<prompt> Kims classification type IV:Incomplete isthmus between two canalsWell defined complete isthmus between two canals3 or more canals with complete or incomplete isthmus3 or more canals without any visible connections  <response>: Kim et al ClassificationRoot Apex cross-sectionNarrow ribbon-shaped connection that contains pulp or pulpally derived tissue : ISTHMUSAccording to Kim et al classification; there are 5 types:Type I : Incomplete isthmus between 2 canals.Type II : Well defined, complete isthmus between 2 canals.Type III : Very short but complete isthmus between 2 canals.Type IV : 3 or more canals with the complete or incomplete isthmus.Type V : 3 or more canals without any visible connection. 