Efficacy of leukocyte–platelet-rich fibrin membrane in immediate postextraction implant placement: A randomized controlled trial

Abstract

Background:

Leukocyte–platelet-rich fibrin (L-PRF) membrane is an emerging autologous healing biomaterial that promotes angiogenesis and healing in immediate implant sites. The purpose of the study was to evaluate hard and soft tissue outcomes of immediate implant placement with or without L-PRF.

Materials and Methods:

A total of 18 immediate implants were divided randomly into two groups of 9 implants each, i.e., Group 1 and Group 2. All sites received a definitive restoration after 3 months of implant placement and were followed up for a period of 6-months.

Results:

Addition of L-PRF in the extraction sockets when placing immediate implants resulted in statistically nonsignificant benefit in terms of clinical and radiographic parameters when compared to immediate implant placement without L-PRF.

Conclusion:

Immediate implant placement in Group 2 demonstrated marginal but statistically significant benefit as compared to sites in Group 1.

INTRODUCTION

Immediate dental implants have revolutionized implant dentistry by drastically shortening the treatment time. Immediate placement of dental implants in an extraction socket was initially described by Schulte and Heimke in 1976.[1] At present, it is a well-accepted protocol due to its various benefits like enhanced soft tissue esthetics and shorter treatment time as it reduces the number of surgical interventions.[2]

Immediate implant when placed in a fresh extraction alveolus may results a gap in between implant surface and the socket wall which is due to the difference in the implant size, shape and extraction socket morphology. Later, remodeling results in resorption and at times may leave some portion of the implant exposed resulting in poor esthetic outcomes. Gaps <2 mm heal spontaneously, whereas larger gaps may require the use of bone grafts and barrier membranes or combination of both for better healing.[3]

To increase the success of immediate implants, use of modified surgical techniques and various augmentation procedures such as autografts, bone substitutes, and platelet-rich plasma has been tried with varying degrees of benefits and drawbacks.[4] Another potential regenerative strategy for promoting and enhancing the healing process in the postextraction alveolus is leukocyte–platelet-rich fibrin (L-PRF). It has already gained acceptance in oral surgical procedures, specifically in alveolar ridge preservation.[5] Since L-PRF contains most of the platelet aggregates, leukocytes, and growth factors, this second-generation platelet concentrate performs better in terms of improving healing due to slow release of growth factors of the fibrin matrix.[6–8] PRF may act as a biobarrier due to its membrane-forming ability, which results in adequate socket preservation.[9,10] This autologous healing biomaterial is inexpensive and quick to prepare.[11]

Ironically, current evidence supporting the use of L-PRF as a biomaterial in immediate implant placement is quite scarce. Present randomized controlled trial (RCT) was, therefore, planned to evaluate the clinical efficacy to L-PRF in postextraction immediate implants.

MATERIALS AND METHODS

The present study was planned and conducted in the department of periodontology and oral implantology after getting approval from the institutional review board. This RCT was planned with the aim to clinically and radiographically access the efficacy to L-PRF in the immediate extraction sockets in sites recruited for immediate implant placements. The inclusion criteria were subjects aged between 18 and 65 years with good oral health and sufficient bone volume and porous cortical and dense trabecular bone at the site of immediate implant placement with no acute infection.[12] Sites indicated for immediate implants that require extraction included root fractures, grossly decayed roots, or root resorptions.[13,14] The exclusion criteria for subjects in this study were the patients with inadequate oral hygiene, current smokers, tobacco consumers, or patients with systemic disease or condition that might interfere with implant placement.[15] Patients with traumatic occlusion and teeth with periapical pathologies were also excluded.[13,16,17]

