Short-Term Case Reports Demonstrating the Use of Volume-Stable Collagen Matrix

As the role of sufficient soft-tissue dimensions in the health, function, and esthetics of periodontal and peri-implant tissues comes further into focus, an increased emphasis in the recent periodontal and implant literature has been placed on the concept of "phenotype modification"¹ or "biotype conversion."^2,3 This idea broadly refers to soft-tissue augmentation therapies used to increase either the amount of attached keratinized gingiva or the volume and thickness of the periodontal and peri-implant tissues. The two clinical case reports described in this article demonstrate the use of a novel volume-stable xenogeneic collagen matrix to increase the volume and thickness of peri-implant mucosa.

Recent systematic reviews indicate that the autogenous subepithelial connective tissue graft (SCTG) is considered to be the ideal graft material for increasing tissue volume and enhancing pink esthetics in implant and partially edentulous sites.^4,5 Drawbacks of autogenous tissue grafts, however, include increased morbidity, postoperative discomfort, additional chairtime, increased risk of complications from vascular or nerve damage, and anatomical limitations in the harvest site.^6-9 Additionally, many patients experience significant anxiety from the anticipated discomfort of a palatal tissue graft, which may also be a barrier to patients seeking appropriate care.

Increasingly available commercial biomaterials, meanwhile, offer several benefits versus autogenous tissue harvesting. Advantages of tissue substitutes include unrestricted availability, avoidance of a second surgical site, reduction of operation time, and patient preference with favorable patient-reported outcome measures.¹⁰ A biomaterial matrix for soft-tissue augmentation should be biocompatible, able to maintain space or volume, and conducive to angiogenesis and cellular migration and proliferation.

A novel resorbable volume-stable collagen matrix (VSCM) (Geistlich Fibro-Gide^®, Geistlich Pharma, geistlich-pharma.com) recently approved by the US Food and Drug Administration and introduced to the market is a porous collagen matrix of porcine origin designed to facilitate cell and vascular ingrowth and soft-tissue volume augmentation.¹¹ The material is chemically cross-linked during manufacturing, which gives it resistance to mechanical compression and early resorption. Early in vitro and in vivo studies demonstrated that the material could resist mechanical stress under dynamic loading conditions while still promoting fibroblast proliferation and volume gain.^12-16 In a randomized clinical trial, the efficacy of VSCM was compared against SCTG around single unrestored dental implants in the esthetic zone.^17,18 The gains in soft-tissue thickness after 90 days were similar in both groups and demonstrated non-inferiority of the VSCM. The augmentation results were followed-up for 1 and 3 years after the implants were definitively restored and showed minimal changes to the buccal soft-tissue dimensions in both groups during the follow-up periods.^19,20 Histological samples obtained at 3 months post-surgery showed resorbing fragments of VSCM surrounded by a loose network of newly formed collagen fibers with few inflammatory cells and no indications of a foreign body reaction.¹⁷ In a clinical case series, VSCM was used simultaneously with implant placement and guided bone regeneration (GBR) in the esthetic zone and demonstrated feasibility of the surgical approach and significant buccal soft-tissue thickness gain (median: 1.56 mm after 8 weeks).²¹

The authors (RAL and JG) have more than 3 years of routine clinical experience with VSCM. Two of their cases, which incorporate several keys of their "10 Keys" concept for successful esthetic-zone single implants,^2,3 are presented.

The patient presented to RAL's office wanting immediate replacement of his mandibular teeth. The patient had never been happy with his mandibular jaw esthetics after a mandibular anterior implant was placed and restored years prior and which now presented with significant bone loss resulting in food impaction with adjacent lower anterior teeth. All options were presented to save his mandibular teeth. The patient did not want a drawn-out treatment with bonded orthodontic appliances. He elected for removal of his lower teeth and placement of six axially placed implants for a fixed dental prosthesis restoration. He preferred immediacy with his treatment in the lower jaw as he was planning on moving out of the area within 12 months.

The patient's periodontal phenotype was thin to medium with generalized buccal attachment loss on all remaining teeth.

After local anesthesia (articaine HCL 4%) was administered via bilateral mandibular blocks and long buccal injections, full-thickness flap reflection was completed in the mandibular jaw with minimally traumatic removal of teeth Nos. 19 through 29 with preservation of all buccal plates. Six immediate implants (five Straumann^® Regular Connection Bone Level Tapered and one Straumann^® Regular Neck Tissue Level, Straumann, straumann.com) were placed with the aid of an anatomically correct surgical guide template (Figure 1).

To follow the "10 Keys" concept, the surgical goal is to have at least 2 mm of bone and soft-tissue thickness buccal to all implants (Figure 2). In this case, this was accomplished by bone grafting all immediate buccal gaps, socket grafting sites Nos. 23 through 26 for pontic site development, and contour grafting the site No. 30 buccal membrane (Bio-Oss^® and Bio-Gide^®, Geistlich Pharma).

