A night guard is an oral appliance worn over the teeth, typically while sleeping. Its primary function is to create a physical barrier between the upper and lower teeth, protecting dental surfaces from wear. This protective device is commonly recommended for individuals who suffer from bruxism (involuntary teeth grinding and jaw clenching). By cushioning the force generated by these habits, the appliance helps safeguard the teeth, restorations, and surrounding structures from damage.
Understanding Jaw Resting Position While Wearing a Guard
You should generally be able to close your mouth with a night guard, although the sensation of your bite will feel different. A properly fitted night guard prevents the full, habitual closure of your teeth (full occlusion). It achieves this by introducing a specific vertical dimension, which separates the upper and lower jaws.
The guard’s thickness is calibrated to maintain your jaw in a relaxed, therapeutic position, known as the physiologic rest position. This separation keeps the jaw muscles from contracting with full force, which is the underlying cause of clenching and grinding symptoms. For some designs, the guard may only contact the anterior teeth, a technique that reduces the firing of up to 90% of the powerful chewing muscles.
The appliance teaches the jaw to rest in a position that minimizes muscle strain. While your teeth will not meet in their normal biting relationship, the jaw should feel comfortable and unforced when the mouth is closed. The goal is a comfortable, slightly open resting position, not a painful or strained closure.
How Device Type Affects Fit and Closure
The type of night guard significantly influences how naturally your mouth feels when closed. Custom-fitted guards are created from impressions of your teeth and integrate seamlessly with your unique bite pattern. Made of hard acrylic, these guards allow for a slimmer profile that maintains the therapeutic jaw position without feeling bulky.
A custom guard guides the jaw into the ideal, relaxed resting position, promoting easy closure and comfort. In contrast, over-the-counter (OTC) or “boil-and-bite” devices are mass-produced and offer a one-size-fits-all approach. These materials are often softer and bulkier, which interferes with natural closure and creates an awkward feeling.
Since OTC guards lack precise dental measurements, they may not correctly position the jaw, potentially leading to a forced or strained closure. The imprecise fit can also cause the guard to shift during sleep, compromising the protective barrier and feeling substantially less comfortable than a custom appliance.
Symptoms of a Poorly Fitted Night Guard
Even if you can close your mouth, several warning signs indicate that your night guard is not correctly fitted or is positioning your jaw improperly. Persistent jaw soreness or tenderness upon waking suggests that the appliance is placing uneven pressure on the temporomandibular joint (TMJ) instead of relieving it. A poorly aligned guard can exacerbate symptoms of temporomandibular disorders, sometimes leading to clicking or popping in the joint.
Waking up with new or worsening headaches, particularly tension headaches, is a common symptom of an ill-fitting device that causes increased muscle strain. An improper fit can also lead to subtle but harmful tooth movement over time, resulting in teeth feeling loose or a noticeable change in how the upper and lower teeth meet when the guard is removed.
If the guard feels excessively bulky, irritates the gums or cheeks, or falls out during the night, it is not providing effective protection and requires adjustment. Any discomfort that does not subside after the initial adjustment period of a few days to two weeks signals the need for professional evaluation or refitting.