The Efficacy of Xenograft Polymerized with Platelet Rich Fibrin Versus Autogenous Graft During the Secondary Alveolar Bone Grafting Of Alveolar Clefts: A Randomized Controlled Clinical Trial

Keywords

Autogenous Grafts; Alveolar Clefts; Xenografts; Platelet-Rich Fibrin (Prf).

Introduction

Secondary alveolar bone grafting (SABG) is considered to be an important comprehensive treatment for cleft lip and palate patientsduring the mixed dentition stage [1]. SABG has many advantages likethe stabilization of maxillary dental arch, reaching to a continuous alveolar process, closing theoronasal fistula, facilitating the normal eruption of the impacted teeth into the grafted area, supporting the upper lip, and improving the esthetic appearance [2, 3].

In 1972, SABG technique was introduced by Boyns and Sends. Several types of bone grafting have been used in the medical literature such as: Autogenous bone graft, Allogenic bone graft, and Xenogeneic bone graft.

The autogenous bone graft is considered thegold standard way of bone grafting in which the preferred site of donation is iliac crest bone dueto the sufficient osteoinductive properties and rapid healing [4, 5]. In fact, the cancellous bone has always seen as one of the best materials used in the alveolar clefts management [6]. However, there are many shortcomings associated with this type of bone grafting such as, donor site deterioration, infection, significant pain, high bone resorption rate, and increased hospitality time with the possibility of hematoma [7, 8]. These disadvantages led to search for alternative substances that are biocompatible, resorbable and readily available with bone induction properties [9]. Xenograft refers to a tissue transplanted from one species to another species, usually derived from bovine or porcine dermis [10]. Bovine grafts are similar in structure to the cancellous bone of human origin [11]. Furthermore, it is safe and biocompatible with aboneosteoconductive property [12]. Recently, Choukroun et al in 2006 mentioned the platelet rich fibrin (PRF) as an effective method for bone formation in the alveolar cleft patients [13]. The liquid form of platelet rich fibrin (PRF) is called injectable platelet rich fibrin (I-PRF). I-PRFincrease the healing properties since it is richwithleukocytes and platelets. I-PRF can be mixed with bone graft grains to obtain a sticky bone graft, this sticky bone then is condensed in the alveolar cleft region where it coagulates and formed cohesive crystals within few minutes [14].

Several studies reported that I-PRF able to enhance graft stability, consistency, and integration into thecleft site. as well as it provokes immune response and reduce the graft rejection possibility [15]. There are a limited number of studies in the medical literature compared the autogenous bone graft with the xenogenous bone graft during secondary alveolar bone grafting. Therefore, the aim ofthe current study was to evaluate the clinical and radiological results of secondary alveolar bone grafting using xenograft polymerized with I-PRF comparing with autologous bone graft in patients who have alveolar clefts.

Materials and Methods

Study Design

This prospective study was a two-arm parallel-group randomized controlled clinical trial. This study was carried out at the oral and maxillofacial surgery hospital in Damascus University between March 2017 and September 2019. Ethical approval was obtained from the Local Ethics Research Committee at Damascus University Dental School.

Study samples

The sample size was estimated using G-power software version 3.1.9.2 (Franz Faul, Universitat Kiel, Germany) as following: the effect size of bone density was 1.37 [17], study power was 80 %, the level of significance was 0.05 and the allocation ratio was 1:1. The required sample size was 10 patients for each group.

Twenty patients who have a unilateral alveolar cleft according to LAHS classification [16] aged between 9-13 years were recruited to this study.

Patients with a systemic disease, a contraindication for general anesthesia, a history of failed alveolar bone grafting, a history of chemo-therapy or jaw irradiation or poor oral hygiene were excluded. Figure 1 shows the CONSORT flow diagram of the trial. A pre-surgical orthodontic expansion for the upper dental arch was occured if needed to prepare the cleft area for bone grafting. A removable appliance with expansion screw was applied for 3-4 months to obtain 6 to 8 mm of adequate expansion for maxillary arch which lead to increase in the alveolar cleft width and access to the surgical field more conveniently [18].

36 patients who have cleft lip and palate were diagnosed and screened for eligibility primarily, 24 of them met the study inclusion criteria. The parents of four patients refused to participate in the current study. Informed consent was obtained for 20 patients. They were allocated randomly into two parallel groups using software- generated list of random numbers from the website:www. randomalists.com. Patients in the first group receivedanautogenous bone graft from iliac bone. On the other hand,patients in the second received abovine Xenograft (Bionnovation, Brasil) in the form of granules polymerized with I-PRF.

