Influence of PRP on autogenous sinus grafts. An experimental study on sheep

Exploring the applications of platelet-rich plasma in tissue engineering and regenerative medicine: evidence from goat and sheep experimental research

Platelet-rich plasma (PRP) has emerged as a promising therapeutic approach in regenerative medicine. It contains various growth factors and bioactive molecules that play pivotal roles in tissue repair, regeneration, and inflammation modulation. This comprehensive narrative review delves into the therapeutic potential of PRP in experimental goat and sheep research, exploring recent advancements, challenges, and future prospects in the field. PRP has been explored for its application in musculoskeletal injuries, wound healing, and orthopedic conditions. Studies have demonstrated the ability of PRP to accelerate tissue healing, reduce inflammation, and improve the overall quality of healing. Recent advancements in PRP technology have led to the development of novel formulations and delivery methods to enhance its therapeutic efficacy. PRP has shown promise in tendon and ligament injuries, osteoarthritis, and bone fractures in experimental goat and sheep research. Despite these advancements, several challenges and opportunities exist to harness the full therapeutic potential of PRP in regenerative medicine. Standardizing PRP preparation protocols, including blood collection techniques, centrifugation parameters, and activation methods, is essential to ensure consistency and reproducibility of the findings. Moreover, further research is needed to elucidate the optimal dosing, frequency, and timing of PRP administration for different clinical indications. Research conducted in goat and sheep models provides evidence supporting the translational potential of PRP in tissue engineering and regenerative medicine. By harnessing the regenerative properties of PRP and leveraging insights from preclinical studies, researchers can develop innovative therapeutic strategies to address unmet clinical needs and improve patient outcomes in diverse medical specialties.

Efficacy and Safety of Platelet-Rich Plasma on Bronchopleural Fistula: A Pilot Prospective Cohort Study

INTRODUCTION

Bronchopleural fistula (BPF) is associated with high morbidity and mortality rates in patients undergoing pulmonary resections. Surgery, bronchoscopy, and conservative management have their limitations for small fistulas. Platelet-rich plasma (PRP) has regenerative properties, which might be efficient in enhancing tissue recovery and repairing small BPF. This study aimed to investigate efficacy and safety of PRP on BPF.

METHODS

This is a pilot prospective cohort study. Patients whose fistulas smaller than 4mm were enrolled in this study, treated with PRP under bronchoscopy and followed up at 2 weeks and 4-6 weeks after the last PRP treatment. The cure rate, improvement rate and ineffectiveness rate were investigated. The severity of respiratory symptoms was evaluated by modified Medical Research Council dyspnea scale (mMRC) and COPD Assessment Test (CAT). The recurrence of fistula, new infection and mortality rate were examined. Adverse events were documented to explore the safety profile of PRP therapy.

RESULTS

A total of 16 patients (mean age, 50.1 years) met the eligibility criteria. The median time from the first PRP treatment to the closure of the fistula was 12.0 (IQR 6.0, 21.5) days. Our findings indicate an effectiveness rate of 87.6%, with 68.8% of cure and 18.8% of improvement, along with significant improvement of respiratory symptoms evaluated by mMRC (P<0.001) and CAT (P<0.001). No recurrent of fistulas, newly developed infection, or death was observed. Adverse events of the procedure were most mild (82.6%) and temporary.

CONCLUSIONS

PRP is a potential treatment for small BPF and is well tolerated.

Clinical Effect of Platelet-Rich Fibrin Combined with BIO-GENE Artificial Bone Meal in Bone Defects After Jaw Cyst Surgery

Purpose

To compare the clinical repair effects of leaving the defect empty and using Platelet-Rich Fibrin (PRF) combined with BIO-GENE artificial bone powder in patients with bone defects 6 months after jaw cystectomy.

Patients and Methods

From June 2021 to June 2022, 70 patients who were admitted to the Department of Stomatology, Affiliated Hospital of Yanbian University, and were diagnosed with jaw cysts postoperatively were selected. All of the patients were divided into two groups according to random method, among which 35 patients who underwent cystectomy alone were recorded as group A, which served as blank control; 35 patients who underwent cystectomy and PRF combined with BIO-GENE artificial bone meal repaired bone defects during the same period were recorded as group B. 3D Slicer 5.0.3 software was used to reconstruct Cone Beam Computed Tomography (CBCT) after operation. In this study, the preoperative and postoperative CBCT data of the patients were analyzed using 3D Slicer 5.0.3 software in DICOM format to calculate the cleft volume before surgery and the newly formed bone volume after surgery. The osteogenesis rate was measured based on these calculations.The bone formation percentage in the bone defect area was recorded at 6 months, and the clinical curative effects of the two groups were compared.

Results

After 6 months of surgery, the patients showed varying degrees of restoration in the jaw cyst area.The osteogenesis rate at 6 months in group A was 76.06±13.38%, while group B had a rate of 92.87±5.72%.The CBCT values in group B were higher than those in group A at 6 months post-surgery (P<0.05), t=-6.84.Group A and Group B showed a statistically significant difference.

Conclusion

Compared with simple cystectomy, PRF combined with BIO-GENE artificial bone powder has a better effect on the speed of bone repair after cystectomy within 6 months and provides more favorable effects for the repair of postoperative dentition defects, and provides support to repair teeth after defects such as dental implants.

