Evaluation of I-PRF-Enriched Bone Graft Matrix (Sticky Bone) Among Patients Requiring Sinus Lift Operation: A Retrospective Comparative Study

Introduction

The posterior maxilla is frequently considered a challenging anatomical region for dental implant placement due to insufficient bone volume, poor bone quality, and the presence of the maxillary sinus [1]. Over time, alveolar ridge resorption combined with sinus pneumatization leads to further reduction in available vertical bone height. In such cases, sinus lift surgery has become a widely accepted procedure to enable implant-supported rehabilitation [2,3].

Bone resorption in the posterior maxilla represents a substantial clinical challenge, particularly among patients with long-standing edentulism. Because of low bone density and anatomical limitations imposed by the maxillary sinus, this region often lacks sufficient vertical bone height for predictable implant placement. Sinus augmentation procedures, commonly termed sinus lifts, are performed to facilitate implant placement by elevating the sinus membrane and placing bone graft materials to promote new bone formation [3,4]. Graft materials used in sinus augmentation have been widely investigated. Although autogenous bone is considered the gold standard due to its osteoinductive properties, disadvantages such as donor site morbidity and limited volume availability have prompted the use of allografts [5].

Recent advances in tissue engineering have led to the incorporation of autologous blood-derived biomaterials in grafting procedures. Injectable platelet-rich fibrin (I-PRF) is a second-generation platelet concentrate rich in growth factors that enhance angiogenesis and osteogenesis [6]. Sticky bone – comprising particulate bone graft combined with I-PRF – forms a cohesive and moldable grafting material with potential advantages in stability, handling, and biological performance. Previous studies have demonstrated improved handling characteristics and favorable biological outcomes using sticky bone; however, direct comparative studies with conventional grafting materials remain limited [7,8].

Accordingly, the present study aimed to compare the clinical and radiographic outcomes of conventional particulate bone grafting and I-PRF-enriched bone graft matrix (sticky bone) in lateral sinus lift procedures performed simultaneously with implant placement. Primary outcome measures were radiographic evaluation of bone gain and bone resorption over a 6-month postoperative follow-up period.

Material and Methods

STUDY DESIGN AND LIMITATIONS:

This study was designed as a retrospective comparative analysis, which inherently limits control over confounding variables and may introduce selection bias. Additionally, the relatively small sample size and retrospective data collection restrict the generalizability of the findings. These limitations were considered during data interpretation and are acknowledged accordingly.

ETHICS APPROVAL AND PATIENT SELECTION:

This study was conducted at the Faculty of Dentistry, Eskişehir Osmangazi University; it was approved by the Non-Interventional Clinical Research Ethics Committee (IRB 2023-53; decision date: June 20, 2023). The study adhered to the principles of the Declaration of Helsinki, and informed consent had been obtained from all patients at the time of treatment.

Patient records of individuals who underwent lateral sinus lift surgery with simultaneous implant placement between January 2014 and June 2023 were retrospectively reviewed. All eligible patients meeting the inclusion criteria during this period were included consecutively. Inclusion criteria comprised systemically healthy, non-smoking patients with insufficient residual bone height (<6 mm) in the posterior maxilla requiring sinus augmentation for implant placement. Patients with systemic diseases, a history of smoking, previous sinus pathology, or incomplete radiographic records were excluded.

GROUP ALLOCATION:

Group allocation was solely based on grafting material used at the time of surgery. The allograft material used in this study was a cortico-cancellous allograft (Atident, Atigen-Cell, Trabzon, Türkiye) with a particle size of 0.5 to 1.0 mm. The same graft material was used in all groups.

Conventional particulate bone grafts were routinely used in the earlier years of the study period; I-PRF-enriched bone graft matrix (sticky bone) was introduced into clinical practice at our institution after its clinical adoption and availability. Therefore, patients were assigned to the conventional graft group (group 1) or sticky bone group (group 2) according to the graft material documented in their surgical records. Surgeon preference did not influence patient inclusion. All cases that met eligibility criteria during the defined time frame were included, thereby minimizing selection bias inherent to the retrospective study design.

SURGICAL PROCEDURE:

All sinus lift procedures were performed using the lateral window technique by experienced surgeons who followed standardized surgical protocols. I-PRF was prepared by collecting 10 mL of venous blood in plastic tubes without anticoagulant, followed by immediate centrifugation at 700 rpm for 3 minutes. The upper orange-colored liquid fraction was aspirated using a sterile syringe and mixed with the particulate allograft. The resulting cohesive and moldable graft material (ie, “sticky graft,”) was used for augmentation procedures. In group 1, the sinus cavity was augmented using particulate allogeneic bone graft material. In group 2, sticky bone was prepared by mixing particulate bone graft with I-PRF and applied after sinus membrane elevation.

