Introduction
Dental implant placement and implant-supported restorations have become a vital element of modern restorative dentistry. Intense research and continual improvement of materials and clinical protocol lead to a remarkable 10-year survival rate of about 98.8% in titanium implants today.1 However, the clinical success of implant-supported restorations not only depends on the implant survival rate, but also on the absence of technical prosthetic and biological complications during the implant loading time. In this aspect of treatment, considerably lower success rates can be observed.2 Since the true clinical relevance of keratinized gingiva around dental implants is still under controversial discussion, the subject of stable peri-implant soft tissue should be a main focus of clinical research.
There have been several studies on the cause of biological complications. An important point to consider is the quantity and quality of the peri-implant soft tissue and its effect on peri-implant tissue health over time.
In 1975, Lang and Loe determined that an adequate dimension for keratinized gingiva of at least 2 mm resulted in better periodontal health in teeth compared to teeth with <2 mm keratinized gingiva.3
The oral surface of the gingiva, extending from the mucogingival junction to the gingival margin, is defined as “keratinized gingiva.” The position of the mucogingival line determines the width of the keratinized gingiva individually and can vary from 1 up to 9 mm.4
Soft tissue around dental implants and natural teeth show substantial differences concerning different aspects. Periodontal ligament fibers adjacent to teeth run perpendicularly to the root surface and insert into the cementum; in contrast, the connective tissue fibers at the implant surface are aligned in parallel and do not insert into the implant.5 Due to the high concentration of fibers and the reduced number of vessels, the peri-implant soft tissue resembles scar tissue.6 This could be the reason why there is a tendency to see more plaque associated inflammatory lesions in implants compared to natural teeth. However, the gingiva surrounding teeth and the peri-implant mucosa tend to show the same immunological response to plaque accumulation.7
The presence or absence of keratinized mucosa affecting peri-implant soft-tissue health and the long-term success of implants is still the subject of a lively debate.8
In their systematic review, Wennström and Derks found no evidence confirming a measurable benefit of keratinized mucosa around implants, especially in patients with proper plaque control.8 However, other researchers showed higher plaque accumulation and a greater incidence of tissue inflammations in patients lacking adequate amounts of keratinized mucosa.9,10
Nevertheless, it is generally accepted that an adequate zone of keratinized mucosa is beneficial in terms of enhanced aesthetics, appropriate plaque control, and feasible aftercare.11
In most clinical situations, the healing process after tooth extraction results in the loss of alveolar bone followed by bone resorption and bone remodeling.12 This also means that the mucogingival junction becomes displaced into a more coronal position.13 In the case of advanced atrophy, extensive vertical bone augmentation is often unavoidable to enable appropriate implant treatment. The flap design for primary wound closure after bone augmentation affects an additional coronal shift of the mucogingival junction and hence results in further reduction of the width of keratinized gingiva.14
To achieve a sufficient amount of keratinized tissue, several surgical techniques for soft tissue augmentation have been described. They can be classified into the performance of an apically positioned flap for secondary epithelialization, appliance of a free gingival graft (FGG), and use of a collagen matrix.15 Benefits of secondary epithelialization include avoiding another donor site with connected postoperative morbidities, but it leads to wound contraction with an increased risk of relapse.16
The free gingival graft achieves a predictable, increased stability for the newly created keratinized tissue in the long term.17 The downsides include compromised esthetics due to tissue differences in texture and color from adjacent areas.18 In recent studies, use of collagen matrices showed similar results to the FGG, but it did not provide sufficient evidence regarding long-term stability of the reestablished tissue.16
The protocol presented in this case report intends to offer a reliable strategy to relocate the mucogingival junction and to reestablish a sufficient amount of peri-implant soft tissue by second-stage surgical intervention at the time of the uncovering of the implants.
Case description and results
Requirements of the Helsinki Declaration were observed, and the patient gave informed consent concerning all surgical procedures.
Initial therapy
In a healthy 57-year-old female a dental implant in region 24 (Federation Dentaire Internationale tooth numbering system) and severely decayed teeth 38, 37, and 36 could not be preserved (Figure 1). After extraction of teeth and implant, a systematic periodontal therapy was performed in combination with full-mouth disinfection with chlorhexidine and antibiotics (500 mg amoxicillin 3 times a day and 400 mg metronidacol 3 times a day, for 10 days each).
Figure 1. X-ray of initial situation before removal of implant in region 24.
Figure 2. Augmentation and implant placement in region 24 and 26.
Figure 1. X-ray of initial situation before removal of implant in region 24.
Figure 2. Augmentation and implant placement in region 24 and 26.
