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At the European Dental Center.

Densitometric examination (determination of bone density) of regenerated bone.

The development of treatment methods to accelerate the regeneration of soft tissues and alveolar bone is vital for delayed protocols, for short, medium or long term, in order to reduce the waiting time for the patient and improve the quality of the regenerated tissue. Filling the PRGF®-ENDORET® post-extraction well with its subsequent compaction with autogenous fibrin allows us to obtain a sufficient quantity (density indices of more than 500 Hounsfield units) and quality (bone I, II and III type) of the alveolar bone to ensure the primary stability of the implants, both in the internal and external walls of the alveoli, for a time period of 4 to 8 weeks. Treatment of wells after removal using PRGF®-ENDORET® and autologous fibrin is a simple, economical and predictable bio-technological process for the regeneration of the alveolar bone and keratinized gums, which can significantly reduce the patient's waiting time without any side effects, as shown by long-term an experience.



Over the past decade, the field of dentistry has undergone significant progress thanks to a more thorough knowledge of dental pathologies and the development of new biological techniques and protocols. One has only to look back for a moment to understand that the protocols that were once undeniable — such as the implantology treatment according to Branemarck — are completely replaced today. This standard original procedure implied: before installing the implant, the healing period is 12 months from the moment the tooth was removed, after which it was necessary to wait from 3 to 6 months before the next surgery. Today we use other criteria to determine the time frame between removal (exodontics) and implantation. In accordance with the current classification, immediate implant placement is distinguished, as well as delayed — for short, medium and long term — depending on whether the implant is installed immediately after removal or after 6-8 weeks, 3-4 months or 9 months, respectively.
Undoubtedly, immediate installation offers many functional and aesthetic benefits for the patient, in addition to significantly reducing treatment time. However, under certain circumstances, to ensure the functional and aesthetic success of implantation, complete regeneration of the post-extraction hole and keratinized gums is necessary. Certain situations, such as extensive periapical lesions, three-wall defects, large craters around the teeth, or gum recession, may be contraindications for immediate implant placement. In these cases, a longer time is needed for the healing and regeneration of the alveoli. On the other hand, delaying treatment after tooth loss increases the risk of developing the process of resorption of the alveoli and loss of bone height and thickness of the alveolar bone, which in some cases can make the installation of implants more difficult or even impossible. It is necessary to create a protocol that will accelerate the process of regeneration of soft tissues and alveolar bone to obtain the ideal quantity and quality of keratinized tissues and bone for implantation, at the same time, reducing the waiting time for the patient.
Filling post-extraction alveoli with a preparation enriched with growth factors (PRGF®-ENDORET®) (1) is a biotechnological alternative to accelerate regeneration of the alveolar bone.
PRGF®-ENDORET® consists of a small volume of a highly specific platelet-rich plasma preparation, quickly obtained and prepared in a simple way from the patient’s own blood, the activation of which leads to the formation of a three-dimensional biocompatible fibrin matrix. As a result, a number of proteins and growth factors are released that help accelerate bone healing and bone regeneration.
PRGF®-Endoret® is a 100% autogenous and biocompatible product. Today, it is considered more accurate to talk about PRGF®-Endoret® technology, since it does not mean a single product, but a series of several therapeutic compounds that can be obtained in a simple way from the patient’s own blood using a single preparation protocol:
Supernatant PRGF®-Endoret®: An excellent nutrient medium for stem cells and autologous bone. It contains growth factors and plasma proteins obtained by retraction of a clot of PRGF®-Endoret® (Fig. 1).
PRGF®-Endoret® Activated Fluid: Activation of PRGF®-Endoret® with the PRGF®-Endoret® Activator (Calcium Chloride) promotes the release of protein content and platelet-derived growth factors, which saturates the liquid composition with signals that can create a bioactive surface on dental implants for acceleration of osseointegration. It can also be used to infiltrate muscles, ligaments, skin, joints, wounds, etc. (Fig. 2).
Clot PRGF®-Endoret®: after 3-5 minutes, the activated liquid PRGF®-Endoret® turns into a three-dimensional fibrin matrix saturated with growth factors, which can be used in a variety of procedures, from regeneration of the well after removal to treatment of musculoskeletal and vascular pathologies ( Fig. 3).
Autogenic fibrin: retraction of a clot obtained from PRGF®-Endoret® fraction 1 allows to obtain a dense, flexible, fully biocompatible fibrin, which can be used in many cases as an insulating membrane (Fig. 4).
    So, this article describes the technique used in 11 patients with an average age of more than 50 years. This group of patients was selected to observe the effects of PRGF®-Endoret® and autologous fibrin. The purpose of this study is to confirm the effectiveness of growth factors in combination with the fibrin matrix, along with a decrease in the waiting time required for adequate healing and bone regeneration. It also evaluates the potential of autologous fibrin as a biocompatible material for optimal filling of the alveoli. To do this, using cone beam computed tomography, the density and quality of the alveolar bone were determined in the period from 8 to 13 weeks after removal and subsequent evaluation of these data using the BTI Scan® II software (3).