Recruitment of the patients was done during the period from October 2018 to June 2019 and all postoperative recall appointments were commenced till January 2020. Only the patients who were willing and gave their written consent were enrolled for the trial. The power of the study was calculated for the purpose of sample size calculation; the accepted variances, i.e., type 1 error was set to be 5% (P = 0.05) and the accepted type 2 error was set to be 20%, thus making power of the study to be 80%. A total of 18 immediate implant sites were included without any dropouts. “Research Randomizer software” was used for randomization of implant sites to either of the groups and a sealed opaque envelop was used for allocation concealment. The study was a single-blinded study where only the evaluator was blinded about the intervention. The patients involved in the study could not be blinded as blood had to be drawn for the preparation of L-PRF in patients allocated to Group 2. All the implants were placed by the same operator and the size ranged from 3.75 to 4.5 mm diameter. Study cast and preoperative radiographs including intraoral periapical radiograph and orthopantomograph were considered for the availability of native bone, bone shape, quality, quantity, bone width and height, and sufficient distance available coronal to the maxillary sinus and floor of the nose. The patients were subjected to Phase I therapy, which included scaling, polishing, and root planing. This was done prior to implant placement and proper oral hygiene instruction was given. Meticulous plaque control was done by all the patients and plaque index score was kept under one. The implant sites were randomly allocated into two groups [Figure 1].

Figure 1.

CONSORT diagram for randomization (n = no. of participants), (L-PRF = Leukocyte–platelet-rich fibrin)

• GROUP 1: Nine sites were treated with immediate implant placement without L-PRF membrane placement [Figure 2]

• GROUP 2: Nine sites were treated with immediate implant placement along with the use of L-PRF membrane [Figure 3].

Figure 2.

Surgical procedure of patient without leukocyte–platelet-rich fibrin membrane. (a) Preperative photograph. (b) Extracted root stumps. (c) (Implant placement, (d) Gingival former placed. (e) Implant abutment placed. (f) PFM crown delivered. (g) Preoperative radiograph. (h) Postoperative radiograph

Figure 3.

Surgical procedure of patients with leukocyte–platelet-rich fibrin membrane. (a) Patient blood drawn. (b) Centrifugation of the blood. (c) Preoperative photograph. (d) Extracted root stump. (e) Leukocyte–platelet-rich fibrin membrane prepared. (f) Implant placement with Leukocyte–platelet-rich fibrin membrane. (g) Postoperative suturing. (h) Posttreatment view (i) Preoperative radiograph. (j) Postoperative radiograph

L-PRF Preparation: The preparation of the L-PRF was done from the venous blood of the patient on the same day before the immediate implant surgery. About 10 ml of blood was drawn from the patient and collected in sterile Vacuette tubes (VACUTECH PRF TUBES, India). After collection of blood, it was immediately centrifuged on manual mode at a rate of 2700 rpm for 12 min (DENTIST’S CENTRIFUGE LABTECH, Gujarat, India). To prepare L-PRF membrane, L-PRF clot was transferred to the pressboard of PRF box and a compressor lid was placed in its position for 1 min after which L-PRF membrane of uniform thickness was obtained. This step ensures that the membrane remains hydrated for several hours.

Surgical Procedure: To administer local anesthesia intraorally, required nerve blocks were performed as per the anatomical requirement of surgical site by injecting a 2% solution of lignocaine hydrochloride with 1: 80,000 adrenaline (LIGNOX 2%, INDIA). The teeth were carefully extracted using forceps or Piezotome to protect and preserve the alveolar bone. Care was taken to preserve the integrity of the buccal and lingual cortical plates. The socket was curetted and irrigated with sterile saline to ensure that no debris or bone chip is left. The depth of the socket was measured to determine the amount of drilling required beyond the root apex tip. Drilling was performed at 600–800 rpm at the predetermined direction being guided by the surgical drill guide of an implant. Copious saline irrigation was done to prepare the osteotomy site with a physiodispenser (ACTEON). Sequential drilling was carried out until the desired dimensions were achieved depending on the selected implant size. Manual key and rachet were used for implant insertion. Implants were placed 2–3 mm beyond the apex in the post extraction socket to achieve good primary stability.[13] Length and width of the implant in each and every case was calculated according to the preoperative radiographic; clinical parameters and all implants were placed slightly below or at the crestal bone level. Each implant was placed manually and rotated clockwise until resistance for seating was achieved. Complete seating of the implant was carried, so that the coronal part of the collar of an implant was at or below the crestal bone level of the alveolar ridge. The cover screw was then screwed on the implant body and placement protocol followed the manual of Alpha-Bio Tec. (ALPHA BIO_TEC, I.C.E, ISRAEL).

