Clenching and grinding of the teeth are extremely destructive dental habits. Unlike normal chewing where the teeth are cushioned with portions of food, clenching and grinding involve one tooth surface against another, leading to the propagation of cracks in teeth and to wearing down of the chewing sides of the teeth. With the accumulation of cracks, teeth may become sensitive and portions of teeth may break off, leading to the necessity of crowns. Over time, the wear may actually extend to the pulps of the teeth thus requiring root canals or extractions.
Understandably, treatment of worn teeth can be both expensive and involved so prevention of the clenching and grinding habit is obviously desired. Since it is a habit, it is most often done unconsciously and during sleep, making it extremely difficult to correct. However, one way to lessen the destructive effects of the habit is by wearing a cushioned splint, also known as a BITEGUARD, over the teeth. 
This does not correct clenching and grinding but keeps the hard tooth surfaces from contacting each other.
If you are aware of grinding, especially during sleep, a nightguard would be wise to wear. On examination, if tooth wear is evident, a biteguard might be suggested to lessen the long-term damage of clenching and grinding.