"Hey, Doc! My jaw clicks sometimes. Why does it do that?" or "My teeth are sensitive when I brush or drink cold liquids. It's not always the same place, though. How come?" "Sometimes when I'm eating, I get a pain in my ear. I think it might be actually my jaw joint though."
These are all complaints I get regularly. The jaw joints are a very complex mechanism and there are many factors involved with what is know as TMJ Dysfunction, TMJ Syndrome or just TMJD. The cartilage disk in the joint can become worn and the ligaments holding it become stretched, leading to various problems which in early stages can elicit the kinds of complaints I mentioned here as well as others.
So what is a nightguard? A nightguard (or more accurately an occlusal guard) is a plastic appliance made from an impression taken by a dentist that is worn over the teeth to protect the teeth from grinding action. This grinding (or sometimes clenching) is often done while a person is asleep, hence the term nightguard. However, it does not have to be worn only at night. It can be worn any time. You would not want to wear it while around other people or while eating, however.
The grinding of the teeth, known as bruxing, causes excess pressure on the teeth and jaw joints and can be responsible for the abnormal wear of teeth and the joint cartilage. When you sleep, the nerves responsible for controlling the amount of pressure you put on your teeth when you close your jaws are inactive, so you can put up to ten times more pressure on your teeth asleep and not even know it.
Pressures on the joints cause abnormal wear of the cartilage disc between the jaw bone and the skull. The ligaments holding this disc in proper position can also get stretched. The wear of the disc itself and stretching of the ligaments causes the disc to lose proper shape and position resulting in clicking or popping noises in the joint, and eventually pain. If these problems become severe enough, a simple preventive measure like a nightguard will not solve the problem and it may require crowns, bridges and even surgery to correct the problem.
There are also alternative healing modalities that are centered around realigning muscle and joint function, but again, these measures would need to be applied before significant anatomical changes have taken place.
Pressures on the teeth cause abnormal wear on the teeth themselves, as well as stress to the nerves within the teeth. When the teeth wear, it can be either at the point of contact between opposing teeth or where the enamel is thinnest at the gum line. This wear at the gum line from grinding pressure is the result of microscopic "bending" of the teeth and is known as abfraction. This is one of the causes for the dished out sensitive areas that can appear at the gum line of teeth in various parts of the mouth. The wear at the point of contact is usually less serious, but can result in the need for bonded fillings, or sometimes crowns if a fracture develops in the tooth.
The stress to the nerves within the teeth leads to "aching" teeth and eventually to the need for crowns, root canals (removal of the nerve) or even extraction if accompanied by severe damage to tooth structure.
Nightguards are preventive appliances and can help to mitigate minor symptoms related to early problems from grinding or clenching habits. They are not, however, a treatment solution for the problem and if grinding or clenching persist or have cause significant symptoms already, treatment solutions should be discussed with your dentist.