Peri-implant bone augmentation using the subperiosteal peri- implant augmented layer technique and a bovine-derived bone block

A 50-year-old, non-smoking, systemically healthy female patient presented for implant-supported rehabilitation of an edentulous area in the left posterior mandible (Fig. 1). After treatment for Stage II periodontitis, the patient had a bleeding on probing score of < 10% and no sites with a probing depth of ≥ 5mm and was enrolled in a supportive periodontal care programme.

The implant position was planned digitally on a CBCT scan, and a surgical guide was fabricated. Digital planning previewed the formation of a buccal dehiscence at placement of both implants, suggesting the need for a horizontal bone augmentation procedure (Figs. 2 & 3). At the buccal aspect, a split-thickness flap (creating the mucosal layer) was raised, leaving the periosteal layer on the edentulous ridge intact. The periosteal layer was then elevated from the bone crest by means of a microsurgical periosteal elevator (PTROM, Hu-Friedy) and tunnelling knives (KPAX, TKN1X and TKN2X, Hu-Friedy) with varying angulated sharp edges (Fig. 4).

At the lingual aspect, a full-thickness flap was elevated. The elevation was extended in an apical direction to detach the superficial fibres of the mylohyoid muscle and obtain a tension-free lingual flap. The implant sites were prepared using the CAD surgical guide, and two tissue-level implants (ELEMENT, Thommen Medical) were positioned. The implants presented with a buccal dehiscence of 3mm at implant #36 and 2mm at implant #35. Cortical perforations were performed using a carbide bur (Fig. 5). A graft composed of deproteinised bovine bone mineral, delivered as a block (Geistlich; Fig. 6), was trimmed using a high-speed diamond bur in order to obtain a homogeneous thickness of 3–4mm and was adapted beneath the periosteal layer to completely cover the exposed implant surface (Fig. 7). Using a resorbable #6/0 suture, the periosteal layer was stabilised to the lingual flap by means of internal mattress sutures. The mucosal layer was coronally advanced to achieve primary closure of the wound (Figs. 8 & 9).

Six months after the implant placement, a re-entry procedure for implant exposure was performed using a buccal split-thickness flap (Fig. 10). It could be seen that the previously exposed implant surfaces were completely covered by new hard tissue, and a peri-implant buccal tissue thickness of ≥ 3mm was present at the most coronal portion of both implants (Figs. 11 & 12). A free epithelial and connective tissue graft was placed to augment the peri-implant soft-tissue phenotype (Fig. 13).

A digital impression was taken four weeks after the implant exposure to digitally plan the shape and emergency profile for the definitive restoration (Fig. 14). Two splinted crowns were milled from a zirconia monobloc and cemented on to the titanium inserts according to the manufacturer’s instructions. The defi nitive restoration was screwed on four weeks after impression taking (Fig. 15). The peri-implant tissue conditions appeared adequate on both clinical and radiographic examination (Fig. 16).

Conclusion

The present case report indicates that the combination of a subperiosteal peri-implant augmented layer and deproteinised bovine bone mineral may be successfully used to achieve an increase in buccal tissue thickness at the most coronal portion of an exposed implant.

Prof. Leonardo Trombelli, Italy