Efficacy of free gingival graft in the augmentation of keratinized tissue around implants: A prospective clinical study.

BACKGROUND: Effectuating adequate width of keratinized tissue (WKT) can lead to a healthy and stable implant/soft tissue interface which is important for the long term success of the implant. The use of free gingival grafts (FGG) for widening the WKT around dental implants increases the amount of attached gingival tissue and prevents clinical attachment loss. AIM: The aim of the study was to assess the ability of FGG to create a healthy implant/soft tissue interface. METHODS AND MATERIAL: A total of 10 edentulous sites in 10 patients with inadequate keratinized tissue indicated for replacement of missing teeth were treated. An implant was placed in edentulous sites and the keratinized tissue was augmented using FGG at the second stage of implant surgery. WKT was recorded at baseline, 3rd month and 6th month post-operatively. Plaque index (PI), gingival index (GI), probing depth (PD) and papillary index (PPI) and were recorded at 3 and 6 months post-operatively to evaluate the health of peri-implant tissues. Paired t-test was used for standard deviation and the level of significance was taken as 5% (P < 0.05).
RESULTS: The WKT at 3 (3.2±1.61mm) and 6 months (3±1.56 mm) compared to the baseline was statistically significant (P = 0.034). The other parameters PI, GI, PD, PPI showed no clinical significance from 3 and 6 months (P > 0.05).
CONCLUSIONS: Augmentation of FGG created a significant gain in the WKT which resulted in a healthy implant/soft tissue interface. Copyright:

INTRODUCTION

The requirement for keratinized tissue around dental implants is contended.[1] Studies have shown that even without the presence of the attached keratinized tissue, periodontal health can be maintained.[2] However, some studies have shown that the absence of keratinized tissue leads to implant failure and the mobile mucosa can disrupt the implant which can cause accumulation of plaque, further enhancing the risk of inflammation.[345] The study states that widening the width of the keratinized tissue might be advantageous to the peri-implant tissue health, including minimal plaque accumulation and mucosal inflammation.[6]

There is inconsistency in the literature regarding the relationship between the width of the keratinized tissue and the health status of peri-implant tissue. However, it is accepted that the long-term stability and healthy soft-tissue implant can be achieved if a sufficient area of keratinized tissue is present.[78] There are many surgical techniques for increasing the width of keratinized tissue including Free gingival graft(FGG), apically positioned flap, coronally positioned palatal sliding flap, and acellular dermal matrix graft.[9] Among all, FGG is highly recommended, predictable, and is a versatile procedure used to increase the width of attached gingiva.[10] Hence, the aim of the study was to evaluate the use of free gingival graft in increasing the width of keratinized tissue around dental implants and its ability to create a healthy implant/soft-tissue interface.

MATERIALS AND METHODS

Patients who presented with an edentulous area having inadequate keratinized tissue were selected at the outpatient unit of the department of periodontics. The study included a total of 10 individuals between the age of 18 and 40 years. The study was conducted for a duration of 2 years. The research was approved by the Institutional Research and Ethical Committee obtained of K.L.E. Society's Institute of Dental Sciences on October 30, 2009 (IEC no.: 430), and written informed consent was obtained before the commencement of the study. Patients with at least one edentulous area in mandibular posterior region requiring replacement of tooth/teeth, unremarkable medical history, and those with keratinized tissue <3 mm at the edentulous site were included in the study. Patients with uncontrolled diabetes, coagulation disorders, allergies to materials used in the study, acute infection/pathology at the surgical site, smokers, and pregnant women were excluded from the study. A two-stage implant procedure was performed for every patient at all the sites. Augmentation of the keratinized tissue was done at the second stage of implant surgery. The width of keratinized tissue was measured according to the method described by Hall Wb in 1982, with the help of a Williams periodontal probe at baseline, 3 months, and 6 months after gingival augmentation procedures by a single operator.[11] Health of peri-implant tissues was also evaluated at 3 and 6 months after the second stage of gingival augmentation procedure using plaque index (Silness and Loe, 1964), gingival index (Loe and Silness, 1963), papillary index (Jemt, 1997), and marginal recession (Miller, 1985) levels.[12131415]

Following the initial examination and treatment planning, all patients received initial therapy including full mouth scaling, root planing, and oral hygiene instructions. Alginate impressions were taken for all the patients for both the arches, and study models were prepared. A surgical stent was fabricated on the casts to guide the implant placement in the correct position and angulation.[16] Preoperative intraoral peri-apical radiographs and digital orthopantomograph were taken for each case [Figure 1]. Ridge mapping was done with a ridge mapping instrument to evaluate the bone width.[17] All patients underwent blood investigations such as bleeding time, clotting time, and hemoglobin levels. The extraoral surface of the patient was scrubbed with 7.5% povidone-iodine solution. The operative site was anesthetized with 2% xylocaine hydrochloride with adrenaline (1:80,000). After achieving adequate anesthesia, a crestal incision was given at the edentulous site using a Bard-Parker blade No. 15. The incision was extended to the teeth adjacent to the edentulous area by giving a crevicular incision to achieve adequate flap reflection. A full-thickness mucoperiosteal flap was reflected to expose the underlying bone using a periosteal elevator.