RADIOGRAPHIC EVALUATION AND MEASUREMENTS:

Radiographic assessments were performed using panoramic radiographs obtained preoperatively, immediately postoperatively, and at 6 months postoperatively. All images were analyzed using Planmeca Romexis software (Planmeca Promax, Helsinki, Finland). Vertical bone height measurements were standardized by measuring the distance from the most coronal point of the alveolar crest to the most inferior point of the elevated sinus floor along the planned implant axis (Figure 1). After membrane elevation, graft boundaries were radiographically defined as the radiopaque region extending from the sinus floor to the graft apex. Calibration was performed using known implant lengths to minimize magnification-related errors inherent to panoramic imaging.

All measurements were performed by a single experienced examiner who was blinded to group allocation. To assess intraobserver reliability, measurements were repeated in 20% of randomly selected radiographs after a 2-week interval. Intraclass correlation coefficient analysis demonstrated excellent measurement reliability (coefficient >0.90).

Radiographic deviation was calculated to assess measurement accuracy relative to the known implant length. The radiographically measured implant length was compared with the manufacturer-reported (actual) implant length. Deviation percentage was calculated using the formula below. Negative values indicated radiographic underestimation, whereas positive values indicated overestimation. This metric was used to evaluate calibration accuracy and radiographic stability over time.

SAMPLE SIZE:

Post hoc power analysis was performed using G*Power software (version 3.1.9.7) to confirm sample size adequacy. The analysis was based on a 2-tailed independent samples t-test, selected in accordance with the primary outcome variable comparing radiographic bone resorption between the 2 grafting approaches. The effect size (Cohen’s d) was estimated at 1.3, reflecting the magnitude of the observed intergroup difference. The alpha level was set at 0.05, and the desired statistical power (1−β) was defined as 0.80. Under these assumptions, the minimum required sample size was 10 patients per group. Given that 12 patients were included in each group, the actual sample size was considered sufficient to detect clinically meaningful differences between the study groups.

STATISTICAL ANALYSIS:

Statistical analyses were performed using SPSS software (version 25.0; IBM Corp., Armonk, NY, USA). All analyses were conducted at the patient level, with each patient considered a single independent observational unit. Prior to statistical testing, data normality was assessed using the Shapiro-Wilk test. Given that all variables demonstrated a normal distribution (P>0.05), parametric tests (paired and independent samples t-tests) were performed. The statistical significance threshold was set at P<0.05.

Results

In total, 24 patients were included in the study (16 women and 8 men). In group 1, 5 patients (41.7%) were men and 7 (58.3%) were women; in group 2, 3 patients (25.0%) were men and 9 (75.0%) were women. The demographic distribution of the study population is summarized in Table 1. The mean age of patients in group 1 was 47.25±9.32 years (range: 31–65); the mean age in group 2 was 45.42±13.41 years (range: 23–66). Statistical analysis showed no significant difference between groups in terms of age (P=0.702). The mean preoperative residual bone height was approximately 3.1±0.8 mm and did not significantly differ between groups (P>0.05).

Radiographic evaluation demonstrated a significant increase in bone height in both groups immediately after surgery. Mean preoperative-to-immediate postoperative bone height gains were 11.94±1.99 mm in group 1 and 10.15±1.57 mm in group 2. Intergroup comparison revealed that the initial bone gain was significantly greater in group 1 than in group 2 (P=0.023) (Table 2).

At the 6-month postoperative follow-up, both groups exhibited a reduction in augmented bone height. Mean bone losses between immediate postoperative and 6-month measurements were 2.61±0.93 mm in group 1 and 1.07±0.65 mm in group 2. This statistically significant difference indicated greater bone resorption in group 1 (P<0.001).

When bone loss was expressed as a percentage of the immediate postoperative bone height, group 1 demonstrated a significantly higher resorption rate (16.50±5.47%) compared with group 2 (7.74±4.48%) (P<0.001), suggesting superior bone preservation in group 2 (Table 2).

Radiographic deviation analysis based on implant length showed no statistically significant difference between groups concerning immediate postoperative measurements (group 1: −4.88±2.74%, group 2: −3.56±2.20%; P=0.208). However, at the 6-month postoperative evaluation, the deviation was significantly greater in group 1 (−4.68±2.15%) than in group 2 (−2.61±1.10%) (P=0.007), indicating improved radiographic stability in group 2 (Table 2).

Discussion

STUDY LIMITATIONS:

First, the retrospective design limits control over confounding variables and may introduce selection bias. Second, the relatively small sample size restricts the generalizability of the findings. Third, radiographic evaluation was based on panoramic images, which are inherently limited by magnification and distortion despite calibration procedures.

Conclusions

Although conventional grafting resulted in greater initial bone gain, the use of sticky bone provided considerable short-term benefits in bone preservation after lateral sinus lift procedures. Radiographic evaluations at 6 months demonstrated significantly reduced bone resorption and improved graft stability in patients receiving sticky bone compared with those receiving conventional particulate grafting. Within the limitations of this retrospective study and short follow-up period, these findings suggest that sticky bone can offer a clinically relevant advantage in maintaining augmented bone height after sinus lift surgery. Further prospective, long-term, and 3-dimensional radiologic studies are required to confirm these outcomes.

Data Availability

The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.