Growth Factor Release within Liquid and Solid PRF

Aim: The purpose of this study was to obtain data concerning growth factor release within liquid and solid platelet-rich fibrin (PRF) matrices and to estimate the amount of potential interindividual variations as a basis for further preclinical and clinical trials. Therefore, we aimed to determine possible differences in the release of growth factors between liquid and solid PRF. Materials and Methods: Blood samples obtained from four subjects were processed to both liquid and solid PRF matrices using a standard centrifugation protocol. Five growth factors (vascular endothelial growth factor, VEGF; epidermal growth factor, EGF; platelet-derived growth factor-BB, PDGF-BB; transforming growth factor-β1, TGF-β1; and matrix metallopeptidase 9, MMP-9) have been evaluated at six time points by ELISA over a total observation period of 10 days (1 h, 7 h, 1 d, 2 d, 7 d, and 10 d). Results: Growth factor release could be measured in all samples at each time point. Comparing liquid and solid PRF matrices, no significant differences were detected (p > 0.05). The mean release of VEGF, TGFβ-1, PDGF-BB, and MMP-9 raised to a peak at time point five (day 7) in both liquid and solid PRF matrices. VEGF release was lower in liquid PRF than in solid PRF, whereas those of PDGF-BB and MMP-9 were higher in liquid PRF than in solid PRF at all time points. EGF had its peak release already at time point two after 7 h in liquid and solid matrices (hour 7 EGF solid: mean = 180 pg/mL, SD = 81; EGF liquid: mean = 218 pg/mL, SD = 64), declined rapidly until day 2, and had a second slight peak on day 7 in both groups (day 7 EGF solid: mean = 182 pg/mL, SD = 189; EGF liquid: mean = 81 pg/mL, SD = 70). Conclusions: This study detected growth factor release within liquid and solid PRF matrices with little variations. Further preclinical trials are needed to precisely analyze the growth factor release in larger samples and to better understand their effects on wound healing in different clinical indications.

Comparative study of bone regeneration using fibrin sealant with xenograft in rabbit sinus: pilot study

Background

Stability of the grafted bone volume is one of the important factors to the success of alveolar bone grafts. For this, platelet-rich plasma (PRP) or fibrin sealant is mixed with the bone graft material. Bio-Oss® is a protein-free bovine mineral commonly used in bone graft procedures. The grafting particles are commonly combined with a standard fibrin sealant (Tisseel®) to fabricate a plastic implantable product. The purpose of this experiment was to evaluate the efficacy of fibrin sealant (Tisseel®) in bone regeneration performance in a rabbit maxillary sinus model.

Methods

A total of five 3.5 kg weight New Zealand white rabbits were used for the study. After elevating the sinus membrane in both maxillary sinus cavities, Bio-Oss® mixed with normal saline (group 1) was filled into the right side, and Tisseel® mixed Bio-Oss® (group 2) was inserted into the other side. The bone mineral density and bone volume were analyzed with microscopic computed tomography (micro-CT) and histomorphometric 12 weeks after application.

Results

Histologically, new bone formation rate was 14.8%, and grafted bone rate was 70.5% in group 1. In group 2, they were 18.5% and 60.4%, respectively. According to micro-CT analysis, bone mineral density (mg/cm³, BMD) was 2.5% larger in group 1.

Conclusions

The findings from this study suggest that, although the difference in the bone formation between group 1 and group 2 appears to be insignificant, group 2 had an advantage in using smaller amount of bone substances to achieve the reliable bone formation.

Platelet concentrate as an additive to bone allografts: a laboratory study using an uniaxial compression test

Chemical cleaning procedures of allografts are destroying viable bone cells and denaturing osteoconductive and osteoinductive proteins present in the graft. The aim of the study was to investigate the mechanical differences of chemical cleaned allografts by adding blood, clotted blood; platelet concentrate and platelet gel using a uniaxial compression test. The allografts were chemically cleaned, dried and standardized according to their grain size distribution. Uniaxial compression test was carried out for the four groups before and after compacting the allografts. No statistically significant difference was found between native allografts, allografts mixed with blood, clotted blood, platelet concentrate and platelet concentrate gel regarding their yield limit after compaction. The authors recommend to chemical clean allografts for large defects, optimize their grain size distribution and add platelet concentrate or platelet rich plasma for enhancing as well primary stability as well bone ingrowth.

Efficacy of platelet concentrates in bone healing: A systematic review on animal studies - Part B: Large-size animal models

In the presence of large bone defects, delayed bone union, or nonunion and fractures, bone reconstruction may be necessary. Different strategies have been employed to enhance bone healing among which the use of autologous platelet concentrates (APCs). Due to the high content of platelets and platelet-derived bioactive molecules (e.g., growth factors, antimicrobial peptides), they are promising candidates to enhance bone healing. However, both preclinical and clinical studies produced contrasting results, mainly due to a high heterogeneity in study design, objectives, techniques adopted, and outcomes assessed. The aim of the present systematic review was to evaluate the efficacy of APCs in animal models of bone regeneration, considering the possible factors that might affect the outcome. An electronic search was performed on MEDLINE and Scopus databases. Comparative animal studies with a minimum follow up of 2 weeks, at least five subjects per group and using APCs for regeneration of bone defects were included. Articles underwent risk of bias assessment and quality evaluation. Fifty studies performed on six animal species (rat, rabbit, dog, sheep, goat, mini-pig) were included. The present part of the review considers studies performed on small ruminants, dogs, and mini-pigs (14 articles). The majority of the studies were considered at low risk of bias. In general, APCs' adjunct positively affected bone regeneration. Animal species, platelet and growth factors concentration, type of bone defect and of platelet concentrate used seemed to influence their efficacy in bone healing. However, sound conclusions were not drawn since too few studies for each large-size animal model were included. In addition, characterization of APCs' content was performed only in a few studies. Further studies with a standardized protocol including characterization of the final products will provide useful information for translating the results to clinical application of APCs in bone surgery.

A description of the sequence of long-term behavior of autogenous boneblock in maxillary sinus augmentation in sheep: Additional morphologic and histomorphometric evidence

OBJECTIVE

To document the behavior of autogenous bone block in sinus lift and surgical consequences.

STUDY DESIGN

Twelve sinus lifts with autogenous hip bone blocks and simultaneous insertion of two implants in 6 adult female sheep. Polychrome sequential labelling and histologic and histomorphometric evaluation after 6, 16, and 26 weeks.

