Objective: To determine if the histopathological study is associated with the clinical-radiographic diagnosis of reversible and irreversible pulpitis, in patients from 3 to 8 years of age who come to the UEO. Methodology: Conventional clinical diagnostic methods were used for the clinical-radiographic evaluation of reversible and irreversible pulpitis; Likewise, an excisional biopsy of the pulp tissue of 41 dental organs that presented pulp pathology was performed using dentin cutting spoons. In the research laboratory of the Universidad Autónoma del Estado de México (UAEM), using light microscopy, the pulp tissue was studied by a stomatologist specialist and the histopathological diagnosis of the biopsies was established. Results: The McNemar statistical test (comparison of proportions for related samples) resulted in no statistically significan difference (p>0.05, 95 % CI) between the presumptive diagnosis and the confirmatory diagnosis. Limitations: No limitations were considered. Value: An alternative method can be used in places where all means are not available. Conclusions: The histopathological diagnosis confirmed the clinical-radiographic diagnosis in this sample, so it is suggested to use all conventional diagnostic methods to establish a more accurate diagnosis and therefore a better treatment.