Hesperian Health Guides
How to Inject
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For a good, safe injection, remember these 5 things! Local anesthetics are the only injections given in the mouth. Learn more about injecting antibiotics.
- Do not inject local anesthetic into an area that is swollen. This can spread the infection. Also, pus inside the swelling stops the local anesthetic from working properly. Instead, treat the swelling first and take out the tooth later.
- If the person has a heart problem, do not inject more than 2 times in one visit. Also, it is best not to use an anesthetic with epinephrine on persons with heart problems. Use lidocaine only, or mepivacaine 3% only.
- Before you push the needle under the skin, be sure its pointed end is facing in the correct direction.
Before you inject the local anesthetic, wait a moment to see if any blood enters the syringe. (Note: only an aspirating syringe will do this.)
Pull back on the plunger. If blood comes inside, it means you have poked a blood vessel.
Pull the needle part way out and gently move it over to a different place.
If you inject local anesthetic into the blood vessel, there will be more swelling afterward, and the person may faint. If the person faints:
- Lay him on his back.
- Loosen his shirt collar.
- Lift his legs so they are higher than his head.
- Be sure your syringe and needles are clean and sterile.
Do not pass an infection from one person to another by using dirty needles.
FOR GLASS SYRINGES:
Boil the syringe and needle in water for at least 30 minutes in a covered pot. It is also a good practice to boil your metal syringe.
FOR METAL SYRINGES:
- Use a new cartridge for each person who needs an injection. Do not use local anesthetic from a cartridge that you have used on another person.
- Use each disposable needle only 1 time and then throw it away in a disposal box. If you must reuse a needle, replace the cap very carefully and put the needle in a safe place (such as a pan of bleach solution) until you are ready to clean and sterilize it.
come out against
the bone, where
the nerve is.
Injecting the upper teeth
Inject local anesthetic near the root of the tooth you want to treat.
Front teeth have one root. Back teeth have more than one.
For a tooth to become completely numb, the local anesthetic must touch the small nerve going to each one of its roots.
- First decide where to inject. Lift the lip or cheek. See the line that forms when it joins the gum. The needle enters at the line where the lip or cheek meets the gum.
Push the needle in, aiming at the root of the tooth. Stop when the needle hits bone. Inject about 1 ml of local anesthetic (½ of a cartridge).
Pull the needle part way out and move it over to the next root. Inject again.
If the tooth is to be taken out, leave .25 ml for the next step.
If you are taking out a tooth, also inject the gums on the inside.
Ask the person to open wide. Inject the remaining anesthetic (.25 ml) directly behind the back tooth that must come out.
One injection can numb the gum behind the 6 front teeth. Inject into the lump of gum behind the middle front teeth.
(Note: This injection hurts! It may help to use ‘pressure anesthesia.’)
- Wait 5 minutes for the tooth to become numb.
Injecting the lower teeth
When you block the nerve, it affects all of the teeth as well as gums on that side. However, it takes practice to do this successfully. Ask an experienced dental worker to help you learn how to give this injection properly.
Stand in such a way that you can see clearly where you need to inject. Ask the person to open wide.
First feel for the place to be injected.
Put your thumb beside the last molar tooth. (Wash your hands first!) Feel the jawbone as it turns up towards the head. Rest your thumb in the depression there.
Press against the skin with the end of your thumb.
The skin forms a ‘v’ shape. Your needle must go into the ‘v’. Hold the syringe on top of tooth number 4 and aim the needle at the ‘v’.
Push the needle in until it hits the jawbone, (about ¾ of the length of a long needle). Pull back on the plunger of the aspirating syringe to check for blood.
Inject 1.5 ml of local anesthetic (¾ of a cartridge).
Try to feel your way: If you hit bone too early, pull the needle part way out and move it over so that it points more toward the back of the mouth. Try again.
If you do not hit bone, the needle is too far back. Pull it part way out, and point it more toward the front. Push it in again.
Give a second injection BESIDE the back teeth.
If you are going to fill or remove a back tooth, inject beside that tooth, where the cheek joins the gum.
Inject .5 ml of local anesthetic (¼ of a cartridge).
This injection is not needed for front teeth. It is enough to block the main nerve.
- Wait 5 minutes for the tooth to become numb.