Amalgam fillings are metal fillings and they are very strong. Despite being a very strong material, the forces in the mouth can be enough to break these fillings especially if one is grinding or clenching their teeth. The first picture above shows broken amalgam restorations.
These fillings are broken because the patient grinds his teeth. One can see how the tooth structure is worn as well.
A new composite resin restoration brings the tooth back to proper form and function. Although these new restorations will serve the patient well, they will also eventually fail unless the grinding habit is addressed. The treatment solutions may include a night guard and a bite adjustment to balance the forces on the teeth.