Elsevier

Bone

Volume 34, Issue 4, April 2004, Pages 665-671
Bone

Effect of platelet concentration in platelet-rich plasma on peri-implant bone regeneration

https://doi.org/10.1016/j.bone.2003.12.010Get rights and content

Abstract

This study analyzed the effect of the platelet count in platelet-rich plasma (PRP) on bone regeneration in vivo.

Twenty male New Zealand white rabbits were used. PRP was produced using the Platelet Concentrate Collection System (PCCS) (3i, Miami, FL, USA). After inducing ketamine–xylazine anaesthesia, a self-tapping titanium screw (Branemark MK III TiUnite, 3.75 × 7 mm) was inserted in each distal femur; the femurs were randomized so that one side was treated with PRP while the other (control) was not. Intravital fluorochrome staining was performed on days 1, 7 (1.5 ml of 2% doxycycline/kg bodyweight), 14 (6% xylenol orange, 1.5 ml/kg), and 21 (1% calcein green, 5 ml/kg). Animals were euthanized on day 28 (n = 20). Specimens were prepared for histomorphological evaluation according to Donath and Breuner [J. Oral Pathol. 11 (1982) 318].

Comparing the bone regeneration (fluorochrome staining) in the 4-week implants (n = 19), the only significant difference (sign test, P = 0.004) was seen with intermediate platelet concentrations (n = 9,503,000–1,729,000 platelets/μl PRP).

There were no differences in the bone/implant contact rates between the test and the control side among the three groups.

The platelet concentration required for a positive PRP effect on bone regeneration seems to span a very limited range. Advantageous biological effects seem to occur when PRP with a platelet concentration of approximately 1,000,000/μl is used. At lower concentrations, the effect is suboptimal, while higher concentrations might have a paradoxically inhibitory effect. On the other hand, the effect of this type of platelet concentrate was not beneficial to accelerate the osseointegration of enosseous dental implants.

Introduction

Platelets contain a variety of autologous growth factors, including platelet-derived growth factor (PDGF), transforming growth factors β1 and β2 (TGF-β1 and TGF-β2), insulin-like growth factor (IGF), epidermal growth factor (EGF), and epithelial cell growth factor (ECGF), as well as a growth factor for hepatocytes [5]. In 1998, Marx et al. [7], [8] found that platelet-rich plasma (PRP) had a positive effect on bone regeneration, since it was a source of autologous growth factors. In 44 patients who underwent reconstruction of the mandible following resection, they demonstrated that the use of PRP in combination with autologous bone transplant led to increased bone regeneration and bone density. The use of PRP to support the osseointegration of endosseous dental implants also resulted in significantly increased bone regeneration in animal experiments [4], although there are some contradictory results [12].

This study analyzed the effect of PRP on peri-implant bone regeneration in a rabbit model and focused on the possible influence of the platelet concentration in the PRP.

Section snippets

Animal model

After receiving approval from our animal care committee, 20 male New Zealand white rabbits, weighing 3293 ± 259 g, aged 9–12 months, were used for this study. The animals were kept in individual cages in the institution’s animal care center and fed water and standard diet ad libitum.

PRP production

For the self-production of PRP, the Platelet Concentrate Collection System (PCCS System, 3i®, West Palm Beach, FL, USA) was used. After collecting 30 ± 2 ml of whole blood from the marginal auricular vein or the

Intravital fluorochrome staining

Transmission light microscopy was used to compare the implant position in the spongy bone of the epiphysis with respect to the metaphysis and the medullary cavity of the diaphysis of the femur, which lacks spongy bone. For the most part, regeneration was limited to the part of the implant in contact with spongy bone for both the control and PRP-treated groups. Therefore, only the fluorochrome staining in the area of spongy bone was evaluated histomorphometrically.

In the 4-week specimens (n =

Discussion

The fluorochrome staining method used in this study is an established method. The morphometrically determined bone surface areas can be used as a measure of bone regeneration [6], [11], [14].

The extent of the difference in fluorochrome staining between the test and control groups at intermediate platelet concentrations suggests an increase in peri-implant bone regeneration of about 90% with the use of concentrated PRP, which might be a clinically relevant difference. In their miniature pig

Conclusions

From the combined data on the biological effect of PRP, it can be concluded that PRP seems to be able to activate the osseous regeneration processes under optimized conditions. However, we do not fully understand the conditions necessary for it to stimulate osseous regeneration. The stimulatory effect of PRP in vitro on the proliferation of osteoblasts seems to start in vivo in the second week, can be evaluated statistically significant from the third week, and still exists in the fourth week.

Acknowledgements

The authors thank Ms. A.H. Loos of the Institute of Medical Biometry, Epidemiology and Informatics at the Johannes Gutenberg University of Mainz for her help with the statistical analysis. This study was supported by Nobel Biocare® Deutschland GmbH, Wankelstrasse 9, D-50996 Köln, Germany, and by 3i®, West Palm Beach, FL, USA, by providing the self-tapping Branemark® titanium screw implants and the Platelet Concentrate Collection System® for this study free of charge.

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