This study quantitatively assessed injection pressure, pain, and anxiety at the start of injection of a local anesthetic into the oral mucosa, and confirmed the relationship between injection pressure and pain, as well as between injection pressure and anxiety. Twenty-eight healthy men were selected as subjects and a 0.5-inch (12 mm) 30-gauge disposable needle attached to a computer-controlled local anesthetic delivery system (the Wand) was used. A 0.5 mL volume of local anesthetic solution was injected submucosally at a speed of either 30 or 160 s/mL. Three seconds after the start of local anesthetic injection, injection pressure was measured and pain and anxiety were assessed. Injection pressure was measured continuously in real time by using an invasive sphygmomanometer and analytical software, and pain was assessed on the Visual Analogue Scale and anxiety on the Faces Anxiety Scale. A significant correlation was evident between injection pressure and pain (rs = .579, P = .00124) and between intensity of injection pressure and state anxiety (rs = .479, P = .00979). It is therefore recommended that local anesthetic be injected under low pressure (less than 306 mm Hg) to minimize pain and anxiety among dental patients.Abstract
Measurement of injection pressure during local anesthetic. A, A computer-controlled local anesthetic delivery system syringe. B, Pressure transducer and connection to tubes. C, Invasive sphygmomanometer. D, Analytical software and personal computer. E, The patient marks the perceived level of pain and anxiety on the linear Visual Analogue Scale and Faces Anxiety Scale. F, Puncture site and injection of local anesthetic. The hand piece, shortened to half-length, is held like a pen. G, Cheek retractor pulling the lower lip. H, The syringe's foot pedal.
A buccal infiltration injection into the mandibular anterior region with a needle and computer-controlled syringe for local anesthetic (2% lidocaine with 1 : 80,000 epinephrine). A pressure transducer was connected between the hub of the needle and the hand piece. A, Needle puncture: the needle bevel was pointed away from the labial side to perform submucosal puncture while stretching the labial gingival mucosa at the right lower canine position. B, Start of injection: enlargement of the bulge at the injection site during infusion speeds of either 30 or 160 s/mL.
Pain was assessed on the standard Visual Analogue Scale. On a horizontal 100-mm line, patients indicate their level of pain by choosing a numerical score between 0 and 100.
Anxiety was assessed on the standard Faces Anxiety Scale. On a horizontal 100-mm line, patients indicate their level of anxiety by choosing a number between 0 and 5 that also corresponds to a drawing of a facial expression ranging from smiling (far left) to extreme anxiety (far right).
The relationship between Visual Analogue Scale pain score and local anesthetic injection pressure at the start of injection. The regression line is plotted in bold. Injection pressure was a significant predictor of increased pain.
The relationship between Faces Anxiety Scale score and local anesthetic injection pressure at start of injection. The regression line is plotted in bold. Injection pressure was a significant predictor of increased anxiety.
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