RESULTS

Augmentation material in the apical third was almost fully resorbed after 26 weeks (P = .00388). Percentage of bone tissue increased 0.5-1.0 mm from the implant in crestal region (15.3 ± 7.5% to 16.2 ± 10.1%), whereas it vanished in the apical region from 16 to 26 weeks (4.2 ± 10.4% to 0%) (P = .363).

CONCLUSIONS

Autogenous bone block leaves an apical thin but functionally crucial layer covering implants in a form follows function way. Denial of animal-originated biomaterials and prion diseases remain a rarely discussed issue. The use of an implant length-adapted autogenous transplant with osseoinductive advantages should be taken into consideration.

Autologous blood preparations rich in platelets, fibrin and growth factors

OBJECTIVES

Bone regeneration is often needed prior to dental implant treatment due to the lack of adequate quantity and quality after infectious diseases. The greatest regenerative power was obtained with autologous tissue, primarily the bone alive, taken from the same site or adjacent sites, up to the use centrifugation of blood with the selection of the parts with the greatest potential regenerative. In fact, various techniques and technologies were chronologically successive to cope with an ever better preparation of these concentrates of blood. Our aim is to review these advances and discuss the ways in which platelet concentrates may provide such unexpected beneficial therapeutic effects.

METHODS

The research has been carried out in the MEDLINE and Cochrane Central Register of Controlled Trials database by choosing keywords as "platelet rich plasma", "platelet rich fibrin", "platelet growth factors", and "bone regeneration" and "dentistry".

RESULTS

Autologous platelet rich plasma is a safe and low cost procedure to deliver growth factors for bone and soft tissue healing.

CONCLUSION

The great heterogeneity of clinical outcomes can be explained by the different PRP products with qualitative and quantitative difference among substance.

Structural properties of fracture haematoma: current status and future clinical implications

Blood clots (haematomas) that form immediately following a bone fracture have been shown to be vital for the subsequent healing process. During the clotting process, a number of factors can influence the fibrin clot structure, such as fibrin polymerization, growth factor binding, cellular infiltration (including platelet retraction), protein concentrations and cytokines. The modulation of the fibrin clot structure within the fracture site has important clinical implications and could result in the development of multifunctional scaffolds that mimic the natural structure of a haematoma. Artificial haematoma structures such as these can be created from the patient's own blood and can therefore act as an ideal bone defect filling material for potential clinical application to accelerate bone regeneration. Copyright © 2016 John Wiley & Sons, Ltd.

A porcine model: surgical anatomy of the orbit for maxillofacial surgery

Due to its similarity to humans, the pig has proven to be a suitable biomodel for both research purposes and for training medical professionals, particularly in surgical specializations. For example, new implant materials have been tested on pig jaws and pigs have also been used in the development of new surgical techniques. For optimizing the effectiveness of such research or training, detailed data on the anatomy of their particular features are needed. At present, however, only limited information related to surgical and imaging anatomy of the facial and orbital areas of the pig and its comparison to human structures from the experimental surgery point of view is available in the literature. The aim of this study was to obtain such data and to compare the morphological structures of the porcine and human orbital regions and to lay down the foundation for practical use in experimental surgery. Ten pig heads were examined using computed tomography (CT) and magnetic resonance imaging (MRI) and, subsequently, a dissection of the orbit was carried out. Attention was focused on the structure of the orbit (floor, rim and nerves) frequently affected by pathological processes in humans (such as trauma, infection or tumours) and which consequently are frequently the subject of maxillofacial surgery. The porcine orbit is suitable for use in experimental medicine. However, if used in experiments, its anatomical peculiarities must be taken into consideration. Our study presents a foundation of basic knowledge for researchers who plan to use the pig as a biomedical model to investigate alternative treatments in the head region.

Platelet-rich preparations to improve healing. Part II: platelet activation and enrichment, leukocyte inclusion, and other selection criteria

Multiple platelet-rich preparations have been reported to improve wound and bone healing, such as platelet-rich plasma (PRP) and platelet rich fibrin (PRF). The different methods employed during their preparation are important, as they influence the quality of the product applied to a wound or surgical site. Besides the general protocol for preparing the platelet-rich product (discussed in Part 1 of this review), multiple choices need to be considered during its preparation. For example, activation of the platelets is required for the release and enmeshment of growth factors, but the method of activation may influence the resulting matrix, growth factor availability, and healing. Additionally, some methods enrich leukocytes as well as platelets, but others are designed to be leukocyte-poor. Leukocytes have many important roles in healing and their inclusion in PRP results in increased platelet concentrations. Platelet and growth factor enrichment reported for the different types of platelet-rich preparations are also compared. Generally, TGF-β1 and PDGF levels were higher in preparations that contain leukocytes compared to leukocyte-poor PRP. However, platelet concentration may be the most reliable criterion for comparing different preparations. These and other criteria are described to help guide dental and medical professionals, in large and small practices, in selecting the best procedures for their patients. The healing benefits of platelet-rich preparations along with the low risk and availability of simple preparation procedures should encourage more clinicians to incorporate platelet-rich products in their practice to accelerate healing, reduce adverse events, and improve patient outcomes.

A comparative study of the regenerative effect of sinus bone grafting with platelet-rich fibrin-mixed Bio-Oss® and commercial fibrin-mixed Bio-Oss®: an experimental study

Anorganic bovine bone (Bio-Oss®) particles are one of the most popular grafting materials. The particles are often mixed with platelet-rich fibrin (PRF) or a commercial fibrin (Tisseel®) to form a mouldable graft material. The objective of this study was to compare the potentials of PRF-mixed Bio-Oss® and Tisseel®-mixed Bio-Oss® to enhance bone regeneration in a canine sinus model. Six mongrel dogs were used in this study. After elevating the sinus membrane in both maxillary sinus cavities, an implant was placed into the sinus cavity. In one of the sinus cavities, the PRF/Bio-Oss® composite was grafted, and the Tisseel®/Bio-Oss® composite was grafted in the other sinus cavity. After a 6 month healing period, bone formation in the graft sites and bone-implant contact were evaluated. The mean osseointegration rate was 43.5 ± 12.4% and new bone formation rate 41.8 ± 5.9% in the PRF/Bio-Oss® composite sites. In the Tisseel®/Bio-Oss® composite sites they were 30.7 ± 7.9% and 31.3 ± 6.4%. There were statistically significant differences between the groups. The findings from this study suggest that when platelet-rich fibrin is used as an adjunct to Bio-Oss® particles for bone augmentation in the maxillary sinus, bone formation in the graft sites is significantly greater than when Tisseel® is used.

