Mold including sections joined by a weakened region

A mold for thermoforming a dental appliance, the mold comprising:

• a first section of the mold;
• a second section of the mold, the second section comprising a feature having a complex shape, an undercut, or a bite edge;
• and
• a weakened region that joins the first section to the second section, wherein the weakened region is deflectable in response to a first threshold force to enable the first section and the second section to be removed from the dental appliance after a shell is formed over the mold to form the dental appliance, the first threshold force being less than a second threshold force that would damage or permanently deform the dental appliance.

A mold for thermoforming a dental appliance, the mold comprising:

• a first section of the mold;
• a second section of the mold, the second section comprising a feature having a complex shape, an undercut, or a bite edge;
• and
• a weakened region that joins the first section to the second section, wherein the weakened region is deformable in response to a first threshold force to enable the first section and the second section to be removed from the dental appliance after a shell is formed over the mold to form the dental appliance, the first threshold force being less than a second threshold force that would damage or permanently deform the dental appliance.