None of the 10 patients showed postoperative inflammation or infection after the MSFE procedure nor during surgical re-entry for dental implant placement. When opening the area for dental implant insertion, the grafted area proved to be well vascularized and the tissue at the site of the former trap-door location was slightly flexible and had a fibrous aspect. Between the periosteum and the bone graft area, adhesions were seen. Macroscopically, no voids or presence of purulent discharge were observed. Although a demarcation was observed between the grafted area and the original bone of the alveolar process, there was continuity between the grafted area and the native bone. There was no jiggling of the drill, even though bone substitute particles could still be recognized in the tissue specimen retrieved. All particles appeared well integrated in newly formed tissue. These findings were consistent in all 10 patients. In total, 22 Straumann^® SLA solid screw (standard plus regular neck, soft tissue level) dental implants with a diameter of 4.1 mm and a length of 10 or 12 mm were placed. Primary stability was achieved with all dental implants. All dental implants osseointegrated well and could be loaded with fixed prostheses 3 months after implant surgery. No dental implants were lost during 5-year follow-up.

The increase in height of the grafted area achieved by the MSFE procedure was on an average of 7.5 mm (SD ±2.8) in the 9-month group (Table 1) and 9.3 mm (SD ±3.1) in the 12-month group (Table 2). The measured tissue height appeared to be stable between 1 and 5 years in the 9-month group (Fig. 2) and the 12-month group (Fig. 3).

The histological evaluation was performed on the complete section, comprising native bone, newly formed bone, and residual graft material. The BCP particles were surrounded by connective tissue, osteoid islands, and newly formed bone. From the residual bone in all specimens, new bone formation was detected following the scaffold of the bone substitute, starting in cranial direction. This newly formed bone consisted of woven bone as well as lamellar bone and appeared as vital bone tissue containing osteoblasts, osteoid covering the border, and osteocytes inside bone lacunae. Cranially, near the lifted trap-door, some osteoid islands with osteogenic activity were detected.