A crown, or cap, is a means to restore a tooth that is heavily broken down. Dr. Wong recommends a crown when more than 50 (fifty) percent of the tooth is missing. If the tooth exceeds that number, then there is a greater risk of catastrophic fracture of the tooth when you bite.
The crown will give a 360-degree encirclement of the tooth preventing a fracture, whereas the filling will just rest on the tooth and does not provide the structural integrity to prevent the fracture.
One analogy I like to share with patients that a filling is similar to a wedge when placed in the center of the tooth. A small one will not do much due to large support from the robust, and large amount of tooth structure around the filling. Now, imagine the wedge is much larger, then when you bite, the filling will serve as an ax head to cleave the tooth in half because the amount of tooth structure is so small it can not resist the splitting force.
Veneers are a great way to cover intrinsic stains that can not be bleached, such as tetracycline staining or intrinsic stains acquired during the development of the tooth. People may also get veneers to straighten misaligned teeth. Veneers are more conservative than crowns and may also come in the no-prep variety which allows dentists to place a veneer without recontouring, or removing tooth structure.
A bridge is a procedure to replace a missing tooth, or multiple missing teeth when there is a tooth in front, as well as in the back of that space. These teeth will serve as supports to bridge the gap. We call these support teeth, abutments, and the fake teeth over the edentulous space, pontics. A bridge can also be made between implants where two or more implants can support three or more teeth.