Basics of local anesthesia: Dental assisting

Anesthesia plays a critical role in dental practice, and that's a good thing! Imagine going to the dentist and having a cavity drilled out or a tooth pulled without any anesthesia for pain control. You probably wouldn't want to go back. Luckily, local anesthesia helps patients stay comfortable during dental procedures and relieves some of the anxiety that's often experienced when anticipating a dental procedure.

As a dental assistant, you'll play an important role in promoting a safe and comfortable patient experience when local anesthesia is used.

The two levels of pain control commonly used in dentistry are topical anesthesia and local anesthesia. Topical anesthesia is applied directly to the surface of a specific area as an ointment, liquid, spray, or patch, and provides a temporary numbing effect before needle injections or minor procedures. On the other hand, local anesthesia is injected near a nerve to numb a wider area before more complex procedures like a tooth extraction or root canal.

Now, let's take a closer look at how local anesthetic works. Once it's injected, it diffuses through the tissues and the nerve and blocks its ability to transmit pain signals. The area becomes numb once the nerve is sufficiently permeated with the anesthetic agent. With time, the numbness wears off as blood flow gradually removes the anesthetic solution from the area and is absorbed into the body.

Now, each anesthetic agent has a specific time span.

Induction is the time it takes for complete nerve conduction blockage after injection; and duration is the length of time from induction until the nerve blockage is reversed and patient regains sensation.

The duration of action for short-acting anesthetics is about 30 minutes; intermediate-acting anesthetics last about an hour; and long-acting anesthetics usually last about 90 minutes. The duration of action can be prolonged by adding a vasoconstrictor to a local anesthetic solution. The vasoconstrictor slows the uptake of the anesthetic agent by narrowing the surrounding blood vessels, which slows down the blood flow around the injection.

Now, adding a vasoconstrictor to a local anesthetic isn’t always a good choice for every patient, especially those with a history of heart disease like angina, myocardial infarction, or uncontrolled hypertension. As the anesthetic is absorbed by the body, it can increase the heart rate, increase the force of contractions, and elevate blood pressure, putting a strain on the heart.

The vasoconstrictor can also interact with the medications a patient is taking, including thyroid hormones and certain antidepressant medications.

As a dental assistant, it's critical for you to remember to carefully review your patient's medical history at every visit and confirm all local anesthetic medications with the dentist before preparing them.

Now, there are different types of local anesthetic injections used in dentistry. The type you'll be preparing depends on the procedure and which nerves supply or innervate the specific area.

Let's start by talking about maxillary anesthesia, which has three types.

Local infiltration is used when the procedure involves just one tooth. This type of anesthesia can be used with maxillary bone because it's thin and porous nature allows the anesthetic solution to easily diffuse through the bone and reach the nerve endings that supply the tooth.

However, in situations where a larger area requires anesthesia, a field block is used when 2 to 3 teeth are involved, where the anesthetic solution is injected near a larger terminal nerve branch.

Lastly, nerve blocks, where the anesthetic solution is injected close to the main trunk of the nerve, can numb a whole quadrant of the mouth for bigger procedures.