Effect of platelet rich plasma on bone regeneration in maxillary sinus augmentation (randomized clinical trial)

Abstract

This study evaluates bone quality in sinus augmented with autogenous bone with or without platelet rich plasma (PRP) mix. 15 partially edentulous patients requiring maxillary sinus floor augmentation, followed by implant insertion were studied. In Group I, 5 patients underwent maxillary sinus lifting with autogenous bone augmentation and implant insertion at 6 months post grafting. In Group II, 10 patients underwent maxillary sinus lifting with autogenous bone augmentation mixed with PRP prepared from the patient’s own blood with implant insertion at 4 or 6 months post grafting ( n = 5 for each implantation time). A core biopsy was taken at the time of implant placement for histological and histomorphometric evaluation. Immediately and 3 months after implantation, Group I showed the statistically significant highest mean bone density ( p = 0.046 and 0.022, respectively). At 6 months post-implantation, Group II showed the statistically significant highest mean bone density ( p = 0.041). Histomorphometric analysis showed that Group I had the statistically significant highest mean value (39.5 ± 7.4; p = 0.003). Enrichment with PRP did not significantly improve bone density or morphometric value at 3 months post grafting. PRP enriched bone grafts were associated with superior bone density at 6 months post grafting.

Augmentation of the maxillary sinus floor with autogenous bone or bone substitutes is commonly used to increase bone volume prior to placement of implants in the edentulous posterior maxilla. Autogenous bone grafting, the gold standard for bone regenerative material, is preferred in procedures involving alveolar reconstruction because of their oestrogenic capacity, low immunogenicity, and flexibility in clinical use. Excellent implant success rates can be achieved in grafted sinuses or ridges when a locally harvested autogenous bone graft is used.

Platelets are known to contain a number of different growth factors which are released into the tissue after injury and can be used as a physiological glue with wound healing properties. Platelet rich plasma (PRP) gel is formed by mixing PRP, derived from centrifugation of autologous whole blood, with thrombin and calcium chloride. PRP gel includes a high concentration of platelets and a native concentration of fibrinogen. Thrombin directly activates platelets, and the calcium ion replenishes that which was bound by the acid citrate dextrose type A anticoagulant and this results in the release of a cascade of growth factors from the platelet alpha granules.

Marx et al. showed an increase in bone formation and bone density (both radiographically and histologically) when using thrombocyte concentrates (PRP) as a source of autologous growth factors in combination with autologous bone grafting.

The success of alveolar ridge rehabilitation using endosseous implants is directly related to bone quality and quantity of the graft, which can be estimated by histomorphometric analysis using optical light microscopy. It is considered a valuable and well established clinical and research tool for studying the pathogenesis of metabolic bone diseases as well as for defining mechanisms by which drugs and grafts affect the bone.

The use of growth factors in combination with different bone regeneration materials for alveolar crest augmentation has been debated in recent years. This study was designed to evaluate the potential benefit of adding PRP mix to the autogenous bone used in maxillary sinus augmentation and to detect whether there is a significant difference in bone quality sinuses augmented using autogenous bone with or without PRP. This study also aims to detect whether a significant difference in bone quality can be seen in implants placed 4 or 6 months after the studied procedure.

Patients and methods

15 patients of both sexes, partially edentulous in the posterior maxilla unilateral or bilateral, and indicated for maxillary sinus augmentation followed by implant insertion, were selected from the outpatient clinic of the Oral Surgery Department, Faculty of Oral and Dental medicine, Cairo University, Egypt. The age of the selected patients ranged from 22 to 54 years (mean 38 years). All patients were informed about the risks and benefits of the procedure, and they gave their written consent to participate. All patients were non-smokers and non-alcoholics and in good general health with no systemic, immunological or debilitating diseases that could affect normal bone healing. Site analysis was performed with panoramic radiography in all cases. Cases with 5 mm bone height or less were included for the search. An upper and lower alginate impression was taken for the construction of study casts. A surgical template was constructed from transparent vacuum-formed material over the dental stone cast, and was properly trimmed. A transparent vacuum-formed acrylic template was fabricated containing metal balls of known diameter as a radiographic marker to determine image magnification.

The patients were classified into two groups. In Group I, 5 patients underwent maxillary sinus lifting with autogenous bone augmentation taken from intra oral sites. Patients underwent implant insertion at 6 months post grafting. In Group II, 10 patients underwent maxillary sinus lifting with autogenous bone augmentation taken from intra oral sites mixed with PRP that was prepared from the patient’s own blood on the day of surgery, this group was divided into two subgroups according to the time of implant insertion. In Group IIA ( n = 5), patients underwent implant insertion at 6 months post grafting. In Group IIB ( n = 5), patients underwent implant insertion at 4 months post grafting.

Patients were randomly assigned to the study groups and the sexes were not equally distributed. Randomization was performed using the allocation concealment process whereby the investigator enrolling participants did not know in advance which group the next person would join.

