What causes teeth to break?

Answer
Breaking can result from internal causes like extreme mastication (which usually only results in chipping), gum disease (gingivitis) which undermines root structure, making teeth susceptible to cracking (under torque) and multiple cavities (from poor hygiene or systemic deficiencies) which weaken the remaining enamel, thus leading to fissures and separations. External causes include falls, fights and vehicle accidents. Any concentrated or massive force on the teeth from front or side can chip, crack or dislodge a single tooth or many teeth. Until the 1930s most people who lost teeth learned to live without them or had "false teeth" crafted for their upper and/or lower jaws. Today orthodontic surgeons can implant titanium posts to which skilled dentists can affix life-like enamel crowns.