Reconstruction of Deficient Interdental Papilla Using Stem Cells vs Physiological Saline

One injection will be given at each papilla set with the volume of 0.1mL with 2.0 x 10⁶ cells per syringe at every visit. A total of 3 injections will be given at the interval of 6 weeks, with a total of 6.0 x 10⁶ cells for each interdental papilla at the end of the 3 injections. Every injection starts with locally application of local anesthetic. For the control group, participants will be injected with 0.9% sodium chloride after locally application of local anesthetic