Impact of autogenous concentrated bone marrow aspirate on bone regeneration after sinus floor augmentation with a bovine bone substitute--a split-mouth pilot study

PURPOSE

Mesenchymal stem cells (MSC) with biomaterials have osteoinductive potential. The aim of this study was to evaluate early bone formation in xenogenic sinus grafts in a direct comparison with and without MSCs after 3 and 6 months. Literature on bone formation in pure xenogenic graft materials after 3 months in a human model is still lacking.

MATERIALS AND METHODS

In a split-mouth design, seven patients with a bilateral highly atrophic posterior maxilla were included. The test side was grafted with MSCs from concentrated bone marrow aspirate admixed to the bone graft material. On the control side, pure bovine bone material was applied. Biopsies were taken navigated after 3 and 6 months.

RESULTS

After 3 months, new bone formation in the control group was 11.8% (SD 6.2%) and in the test group 7.4% (SD 4.1%). After 6 months, the control group showed 13.9% (SD 8.5%) of new bone and the test group 13.5% NB (SD 5.4%). The fraction of bovine bone material after 3 months was 42.6% (SD 3.5%) in the test group and 34.9% (SD 11.8%) in the control group. After 6 months, the biomaterial content was comparable at both sides (test 36.2%, SD 7.8%; control 39.5%, SD 9.3%).

CONCLUSIONS

There was no significant difference in new bone formation between the test and control group with n = 7. The results may be dominated by the high mineral content of the biomaterial but could nevertheless be valuable for meta-analysis in the future.

Platelet-rich plasma gel promotes regeneration of articular cartilage in knees of sheeps

OBJECTIVE

To assess the regeneration of osteochondral defects in the joint cartilage of the knee induced by autologous platelet-rich plasma (PRP).

METHODS

Osteochondral defects produced in the trochlear groove of both knees of ten sheep; defects of the right knees were filled with autologous PRP and the left knees were left unfilled. Macroscopic and microscopic evaluation was carried out 12 week later. The results were evaluated by the total score of both macroscopic and microscopic evaluations comparing the two sides through the Wilcoxon paired test.

RESULTS

Macroscopic appearance was not uniform among animals, nor was it different between the right and left knees (p=0.3125), and in no case the regenerated tissue was equal to the normal surrounding cartilage. At histological examination, apparently normal cartilage was not detected in any knee, but a poorly differentiated cartilage was present in 7 right knees, compared to 3 left knees. Fibrocartilaginous tissue was present in most of the remaining knees, with a significant difference in the overall score between right and left knees (p=0.0313).

CONCLUSION

The PRP as used in this study has reparative properties of the joint cartilage of sheep knees, mostly by stimulating the formation of a fibrocartilaginous tissue. Laboratory investigation.

Long-term follow-up of severely resorbed mandibles reconstructed using tent pole technique without platelet-rich plasma

PURPOSE

To investigate the results of edentulous patients with severely resorbed mandibles who were treated with a modified tent pole procedure.

PATIENTS AND METHODS

Twenty-two edentulous patients (3 men, 19 women; mean age, 62 yr; range, 51 to 72 yr) with a history of conservative prosthodontic treatment failures were included this study. Using a transcutaneous submental approach, 4 endosseous dental implants were placed in the anterior mandible of each patient and covered with autogenous bone grafts harvested from the posterior iliac crest without the addition of platelet-rich plasma. Follow-up ranged from 3 to 9 years.

RESULTS

The postoperative course of the patients was uneventful, without any surgical infections. At 3 months postoperatively, the density of the grafted bone appeared to closely resemble that of the surrounding alveolar bone on panoramic radiographs. The average alveolar augmentation was 6.3 mm (standard deviation, 1.59 mm; range, 4 to 10 mm) and long-term follow-up showed no bone resorption around the endosseous implants.

CONCLUSIONS

The modified tent pole technique without the addition of platelet-rich plasma is a safe and effective method to reconstruct the severely resorbed mandible.

In vivo comparison of the bone regeneration capability of human bone marrow concentrates vs. platelet-rich plasma

BACKGROUND

Bone marrow aspirate concentrate (BMAC) including high densities of stem cells and progenitor cells may possess a stronger bone regenerative capability compared with Platelet-rich plasma (PRP), which contains enriched growth factors. The objective of this study was to evaluate the effects of human BMAC and PRP in combination with β-tricalcium phosphate (β-TCP) on promoting initial bone augmentation in an immunodeficient mouse model.

METHODOLOGY/PRINCIPAL FINDINGS

BMAC and PRP were concentrated with an automated blood separator from the bone marrow and peripheral blood aspirates. β-TCP particles were employed as a scaffold to carry cells. After cell counting and FACS characterization, three groups of nude mice (BMAC+TCP, PRP+TCP, and a TCP control) were implanted with graft materials for onlay placement on the cranium. Samples were harvested after 4 weeks, and serial sections were prepared. We observed the new bone on light microscopy and performed histomorphometric analysis. After centrifugation, the concentrations of nucleated cells and platelets in BMAC were increased by factors of 2.8 ± 0.8 and 5.3 ± 2.4, respectively, whereas leucocytes and platelets in PRP were increased by factors of 4.1 ± 1.8 and 4.4 ± 1.9, respectively. The concentrations of CD34-, CD271-, CD90-, CD105-, and CD146-positive cells were markedly increased in both BMAC and PRP. The percentage of new bone in the BMAC group (7.6 ± 3.9%) and the PRP group (7.2 ± 3.8%) were significantly higher than that of TCP group (2.7 ± 1.4%). Significantly more bone cells in the new bone occurred in sites transplanted with BMAC (552 ± 257) and PRP (491 ± 211) compared to TCP alone (187 ± 94). But the difference between the treatment groups was not significant.

