We can certainly use an older impression if you prefer. We just need to make sure that:1. The impression is relatively recent. We prefer anything within a year old and preferably within 6 months old2. The impression must be accurate. Nothing can have changed since the impression was taken, including but not limited to alignment treatment, crowns, bridges, implants, and/or extractions.Please note that we can only ensure the fit of the guards to the model/impression provided. If the impression/model differs from your mouth, we cannot refund the guard if it fits the model.If you would like to use your guard, contact a enCore support member to let us know and we'll help make the arrangements.