The high-pitched sound produced when teeth rub together, often described as a squeak, is a common observation. This acoustic effect is usually not a sign of a problem, but rather a direct consequence of the unique physical properties of the tooth surface. The sound is a momentary manifestation of friction and vibration occurring on dental enamel, the hardest substance in the human body.
The Physics of Teeth Squeaking: Friction and Vibration
The sound generated when two smooth, hard surfaces slide against one another is a mechanical process known as “stick-slip” friction. The squeak is not produced by continuous, smooth movement. Instead, it results from a rapid cycle where the surfaces momentarily stick together and then quickly slip apart.
This cycle of sticking and slipping causes the teeth to vibrate at a high frequency. These rapid vibrations create sound waves that we perceive as a sharp, high-pitched squeak. The smooth, dense, and hard composition of tooth enamel is a perfect prerequisite for this vibrational sound production, similar to how a bow creates sound on a violin string.
Why Surfaces Get Squeaky: Role of Saliva and Enamel
The main variable determining if the stick-slip mechanism produces sound is the level of lubrication between the surfaces. Saliva acts as the mouth’s natural lubricant, containing water and mucus that reduce friction during normal movements like chewing or speaking. When the saliva layer is thick and flowing normally, the surfaces glide easily, and the vibrational effect is dampened.
If saliva levels are low, the frictional resistance between the enamel surfaces increases, making the stick-slip effect much more likely. Squeaking is often noticed first thing in the morning when the mouth is dry, or after consuming foods that reduce moisture. The surface texture of the teeth also plays a part, as recently polished or professionally cleaned enamel may be unusually smooth, temporarily intensifying the effect.
When Squeaking Signals a Problem: Dental Wear and Bruxism
While occasional squeaking is normal, frequent or loud noise may signal an underlying condition that increases friction. Chronic teeth grinding or clenching, medically termed bruxism, is a common culprit that increases the likelihood of squeaking. Nocturnal bruxism involves the lower jaw moving side to side while clenched, which can create a distinct squeaking noise loud enough to wake a sleeping partner.
Grinding and clenching over time causes excessive wear, which flattens and smooths the biting surfaces of the teeth. This creates unnaturally smooth planes of contact, making them more susceptible to stick-slip friction. Acid erosion from dietary habits or reflux can also wear down the enamel, resulting in flat, smooth areas. If the squeaking is accompanied by symptoms like jaw pain, headaches, or tooth sensitivity, it suggests a chronic wear issue that warrants evaluation by a dentist.