The aim of the study is to assess the efficacy of cryotherapy application on the success of inferior alveolar nerve block (IANB) in reducing pain during pulp therapy of the mandibular first permanent molars with irreversible pulpitis (IP) in children age from 7 to 16 years. The null hypothesis (H0) supposed no difference in pain intensity during pulp therapy of primary molars with IP anesthetized with IANB with and without cryotherapy application. The secondary aim was to evaluate the children's behavior before and after pulpectomy in the two groups.

Inclusion Criteria:

• Healthy children aged 9-17 years who were categorized as class I or II according to the ASA classification.
• Cooperative children (rate 3 or 4 according to Frankl behavior rating scale)
• Presence of a vital mandibular first permanent molar with SIP, the tooth should show deep caries or dental restorations with a history of spontaneous lingered pain precipitated by thermal stimuli. To confirm the diagnosis of irreversible pulpitis, early response to electric pulp and thermal testing was performed.
• No radiographic changes with at least two-thirds of the root must be evident.

Exclusion Criteria:

• Children with severe emotional, intellectual, and behavioral difficulties.
• Necrotic pulp of primary molars.
• Unrestorable crowns
• Positive history of gingival swelling, abnormal mobility, and fistulous tract.
• Presence of radiographic signs of periapical and/or furcation radiolucency, and pathological resorption.