A 5-year-old shild has sustained a trauma. Objectively: the crowns of the 51st and 61st teeth are shorter then their adjacent ones. The mucosa surrounding the 51st and 61st teeth is hyperemic and swollen. X-ray imaging shows the periodontal fissure to be absent in the apical area of the 51st and 61st roots, 51st and 61st roots apexes are submerged in the spongy bone of the body of the lower jaw. Choose the optimal treatment.