Fig. 01: PRGF-Endoret supernatant enriched with growth factors
Fig. 02: PRGF-Endoret fluid «provides bioactivation of the surface of dental implants to improve their osseointegration.


Fig. 03: PPGF-Endorel clot is a three-dimensional matrix of fibrin and other components, impregnated with growth factors.
Fig. 04: The elastic properties of autologous fibrin.

Only 11 patients (4 men and 7 women) aged 45 to 71 years (average age 53.8 years) were appropriately informed and made up the experimental group. PRGF®-ENDORET® was prepared from a small volume of blood (20 cm3), taken from a peripheral vein using sodium citrate as an anticoagulant (citrate tubes of the PRGF® System) (Fig. 5-10). The tubes are then centrifuged to separate the plasma from the red blood cells (Centrifuge system BTI IV). The plasma layer is separated according to the PRGF®-Endoret® protocol:

Fig. 05: PRGF-ENDORET System Equipment.
Fig. 06: Citric PRGF tubes for blood sampling.


Fig. 07: After centrifugation, plasma and blood of various colors can be observed. BTI PRGF-ENDORET tubes have a calibration scale to see the volume of the obtained plasma, as it will vary depending on the hematocrit of the patient.
Fig. 08: Different fractions in a 9 ml tube after centrifugation.


Fig. 09: Plasma Transfer Device (PTD).
Fig. 10: PTD in position to separate fractions.

Fraction 1: This is the upper part of the total amount of plasma obtained after centrifugation. This fraction has the same platelet concentration as in circulating blood. Its volume is calculated by subtracting 2 ml of the plasma layer above the white blood cell film.
Fraction 2: This is a 2 ml plasma layer above the white blood cell film. It contains 2.5 times more platelets than in circulating blood. When selecting this fraction, it is extremely important not to mix it with white blood cells that cause tissue inflammation.
Once the two fractions are separated, each can be used in different situations. The upper fraction (fraction 1) will be used as an autogenous fibrin membrane to densify the near-side part of the alveoli, providing support for bone and soft tissue growth.
Activation is performed, which causes the formation of a clot or membrane as soon as we get the necessary plasma fractions. To do this, we add 50 μl (0.05 cm3) of PRGF®-Endoret® activator per 1 cm3 of plasma. The amount of activator is measured by an insulin syringe calibrated per μl, and then added to the plasma. A clot forms in 5 to 8 minutes. This time will vary inversely with the platelet count.
Thus, the more platelets there are, the less time aggregation will take.
These data are important due to the individual characteristics of the platelet count in the blood, physiological norms of which range from 150,000 to 400,000. If the activated plasma is maintained at body temperature (37 ° C), time is reduced and clot formation will be more controlled.
The procedure aimed at regenerating the alveoli with PRGF®-Endoret® is performed in one surgical procedure with removal. For this, the coagulated clot PRGF®-ENDORET®, obtained from fraction 2, is placed in the alveoli, and then it is densified with a retracted fibrin membrane, which has excellent elastic and homeostatic properties.
In addition to the barrier effect, leaving room for fibrin compaction, it will become a fully reabsorbed osteoconductive material within 3–4 months (Fig. 11–13).
Fig. 11: A newly formed fibrin clot 8 minutes after activation.
Fig. 12: A fibrin membrane was obtained 45 minutes after activation as soon as clot retraction occurred.
Fig. 13: Complete retraction of fibrin 1 hour after activation. 6 of this consistency, it may even be sutured.
To accurately monitor the process of bone regeneration, patients underwent a CBCT study from 8 to 13 weeks after removal. Thanks to the BTI Scan® II image processing and analysis program, it has become possible to determine bone density and correlate it with the classification of the bone quality of Lekholm and Zarb. To obtain these data, bone density indices were determined at three different points in the regenerated well and in several places every 0.5 mm, both in the inner (1 mm in) and on the outside (1 mm out) of its perimeter, which subsequently will be future implant bed. Thus, it became possible to determine the degree of bone regeneration not only inside the alveoli, but, more importantly, the density and quality of the bone of the alveolar walls where the implant will be installed, and on which its primary stability directly depends.


