Immediate restoration of fixed full-arch prostheses placed on implants in both fresh and healed sockets using the flat one-bridge technique: a 7-year retrospective study.

BACKGROUND: The aim of this retrospective study was to document the long-term clinical efficacy of a surgical-prosthetic technique (the flat one-bridge technique) involving the immediate restoration of both postextraction and nonpostextraction implants supporting full-arch restorations. METHODS: Implants were placed by adapting the axis to the available bone. Flat definitive abutments were connected during surgery and never disconnected to compensate for eventual implant disparallelism. Bone grafting was performed when needed. The patients received a screw-retained provisional restoration within 48 h of surgery and a final screw-retained prosthesis within 1 year. RESULTS: Sixty-six patients received 494 implants distributed in 75 prostheses. The median follow-up was 86 months (range 82-168 months). Only three implants had failed at the last follow-up. Implant survival was 99.6%. CONCLUSION: The flat one-bridge prosthetic protocol is a viable procedure with excellent long-term outcomes. No difference in clinical success could be observed between postextractive and nonpostextractive implants.

Assessment of vinyl polysiloxane as an innovative injection material for the anatomical study of vasculature.

There are numerous injection materials for the study of vasculature in anatomical specimens, each having its own advantages and disadvantages. Latex and resins are the most widely used injection materials but need several days to set. The development of new materials taking shorter time to polymerize might be very useful to improve anatomic specimen study conditions. The aim of the present study was to evaluate vinyl polysiloxane (VPS), a silicon material widely used for dental impressions with the advantage to set very rapidly, as an injection material. We assessed the preparation, use, diffusion and setting time of the product in different anatomical regions (central nervous system, external carotid/jugular, lower limb) to observe its behavior in variably sized vessels. Our results suggest that VPS might be of interest for the study of vessels in anatomical specimens. The main strengths of the product are represented by (1) simplicity of use, as it is a ready-to-use material, (2) very rapid polymerization, (3) availability in a range of viscosities making easier the exploration of small vessels, (4) its better elasticity compared to resins, (5) and finally its availability in a range of colors making it a material of choice for vascular system dissections including those with very small caliber vessels.

Current knowledge and perspectives for the use of platelet-rich plasma (PRP) and platelet-rich fibrin (PRF) in oral and maxillofacial surgery part 2: Bone graft, implant and reconstructive surgery.

Platelet concentrates for surgical use are innovative tools of regenerative medicine, and were widely tested in oral and maxillofacial surgery. Unfortunately, the literature on the topic is contradictory and the published data are difficult to sort and interpret. In bone graft, implant and reconstructive surgery, the literature is particularly dense about the use of the various forms of Platelet-Rich Plasma (PRP) - Pure Platelet-Rich Plasma (P-PRP) or Leukocyte- and Platelet-Rich Plasma (L-PRP) - but still limited about Platelet-Rich Fibrin (PRF) subfamilies. In this second article, we describe and discuss the current published knowledge about the use of PRP and PRF during implant placement (particularly as surface treatment for the stimulation of osseointegration), the treatment of peri-implant bone defects (after peri-implantitis, during implantation in an insufficient bone volume or during immediate post-extraction or post-avulsion implantation), the sinuslift procedures and various complex implant-supported treatments. Other potential applications of the platelet concentrates are also highlighted in maxillofacial reconstructive surgery, for the treatment of patients using bisphosphonates, anticoagulants or with post-tumoral irradiated maxilla. Finally, we particularly insist on the perspectives in this field, through the description and illustration of the use of L-PRF (Leukocyte- and Platelet-Rich Fibrin) clots and membranes during the regeneration of peri-implant bone defects, during the sinus-lift procedure and during complex implant-supported rehabilitations. The use of L-PRF allowed to define a new therapeutic concept called the Natural Bone Regeneration (NBR) for the reconstruction of the alveolar ridges at the gingival and bone levels. As it is illustrated in this article, the NBR principles allow to push away some technical limits of global implant-supported rehabilitations, particularly when combined with other powerful biotechnological tools: metronidazole solution, adequate bone substitutes and improved implant designs and surfaces (for example here AstraTech Osseospeed or Intra-Lock Ossean implants). As a general conclusion, we are currently living a transition period in the use of PRP and PRF in oral and maxillofacial surgery. PRPs failed to prove strong strategic advantages that could justify their use in daily practice, and the use of most PRP techniques will probably be limited to some very specific applications where satisfactory results have been reached. Only a few simple, inexpensive and efficient techniques such as the L-PRF will continue to develop in oral and maxillofacial surgery in the next years. This natural evolution illustrates that clinical sciences need concrete and practical solutions, and not hypothetical benefits. The history of platelet concentrates in oral and maxillofacial surgery finally demonstrates also how the techniques evolve and sometimes promote the definition of new therapeutical concepts and clinical protocols in the today's era of regenerative medicine.

