Introduction and review of literature
Mandibular fractures are common facial injuries and their treatment is one of the most frequent forms of therapy provided by oral and maxillofacial surgery. In the management of any fracture of bone, the goals are to restore function to the affected bone by ensuring union of the fractured segments and re-establish prefracture strength of the bone, to restore any contour defect that might arise as a result of the injury, and to prevent infection at the fracture site 1.
The effects of platelet-rich fibrin (PRF) membranes on the proliferation of many different cell types have already been assessed in vitro, and the influence of leukocytes on both cell reactions and growth factor release has already been hypothesized 2. Several applications of PRF have already been described in oral surgery, ear–nose–throat, and plastic surgery; PRF seems to be particularly useful as an osteoconductive filling material during sinus-lift procedures 3.
Platelet-derived growth factor (PDGF) is angiogenic and known to stimulate the production and chemotaxis of connective tissue cells and matrix deposition. These properties are all critical to bone healing 4.
Insulin-like growth factor (IGF) has shown a capacity to promote bone cell mitoses and increase the deposition of matrix. PDGF and IGF have shown an ability to work together during the reparative stages of bone healing. PDGF-impregnated and IGF-impregnated devices have been proven to increase bone healing in defects associated with dental implants and teeth 5.
Choukroun’s PRF is defined as an autologous leukocyte-rich and platelet-rich fibrin biomaterial. This easy and open-access procedure was developed in France by Choukroun and colleagues 3. Blood is collected in 9 ml tubes and gently centrifuged for 12 min to divide the blood sample into three layers: a base of red blood cells at the bottom, acellular plasma on the top, and a clot of PRF in the middle. The success of this technique depends entirely on the speed of blood collection and transfer to the centrifuge. If the duration required to collect blood and initiate centrifugation is too long, the technique will fail; the fibrin will polymerize in a diffuse manner in the tube and only a small blood clot without consistency will be obtained.
The PRF membranes release high quantities of growth factors (such as transforming growth factor β-1, PDGF-AB, or vascular endothelial growth factor) and matrix proteins (such as thrombospondin-1, fibronectin, and vitronectin) over at least 7 days. PRF seems to be particularly useful as an osteoconductive filling material during a sinus-lift procedure. In all clinical applications, PRF has to be considered and used as a fibrin-based living biomaterial and not just as a simple source of growth factors 6.
Jang et al.7 created two monocortical defects in each of 10 New Zealand white rabbits using a trephine bur and these defects were prepared to receive two dental implants into the tibia (diameter 3.0 mm, length 10.0 mm). In the experimental group, the peri-implant defect was filled with a combination graft of silk fibroin powder and Choukroun’s PRF. The control was left in an unfilled state. The animals were killed at 8 weeks. They concluded from the results of the study that peri-implant defects can be repaired successfully by the application of Choukroun’s PRF and silk fibroin powder compared with the control group.
In a study carried out by Diss et al.8, implants were placed using PRF as the grafting material in the bone-added osteotome sinus floor elevation technique. The survival rate at abutment tightening (6–12 weeks of healing) and at 1 year was calculated. The radiographic analysis carried out on consecutive radiographs yielded the following results: (i) the mean residual bone height under the maxillary sinus at implant placement and (ii) change in the endosinus bone level. Mean and SD were used to assess the endosinus bone changes in the mesial and distal implant sides at 1 year. The results of the study showed that the use of PRF as a grafting material can lead to endosinus bone gain.
An animal study by Soffer et al. 9 was carried out to study the effect of fibrin on osseous healing and they reported that there were direct interactions between fibrin and osseous cells during healing. The results were contradictory; osseous healing either improved or remained unchanged. These discrepancies may have been caused by differences between the models used: animal type, osseous defect, and fibrin gel.
In a clinical study carried out by Choukroun et al.10, fundamental elements were shown during maxillary cystic ablation. After complete cystic ablation, the cavity fills quickly with blood. This blood clot is nothing more than a ‘light’ version (physiologic version) of PRF. The fibrin clot matrix is a trap for the circulating stem cells. Thus, the physiologic healing time of this cystic cavity lies between 6 months and 1 year. When the cystic cavity is filled with PRF, this physiologic healing phenomenon is accelerated. Because the PRF fibrin matrix is better organized, it can more efficiently initiate stem cell harnessing and healing. A cystic cavity filled with PRF will be completely healed in 2 months instead of the 6–12 months required for physiologic healing.
