It is normal for a patient using an aligner for the first time to have some inconvenience as the aligners won’t exactly match the position of their teeth. This is normal. Ideally, aligners should fit tightly at first, then loosen up gradually as the teeth move into the desired position.
Front to back - First insert the aligner on the anterior teeth; then push the tray down over the posterior teeth. This technique is useful when the anterior teeth are excessively slanted forward or excessively crowded. Back to front - Insert the aligner on the posterior teeth first; then push the tray down over the anterior teeth. This technique is useful when all of the teeth are relatively straight. Side to side - Side to side technique can be used when the posterior teeth are excessively slanted towards the tongue. Insert one side of the aligner first, then come forward to insert the anterior teeth. Lastly press down on the other side. Anterior then toward the tongue or toward the cheek - Use this technique when the teeth are widened either lingually (toward the tongue) or buccally (toward the cheek). First insert the aligner on the anterior teeth. Then push the tray down lingually, if the teeth are widened lingually or buccally, if the teeth are widened buccally.