Peri-Implant Guided Bone Regeneration by Dr. Giacomo Tarquini

Hard- and soft-tissue management with innovative products

by Dr. Giacomo Tarquini

Introduction
Implant-supported prosthetic rehabilitation in the presence of significant horizontal bone defects requires particular care and skill from the oral surgeon. Even if it is possible to place implants, the presence of the defect, typically on the buccal, may jeopardize the rehabilitation’s functional and aesthetic success in both the short and long term. In such cases, it is often necessary to perform a peri-implant bone regeneration procedure at the same time.

Guided bone regeneration (GBR) is one of the best-documented procedures to achieve that result: It entails the placement of a barrier membrane between epithelial and connective tissues on one side and implants and bone on the other side to create a protected space for the blood clot to form and organize, thus allowing bone cells coming from marrow spaces to repopulate the defect and to mature into new bone.

Ideally, barrier membranes used in GBR should have features that allow them to suitably protect the bone tissue long enough for the bone regeneration to be completed. They are chosen based on the anatomical characteristics of the defect, including its size, the number of bony walls and the available surface of viable bone.

Nonresorbable barriers, mostly made of expanded polytetrafluoroethylene (e-PTFE), are highly successful for GBR procedures but have some drawbacks, including the need for a second surgical procedure for their removal and their tendency to become exposed into the oral cavity. Resorbable membranes, meanwhile, are regarded as a safer option for almost any regeneration procedure nowadays because of their higher biocompatibility.

In certain cases, the recourse to resorbable barrier membranes with a longer protection period may represent an ideal compromise that significantly increases the predictability of the regeneration therapy, especially in noncontaining bone defects.

Flex cortical sheet (FCS) is a barrier membrane made from enzyme-treated, equine-derived cortical bone and it is therefore remodeled by the osteoclasts. This is why its estimated protection time is approximately 10–12 months, much longer than common collagen membranes. It also stabilizes the graft and prevents any micromovements that may hinder the bone regeneration process.


Case description
The following case illustrates implant placement associated with GBR to replace a missing mandibular first molar. The surgical protocol entails using an heterologous bone substitute obtained via an exclusive enzymatic process of deantigenation in conjunction with a FCS.

At reentry surgery, to boost the local peri-implant phenotype, a tridimensional collagen matrix is grafted onto the regenerated bone to thicken the peri-implant keratinized tissue while avoiding the need to harvest an autogenous connective tissue graft (CTG).


Surgical procedure
The patient presented with an edentulous space (Fig. 1) caused by a missing mandibular first molar, which had been extracted six months previously. Horizontal bone atrophy (Seibert’s Class 1) was detected during X-ray examination (Fig. 2).

Fig. 1

Fig. 2

Once a full-thickness flap had been raised, a very horizontally atrophied bone ridge with a marked vestibular cavity was found (Fig. 3). Considering the anatomy of the bone defect, the rehabilitation schedule entailed the insertion of an osseointegrated implant associated with the regeneration of the defect through a GBR protocol. The patient granted his informed consent to the procedure.

Fig. 3

A full-thickness flap was raised to access the surgical site, and lingual and buccal flaps were released to advance tissue coronally without any tension.

The implant site was prepared with the aid of drill stops (Fig. 4) and the implant was then inserted (Fig. 5) flush to the lingual bone crest (Fig. 6). [Editor’s note: For complete information about products used, see “Surgical Notes” sidebar on below.] A large portion of implant surface was left exposed (Fig. 7). Intramarrow penetrations were performed using a piezoelectric tip to promote the flow of blood, cells and growth factors inside the graft to foster the subsequent regeneration events (Fig. 8).

Fig. 4

Fig. 5

Fig. 6

Fig. 7

Fig. 8

After hydration with sterile saline (Fig. 9), flex cortical sheet was stabilized on the lingual aspect with a titanium pin and bone substitute was grafted around the implant surface (Fig. 10). FCS also was folded onto the graft and fixed with three other titanium pins on the buccal aspect (Fig. 11). The flaps were then sutured with horizontal internal mattress sutures and interrupted stitches (Fig. 12).

Fig. 9

Fig. 10

Fig. 11

Fig. 12

Six months later, at the time of reentry surgery (Fig. 13), a periapical X-ray was taken to assess the success of bone regeneration (Fig. 14). The surgical site was accessed through a partial-thickness flap; a significant amount of new regenerated bone could be observed, without the presence of residual granules (Fig. 15). After the lingual pin was removed, a stock healing abutment was placed (Fig. 16) and a periapical X-ray was taken to check the abutment’s proper seating (Fig. 17).

Fig. 13

Fig. 14

Fig. 15

Fig. 16

Fig. 17

To boost the local peri-implant phenotype, a collagen matrix (Fig. 18) was grafted on the buccal aspect (Fig. 19). Collagen matrix is a tridimensional, scaffold-shaped, 15-by-30-by-4-mm matrix suitable for soft-tissue regeneration procedures. In fact, after grafting, it acts as a biocompatible matrix, able to be repopulated by the patient’s connective tissue cells. Its appearance is a spongy patch with consistent density on both sides; dry use is recommended, without saline hydration. In contact with blood, it shows adhesive properties that promote placement and stabilization. This made it possible to avoid taking subcutaneous connective tissue from the patient’s palate, thus limiting postoperative discomfort.

Fig. 18

Fig. 19

An apically positioned flap was then performed with the aim of re-creating a band of attached gingiva of the ideal size and thickness, sutured with interrupted stitches and a crossed horizontal mattress suture (Fig. 20). No complications were observed during or following either surgical procedure (Fig. 21).

Fig. 20

Fig. 21

After an adequate healing and conditioning of soft tissues (Fig. 22), the subsequent porcelain-fused-to-metal definitive prosthetic crown was delivered (Fig. 23).

Fig. 22

Fig. 23

At the 24-month follow-up, a periapical X-ray was taken to evaluate the stability of peri-implant bone level (Fig. 24).

Fig. 24

Results

• The clinical pictures and periapical X-ray taken at the 24-month follow-up show excellent stability of peri-implant bone level, along with healthy peri-implant soft tissue.

• Peri-implant probing at the follow-up indicated the implant can be considered healthy.

• The patient was admitted into a supportive periodontal therapy program, which he’s still participating in.

Conclusions
The recourse to resorbable FCS with a longer protection period may represent the ideal compromise between nonresorbable e-PTFE and collagen membranes, especially in noncontaining bone defects. Such findings were confirmed by a direct clinical evaluation at reentry surgery, which revealed that the bone defect had been repaired and the aspect was that of the newly formed mature bone of the patient without the presence of bone granules. Moreover, the use of collagen matrix as an alternative to autologous CTG reduced the patient’s discomfort and surgical time length, with a better cost-effectiveness ratio.

These results call for confirmation using well-designed controlled prospective studies involving a larger patient population.

Dr. Giacomo Tarquini graduated with honors in dentistry and dental prosthetics from the Sapienza University of Rome in 1994, and has been practicing dentistry for about 25 years. Today he practices in Rome with particular interest in the disciplines of periodontology and implantology. He is also a consultant, professor, tutor and lecturer for a variety of dental specialties. Along with various articles, Tarquini is the author of the textbook "Techniques of Periodontal Surgery: From Diagnosis to Therapy."