Platelet-Rich Fibrin in Membranes and Dental Implants

Abstract
Objectives: The aim of this research is to investigate the efficacy of the usage of Platelet Rich Fibrin in the area of dental field when used for implant stability, soft and hard tissue regeneration as well as wound healing.

Material & Methods: For this research, electronic searches were conducted, mostly from PUBMED, Indian journal of dental research and Journal of Applied Oral Science. The electronic literatures that were searched for articles were published up to 10 -15 years. Articles that were chosen for this research mention how Platelet Rich Fibrin aids in dentistry in the fields of oral implantology, soft and hard tissue regeneration and wound healing.

Results: From the articles that were researched, it was found that the use of PRF had a positive effect. In the main topics that were chosen (PRF effect on implants, PRF effect on hard and soft tissue, PRF effect on wound healing), in all of them PRF resulted in an increase and was found to assist in these different fields of dentistry to result in better and faster treatment and comfort for the patient. The increase may not have been major however; no negative results and major complications were found towards PRF.

Conclusion: In conclusion, Platelet Rich Fibrin was shown to improve soft and hard tissue regeneration, wound healing and implant stability when used in dentistry. However further studies and investigations are necessary.

Keywords: Platelet rich fibrin; Oral implant; Hard tissue regeneration; Soft tissue regeneration; Wound healing.

1. Introduction
Platelet-rich fibrin (PRF) t 1membrane is a three-dimensional biodegradable biopolymer, which consists of platelet-derived growth factors enhancing cell adhesion and proliferation. PRF does not require the addition of anticoagulants nor bovine thrombin, it is a second-generation autologous platelet concentrate¹³.

Choukroun et al⁶. developed PRF in 2001, it was prepared by withdrawing blood into glass tubes from the patients and then placed into a centrifuge, what happens then is that in the fibrin matrix there are entrapped platelets and leukocytes where a large amount of growth factors are formed from the platelets when they are activated and due do that, the molecules act as cell attractants and increase the proliferation of cells^27,12. When the centrifugation process is completed, hyper acute serum is collected from the PRF clot, which has very advantageous properties since it has an elevated effect of cell proliferation on the bone marrow mesenchymal stem cells, osteoblasts and osteoarthritic chondrocyte cells⁹. After the hyperactive serum fraction is removed the remaining PRF membrane is a three- dimensional, biocompatible, biodegradable scaffold, which can slowly and sustainably release bioactive molecules, which facilitate cell adhesion and proliferation^4,6.

PRF is widely used in the field of dentistry, especially in oral and maxillofacial surgery and periodontics⁷ because it is able to increase the adhesion and proliferate the capacity of gingival fibroblast, it increases new bone formation, improves wound healing, used in sinus lift procedures, soft tissue transplants, post extraction alveolar ridges, bone regeneration for future implants and prosthetic reconstruction²⁰. The tissue healing and regeneration takes place when PRF is placed and is caused by the effective creation of new vessels, accelerated wound closure and fast scar tissue remodeling. Despite an increasing use of PRF membranes, there is still no comprehensive review on their efficacy with regard to soft and hard tissue healing after implants insertion. The aim of this study is to evaluate the potential benefits of using PRF in the soft ad hard tissues implant stability and wound healing.
Thesis objective
For my thesis objective I would like to find out the efficacy of PRF when used as a membrane during implant insertion procedure. To research how PRF aids in soft tissues and hard tissue regeneration also to in the wound healing site.

2.Material and Methods
This article was conducted according to reviews of different articles. PICO question was developed which included definition of the focus question, a P (patient), I (intervention), C (comparison), O (outcome) question. Search strategy, inclusion/ exclusion criteria, data extraction, and outcome measure determination.

2.1 PICO Terms
P: Patients undergoing dental implant surgery.
I: Combining PRF (Platelet Rich Fibrin) while undergoing dental implant surgery.
C: Defined regenerative / reparative approaches with and without the use of PRF.
O: gingival tissues, periodontal tissues, wound healing, Osseo integration.

2.2 Defining the focused questions
For this article, there were different questions concerning the effectiveness of using Platelet rich fibrin (PRF), either it was to be used as a sole treatment or as a combined treatment. The questions were as follows; how would PRF acts as a barrier and as a biological connector when used in implant dentistry (could it improve the Osseo integration process of implant treatment)? How would PRF perform with regard to soft tissue healing?

2.3 Search strategy
For this article, electronic searches were conducted, mostly from PUBMED, Indian journal of dental research and Journal of Applied Oral Science. The electronic literatures that was searched for articles that were published up to 10 -15 years The search terms and strategies that were used were: 1 ((((((platelet rich plasma membrane) OR platelet rich plasma membrane) OR PRP membranes) OR PRP membrane) AND dental) OR platelet rich fibrin membranes) OR platelet rich fibrin membrane. From this combination 219 articles were found, and 42 articles were chosen. 2. ((PRF membranes) AND soft tissue healing) AND dental implants. From this search 3 articles were found and 2 were chosen. 3 (PRF membrane) AND mucosal healing. Here 8 articles were found and 6 selected 4 ((PRF membranes) AND osseointegration) AND dental implants. 4 articles found and 1 chosen.