Current knowledge and perspectives for the use of platelet-rich plasma (PRP) and platelet-rich fibrin (PRF) in oral and maxillofacial surgery part 1: Periodontal and dentoalveolar surgery.

Platelet concentrates for surgical use are innovative tools of regenerative medicine, and were widely tested in oral and maxillofacial surgery. Unfortunately, the literature on the topic is contradictory and the published data are difficult to sort and interpret. In periodontology and dentoalveolar surgery, the literature is particularly dense about the use of the various forms of Platelet-Rich Plasma (PRP) - Pure Platelet-Rich Plasma (P-PRP) or Leukocyte- and Platelet-Rich Plasma (L-PRP) - but still limited about Platelet-Rich Fibrin (PRF) subfamilies. In this first article, we describe and discuss the current published knowledge about the use of PRP and PRF during tooth avulsion or extraction, mucogingival surgery, Guided Tissue Regeneration (GTR) or bone filling of periodontal intrabony defects, and regeneration of alveolar ridges using Guided Bone Regeneration (GBR), in a comprehensive way and in order to avoid the traps of a confusing literature and to highlight the underlying universal mechanisms of these products. Finally, we particularly insist on the perspectives in this field, through the description and illustration of the systematic use of L-PRF (Leukocyte- and Platelet- Rich Fibrin) clots and membranes during tooth avulsion, cyst exeresis or the treatment of gingival recessions by root coverage. The use of L-PRF also allowed to define new therapeutic principles: NTR (Natural Tissue Regeneration) for the treatment of periodontal intrabony lesions and Natural Bone Regeneration (NBR) for the reconstruction of the alveolar ridges. In periodontology, this field of research will soon find his golden age by the development of user-friendly platelet concentrate procedures, and the definition of new efficient concepts and clinical protocols.

Do the fibrin architecture and leukocyte content influence the growth factor release of platelet concentrates? An evidence-based answer comparing a pure platelet-rich plasma (P-PRP) gel and a leukocyte- and platelet-rich fibrin (L-PRF).

