Local Anesthetic Failure and Prevention in Dentistry

Why Is Local Anesthesia Needed in Dentistry?

The dental surgeon mandatorily gives local anesthesia (LA) for simple dental procedures like deep scaling and root planing to surgical procedures like:

• Root canal treatment.

• Extraction.

• Dental implantation.

• Jaw fractures.

• Enucleation of the cyst.

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• Gum surgeries.

• Flap surgeries.

• Wisdom tooth removal.

This is because the surgical procedures can be done only by pain control or by numbing the affected area. When the local anesthesia is given, the operator can successfully access and perform the procedure effectively on the patient (endodontic or oral surgical, or periodontal surgeries). According to traditional research, the failure of a local anesthetic to penetrate effectively is deemed around 5 to 15% of the total number of LA injections given by dental surgeons to patients. The dental surgeon cannot be held responsible solely for the success or failure of local anesthesia.

When Is Local Anesthetic Failure Possible?

Even after giving the required anesthetic dosage for dental surgical procedures, multifactorial causatives lead to anesthetic failure. They are,

1. Variation in the Anatomy of the Teeth:

The dental surgeon cannot visualize the nerves directly. Only the approximate anatomic landmark would be accessible to anesthetize. In edentulous patients, that is, patients of older age with missing teeth in one or more areas, the landmarks may be obliterated to induce adequate anesthesia. In children and adolescents, especially in the growth spurt stage, the landmarks may vary slightly from individual to individual. In some patients, due to excess buccal pad of fat or thicker mucosal lining in the maxillary or mandibular areas (where the anesthetic needs to be given), the efficaciousness of anesthetic to act directly in that area injected tends to reduce. Hence for multiple causes varying from person to person, anatomic variations in the oral cavity pose a challenge to the dentist to inject an adequate amount of anesthetic directly.

2. Chronic Alcoholism and Smoking:

Chronic alcoholics are individuals who consume alcohol at least once daily or even those individuals with an increased frequency of alcohol intake in a week from a prolonged period. Patients often do not mention the detrimental habits of smoking, tobacco or quid chewing, or chronic alcoholism to the dentist, which may complicate the risk of anesthetic failures. This warrants a thorough medical history from the patient before starting a surgical procedure. As the local anesthetic mainly acts by inhibiting peripheral nerve conduction, the alcohol content consumed is certainly known to interfere with a room of local anesthetic, slowing its mechanism considerably.

In chronic alcoholics with liver damage and multi-organ damage, the consequences of alcohol, even mistakenly before or after a procedure, would be life-threatening. Especially prior to a dental surgical procedure, the doctor avoids forewarning these individuals to avoid alcohol and smoking habits (if present) 24 hours before and preferably for up to one week till the area surgically operated heals well. Smoking similarly alters the healing period of post-extraction sites and can cause dry socket,gingivalis bleeding, inflammation, and halitosis.

3. Iatrogenic Errors:

The dentist should avoid operator-based errors (as the nerves cannot be directly visible and approximate anatomic landmarks can only be visualized externally) like depositing the solution into a blood vessel or deep tissue or space. Another major reason is not being able to give an adequate amount of anesthesia, so the patient may not feel numb adequately for the operator to proceed ahead with the procedure painlessly.

4. Anxiety or Apprehensiveness of the Patient Itself:

These patients may raise fears about the dental procedure, making the dentist difficult to operate on. This is especially true in dental phobias, meaning fear of dental procedures or distinctive dentists. These patients can be calmed down by adopting voice control and showing them the difference between an anesthetized area and a non-anesthetized area to make them understand. Explaining the procedure in detail can make the comprehensive patients also alleviate their fears to an extent.

5. Issues With Anesthetic Solutions:

There will be a risk of anesthetic failure if there are storage-related issues with the anesthetic solution, such as indirect exposure to sunlight or heat instead of storing it in a cold environment. Expired anesthetic solutions also cannot act properly, leading to failure, and such errors should be avoided by the dental operator.

6. Certain Genetic Syndromes and Sodium Channel Disorders:

Some examples of resistance to local anesthesia are genetic defects pertaining to sodium channels in the body, tetrodotoxin-resistant channels, mutations, certain anemias, or specific syndromes like the Ehler Danlos syndrome associated with joint hypermobility. In these cases, the dentist should modify the dosage and technique (like the intraligamentary or periodontal ligament anesthesia for usually one or two single-rooted teeth) until the patient's pain is tolerable.

Inflammation - This is a major impediment to the success of local anesthesia. The pharmacodynamic and pharmacokinetic activity of the anesthesia circulating for a specified period in the localized area is affected. This is attributed to the hypothesis of inflammatory acidosis that would potentially occur in people suffering from systemic diseases or inflammatory disease or even in people suffering from oral inflammatory lesions. The interaction to the lipid bilayer is impacted, and the excitability threshold and the Ph of the site are lowered in these inflammatory conditions leading to anesthetic failure. Also, the acidic conditions of the infected or pus-filled area hinder the mechanism of action and passage of the anesthetic molecule to the pulp or the root canal of the tooth to be anesthetized.

In these cases, the dental surgeon may consider preoperative antibiotic prophylaxis to minimize or reduce the source of infection and then choose to operate. In patients suffering from localized dental-related inflammation like apical periodontitis, periodical abscess, gingival abscess, etc., the anesthetic time to produce the effect may be prolonged for the same reason.

Conclusion:

Though iatrogenic errors may be possible by the dental surgeon, they may not be the reason for anesthetic failure. Consideration of the patient's anatomic landmarks, systemic and oral conditions, habits, and anxiety before the procedure will help prevent local anesthetic failure in the dental setting.