Surgical procedure

The surgical technique for secondary alveolar bone grafting was performed similarly in both groups by one surgeon under general anesthesia according to a previous study [19]. In the autogenous bone graft group, the surgical intervention on the iliac crest was achieved by a different surgical team to obtain the autologous bone graft.

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Graft bed or basement preparation was achieved by splitting oral mucosa from nasal mucosa and suturing the nasal layer. Therefore, surgical incisions have been done at the alveolar cleft margins to attained sufficient exposure of the defect region (Fig 2). Vestibular incisions have been completed along gingival margin until first molars region followed by vertical released incision by an obtuse angle toward mucosal vestibule. It is critical to reach periosteum at the bottom of the surgical flap to acquired easy mobilization and coverage of bone graft without tension, and then the flap was elevated from buccal and palatal sides along alveolar cleft edges.

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Bleeding is an important factor to the bone grafted area. Therefore, alveolar bone reshaping by small rounded surgical bur has been used to induce bleeding and allow for the resulting mixture ofthe bone graft and blood to be occurred.

The granular tissues were removed from the cleft area, followed by suturing with released flaps without tension. The graft bed was covered by intact mucoperiosteal flaps on both sides in order to prevent infection or ischemic injury. Suturing began in the nasopalatal mucosal area by Vicryl absorbable sutures – 4/0, followed by labial vestibular mucosa over the grafted areausing the same type of sutures.

The autogenous bone grafts were placed in the form of chips in the first group (Fig 3), while bovine graft particles were mixed with I-PRF in the second group (Fig 3).

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I-PRF was prepared by collecting venous blood by the researchers themselves in 9 ml special-duty tube, followed by centrifuging at 3300 rpm speed for two minutes in a horizontal centrifuge. Blood tubes were placed with water tubes during centrifuging to maintain balance according to previous study [14]. At the end of this process blood materials were observed at the bottom of tube and I-PRF orange material above. Then 5 ml of I-PRF were collected by using 20 ml syringe and mixed with Xenograft in a metal tank for 5 minutes by adding graft particles gradually. Polymerization start within 15 minutes then the material was ready to applied as a bone graft within 20 minutes [14] (Fig 4). Patients were instructed to follow postoperative care guidance, and adhere to liquids based diet for one week.

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Concerning patient’s turnaround time (TAT), patients who underwent bovine graft stayed for one day only, while those with iliac crest bone grafts continued their stay in hospital for full three days.

Outcomes Assessment

Clinical Evaluation: clinical evaluation was performed by measuring pocket depth, gingival bleeding, and plaque indices at the adjacent teeth to the alveolar cleft area [12]. This was done after six months of the secondary alveolar bone grafting by two blinded investigators.

Osseo-density Evaluation: Cone Beam Computed Tomography CBCT (Vatech, South Korea) was implemented to get the measure of bone density values in the alveolar cleft region and intact corresponding region at 99 Kv and 16 mA after 6 months of secondary bone grafting. bone density was determined by the two blinded experienced examiners throughout gray values, which are quantitatively converted into Hounsfield (HU) units [20]. The axial view was chosen to measure the bone density (Fig 5).

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Clinical and bone density measurements were repeated three times at different intervals, the average of these measurements was adopted as the final value of the measured variable.

Statistical analysis

Descriptive statistics were analyzed by measuring means and standard deviations for bone density values and clinical variables in both groups. An Independent sample t-Test was used to compare the mean of bone density and pocket depth in both groups. While the difference in plaque index and gingival bleeding index between studied groups was examined by using Chi square test. Data analysis were performed by using SPSS 20.0 (SPSS, Inc, Chicago, IL). And set the value of p at (≤0.05) to obtain a statistically significant test.

Results

As shown in table 1 the mean value for gingival pockets depth of the first and second group were 1.3 ± 0.3 and 1.4 ± 0.3 respectively. By comparing the two groups there was no statistical significant difference regarding gingival pocket depth, plaque index, and gingival bleeding index after 6 months of secondary alveolar bone grafting. In contrast, table 2 shows the statistical significant difference regarding bone density values in the first group between the grafted alveolar cleft region (425 ± 120 HU) and the intact corresponding area (545 ± 120 HU) with p = 0.002.

