Abstract

The presence of adequate gingiva with firm attachment to the underlying periosteum and bone is important for the overall long-term success of implant-supported oral rehabilitation. In the presence of an atrophic edentulous mandible, peri-implant soft tissue management is a challenging task. Therefore, mucosal grafts are sometimes necessary in patients with insufficient attached gingiva around abutments. Immobilization of this graft is mandatory for its survival. The study design included 5 edentulous patients with inadequate attached gingival zone, all candidates for implant surgery and free gingival graft. In the first surgery the implants were inserted, and in the second operation a free gingival graft was obtained from the palate and sutured to the mandibular site. A newly designed stent was applied for the stabilization of the graft. Two to 3 weeks after the second surgery, the stents were removed and the attached gingival width was measured. Long-term evaluations were performed to follow the survival of the graft. All grafts were intact at the time of stent removal. In all cases, the long-term evaluations revealed adequate attached gingiva around the implant. It may be concluded that immobilization of free gingival graft in the recipient site increases its success rate and its survival rate. The application of the newly designed stent can serve as a proper and easy immobilizer for peri-implant soft tissue management.

Introduction

It has been shown that tissue integration of an osseointegrated implant should involve formation of new gingival ligament to wrap the metal and connect it to the gingiva and adjacent hard tissue and also contribute to the proper bone to metal contact.1 

The peri-implant seal apparently plays a crucial role in the longevity of osseointegrated implants. Because there is no cementum or fiber insertion into the surface of an implant, the peri-mucosal seal is extremely important. A broken seal results in openings which most probably extend to osseous structures, thus subjecting the area to the peri-implantitis.2 The delicate alveolar mucosa is not expected to withstand the daily demands of tooth brushing, mastication of coarse food, and the function of adjacent muscles and frena. Therefore, the presence of attached keratinized gingiva (KG) around the abutments may be considered as a prerequisite for implant health.36 Meanwhile, mobile nonkeratinized gingiva (NKG) is not necessarily associated with periodontal problems when satisfactory oral hygiene is maintained.7,8 Most patients, however, are not able to maintain a good oral hygiene.

Due to the presence of ample collagen type V, KG is more consistent than NKG, serves as a superior seal against bacterial penetration, and provides higher seal maintenance compared with NKG.1,9 This well describes a less frequent peri-implant pocket formation in KG compared with NKG.10 

Alveolar ridge resorption following tooth loss is associated with decreased width of KG and reduced vestibular depth. This phenomenon leads to the proximity of resorbed crestal bone and peri-implant soft tissue to muscular attachment fibers. Since no attached gingiva is present, muscle contractions will pull the peri-implant tissue resulting in a broken seal, which has been associated with chronic irritation and patient discomfort through the literature.11 Various surgical procedures such as vestibuloplasty with autogenous palatal graft, allograft, and apically positioned grafts, and also graft-free surgical procedures have been suggested to augment KG around implants and sulcus deepenings.1215 

Studies on periodontal healing demonstrate the importance of tissue stability on the underlying osseous or dental support.16 In all described methods, the fixation of the graft is the most important principle to achieve promising results. To immobilize the graft against the muscular function, authors have recommended different approaches, such as the application of transitional dentures, circummandibular wiring, impacted posts, and Loma Linda stents.1215,1724 

The aim of the present study was to achieve a simple and applicable fixation method to immobilize the keratinized gingival graft using a fabricated implant supported stent.

Materials and Methods

Patients

The present study was conducted on 5 patients (3 women and 2 men) with a mean age of 47 (22–70) years. An extensive preoperative examination, including complete medical evaluation and drug history, clinical examinations, and radiographic examinations were performed before the operation. All patients were candidates for dental implant placement. Two patients were fully edentulous and 3 were partially edentulous in the posterior mandible in the buccinator muscle area. All patients presented with a major loss of attached gingiva and bone resorption due to tooth loss. Informed consents were obtained in advance.

Implantation

Implants (NobelReplace, Nobel Biocare AB, Göteborg, Sweden, and Implantium, Dentium, Seoul, Korea) were inserted in the edentulous areas. Recall appointments for reevaluation and removal of any remaining sutures were scheduled 7 to 10 days after surgery. Patients were examined periodically until the osseointegration was expected to occur. Following the integration period (2 to 3 months), the implants were exposed and proper healing abutments were inserted. Proper abutments were chosen 10 days afterwards. Ball or magnet abutments (Implant Keeper, Implantium) were installed to place overdentures for edentulous patients. For partially edentulous patients, however, proper size of 2-piece abutments with at least 1 snapped prosthetic component (Snappy Abutment, NobelReplace, and Dual Abutment, Implantium) were chosen and tightened by 35 N/cm force as indicated by the manufacturers (Figure 1). An abutment level impression was made using custom tray (MZK Dental Products, Southfield, Mich) and polyvinyl siloxane material (Putty and Light Body/Normal Set, Elite HD VPS, Zhermack, GmbH, Germany). Abutment replicas were placed in the impression. All impressions were poured with improved type IV stone (GC Fujirock EP, GC Europe NV, Leuven, Belgium).

