Results

Patients were surgically treated and rehabilitated between January 2015 and March 2017. A total of 75 implants were placed, of which 33 were installed in sites grafted with the combination of βTCP and autogenous bone, 31 were placed in sites grafted with βTCP alone, and 11 were installed in native bone sites (Fig. 1). Membrane perforation occurred in three maxillary sinuses; however, these events did not compromise the surgical procedure or result in any complications. The perforations were isolated and covered with a collagen membrane. All implants were successfully placed without further complications.

Fig. 1: CONSORT 2025 Flow Diagram illustrating the process of participant selection, allocation, follow-up, and analysis in the study

Implant stability analysis

No significant differences were observed between the groups regarding implant insertion torque in grafted areas or native bone sites (37.71 [30.00] ± 14.52 Ncm for sites grafted with βTCP + autogenous bone 1:1; 41.88 [40.00] ± 15.80 Ncm for sites grafted with βTCP alone; 46.82 [45.00] ± 15.54 Ncm for native bone sites). Additionally, no significant differences were found between the groups in the resonance frequency analysis. Implants placed in sites grafted with βTCP + autogenous bone 1:1 exhibited primary stability values of 28.50 ± 19.50, implants placed in sites grafted with βTCP alone presented values of 22.50 ± 12.50, and implants placed in native bone sites presented values of 18.50 ± 4.50 (Fig. 2).

Fig. 2: Box plot of mean implant insertion torque (A) and primary stability (B). Specifically, the mean insertion torque values were 37.71 ± 14.52 Ncm in areas grafted with β-TCP + AB 1:1, 41.88 ± 15.80 Ncm in areas grafted with β-TCP alone, and 46.82 ± 15.54 Ncm in native bone areas. Implants placed in areas grafted with β-TCP + AB 1:1 showed the highest primary stability values (28.50 ± 19.50), followed by implants in areas grafted with β-TCP alone (22.50 ± 12.50). Implants placed in native bone areas presented the lowest primary stability values (18.50 ± 4.50)

Histomorphometric analysis

Regarding the composition of the repaired tissue, sinuses grafted with βTCP + autogenous bone 1:1 showed values of 43.75 ± 13.67% bone, 7.58 ± 6.03% remaining bone substitute, and 48 ± 10.65% soft tissue, and sinuses grafted with βTCP alone presented values of 49.32 ± 13.41% bone, 3.22 ± 8.46% remaining bone substitute, and 47.45 ± 12.61% soft tissue. No significant differences were observed between the groups in terms of the composition of the repaired tissue (Fig. 3). The bone tissue associated with the residual autogenous bone and β-TCP particles predominantly exhibited an immature morphology, with no clear evidence of complete lamellar maturation.

Fig. 3: Histological sections of sinuses grafted with β-TCP + AB 1:1 (A) and with pure β-TCP (B), and box plot of grafted area composition (C). Sinuses grafted with β-TCP + AB 1:1 showed 43.75 ± 13.67% bone, 7.58 ± 6.03% residual bone substitute, and 48 ± 10.65% soft tissue. Sinuses grafted with pure β-TCP presented 49.32 ± 13.41% bone, 3.22 ± 8.46% residual bone substitute, and 47.45 ± 12.61% soft tissue

Tomographic analysis

Both grafts promoted an increase in the height of the surgical bed where implants were subsequently placed. In the βTCP + autogenous bone 1:1 group, linear heights of 3.38 ± 1.56 mm at baseline, 14.18 ± 3.54 mm at 14 days post-surgery, and 12.12 ± 3.54 mm at 10 months post-surgery were recorded, while in the βTCP-only group, linear heights of 3.17 ± 1.51 mm at baseline, 15.62 ± 2.41 mm at 14 days post-surgery, and 11.81 ± 2.12 mm at 10 months post-surgery were observed. However, no significant differences were found between the groups regarding this parameter. At 10 months, the βTCP + autogenous bone 1:1 group maintained values of 85.17 ± 24.69% of the grafted height relative to the 14-day measurement, whereas the βTCP group maintained 76.50 ± 17.27% of the grafted height. The amount of initial bone influenced overall graft stability (r = 0.55; p = 0.008); however, this correlation was statistically significant only in sinuses grafted with βTCP (r = 0.67; p = 0.01) (Fig. 4). Representative images of the tomographic scans obtained before, 14 days after, and 10 months after the maxillary sinus floor elevation procedure are shown in Fig. 5.

Fig. 4: Evaluation of the linear height of the surgical bed at different time points (baseline, 14 days, and 10 months after surgery) in the groups grafted with β-TCP + AB 1:1 and β-TCP. Both groups showed a significant increase in surgical bed height after grafting, followed by a reduction at 10 months, with no significant differences between the groups. The maintenance of the grafted area height relative to the 14-day period was 85.17 ± 24.69% in the β-TCP + AB 1:1 group and 76.50 ± 17.27% in the β-TCP group. The correlation between the initial residual bone and graft stability was significant in the β-TCP group (r = 0.67; p = 0.01)

Fig. 5: Representative panoramic images of the tomographic analyses of the groups at baseline, and 7 days and 10 months postoperatively