The mice were randomly divided into three groups (7 mice per group): 1) the control group, which received only intraperitoneal injection of normal saline with TMJ injection of incomplete Freund's adjuvant (IFA; Chondrex, Redmond, WA, USA); 2) the CFA group, which received intraperitoneal injection of normal saline with TMJ injection of complete Freund's adjuvant (CFA, 5 mg/mL; Chondrex, Redmond, WA, USA); 3) the infliximab group, which received intraperitoneal injection of infliximab (10 mg/kg, dissolved in normal saline) with TMJ injection of CFA.
All mice were briefly anesthetized with 2% isoflurane and bilaterally injected using a 30-gauge needle fitted to a 10 µL Hamilton syringe. To easily identify and palpate the TMJ area, local hairs around the TMJ were trimmed with scissors. After carefully palpating the locally trimmed area considered to be the TMJ, a 30-gauge needle was inserted through the facial skin. The needle was carefully advanced superoanteriorly until the tip of the needle reached the zygomatic arch. Then the needle was slowly moved more inferiorly until it passed under the edge of the arch and ultimately entered into the joint space. Once the needle was located in the joint space, 10 µL of CFA or IFA was injected slowly over a period of 5 sec. Injections were given into both TMJs to minimize the fluctuation in the changes in BF. To evaluate the effect of TNF-alpha neutralizing drug, the infliximab group received a single intraperitoneal injection of infliximab. The control and CFA groups received intraperitoneal injection of the same volume of normal saline on the same day as the infliximab group. Intraperitoneal injection was administered immediately after local TMJ injection was given, and then it was administered daily for 13 days. BF was measured at day 0 (baseline bite force). After measuring the baseline BF, CFA or IFA was injected into both TMJs and then changes in BF were measured at days 1, 3, 5, 7, 9, and 13 after TMJ injection. All measurements were performed by one examiner who was blinded to the study groups.
All mice were briefly anesthetized with 2% isoflurane and bilaterally injected using a 30-gauge needle fitted to a 10 µL Hamilton syringe. To easily identify and palpate the TMJ area, local hairs around the TMJ were trimmed with scissors. After carefully palpating the locally trimmed area considered to be the TMJ, a 30-gauge needle was inserted through the facial skin. The needle was carefully advanced superoanteriorly until the tip of the needle reached the zygomatic arch. Then the needle was slowly moved more inferiorly until it passed under the edge of the arch and ultimately entered into the joint space. Once the needle was located in the joint space, 10 µL of CFA or IFA was injected slowly over a period of 5 sec. Injections were given into both TMJs to minimize the fluctuation in the changes in BF. To evaluate the effect of TNF-alpha neutralizing drug, the infliximab group received a single intraperitoneal injection of infliximab. The control and CFA groups received intraperitoneal injection of the same volume of normal saline on the same day as the infliximab group. Intraperitoneal injection was administered immediately after local TMJ injection was given, and then it was administered daily for 13 days. BF was measured at day 0 (baseline bite force). After measuring the baseline BF, CFA or IFA was injected into both TMJs and then changes in BF were measured at days 1, 3, 5, 7, 9, and 13 after TMJ injection. All measurements were performed by one examiner who was blinded to the study groups.
