Pulpitis is successfully treated and has long ceased to be frightening for a practicing veterinary specialist. Three-channel pulpitis, subject to endodontic treatment, is common and has some treatment features. For treatment, it is required to process all three channels, following a certain algorithm. The process takes a long time, requires accuracy and precision. It is important to follow the main stages of endodontic treatment and take into account the anatomical features of the maxillary P4 of the dog. This is the only premolar in dogs that has 3 roots. According to the international system, Triadan has numbers 108 and 208. (*A modified Triadan system provides a consistent method of numbering teeth across animal species. The system is based on the occlusion of the permanent teeth of the pig (11 teeth in each quadrant - three incisors, one canine, four premolars and three molars. A total of 44 teeth). Tooth after Endodontic treatment does not become «dead», it can last a lifetime. Endodontic treatment is becoming an advanced trend in modern dentistry. It requires a doctor's vast experience and intuition, patience and accuracy, possession of a variety of high-tech diagnostic and treatment methods. Endodontic treatment is the most effective method of eliminating pulpitis.