CONCLUSIONS/SIGNIFICANCE

Both human BMACs and PRP may provide therapeutic benefits in bone tissue engineering applications. These fractions possess a similar ability to enhance early-phase bone regeneration.

Maxillary sinus floor augmentation with injectable calcium phosphate cements: a pre-clinical study in sheep

OBJECTIVES

The aim of this pre-clinical study was to evaluate the biological performance of two injectable calcium phosphate cement (CPC) composite materials containing poly(D,L-lactic-co-glycolic)acid (PLGA) microspheres with different properties in a maxillary sinus floor elevation model in sheep.

MATERIALS AND METHODS

PLGA microspheres were made of either low molecular weight (~17 kDa) acid-terminated PLGA (PLGA(L-AT) ) or high molecular weight (~44 kDa) end-capped PLGA (PLGA(H-EC) ) and incorporated in CPC. Eight female Swifter sheep underwent a bilateral maxillary sinus floor elevation procedure via an extra-oral approach. All animals received both materials, alternately injected in the left and right sinus (split-mouth model) and a time point of 12 weeks was used. Analysis of biological performance was based on histology, histomorphometry, and evaluation of sequential fluorochrome labeling.

RESULTS

Both types of CPC-PLGA composites showed biocompatibility and direct bone-cement contact. CPC-PLGA(L-AT) showed a significantly higher degradation distance compared to CPC-PLGA(H-EC) (1949 ± 1295 μm vs. 459 ± 267 μm; P = 0.0107). Further, CPC-PLGA(L-AT) showed significantly more bone in the region of interest (26.4 ± 10.5% vs. 8.6 ± 3.9% for PLGA(H-EC) ; P = 0.0009) and significantly less remaining CPC material (61.2 ± 17.7% vs. 81.9 ± 10.9% for PLGA(H-EC) ; P = 0.0192).

CONCLUSIONS

Both CPC-PLGA(L-AT) and CPC-PLGA(H-EC) demonstrated to be safe materials for sinus floor elevation procedures in a large animal model, presenting biocompatibility and direct bone contact. In view of material performance, CPC-PLGA(L-AT) showed significantly faster degradation and a significantly higher amount of newly formed bone compared to CPC-PLGA(H-EC) .

Comparative radiographic evaluation of alveolar bone healing associated with autologous platelet-rich plasma after impacted mandibular third molar surgery

PURPOSE

This study radiographically evaluated the performance of autologous platelet-rich plasma (PRP) applied in tooth sockets.

PATIENTS AND METHODS

Thirty extractions of bilateral impacted mandibular third molars were performed in 15 volunteers (7 men, 8 women; 18 to 22 years old). After extraction of right and left mandibular third molars, the socket at 1 side received the autologous PRP (PRP group) and the other was filled with blood clot (control group). Millimeter periapical radiographs were obtained 7 days, 1 month, and 2, 3, and 6 months postoperatively. Radiographic bone density was quantified 3 times by the same examiner at different moments using HLImage 97 software, and data were statistically analyzed by Statgraf 7.0 software (analysis of variance and Tukey test).

RESULTS

In general, there was significantly faster bone formation in sockets treated with PRP (P < .01). Significant bone formation was observed in the first month (P < .01), second month (P < .05), and third month (P < .01) for the PRP group. No statistical differences were observed on the seventh day and sixth month of investigation, yet there were higher means of radiographic bone density in sockets treated with PRP. In the control group, men exhibited significant bone repair compared with women (P < .05).

CONCLUSION

Autologous PRP was found to accelerate alveolar bone regeneration, and men presented better repair after tooth extraction.

An animal model for sinus floor elevation with great elevation heights. Macroscopic, microscopic, radiological and micro-CT analysis: ex vivo

OBJECTIVES

Different animal models are used for research and training concerning sinus floor elevation. However, there is little information regarding an animal model for elevation heights of approximately 10 mm. The aim of this study was to explore the anatomical aspects of the maxillary sinus of adult pigs and to investigate the suitability of this animal as a model for sinus floor elevation training and research with great elevation heights.

MATERIAL AND METHODS

Thirty-four bisected heads of adult domestic pigs were examined 6 h postmortem. Direct sinus floor elevation was performed with an elevation height of 10 mm. Localization, diameters, volume and septa of the maxillary sinus were recorded on lateral X-rays and macroscopically. The thickness and structure of the maxillary sinus were investigated microscopically. The osseous microstructure of the lateral sinus wall was assessed microscopically and via micro-CT.

RESULTS

The maxillary sinus of the adult pig exhibits an average length of 51±6.2 mm, a height of 31±4.1 mm, a width of 19±1.6 mm and a volume of 31±7.6 cm(3) . At least one septum could be observed on the floor of each sinus. The mucosal thickness amounted to a mean of 1692±138 μm, and the lateral bony wall of the sinus to a mean of 3±0.3 mm. A laceration of the Schneiderian membrane occurred in 25% during the elevation process.

CONCLUSION

The maxillary sinus of adult domestic pigs is a suitable model for sinus floor elevation training and research with greater elevation heights of up to 10 mm.

Effects of a highly concentrated platelet-rich plasma on the bone repair using non-critical defects in the calvaria of rabbits

PURPOSE

To verify the effect of highly concentrated platelet-rich plasma (hPRP) in the pathways of bone repair using non-critical defects in the calvaria of rabbits.

