This is a Pilot Phase III single-blind randomized controlled clinical trial in patients, aged 18 years and older, presenting with symptoms of apical periodontitis. The overall goal is to assess whether 2% Chlorhexidine (CHX) is superior to Calcium Hydroxide in reducing interappointment pain.

This is a Pilot Phase III single-blind randomized controlled clinical trial in patients, aged 18 years and older, presenting with symptoms of apical periodontitis. Patients will be treated with one of two current clinically-used medications, 2% chlorohexidine (intervention) vs. calcium hydroxide (standard-of-care). One week following treatment (+/- 2 days), patients will return for reevaltuion of apical periodontitis symptoms, via patient's pain perception after a bite test.

The primary objective of the proposed study is to determine if there is a difference in 7-day (+/- 2) post-procedure apical periodontitis following randomization to either 2% chlorohexidine vs. calcium hydroxide paste among patients presenting with symptoms of apical periodontitis. Additionally, the investigators will assess the number of adverse events that occur in each treatment group to determine if there appears to be a difference across groups, descriptively.

Inclusion Criteria:

• 18 years and older
• symptomatic apical periodontitis (positive to the bite test)
• restorable tooth
• requires root canal therapy
• able to undergo informed consent process
• must be English or Spanish speaker

Exclusion Criteria:

• Cracked tooth
• non-restorable tooth
• no pain medication or antibiotic taken in the past 3 days

Participant will be unaware as to which medication is used in the treatment procedure and will also be self-reporting outcomes.