Acute or Chronic Pain
Fortunately or unfortunately, bruxism aches and pains are a functional, healthy response. It is the body’s way of sending a message that something is not in sync and an adjustment needs to occur. Any injury to the body causes other muscles, ligaments or tendons to overcompensate for the injury. Over time, those compensations also become weak and unproductive. Common aches or pains can progress from mild to severe depending on the aggressiveness and repetitiveness of the bruxing.
Any of these pains can be acute (comes and goes) or chronic (comes but never goes). Teeth sensitivity can be very specific or generalized. Jaw pain can be from the muscles or joints and can feel overworn, fatigued, stiff or throbbing. Headaches can be in the morning or night, constant or fluctuating and can range from a slight dull pain to an intense migraine. Cheeks can feel tired, worn or sore when chewing. The TMJ can have inflammation, become locked or have limited opening of the mouth. Earache pain can feel like a dull pain or an intense shooting pain leading into the ear. Neck and shoulder pain can feel dull, stiff, achy or intense.46
When grinding with the anterior teeth, there may not be any pain beyond those specific teeth. But when grinding the posterior teeth, the masseter and temporalis muscles are more involved, which can create more facial and head pain.4 Myalgia may worsen during function, along with tenderness on palpation.16
Sensitivity of the Teeth
Sensitivity can be localized, generalized, constant or sporadic. One of the first symptoms of bruxism is hot and cold sensitivity to the teeth. This is caused by the flexing that occurs when teeth are ground from side to side. Teeth were not designed to flex, so they deteriorate at the areas of bending above the gingiva.4 This area can become very sensitive with abfractions developing at the roots and causing receding gingiva. Many times patients do not know which exact tooth is causing the sensitivity, or even if it is maxillary or mandibular. When there are not obvious signs of bruxism, treatment is usually desensitizing toothpaste, which temporarily resolves the problem.
Sensitivity related bruxism can be challenging to diagnose. The thinning of enamel can cause underlying dentinal sensitivity. The tooth may acclimate to the new conditions. Additional enamel loss and reacclimation may lead to the “coming and going” symptoms of sensitivity.
A common symptom is pain in and around the TMJ. This pain is usually felt when opening and closing the mandible; however, it can also occur while the mandible is in the resting position. Discomfort can occur through hyperactivity, spasms or overworked muscles. As with any other muscle, when contracted for a long period of time, the muscle fibers start to present fatigue or inflammation that produce the pain. Overt tissue damage, injury or trauma and overloading stress of the jaw muscles and TMJ during bruxism can activate nociceptors (receptors for pain stimulated by various kinds of tissue injury and pain).4,46 These conditions can cause inflammation of the stressed areas and coincidentally cause pain as well. This type of pain is characterized as a fairly prolonged, deep dull ache, often similar to the discomfort associated with a nagging headache. A sharp, brief shooting pain or a feeling of numbness in the orofacial area is another symptom. Bruxism can cause stiffness in the TMJ and masseter muscles.
Changes that happen in the TMJ arise from pathologic processes more than physiologic adaptation, which can cause the entire dentition to undergo a continuous adaptation to functional wear. Adjustments in the orofacial region are constantly being supported by the wear caused by bruxing.47 Repetitive overloading of the TMJ through bruxing can be a factor in osteoarthritis. Bruxing pain in the TMJ area includes the retrodiscal pad, synovial membranes of the joint capsule and collateral ligaments of the disc-condyle complex.47 Bruxism can cause nightly bruising of the TMJ with a dislocated disk and can sometimes function as a sustaining factor in the cycle of pain and muscle tightness.47
Patients with Temporomandibular Disorder (TMD) often hear clicking, popping, or grating noises in their TMJ.4,46,47 The clicking noise commonly heard and palpated during opening or closing is a result of this disc slipping out of place, sticking, or malfunctioning. Although some clicking and popping sounds in the TMJ can be normal and insignificant, when the sound is grating or gravel like, the joint and disc may be breaking down (degenerating). This requires a more involved evaluation. Clicking sounds may occur in one or both joints when the bony joint and disc movement are not coordinated. The click may occur when opening or closing and with lateral movements as well. The jaw may shift to the side and may catch or lock during any of its movements.48 Although the disc can quickly reorient itself and normal jaw function can be restored, sometimes this problem can worsen. The disc wear can continue and result in a more severe displacement. Occasionally, this can be a painful event that results in a reflex contraction of the chewing muscles which locks the TMJ in an open dislocated position. This is referred to as an open lock.48 When these situations arise, a referral to a TMD dental specialist would be most beneficial for the patient.
Muscles, Neck Pain and Headaches
Since the masseter muscle is considered one of the strongest single muscles in the body, when the muscle is worn and fatigued from bruxing, it can cause localized and referred pain.43,49 The masseter alone can be inflamed and fatigued, causing localized pain. The masseter attachment trigger points at the upper superficial layer can have referred pain points to the mandible, teeth and gingival area. The mass superficial layer can also have referred pain patterns to the mandible, teeth and gingival area. The attachment trigger point of the lower superficial layer refers pain to the mandible and above the eyebrows. The trigger point of the upper posterior deep layer below the TMJ refers pain to the ear area.49,50,51
Even if muscle pain does not occur, muscle hypertrophy can result.16 Bruxism involves excessive muscle use, which can lead to enlargement of the facial muscles. In long-term bruxers this enlargement can cause a square jaw appearance.52
Bruxism may lead to chronic headaches, although the correlation is not entirely clear. One perspective could be the aches and pains are from disturbed circulation in the muscles. Another suggestion is the tightening of the entire mandible and face during bruxing can cause headaches.5,50 Bruxers are three times more likely to experience headaches than non-bruxers.18 The use and tightness of the masseter muscles and the clamping down of the dentition connects with the neck muscles causing neck pain.52