Figure 1

Preoperative orthopantomograph

The stent, prepared on the patient's cast, was placed in the patient's mouth after disinfecting it with 5% povidone-iodine. A 2-mm pilot drill was used to drill the bone at 800 rpm through the access hole prepared in the stent. The depth of the osteotomy site was achieved using the pilot drill, depending on the length of the dental implant to be placed. Subsequently, the osteotomy site was widened using sequential widening drills according to the diameter of the implant being placed. Two-piece implants with an internal hex connection (HI-TEC™ implants) were inserted into the osteotomy site using a torque wrench, and subsequently, a cover screw was placed on the dental implant. The flap was sutured over the dental implant using black braided silk sutures, thus completely submerging the dental implant.[10] A postoperative intraoral periapical radiograph was taken after the placement of the dental implant [Figure 2].

Figure 2

Postoperative intraoral peri-apical radiograph

The extraoral surface of the patient was scrubbed with 7.5% povidone-iodine solution. The operative site was anesthetized with 2% xylocaine hydrochloride with adrenaline (1:80,000) and injected with greater palatine nerve block on the palate before harvesting a free gingival graft.

A tin foil template was designed according to the area to be augmented at the recipient site, and free gingival graft was harvested from the palate using template as a guide. The graft was harvested from the mesial surface of the maxillary first premolar to distal surface of the maxillary first molar [Figure 3], to avoid obtaining a graft with excessive fatty or glandular tissue.

Figure 3

Palatal donor site after harvesting the free gingival autograft

After obtaining the graft, it was placed on a moist gauze to prevent desiccation [Figure 4]. Excessive fatty or glandular tissue was trimmed. A split-thickness incision was performed at recipient site to receive the donor graft; the graft was sutured at the recipient site to the underlying periosteum using resorbable sutures [Figure 5]. The patients were instructed to wear a custom-made acrylic stent on the maxillary arch at donor site for hemostasis and comfort, especially during eating. A periodontal dressing was placed over the treated site.[1819] Postoperative instructions were given along with a prescription for analgesics and antibiotics (amoxycillin 500 mg twice a day for 5 days and ibuprofen 600 mg twice a day for 3 days).

Figure 4

Free gingival autograft harvested

Figure 5

Suturing the graft with resorbable sutures

After 10 days following the surgery, the periodontal pack was removed, and the area was irrigated thoroughly with normal saline. The patients were instructed to rinse with chlorhexidine mouthwash daily for another 1 week. Oral hygiene instructions were reinforced. Patients were asked to discontinue using the stent for the palatal wound. Patients were evaluated at 3 and 6 months [Figure 6a and b] postoperatively to assess the increase in width of keratinized tissue and to evaluate the health of peri-implant tissues.[9] At each visit, the oral hygiene instructions were reinforced [Figure 7]. The implants were loaded after 4–6 months with delayed loading protocol followed by placement of cement-retained prosthesis (porcelain fused to metal [PFM] crown).

Figure 6

(a) Three months postoperatively; (b) 6 months postoperatively

Figure 7

Evaluating the health of peri-implant soft tissues

The width of keratinized tissue was evaluated at baseline, 3 months, and 6 months postoperatively. The mean and standard deviation were calculated and compared using the paired t-test. The level of significance was taken as 5% (P < 0.05). The plaque index, gingival index, and papillary index were evaluated at 3 and 6 months postoperatively. Their mean values and standard deviations were calculated at 3- and 6-month intervals and were compared using paired t-test.

RESULTS

There were total 10 sites replaced with dental implants evaluated on 10 patients (6 males and 4 females). The mean age of the patients was 32.89 ± 11.23 years. Following the placement of the implant, plaque index, gingival index, probing depth, and papillary index were evaluated at 3 and 6 months. These parameters were analyzed using the paired t-test and were found to be insignificant [Table 1].

Table 1

Clinical parameters

	3 months	6 months	P
Plaque index	0.52±0.32	0.30±0.45	0.081
Gingival index	0.35±0.34	0.25±0.29	0.223
Probing depth (mm)	2.1±0.88	2±0.82	0.343
Papillary index	2.7±0.48	2.8±0.42	0.343

*P<0.05 is considered significant. mm - Millimeter; P - Probability value

No mucosal recession was noted at any of the 10 sites at 3 and 6 months postoperatively. The mean width of keratinized tissue at baseline was 2 ± 0.81 mm, which increased to 5.2 ± 1.75 mm at 3 months [Table 2]. The mean width of keratinized tissue at 6 months was 5 ± 1.56 mm. The mean gain in width of keratinized tissue was 3.2 ± 1.61 mm at 3 months and 3 ± 1.56 mm at 6 months. However, the difference between the width of the keratinized tissue at 3 and 6 months was not statistically significant (P = 0.343) [Table 3].

