Afterward, a trichotomy was performed in the nasal dorsum and, after disinfection of the experimental region using Betadine (MEDA Pharma®, Madrid, Spain), a sagittal incision was carried out. The skin and the periosteum were dissected and shifted laterally to expose the nasal bone. Antrostomies, 4 × 4 mm in dimensions, located about 3–4 mm laterally to the midline and about 10 mm in front of the nasal-frontal suture, were prepared bilaterally grinding the bone with a round diamond bur (Fig. 1b), under conspicuous irrigation with saline.

The sinus mucosa was elevated from the bone walls with a small elevator (Bontempi®, San Giovanni in Marignano, RN, Italy), and the space obtained was grafted with a collagenated cortico-cancellous porcine bone (OsteoBiol Gen-Os, Tecnoss®, Giaveno, Italy; 250–1000 μm). The autogenous bone particles were placed in the antrostomy and the subjacent region at the randomly assigned sites (treated sites; Fig. 1c, d). Collagen membranes (OsteoBiol® Evolution 0.3 mm, Tecnoss®, Giaveno, Italy; Fig. 1e) were placed to cover the antrostomies both at the treated and untreated sites. Resorbable sutures (Vicryl®, Johnson-Johnson, New Brunswick, NJ, USA) were used to close both periosteum and skin (Fig. 1f).

Meloxicam (Normon®, Madrid, Spain) 0.2 mg/kg once a day for 7 days and Buprenorphine hydrochloride (Buprex®, Hull, UK) 0.02 mg/kg twice a day for 3 days were administered subcutaneously. The rabbits were kept in individual cages in controlled temperature rooms at the animal facilities of the University of Valencia. The monitoring of wounds and biological functions was performed for the whole follow-up.

The animals were euthanized using 50 mg/kg of sodium pentobarbital (Nembutal® Schaumburg, IL, USA).

The experimental region was dissected and fixed for 7 days at room temperature in formalin 10% and subsequently decalcified in Osteosoft (Merck KGaA®, Darmstadt, Germany). After decalcification, the specimens were washed in distilled water and included in paraffin. Sections of about 5 μm in width were prepared in a microtome (RM2245, Leica Biosystems, Wëtzlar, Germany). A section from the central region of the antrostomy was selected and stained with scarlet-acid fuchsine and toluidine blue and used for histomorphometric analysis.