Platelet concentrates for surgical use are tools of regenerative medicine designed for the local release of platelet growth factors into a surgical or wounded site, in order to stimulate tissue healing or regeneration. Leukocyte content and fibrin architecture are 2 key characteristics of all platelet concentrates and allow to classify these technologies in 4 families, but very little is known about the impact of these 2 parameters on the intrinsic biology of these products. In this demonstration, we highlight some outstanding differences in the growth factor and matrix protein release between 2 families of platelet concentrate: Pure Platelet-Rich Plasma (P-PRP, here the Anitua's PRGF - Preparation Rich in Growth Factors - technique) and Leukocyte- and Platelet-Rich Fibrin (L-PRF, here the Choukroun's method). These 2 families are the extreme opposites in terms of fibrin architecture and leukocyte content. The slow release of 3 key growth factors (Transforming Growth Factor ß1 (TGFß1), Platelet-Derived Growth Factor AB (PDGF-AB) and Vascular Endothelial Growth Factor (VEGF)) and matrix proteins (fibronectin, vitronectin and thrombospondin-1) from the L-PRF and P-PRP gel membranes in culture medium is described and discussed. During 7 days, the L-PRF membranes slowly release significantly larger amounts of all these molecules than the P-PRP gel membranes, and the 2 products display different release patterns. In both platelet concentrates, vitronectin is the sole molecule to be released almost completely after only 4 hours, suggesting that this molecule is not trapped in the fibrin matrix and not produced by the leukocytes. Moreover the P-PRP gel membranes completely dissolve in the culture medium after less than 5 days only, while the L-PRF membranes are still intact after 7 days. This simple demonstration shows that the polymerization and final architecture of the fibrin matrix considerably influence the strength and the growth factor trapping/release potential of the membrane. It also suggests that the leukocyte populations have a strong influence on the release of some growth factors, particularly TGFß1. Finally, the various platelet concentrates present very different biological characteristics, and an accurate definition and characterization of the different families of product is a key issue for a better understanding and comparison of the reported clinical effects of these surgical adjuvants.

Simultaneous sinus-lift and implantation using microthreaded implants and leukocyte- and platelet-rich fibrin as sole grafting material: a six-year experience.

PURPOSE: To assess the relevance of simultaneous sinus-lift and implantation with leukocyte- and platelet-rich fibrin (L-PRF, Choukroun's technique) as sole subsinus filling material. MATERIALS: Twenty-three lateral sinus elevations (SA4 sinus) were performed on 20 patients with simultaneous implant placement. Seven patients were treated with 19 Astra implants (AstraTech, Mölndal, Sweden) and 13 patients with 33 Intra-Lock implants (Intra-Lock Ossean, Boca Raton, FL). L-PRF membranes were used to cover the Schneiderian membrane, the implant tips served as "tent pegs" for the L-PRF-patched sinus membranes, and the subsinus cavity was finally filled with L-PRF clots. Clinical and radiographic follow-up was performed just after implant placement, after 6 months, 1 year and each following year. RESULTS: Six months after surgery, all implants were clinically stable during abutment tightening. The maximum follow-up was 6 years, and all patients were followed up for a minimum of 2 years. No implant was lost during this 6-year experience, and the vertical bone gain was always substantial, between 8.5 and 12 mm bone gain (10.4 ± 1.2). The final level of the new sinus floor was always in continuation with the implant apical end, and the periimplant crestal bone height was stable. CONCLUSION: The use of L-PRF as sole filling material during simultaneous sinus-lift and implantation seems to be a reliable surgical option promoting natural bone regeneration.

Three-dimensional architecture and cell composition of a Choukroun's platelet-rich fibrin clot and membrane.

BACKGROUND: Platelet-rich fibrin (PRF; Choukroun's technique) is a second-generation platelet concentrate for surgical use. This easy protocol allows the production of leukocyte and platelet-rich fibrin clots and membranes starting from 10-ml blood samples. The purposes of this study were to determine the cell composition and three-dimensional organization of this autologous biomaterial and to evaluate the influence of different collection tubes (dry glass or glass-coated plastic tubes) and compression procedures (forcible or soft) on the final PRF-membrane architecture. METHODS: After centrifugation, blood analyses were performed on the residual waste plasmatic layers after collecting PRF clots. The PRF clots and membranes were processed for examination by light microscopy and scanning electron microscopy. RESULTS: Approximately 97% of the platelets and >50% of the leukocytes were concentrated in the PRF clot and showed a specific three-dimensional distribution, depending on the centrifugation forces. Platelets and fibrin formed large clusters of coagulation in the first millimeters of the membrane beyond the red blood cell base. The fibrin network was very mature and dense. Moreover, there was no significant difference in the PRF architecture between groups using the different tested collection tubes and compression techniques, even if these two parameters could have influenced the growth factor content and biologic matrix properties. CONCLUSIONS: The PRF protocol concentrated most platelets and leukocytes from a blood harvest into a single autologous fibrin biomaterial. This protocol offers reproducible results as long as the main production principles are respected.