Table 2

Width of keratinized tissue

Site number	Baseline (WKT 0), mm	3 months (WKT 1), mm	6 months (WKT 2), mm
1	2	7	7
2	2	7	6
3	2	5	6
4	3	5	5
5	1	3	3
6	2	2	2
7	3	6	5
8	1	6	6
9	1	4	4
10	3	7	6
Mean width	2±0.81	5.2±1.75	5±1.56

WKT Width of keratinized tissue; mm - Millimeter

Table 3

Comparison between width of keratinized tissue at baseline, 3-, and 6-month intervals using paired t-test

	Mean increase in width of keratinized tissue (mean±SD), mm	P
Baseline versus 3 months (K1)	3.2±1.61	<0.001*
Baseline versus 6 months (K2)	3±1.56	<0.001*
3 months versus 6 months (K3)	− months	0.343

*P<0.05 is considered significant, *Statistically significant value. K1 Increase in width of keratinized tissue at 3 months; K2 Increase in width of keratinized tissue at 6 months; K3 Change in width of keratinized tissue from 3 to 6 months; SD Standard deviation; mm - Millimeter; P - Probability value

DISCUSSION

The soft-tissue adaptation to the implant abutment forms the first line of defense to prevent the development of peri-implantitis. The health of peri-implant tissues is vital for the success and longevity of the implants.[17]

The connective tissue graft and acellular dermal allograft can be used to augment the zone of keratinized tissue around the dental implants, but the free gingival graft still remains the gold standard to increase the width of attached gingiva. Therefore, the aim of this prospective clinical study was to increase the width of keratinized tissue around dental implants using a free gingival graft and to evaluate the amount of increase in the width of keratinized tissue achieved over a period of 6 months.

The plaque scores were reduced at 6 months compared to the baseline. The decrease in the plaque scores indicated efficiency of the patients in maintaining the areas plaque free. This finding was in accordance with the study done by Kennedy et al., who concluded that it was easier for patients to maintain oral hygiene in areas of adequate keratinized tissue.[18] Similarly, reduction in mean gingival index was not found to be significant when compared at 3 months and at 6 months of evaluation in this study. Mehdi Adibrad et al. found a higher amount of bleeding on probing and gingival inflammation around implants surrounded by a loose nonkeratinized tissue.[19] On clinical examination, a healthy sulcular depth was achieved in all the 10 implant sites at 3- and 6-month intervals, which was suggestive of a healthy peri-implant soft tissue. Evaluation with a periodontal probe represents a simple and good technique to evaluate the health of peri-implant tissues. The papillary index indicated a complete fill of embrasure spaces with interdental papilla and maturation of the graft. This outcome further supports the results drawn in a study that stated that the formation of the interdental papilla is completely unpredictable with mobile nonkeratinized tissue and a firm zone of keratinized tissue is needed for a predictable interdental papilla formation.[15] Further, a study conducted by Zigdon and Machtei showed a greater mucosal recession around dental implants surrounded with inadequate keratinized tissue.[3]

Evaluation of the results showed that there was a statistically significant increase in the width of keratinized tissue at the 3rd and 6th months compared to the baseline. There was a slight reduction in the width of keratinized tissue at the end of 6 months as compared to the 3-month value, suggesting a slight shrinkage in the graft during maturation and healing. Graft immobility is of utmost importance during the healing period of the free gingival graft [Table 3].

Yan et al. compared the free gingival graft and acellular dermal allograft for soft-tissue augmentation around implants and concluded that though acellular dermal allograft has an advantage of a better color match and reduced patient morbidity, it is associated with a delayed wound healing and a greater shrinkage as compared to a free gingival graft.[11] A 57% contraction of the acellular dermal allograft compared to a 16% contraction for the free gingival graft was reported by Rose and Sullivan et al.[20]

The increase in the width of keratinized tissue with a healthy peri-implant tissue was achieved at the implant sites with the augmentation of FGG and regular oral hygiene maintenance by the patient.

CONCLUSION

Within the limitations, the study evaluated the application of free gingival graft to increase the width of keratinized tissue around dental implants and assessed the health of peri-implant tissues over 6 months postoperatively. The results demonstrated a significant increase in the width of the keratinized tissue at 3 and 6 months postoperatively. Healthy implant/soft-tissue interface aids in achieving a stable implant/soft-tissue interface, which is eventually important for the long-term success of the dental implant. However, larger sample size and longer follow-up periods are essential to evaluate the further prognosis of the free gingival graft in increasing the width of inadequate keratinized tissue around dental implants.

Recommendations

In the future, more prospective studies are necessary to evaluate the effect of increasing the width of keratinized tissue around implants with a free gingival graft on peri-implant tissue health and whether this procedure offers long-term benefits to the patients.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.