After management of the buccal gaps, "phenotype conversion" was used to augment the peri-implant mucosa.^2,3 The patient was concerned about overall postoperative discomfort, as bilateral palatal tissue harvesting for two large SCTGs would be needed to augment the four immediate mandibular implant sites; thus, the patient instead accepted a "palate-free" option with VSCM (Fibro-Gide) (Figure 3).The use of the VSCM requires that adequate hemostasis be obtained, because, like a sponge, the material will expand significantly (up to 30%) once hydrated.²¹

Four pieces of the material (each 15 mm x 20 mm x 6 mm thick) were individually thinned while dry using a new #15 surgical blade by removing 2 mm of thickness (discarded). This made the pieces of VSCM material 4 mm thick. Under relatively dry conditions and with 1:50,000 lidocaine with epinephrine having been administered, the pieces of material were inserted under the buccal flaps from sites Nos. 19 through 29 after buccal gap bone grafting and covering with collagen membranes (Bio-Gide) for GBR in the immediate sites (Figure 4). After the VSCM was placed, single interrupted 4-0 chromic gut sutures were used to penetrate both the flaps and VSCM to stabilize the material into position over the collagen membrane (Figure 5).

The patient's same-day restorative visit was coordinated with the prosthodontist for impressions and inter-occlusal records for the fabrication of a laboratory-made metal-reinforced screw-retained provisional, which was inserted 24 hours later using the indirect technique for provisionalization.²² A second screw-retained polymethyl methacrylate (PMMA) provisional was then inserted to finalize the occlusion scheme in preparation for the full-arch milled zirconia prosthesis. Due to the recent COVID-19 pandemic, the final prosthesis was delivered 1.5 years post-surgery with an acrylic nightguard appliance. The occlusal view of the soft tissues associated with the six implants, in a photograph taken by the prosthodontist prior to the delivery, showed a thickened periodontal phenotype confirming "phenotype conversion" (Figure 6). The patient was extremely happy with the final result and the overall seamless experience between offices, which facilitated minimal downtime and discomfort (Figure 7).

The patient presented to JG's office for extraction and immediate implant placement to replace fractured tooth No. 9. The plan called for bonding the crown of the fractured tooth (No. 9) back into position as a provisional restoration (Figure 8).

After infiltration with articaine 4% with epinephrine 1:200,000 and bupivacaine 0.5% with epinephrine 1:200,000, the tooth and root were extracted, leaving an intact buccal plate. This was followed by immediate implant placement along the palatal wall and bone grafting of the 2 mm to 3 mm buccal gap with a combination of autogenous bone chips and anorganic bovine bone mineral (ABBM) in a ratio of 1:3 (Figure 9). Contour management, in accordance with the principles of the "10 Keys" concept,² was accomplished with a custom healing abutment. Soft-tissue augmentation was then accomplished with VSCM to avoid the harvesting of a palatal SCTG (Figure 10).

Before the custom healing abutment was attached, a subperiosteal pouch was created on the facial of the socket using a blunt curved tunneling instrument (Zadeh VISTA tunneling instrument #3, DoWell Dental Products, Inc., dowelldentalproducts.com) to detach the labial gingiva. This subperiosteal space was extended past the mucogingival junction to the adjacent interdental spaces, but not coronally over the papillae. Once this space was created, a sterile, non-woven gauze moistened with sterile saline was pushed into the space in a manner similar to packing retraction cord around a tooth for impression-making.

A dry 12-mm-long piece of VSCM (Fibro-Gide) was trimmed with sharp scissors to taper the apical end and reduce the thickness from 6 mm to 4 mm. The surgeon then compressed this collagen matrix between his fingers to make it 1 mm to 2 mm thick and give it the consistency of a piece of cardboard. In a quickly sequenced move, the surgical assistant removed the gauze while the surgeon slipped the compressed VSCM into the space between the retracted facial tissue and the buccal plate using sterile cotton pliers and the aforementioned tunneling instrument. The VSCM position was adjusted so that it was level with the gingival margin and allowed to rehydrate with tissue fluid and blood (Figure 11). The poly-ether-ether-ketone (PEEK) custom healing abutment was then placed with ideal subcritical contours, completing the surgical procedure (Figure 12). Finally, the original tooth No. 9 was bonded to the adjacent teeth to serve as a provisional restoration (Figure 13).

After 3 months of healing, the patient was referred back to the restorative dentist for final restoration. The patient opted to have both teeth Nos. 8 and 9 restored with prominently contoured crowns. Clinical evaluation of the final restoration 6 months after implant placement showed loss of the facial subcritical contours as evidenced by the slight coronal creep of facial gingiva and slight lack of root prominence (Figure 14). An implant crown that more accurately duplicated the original tooth could have been created had a faithful reproduction of the contours in the impression been done using the custom impression coping technique²³ or had the technician preserved the contours. Interproximally and more apically, tissue contours were perfectly preserved, and the patient was highly satisfied with the final results despite the imperfect pink esthetics.

Both of these cases demonstrate several relevant principles and support the use of the authors' "10 Keys" approach, which can be utilized in both esthetic and non-esthetic areas of the mouth, as well as in challenging situations involving thin periodontal phenotype, thin labial plates, and/or full-arch immediate-load cases. By performing immediate placement with simultaneous hard- and soft-tissue grafting, treatment time can be minimized without compromising results. The use of VSCM avoided the need for a second surgical site in the palate, minimizing the amount of postoperative follow-up and patient discomfort. Additionally, both cases demonstrated that the restorative aspects of the "10 Keys" are as important as the surgical ones, with final contour management and component selection directly influencing final outcomes.