Figures 1–3

Figure 1. Implanted site has no keratinized gingiva. Figure 2. Methyl methacrylate acrylic resin stent was formed over the cast and cured. Figure 3. The finished and polished stent. Snapped temporary cap was used in this case.

Figures 1–3

Figure 1. Implanted site has no keratinized gingiva. Figure 2. Methyl methacrylate acrylic resin stent was formed over the cast and cured. Figure 3. The finished and polished stent. Snapped temporary cap was used in this case.

Stent

Based on desirable clinical width of future keratinized attached gingiva and residual bone contour, stone was reshaped and the vestibular area formed. Stent extensions were marked by a color pencil on the cast. A 2-mm wax spacer was then added on marked areas around abutment replicas on the casts to provide a noncompressive stabilizing stent to allow sufficient blood circulation during the healing period. Snapped prosthetic components (Snapped Temporary Cap, Snappy Abutment, NobelReplace, and Impression Coping, Snap on, Dual Abutment, Implantium) and ball or magnetic attachments were used in overdenture cases. Self-cured methyl methacrylate acrylic resin was formed on the planned area and polymerization phase was completed in a pressure pot. Stents were finished and polished (Figures 2 and 3).

Recipient

After the administration of proper local anesthesia for both donor and recipient sites according to the patient health and surgery time, a crestal incision was made in the KG. If there was no attached gingiva available, the incision was made as near as possible to the lingual area. Two vertical releasing incisions delineated the partial thickness flap. The flap was then apically positioned and sutured (Figure 4).

Figures 4–9

Figure 4. The flap sutured apically to prepare a recipient site for free gingival graft. Figure 5. Harvesting free gingival graft from the palate. Figure 6. The free gingival graft sutured to the recipient site. Figure 7. The stent placed over the abutments. Adaptation achieved using a periodontal dressing. Figure 8. The grafted site 10 days post operation. Figure 9. The grafted site 12 months post operation.

Figures 4–9

Figure 4. The flap sutured apically to prepare a recipient site for free gingival graft. Figure 5. Harvesting free gingival graft from the palate. Figure 6. The free gingival graft sutured to the recipient site. Figure 7. The stent placed over the abutments. Adaptation achieved using a periodontal dressing. Figure 8. The grafted site 10 days post operation. Figure 9. The grafted site 12 months post operation.

Donor

A gingival graft was taken from the palate. The graft was 1 to 2 mm in thickness, 13 mm in width, and free of adipose tissue. The graft was then trimmed to adapt to the shape and size of the recipient site (Figure 5).

Procedure

After suturing the graft to the recipient cites, the stent was adapted to the site using a regular-set periodontal dressing (Coe-Pak, GC America Inc, Alsip, Ill). The stents were then installed on the abutments (Figures 6 and 7). The sutures were removed 7 days afterwards and the stent was relined with the same periodontal dressing and repositioned again over the grafted site. The stent was removed 2 weeks after the surgery (Figure 8). The patients were asked to come back after 3 weeks (healing period). The final impression and restoration phase were done, respectively. Follow ups at 3, 6, and 12 months were arranged to assess the survival of the grafts (Figure 9).

Results

Clinical and photographic measurements showed a proper increase in the attached gingiva width. After 1 year, the mean size of the remained gingival graft approximated 37% of the initial size (Table). The maximum changes occurred during the first 3 months after the soft tissue management procedure (41.9% shrinkage).

Table

Dimensional change (in mm) of the free gingival graft over time

Dimensional change (in mm) of the free gingival graft over time
Dimensional change (in mm) of the free gingival graft over time

For 2 patients, implant-supported mandibular overdentures were fabricated. For the rest, implant-supported fixed prostheses were made. In all patients, the development of the attached gingiva allowed a better restoration of the edentulous site. Patients reported little soreness during the healing and maintenance phases. No signs of inflammation and peri-implantitis were observed through periodical examinations.

All patients regained satisfactory function and esthetics and reported a normal social life.

