A method is for manufacturing a shell. The method includes forming the shell over a mold. The mold includes a first portion and a second portion. One or more weakened regions of the mold are associated with the first portion and the second portion. The method further includes causing the first portion of the mold to separate from the second portion of the mold via the one or more weakened regions. The method further includes removing the first portion of the mold from the shell. The method further includes removing the second portion of the mold from the shell. The shell is configured to be worn in a mouth of a patient.

A method is for manufacturing a shell. The method includes forming the shell over a mold. The mold includes a first portion and a second portion. One or more weakened regions of the mold are associated with the first portion and the second portion. The method further includes causing the first portion of the mold to separate from the second portion of the mold via the one or more weakened regions. The method further includes removing the first portion of the mold from the shell. The method further includes removing the second portion of the mold from the shell. The shell is configured to be worn in a mouth of a patient.

A mold is for thermoforming a dental appliance. The mold includes a first section of the mold and a second section of the mold. The second section includes a feature having a complex shape, an undercut, or a bite edge. The mold further includes a weakened region that joins the first section to the second section. The weakened region is breakable, deflectable, or 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 the dental appliance is formed over the mold. The first threshold force is less than a second threshold force that would damage or permanently deform the dental appliance.

A mold is for thermoforming a dental appliance. The mold includes a first section of the mold and a second section of the mold. The second section includes a feature having a complex shape, an undercut, or a bite edge. The mold further includes a weakened region that joins the first section to the second section. The weakened region is breakable, deflectable, or 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 the dental appliance is formed over the mold. The first threshold force is less than a second threshold force that would damage or permanently deform the dental appliance.