Choukroun's platelet-rich fibrin (PRF) stimulates in vitro proliferation and differentiation of human oral bone mesenchymal stem cell in a dose-dependent way.

BACKGROUND: Choukroun's platelet-rich fibrin (PRF) is an autologous leukocyte- and platelet-rich fibrin biomaterial. The purpose of this study was to analyse the in vitro effects of PRF on human bone mesenchymal stem cells (BMSC), harvested in the oral cavity after preimplant endosteal stimulation. MATERIALS AND METHODS: BMSCs from primary cultures were cultivated with or without a PRF membrane originating from the same donor as for the cells, in proliferation or osteoblastic differentiation conditions. After 7 days, the PRF membranes were removed. A series of cultures were performed using 2 PRF membranes, in order to measure the dose-dependent effect. Cell counts, cytotoxicity tests, alkaline phosphatase (ALP) activity quantification, Von Kossa staining and mineralisation nodules counts were performed at 3, 7, 14, 21 and 28 days. A last independent series was carried on up to 14 days, for a morphological scanning electron microscope (SEM) observation. RESULTS: PRF generated a significant stimulation of the BMSC proliferation and differentiation throughout the experimental period. This effect was dose-dependent during the first weeks in normal conditions, and during the whole experimentation in differentiation conditions. The cultures without PRF in differentiation conditions did not rise above the degree of differentiation of the cultures in normal conditions with 1 or 2 PRF up to the 14th and 28th day, respectively. The SEM culture analysis at day 14 allowed to show the mineralisation nodules which were more numerous and more structured in the groups with PRF compared to the control groups. DISCUSSION AND CONCLUSIONS: This double contradictory proliferation/differentiation result may be due to the numerous components of PRF, particularly the presence of leukocytes: any culture with PRF is in fact a coculture with leukocytes. It could be the source of differential geographic regulation processes within the culture. The combination of oral BMSC and PRF might offer many potential clinical and biotechnological applications, and deserves new studies.

Sinus floor augmentation with simultaneous implant placement using Choukroun's platelet-rich fibrin as the sole grafting material: a radiologic and histologic study at 6 months.

BACKGROUND: Sinus augmentation with simultaneous implant placement without bone graft material is a hotly debated technique. This technique could be improved and secured by the use of an autologous leukocyte- and platelet-rich fibrin (PRF) (Choukroun's technique) concentrate. The objectives of this study were to assess the relevance of PRF clots and membranes as the sole filling material during a lateral sinus lift with immediate implantation using radiologic and histologic analyses in a case series. METHODS: Twenty-five sinus elevations with simultaneous implantation were performed on 20 patients with Choukroun's PRF as the sole filling biomaterial. For each patient, a presurgical exam and a 6-month post-surgical radiologic exam were performed with a panoramic x-ray and three-dimensional volumetric computed radiography (VCR) to evaluate the subsinus residual bone height and the final bone gain around the implants. In nine patients, 6 months after the sinus lift, bone biopsies were collected on the buccal wall of the alveolar ridge at the level of the osteotomy window, and evaluated by histomorphometry. RESULTS: In this study, 41 implants from three different systems with different screw designs (Biomet 3I Nanotite, MIS Seven, Intra-Lock Ossean) were placed. All implants were inserted in residual bone height between 1.5 and 6 mm (mean +/- SD: 2.9 +/- 0.9 mm). The final bone gain was always very significant (between 7 and 13 mm [mean +/- SD: 10.1 +/- 0.9 mm]). No implant was lost. After radiologic analyses, the position of the final sinus floor was always in the continuation of the end of the implant. All biopsies showed well organized and vital bone. CONCLUSIONS: From a radiologic and histologic point of view at 6 months after surgery, the use of PRF as the sole filling material during a simultaneous sinus lift and implantation stabilized a high volume of natural regenerated bone in the subsinus cavity up to the tip of the implants. Choukroun's PRF is a simple and inexpensive biomaterial, and its systematic use during a sinus lift seems a relevant option, particularly for the protection of the Schneiderian membrane.