The L-PRF membrane was placed to fill the gap between implant and socket wall in Group 2 patients along with same technique as described above for Group 1. The flap margins were repositioned and sutured tension free applying simple interrupted sutures with 3-0/4-0 braided silk suture. Patients were recalled at the 10^th day for suture removal and various clinical and radiographic parameters were recorded at 1 month, 3 months, and 6 months. The recall intervals were in accordance with Del Corso et al., 2012, and Öncü and Erbeyoğlu, 2019.[12,17] The second stage surgical procedure was done after 3 months and gingival former was placed wherever tissue adaptation was inadequate and later prosthesis was given.

Primary outcome variables included tissue biotype assessment, peri-implant bone loss, and radiolucency. At the implant site, local anesthetic was administered after which the tissue thickness was measured using an endodontic reamer (size 20-yellow) with a stopper. The thickness of the tissue was determined by the depth of penetration of the reamer from the external surface of the mucosa to the point where bony resistance could be felt. Sites with mucosal thickness of 2.0 mm or more were categorized as a thick biotype and those <2.0 mm were categorized as a thin biotype.[18] The marginal bone around implants is considered as a significant indicator of implant health. Postoperative radiographs with grid were obtained for measuring marginal bone loss between the fixture-abutment junction and the most coronal level of the bone on the radiograph. Bone loss was calculated in mm by digitalizing the radiograph and calculating the value. Peri-implant radiolucency at subsequent visits was observed and recorded on intraoral periapical radiographs as 0 which represents radiolucency absent at any bone to implant contact site, whereas 1 represents radiolucency present at any bone to implant contact site.[19]

Secondary outcome included peri-implant pocket depth and implant stability. Probing depth was recorded at 4 sites around implant (mesial, distal, buccal, and lingual) in mm.[13] Hu-Friedy Colorvue® periodontal probe with Williams marking was used to determine the probing depth around the implant from the gingival margin to the base of the sulcus. Clinical Implant Mobility Scale was used to determine implant stability (2008).[20]

Statistical analysis

The data obtained were fed into Microsoft Excel 2000 package and descriptive statistics was performed by calculating mean and standard deviation for the continuous variables. The statistical tests used were unpaired t-test and Chi-square test. All the statistical analyses were performed using Statistical Package for the Socialsciences version 25.0 (IBM SPSS Statistics, IBM corp., 2018) and P < 0.05 was considered statistically significant.

RESULTS

All the 18 patients completed their follow-up visit and there were no dropout. The outcomes were assessed by a single-blinded assessor. In our implant sites, the mean peri-implant probing depth for both the groups was below 3 mm at all recall intervals. In Group 1, when the means of peri-implant pocket depth were taken and intergroup comparisons were made, means increased slightly from 3 months (1.63) to 6 months (2.01). Similar findings were seen for Group 2 patients [Table 1], though the increase in the mean probing depth in both the groups was statistically non-significant (P = 0.774).

Table 1.

Comparison of peri-implant probing depth at different time points between two groups

Peri-implant probing depth	Mean±SD		Mean difference	t-test	P
	Group 1	Group 2
3 months	1.63±0.45	1.71±0.50	−0.08	−0.335	0.742
6 months	2.01±0.61	1.92±0.65	0.09	0.292	0.774

Unpaired t-test, Statistical significance at P<0.05, Nonsignificant difference (P≥0.05). SD – Standard deviation; P – P-value

When tissue biotype was assessed, only one patient in the Group 1 demonstrated tissue thickness of 3 mm at 6 months, whereas there were three patients in Group 2 who showed tissue thickness of 3 mm at 6 months. On comparing the mean distribution of tissue biotype in both Group 1 and Group 2, statistically nonsignificant difference was seen between baseline, 1 month, 3 months, and 6 months using the Chi-square test [Table 2].

Table 2.

Comparison of tissue biotype at different time points between two groups

Tissue biotype	Mean±SD		Mean difference	t-test	P
	Group 1	Group 2
Baseline	1.56±0.73	1.67±0.87	−0.11	−0.295	0.772
1 month	1.33±0.50	1.67±0.87	−0.33	−1.000	0.332
3 months	1.44±0.73	1.89±0.93	−0.44	−1.131	0.275
6 months	1.56±0.73	2.00±0.87	−0.44	−1.180	0.255

Unpaired t-test, Statistical significance at P<0.05, Nonsignificant difference (P≥0.05). SD – Standard deviation; P – P-value

When comparing the mean value of clinical mobility at different recall intervals between Group 1 and Group 2, statistically nonsignificant difference was seen at baseline (P = 1.000), 3 months (P = 0.444), and 6 months (P = 1.000) [Table 3]. In intergroup comparison of sites in both the groups followed the same pattern for implant placement therefore, a nonsignificant difference was recorded between the groups.

