Most adults have had the experience of needing a cavity filled or some other type of minor dental work that would be more comfortable—or even tolerable at all—with local anesthesia.
Thinking back on my dental care over the years, I cannot recall a single instance when a dentist explained to me the risks that come with a local anesthetic injection into my gums. I guess I never really thought about what could go wrong, that is, until I started handling more and more nerve injury cases in my career as a Texas medical and dental malpractice lawyer.
Types of anesthetic injections
An injection to numb feeling in the lower jaw is called a mandibular block, while an injection to numb the upper jaw is referred to as a maxillary block.
The overwhelming majority of complications and problems occur during mandibular blocks, as opposed to those involving the upper jaw.
What can happen after a dental anesthetic injection?
Injury to one of the nerves of the mouth is one of the most common injuries after a dentist injects local anesthetic into a patient’s gums.
Over two-thirds of nerve injuries after a local anesthetic injection involve the lingual nerve, which supplies the tongue. The second most-common nerve injury is to the inferior alveolar nerve, which supplies the lip and chin. There have also been reports of less-common injuries to the chorda tympani, which involve the sensation of taste.
Generally speaking, there are three types of nerve injuries that can be caused by the injection of local anesthetic.
Anesthesias involve the total absence of sensation, including pain.
Paresthesias are a broader category of abnormal feeling, and includes thins like numbness and a “pins and needles” feeling.
Dysesthesias refers to pain that can start suddenly and unpredictably, or in response to a stimulation that would not normally be painful.
Studies have shown that about two-thirds of patients with permanent nerve injuries experience anesthesia or paresthesias, leaving one-third to experience dysesthesias. Most people find anesthesia or paresthesias very unpleasant. Patients with dysesthesias frequently describe the pain as unbearable, and the condition causes many people to develop chronic anxiety.
Overall, dental nerve injuries from an anesthetic injection resolve on their own about 90% of the time within eight weeks. More specifically, though, injuries to the inferior alveolar nerve are more likely to favorably recover than injuries to the lingual nerve.
It is not a good sign if the abnormal symptoms persist beyond the eight-week mark. That is viewed as the point when there is a significant decrease in the chance of recovery.
What can cause a nerve injury?
Needle trauma. The needle that the dentist uses to make the injection can cause a nerve injury by traumatizing the nerve.
This happens most often with the lingual nerve, which is located very close to the mucosa (oral surface) and next to the site where the local anesthetic is injected. In addition, because the mouth must be open for the injection, the lingual nerve is stretched and held in place, making it unlikely that the nerve will be able to wiggle out of the way if the needle hits it.
In order to decrease the odds of physically damaging the lingual nerve, the standard of care requires dentists performing a mandibular block to insert the needle until it touches bone, to ensure the proper location for the injection.
Hematoma formation. A hematoma is an abnormal collection of blood outside a blood vessel, which causes swelling as it clots. If the needle injures blood vessels within the nerve tissue during an injection, it can cause a compression injury called compressive neuritis. Within 30 minutes of an injection, hematoma damage can be rather extensive. Later, when scar tissue forms, it makes it difficult for the nerve to heal.
Dentists describe hematomas in two ways, depending on the extent of the injury.
The first, called neurapraxia, is less severe. It involves damages to a limited area of the nerve, without disrupting the axons and connective tissue. Patients with neurapraxia after a local anesthetic injection typically recover within several weeks, as the pressure is relieved and the nerve repairs itself.
The second type of injury is called axonotmesis, and involves some amount of damage to the axons (nerve cells that carry electrical impulses) and connective tissue (the structure that holds nerve fibers together). If the patient recovers, it takes a longer time for the nerve tissue to build a bridge to span the gap where the damage occurred.
Toxic anesthetic medications. Some anesthetic medications themselves can damage nerve tissue. This is particularly true of anesthetics that contain alcohols, which are now not commonly used because of this problem. Such anesthetic medications are chemically toxic to nerve tissue, and can damage or destroy the protective myelin sheath around nerve fibers, as well as swelling and loss of oxygen and blood flow.
I have handled a number of cases where alcohol-based injections have caused serious and permanent nerve damage.
Research shows that the anesthetic medications prilocaine and articaine are more likely to cause nerve injuries than lidocaine.
Painter Law Firm is here to help
If you or someone you care for has had a nerve injury because of dental care, we understand that it can be life-changing. Call us at 281-580-8800, for a free consultation with an experienced medical and dental malpractice attorney.