© Andrey Popov | Dreamstime.com
Dreamstime M 213586576

Sprained tooth syndrome explained

March 26, 2021
A sprained (or bruised) tooth is a pain—literally. Learn more about identifying and treating this sometimes overlooked issue.

Modern dentistry, in all of its technology over the last 50 years, has solved many of the problems that have arisen with the increase of tooth retention. However, situations still arise that reasonable practitioners can disagree on in terms of diagnosis and treatment. Such disagreements may lead to delayed effective treatment, unnecessary procedures, or excessive actions. All create a situation of frustration for the patient and the dentist resulting in ill will and unproductive activity.

Consider a common example: A patient presents the following concerns: dull generalized ache, intermittent gum "itchiness," pain when probing localized gum pockets, soreness to chew, sensitivity to temperature, and the occasional headache. The pain isn't severe enough to wake the patient from sleeping, but there's enough discomfort for the patient to make a specific appointment to discuss the problem. In addition, the patient recently had a cavity filled in the area of discomfort.

A good course of action to diagnose the issue is to take an x-ray, temperature tests, percuss, and bite tests to isolate potential problems. It is also reasonable to check the patient's bite with articulating paper to determine potential high spots. Yet, common strategies do not seem to address or clearly identify the patient's problem. There are no cavities, cracked teeth, sinus issues, or sharp pains associated with biting. There are clinical signs of a molar rise with a lateral excursion on the patient's working (chewing) side, and also a balancing side contact on the same tooth with the opposite lateral excursion. In addition, the tooth is slightly mobile and the periodontal tissues are tender and bleed upon probing. The x-ray does indicate a slightly thickened periodontal ligament space and a slightly thickened layer of cortical plate surrounding it, but no bone loss is evident.

At this point, there could be disagreement on the next steps to take. Some practitioners might attempt to correct the problem by filing the tooth down or replacing the filling. Others might perform a root canal or crown, a few would event think to extract the tooth, and some might do nothing. But there's another plausible diagnosis (and possible treatments)—"sprained tooth syndrome."

Related reading:

Jaw sprain or jaw strain symptoms and treatments

How to manage toothache pain

Sprained tooth syndrome

Sprained tooth syndrome (STS) is defined as a condition where unusually strong bilateral opposing vector forces cause the ligaments connecting a tooth to the bone to become stretched and chronically inflamed, creating patient discomfort similar to that which is described above. Just as ligaments can be stretched and damaged in an ankle or other parts of the body, similar damage can occur with the ligaments connecting a tooth to the bone resulting in STS.

Common causes that could lead to STS are:

  • Cold, sinus problems, or allergies
  • Trauma from small objects (popcorn seed, etc.)
  • Filling or crown overfilled
  • Filling underfilled
  • Drifting of teeth
  • Early vital tooth infection
  • Damage, wear, or improper repair to discluding working side teeth (canine rise or group function is desirable)

One common cause of STS is tooth movement due to sinus problems or colds. Excessive swallowing as a direct result of sinus drainage may result in abnormal outward lateral pressure from the tongue to the teeth, creating temporary orthodontic pressure and movement outward. This temporary outward shift of the tooth may place the lingual cusp in harm's way of damaging lateral tooth to tooth forces. As such, it is critical to determine why the teeth are moving and causing horizontal friction to occur. In cases such as a cold or sinus condition, waiting for the patient's health to improve may be the best course of action. After the cold has resolved, there will be less tongue pressure and the cheek pressure will move the tooth back into a harmonious position.

Another cause of STS can be accidental trauma or trauma from a small object such as a popcorn seed or a bone in a piece of meat. This trauma can cause temporary periodontal ligament damage and swelling which can cause the tooth to supra-erupt into a harmful position which can then indefinitely prolong the inflammation.

Dentistry itself can promote these damaging conditions to occur in the mouth. If a crown is fabricated with a perfect centric contact but cusps that interfere with lateral excursive movements, STS can develop. Likewise, if the centric contact of a filling or crown is left too low, over time (a few days to a few weeks) the tooth can supra-erupt and move one or more cusps into an occlusal interference which would result in STS induced inflammation.

Drifting teeth are always at risk of moving one or more cusps into this damaging lateral excursive pathway.

