The presence of an idiopathic bone cavity (IBC) is usually identified during routine dental radiographic examinations. The purpose of this study was to investigate the effect of platelet-rich plasma (PRP) on bone healing in the idiopathic bone cavity. This was a single-blind randomized clinical trial. Twenty-four subjects were assigned randomly to two groups. Subjects in group 1 received PRP through a buccal window approach, and those in group 2 underwent conventional management via the creation of a window on the buccal wall and curettage of the walls of the defect. Subjects were followed up at 3, 6, and 9 months after the intervention. The amount of bone formation as determined on panoramic radiographs was divided into four categories: stage 1: ≤25% of the defect showed opacity; stage 2: 25–50% of the defect showed opacity; stage 3: 50–75% of the defect showed opacity; and stage 4: >75% of the defect showed opacity. There was a significant difference between the two groups with regard to the various healing stages at the three time points ( P < 0.05). When compared with conventional management of the idiopathic bone cavity, the use of PRP may enhance bone formation.
Traumatic bone cysts were first reported by Lucas and Blum in 1929, and were subsequently defined by Rushton as single cysts with no epithelial lining, an intact bony wall, and no evidence of acute or chronic inflammation. The term ‘traumatic bone cyst’ is a misnomer, in that the incidence of prior trauma in patients with this entity is the same as that in the general population. The term ‘idiopathic bone cavity’ was introduced by Marx and Stern and is generally accepted for such lesions.
The pathogenesis of idiopathic bone cavities remains controversial. Trauma is the most frequently discussed aetiological factor in the formation of an idiopathic bone cavity. The presence of a history of trauma is extremely variable in the reported series of cases, ranging from 17% to 70%. There is, however, general agreement that most idiopathic bone cavities present without signs or symptoms as incidental radiographic findings. Rarely, expansion of the cortical plate may take place, with extraoral swelling, and even less commonly there may be erosion through the cortical bone. The lesion is often discovered during a routine radiological examination and is usually asymptomatic at presentation. However, some studies suggest that up to one-third of the patients have symptoms upon presentation, with the main symptoms including swelling, pain, and rarely labial paresthesia.
The radiological appearance is not diagnostic, but the classical appearance is well known. A definite diagnosis can be made only upon surgical exploration. After removal of the overlying cortical bone, the surgeon will encounter an empty cavity. Less commonly, the cavity contains a small amount of straw-coloured fluid. Histopathological examination reveals no remarkable findings. Frequently no biopsy specimen is submitted, particularly in those cases in which an empty cavity is encountered.
The treatment of idiopathic bone cavities includes surgical exploration and curettage to stimulate bleeding within the bony cavity, packing of the cyst cavity with gel foam (Pfizer, New York, USA) that has been saturated with thrombin and penicillin, and bone grafting. Previous studies have shown that the injection of autologous blood into the bony cavity in order to stimulate osteogenesis is followed by rapid resolution of the lesion.
Platelet-rich plasma (PRP), a new application of tissue engineering, is an autologous source of various growth factors, including platelet-derived growth factor (PDGF), transforming growth factor beta (TGF-β), insulin-like growth factor (IGF), and epidermal growth factor (EGF). These growth factors are considered to have the ability to accelerate chemotaxis, mitogenesis, angiogenesis, and the synthesis of collagen matrix, and favour tissue repair when applied to bone wounds. PRP has recently been investigated for the regeneration of bone.
The purpose of this study was to address the following question: Does platelet-rich plasma enhance healing in the idiopathic bone cavity? It was hypothesized that the application of PRP to idiopathic bone cavities of the mandible would enhance the bone healing process. Therefore the aim of this study was to evaluate the enhancing effect of PRP on bone healing in the idiopathic bone cavity.
Materials and methods
A single-blind randomized clinical trial was designed. The study sample was derived from the population of patients presenting to the Department of Oral and Maxillofacial Surgery of Shiraz University of Medical Sciences between 1 January 2010 and 31 December 2013. This study was approved by the medical ethics committee of the study university. Eligible subjects had an idiopathic bone cavity that was identified during routine dental examinations on panoramic radiograph views and wished to follow our treatment protocol. All subjects provided signed informed consent to participate in the study. Subjects were excluded if they had a systemic disease that affected bone healing, were pregnant, had recently undergone corticosteroid therapy, or had undergone a previous surgical intervention for idiopathic bone cavity. Patients who were found to have true cysts during surgical exploration were excluded from the study.
The patients who agreed to undergo the surgical intervention for idiopathic bone cavity lesions were randomized to two groups: subjects in group 1 received PRP through a buccal window approach; those in group 2 underwent conventional management with the creation of a window on the buccal wall and curettage of the walls of the cyst. Subjects were unaware of group assignment.
