A severe underbite in an adult often requires surgery to fix. An underbite can cause many problems for the patient since the lower jaw may be much smaller or the teeth don't meet correctly. The mouth naturally attempts to get a proper and aligned bite causing the jaws to hold in uncomfortable positions causing pain and the inability to chew properly. The joint in the jaw may pop or even lock out of alignment. In these cases, surgery is the only option.
It's likely for a patient with underbite to be put into braces for several months to a year before surgery. This is done to align the teeth as much as possible to prepare them for the movement of the mandibular jaw bone to align with the top jaw.The operation is almost entirely carried out from the inside the mouth to minimise visible scars on facial skin. A cut is made through the gum behind the back teeth to gain access to the jawbone. The jawbone is then cut on an angle in order to slide the jaw bone forward. Titanium screws and plates are then placed to hold the jawbone in its new position. The gums are then sewn back together with dissolving stitches that will disappear after a week or so.
After the Surgery
This is a painful surgery and you will be on pain medications for several days. Don't be surprised when you look in the mirror and see your lower face looking twice its normal size. It will take time for this swelling to dissipate. Bruising on the jawline is very common. You will be given several days to just rest and heal. You will be on a liquid diet during this time. Depending on the severity of the problem, your jaw might be wired shut but even if it isn't, you will not be able to open your mouth at first. In the process of the surgery your jaw is laid wide open. This procedure tends to atrophy the jaw muscles and you will have to retrain these muscles to open and close the mouth. Prepare to lose weight and be hungry often.
The Healing Process
Small elastics will be used to do some final adjustments to the bite while you are healing. You will be given rehabilitation and physiotherapy to bring the jaw back to regular working order. At first you will use small electrodes to spark nerve regeneration in the lower jaw. This is a pleasant process with little or no pain. However, there will be some pain in the process of teaching your jaw to open normally again. It is possible that it may take years for the nerves to completely regenerate and some nerve function may never return. This will not affect the normal operation of your jaw.
Eating will be a learning experience when you are able to chew again. Your jaw will be tender and weak. Chewing will take longer then usual. One rule of thumb, you should be able to get the circumference of three fingers lined up vertically into your open mouth. When you can do this you are most of the way rehabilitated. With time and patience you will have normal operation again.
Speaking From Experience
I understand that this surgery can be a very frightening prospect as I myself had this procedure done seven years ago. However, faced with the issues an underbite can produce as you age, I urge you to seriously consider tolerating the small amount of pain and discomfort a mandibular osteotomy will cause you. The alternative will bring more pain and discomfort over a much longer period, perhaps even a lifetime of eating, chewing and speaking issues associated with an underbite. A mandibular osteotomy will not only help your daily living but it will have a profound effect on your self esteem.