The part of your tooth above the gum line is called the crown. This part of your tooth is covered with enamel which is the strongest substance in the human body. In some instances, a tooth becomes weakened and may become more susceptible to breakage or further damage or decay. This can occur when a tooth is cracked or broken. It can also happen when a tooth has a very large filling or when it has had the nerve removed through root canal therapy. In these scenarios, the tooth is no longer as strong as it was originally and your dentist may recommend a dental crown as a general dentistry treatment to restore its strength.