With respect to marginal bone loss, it could be shown that there were no significant differences when comparing dimension of bone loss between test and control groups. The study of present research data shows, to the best knowledge of the authors, no other RCTs about tissue thickening with PRF and peri-implant bone loss. However, several studies focused on mucosa thickening with tissue grafts and assessed the marginal bone loss around implants. Hehn et al. and Wiesner et al. achieved a stable mucosa thickening by augmenting the initial situation with a tissue graft taken from the palate [12, 25]. Whereas Hehn could show a reduced bone loss after 12 months, Wiesner’s results show no difference in bone loss between test and control sides.

A second technique is the use of membranes. Lai et al. postulated a successful, long-term stable augmentation by using an acellular dermal matrix (ADM group increased by 3.10+/−0.64 mm at 12 weeks, control group increased by 0.30+/−0.50 mm) [13]. Puisys et al. focusing on the coherence of membrane tissue augmentation and peri-implant bone loss show similar results. They came to the conclusion that initial soft tissue augmentation with an allogenic collagen matrix resulted in a long-term stable thickened mucosa. Furthermore, the bone loss around implants was significantly less when implants were placed in naturally thick tissue than in thin tissue. Bone loss 1 year after surgery around implants with a thin mucosa was 1.22+/−0.08 mm bone loss mesially and 1.14+/−0.07 mm distally. Around implants placed in a thick mucosa, it was 0.24+/−0.06 mm mesially and 0.19+/−0.06 mm distally. The attempt to thicken thin mucosa with an allogenic membrane resulted in highly reduced bone loss (0.22+/−0.06 mm mesially and 0.20+/−0.06 mm distally after 1 year) [11].

One limitation of this study is the standardized radiographic evaluation. This technique allows information about the peri-implant bone only on the mesial and distal but not on the buccal and lingual side. However, this fact is limiting most present studies focusing on the peri-implant bone level [5, 26]. Yet, the main limitation of this study is the small number of patients. For this reason, these findings cannot be generalized to soft tissue augmentation with PRF on this study alone.