Sometimes a tooth infection can cause supraeruption of that tooth, placing the cusps in harm's way. The ensuing symptoms will be a part of the sprained tooth syndrome but secondarily to the tooth infection, again underscoring the need to find out why a tooth has moved into this damaging position. In all cases of STS, it is very important to follow up (after two weeks, four weeks, three months, and six months) to make sure symptoms are resolved and an infection was not the root cause of the STS.

Finally, a less obvious but equally important cause of STS is the damage, wear, or improper repair of the discluding (working side) teeth. It is this working side protection (canine rise is best) that keeps the balancing side cusps out of trouble.

In short, posterior teeth are designed to absorb heavy forces in the direction of the long axis of the tooth. Most posterior teeth are not designed to absorb damaging lateral forces, which can result in STS. Determining how these damaging forces have come about is important in determining treatment.

Identifying STS is not as simple as it may seem. Sometimes symptoms may lead you to believe the problem is STS when in actuality it's an early vital tooth infection. A vital tooth infection is defined as an early infection of a tooth that has a nerve that is partially infected and partially vital, resulting the same symptoms and discomfort as STS.

A few prudent tests should allow dentists the confidence that they have adequately diagnosed STS:

1. Place a cotton roll or "Tooth Sleuth" over the suspected teeth and have the patient bite. Ask the patient where they think the problem is located. Also ask if the bite pain is sharp or dull and achy. Dull and achy is indicative of STS. Sometimes with this test, the patient is not sure if the pain is coming from the top or bottom.

2. Use the perio probe on the gum tissue to find the tender area or abnormal gum pocket and observe the patient for discomfort that may indicate inflammation. The gum tissue may be tender circumferentially, or sometimes it may be localized on one side of the tooth affected.

3. Percuss teeth with mirror handle and observe the patient for pain response which may indicate periodontal inflammation.

4. Pulp test and cold test teeth. A sprained tooth, unless it has been root-canaled, could be sensitive to cold and should respond to a pulp test, possibly with an elevated reading pending any associated pulpal inflammation secondary to periodontal inflammation.

5. Place articulating paper over the affected teeth and have the patient grind widely right and left. Observe the markings. Any balancing side contact accompanied by a similar intensity working side contact on the same tooth detected by this method can lead you to suspect this syndrome.

How to explain STS to patients

People do not chew their food in a straight up and down motion. Rather they chew on a hinge using a lateral envelope of motion. A person's cuspid/canine teeth should help to protect their molar cusps from banging against one another throughout this motion. Cuspids are long-rooted, thickly buttressed in bone laterally, have slanted incline biting surfaces, and are positioned forwardly in the mouth. These features make the cuspid teeth ideal as the "kickstand" for the mouth. All of these protective features except the forward positioning are self-explanatory.

The mouth is much like a nutcracker—the further back you go in the mouth, the more pressure is exerted. That's why it is so important for the cuspids (which are located anteriorly) to bear the brunt of the chewing strokes to take the pressure off of the molars. If the cuspids fail to protect, then the molars will bump and grind and begin to wiggle. When a post is wiggled back and forth in the ground, eventually the post loosens up and gaps around the post can form.

The dentist needs to restore protection for the molars by either building up the cuspids, adjusting the high spots from the cusps on the affected molars, or trying a few other methods such as fabricating a nightguard/bruxing appliance or orthodontic repositioning. The affected tooth is like a sprained ankle and it will take a week or so to heal. When the patient returns to chewing on the affected tooth, they should start with soft foods first.

In addition, headaches have known to have been caused by muscle tension. STS may also be linked to an increase in grinding, muscle tension, and headaches. In some cases solving these bite problems have resulted in fewer or no headaches. Also, inform the patient that gum-chewing and single side chewing will also aggravate this syndrome.

STS treatment

Treating STS is rather straightforward; the dentist must eliminate the second vector force on the tooth, leaving the centric contact. STS is caused by strong bilateral opposing vector forces, so eliminating one of the opposing forces is essential. However, the elimination of the second vector force can be a complicated process.

The most common strategy is to mark the affected tooth/teeth in lateral excursive movements with articulating paper. Determine the extent and origin of the problem. Then develop a treatment strategy that will remedy the problem.