After a 4-month hygiene period, a lateral bone augmentation and a sinus floor elevation with a combination of autogenous bone from the left tuberosity and artificial bone (BioOss, 1.0 to 2.0 mm, Geistlich Biomaterials, Wolhusen, Switzerland) was performed, followed by implant placement (Camlog SLPP, Camlog, Wimsheim, Germany) in positions 24, 26, and 36 after another 5 months of bone healing (Figure 2).
Second-stage surgery
Results of the hard tissue augmentation in region 24–27 was a coronal shift of the mucogingival junction to the midline of the crest. There was a strong traction from the frenulum because of the coronal displacement of the soft tissue necessary for primary wound closure (Figure 3). At the day of the uncovering of the implants, a palatally shifted incision to the periosteum was performed, ranging from region 28 into the sulcus of tooth 23. This incision was placed 4 mm palatal of the mucogingival line, to achieve 4 mm of keratinized tissue on the buccal aspect of the implants (Figure 4). A buccal split-thickness flap was raised sharply with a blade (15c, Swann-Morton, Sheffield, UK) and a plasty of the vestibule was conducted (Figure 5). The implant was uncovered with a 15c blade, performing a u-shaped modified roll flap (Figure 6). Both flaps were carefully lifted with a small elevator (Papilla elevator, Stoma, Emmingen-Liptingen, Germany) and folded to buccal (Figure 7). Cover screws were removed, the implants were rinsed with 0.1% chlorhexidine solution, and healing abutments (Dedicam 4mm, Camlog) were installed (Figure 8). The buccal flap was then secured with a combination of a horizontal mattress sutures and single sutures (Mopylen 6-0, Resorba, Nuremberg, Germany). The mattress sutures were pierced under the buccal periosteum to stabilize the flap buccally, and the knots were placed palatally. Interrupted sutures were placed for wound adaptation (Figure 9). The defect in between the implants and distal of the implant in region 26 was measured with a periodontal probe (PCPNC North Carolina, Stoma). Its shape was transferred to the tuberosity, outlined with a 15c blade, followed by a perpendicular incision to the tissue with a thickness/depth of nearly 4 mm. A parallel incision to the periosteum was performed to harvest the graft. It was then transplanted into the defect and secured with interrupted sutures (Mopylen 6-0, Resorba). On the four corners, a single suture was placed to the buccal and to the palatal to stretch the graft firmly into the defect. To fix the graft, 2 sutures were performed from the buccal tissue to the palatal tissue penetrating the graft at the same vertical level (Figure 10). The soft tissue defect at the tuberosity was filled with platelet-rich fibrin (A-PRF, Mectron, Cologne, Germany) and covered by the temporary removable dental prosthesis (RDP), serving as a surgical stent.
Figure 3. Clinical situation after removal of implant in region 24, hard tissue augmentation, and implant placement in region 24 and 26 with coronal displacement of the mucogingival junction.
Figure 4. Palatal shifted incision with a distance of 4 mm to the mucogingival line.
Figure 5. Split-thickness flap for plasty of the vestibule.
Figure 6. U-shaped incision for uncovering of the implants.
Figure 3. Clinical situation after removal of implant in region 24, hard tissue augmentation, and implant placement in region 24 and 26 with coronal displacement of the mucogingival junction.
Figure 4. Palatal shifted incision with a distance of 4 mm to the mucogingival line.
Figure 5. Split-thickness flap for plasty of the vestibule.
Figure 6. U-shaped incision for uncovering of the implants.
Figure 7. Modified roll flap to thicken the buccal tissue.
Figure 8. Installing of the wide-body healing abutments.
Figure 9. Stabilization of the flap to the buccal periosteum with horizontal mattress sutures with existing soft tissue defect between the implants.
Figure 10. Fixation of the soft-tissue grafts between the implants and distal of implant in region 26.
Figure 7. Modified roll flap to thicken the buccal tissue.
Figure 8. Installing of the wide-body healing abutments.
Figure 9. Stabilization of the flap to the buccal periosteum with horizontal mattress sutures with existing soft tissue defect between the implants.
Figure 10. Fixation of the soft-tissue grafts between the implants and distal of implant in region 26.
Wound healing
Wound healing was uneventful. There was no sign of necrosis or graft resorption. Single sutures were removed on day 8 after surgery, mattress sutures on day 14 (Figure 11). After 4 weeks the wound was completely healed and donor side re-epithelialized without any signs of inflammation (Figure 12). Six weeks after second stage-surgery, an all-ceramic fixed dental prosthesis (FDP) was cemented on all-ceramic abutments luted on titanium bases (Figures 13, 14). Stable conditions were visible 1 year after restorative treatment without any resorption of graft or buccal flap (Figure 15).