Once PRGF®-ENDORET® is activated, the process of release of growth factors (FR) begins. These RFs will play a major role in revascularization and bone regeneration, exerting a mitogenic and proliferative effect on endothelial and osteoprogenic cells. In order to characterize the composition of the growth factors PRGF®-ENDORET® (RF), we measured the amount of major RF released from platelets, namely, TGF (platelet), ß-TGF (ß-transforming), IGF-1 (insulin-like), EGF (epidermal), VEGF (vascular endothelium), and VEGF (hepatocytes) (Fig. 14 and 15).
Fig. 14 and 15: Concentrations of the main growth factors contained in PRGF-ENDORET. Significant concentrations of IGF-1, B-TGF and TGF should be noted.
Advantageously, the first 3 factors are most widely represented in PRGF®-ENDORET®, and their effects on healing and bone regeneration are described in detail in the literature.
For example, TGF is known for its ability to increase the proliferation of osteoblasts in vitro, while ß-TGF at a certain dose enhances the synthesis of proteins of collagen derivatives, such as type I and V collagen, in addition to augmentation of matrix mineralization and improvement of implant engraftment. Finally, IGF-1 stimulates bone formation by inducing cell proliferation, differentiation and biosynthesis of type I collagen. Its mitogenic function in multinuclear osteoclastic cells is also known. But it is more important to note that, according to various studies, a combination of these RFs induces a synergistic effect on bone regeneration. Moreover, activation of PRGF®-ENDORET® involves the release of a large number of proteins and growth factors, which play a key role in proper bone regeneration. In this regard, it is necessary to emphasize the angiogenic effects of the VEGF, as it will be vital for the appropriate provision of regenerated tissues with oxygen and nutrients. Immediately after preparation of PRGF®-ENDORET®, an operation is performed to remove and fill the post-extraction well PRGF®-ENDORET®, as well as its compaction with autogenous fibrin, as illustrated in Fig. 16-20.
One aspect should be noted that the amount of PRGF®-ENDORET® used will vary depending on the size of the alveoli to adequately fill the resulting defect. After 2 to 3 months after filling and compaction of the alveoli, patients underwent CT; data were analyzed using BTI Scan® II software. As mentioned earlier, this program is an excellent diagnostic tool for evaluating bone quality and quantity, which helps ensure predictability of implantation.
In fact, these two variables seem to have a decisive influence on the success or failure of implantation, regardless of where the implants are placed. The failure rate is higher when the amount of bone is insufficient or its quality is low, which will directly affect primary stability.
Fig. 16: (a) Schematic representation of a post-extraction alveoli. (b) Filling the alveoli with a clot of PRGF'-ENDORET * and an autogenous fibrin membrane obtained using the same technique, © Regeneration of keratinized tissues and post-extraction alveoli after 12 weeks.

Fig. 17: The removal, curettage of the hole and its filling, as described previously. In this case, suturing, in addition to the fibrin’s own adhesive properties, stabilizes and retains the fibrin membrane.
Fig. 16: View of the disposal site after 24 hours.


Fig. 19: Epithelization of the fibrin membrane after 15 days. The time of epigelization can vary between 5 and 15 days depending on the size of the alveoli and on the patient.
Fig. 20: Epithelial regeneration is observed after 3 months.

For example, a bone of type IV, considered as a bone of low quality, is characterized by a matrix of soft trabecular bone of low density, compared with type II and III, the quality of which will provide a much higher level of primary stability of the implant.
The BTI Scan® II program allows you to correlate bone density with the bone quality classification proposed by Lekholm and Zarb. Nevertheless, we propose a new classification, more accurate, which represents 5 classes in accordance with the average density indicators measured in units. Hounsfield, to determine the type of bone (Fig. 21 — 25). Over the past few years, our research team has made considerable efforts to thoroughly research and describe PRGF®-ENDORET® and all its possible therapeutic applications (4-6). In this study, we were able to verify the enormous potential of PRGF®-ENDORET® as a means for the regeneration of the alveolar bone of patients older than 50 years who have reduced osteogenic activity (8).

Tab. 1: The ratio of bone density to bone type and areas in which they are most often present.
Fig. 21: Type I bone (10S0 — 1400 Howsfield units). It is important to evaluate the density, both in the middle and on the outer perimeter of the future implant bed.

Fig. 22: Type II bone (850 — 1 LLC Hounsfield units).
Fig. 23: Type III bone (550 — 800 Hounsfield units).


Fig. 24: Type IV bone (400 — 500 od. Hounsfield).
Fig. 25: Cos V type (100 — 350 Hounsfield units).

It should be noted that even 2-3 months after removal (to be precise, from 8 to 13 weeks), data analysis using the BTI Scan® II program showed high density and sufficient bone quality in the wells filled and compacted with PRGF®- ENDORET® and autologous fibrin (Fig. 26 — 28). Namely, we got an average density of 534 units. Hounsfield in the center of the alveoli — a site where 12 weeks before that there was no bone at all and the density, respectively, was zero. But undoubtedly, the most remarkable is obtaining high bone density, both in the middle and on the outer perimeter of the future site for implantation, which reach levels above 600 units. Hounsfield, which guarantees good primary stability.
Fig. 26: Diagram of three measurements taken in a well to assess the quality of regeneration.

