i-PRF: what is liquid PRF, and when is it used?

What is i-PRF (liquid PRF)?

i-PRF stands for injectable platelet-rich fibrin and is the liquid version of PRF. The blood is drawn into tubes without anticoagulants and briefly centrifuged. The top fraction contains platelets, white blood cells, fibrinogen, and thrombin that have not yet been converted into a fibrin clot. Therefore, it remains liquid for a short period, so it can be drawn up into a syringe.

After application, the liquid gradually clots and forms a fibrin network, which contains platelets and leukocytes, among other things. A systematic review published by Farshidfar et al. in Periodontology 2000 in 2025 compiled 23 studies of i-PRF and PRP. Based on the studies the review refers to, the authors describe the release of growth factors from i-PRF as longer than from PRP, but limited to around 10-14 days. This is the authors' description of earlier studies, not something the review itself measured. On that basis, the authors highlight i-PRF as relevant for, among other things, bone and periodontal regeneration and soft tissue healing around implants, but they emphasize that the evidence is limited and call for more clinical trials.¹

We cover how liquid PRF differs from solid PRF and membranes in our guide to Platelet-Rich Fibrin.

How is liquid PRF produced?

i-PRF was developed based on the so-called low-speed centrifugation concept: a slower and shorter centrifugation that leaves a liquid PRF fraction. Hydrophobic plastic tubes also help the liquid remain liquid.¹

The same research group has since investigated horizontal centrifugation. In a review also in Periodontology 2000 in 2025, Farshidfar et al. compiled 75 studies of PRF produced on horizontal centrifuges. 13 of them directly compared it with a fixed-angle centrifuge: 11 found an advantage with horizontal centrifugation, 2 found no difference, and none found an advantage with a fixed angle. For liquid PRF, horizontal centrifugation yielded a higher concentration of platelets and white blood cells. The advantage was measured in the laboratory, and the authors call for clinical trials.²

Horizontal centrifugation also has a practical advantage when liquid and solid PRF are to be used together, e.g. for sticky bone. On a horizontal centrifuge, both types of tubes can be centrifuged at the same time using the same protocol. On a fixed-angle centrifuge, the tubes for liquid PRF must be removed before the tubes for solid PRF, otherwise they may clot.²

What variants of liquid PRF are there?

Standard i-PRF is harvested from the top of the tube. The review on horizontal centrifugation describes newer variants, which are currently mostly documented in laboratory studies:²

• C-PRF (concentrated PRF). The blood is centrifuged at a higher force, so the cells collect in a thin layer just above the red blood cells. Harvesting exactly that layer increases the concentration of platelets and white blood cells more than tenfold compared to blood. Standard i-PRF on a fixed-angle centrifuge gave 1.5-2.5 times by comparison. 
• e-PRF (extended PRF). A further development of liquid PRF, where the platelet-poor plasma (PPP) is heated to an albumin gel and mixed with liquid PRF, so the material breaks down more slowly. In research, it is also called Alb-PRF. Read more in What is extended PRF?

What is i-PRF used for, and what do the studies show?

Because i-PRF is liquid, it can be injected directly into tissue or joints, and it can be mixed with other biomaterials before it clots.¹ Here are four areas in dentistry where i-PRF has been studied in randomized clinical trials. The evidence varies in strength: For thin gingiva and temporomandibular joint disorders, there are meta-analyses; for wisdom teeth, one trial; and for socket preservation, a small pilot trial.

Thin gingiva

Thin gingiva can be made thicker with a connective tissue graft, but this requires a donor site and can cause pain after the procedure. Instead, i-PRF is injected into the gingiva. A meta-analysis published by Idris et al. in BMC Oral Health in 2024 compiled seven randomized split-mouth trials with 178 patients with a thin gingival phenotype. Gingival thickness increased significantly after i-PRF at all follow-ups, by 0.12-0.38 mm compared to baseline. The width of keratinized gingiva increased significantly when four injections were given at ten-day intervals, but not with three injections. Combined with microneedling, i-PRF provided a slightly greater increase in thickness after six months.³

Most trials compared it with baseline or with another active treatment. In the one trial with an untreated control side, the increase was significantly greater with i-PRF. The trials used different protocols, e.g. different numbers of injections, and the one trial where only one injection was given found no difference from baseline. Only three of the seven trials had a low risk of bias, and the follow-up was 3-6 months.³

