Why cannot the Dentist get my Teeth Numb with Local Anesthesia

Getting a Tooth numb before any procedure in the dental clinic is one of the main things which every Dentist would like to get and all the patients would feel comfortable with, but there are some or shall I say many situations when your Dentist cannot get your teeth numb even after multiple doses and injections of Local Anesthetic solutions like Lidocaine, Novocaine (rarely used now days), lignocaine, atricaine etc.

According to some studies, the failure rate of Local anesthesia is almost 5-15% of the total number of injections given to patients by dentists. There are various factors involved in the success and failure of Local anesthesia which is not always the fault of the Dentist.

I personally faced many such situations where patients had all the signs and symptoms of local anesthesia but the particular tooth which was to be operated on was not Numb this condition is called as “Hot Tooth” which I will explain in detail in another post. And in other conditions there was no numbness or effect of anesthesia at all the reasons to which I will be explaining now.

Inferior alveolar Nerve Block Technique

Why your teeth are not getting Numb after multiple injections by your Dentist:

There are multiple factors which play a major role in success or failure of Local anesthesia and I am going to explain in brief some of the main reasons which might lead to your tooth not getting numb.

Variations in Anatomy:

This is one of the major factors affecting the success of Local anesthesia because the anatomy of each individual is different from others. And giving a local anesthesia is depending on the landmarks as the dentist cannot visualize the nerve. In some patients there is excess fat over the area (inf alveolar nerve block). And then there is difficulty of missing landmarks in old patients without teeth or children who are in growing stage where the landmarks are different and injecting the anesthetic liquid in the right location is difficult.

Infection or Inflammation:

In case of local infections in the area like Chronic periapical abscess or Apical periodontists the effect of local anesthetic effect is not seen to the tooth which is affected as the acidic nature of the pus hinders the passage of the Local anesthetic agent to the Pulp of the tooth. This is the reason why it takes more time and solution for the anesthetic to take effect and in some severe cases a dose of antibiotic therapy is necessary to decrease infection.

Anxious or Apprehensive patients:

Some patients who have come for the first time to a dental clinic or apprehensive patient who have fear of the dentist (Dental Phobia) can move while injecting the liquid and this can lead to wrong location of the anesthetic solution. In these patients it is important to make them understand that the effect has started by showing the difference between the anesthetized side and the normal side. Calming down the patient by explaining about the procedure and if needed spraying Local Anesthesia on the Injection site can help decrease the pain while injection.

Chronic Alcoholics:

This is one of the common reasons seen in middle age men, who are also chronic alcoholics who consume alcohol at least once a day. It requires double the dose of Local Anesthesia to get the Block or infiltration working and it is one of the common causes which I have personally faced in my clinical Practice in India. It is important to ask the patient if they are alcoholics and every patient should mention to their dentist if they are. In some people addicted to Ghutka and Drugs face difficulty in getting anesthetized and LA effect is seen less in such patients.

Error by Dentist:

Because of the lack of visibility of the Nerve where the local anesthesia should be deposited, sometimes the agent is deposited either too deep into the tissue or space or is injected into the blood vessel which is circulated into blood and its effect is not seen here. Giving less amount of anesthetic solution is also a reason for lack of numbness in the area.

Anesthetic Solution:

There can be a problem with the Anesthetic solution which can be the cause for lack of anesthesia. The various problems with Anesthetic solution are expired LA agent, agent kept in Sunlight or hot place instead of cold place like a fridge, duplicate anesthetic solution etc. (For Dentists) It is always better to opt for well known brands for Local Anesthetic solution which are tried and tested.

People with Ehlers-Danlos Syndromes and Red Hair:

There are studies suggesting that people who are suffering with Syndromes like Ehlers Danlos Syndrome which is a condition affecting Joints leading to Hyper mobility, in these patients the effect of Local anesthesia is less and they are insensitive to LA. People who are born with red hair also face difficulty in getting anesthetized which is based on an Article published in American dental Association states.

These are the various conditions in which a Patient in a Dental clinic cannot get anesthetized by Local Anesthesia which can be easily corrected with the help of many simple procedures first of which is to identify the cause of the failure. In some cases when a single tooth is not getting anesthetized Intra-ligamentary injection works wonders as I have experienced in my practice.

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