2.4 Criteria for study selection and inclusion / exclusion
The study selection for this article that was considered were articles that were published only in the English language. Only human studies. (All animal studies were excluded.). Studies that evaluated the clinical effects of PRF (Platelet rich fibrin) in dentistry. The effects of PRF on the gingival tissues and periodontal tissues implant stability, osseointegration process and wound healing.

2.5 Number of included studies
From all of the searched studies, out of 52 articles, 29 articles were chosen for this thesis.

2.6 Data extraction and analysis
Data that was extracted from different articles were general characteristics such as authors, publications (up to 10 years), and reason of study, number of patients, treatment groups, baseline of the studies, PRF preparation techniques, and evaluated parameters, whether implants were placed and complications. Studies were extracted from the collection of articles and summarized into tables based on the topics and discussed accordingly.

2.7 Outcome measure determination
For each of the investigated clinical indication, different primary outcomes were considered. For studies involving wound healing; EHI, GML, Mean Soft Tissue Healing were measured. For studies dealing with implant stability; torque values, ISQ were measured. For studies involving extraction socket management; Alveolar crest height, mean bone density, radiography were being evaluated. For studies involving gingival recessions, KTW, CAL, PD, recession height, GRW were measured.

3. Results
3.1 PRF membranes
3.1.1 PRF membranes definition and preparation
PRF membrane is a patient blood derived and an autogenous living biomaterial that can be utilized as an adjunctive autologous biomaterial to back bone and delicate tissue recuperating and recovery. The critical dynamic components of PRF incorporate the common interaction between a framework (fibrin network), platelets, development variables, leukocytes, and stem cells. So when these elements are combined and arranged legitimately the method of tissue recuperating and recovery cell expansion and separation, extracellular lattice amalgamation, chemotaxis and angiogenesis (neo-vascularization) occurs.

For the PRF preparation, blood is withdrawn from the patient employing a sterile. The tubes with collected blood samples are promptly (within 2 minutes after collecting the blood sample) put within the centrifuge and processed employing a single centrifugation step. Failure to achieve the speedy arrangement of PRF may cause a diffuse polymerization of fibrin, which isn’t perfect for tissue.

At the end of the centrifugation spin the caps for A-PRF or L-PRF (not i-PRF) are expelled and the tubes are put in a sterile tube holder. The blood with the clot is put to rest/mature for around 4-8 minutes before removing the clot from the tube.

The centrifugation process activates the coagulation handle and isolates the blood test into three distinctive layers: acellular plasma at the best of the tube; a polymerized fibrin clot is shaped within the center; and blood cells ((red corpuscle base) are accumulated at the end of the tube.

There are diverse centrifugation preparing conventions that are right now being utilized. These incorporate; Unique Choukroun et al. PRF convention (standard convention): 3,000 rpm/10 minutes, Choukroun et al. progressed PRF (A-PRF), enriched with leukocytes: 1,300 rpm/ 8 minutes, Choukroun et al. I-PRF (solution/gel): 700 rpm/3 minutes, Ehrenfest et al. bunch (leukocyte- and platelet-rich fibrin [L-PRF]): 2,700 rpm/12 minutes6,19.

In vitro studies it appeared that a longer centrifugation speed (2,700 rpm) produce a denser fibrin clot with less inter-fibrous space containing less cells compared to the shorter centrifugation speed of A-PRF (1300 rpm) that creates a less thick fibrin clot with a looser inter-fibrous structure containing more cells8.

3.1.2 Biological  and  mechanical  properties  of  PRF membranes
The key biological functions of PRF are the bioactive barrier and the Competitive interposition barrier. What is meant by these two terms is that in the bioactive barrier, when the PRF membrane is prepared clot forms, which is rich in cells and growth factor, so these components act as a natural bioactive barrier allowing interaction with the tissues below and above it14.15.

In the competitive interposition barrier such as the GTR (Guided Tissue regeneration) barrier are cell proof barriers against soft tissue invagination, on the other hand PRF membranes allow cells to migrate through it, which allows new blood vessels to form which will lead to regeneration and healing between the tissues below and above the PRF membrane15.

Advantages and disadvantages of PRF membranes
The main advantages of PRF in repair and recovery processes are that PRF could be a common biomaterial; it is simple and proficient to use, cost effective and successful. It is expected that it is has an expanded clinical performance since it shows a more exhibited expression, concentration of growth factors and matrix proteins. It is safe, it has increased healing potential, reduced morbidity. However there are limitations as PRF lacks rigidity and causes fast degradation, which reduces the application in procedures. Also at present, very little is understood about PRF generated from patients with coagulation disorders or patients on medications that affect blood clotting (heparin, warfarin, or platelet inhibitors)6.

