling material, demonstrated a favorable long-term outcome over 20 months postoperatively.

Abstract : This report describes the application of a surgical template to guide osteotomy in a mandibular molar with a thick buccal bone plate. Anatomic difficulties such as a thick buccal cortical bone on the mandible raise the difficulty of endodontic surgery. The buccal cortical bone in this case was intact and thick, which made it difficult to locate the root apex. In this case, a surgical template was applied for guided osteotomy and precise apex targeting. Surgical templates are particularly helpful in difficult cases involving teeth near potentially problematic anatomic structures. Structures such as adjacent root tips, the inferior alveolar nerve, the mental foramen, and the maxillary sinus contribute to difficulty in surgical approaches to the root apex. A computer-aided surgical template may broaden the indications for endodontic microsurgery.

Abstract : Purpose : External cervical resorption (ECR) represents a challenging condition in endodontics, for which therapeutic options are limited and no standardized treatment protocol has been established. In asymptomatic cases, clinical monitoring is often selected ; however, long-term three-dimensional observations of severe ECR using cone-beam computed tomography (CBCT) are scarce. In particular, dynamic changes involving hard tissue formation within the root canal space have rarely been documented.

 Case : This report describes the case of a female patient with bilateral maxillary central incisors affected by palatal ECR. Both teeth had previously undergone root canal treatment and exhibited normal periapical tissues. Initial CBCT images revealed extensive cervical dentin loss and a peculiar finding suggestive of alveolar bone extending into the root canal space. Due to the unfavorable prognosis, extraction was initially recommended. However, following orthodontic consultation, non-extraction orthodontic treatment with intentional extrusion was performed to reposition the resorptive defects supragingivally. Subsequently, repeated local repair procedures using mineral trioxide aggregate (MTA) and composite resin were carried out without retreatment of the root canals. Serial CBCT examinations over more than 10 years demonstrated progressive dentin resorption, changes in the extent and morphology of the intraradicular hard tissue, and eventual disappearance of the bone-like tissue initially observed within the root canal. Despite intermittent complications in one incisor, both teeth remained functional and clinically stable at the final follow-up.

 Discussion : The intraradicular hard tissue observed in this case was most likely derived from alveolar bone entering through the cervical resorptive defect rather than through the apical foramen. The findings suggest that, under conditions with minimal bacterial involvement, periodontal or bone-derived cells may proliferate into available spaces within the tooth. The radiographic appearance partially resembled replacement resorption ; however, the teeth remained orthodontically movable, indicating that true ankylosis was not initially established. The subsequent changes observed over time highlight the dynamic and heterogeneous nature of ECR and underscore the limitations of current classification systems in explaining such atypical presentations.

 Conclusion : This case demonstrates that, under carefully controlled conditions and with CBCT-based longitudinal assessment, long-term preservation of teeth affected by severe ECR may be achievable. ECR should be regarded as a dynamic pathological process requiring individualized, staged interventions rather than a single definitive treatment.