METHODS

The hPRP was produced from collected venous blood of 21 rabbits. Four non-critical defects of 8 mm in diameter were created on the calvaria of each animal. The defects were all treated differently: autogenous particled bone (APB, group 1), autogenous particled bone associated with hPRP (APB + hPRP, group 2), isolated hPRP (group 3), and blood clot (control, group 4). Animals were submitted to euthanasia on the 2nd, 4th and 6th week postoperatively. Histological and histomorphometric analysis were carried through.

RESULTS

After two weeks, groups 1 and 2 were in more advanced stage of repair than 3 and 4. At this period, comparing the groups 1 and 2, no significant differences were found between both, which also happened between the groups 3 and 4. However, after four and six weeks, the group 1 showed a more advanced stage of repair among all the other studied groups, while group 2 was in more advanced signs of bone repair than groups 3 and 4. Comparing groups 3 and 4, after four and six weeks, the least advanced stage of bone repair was found to be within group 3.

CONCLUSION

The use of a highly concentrated PRP was considered prejudicial to the repair of non-critical defects in the calvaria of rabbits, either in the association of autogenous particled bone, when compared to autogenous particled bone alone, or in its isolated form, when compared to blood clot (control).

Evaluation of the bone healing process utilizing platelet-rich plasma activated by thrombin and calcium chloride: a histologic study in rabbit calvaria

To evaluate the bone healing of defects filled with particulate bone graft in combination with platelet-rich plasma (PRP), added with a mixture of calcium chloride and thrombin or just calcium chloride. Two 5-mm bone defects were created in the calvaria of 24 rabbits. Each defect was filled with particulate bone graft and PRP. In one defect the PRP was activated by a mixture of calcium chloride and thrombin; in the other, PRP was activated by calcium chloride only. The animals were euthanized 1, 2, 4, and 8 weeks after the surgeries, and the calvaria was submitted to histologic processing for histomorphometric analysis. The qualitative analysis has shown that both defects presented the same histologic characteristics so that a better organized, more mature, and well-vascularized bone tissue was noticed in the eighth week. A good bone repair was achieved using either the mixture of calcium chloride and thrombin or the calcium chloride alone as a restarting agent of the coagulation process.

Platelet-rich plasma in sinus augmentation procedures: a systematic literature review: Part II

BACKGROUND

Although platelet-rich plasma (PRP) has been extensively studied for over a decade, there are no definitive reports, which prove the benefit of using PRP in sinus augmentation procedures. In addition, no systematic literature review has been done to report the benefit of treatment outcome in patients who received PRP in conjunction with bone/bone substitutes in maxillary sinus augmentation procedures. Therefore, it can be rightly stated that evidence for an adjunctive benefit of using PRP with bone grafts in sinus augmentation procedures is equivocal and inconclusive.

AIM

: The objective of this systematic literature review was to examine this literature in determining whether PRP with bone and bone substitutes leads to more rapid and effective bone regeneration clinically, radiographically, and histologically with sinus augmentation procedures and was there any clinical data parallel to animal experiments providing clinical evidence in sinus augmentation procedures?

METHODS

A systematic review of randomized clinical trials of at least 6 months duration was conducted comparing PRP and bone/bone substitutes (test group) to bone/bone substitutes (control group) alone. Electronic databases such as MEDLINE and CENTRAL (Cochrane central register of controlled clinical trials) were searched for relevant articles. The reference list of all included articles was searched along with unpublished clinical trials whose abstracts were available.

RESULTS

Although, there is a lack of human studies, which show benefit of using PRP in conjunction with bone grafting materials, it can be stated that use of PRP does lead to early regeneration and reduction in healing time of soft and hard tissues. However, no significant statistical or clinical benefit was reported from studies that would satisfy the inclusion criteria. This study answers the question very clearly that at this point of time, there is no human study that strongly supports the benefit of using PRP in sinus augmentation procedures.

CONCLUSION

There is a paucity of clinically controlled trials regarding benefits of PRP in sinus augmentation procedures. Theoretically, it seems to have significant beneficial effects on the soft and hard tissue healing; however, the disparity in study design, surgical techniques, and different outcome assessment variables used, makes it difficult to assess the practical benefit of its clinical use. Although no obvious positive effects of PRP on healing of bone graft material in maxillary sinus augmentation procedures were noted, the handling of the particulate bone grafts was improved.

Platelet-rich plasma diminishes calvarial bone repair associated with alterations in collagen matrix composition and elevated CD34+ cell prevalence

The interaction between platelets and both type I and III collagens plays an important role in modulating platelet adhesion and aggregation, also contributing to the chemotaxis of CD34+ cells. The interaction with type III collagen can maintain high levels of collagen and alter the biology of bone repair when the PRP is used. The aim of this study was to evaluate the effect of platelet-rich plasma (PRP) and autograft on the presence of type III and type I collagens, the ratio between them, as well as the presence of CD34+ progenitor cells, while comparing these results by means of a histomorphometric analysis of the bone tissue. Four bone defects (8.0mm in diameter and 2.0mm in depth) were produced on the calvarium of 23 rabbits. The surgical defects were treated with either autogenous bone grafts, autogenous bone grafts with PRP and PRP alone. Animals were euthanized at 2, 4 or 6 weeks post-surgery. Histological, histomorphometric and immunohistochemical analyses were performed to assess repair time, as well as the expression of type I and III collagens, and number of progenitor CD34+ cells. Data were analyzed using the ANOVA and Student-Newman-Keuls test (alpha=5%). An enlarged granulation and medullary tissue areas in the PRP groups were observed. The use of PRP in this study hindered bone deposition, also enhanced type III to type I collagen ratio and the chemotaxis of CD34+ progenitor cells, similarly to a thrombogenic effect.

Effects of platelet-rich plasma on healing of alveolar socket: split-mouth histological and histometric evaluation in Cebus apella monkeys

CONTEXT

The prediction of implant treatment is directly influenced by the quality of the remaining bone after tooth extraction.

