Reconsideration of the So-Called "Someya's Sinew String": An Anatomical Structure or a Postoperative Scar?

The so-called Someya's sinew string is a linear structure observed in the buccal mucosa distal to the mandibular second molar and is primarily recognized in Japanese prosthodontic practice. Although previous studies have described its prevalence and clinical importance, particularly during impression procedures for removable prostheses, its anatomical basis remains unclear, and it is not formally defined in standard anatomical terminology. This study reviews the existing literature and reexamines the nature of this structure from anatomical and surgical perspectives. Based on clinical observations and previously reported findings, we propose that Someya's sinew string may represent postoperative scar tissue following mandibular third molar extraction rather than a distinct anatomical entity. Its location, linear morphology, low prevalence, and frequent asymmetry support this interpretation. Additionally, none of the cases observed in our experience exhibited intact mandibular third molars. Although this hypothesis remains unverified, it provides a coherent explanation consistent with current clinical and structural observations. Importantly, regardless of its origin, this structure remains clinically relevant and should be recognized in prosthodontic practice, particularly during impression procedures. Further studies, including histological and imaging analyses, are warranted to clarify its biological nature.