Nine sinus floor augmentations were performed by Choukroun et al.10. In six sites, PRF was added to freeze-dried bone allograft (FDBA) particles (test group) and in three sites, FDBA without PRF was used (control group). Four months later for the test group and 8 months later for the control group, bone specimens were harvested from the augmented region during the implant insertion procedure. These specimens were treated for histologic analysis. Sinus floor augmentation with FDBA and PRF leads to a reduction in healing time before implant placement. From a histologic point of view, this healing time could be reduced to 4 months 11.
The aim of this study was to evaluate both clinically and radiographically the validity of a local application of PRF on mandibular fracture healing.
Patients and methods
The current study is a prospective comparative study carried on 16 patients ranging in age from 20 to 42 years. All surgical procedures were carried at the Plastic Surgery Unit in the Department of Surgery at Suez Canal University Hospital over a period of two years (from July 2011 to July 2013).
Written informed consent were obtained from all patients in this study.
The patients were divided into two equal groups as follows:
- Group I (the control group): this group included eight patients treated by open reduction and direct osteosynthesis using a 2.0-mm miniplate with a conventional screw where nothing was locally applied on the fracture line.
- Group II (PRF group): this group inlcuded eight patients treated by open reduction and direct osteosynthesis using a 2.0-mm miniplate with a conventional screw where the PRF was locally added to the fracture line.
Preoperative radiographic examination
Standardized preoperative panoramic or CT radiographs were performed for each patient to assess the number and location of line or lines of fracture and degree of displacement, and to localize the inferior dental canal or tooth in the fracture lines.
Patients were admitted to the hospital and the following laboratory investigations were performed before surgery: complete blood count, bleeding time, coagulation time, prothrombin time, partial thromboplastin time, ECG, and chest radiograph for patients older than 40 years of age.
Preparation of platelet-rich fibrin
PRF was prepared according to the technique described by Choukroun and colleagues 7. Twenty minutes before surgery, 10 ml of venous blood was collected in a sterilized dry, neutral glass tube without an anticoagulant. After immediate centrifugation at 300g for 10 min, the platelet-poor plasma, which accumulated at the top, was discarded. PRF was dissected ∼2 mm below its connection to the red corpuscle beneath to include the remaining platelets, which have been proposed to localize below the junction between PRF and the red corpuscle.
Patients fasted for 8 h before surgery. The surgical area was shaved and cleaned preoperatively. Patients were anesthetized using nasotracheal intubation. The oral cavity was first scrubbed with povidone iodine, then all around the extraoral surgical site, followed by draping with sterile towels, exposing only the area of surgery.
Group I (control group)
In group I the fractured segments were manipulated and aligned anatomically using bone clamps. One or two miniplate (depending on the site of fracture) were adapted to the reduced bone segment; the first hole was drilled under copious irrigation and then the other holes were drilled. Fixation of the reduced bony segment was performed with the screws inserted perpendicular to the plate surface. The surgical wound was sutured in layers using vicryl suture material and the skin layer with prolene suture material.
Group II (study group)
Patients in this group were treated by open reduction and direct osteosynthesis using miniplates with the application of PRF in the fracture line.
Clinical and radiographic follow-up was performed for all patients for 6 months postoperatively; the patients were recalled immediately the day after the operation, and at 1, 3, and 6 months postoperatively.
Postoperative care and follow-up
Clinical follow-up was carried out every week at the first month, then at 2, 3, and 6 months postoperatively. Clinical assessment was performed on the basis of the following parameters:
- Postoperative pain: it was measured using a visual analog scale to assess pain, with the end point marked score 0 (no pain) and score 10 (worst pain) at 1 week postoperatively.
- Postoperative trismus mandibular movements: using calipers to measure the maximum interincisal mouth opening, these measurements were performed preoperatively and after 1, 3, and 6 months.
- Soft tissue infection: the wound was evaluated for signs and symptoms of infection including swelling, redness, hotness, discharge, and pain in addition to observation for any manifestation of wound-healing disturbance.
