The bone graft was retrieved by making a continuous osteotomy line with a cylindrical and a round bur at the lateral part of the mandible, with a uniform size of approximately 15 × 25 mm (Fig. 1c, d). The bone block containing mainly cortical bone was then gently separated from the mandible using a raspartorium. The block graft was covered with a saline-moistened gauze until used. In the PRF group, the donor site was covered by 3–4 PRF membranes while no adjunctive measures were performed in the control group [28], before suturing (4-0 Vicryl TM, Ethicon ®, Johnson & Johnson, NJ, USA).

Lateral bone augmentation

An incision was made on the top of the alveolar crest with 1–2 releasing incisions at the adjacent teeth before the mucoperiosteal flap was elevated. The previously collected bone block graft was adjusted to the contour of the bone at the recipient site and fixated with 1–2 osteosynthesis screws (Walter Lorenz® Midface System, Biomet Microfixation, Jacksonville, USA) (Fig. 1e). The remaining part of the autogenous bone graft was milled in a bone mill (Roswitha Quétin Dental-Produkte, Leimen, Germany), and autogenous bone graft particles were packed around the bone block. In the PRF group, three PRF membranes covered the grafted area (Fig. 1f, g). In the control group, the grafted area was covered by deproteinised bovine bone mineral (Geistlich Bio-Oss® Spongiosa Granules, Geistlich Pharma AG, Wolhusen, Switzerland) and two layers of a resorbable native bilayer collagen membrane (Geistlich Bio-Gide®, Geistlich Pharma AG, Wolhusen, Switzerland). Finally, the periosteum of the mucoperiosteal flap was released by an incision to secure tension-free primary wound closure before suturing (4-0 Vicryl TM, Ethicon ®, Johnson & Johnson, NJ, USA) (Fig. 1h).

Antibiotics, analgesic and plaque control

All patients received oral amoxicillin (1000 mg), metronidazole (500 mg), ibuprofen (400 mg), paracetamol (1000 mg) and methylprednisolone (32 mg) 1 h before surgery. Just prior to the operation, a mouth rinse with 10 ml 0.12% chlorhexidine digluconate was performed.