Feeling a space between your upper and lower teeth when your jaw is relaxed and your mouth is closed is a common observation. This often leads to the mistaken belief that teeth should always be in contact. The reality is that the jaw’s natural state of rest is one of slight separation, which is a healthy and functional position for the facial and jaw muscles. Understanding this normal gap helps determine if your situation is typical anatomy or a condition requiring attention.
The Healthy Resting Gap
The slight space between your teeth when your jaw is resting is known as the interocclusal rest space, or “freeway space.” This separation represents the mandible’s natural postural position when the jaw muscles are in a minimal state of contraction. When the muscles are relaxed, the lower jaw assumes this position, slightly below where the teeth meet.
The size of this healthy resting gap typically falls within a range of 2 to 4 millimeters when measured at the front teeth. This gap is necessary to prevent constant stress on the jaw joints (temporomandibular joints) and to allow the muscles of mastication to rest. If this space were absent, the teeth would constantly grind against each other, leading to excessive wear and muscle fatigue. This physiological rest position is distinct from the bite position, where the upper and lower teeth are fully interlocked for biting or chewing.
Defining Open Bite Malocclusion
While a small resting space is normal, a true open bite is a type of malocclusion, or misalignment, where the upper and lower teeth fail to overlap or touch even when the back teeth are engaged. This failure of vertical dental contact can affect different parts of the mouth.
It is most common for this misalignment to occur at the front of the mouth, known as an anterior open bite, where the incisors do not meet. Less frequently, the back teeth fail to make contact while the front teeth may touch, which is classified as a posterior open bite. The severity of the malocclusion can range from a minor issue involving only a few teeth to a complete open bite that affects most of the dental arch.
Factors Contributing to Open Bite Development
Open bites are often caused by a combination of skeletal, habitual, and dental factors. Skeletal factors relate to the growth pattern of the facial bones, where a disproportionate vertical growth of the jaw can result in an open bite. This growth pattern often results in a longer lower facial height, which prevents the upper and lower dental arches from meeting properly. These skeletal discrepancies are frequently inherited.
Habitual factors are major contributors, particularly in children whose jaws are still developing. Prolonged, non-nutritive sucking habits (such as thumb sucking and extended pacifier use) can physically push the developing teeth out of alignment. Tongue thrusting is another factor, where the tongue pushes against the front teeth during swallowing or rest, interfering with natural eruption and alignment. This constant pressure prevents the front teeth from fully erupting into a closed bite.
Dental factors, such as issues with tooth eruption, can also result in an open bite. A dental open bite may occur when the teeth are prevented from erupting fully into the correct position. In rare cases, the failure of teeth to erupt due to conditions like ankylosis or primary failure of eruption can cause a localized posterior open bite.
Addressing and Correcting an Open Bite
The treatment approach for an open bite depends on the underlying cause and the patient’s age. For open bites caused by habits, especially in younger patients, the initial step involves behavior modification and myofunctional therapy. This therapy focuses on retraining the oral and facial muscles, correcting improper tongue posture, and establishing a normal swallowing pattern by teaching the tongue to rest against the palate instead of the front teeth.
Orthodontic solutions are commonly used to correct the misalignment, ranging from traditional braces and clear aligners to specialized appliances. Specific devices, such as a palatal crib or bonded spurs, can physically intercept and break persistent habits like thumb sucking or tongue thrusting. In some cases, orthodontic mechanics focus on molar intrusion to close the bite vertically, often achieved with modern tools like temporary anchorage devices (mini-implants).
For severe skeletal open bites, particularly in adult patients where jaw growth is complete, the most predictable treatment involves orthognathic surgery combined with orthodontics. This surgical intervention corrects the underlying jaw discrepancy by repositioning the upper and lower jaws into a harmonious relationship. Given the complexity and high risk of relapse, careful diagnosis by an orthodontist and a multidisciplinary approach are necessary for a stable, long-term outcome.