Enamel loss can be easily restored by covering the tooth with a layer of white composite filling material, or sometimes in severe cases a covering like a crown or a veneer. This is only done once the cause has been established and steps to help reduce this from happening again put in place.
Things such as over brushing or brushing too hard, using very abrasive toothpaste regularly, grinding or clenching of the teeth or consuming highly acidic foods on a regular basis can cause tooth or enamel loss.