However, complications may arise, such as in a cross-bite occlusal scheme. As a general rule, if more than one to two teeth are involved, or if by adjusting the bite you will be creating new problems, then you opt to not adjust the second vector contact. There is a body of evidence that contralateral balancing side contacts may be important for condylar joint health. In such cases eliminating this contact may do harm to the TMJ. Building up the protected occlusion on the opposite side of the mouth, fabricating a night-grinding appliance to minimize nocturnal damage, or orthodontically correcting the bite may be safer alternative treatments, especially if the patient doesn't present with any TMJ symptoms.

Opposing vector forces can appear in a buccal/lingual, mesial/distal, or any opposing vector direction in between. The treatment is still the same—safely eliminate the second vector force, leaving the tooth in a stable position so that you don't have to keep adjusting the tooth (or teeth) every six months.

Successful treatment will be indicated by an immediate feeling by the patient that the bite feels different and better. They may say things like "The bite doesn't feel so tight" or "My teeth slide across each other much better." Withina few days and a week, the tooth will feel back to normal with a complete resolution of the subjective symptoms. Headaches and grinding may be completely gone.

This conservative treatment approach is only for patients with mild to moderate pain that is usually manageable with ibuprofen.

Instruct the patient to contact the office if symptoms are not completely resolved within four to five days because it could be a sign that there is an early vital tooth infection which could lead to more serious problems if ignored.

If the symptoms don't resolve or if they get worse, then instruct the patient to contact your office immediately and treat this tooth problem like an infection and prescribe your antibiotic of choice followed by the appropriate treatment.

When to treat

When the reward outweighs the risk.

Risk is:

1. Removing healthy enamel unnecessarily, breaking through to dentin or pulp.
2. Changing the patient's bite to one that is less stable or would somehow worsen their condition. (The more symptoms that the patient has pre-treatment means that there is less risk that you will worsen their condition.)

Minimizing risk:

Limit the adjustment at one to two teeth. If it's more than that (or the occlusal scheme is complex like for instance a crossbite), then you need to consider ortho/jaw surgery, building up cuspids, restoring all posterior teeth affected, or making a lifetime nightguard. Jaw surgery and full mouth reconstruction are the most invasive and should be considered as a last resort.

If there are signs of opposing vector forces but no symptoms, then there is no reward. In these cases you watch it and advise the patient what symptoms may arise in the future.

If a patient makes a dedicated appointment to address this problem, then there is a reward to treating this case and an effort is made to eliminate the second vector force on the affected tooth. Most of the time the tooth and bite will feel 100% better immediately after adjusting.

The reward, of course, is that you fix their pain, you make their bite feel better, you validate their symptoms, you diagnose what others may have missed, you possibly help cure their headaches, and possibly avert future periodontal problems—all using a conservative, cost-effective approach that expresses a genuine concern to solve their problem. The patient can't help but to be grateful if it's successful, and it becomes a huge practice builder.

The liability of not treating is, of course, is that the patient's symptoms, possible periodontal damage, and emotional frustration continue. You may lose the patient altogether.

Follow-up is important for four reasons:

1. To make sure the problem is solved to the patient's satisfaction.

2. It gives you another opportunity to gather information pertaining to the problem which will help you localize and treat it.

3. To make sure that an early vital tooth infection can be ruled out. If symptoms are permanently gone after 2-3 months then you can assume that there is no infection but you still x-ray the tooth at the 6 month recall.

4. It shows the patient that you care and are really listening to their complaints.

There could be many patients who are suffering from this syndrome. It is poorly understood because there are several factors that contribute to its onset and severity:

1. Bilateral opposing vector forces from occlusion, of which premature contacts and eccentric excursions can be very complicated and difficult to detect.

2. Biting force magnitude, of which position in the mouth, steepness of cusps and muscular development are directly related and equally difficult to detect or measure.

3. Frequency of the offending force, of which gum chewing, frequent eating, single-sided chewing, or frequency of grinding are important risk factors.

There are several factors that minimize the impact of this syndrome clinically—especially pain tolerance and blood flow to the area for repair of the inflamed tissue.

Regardless of how obscure this syndrome appears, after reading this article it should be clear that unidirectional forces are tolerated better by teeth than bidirectional opposing vector forces. Furthermore a dentist should be able to identify and treat patients who present with signs and symptoms of the sprained tooth syndrome.

Originally posted in 2007 and updated regularly