Re: "Clinical evaluation of a modified coronally advanced flap alone or in combination with a platelet-rich fibrin membrane for the treatment of adjacent multiple gingival recessions: a 6-month study".

Choukroun's platelet-rich fibrin (PRF) is a fibrin biomaterial with a specific composition, three-dimensional architecture, and associated biology. This letter highlights some key issues related to the use of this complex material during periodontal surgery. First, a reproducible protocol for the production of PRF membranes must be followed to control the quantity and quality of the fibrin matrix, leukocytes, platelets, and growth factors. Second, its use in periodontology must follow two principles founded on tissue-engineering basic rules and classical periodontal concepts. Using this two-principle safe protocol, the use of PRF in periodontal surgery leads to a significant improvement during the early healing phase and to a thick and stable final remodeled gingiva.

The relevance of Choukroun's platelet-rich fibrin and metronidazole during complex maxillary rehabilitations using bone allograft. Part II: implant surgery, prosthodontics, and survival.

Extensive bone grafting remains a delicate procedure, due to the slow and difficult integration of the grafted material into the physiological architecture. The recent use of platelet concentrates aims to improve this process of integration by accelerating bone and mucosal healing. Choukroun's platelet-rich fibrin (PRF) is a healing biomaterial that concentrates in a single autologous fibrin membrane, most platelets, leukocytes, and cytokines from a 10-mL blood harvest, without artificial biochemical modification (no anticoagulant, no bovine thrombin). In this second part, we describe the implant and prosthetic phases of a complex maxillary rehabilitation, after preimplant bone grafting using allograft, Choukroun's PRF membranes, and metronidazole. Twenty patients were treated using this new technique and followed up during 2.1 years (1-5 years). Finally, 184 dental implants were placed, including 54 classical screw implants (3I, Palm Beach Gardens, FL) and 130 implants with microthreaded collar (46 from AstraTech, Mölndal, Sweden; 84 from Intra-Lock, Boca Raton, FL). No implant or graft was lost in this case series, confirming the validity of this reconstructive protocol. However, the number of implants used per maxillary rehabilitation was always higher with simple screw implants than with microthreaded implants, the latter presenting a stronger initial implant stability. Finally, during complex implant rehabilitations, PRF membranes are particularly helpful for periosteum healing and maturation. The thick peri-implant gingiva is related to several healing phases on a PRF membrane layer and could explain the low marginal bone loss observed in this series. Microthreaded collar and platform-switching concept even improved this result. Multiple healing on PRF membranes seems a new opportunity to improve the final esthetic result.

The relevance of Choukroun's platelet-rich fibrin and metronidazole during complex maxillary rehabilitations using bone allograft. Part I: a new grafting protocol.

Extensive bone grafting remains a delicate procedure, because of the slow and difficult integration of the grafted material into the physiological architecture. The recent use of platelet concentrates aims to improve this process of integration by accelerating bone and mucosal healing. Choukroun's platelet-rich fibrin (PRF) is a healing biomaterial that concentrates in a single autologous fibrin membrane, most platelets, leukocytes, and cytokines from a 10 mL blood harvest, without artificial biochemical modification (no anticoagulant, no bovine thrombin). Whether used as a membrane or as fragments, PRF allows a significant postoperative protection of the surgical site and seems to accelerate the integration and remodeling of the grafted biomaterial. These properties are particularly helpful for vestibular bone grafting on the alveolar ridges. Moreover, it provides a very high quality of gingival maturation.A small quantity of a 0.5% metronidazole solution (10 mg) can also be used to provide an efficient protection of the bone graft against unavoidable anaerobic bacterial contamination. This article describes a new technique of total maxillary preimplant bone grafting using allograft, Choukroun's PRF membranes and metronidazole. This first part focused on the preimplant reconstructive treatment using allogeneic bone granules. PRF membranes are particularly helpful to protect the surgical site and foster soft tissue healing. This fibrin biomaterial represents a new opportunity to improve both the maturation of bone grafts and the final esthetic result of the peri-implant soft tissue.