3.2 Effect on implant stability
3.2.1 Characteristics of included studies
Implant stability is a critical factor resulting in success when setting implants. Four articles considered the connection of PRP layers and embed stability, and to this end they assessed parameters for embed soundness were ISQ (Embed Solidness Remainder), Addition torque and sort of bone quality (Table 1). The patients that took portion in these ponders were separated into bunches PRF vs. Non- PRF All ponders utilized comparative arrangement strategies for the layer, pulling back 9-10 ml of persistent blood and centrifuging it for 10 - 12 minutes at 2000 – 3000 rpm. No complications were recorded within the studies during the treatment.

Table 1: Characteristics of studies on PRF membranes and implant stability.

 Table legend: rpm rounds per minute, ISQ implant stability quotient.

3.2.2 ISQ values
The results demonstrate that the application of PRF during implant surgery enhances the stability of implants and that is shown by the increased values of the ISQ.

In general there is an increase between all the groups the ISQ measurements, the results show that there is an increase in the PRF as well as in the non- PRF groups however the groups that had the PRF showed higher results.

Table 2: ISQ values with and without PRF membrane over time.

Table legend: P-values denote significant against each other with P<0.001.

3.2.3 Mean insertion torque
In the studies found, the patients that had undergone the In the studies that had used insertion torque as a parameter showed no significant difference between the groups. Nevertheless the group with the PRF had higher values.

Table 3: Mean insertion torque values with and without PRF membrane over time.

In the studies found, the patients that had undergone the studies were ranging in age between 18-52 years. In each study the patients were divided into different group treatments but each one included a group that combined PRF into the treatment (VRD+PRF vs. CTG, Gingival recession +LPRF vs. CTG, CAF vs. CAF+PRF, Mucogingival surgery+ PRF, MCAF+PRF and MCAF+SCTG).

Just in two studies minor complications were observed after surgery such as pain, swelling, bleeding, and inflammation of the gingiva. However these kinds of symptoms are normal after a surgery.

For the PRF preparation the blood drawn from the patients that took part in the studies were to be centrifuged. The blood samples that were withdrawn were between 6-10 ml and were being centrifuged at 2700-3000 rpm for 10-12 minutes.

 In the different articles the studies were between 3 - 12 months. The evaluated parameters for PRF membranes on gingival recession included the CAL (Clinical attachment level), PD (pocket depth), GT (gingival thickness), recession height and KTW (keratinized tissue width). 

Table 4: Characteristics of studies on PRF membranes and gingival recession.

3.3.2 Keratinized tissue width
The KTW increased in all the groups that were used as treatment modalities for gingival recessions. The groups that involved PRF showed higher values. Two studies included groups that were PRF vs CTG, and the other study included MCAF+PRF and MCAF+SCTG.

In the study by Jankovic et al. 2012 the KTW in the PRF group increased from 1.32 ± 0.66 mm to 2.20 ± 0.54 mm. In the control group, KTW increased from 1.41 ± 0.58 mm to 2.85 ± 0.45 mm. The gain in KTW was statistically significant for both groups. In a study by Tunali et al29. The statistical analyses for the clinical parameters at baseline and 6 months and 12 months post treatment for both groups. Both groups showed a significant increase in the KTW from baseline to 12 months; however, there were no statistically significant differences in the KTW between the two groups at baseline or at 12 months. It goes for the study by Öncü et al21 where KTW increases in time in both the groups.

Table 5: Keratinized tissue width values with and without PRF membranes over time.

Table legend: CTG (control group), PRF (platelet Rich Fibrin), MCAF (Modified Coronally Advanced Flap) SCTG (Subepithelial Connective Tissue Graft).

3.3.3 Recession height
Two studies studied difference between CAF vs PRF, and one study studied CTG vs PRF. Kuka et al. 2017 results of the recession height from the baseline in CAF + PRF and CAF groups was 3.15 ± 0.24 and 3.36 ± 0.34 mm, respectively. Intragroup comparisons revealed significant differences at 12 months for all parameters (p < 0.05). Recession height reduction was 2.75± 0.33 and 2.51 ± 0.33 mm in the CAF + PRF and CAF groups respectively. According to the study by Jankovic et al. 2012¹¹ the recession height in the PRF group decreased from 3.51±0.70 to 2.83±0.37.and in the CTG group from 3.45±0.84 to 3.07±0.30, it is shown that the differences between the groups were not statistically significant. In Dixit et al. study from baseline to 6 months the recessions height in both the groups also resulted in the decrease, however the results were not statically significant⁵.

Table 6: Recession height values with and without PRF membranes over time.