Your top and bottom teeth are not supposed to touch when the jaw is in its natural resting state. The ideal posture involves a relaxed jaw, with the lips gently closed and the teeth separated by a small space. This separation is a physiological necessity, allowing the muscles that control jaw movement to remain at rest. Constant contact indicates muscle tension and can lead to significant dental and musculoskeletal problems.
The Concept of Interocclusal Clearance
When the jaw is completely relaxed, a subtle gap exists between the chewing surfaces of the upper and lower teeth, known as interocclusal clearance. This phenomenon is also called the “freeway space” and represents the mandible’s position when the elevator muscles are minimally active. This space is a natural mechanism designed to prevent the masticatory muscles and the jaw joint from being overworked.
This resting space typically measures two to four millimeters between the upper and lower teeth. This distance is significant because it places the jaw muscles, such as the masseter and temporalis, in a state of equilibrium. Without this separation, these muscles would be under constant, low-level strain throughout the day.
This resting posture supports the long-term health of the entire chewing system. The separation allows for the recovery and maintenance of muscle fibers, preventing fatigue and chronic tension. If the teeth are perpetually touching, the muscles must remain contracted, disrupting this natural cycle of rest.
Essential Functions Requiring Tooth Contact
While teeth should be separated at rest, specific active movements require the upper and lower teeth to meet. The most recognized functional contact is mastication, or chewing, which requires forceful, repeated contact to break down food fibers. During this process, the teeth are brought together under considerable force to crush and grind food into a swallowable bolus.
Another necessary, brief moment of contact occurs during deglutition, or swallowing. When swallowing, the jaw briefly stabilizes to provide a firm base for the muscles of the tongue and throat. The forces generated during this momentary contact can be substantial, sometimes reaching up to 40% of the maximum biting force.
Speech is another function involving the jaw, but it generally occurs with the teeth separated. The dynamic movement of the lips and tongue, rather than tooth contact, forms most sounds. Light, momentary contact might occur for specific phonemes, or speech sounds, but this contact is fleeting and does not involve sustained, heavy forces.
Health Implications of Constant Tooth Contact
When teeth meet outside of necessary functions, it is considered a parafunctional habit that can cause extensive damage. These habits typically manifest as clenching or bruxism, both of which eliminate the protective interocclusal clearance. Clenching involves sustained, static pressure, while bruxism includes dynamic movements like grinding or gnashing, often occurring unconsciously during sleep.
The constant friction and pressure from these habits lead to accelerated tooth wear, causing premature enamel erosion. This erosion can expose the softer, underlying dentin layer, resulting in heightened tooth sensitivity to temperature changes and pressure. Sustained force can also lead to chipped, cracked, or fractured teeth, necessitating restorative dental work.
Excessive and chronic tooth contact places immense strain on the temporomandibular joints (TMJ) and surrounding muscles. This overuse can trigger Temporomandibular Disorders (TMD), characterized by symptoms like chronic jaw pain, morning muscle stiffness, and restricted jaw opening. Constant joint compression can also cause an audible clicking or popping sound upon movement.
Sustained muscle tension can lead to referred pain, where discomfort is felt in a location other than its source. Patients experiencing chronic clenching often report tension headaches or earaches, resulting from fatigued jaw muscles radiating discomfort. Individuals who suspect they are clenching or grinding should consult a dental professional to prevent further damage.