Optical three-dimensional scanning acquisition of the position of osseointegrated implants: an in vitro study to determine method accuracy and operational feasibility.

PURPOSE: Manufacturing complex prosthetic framework on osseointegrated implants requires precision at every step of execution. The purpose of this study was to verify the possibility of applying the technology of image acquisition to determine the spatial position of osseointegrated implants. MATERIALS AND METHODS: An optical three-dimensional scanning technique was employed: its measurement systematic error (bias) was calculated by comparing the results with the detection on a coordinates measuring machine. Measurements were carried out on master casts by doing an in vitro simulation of intraoral conditions. RESULT: This study showed that the bias error value of the three-dimensional optical acquiring system was situated between 14 and 21 microm. CONCLUSION: As far as the accuracy is concerned, it seems possible to use the three-dimensional image acquisition technology as a valid alternative to traditional impression-making procedures. However, the bias levels obtained in this in vitro study will have to be confirmed in a clinical trial.

Controlling systematic perioperative anaerobic contamination during sinus-lift procedures by using metronidazole: an innovative approach.

BACKGROUND AND OBJECTIVES: Analysis of tomodensitometric controls following sinus grafts clearly demonstrates a quite systematic lack of homogeneity. Sinus contamination by anaerobic bacteria seems almost unavoidable during bone graft surgery, and this problem may jeopardize the healing process. The aim of this study was to characterize in a systematic way the nonhomogeneities observed at 1, 2, or 3 months postsurgery within allogenous sinus grafts, and to assess the possible influence of a 0.5% sterile solution of metronidazole incorporated in the sinus bone graft. MATERIALS: This clinical study was conducted on 72 patients treated with single or bilateral sinus-lifts: 94 sinus elevations performed with freeze-dried bone allograft (Phoenix, TBF, Mions, France), with (test group) or without (control group) metronidazole. In the test group, each bone graft was hydrated with 2 mL of a 0.5% metronidazole solution, i.e., only 10 mg of metronidazole. All the patients went through a first presurgical computerized tomography (CT)-scan followed by a second scan performed at 1, 2, or 3 months postsurgery (which was used as the preimplant reference scan). For 11 patients, 2 postsurgical CT-scans were performed respectively at 10 days and 2 months. Using an arbitrary gray scale (Arbitrary Densitometric Unit) which functions according to the Hounsfield unit principle, the degree of radiographic homogeneity of the grafts was established. Density scattering provides some information on the homogeneity or nonhomogeneity of the bone graft. RESULTS: The 12 grafts performed without metronidazole show significant nonhomogeneities at 1, 2, or 3 months. Moreover, when a CT-scan is performed during the first postoperative days (at 10 days), the presence of air bubbles in the graft is confirmed. The tomodensitometric aspects of all grafts treated with metronidazole in this series are absolutely identical: they show a high degree of homogeneity. Sixty-three cases (76.8%) are homogeneous, and 19 cases (23.2%) are significantly homogeneous. The time at which the control scan is performed (10 days, 1, 2, or 3 months) does not seem to influence significantly the degree of homogeneity assessed. In the control group, some inflammatory events associated with facial oedema were observed in 25% of the cases. In the test group, no such event was recorded for the 82 sinus-lifts treated with metronidazole. CONCLUSION: A possible correlation may exist between the occurrence of non homogeneities within the bone grafts and the anaerobic bacterial contamination. The local use of a very small quantity of metronidazole (equivalent to only 1/20 of a common 200 mg oral tablet) could provide more security when performing sinus-lift procedures and an improved quality of the graft. This protocol should not be considered as an antibiotherapy, but only as way to limit the initial contamination of bone graft.