<prompt> Kim et al classification system deals withApical constrictionApical foramenIsthmusNo. of canals  <response>: Kim et al classification of isthmusClassification of the isthmus : by Hus Kim et alType I - Is two or three canals with no notable communication.Type II - Is two canals that possess a definite connection between the two main canals.Type III - Is three canals that possess a definite connection between them.Type IV- Is when the canals extend into the isthmus area.Type V- Is the true connection or corridor throughout the section. 