A night guard (occlusal splint) is a removable dental appliance designed to protect the teeth and jaw structures during sleep. This device acts as a cushioned barrier between the upper and lower teeth, shielding the natural tooth surfaces from direct contact. Its primary function is to mitigate the damaging forces associated with bruxism, which is the involuntary clenching or grinding of the teeth. Bruxism generates significant force, which can lead to excessive wear, fractures, and sensitivity of the teeth, as well as pain in the jaw joints and facial muscles. By covering one dental arch, the night guard absorbs this pressure and reduces the strain on the temporomandibular joints (TMJ) and surrounding musculature.
Determining Arch Placement
The decision regarding whether a night guard should be placed on the upper or lower arch is a clinical one, determined by a dental professional. The upper jaw, or maxillary arch, is the most frequent choice for night guard placement. This preference exists because the upper arch typically provides a larger, more stable surface area for the appliance to grip, ensuring a secure fit throughout the night. However, the lower arch is often preferred in specific situations based on patient comfort and anatomy. For example, individuals who experience a strong gag reflex often find a less bulky lower appliance easier to tolerate.
Dental and Clinical Criteria for Selection
Beyond general comfort and mechanical stability, a dentist’s final determination of arch placement relies on specific diagnostic and clinical criteria unique to the patient. The presence of existing dental restorations is a significant factor. It is generally advisable to place the guard on the arch with fewer crowns, bridges, or partial dentures. This minimizes the risk of inadvertently stressing or damaging these complex dental structures.
The patient’s specific bite alignment, or occlusion, also influences the placement decision. For patients whose primary concern is the protection of teeth from simple grinding, the choice is often driven by which arch offers a more balanced contact point with the opposing teeth. If the night guard is intended to treat a Temporomandibular Joint Disorder (TMD), the placement becomes more critical for achieving a balanced jaw position.
In TMD treatment, the guard is often designed to guide the lower jaw into a specific, relaxed musculoskeletal position, such as centric relation. The pattern of bruxism can also be a consideration. For patients who primarily clench their teeth with axial force, an upper guard may be selected to cushion the direct impact. Conversely, if the patient exhibits heavy lateral grinding movements, the arch with the least amount of existing dental work may be selected to provide a durable, flat plane for the opposing teeth to glide against.
How Device Type Impacts Placement and Fit
The type of night guard significantly impacts both the precision of the fit and the effectiveness of the chosen arch placement. Custom-made guards, which are fabricated from a mold of the patient’s teeth, are specifically designed for a single arch, ensuring optimal retention and therapeutic outcomes. The material and design of a custom guard are tailored to the contours of the mouth, providing a secure fit that will not shift.
In contrast, over-the-counter (OTC) boil-and-bite guards offer a much lower level of precision and are often bulkier. These generic appliances are not custom-molded to the unique shape of an individual arch, which can lead to an unstable fit regardless of whether it is placed on the top or the bottom. Since a precise, stable fit is necessary to achieve the desired cushioning and jaw-positioning effects, customization is paramount for successful treatment.