Table 3.

Comparison of implant stability at different time points between two groups

Implant stability	Mean±SD		Mean difference	t-test	P
	Group 1	Group 2
Baseline	0.11±0.33	0.11±0.33	0.00	0.000	1.000
3 months	0.22±0.44	0.44±0.73	−0.22	−0.784	0.444
6 months	0.33±0.50	0.33±0.50	0.00	0.000	1.000

Unpaired t-test, Statistical significance at P<0.05, Nonsignificant difference (P≥0.05). SD – Standard deviation; P – P-value

Mean marginal bone loss at different recall intervals was compared, on intergroup comparison between the Group 1 and Group 2; statistically nonsignificant difference was found at baseline (P = 0.659), 1 month (P = 0.816), 3 months (P = 0.485), and 6 months (P = 0.323) [Table 4].

Table 4.

Comparison of Marginal bone loss at different time points between two group

Marginal bone loss	Mean±SD		Mean difference	t-test	P
	Group 1	Group 2
Baseline	0.20±0.29	0.26±0.29	−0.06	−0.450	0.659
1 month	0.47±0.42	0.53±0.56	−0.06	−0.237	0.816
3 months	0.81±0.46	0.64±0.49	0.16	0.715	0.485
6 months	0.93±0.51	0.68±0.53	0.25	1.019	0.323

Unpaired t-test, Statistical significance at P<0.05, Nonsignificant difference (P≥0.05). SD – Standard deviation; P – P-value

Peri-implant radiolucency around implants was observed at different time intervals placed in both the groups. Nonsignificant difference was observed when comparisons were made at baseline (P = 1.000), 1 month (P = 0.527), 3 months (P = 0.599), and 6 months (P = 0.599) using Chi-square test [Table 5].

Table 5.

Comparison of peri-implant radiolucency at different time points between two groups

Peri-implant radiolucency	Group 1	Group 2	χ2	P
Baseline
0	8 (88.9)	8 (88.9)	0.000	1.000
1	1 (11.1)	1 (11.1)
1 month
0	8 (88.9)	7 (77.8)	0.400	0.527
1	1 (11.1)	2 (22.2)
3 months
0	7 (77.8)	6 (66.7)	0.277	0.599
1	2 (22.2)	3 (33.3)
6 months
0	7 (77.8)	6 (66.7)	0.277	0.599
1	2 (22.2)	3 (33.3)

Chi-square test, Statistical significance at P<0.05, Nonsignificant difference (P≥0.05). P – P-value; χ² – Chi-square

DISCUSSION

The biological intention behind immediate implant placement is to prevent the postsurgical bone resorption seen following tooth extraction. The chief drawback of postextraction immediate implants which risks the overall implant survival is the presence of gap between the extraction socket and implant surface.[3] Advances in implant therapy have evaluated various hard and soft tissue substitutes to be placed during implant placement in an attempt to accelerate healing and improve chances of implant survival. The present trial investigated the benefits of L-PRF assessing its novel use alongside the implant in the extraction sockets. All the 18 sites selected for immediate implant therapy in our study had teeth or root stumps extracted following atraumatic protocol to preserve the buccal cortical plate. It was ensured that the implant was placed 2–3 mm beyond the apex of the existent natural tooth.[13] Osteotomy was done using piezosurgical unit or extraction forceps, so that the minimum gap remains between the surface of implant and socket wall.[21] The inspiration behind exploring the possible usage of L-PRF membrane in immediate implants placement was drawn from the studies conducted by Öncü and Erbeyoglu AA, 2017,[17] and Omar Ragab, 2013.[21]

Peri-implant probing depth was evaluated at 3 months and 6 months using the Hu-Friedy Colorvue^® periodontal probe with Williams marking graded in mm, which has a vivid yellow tip and black markings that provide superior contrast for better visualization and plastic probe prevents unnecessary scratches on the implant surface; thus, it has been proved safe to use around implants.[22] In our trial, mean peri-implant probing depth was recorded to be below 3 mm at all time intervals for both the groups. Mombelli et al. have reported a maximum mean probing depth of 3.9 mm for successful implant, whereas probing depth > 5 mm may be considered as failing implants.[23]

