Types Of Isthmus And Their Prevalence In Mandibular Incisors

Purpose: This study aimed to evaluate the types of isthmus and their prevalence in mandibular incisors using magnification systems and histochemical methods. Materials and Methods: This study included 150 randomly selected human mandibular incisors devoid of caries and free of any pathology in the crown or root portion. Samples were preserved in 10% formalin until needed. After fixation and decalcification, serial sections were placed into tissue-tracking cassettes, stained with hematoxylin and eosin, and examined under a light microscope at 40× magnification. Results: Of the 150 mandibular incisors examined, various types of isthmus were observed in 105. The most frequently observed isthmus type was Type 1, accounting for 44.8% of cases, while the least observed was Type 3, accounting for 8.6%. No isthmus was observed in 30% of the samples. Isthmuses were significantly more common at the apical 5 and 6 mm levels; however, no significant difference was observed in the types of isthmus. Conclusion: Mandibular incisors exhibit significant variations in isthmuses, indicating a complex structure. Knowledge of the possible location and variations of isthmuses is crucial as it not only influences the selection of techniques and instruments but also directly impacts treatment success. Standard instrumentation techniques alone may not suffice for thoroughly cleaning the root canal system in complex cases, such as those with isthmus variation.