Figure 11. Uneventful wound healing and perfect integration of the grafts. Figure 12. Situation before prosthodontic reconstruction with stable soft tissue conditions.
Figure 11. Uneventful wound healing and perfect integration of the grafts. Figure 12. Situation before prosthodontic reconstruction with stable soft tissue conditions.
Figure 13. Delivery of the all-ceramic FDP luted on all-ceramic abutments luted on titanium bases. Figure 14. X-ray after delivery of the FDP.
Figure 13. Delivery of the all-ceramic FDP luted on all-ceramic abutments luted on titanium bases. Figure 14. X-ray after delivery of the FDP.
Figure 16 shows the step-by-step protocol of the clinical procedure.
Step-by-step schematic of the clinical protocol. (a) MJ indicates mucogingival junction. (b) I, incision line. (c) MF, mucosal flap. (d) IR, Incision for roll flap. (e) CS, cover screw; RF, roll flap. (f) HA, healing abutment; RF, roll flap. (g) SS, single suture; MS, mattress suture. (h) TFGG, thick free gingival graft. (i) Grafts in situ.
Step-by-step schematic of the clinical protocol. (a) MJ indicates mucogingival junction. (b) I, incision line. (c) MF, mucosal flap. (d) IR, Incision for roll flap. (e) CS, cover screw; RF, roll flap. (f) HA, healing abutment; RF, roll flap. (g) SS, single suture; MS, mattress suture. (h) TFGG, thick free gingival graft. (i) Grafts in situ.
Discussion
The topic of an adequate peri-implant width of keratinized mucosa is still considered controversial. Recent studies show, nonetheless, that an appropriate width of peri-implant keratinized mucosa and sufficient soft-tissue thickness have a beneficial influence on the long-term stability and health of peri-implant tissues.19 A small band of less than 2 mm of keratinized mucosa on implant sites increases susceptibility for plaque accumulation, peri-implant soft tissue inflammation, and peri-implant disease.20,21 It has also been shown that peri-implant mucosal tissue with soft-tissue thickness of less than 2 mm is associated with a higher marginal bone loss.19,22 Since absence of keratinized mucosa around implants before second-stage surgery is a common finding, advanced soft tissue augmentation techniques are needed. This is to increase the thickness and width of peri-implant keratinized tissue. The large supply of keratinized tissue in the maxilla enables for straightforward displacement of keratinized mucosa from the palatal to the buccal aspect. In the presented approach, this is done performing the incision on the palatal side of the implants. The procedure results in a deficit of soft tissue between the implants. Yet, papillae and pontic areas between implants are necessary to provide optimal function and sophisticated esthetic results.23 A 3–4 mm thick free mucosal graft, harvested from the hard palate or tuberosity, is used to completely fill and stabilize the interimplant soft tissue defect. To fill the wedge-shaped distal defect of the posterior implant in a free-end situation, another graft has to be harvested and transplanted. However, due to the thickness of the tissue of the tuberosity this additional graft is not coercively necessary. In clinical cases where the distal graft was set aside, a good secondary tissue healing with no noticeable volume deficit was observed. In an interdental space with a posterior tooth, a secondary graft between the posterior implant and the tooth is needed to stabilize the papilla.
The palatal graft may slightly differ in color and texture from the recipient area, especially in the esthetic zone.24 Successful integration of the free grafts depends on sufficient adaption to the existing mucosa for proper blood circulation and a minimum gap of 5 mm between adjacent implants to avoid graft necrosis.25
In summary, this second-stage surgery technique with the combination of a split-thickness flap and plasty of the vestibule, modified roll flap, and tissue grafting provides a good reconstruction method to reestablish the mucogingival line more apically after hard-tissue augmentation. Furthermore, the buccal and occlusal peri-implant soft tissue is thickened, enhancing and stabilizing the interproximal tissues between implants. This is a key factor for a long-term success in implant therapy and can serve as a prophylaxis to prevent peri-implant inflammation and peri-implant disease.
Abbreviations
- CS:
cover screw
- FDP:
fixed dental prosthesis
- FGG:
free gingival graft
- HA:
healing abutment
- I:
incision line
- IR:
incision for roll flap
- MF:
mucosal flap
- MJ:
mucogingival junction
- MS:
mattress suture
- PRF:
platelet-rich fibrin
- RDP:
removable dental prosthesis
- RF:
roll flap
- SLPP:
screw line promote plus
- SS:
single suture
- TFGG:
thick free gingival graft
- t.i.d.:
three times a day
All authors declare that they have no conflict of interest for this publication.