The Ethics Committee for Animal Research of the Veterinary School of the University of Teramo (Teramo, Italy) approved the study protocol, which followed guidelines established by the European Union Council Directive of February 2013 (R.D.53/2013).

A total of 36 implants were used in the present study. Implants had different macro-geometries and surfaces and they were divided into three groups of 12 implants each.

Twelve implants, belonged to group A, were 4.1 mm in diameter and 10 mm in length, with a smooth neck of 2.8 mm and SLActive sandblasted and acid-etched surface (STRAUMANN Basel, Switzerland) (Fig. 1).

Twelve implants, belonged to group B, were 3.8 mm in diameter and 11 mm in length and showed a small thread design, a smooth neck of 0.25 mm in the most coronal area, a micro-threads collar of 3.25 mm in length and laser-treated surface (GEASS s.r.l. Pozzuolo Del Friuli, Italy) (Fig. 2).

Twelve implants, belonged to group C, were 3.8 mm in diameter and 11 mm in length and showed a small thread design, a smooth neck of 0.25 mm in the most coronal area, a micro-threads collar of 3.25 mm in length and machined surface (GEASS s.r.l. Pozzuolo Del Friuli, Italy) (Fig. 3).

Implant details of both groups are shown in Table 1.

Four female Bergamasca sheep, 4–5 years old, were included in the study. Clinical examination determined that all animals were in good general health. Exclusion criteria included general contraindications (pregnancy, systemic disease) to implant surgery and active infection or severe inflammation in the area intended for implant placement.

All animals underwent deep sedation with xylazine hydrochloride 0.1 mg/kg intravenously and 0.2 mg/kg intramuscularly (Bayer–Leverkusen, Germany). After administration of deep sedation, trichotomy was performed, as well as cleaning and disinfection of surgical sites through by using soaped povidone-iodine 7.5%; loco-regional infiltrative anesthesia of lidocaine hydrochloride solution at 2% followed (Bioindustria, Novi Ligure, Italy).

The edges of iliac crests were exposed through a skin incision of 15 cm in length. The skin and facial layers were opened and closed separately. After dissection of the soft tissues, the bone was exposed and five osteotomic sites were prepared in the left side and four in the right one of the iliac crest for a total of nine osteotomic implant sites in each animal (Fig. 4).