抄　録：令和2年の国勢調査によると人口は1億2,614万6千人で，総人口に占める65歳以上の割合は28.6%であった．日本は，15歳未満人口の割合は世界で最も低く，65歳以上人口の割合は世界で最も高いという結果であった．高齢者は多くの疾患を有していることが多いため，診療に際しては患者の基礎疾患に注意しなくてはならない．高齢者歯科医療は，口腔機能低下への対応も求められる．高齢者の根管治療には，根管形態による困難と患者の全身状態による治癒困難などさまざまな容易でない要素がある．しかし，根管治療によって歯を保存することで口腔機能の維持につながるため，さまざまな工夫がなされてきた．近年，歯科用実体顕微鏡をはじめ歯科用コーンビームCTが取り入れられ，高齢者の狭窄した根管も正確に診断し可能なかぎり最善の処置を行えるようになってきたが，高齢者の全身状態を考慮したうえで来院回数を減らし処置時間も少なくし，非外科的治療法にて，閉鎖根管の根尖に存在する根尖病変を治癒させることは容易ではない．本稿では将来の高齢者の根管治療の可能性についてまとめた．

Abstract : Purpose : This study aimed to evaluate the effectiveness of a sonic-powered irrigation system (EDDY) used in combination with ethylene diamine tetra acetic acid (EDTA) and sodium hypochlorite (NaOCl) on smear layer removal and dentinal erosion.

 Materials and Methods : Noncarious human single-rooted teeth (n=60) were decoronated and their root canals were then prepared up to #40/.08 at a 10-mm working length. These root canals were irrigated with needles or EDDY with EDTA and NaOCl in various sequences and durations (n=5 each). The removal of the smear layer and the degree of dentinal erosion were assessed by scanning electron microscope observation. The percentage of smear layer covering the canal wall and dentin tubules was scored : score 1, smear layer almost absent ; score 2, 25% or less ; score 3, 25-50% ; score 4, 50-75% ; score 5, 75-100%. The degree of dentinal erosion was also scored : score 1, no erosion, all tubules look normal in appearance and size ; score 2, moderate erosion, the peritubular dentin is eroded ; score 3, severe erosion, the intertubular dentin is destroyed. The data were statistically analyzed by one-way ANOVA followed by a post-hoc Bonferroni test.

 Results : The canal walls were consistently cleaner in the coronal and middle thirds than in the apical third in all specimens of the syringe irrigation groups. The 60 s EDDY irrigation removed more smear layer from the canal wall in the apical third than the 30 s EDDY irrigation and the 30 and 60 s syringe irrigations. The NaOCl with 60 s EDDY followed by EDTA with 60 s EDDY irrigation showed less dentinal erosion compared to the EDTA with 60 s EDDY followed by NaOCl with 60 s EDDY irrigation.

 Conclusion : The NaOCl with 60 s EDDY followed by EDTA with 60 s EDDY irrigation is effective for smear layer removal and erosional inhibition from the root canal walls from the apical area to the coronal area.

Abstract : Purpose : Invasive cervical resorption is a complex form of absorption that can be difficult to diagnose clinically. The amount of information available in the two-dimensional evaluation by radiographic examination is limited. Moreover, not only the pathological condition but also the diagnosis of the pulp and apical periodontal tissue may significantly change the treatment planning. We report here a case in which the pathophysiology of invasive cervical resorption was accurately grasped using CBCT and the treatment was planned accordingly.

 Case : The mandibular right second molar showed a positive reaction in the electric pulp test, and the cold test showed a transient strong positive reaction, which was clearly different from the control tooth, although there was no persistent pain. Periodontal pocket testing revealed a 6-mm pocket from the distal buccal side to the furcation area of the second molar. Radiographic examination revealed a transmission image in the distal crown. The affected tooth was the right second molar of the lower jaw, the pulp was diagnosed as reversible pulpitis, and the apical periodontal tissue was diagnosed as normal apical periodontal tissue. As for the pathological condition, caries, internal resorption or external resorption was considered. Therefore, CBCT imaging was performed. From the laboratory findings, the medullary cavity and root canal structure were normal, but a resorption site was found in the cervical region, suggesting invasive cervical resorption. Aiming to achieve a better prognosis, we decided to perform root canal treatment and curettage/repair of the resorption part.

 Discussion : In this case, CBCT images showed 3Bp invasive cervical resorption according to Patel’s classification, and the spread of the pathological condition could be accurately grasped. As a result, problems could be identified accurately, which helped to determine the treatment planning, resulting in the success of this case and a better prognosis.

 Conclusion : For cases of invasive cervical resorption, performing 3D CBCT imaging to consider the location, extent, and proximity to the medullary cavity of the resorption site may assist better treatment planning.