Why Do Wisdom Teeth Become Impacted?
The reasons why wisdom teeth become impacted is that there is an obstruction which is preventing them from fully erupting. The two causes of an obstruction are the adjacent tooth and also simply that there is not enough room in the jaw bone to accommodate this extra tooth. Wisdom teeth are the most common teeth to become impacted because they are the last teeth to come through when all the other adult permanent teeth are already through. By the time the wisdom teeth start to come through which is on average between the ages of 16-21 years old, there is very little room left for them to squeeze through. Imagine trying to squeeze your foot into a shoe which is one size smaller than your normal shoe. You have to force your shoe on and once it is on, it quickly becomes uncomfortable resulting in sores and ulcers. This is exactly what happens with a wisdom tooth which is impacted.
Problems with impacted wisdom teeth relate to infection of the operculum, decay in the wisdom tooth, decay in the adjacent teeth, food packing and gum disease.
Treatment of the impaction is by extraction. In dentistry, we classify different types of impaction. These are horizontal impaction, buccolingual, mesioangular, distoangular, vertical and others. This is known as Winters Classification. Winters Classification gives you a description of the angulation of the wisdom tooth in comparison to the remaining molars in front.
There is also another type of classification which also describes the impaction.
The Pell and Gregory Classification
The Pell and Gregory Classification gives the position of a third molar in relation to the mandible so the division is a Class 1 or Class2 or Class3.
The Pell and Gregory Classification is useful because it also gives the depth of the impaction as a level. The division here is level A, B, or C.
It is useful to be able to have a classification for impacted wisdom teeth. A classification can give an indication and description of the impaction which can help to determine how difficult or easy the extraction will be. This is important in order to decide if the extraction of the wisdom teeth can be done as a routine procedure in the surgery or if it warrants a referral to the dental hospital. If possible, the extraction should always be carried out in the dental surgery because hospital referrals have lengthy waiting lists. You can easily be waiting for a year to have your wisdom teeth out in hospital. It’s also quite inconvenient because once the dentist has written a referral request to the hospital, the patient will need to have further x-rays carried out. Once these have been taken, the patent has to attend for a hospital initial consultation. This means more waiting around and it happens on a frequent basis that hospital appointments get cancelled at the last minute. I have seen patients waiting for over one and a half years to have their wisdom teeth removed.
Another important function of wisdom teeth classifications is that it can give an idea of complications afterwards. So if a wisdom tooth is very deep and lying horizontal, there is a very increased risk of the dentist causing nerve damage during it’s extraction. The two nerves that can be affected are the lingual nerve and the inferior alveolar nerve. Damage to the lingual nerve causes a disturbance to the sensations in the tongue so that taste may be altered or damaged temporarily or permanently. If there is damage to the inferior alveolar nerve, this will cause temporary or permanent altered sensation to the lower lip and the skin on that side of the face right up to the ear. Depending on the amount of damage, it is rare that the nerve recovers because nerve cells do not regenerate. It is also not uncommon that during a wisdom tooth extraction the nerve is bruised but not actually severed. In these cases, the altered sensation is short lived. It may last for a week or even a few months but as the nerve has not been actually severed, normal function will reappear.