Effect of Intracanal Cryotherapy on Pain, Anxiety, and Salivary Irisin After Root Canal Treatment

Some people feel pain after a root canal treatment. This study will test whether intracanal cryotherapy, a final rinse of the tooth with cold sterile saline, can reduce this pain compared with a room-temperature rinse. Previous studies have suggested that intracanal cryotherapy may reduce pain after root canal treatment. This study will examine the effect of cryotherapy in a defined group of patients and explore how cryotherapy works. The investigators will measure the level of irisin, a substance with reported anti-inflammatory properties, in saliva to see whether cryotherapy changes the irisin level. The study will also look at whether a person\'s tendency to worry about pain (pain catastrophizing) changes the effect of cryotherapy on pain, and whether dental anxiety is related to pain after treatment. Adults aged 18 to 65 who need root canal treatment on a single-rooted lower premolar tooth will receive standard single-visit treatment. By chance, 100 participants will be placed in a cold-saline group or a room-temperature-saline group. Thirty healthy volunteers will give one saliva sample for comparison. Participants will complete questionnaires before treatment, rate pain over the 7 days after treatment, and give saliva samples for irisin measurement. The main questions this study aims to answer are: Does intracanal cryotherapy lower pain after root canal treatment? Does intracanal cryotherapy change salivary irisin levels? Does pain catastrophizing change the effect of cryotherapy on pain? Is dental anxiety related to pain after treatment?