The objective of this proof-of-concept study was to investigate the effects of a new guided bone regeneration technique with a tissue engineering approach. This single cohort observational study evaluated the outcome of the leucocyte- and platelet-rich fibrin (L-PRF) Block for horizontal bone augmentation in the maxilla. The L-PRF Block is prepared by mixing a particulated biomaterial with chopped L-PRF membranes at a 50:50 ratio and adding liquid fibrinogen to glue all together. Horizontal augmentation was assessed linearly and volumetrically immediately after surgery and 5-8months later by matching consecutive cone beam computed tomography (CBCTs). Ten patients (mean age of 50.7years [±17.2]) representing 15 sites with horizontal alveolar deficiencies were included. Superimposition of pre-operative and posthealing CBCT scans showed an average linear horizontal bone gain of 4.6mm (±2.3), 5.3mm (±1.2) and 4.4mm (±2.3), measured at 2, 6 and 10mm from the alveolar crest, respectively. The volumetric gain was 1.05cm3 (±0.7) on average. The resorption rate after 5-8months was 15.6% (±6.7) on average. L-PRF Block may be a suitable technique to augment deficient alveolar ridges.