Fig. 27: Density indices within the alveoli obtained from an average of 3 measurements at 3 different points in the center of the alveoli.
Fig. 28: Density measurement was carried out for every 0.5 mm, both 1 mm inward and 1 mm outward from the hypothetical position of the future implant. This graph reflects the picture at week 8-13.

Along with this, the results of determining the quality of the bone for implant placement confirm the formation of a bone of suitable quality for implants: in 6 patients, type II bone was formed, and in 5 — type III bone.
These data confirm the fact that the use of this technology is significant progress in conducting an immediate procedure, as well as delayed for a short or medium period of time, as it allows to achieve a significant reduction in the waiting time between surgical interventions. It is also necessary to take into account that, in accordance with traditional literature, it takes 12 months to fully heal a post-ejection well, assuming that during this time the thickness of the alveolar bone can decrease by 50%. Therefore, as mentioned earlier, the question is not only to reduce the time between surgical interventions, but, first of all, in the function, aesthetics and improved ability to predict future treatment.
The paramount aspect is that none of the patients experienced discomfort, inflammation or infection after the PRGF®-ENDORET® removal and filling procedure. In our opinion, this is due to the use of autogenous fibrin for densification of the well. Some authors believe that the closure of the alveoli is not the primary goal; others prefer flap movement to provide primary alveoli closure. However, this technique can reduce the thickness of the gums around the implant, disrupting the aesthetic appearance of the patient. On the contrary, the use of autologous fibrin does not lead to any side effects, and this procedure is safe and easy for a specialist, as well as inexpensive and effective for the patient. Despite the fact that the number of patients in this study is small, we sought to study the regeneration effect when using PRGF®-ENDORET® and subsequent densification with a fibrin membrane in various tooth locations — both on the upper and lower jaw. The results confirm that PRGF®-ENDORET® has an outstanding regenerative effect in the various studied alveoli, which indicates its therapeutic potential.
These results led us to the following thoughts: what will happen if we study the same protocol for applying PRGF®-ENDORET® on a new group of patients over a longer time period? Will density increase significantly and bone quality will change?
No sooner said than done. We examined 8 new patients (3 men and 5 women) who were examined with BTI Scan® II at 14-16 weeks after removal, reaching very close density values ​​in the middle of the alveoli (567 Hounsfield units) and slightly lower, although not significantly, outside and inside the proposed site for implantation (Figs. 29 and 30).
This indicates that we should not seek to enhance the favorable regenerative effect of PRGF®-ENDORET® after longer periods of time, but, on the contrary, should mean improvement and benefit to the patient in a shorter time.
Then, until what point will the initial determination of bone density and quality produce equally positive results? This question arises as a result of the excellent results obtained in some patients, especially in whom CT was performed at 8 weeks after removal. That is why it is more advisable to conduct research in this direction in order to find out whether it is possible to achieve equally positive results in a shorter period of time, reducing the patient's waiting time.
Fig. 29 and 30: Bone density inside the alveoli and at the periphery of the site of the future implant at 14-16 weeks after removal.


This article discussed the treatment of a well after removal using the PRGF®-ENDORET® technique, which was previously described by our research team (7, 9) as predictable. This is probably the best biomaterial for the well after removal, since it is a 100% autogenous product obtained simply and economically (from 20 cm3). In cases of severe loss of the vestibular plate, it can be used in combination with biomaterials or, preferably, with autologous bone (7.9).
In the previous comprehensive clinical study, the same procedure was used in more than 2000 patients, who were then observed for 5 years, during which no side effects were noted. On the contrary: there was more accelerated epithelization, less pain and less inflammation. No complications were observed at all, as was not a single case of dry alveolitis. Further studies are needed to compare the effectiveness of this procedure with others, such as moving a connective tissue graft or a split flap, but soft tissue regeneration is more effective using the PRGF®-ENDORET® procedure, and it is recommended for most removal cases, regardless of whether further installation is planned. implant or not. Regarding time, this study makes it obvious that with small defects, 8 to 10 weeks is enough; with large defects — after 14 — 16 weeks, you can guarantee the best indicators of bone quality. (Fig. 31 — 35).
Fig. 31: Initial x-ray of one of the patients involved in the study. The lesion at the bifurcation site and the apical focus of the medial root are indications for tooth extraction.

Fig. 32: Photo at the time of the delete operation.
Fig. 33: Photograph of access for implant placement after 3 months.


Fig. 34: Photograph of an implant placement operation. You can see that the degree of regeneration allows the installation of the implant.
Fig. 35: X-ray control of the final rehabilitation after 3 months.