The critical amount of bone necessary around dental implants to prevent physiologic bone loss has been thoroughly investigated.^24-26 Modern theorem on meticulously planned dental implant placement in three dimensions takes into consideration the restoratively optimal position as well as the amount of hard tissue needed to provide an anatomically stable environment. What has not been thoroughly investigated are the dimensions of soft-tissue thickness necessary around dental implants.

Esthetically, it is beneficial to maintain an adequate thickness of soft tissue to create an illusion of root prominence and to minimize the potential transmucosal discoloration of the fixture and abutment. In an in vitro study, 3 mm of tissue thickness was required to sufficiently mask optical changes in all test materials.²⁷ In a recent clinical spectrophotometry study, all implant sites with thin soft-tissue phenotype (≤2 mm) showed color changes exceeding the critical threshold of clinical detectability regardless of the abutment material used (titanium, titanium nitride, and zirconia).²⁸ In immediate implant placement and provisionalization, it has been demonstrated that the simultaneous augmentation of mucosal thickness using SCTGs to yield a final thickness of >2 mm helped to minimize discoloration caused by the prosthetic component, compared to nongrafted sites.²⁹

The need to achieve adequate tissue thickness early to prevent mucosal recession has been shown in a number of clinical studies on outcomes of immediate implants. After a mean follow-up time of 2.15 years, Kan et al found that thin and thick biotype sites that received connective tissue grafts at the time of immediate implantation all exhibited thick biotypes and minimal changes to the levels of the mucosal margin, interproximal papillae, and marginal bone.³⁰ It should not be presumed, however, that the presence of thick gingival biotype obviates the need for soft-tissue augmentation. In a 5-year prospective case series, eight out of 17 patients who had thick gingival biotypes experienced significant esthetic complications (three developed advanced mid-facial recession [>1 mm] between the 1- and 5-year postoperative period) and had to undergo corrective tissue augmentation with SCTGs.³¹ Anticipating the risk of esthetic problems regardless of phenotype, the present authors (RAL and JG) recommend the routine use of connective tissue grafts buccal to the facial bone as a critical step in the surgical protocol of immediate implant placement.^2,3

An implantable biomaterial ideally should integrate into the host tissues without a prolonged, chronic inflammatory reaction or foreign body reaction.³² Collagen was identified as an ideal structural protein for the construction of extracellular scaffolds because of its natural abundance and role in tissue neogenesis and regenerative healing.³³ In order for a scaffold to create and maintain intraoral tissue volume, it needs to have an adequate resorption time to facilitate replacement by host tissue and possess mechanical resilience to normal masticatory forces and tension from the overlying mucosal flap or sutures. In in vivo studies in animal and human subjects, the VSCM described in this article has demonstrated early vascularization and progenitor cell invasion, connective tissue formation, and macrophage-mediated resorption with a short inflammatory phase.^14,16,17,34 In daily clinical application, the authors report that their patients have generally experienced uneventful healing and minimal discomfort following the use of VSCM.

A proper diagnostic and treatment planning process for dental implant rehabilitation should include evaluation of the soft-tissue volume associated with the implant site, because it is not only a major contributing factor to the esthetic outcome but may also function to maintain marginal bone levels around the implant. As such, a decision to augment the soft tissue should be considered in every case as described in the "10 Keys" checklist.² The autogenous palatal graft has long been the method of choice for soft-tissue augmentation, but surgeons should weigh its benefits against the potential complications associated with a secondary surgical site and the preference of the patient for a relatively painless experience especially when treating large areas. The volume-stable collagen matrix is a promising material with favorable healing characteristics and thickness maintenance compared to the SCTG in up to 3 years in current literature. Further clinical trials are needed to determine long-term efficacy and stability.

The authors have financial affiliations with Geistlich Pharma North America.

Robert A. Levine, DDS
Clinical Professor, Kornberg School of Dental Medicine, Temple University, Philadelphia, Pennsylvania; Clinical Associate Professor, Adams School of Dentistry, University of North Carolina, Chapel Hill, North Carolina; Diplomate, American Board of Periodontology; Fellow, International Team for Implantology; Fellow, Academy of Osseointegration; Private Practice, Dental Implants and Periodontics, Philadelphia, Pennsylvania

Jeffrey Ganeles, DMD
Adjunct Associate Professor, Nova Southeastern University College of Dental Medicine, Fort Lauderdale, Florida; Clinical Assistant Professor, Boston University Goldman School of Graduate Dentistry, Boston, Massachusetts; Diplomate, American Board of Periodontology; Fellow, International Team for Implantology; Fellow, Academy of Osseointegration; Private Practice, Periodontics and Dental Implant Surgery, Boca Raton, Florida

Ron Wang, DMD
Resident, Graduate Prosthodontics, Montefiore Medical Center, Bronx, New York