Improving Free Gingival Graft Success Around Implants Using a Completed Implant Restoration

Implant restorations have been shown to be a predictable treatment option for the replacement of missing teeth, with high survival rates reported for single-tooth and partially edentulous patients.^1-3 The patient's and clinician's ability to maintain peri-implant health with oral hygiene and regular maintenance visits is essential for long-term success.⁴ The need to have keratinized tissue around dental implants has been investigated in many studies over the past 30 years. Based on human studies, some authors have concluded that keratinized tissue around implants is not necessary for maintaining peri-implant health as long as excellent oral hygiene is maintained.^5,6 However, most experimental studies, cross-sectional studies, and systematic reviews have concluded that keratinized tissue is essential for maintaining peri-implant health.^7-10

A significant factor affecting osseointegration is the surface roughness parameter (Ra value). Machined-surface implants were used for decades, and while they harbored only a minimal amount of plaque due to their smooth surface (0.3 µm to 0.5 µm), the trend in implant dentistry shifted to moderately rough-surface implants (1 µm to 2 µm), which were able to produce faster and more predictable osseointegration.¹¹ Contemporary studies and reviews relating keratinized tissue to implants have based their conclusions on the moderately rough-surface implants that are currently being used today.^10,12

A lack of keratinized tissue often can lead to complications such as pain during oral hygiene procedures, mucosal recession, increased risk of inflammation, and mechanical irritation during function.^13,14 Angled implants often are used in implant dentistry to avoid impinging on vital structures such as nerves and the maxillary sinus. The use of such implants can make oral hygiene difficult for the patient. While augmenting keratinized tissue prior to implant placement or during stage 1 or stage 2 surgery is advantageous because of greater predictability,¹⁵ it is often necessary to augment keratinized tissue after loading when most complications related to soft tissues around the implant become evident.

Free gingival grafts (FGGs) are commonly used to augment keratinized tissue when marginal soft-tissue recession occurs in non-esthetic areas.¹⁵ This increases soft-tissue volume as well as keratinized mucosa at the implant site. In two studies investigating the keratinized mucosa gain around loaded implants, similar outcomes were achieved in which 1.5 mm of keratinized mucosa gain was obtained around loaded implants treated with FGGs and connective tissue grafts.^16,17 However, the stability of the FGGs may be compromised depending on the case, such as when there is a complete absence of attached gingiva. Immobilization of the graft can become a challenge in these circumstances.

To improve clinical success rates, stents of various designs have been fabricated to increase the stability of the graft at the recipient site (Figure 1 through Figure 4).^18,19 Solutions may include retentive caps that may have a male and female component or devices that can be adapted to the healing abutments and screwed in. The acrylic attached to the retentive device is designed to then press down on the tissue to improve stability of the graft by enhancing contact to the recipient site. A disadvantage common to both of these options is that they require prefabrication by a laboratory, resulting in increased cost and time. They also necessitate additional visits for both the clinician and patient because these devices require try-ins prior to surgery to assess the adaptation of the stent to the recipient site.

The purpose of this case report is to present a novel way of improving free gingival graft success around implants using a completed implant restoration.

The clinical data in this case report was extracted from the anonymous implant database from the routine treatment of patients at the Ashman Department of Periodontology and Implant Dentistry at the New York University College of Dentistry (NYUCD) Kriser Dental Center. The office of Quality Assurance at NYUCD certified the implant database. This case report is in compliance with the Health Insurance Portability and Accountability Act (HIPPA) requirements and approved by the University Committee on the Activities Involving Human Subjects (UCAIHS).

A 50-year-old woman with a nonremarkable medical history and no known drug allergies presented to the clinic complaining of pain and discomfort on implant No. 31, which had been placed 1 year previously (Figure 5 and Figure 6). The implant was placed slightly angled toward the inferior alveolar nerve to avoid nerve damage and emerged slightly buccal to the zone of keratinized tissue on the crest. The implant served as the distal abutment for a three-unit implant-supported porcelain-fused-to-metal (PFM) bridge from implant No. 29 to No. 31.

Following administration of local anesthesia (lidocaine 2% with epinephrine 1:100,000, Henry Schein Dental, henryschein.com), the abutment screws were loosened using a SCS screwdriver (SCS^® Screwdriver, Straumann, straumann.com), and the three-unit bridge was removed. Clinically, the surrounding soft tissue on No. 31 was non-keratinized alveolar mucosa on the buccal aspect with a zone of keratinized tissue on the lingual aspect (Figure 7). No signs of radiographic bone loss were evident on the periapical radiograph (Figure 8).

Local anesthesia (lidocaine 2% with epinephrine 1:100,000, Henry Schein Dental) was administered to the surrounding tissue on implant No. 31 and the upper left palatal area. A sulcular incision was then made to the bone level on the implant, and the peri-implant mucosa was reflected apically. An autogenous FGG was then harvested from the palate (Figure 9), which was approximately 1 mm wider than the recipient site. After the graft was cut with a manual tissue punch with an internal diameter of 6 mm, a sharp scalpel #15 blade was used to dissect the fibers, leaving the periosteum and connective tissue fibers on the palatal bone (Figure 10). This ensured that bone denudation was avoided.

