Clear aligners can fail for a variety of reasons. One common reason is poor compliance, meaning the patient does not wear the aligners for the prescribed amount of time each day. The aligners must be worn for at least 22 hours per day in order for them to be effective, and if they are not worn for this amount of time, the teeth may not move as planned. Another possible reason for failure is a lack of follow-up visits with the dentist or orthodontist, as these visits are important for monitoring the progress of the treatment and making any necessary adjustments to the aligners. In some cases, clear aligners may fail because the patient has severely misaligned teeth or a complicated dental condition that requires more advanced treatment. It is important to discuss any potential risks and limitations of clear aligner treatment with your dentist or orthodontist before starting treatment.