Operative procedure

3 days before surgery, patients were premedicated with prophylactic antibiotics (ampicillin 250 mg with sulbactam 125 mg tablets two times daily) starting 3 days prior to surgery and continuing for 5 days after surgery. Tablets of pseudoephedrine HCl 120 mg with loratadine 5 mg (Clarinase (Medical Union Pharmaceuticals, Abusultan, Ismailia, Egypt)) were given two times daily, starting 3 days prior to surgery and continuing for 5 days after surgery. Decongestant nasal drops (oxymetazoline HCl 0.05%; Afrin (Medical Union Pharmaceuticals, Abusultan, Ismailia, Egypt)) were given in the side to be operated for four times daily starting 3 days prior to surgery and continuing until the day of surgery.

Surgery was performed under general anaesthesia. Local anaesthesia articaine HCl 4% (Septanest SP, Septodont Pharmaceutical Industries, France) with 1:100,000 vasoconstrictor was used for local haemostasis and injected few minutes before surgery.

Sinus lifting technique

After local anaesthesia infiltration of the region to be grafted, a full thickness mucoperiosteal flap was made and elevated to expose the lateral wall of the maxilla. A no. 8 round diamond bur was used in a straight hand piece, at 40,000 rpm with copious irrigation, to outline the osteotomy into the lateral antral wall with the inferior horizontal segment above the floor of the sinus to allow placing the graft material in the floor of the sinus ( Fig. 1 ). Care was taken to avoid penetration of the sinus membrane. Once the outline was completed, special elevators (surgical sinus freers, Asculap number P00451, 453, 455) were used to gently push the sinus membrane inward. As the dissection continued, the membrane was elevated from the floor, lateral wall, medial wall, and antero-posteriorly to provide a large compartment for graft placement. If any tears in the membrane were visualized, a resorbable collagen membrane (Biocollagen, Bioteck, Torino, Italy) was placed below the lifted sinus membrane to isolate the lower compartment where the graft is to be placed.

Fig. 1
The outline of the osteotomy.

Autogenous bone graft was harvested from intra oral sites (symphysis, and/or external oblique ridge) of the mandible, as explained by Misch. The proposed recipient site for the graft was exposed prior to graft harvest in all cases. In this manner, the dimension and morphology of the bony defect were measured, and minimal time elapsed between graft harvest and placement. The bone graft was milled using manual bone mill and packed into the elevated sinus. A resorbable collagen membrane was used to cover the window on the lateral wall of the sinus and was fixed in place by nails or sutures during the primary soft tissue closure.

Production of PRP for Group II

A blood sample (20 cm 3 ) was collected preoperatively from the patient in tubes contain anticoagulant citrate dextrose-A (ACD-A). Blood was separated using a centrifuge with radius 8.2 cm at 5600 rpm (hard spin), for 15 min to separate the platelet-poor plasma from the erythrocytes, platelets and leukocytes. The centrifuge speed was slowed to 2400 rpm (soft spin) for 10 min to allow for further separation of the platelets and leukocytes from the red blood cell pack. This soft spin produces PRP and separates it from the platelet poor plasma (PPP) free from the obstruction provided by a large number of red blood cells. The resultant PRP was mixed with thrombin/calcium chloride (1000 units/10%) solution to form a gel to allow neutralization of the citrate and activation of polymerization of the fibrin and degranulation of the platelets by thrombin. PRP was stored at room temperature until the surgical team was ready to pack it, in conjunction with the corticocancellous particulate, into the elevated sinus.

Implant placement

Implant placement was performed after a healing period of 6 months for Groups I and IIA and after 4 months for Group IIB following the sinus elevation procedure. Spectra-System implant (Implant Direct LLC, USA) was used in all cases in the current study.

The drills were used at a low speed of 800–1000 rpm, the speed was then reduced to 150–200 rpm for the application of the final drill. Copious cooling irrigation by saline solution (20–60 ml/min) was applied to minimize the trauma resulting from the heat generated by the drills and to maximize the chances of successful osseointegration.

Surgery was performed under local anaesthesia using a paraperiosteal infiltration technique with Articain HCl 4% containing 1:100,000 epinephrine. A crestal incision and two vertical incisions were made to allow sufficient mobility of the buccal flap. A surgical template was applied and drilling was prepared through the openings with standard drills using the bony walls as guides. A pilot hole was made using a twist drill of 2 mm diameter with a depth indicator at 10, 11 and 13 mm. The diameter of the receptor site was increased to the final diameter, which was 1 mm less than that of the implant diameter. As the implant is self tapping, it was inserted to two-thirds of its length manually, followed by the use of an implant mount and a ratchet to screw the implant into bone towards the apical aspect. The implant mount and the ratchet were removed. The implant was sealed with a healing screw with a screwdriver. The surgical site was closed using horizontal mattress 3-0 vicryl sutures.