- Occlusion: it was checked in the maximal intercuspal position to ensure proper occlusal relationship including molar relation and midline centralization; any occlusal disturbance including open bite or improper tooth contact was noted.
- Stability of the fractured segments.
- Teeth related to the fractured line (tooth damage).
- Assessment of the sensory and motor nerve function: assessment of the sensory function of the inferior alveolar nerve was performed subjectively by asking the patient about any alteration in sensation in addition to an objective examination using a dental probe to assess the sensory changes along the distribution of the mental nerve through examination of lip sensation in comparison with the contralateral side.
- Non-union, malunion, and malocclusion.
Radiographic follow-up was carried out by digital panoramic radiographs at the following intervals: immediately postoperatively, and at 1, 3, and 6 months postoperatively. Radiographic assessment was performed on the basis of the following parameters:
- Width of the fracture line.
- Bone surrounding plate.
- Teeth related to the fracture line.
All radiographs for every patient were imaged using the same electronically controlled panoramic machine; the exposure parameters were considered fixed for all patients at 70 kv and 10 A for 15 s.
Direct digital panoramic radiographs for group I and II were performed to assess the radiodensitometric bone changes in the fracture site immediately postoperatively, and at 1, 3, 6 months postoperatively.
The patients were positioned (for panoramic exposure) according to the standard procedure as follows: the patient’s head was aligned so that the dental arches were located in the middle of the focal trough.
Data management and analysis
The data were collected and the significance of differences between groups was assessed by analysis of variance, followed by an independent t-test.
The collected data were coded and entered into the statistical package for the social sciences (SPSS, version 17; SPSS Inc., Chicago, Illinois, USA) program for statistical analysis.
Each panoramic image was evaluated for the width of the fracture line after reduction and alignment of the fractured segments.
Quantitative analysis (radiodensitometric analysis)
Densitometric (radiometric) measurement: digitized images were manipulated using the specially designed software of the Digora (Digora for windows 2.5 REV2, single user Demo Build 100, 1993-2007 Soredex).
On each digital image, the mean gray value of the marked region of interest was calculated using the following steps:
- Point A was selected at the fracture line and the pixel density of that point was measured on a scale from 0 to 255 according to its radiopacity, wherein the maximum radiopaque is 255. A zero scale was assigned to the totally black regions (totally radiolucent) and 255 for totally white regions; values in between were represented by different shades of gray.
- A second point (point B) was selected at the same level and just next to the first area, but sound bone and pixel density were also measured as before.
- The difference between these two areas was calculated as the difference between bone density (pixel density) at the fracture line (point A) and at sound bone (point B).
To standardize the position of the point of interest under investigation, the exact coordinates (x and y coordinates) for each of points A and B were calculated for each case and repeated during the follow-up radiography.
One month postoperatively
- Wound dehiscence or plate exposures were not observed in any case. The mucosa overlying the miniplates appeared healthy and of normal color and texture. Extraoral wound scars became hidden in the shadow of the inferior border of the mandible and became fainter with time.
- Measurements of mouth open were decreased compared with preparative measurements.
- Bimanual examination of the fractured segments showed absolute stability. A smooth uniform inferior border of the mandible was palpated in all cases, except for case no. 8 in group I, in whom mobility of the bony segments was detected, because of the presence of a tooth in the fracture line, which was treated by extraction of the tooth and intermaxillary fixation (Figs 1–4).
Three and six months postoperatively
- All cases showed stability of the bony segments, with no detected mobility of the bony segments.
- Measurements of mouth open increased compared with the previous months.
- At the end of the follow-up period, all cases presented with normal occlusion, healthy soft tissue, and proper alignment of the mandibular inferior border. Also, extraoral wound scars became unnoticeable in all cases by the end of follow-up. Neither infection nor mobility was observed in any of the teeth related to the fracture line for any of the patients. The teeth remained vital, without the need for any therapeutic interference, except case no. 1 in group I and case no. 1 in group II; we extracted the tooth after 6 months postoperatively.
- No sensory or motor nerve dysfunction was reported or observed in any of the patients, except case no. 5 (group II), who still complained of numbness of the lower lip and chin (Figs 5–9).