Temporomandibular joint disorders

For intracapsular temporomandibular joint disorders, i.e. disc displacement and osteoarthritis in the temporomandibular joint, i-PRF is injected into the upper joint space, most often after arthrocentesis. A meta-analysis published by Bahgat et al. in BMC Oral Health compiled six randomized trials with 270 patients. i-PRF resulted in significantly less pain and greater maximum mouth opening than the control groups, which in four of the trials received arthrocentesis alone. The authors found improvements in pain, joint noises, and jaw movements at follow-ups of up to 12 months. At the same time, they highlight that the trials differed greatly in patients, injection protocols, control groups, and follow-up time, that most were not blinded, and that there are only a few randomized trials in the field.⁴

Wisdom tooth removal

Aliberti et al. investigated i-PRF in Clinical Oral Investigations in 2025 after surgical removal of impacted wisdom teeth in the lower jaw. In the randomized trial with 56 patients, half received i-PRF infiltrated submucosally around the surgical site, and the person who measured the results was unaware of the group allocation. The i-PRF group had significantly less swelling on days 3 and 7, less pain on days 1 and 3, and better wound healing at all follow-ups from day 3 to day 21. No side effects were reported in the trial.⁵

Socket preservation with allograft

i-PRF can be mixed with bone substitute material. Talebi Ardakani et al. compared socket preservation with allograft alone and with allograft mixed with i-PRF in 20 alveoli in 12 patients in International Journal of Dentistry in 2024. After three months, the i-PRF group had lost significantly less width of the alveolar ridge, measured by CBCT as 0.67 versus 1.07 mm. Histological analysis showed a greater proportion of newly formed bone, 61 versus 44%, and fewer graft particle remnants. The difference in bone height was not significant. The authors call the results preliminary and call for larger trials with longer follow-up.⁶

For solid PRF in extraction alveoli, the documentation is broader. Al-Maawi et al. reviewed 20 randomized or controlled studies of PRF versus spontaneous healing in International Journal of Implant Dentistry. The loss of bone dimensions was less after 8-15 weeks, but not after six months, and four of the six studies that measured pain found less pain after the procedure. The studies used solid PRF, not i-PRF, and the authors assessed the risk of bias as high.⁷

For more on alveolar preservation after extraction, read What is socket preservation?, and you can find our allografts and other bone substitute materials under biomaterials. The amount and number of sessions are determined by the treating dentist.

What is the difference between i-PRF and PRP?

PRP is produced with anticoagulants and therefore remains liquid, and the production is more complicated.⁴ i-PRF is produced without anticoagulants and clots into a fibrin network after application. The Farshidfar review found 23 studies that directly compared the two and reported 25 comparisons: 18 favored i-PRF, 6 found no difference, and 1 favored PRP.¹

The overall preponderance of comparisons favoring i-PRF came especially from laboratory and animal studies. Of the eight clinical studies, 3 found an advantage with i-PRF, 4 found no difference, and 1 found an advantage with PRP. They concerned skin, the temporomandibular joint, orthodontic tooth movement, and pulp regeneration.¹

What equipment is needed for i-PRF?

For liquid PRF, a centrifuge, tubes without anticoagulants designed for liquid PRF, blood collection equipment, and syringes for application are required. Use the protocol for force and time that applies to the specific centrifuge and tubes you are working with.

• 

  PRF Centrifuge BP 200

  Horizontal swing-out centrifuge for producing PRF.

  See product →
• 

  Tubes for liquid PRF

  10 ml vacuum tube for i-PRF and sticky bone.

  See product →
• 

  Blood collection set

  Safety butterflies 21G with holder for venipuncture.

  See product →
• 

  PRF syringe 1 ml

  Luer Lock syringe for dosing liquid PRF.

  See product →
• 

  Understanding PRF, 2nd edition

  Textbook on PRF, edited by Richard Miron.

  See product →

See the full range of PRF equipment →

What does it take to work with liquid PRF?

The clinic must be able to perform venipuncture properly, and the practitioner must know the protocols for the centrifuge and tubes used. Force, time, and tube type determine what ends up in the syringe, and the liquid fraction must be used before it clots.

See courses in PRF and blood collection →

Frequently asked questions about i-PRF

Sources