Preoperative panoramic radiographs and cone beam computed tomography (CBCT) scans were obtained for all subjects. The lesion size was measured on CBCT for each subject. Subjects were followed at 3, 6, and 9 months after the intervention. Panoramic radiographs were taken at each appointment for all subjects. A 15 × 30 digital receptor (Regius RC-110; Konica Minolta, Japan) was used in conjunction with a digital panoramic X-ray machine (Proline XC; Planmeca, Helsinki, Finland).
The amount of bone formation as determined on the radiographs was divided into four categories: stage 1: ≤25% of the defect showed opacity; stage 2: 25–50% of the defect showed opacity; stage 3: 50–75% of the defect showed opacity; stage 4: >75% of the defect showed opacity.
Two examiners assessed the radiographic views independently and reported the stages of healing by direct measurement on panoramic radiograph views at each follow-up time.
Prior to surgery, 20 ml of blood was drawn from each patient and mixed with 5 ml of citrate phosphate dextrose (CPD; Terumo Corporation, Tokyo, Japan) for anticoagulation. PRP gel was produced through centrifugal separation of whole blood. After the first centrifugation (800 × g , 5 min), the blood was separated into plasma and red blood cells. The red blood cells were removed, and after another centrifugation of the remaining plasma (1500 × g , 5 min), the bottom layer, which is rich in platelets and constitutes approximately 10% of the total sample volume, was collected for use as PRP. The PRP was applied in gel form, manufactured by adding 0.5 ml of procoagulant solution to the tube with the liquid PRP and allowing 15 min for the solution to become a gel.
First, 3.6 ml of 2% lidocaine with 1:80,000 epinephrine was injected into the lesion. The bony cavity was subsequently exposed through a full-thickness mucoperiosteal flap. The bone was thin and the underlying cavity was entered easily with a small bone bur by creating a window ( Fig. 1 ). In group 1, PRP gel was injected into the defects and the window covered with a 5 × 10-mm resorable membrane (Jason membrane; Botiss Dental GmbH, Zossen, Germany) ( Fig. 2 ). In group 2, after creating a window on the buccal wall, curettage was performed to enhance blood accumulation inside the defect. A 5 × 10-mm resorable membrane (Jason membrane; Botiss Dental GmbH, Zossen, Germany) was then used to cover the window.
The statistical analysis was performed using IBM SPSS Statistics for Windows, version 19.0 (IBM Corp., Armonk, NY, USA). The independent t -test was applied to compare age and defect size between the two groups. The χ 2 test was used to evaluate stages of bone formation at each time point between the two groups. An inter-examiner reliability analysis was performed using the kappa statistic to determine consistency between the examiners.
Twenty-four of 34 subjects who had an idiopathic bone cavity were included in the two study groups; 10 subjects were excluded from the study because of a true cystic lining. Group 1 consisted of four males and eight females, while there were five males and seven females in group 2. There was no statistically significant difference between the two groups for sex distribution ( P = 0.50). The mean age of subjects was 23.75 ± 5.11 years in group 1 and 24.08 ± 5.24 years in group 2 ( P = 0.88). The size of the idiopathic bone cavity was 6.58 ± 2.77 cm 3 in group 1 and 5.83 ± 2.40 cm 3 in group 2 ( P = 0.39) ( Table 1 ).
|Variables||Group 1 *||Group 2 †||P -value|
|Age (years)||23.75 ± 5.11||24.08 ± 5.24||0.88 §|
|Cyst size (cm 3 )||6.58 ± 2.77||5.83 ± 2.40||0.39 §|
At the first follow-up appointment (3 months after surgery), four patients (33.3%) in group 1 showed stage 1 healing and eight patients (66.7%) showed stage 2 healing. For the same appointment, 10 patients (83.3%) in group 2 showed stage 1 healing and two patients (16.7%) showed stage 2 healing ( Table 2 ). There was a significant difference between the two groups with respect to the stage of healing at this appointment ( P = 0.036).
|Time point||Group 1 * , with healing stages||Group 2 † , with healing stages||χ 2 test|
|Time 1||Stage 1: 4 (33.3%)||Stage 1: 10 (83.3%)||P = 0.036|
|Stage 2: 8 (66.7%)||Stage 2: 2 (16.7%)|
|Time 2||Stage 2: 6 (50%)||Stage 1: 4 (33.3%)||P = 0.022|
|Stage 3: 6 (50%)||Stage 2: 6 (50%)|
|Stage 3: 2 (16.7%)|
|Time 3||Stage 3: 4 (33.3%)||Stage 2: 4 (33.3%)||P = 0.006|
|Stage 4: 8 (66.7%)||Stage 3: 7 (58.3%)|
|Stage 4: 1 (8.3%)|