When comparing the mean value of peri-implant probing depth at different recall intervals between Group 1 and Group 2, statistically nonsignificant results were found at 3 months (P = 0.742) and at 6 months (P = 0.774) [Table 1]. As the value was less in Group 2 patients as compared to Group 1 at 6 months, L-PRF in Group 2 sites could have acted as a healing biomaterial for both hard and soft tissues because of the presence of various growth factors. Peri-implant probing depth can be considered to be an outcome of keratinized mucosa around implant. Patients in both the groups maintained satisfactory plaque control, resulting in minimal inflammation around peri-implant soft tissue.[24] This might explain the nonsignificant difference in the peri-implant probing depth of both the groups.

In our study, gingival tissue biotype was measured using an endodontic reamer (size 20-yellow) with a stopper. Studies have reported that gingival biotype is correlatable with the thickness of the underlying buccal plate.[25] Therefore, its assessment was done to evaluate soft tissue parameter around immediate implants. Gingival tissue thickness >3 mm in buccolingual dimension was demonstrated by three patients at 6 months recall, although a statistically nonsignificant difference was observed between the groups. Factors that play a modifying role in the gingival tissue biotype include operator variables such as surgical and restorative techniques. These were taken care of as the same operator placed implants for both the groups. Other factors that impact the tissue biotype are preextraction condition of the buccal plate, soft tissue volumetric deficiencies, and wound healing potential. Recruitment of patients for the trial adhered to strict inclusion and exclusion criteria, thereby eliminating any potential bias. Our study could not demonstrate any benefit of L-PRF in terms of gingival tissue biotype probably due to a smaller sample size.

On intergroup comparison of the mean values of clinical mobility in both the groups, a nonsignificant difference was recorded between the groups [Table 3]. This could be due to the fact that in all the patients irrespective of the group, a minimum insertion torque applied was 30–45 Ncm to ensure adequate primary stabilization.[26,27] Since primary stability has been recognized as an important prerequisite for the achievement of osseointegration, all the implants in both the groups were placed 2–3 mm beyond the apex of the existent natural tooth or root to compensate for bone loss and also ensure adequate primary stability, thereby impeding any clinical mobility at baseline.[13]

Radiographic parameters evaluated in the study included marginal bone loss and periapical radiolucency.[22] All evaluations were done using standardized intraoral periapical radiographic projections with a standardized grid. Cone-beam computed tomography (CBCT) was not taken as IOPA radiographs and orthopantomograms were able to decipher and help to evaluate bone quality and anatomical landmarks for immediate implant placement. Furthermore, cost of CBCT was a discouraging factor and, therefore, it was not used. Marginal bone loss recorded <1 mm for both the groups, which was within the normal limit of bone loss measured around an implant over a year (<1–2 mm in the 1^st year after implant placement).[28] Studies have shown that ridge height alteration continues in the extraction socket even after the placement of immediate implants. These remodeling processes explain the highly significant difference between the marginal bone levels at different time intervals for sites in both the groups[29] [Table 4]. Osteotomy site for both the groups was enlarged using the final drill that was slightly undersized to increase the initial stability of the immediate implants.[24] When comparing the means of peri-implant radiolucency at different recalls in both the groups, a statistically nonsignificant difference was observed [Table 5]. This could be due to focal peri-implant radiolucency that might be a part of normal bone remodeling process and not pathological, because this study followed standard protocol for case selection and extraction of the root stumps and excluded the teeth with any preoperative periapical radiolucency, so that implant failure chances decreases.[30]

The comparative evaluation of clinical and radiographic parameters in our study did show some advantages of employing L-PRF in the extraction sockets when placing immediate implants, but these advantages were statistically insignificant.

CONCLUSION

It may be stated that L-PRF does offer benefits when placed in the extraction sockets for immediate implant placement sites in terms of a thicker tissue biotype. Improved healing could be best assessed by a histological investigation, which could not be executed due to esthetic and patient compliance concerns. Due to a smaller sample size and short follow-up period, it may be stated that the results obtained cannot be fully extrapolated or generalized. Therefore, a larger sample size and longer follow-up periods should be advocated to draw definitive results regarding the clinical and radiographic benefits of using L-PRF in immediate implant placement.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.