Immediately after harvesting, the autogenous FGG was incised in a straight line approximately 2 mm in length in the center of the graft to allow a through and through passage for the implant abutment and screw. The graft was sutured to the recipient site on all corners with suture material (Vicryl 5-0, Ethicon, jnjmedicaldevices.com) over implant No. 31. This graft was secured with a total of four single interrupted resorbable sutures, and the implant was not submerged (Figure 11). The three-unit bridge was used to secure the graft by passing the screw through the poncho-like perforated graft. The bridge was then hand-torqued to 35 Ncm to both the No. 29 and No. 31 implants (Figure 12).

The patient was given postoperative instructions, which included not to brush for 2 weeks and to maintain oral hygiene with chlorhexidine gluconate 0.12% oral rinse three times a day. The patient was prescribed amoxicillin 500 mg three times a day antibiotic coverage for 1 week and was followed clinically for a total of 16 weeks. At the 16-week follow-up the graft had healing with a 2 mm to 3 mm band of keratinized tissue on the buccal, mesial, and distal aspects of the implant (Figure 13).

Several complications can occur when non-keratinized mucosa surrounds an implant, such as discomfort during oral hygiene procedures, mucositis, and recession. To improve the long-term prognosis of implant treatment, it is recommended that a zone of keratinized gingiva of at least 2 mm surround the implant.²⁰ In the present case, attempts were made to manipulate the soft tissue during second-stage surgery to increase the zone of keratinized tissue, however these attempts still proved insufficient to achieve an adequate band of keratinized mucosa. The standard for grafting around implants is the use of autogenous free gingival grafts, because they are able to provide a wide zone of keratinized tissue as well as denser connective tissue, which is well suited for dental implants. FGGs can be categorized according to thickness: thin = 0.5 mm to 0.8 mm; average = 0.9 mm to 1.4 mm; thick = 1.5 mm to >2 mm. A thick graft has less shrinkage and is more resistant to recession.²¹

The size of the graft to be obtained is dependent on the amount of peri-implant keratinized tissue necessary and available. The authors recommend harvesting donor tissue with this parameter in mind while simultaneously allowing for expected contraction of the tissue. In the present case a circular punch was fabricated in the periodontology/implant dentistry department by modifying a trephine drill to have sharp beveled edges to allow for even and efficient cutting. The trephine had an internal diameter of 6 mm to control the size and thickness of the graft to be harvested. Because an implant is round in shape, the size and shape of the punched tissue will correspond to the implant, and the tissue can be stretched to overlap all sides of the implant with an equal distribution of tissue. The graft obtained with the punch has a preformed size designed to be no larger than necessary, helping to create less trauma and discomfort for the patient. This theoretically should improve healing time. The recipient site is then de-epithelized circumferentially to maximize contact of the graft to the recipient site.

The use of a fixed screw-retained prosthesis helps to overcome difficulties in stabilizing the graft in cases, such as this one, where a shallow vestibule is present or when the recipient site is completely lacking attached gingiva. Where a shallow vestibule is present, muscle pull becomes a principal cause for failure. Moreover, when there is a complete lack of attached gingiva, sutures alone may be insufficient to stabilize the mucosa. A fixed screw-retained prosthesis is able to improve the stability of the graft because, in addition to the sutures, the prosthesis ensures intimate adaptation of the graft to the recipient site. The prosthesis may also further deflect potential irritants and prevent movement from oral function from disturbing the healing of the grafted site. However, to prevent the prosthesis from placing pressure on the graft that may restrict blood supply, adjusting the length of the created perforation is recommended. In the present case, the soft tissue healed uneventfully and an adequate zone of keratinized tissue was achieved.

Immobility is essential in all types of soft-tissue grafting procedures. While suturing is necessary for creating stability for soft-tissue grafts, a prosthesis may be used as an adjunctive aid to secure the graft and improve clinical outcomes. An important prerequisite to perform this technique is to have a properly fitting retrievable appliance such as a fixed implant restoration. While this case report demonstrated a favorable outcome, more cases are needed to verify the results achieved in this and similar cases.

Anna Corinna Lim, DMD
Former Resident, Advanced Program for International Dentists in Implant Dentistry, Ashman Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, New York

Eduardo Gonzalez de la Torre, DDS
Post Graduate Student, Advanced Program for International Dentists in Implant Dentistry, Ashman Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, New York

Sang-Choon Cho, DDS
Director, Advanced Program for International Dentists in Implant Dentistry, Ashman Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, New York; Chairman, Implant Dentistry Research & EducationFoundation Scientific Advisory Board of the International Congress of Oral Implantologists

Stuart J. Froum, DDS
Adjunct Clinical Professor and Director of Clinical Research, Ashman Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, New York; Private Practice, New York, New York