Qualitative radiographic results
- Immediate postoperative radiograph:
- Immediate radiographic examination of all cases showed properly reduced fractured segments with narrowing of the interfragmentary gap. In all cases, the inferior border of the mandible was properly aligned.
- One-month postoperative radiograph:
- The interfragmentary gap was also observed, with no significant difference.
- Three-month postoperative radiograph:
- Radiographic examination showed greater healing of fracture lines with proper alignment of the inferior border of the mandible and the beginning of disappearance of the interfragmentary gap.
- Six-month postoperative radiograph:
- The fracture line became unidentifiable in all cases; no abnormal radiographic changes were observed in relation to both the plate and the teeth within the fracture line in all cases.
Quantitative radiographic results
A comparison was made of the pixel density values among the three groups in terms of the bone density immediately postoperatively, and at 1, 3, and 6 months postoperatively.
- Radiographic analysis results for the fracture line:
- From Table 1, it is clear that the mean and SDs of bone mineral densities (BMDs) for two groups were as follows:
- In group I BMD was 56.07±12.7 immediately postoperatively, 47±12.7 at 1 month, 24.5±7.0 at 3 months, and 12.1±2.8 at 6 months, whereas in group II (PRF group), the mean BMD was 59.5±6.7 immediately postoperatively, 43.1±3.4 at 1 month, 13.3±3.4 at 3 months, and 5.1±2.1 at 6 months.
- Changes in density over time:
- Group I (the control group):
- From Table 2, it is clear that a highly significant difference was detected in the study period between immediately postoperatively and at 3 months, immediately postoperatively and 6 months, at 1 and 3 months, and at 1 and 6 months.
- A significant difference was detected in the same group between 3 and 6 months, whereas no significant difference was detected in the same group immediately postoperatively and at 1 month.
- Group II (PRF group):
- From Table 2, it is clear that a highly significant difference was detected in the study period, immediately postoperatively and at 3 months, immediately postoperatively and at 6 months, at 1 and 3 months, at 1 and 6 months, and at 3 and 6 months.
- No significant difference was detected in the same group immediately postoperatively and at 1 month.
- Comparison between the study groups are shown in Tables 1–3.
In the present study, radiographic observation of PRF showed better bone healing at the mandibular fracture line compared with the control group at 3- and 6-month time intervals. This observation was in agreement with that of Zhao et al. 12. In their case report study, the clinical and histologic characteristics of a patient who underwent tooth extraction that was filled with PRF were reported. The right mandibular second molar was removed from a 47-year-old male patient and the socket was filled with PRF as the sole grafting material in preparation for placement of an implant after wound healing. The extraction site was re-entered surgically for implant placement. A cylindrical sample core of the newly formed tissue was collected from the socket for histological evaluation. During clinical healing, neither infectious episodes nor untoward clinical symptoms were observed. At the time of implant insertion, the socket was completely filled by a hard material, which, on probing, showed consistency of bone. An image with bone-like density was found within the extraction socket by panoramic radiography.
The objectives of a study carried out by Mazor et al. 13 were to assess the usefulness 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; 41 implants from three different systems with different screw designs were placed. After radiologic analyses, the location of the final sinus floor was always in the continuation of the end of the implant. All biopsies indicated well-organized and vital bone. They concluded that, 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 naturally 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 to be a relevant option, particularly for the protection of the Schneiderian membrane.
The present study showed that PRF application in the fracture line mandible led to greater bone formation than that in the control group. The reason for this may be the higher levels of growth factors in PRF. Another reason may be related to the intrinsic nature, content, and architecture of the PRF biomaterial. Moreover, fibrin seems to be a relevant matrix to support osteoblastic growth and differentiation, and it is used frequently during bone tissue-engineering experimentations 14. This finding was in agreement with that of Zhu et al.14 in their experimental study on rats. The aim of that study was to compare the effects of platelet-rich plasma and PRF glue on bone formation in bone tissue engineering. Histomorphometric analysis showed that the nodules contained 14.9±4.1% newly formed bone when using platelet-rich plasma and 19.8±3.6% newly formed bone when using PRF glue.
Conflicts of interest
There are no conflicts of interest.
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© 2014 Egyptian Associations of Oral and Maxillofacial Surgery
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