Jaw misalignment, often referred to as malocclusion, describes a condition where the upper and lower teeth do not properly come together, or the lower jaw is positioned awkwardly relative to the skull. This issue is not purely cosmetic; it can interfere with speaking, chewing, and overall oral function. Since the jaw is a complex system involving bones, joints, muscles, and teeth, the origins of misalignment are diverse, spanning genetics, growth patterns, function, and external factors. Determining the precise cause requires a professional diagnosis for effective management.
Issues Stemming from Dental Alignment
The most common source of perceived jaw misalignment is malocclusion, defined by the improper meeting of the upper and lower teeth. This is a dental issue, distinct from problems with the underlying jawbones. Proper occlusion occurs when the upper teeth slightly overlap the lower teeth, and the pointed ridges of the upper molars fit into the grooves of the lower molars.
When this relationship is incorrect, the jaw may be forced to shift to find a comfortable biting position, leading to a functional misalignment. Dental crowding, where there is not enough space for all the teeth, or significant gaps can disrupt the bite plane. Similarly, a missing tooth or the premature loss of a baby tooth can cause neighboring teeth to drift, leading to an uneven bite.
Poorly fitted dental restorations, such as a filling or crown that is slightly too “high,” can cause the jaw to deflect upon closing. The constant interference forces the jaw muscles to adjust the closure pattern, which can strain the system and create the sensation of a misaligned jaw. Correcting these dental discrepancies often relieves the associated muscle strain and functional shift.
Issues Stemming from Skeletal Structure
Beyond the position of the teeth, misalignment can originate from developmental or genetic factors affecting the size and relationship of the upper and lower jawbones (maxilla and mandible). These skeletal discrepancies are inherited and represent a structural foundation for the misalignment. The relative growth of these bones determines the overall profile and how the dental arches relate to each other.
One example is mandibular prognathism, where the lower jaw (mandible) is significantly larger or grows forward more than the upper jaw. This results in an underbite, where the lower front teeth sit in front of the upper teeth. Conversely, mandibular retrognathism describes a lower jaw that is too small or set back, creating a pronounced overbite.
These differences in bone structure create a large horizontal gap between the dental arches that teeth alone cannot overcome. Unilateral growth issues, where one side of the jaw grows differently, can cause the chin and lower jaw to deviate to one side, leading to facial asymmetry. Such structural misalignments often require orthodontics and, in severe cases, corrective jaw surgery to re-establish a balanced skeletal relationship.
Problems with the Temporomandibular Joint
The temporomandibular joints (TMJs) are the hinges connecting the lower jawbone to the skull, enabling movement for speaking and chewing. Problems with this joint, its surrounding muscles, or associated ligaments are collectively known as Temporomandibular Disorders (TMD), a common functional cause of jaw misalignment. This misalignment is often functional, meaning the jaw shifts due to a problem in the joint’s mechanics rather than a static bone or tooth position.
One frequent issue is internal derangement, involving the displacement of the small articular disc within the joint capsule. This disc acts as a shock absorber; if it slips out of its normal position, it can cause a clicking or popping sound as the jaw opens and closes. If the disc is displaced too far forward, it can temporarily block the motion of the jawbone, leading to a “closed lock” that severely limits mouth opening.
Chronic strain on the muscles that control jaw movement is a major contributor to TMD. Habits like bruxism (involuntary clenching or grinding of the teeth) create excessive force on the joint and muscle group. This sustained tension can cause muscle spasms, pain, and an alteration in the resting position of the jaw. Furthermore, conditions like arthritis can cause degenerative changes within the joint, leading to pain and a change in how the upper and lower jaws fit together.
Causes from Injury or External Habits
Acute trauma and chronic external habits represent acquired causes of jaw misalignment. An immediate shift in the jaw’s position can occur from an injury, such as a hard blow to the face during an accident or sports. Trauma can result in a fracture of the jawbone or a dislocation of the temporomandibular joint, physically forcing the jaw out of its normal alignment.
Beyond acute injury, certain long-term habits can slowly influence jaw position. Persistent mouth breathing, often due to allergies, alters the resting posture of the tongue and jaw, which can affect facial structure development and contribute to malocclusion. Similarly, poor body posture, particularly forward head posture caused by slouching, strains the neck and jaw muscles. This chronic strain can lead to muscle tension that pulls the lower jaw out of its balanced position.