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Whilethe second group showed no significant difference in the bone density values when comparing between the grafted alveolar cleft region (520 ± 170HU) and the intact corresponding area (510 ± 150HU). Moreover, no statistically significant differences were depicted in the bone density values in the grafted alveolar cleft regions(p= 0.165) and intact corresponding regions (p=0.476) when comparing between the two groups.

Discussion

Skeletal deformities in the cleft lip and palate patients represented major challenge for maxillofacial surgeons, because of the various procedures required to restore normal shape and function of the oral cavity components. Therefore, secondary alveolar bone grafting has become a wide popular procedure for restoring occlusal function in the cleft lip and palate patients. Although, many articles explored different grafting materials and their application, there is still a lack of knowledge concerning possible alternatives to classic grafting materials, hence the importance of this study as it is the first clinical control study comparing xenografts polymerized with I-PRF with autologous graft in the alveolar cleft patients.

Patients were divided into two separate groups autogenous and xenograft polymerized with I-PRF groups, the use of split mouth technique was avoided due to heterogenity of right and left sides in the cleft area for bilateral alveolar cleft patients [21].

Orthodontic expansion were applied for all patients before grafting in a similar manner to some authors [21]. Orthodontic expansion provide enough space for graft application and increase graft absorption rate [23].

Vicryl absorbable sutures were used for closure of the grafting site as this type of sutures is characterized by low tissue reactivity, and continuity of the tensile strength for two weeks after surgery [24].

Cohen's kappa test was used to calculate intra-examiner reproducibility and inter-examiner reliability for the assessment of test variables. The kappa for intra-examiner agreement and inter-examiner reliability was 0.90.

Gingival and periodontal status assessment of the teeth adjacent to the cleft side is an important factor to confirm oral health status. Poor oral hygiene promotes infection in the grafting site, which in turn lead to the bone graft resorption. Thus, clinical evaluation of the periodontal tissues of the adjacent teeth is studied by measuring amount of pocket depth, gingival bleeding, and plaque index [25].

Tiny voxel size could be obtained in cone beam computed tomography (CBCT) which are close to the size of voxel in the computed tomography (CT) [26], Therefore, it is feasible to obtain an accuracy in measuring bone density with less radiation exposure. In addition to that using CBCT is less expansive, more convenient, and ethically justified [27].

Due, et al. in 2018 concluded that en bloc grafts application in 17 years patients yields satisfactory results as enough bone is provided to apply dental implants and orthodontic procedures [5]. In contrast to many studies agreed that using bone grafts in the form of chips is superior to en bloc corticocancellous grafts. Indeed, bone chips are easier to osseo-integrate and remodel with the adjacent bone [28], as indicated in the current study.

Autograft group showed statistically significant difference between grafted alveolar cleft regionand intact corresponding region. This is most probably attributed to the autograft’s high absorption rate, which is in consistent with a previous study [20].

There was no statistically significant difference between alveolar cleft area and the intact corresponding area in the xenografts polymerized with I-PRF group; this may be related to the period of radiographic evaluation. Mich indicated that Xenograft remodeling in large defects requires 6-9 months [29]. The variance in this period is related to the size of grafted area; the results of the present investigation are different with others [12]. Nonetheless, the outcomes of the current study are in consistent with Zhang’s study, which evaluated secondary alveolar bone grafting by using xenografts after six months [30].

Although the bone density value in the xenograft polymerized with injectable I-PRF group (520 ± 170 HU) was higher than that in the autogenous group (425 ± 120 HU) in the cleft area, statistical analysis showed no significance differences between both groups (P=0.190), which is in agreement with others [12]. Many components such as: bone graft form, dimension, quality, and fixation affect remodeling process during secondary alveolar bone grafting. Therefore, the result of this study may related to the amount of bone loss occurs after autogenous bone grafting. The limitations of our study are the short period of follow-up and the small sample size.

Conclusions

Within the limitations of this study, it can be concluded that injectable I-PRF with Xenograft may show favor in bone formation than autogenous bone graft. In addition, there are no negative clinical results when comparing between two types of grafting. Hence, I-PRF material is preferred for cleft lip and palate correction during secondary alveolar bone grafting because of its ease of application and low cost.