AIMS

The purpose of this experimental study was to, histologically and histometrically, evaluate the bone repair process in the central areas of extraction sockets filled with platelet-rich plasma.

MATERIALS AND METHODS

Four young adult male Cebus apella monkeys were used. The extraction of both right and left inferior second premolars was accomplished. After extraction, in one of the extraction sockets, coagulum was maintained while in the other it was removed; the alveolus was dried with gauze compress and filled up with platelet concentrate. For PRP production, Sonnleitner's protocol was followed. The specimens for histological and histometric assessment were obtained in 30, 90, 120 and 180 days intervals.

RESULTS

In 30 days new bone formation was intense in both experimental and control sockets and no significant differences were observed between the two groups. After 90 days of the extraction, while the control group showed signs of decrease in osteogenesis, in the experimental unit, the process of bone formation and fibroblast-like cell proliferation remained intense. After 120 days, the PRP treated socket was occupied by large trabeculae of bone. After 180 days, the control unit was occupied mostly with bone marrow. The experimental unit remained occupied with large amounts of bone tissue.

CONCLUSIONS

It was possible to conclude that bone repair was enhanced by the use of platelet- rich plasma in alveolar sockets.

Influence of the ratio of particulate autogenous bone graft/platelet-rich plasma on bone healing in critical-size defects: a histologic and histometric study in rat calvaria

The purpose of this study was to analyze histomorphometrically the influence of the ratio of particulate autogenous bone (AB) graft/platelet-rich plasma (PRP) on bone healing in surgically created critical-size defects (CSD) in rat calvaria. Fifty rats were divided into five groups: Group C (control), Group AB, Group AB/PRP-50, Group AB/PRP-100, and Group AB/PRP-150. A 5-mm diameter critical-size defect was created in the calvarium of each animal. In Group C, the defect was filled by blood clot only. In Group AB, the defect was filled with 0.01 mL of AB graft. In Groups AB/PRP-50, AB/PRP-100, and AB/PRP-150, the defects were filled with 0.01 mL of AB graft combined with 50, 100, and 150 microL of PRP, respectively. All animals were euthanized at 30 days postoperative. Histomorphometry, using image analysis software, and histology analyses were performed. New Bone Area (NBA) and the remaining bone graft particles area (RPA) were calculated as a percentage of the total area of the original defect. Percentage data were transformed into arccosine for analysis. No defect completely regenerated with bone. Group AB/PRP-50 (41.78 +/- 13.48%) had a significantly greater NBA than Groups C (19.29 +/- 5.11%), AB (27.43 +/- 10.90%) or AB/PRP-150 (19.17 +/- 8.45%) (p < 0.05). No significant differences were observed between groups AB/PRP-50 and AB/PRP-100 or among groups AB, AB/PRP-100, and AB/PRP-150 with regard to NBA (p > 0.05). Group AB/PRP-150 (31.59 +/- 3.22%) had a significantly greater RPA than Groups AB (19.09 +/- 5.21%), AB/PRP-50 (17.33 +/- 4.43%), and AB/PRP-100 (19.72 +/- 3.62%) (p < 0.001). No significant differences were observed among groups AB, AB/PRP-50, and AB/PRP-100 with regard to RPA (p > 0.05). The ratio AB graft/PRP influences bone healing in surgically created CSD in rat calvaria.

Sinus grafting with a natural fluorohydroxyapatite for immediate load: a study with histologic analysis and histomorphometry

The goal of this retrospective study was to evaluate the survival rates of dental implants placed in sinuses grafted with a 50:50 composite ratio of autogenous bone and a natural flourohydroxyapatite (FHA) combined with platelet-rich plasma (PRP) using an immediate-load protocol. The authors hypothesized that a 50:50 composite ratio of FHA and autogenous bone combined with PRP would permit immediate loading without compromising implant survival rates. Eleven patients with bilateral partial edentulism of the posterior maxilla were enrolled in this retrospective study. Autogenous bone used in the graft procedure was harvested from the tibia of the left lower extremity. Each patient was grafted with a 50:50 composite ratio of autogenous bone and FHA. Membranes were not used to cover the lateral wall osteotomy site. Platelet-rich plasma was added to the graft material to accelerate and enhance bone regeneration. Four to 6 months after the grafting procedure, 37 hydroxyapatite-coated dental implants were surgically placed and immediately loaded between 72 hours and 5 days later with custom titanium abutments and acrylic provisional restorations placed out of functional occlusion. Six months later, definitive ceramometal restorations were cemented on to the custom abutments. Patients were observed over a 52-week period. The overall implant survival rate was 97.3%. Histologic and histomorphometric analysis of core samples revealed formation of new vital bone in different graft specimens ranging from 23% to 34%. In each core bone sample, 100% of the bone sample was determined to be vital. In the grafted maxillary sinus, the natural FHA combined with autogenous bone in a 50:50 composite ratio with PRP is a suitable graft material permitting immediate load without compromising implant survival rates while decreasing the overall healing time.

The adjunctive use of platelet-rich plasma in the therapy of periodontal intraosseous defects: a systematic review

BACKGROUND AND OBJECTIVE

The evidence for the efficacy of the adjunctive use of platelet-rich plasma (PRP) in periodontal intraosseous defects has not been systematically evaluated. The objective of this review was to address the focused question, 'What is the efficacy, with respect to clinical, radiographical and patient-centred outcomes, of combinations of PRP with other therapeutic bioactive agents/procedures, compared with the efficacy of the same agents/procedures without the adjunctive use of PRP in the therapy of periodontal intraosseous defects in patients with chronic periodontitis and without systemic diseases that could potentially influence the outcome of periodontal therapy?' by performing a systematic review of randomized controlled clinical trials (RCTs) published in the dental literature in any language, up to and including September 2008.

MATERIAL AND METHODS

Data sources principally included electronic databases, manually searched journals and contact with experts. In the first phase of study selection, the titles and abstracts, and in the second phase, full papers were screened independently and in duplicate by two reviewers.

