Randomization
Randomization was performed by allocating each of the two recessions to one of the two techniques A (right side: FGG, left side: liquid PRF with FGG) or B (right side: liquid PRF with FGG, left side: FGG). The sequence of allocation was performed using a computer random generator (allocation ratio of 1:1). The sequence of allocation was concealed in opaque sealed envelopes, which were identified by the initials of the patient's name. Each patient's envelope was opened immediately before surgery.