Deep inside the mouth often referred to as the oral cavity; there is a basket weave of muscles, arteries, nerves and veins which perform their function in human physiology like a well tuned Suisse watch. Any tinkering or injury is sure to result into symptoms ranging from minor to clinically significant which may need the skills of a well trained and experienced dentist. Trauma to any part of this entire integrated network can as subtle and varied as during a meal, kidding around as so often done by children, the natural course of growing anatomy or while having dental work done.

To add insult to injury, there are anatomical variances from on person to another. These, arteries, veins, nerves and muscles are so closely platted, that dentists must be given credit when administering local anesthesia because there is literally only a few millimeters with which to accurately direct the needle, bearing in mind that as the needle advances through the tissue before gently touching bone, there are minor deflections (of the needle) which have to be factored in.

According to Dr. Stan Malamed's Hand book on local anesthesia, which is considered the "bible" for most dentists, states that a slow injection is by far the preferred way to avoid any mishaps. Because of the tight maneuvering through the maze of integrated net work of arteries, nerves, veins and muscle, if an error is made the patients feels it instantaneously and a slight correction can be made by slightly withdrawing and redirecting. Were it a rapid injection the needle would have already penetrated and exited the muscle or vein and the patient pays the price the next day.

The counter argument is that if the dentist can complete the injection as quickly as possible the patient is free of the needle. Nothing could be further from the truth since the variances in the pH of the local anesthetic and that of the tissue is too great to allow a smooth transition. One should also bear in mind that at this slow speed (1.5 minutes) the local anesthetic is actually numbing the tissue ahead of the needle.

Some dentists have chosen to use an automatic device which is programmed to deliver at the rate for any given patient. Dentists who use these mini computers admit that patients say they felt nothing. This is a win-win situation because the dentist can start to work right away and avoid having to give another injection before rushing off to another room. You do have their undivided attention form start to finish. This is the normal procedure they are taught in dental school. This can be a warning to the patient if they see the dentist darting from room to room, it will be a bad "hair day", as sure as they are little green apples.

When a certain muscle is penetrated, invariable a condition called a trismus will develop. A trismus is defined as a motor disturbance of the trigeminal nerve, especially spasm of the masticatory (chewing) muscles, with difficulty in opening the mouth to the full extent. Although post injection pain is the most common local complications of local anesthesia (due to hurry and speed), trismus can become one of the more chronic and complicated problems to manage. Some dentists also develop the habit of swiping the diaphragm of the cartridge with an alcohol or cold sterilizing solution cotton swab. A residue of these solutions may diffuse into the tissue during injection, and may produce irritation to the muscle which adds to the discomfort and or the trismus. Bleeding is another cause. Large volumes of blood can cause irritation, which leads to muscle dysfunction as the blood has a tendency to be resorbed. A low grade infection can add to the severity of the trismus.

Less is best and most dentists will try for as few injections in the same general area. Excessive volumes of local anesthetic ("an extra one for the pot") is a bad practice since tissue around the teeth are taught. Excessive volume will cause tissue expansion which again will lead to the severity and length of enduring a trismus. Some of the newer more effective local anesthetic solutions are now supplied as double strength, therefore, where it normally took one cartridge to do a procedure, one half is now required. For the patient it is far better to toss the left over rather than to use it all, for the reasons mentioned above. It makes good sense to follow this habit since using it all will cause the unnecessary discomfort of distention and swelling around the area.

In an acute (sudden) phase of a trismus, pain produced by bleeding, leads to muscle spasm and limitation of movement. The chronic or long lasting, phase usually develops if treatment is not begun immediately. The inability to open one's mouth widely is the result of the hematoma, fibrosis and eventually scar contraction. Infection may also produce reduced ability to open the mouth widely, due to pain, increased irritation and scarring. In extreme cases physio-therapy may be necessary.

The above incidences of trismus are quite common when a block is given. Fortunately, the majority are resolved in a few days. You should request a slow injection over a period of 1.5 minutes and also excessive shots are being avoided. Contrary to popular opinion, a dentist can increase patient load by 4 -5 more per day, if the time is spent completely with one patient from start to finish, rather than the perceived popular idea of rushing from operatory to operatory.

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