Objective: Describe the cryoanesthetic effect of the use of dry ice (solid Carbon Dioxide) spray in patients with Irreversible Pulpitis (IP) undergoing conventional endodontic treatment in lower molars. Materials and Methods:This are an-in vivo quasi-experimental study with a convenience sample of 126 patients who met the criteria for selection.The clinical history was completed, obtaining socio-demographic characteristics, including the diagnosis of IP.After previously signing informed consent, patients were anesthetized applying the inferior alveolar anesthetic technique; after a period of five minutes, molars were completely isolated, then dry ice spray was applied for two seconds.Subsequently, a conventional access cavity was opened, applying intrapulpal anesthesia upon pulp exposure.For the purpose of measuring the pain experienced by the patients during access cavity opening and instrumentation procedures, the Heft-Parker modified visual analog scale (HPVAS) was used.Results: 60% of the subjects (sample) were female, the average age range was between 53 and 63 years.The tooth most frequently affected by IP was 46.According to HPVAS, 94.4% of patients reported feeling no pain, gender had no influence on the outcome of HPVAS.Based on the odds ratio related to Chi2 at older age, there is a 1.6% probability of success per year.Age showed a P value of less than 0.05.The relation between gender and the affected tooth did not show a statistically significant difference. Conclusion:Cryoanesthesia was successful as a supplementary aid to mandibular anesthesia in the endodontic treatment of lower molars.