There you are with a giant needle sticking out of your face and your dentist starts to shake your cheek. What do they think they are doing? Is the shaking supposed to distract you? Well, it’s not working! Or is it? These are the thoughts that rush through many patient’s minds when I am giving anesthesia. I know this, because I myself have been on the receiving end of dental injections. Many of my own patients ask me why I shake their cheek. So, does it do actually anything? Or is it just sort of a habit that dentists acquire over the years like baseball players and chew?
Basic Nerve Physiology
Nerves perform many functions in our bodies, and they do them all quite well. One thing nerves are not so good at though, is feeling more than one sensation at a time. Nerves can detect vibration, temperature change, odor, flavor, light, pressure, pH, sound, and other sensations as well. Nerves are actually pretty amazing. But, nerves have their limitations. One limitation is their inability to detect pain stimulus when they are already detecting non-painful stimulus.
Dentists take advantage of this limitation to reduce the pain you feel by shaking or rubbing your cheek. Because the act of shaking or rubbing is detected by millions of nerve endings, those nerves are unable to detect pain. This phenomenon is called the gate control theory of pain. Basically, a non-painful stimulus like rubbing or shaking closes the nerve “gates” to painful stimulus. Thus, by shaking your cheek, many of your nerves are are unable to send pain signals to your central nervous system.
Some intrepid equipment manufacturers have taken advantage of this physiologic feature and created specialized syringes that vibrate. The vibration of the syringe reduces the amount of pain a patient feels. But, these devices are costly and require significant upkeep, so many dentists prefer the low-tech approach.
Next time your dentist shakes or rubs your cheek you will understand why. Better yet, you will understand that your dentist is going the extra mile to decrease your pain.