Discussion

Although the presence of KG is not a necessary factor in the maintenance of peri-implant tissue health, its presence is generally advocated if oral hygiene is adequate.7,8,25,26 The oral hygiene maintenance of edentulous patients with fixed prostheses could be inconvenient or even harmful in the absence of attached masticatory mucosa.36 The peri-implant soft tissue tension due to the activity of muscular attachments in vicinity may lead to the disruption of biologic attachment around the implants and cause inflammation.11,12 Once the vestibular depth is lost, food boluses may easily be trapped around transmucosal extensions of implants and exacerbate the inflammation.27 

A necessary step in the restoration of an edentulous area is to regain KG and vestibular depth.28 Studies have demonstrated the importance of the tissues' stability for the first hours when support is provided by underlying osseous or dental structures.16,29 Movement of the graft during mastication and phonation will disturb healing procedures. Most of the clinicians prefer a protective device during the healing phase.24 Transitional dentures are not stable themselves, and hence are not suitable for stabilizing. Circummandibular wiring and impact posts are seemingly very aggressive for patients and need extra clinical practices, skills, and equipment.13,1724 Similar to the custom stents designed by Loma Linda and Brygider and Bain, the concept behind the stent presented in the present study is based on conservative tissue management and the application of existing facilities.12,14,15 

The present study is in agreement with other studies that claim the maximum tissue shrinkage (approximately 20%–40%) occurs during the first 3 months post operation30,31 and will proceed until 12 postsurgical months with a persistent, significantly lower rate.32 The tissue width at the end of the study (4.3 mm in average) was about 37% of the initial grafted tissue width. This width was seemingly sufficient for predictable implant maintenance.

It is always difficult to keep the fibrous and muscular attachments away merely by apically affixed flaps with periosteal sutures, especially in the presence of highly active mentalis or buccinator muscles. The presented stent was designed to prevent coronal migration of muscular attachments and consequently provide adequate vestibular space. Meanwhile, it meant to immobilize and protect the free gingival graft in the recipient site from mechanical stresses and interrupted circulation.26,33 The results of the study indicate that the treatment goals are achieved, meaning about 37% of the tissue width was maintained after a 1-year follow-up. The negligible soreness observed may be due to the protective effect of the stent during wound healing and proper KG formed around their implants afterward. This method followed the routine sequences of a restorative rehabilitation procedure, and the impression which was taken for the fabrication of the stent will be used for the fabrication of the restoration as well during healing. The only remaining step is the final contouring of the cervical third of the restoration, which will be adjusted 6 weeks after the soft tissue graft surgery by a pick-up impression of the fabricated restoration.

Clinicians may prefer separate appointments for a tissue graft and an implant second surgery. It could save some time of treatments; however, it might have some difficulties to controlling the amount of Coe-Pak under the splint. Coe-Pak might go in between newly grafted tissue. Primary attempts for soft tissue management are usually initiated at the second stage surgery by simple flap modifications. In fact, in so many borderline situations, it is more rational to wait and evaluate the results of the primary conservative interventions and decide for more complicated approaches thereafter. The aim of the Coe-Pak dressing application under the stent is limited to the prevention of dead space formation between the stent and the adjacent tissues with a medical filler so that a light contact will be maintained between the tissue and the stent. This space was designed at the first step of stent fabrication procedure by wax. Coe-Pak manipulation early in its setting process provides a paste of lower viscosity that may freely flow in the space between the stent and the grafted tissue.

KG surgery advantages before implant surgery are well known in class III Kennedy partially edentulous patients who could benefit from stent stabilization in a teeth-bound edentulous span. However, our partial edentulous cases were class II Kennedy patients, therefore stabilization could be achieved only by a transitional partial removable stent (denture) in which the stabilization is provided by cross-arch design. The stent fabrication may be complicated by the positioning of the teeth and the presence of undercuts, which will not be comparable to the fixed anchorage achieved by an implant abutment.

In partially edentulous patients, keratinized gingival width was limited to 2–3 mm on the lingual aspect of the healing abutments to eliminate the need of the lingual side correction. But in the completely edentulous cases, the width of the keratinized gingiva was reduced to less than 1–2 mm, and the soft tissue management involved both the lingual and the labial aspects of the crestal ridge.

This study was a pilot case series study and the authors are looking forward to further provide evidence for their findings on soft tissue augmentation around implants through case control studies. The present study was also limited by the availability of patients with bilateral edentulous spans and inadequate attached gingiva who sought an implant supported restoration. It was also not possible to use control sites in the present study. It may not be possible to make a comparison between the results obtained by this technique and those of other suggested techniques. On the other hand, the evaluation of the results was subjective and only based on the authors' clinical experiences.

In conclusion, the method we have presented can be recommended as a modality of peri-implant soft tissue management in those cases in which it might be expected that the planned implants will later be surrounded with insufficient or no healthy attached gingiva.

Abbreviations

     
  • KG

    keratinized gingiva

  •  
  • NKG

    nonkeratinized gingival

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Author notes

1

Department of Oral and Maxillofacial Surgery, School of Dental Medicine, Azad University of Tehran, Tehran, Iran.

2

Department of Prosthodontics, Tehran University of Medical Sciences, Tehran, Iran.

3

Private practice, Tehran, Iran.