Multiple techniques for detecting defects in customized dental appliances are disclosed. In one technique, processing logic obtains one or more images of a customized dental appliance, obtains a digital model associated with the customized dental appliance, and identifies an area of the one or more images that comprises a representation of the customized dental appliance. Processing logic then registers the one or more images to the digital model, compares the area of the one or more images of the customized dental appliance with the digital model of the customized dental appliance, determines a difference between the area of the one or more images that comprises the representation of the customized dental appliance and the digital model of the customized dental appliance at a region, and determines whether the difference satisfies a defect criterion.