RESULTS

In the first phase, 6124 potentially relevant titles and abstracts were examined. In the second phase, the full text of 20 publications was thoroughly evaluated. Eventually, 10 RCTs were selected.

CONCLUSION

Diverse outcomes (positive and negative) have been reported for the efficacy of PRP combined with various therapeutic bioactive agents/procedures, reflecting the limited and heterogeneous data available and possibly suggesting that the specific selection of agents/procedures combined with PRP could be important. Additional research on the efficacy of each specific combination of PRP is necessary.

Platelet-rich plasma: a literature review

Platelet-rich plasma (PRP) is an autologous concentration of platelets in concentrated plasma, which is extensively used to promote soft and hard tissue healing. The significance behind its use refers to the abundance of growth factors present in a well-prepared PRP concentrate. These growth factors enhance the rate and quality of wound healing by different mechanisms. The objective of this review article is to explain the biological aspect of hard and soft tissue healing by application of PRP in conjunctions with its molecular basis.

Influence of the proportion of particulate autogenous bone graft/platelet-rich plasma on bone healing in critical-size defects: an immunohistochemical analysis in rat calvaria

This immunohistochemical analysis evaluated the influence of the proportion of particulate autogenous bone (AB) graft/platelet-rich plasma (PRP) on bone healing in surgically created critical-size defects (CSD) in rat calvaria. 25 rats were divided into 5 groups: C (control), AB, AB/PRP-50, AB/PRP-100 and AB/PRP-150. A 5 mm diameter critical-size defect was created in the calvarium of each animal. In Group C, defect was filled by blood clot only. In Group AB, defect was filled with AB graft. In Groups AB/PRP-50, AB/PRP-100 and AB/PRP-150, defects were filled with AB graft combined with 50, 100 and 150 microl of PRP, respectively. Animals were euthanized at 30 days post-operative. Osteocalcin (OC) and osteopontin (OP) immunohistochemical staining were performed. OP-positive and OC-positive cells were quantified. The amount of vital bone (VBA) and remaining bone graft particles (RPA) were calculated as percentage of the total area of the original defect. Data were statistically analyzed (ANOVA, Tukey, p<0.05). Group AB/PRP-100 presented a significantly higher number of OP-positive cells than groups C, AB/PRP-50 and AB/PRP-150 (p<0.05) and also a significantly higher number of OC-positive cells than all of the other groups (p<0.05). The number of OP-positive cells in Group AB/PRP-150 was significantly lower than in Group AB (p<0.05). Statistically significant differences were not found between groups with regard to either VBA or RPA (p>0.05). However, clear trends were indicated by an increase in VBA in Group AB/PRP-100 when compared to groups C, AB and AB/PRP-150 and an increase in RPA in Group AB/PRP-150 when compared to groups AB, AB/PRP-50 and AB/PRP-100. The proportion AB graft/PRP seems to influence bone healing in CSD in rat calvaria. The highest expression of osteocalcin and osteopontin, and thus the most developed healing, was found in Group AB/PRP-100 indicating that there may be an optimal proportion beyond which increasing the concentration PRP is deleterious.

The use of platelet-rich plasma in bone reconstruction therapy

The use of platelet-rich plasma (PRP) in bone reconstruction therapy was introduced in the late 1990s. Since then, many scientists and clinicians have employed it in orthopaedic and oral surgeries. Unfortunately, studies that analyze the use of PRP are somewhat controversial as some conclude that the use of PRP may favor bone regeneration and others conclude that the use of PRP is irrelevant. By listing and analyzing the biological effect that each factor released by the activated platelets can have in bone regeneration, the present review answers the question of why PRP may be useful in bone reconstruction therapy. Subsequently, by examining the studies that have both successfully and unsuccessfully utilized PRP, it suggests how PRP might be used in order to achieve successful results in orthopaedic and dental bone reconstruction surgeries.

Effect of platelet-rich plasma on sinus lifting: a randomized-controlled clinical trial

OBJECTIVE

The combination of anorganic bovine bone (ABB) with platelet-rich plasma (PRP) has been widely used in bone regeneration procedures although its benefits are still unclear. The purpose of this study was to evaluate whether or not PRP improves the efficacy of ABB in sinus floor augmentation. In addition, we have investigated the effect of residual bone height and tobacco on implant survival in sinus augmentation procedures.

PATIENT AND METHODS

Eighty-seven patients recruited for this study underwent 144 sinus floor augmentation procedures using ABB alone or ABB plus PRP (ABB+PRP) in a randomized clinical trial. A total of 286 implants were placed in the augmented bone, and their evolution was followed up for a period of 24 months. In order to investigate on a histological level and any adjunctive effects, we performed an ancillary study in five edentulous patients with a symmetrical severely resorbed maxilla. In these patients, a bilateral sinus augmentation was randomly performed using ABB or ABB+PRP in a split-mouth design, and after 6 months, bone biopsies were taken from the implant sites for histological and histomorphometric analysis.

RESULTS

Overall, 96.2% of ABB and 98.6% of ABB+PRP implant success were obtained during the monitoring period and differences were not found between sites grafted with and without PRP in the 87 patients studied. Densitometry assessments and graft resorption were similar in both experimental groups. However, the histological and histomorphometrical analysis in the five edentulous patients revealed that bone augmentation was significantly higher in sites treated with ABB+PRP (p <or= 0.05). Another outcome from our study is that the lack of initial bone support (p <or= 0.05) and smoking (p=0.05) appeared to have a negative effect on the treatment success, which was accentuated when both circumstances coincided.

CONCLUSIONS

PRP is not a determining factor for implant survival in sinus lifting procedures. However, this study revealed that PRP can improve the osteoconductive properties of ABB by increasing the volume of new bone formed. Moreover, in sinus augmentation procedures the implant's survival rate appears to be more influenced by the residual bone height or by tobacco than by the type of bone graft.