Postoperative instructions and follow up

Following the primary sinus lifting and the final implant placement procedures, postoperative cold application, prophylactic antibiotics and analgesics were recommended for all patients. All patients were evaluated for postoperative pain, oedema, sinus perforation, infection or nose bleeding.

After 6 months of implant placement, second stage implant surgery was performed and the periosteum was reflected by a crestal incision flap. Rigid fixation of the implant, proper abutment position, crestal bone loss around the implant, adequate zones of attached gingiva, tenderness or discomfort under vertical or lateral forces were evaluated. The gingival former (healing collar) was placed into the implant body and was secured by screws to allow gingival healing before abutment placement. The surgical site was closed using interrupted sutures. The prosthetic phase started 15 days after the insertion of the gingival former (the extender).

Histologic and histomorphometric techniques

At the time of implant placement a core biopsy was performed using a trephine bur of diameter 2.0 mm. The specimens were immediately fixed in 10% buffered formalin, demineralized in 10% ethylenediaminetetraacetic acid (EDTA) for 1 week, and stained with haematoxylin and eosin (H–E) for histological and histomorphometric evaluations. An image analyzer computer system was used for the generation of digital photomicrographs for histomorphometric analysis. The equipment consists of a digital camera attached to a light microscope and a computer system equipped with Leica Quin500 software (Leica Microsystems Inc., Switzerland). The percentage of the area occupied by the newly formed bone trabeculae was estimated in a standard measuring frame in 10 fields in each specimen, using magnification (200×) by light microscopy transferred to the computer screen.

Radiographic evaluation

The radiographic assessment was made with magnification 1:1 using the digital panoramic radiographic technique immediately after the primary procedure and 3 months postoperatively, and was repeated immediately after the implant placement and at 3and 6 months. Linear radio densitometric analysis of the digital images were performed using Digora software (Digora for windows v 1.51 Soredex-Finndent, Finland) by automatically calculating the mean grey shade values on two lines mesial and distal to the implant, extending under the lifted maxillary sinus from fixed reference points drawn directly on the images. The mean density of pixels within the area was recorded.

Statistical analysis

Data were presented as means and standard deviation (SD) values. Paired t -tests were used to compare mean bone density at the mesial and distal sides of the implants. This comparison yielded non-significant difference between the two sides, so the mean of both sides was used for the comparisons. One-way ANOVA was used to compare the groups. Tukey’s post hoc test was used for pair-wise comparison between the means when the ANOVA test was significant. Repeated ANOVA measures were used to study the changes by time within each group. The significance level was set at p ≤ 0.05. Statistical analysis was performed with SPSS 16.0 (Statistical Package for Scientific Studies, SPSS Inc., Chicago, IL, USA) for Windows.

Results

Clinical results

Only 5 of the 15 patients showed a small membrane perforation that was managed by folding the sinus membrane on itself in the process of sinus membrane elevation and by placement of an absorbable collagen membrane under the perforated sinus membrane. No postoperative complications occurred in any of the patients at the host site. Normal wound healing was observed after both the first and the second operations.

The implants were exposed at 6 months post-implantation and were loaded. All implants gave a definitive clear audible ring on percussion. No mobility was detected clinically prior to the final seating of the porcelain prosthesis. All hard and soft tissues surrounding the prosthesis demonstrated excellent tissue health.

Radiographic results (bone density)

In Group I, there was a statistically significant decrease in mean bone density 3 months post-grafting. This was followed by a statistically significant increase in mean bone density immediately post-implantation. A statistically significant decrease occurred in 3 months post-implantation. A further statistically significant decrease occurred in 6 months post-implantation. Comparing the bone density at 6 months post-implantation with the immediate post-surgical measurement, there was a statistically significant decrease in mean bone density ( Fig. 2 , Table 1 ).

Fig. 2
Group I: immediate post-implantation radiograph.

Table 1
The means, standard deviation (SD), results of ANOVA and Tukey’s test for comparison of bone densities in the three groups.
Period Group P -value
Group I Group IIA Group IIB
Mean SD Mean SD Mean SD
Immediate post-grafting 162.8 22.3 144.6 14.1 159.5 22.1 0.778
3 months post-grafting 144.5 35.5 151.5 37.8 159.2 17 0.856
Immediate post-implantation 170.4 a 22.3 129.4 b 34.1 148.4 b 18.3 0.046 *
3 months post-implantation 157.3 a 10.1 137.9 b 18.7 133.6 b 11.4 0.022 *
6 months post-implantation 139.8 b 20.2 136.7 b 18.4 155.8 a 11.5 0.041 *
P -value 0.004 * <0.001 * <0.001 *
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Jan 24, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Effect of platelet rich plasma on bone regeneration in maxillary sinus augmentation (randomized clinical trial)
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