Optimisation of implantation after sinus floor elevation: the one-stage approach

Implant rehabilitation of the atrophic posterior maxilla frequently requires the use of sub-antral augmentation. However, the variability of tissue response and implant stability depending on the biomaterials used remains a major clinical challenge for the implantologist. This study, conducted on 62 patients aged 25 to 65 years presenting with alveolar process atrophy, specifically addresses the issue of peri-implant tissue stability and the reaction of the Schneiderian membrane to two distinct protocols.

The authors' objective was to increase the efficiency of implantation through a rigorous postoperative evaluation of the bone and mucosal parameters of the maxillary sinus. To this end, they tested the hypothesis that a single-stage sinus lift procedure, using allogenic bone rings (Maxgraft Bonering) combined with platelet-rich plasma (PRP), would offer superior results compared to the conventional two-stage approach.

The study thus compares a control group (n=48), treated with a two-stage technique using allogenic bone powder and Lioplast membrane (implantation at 6 months), to an experimental group (n=76) benefiting from simultaneous augmentation with bone rings and PRP gel. Parameters were monitored by CBCT analysis and primary stability measurement (Osstell ISQ) over a period of up to 36 months.

Methodology: Comparison of one-stage vs two-stage protocols

This clinical study followed 62 patients (aged 25 to 65 years) presenting with atrophy of the maxillary alveolar process. The authors compare two surgical approaches distributed over 124 clinical sites (n):

• Control group (n=48): A conventional two-stage protocol. Sinus augmentation uses mineralized allogeneic cancellous bone powder and a "Lioplast" bioabsorbable membrane, with delayed implant placement at 6 months.
• Test group (n=76): A single-stage subantral augmentation. The team used "Maxgraft Bonering" allogenic bone rings, filled the space with a platelet-rich plasma (PRP) gel and protected the site with a bioabsorbable membrane, allowing for immediate implantation.

The evaluation protocol is based on cone beam computed tomography (CBCT) to measure the maxillary sinus mucosal thickness (SM MMP) and the bone tissue height (CT MMP). Implant stability is measured by resonance frequency analysis (Osstell ISQ). These measurements are taken immediately after the procedure, then at 12, 24, and 36 months. Statistical analysis validates inter-group and temporal differences with significance set at p < 0.05.

36-month clinical and radiographic results

Analysis of data collected by cone beam computed tomography (CBCT) and resonance frequency analysis (Osstell ISQ) reveals significant differences between the two therapeutic protocols. At the end of the 36-month follow-up, the experimental group (one-stage augmentation with allogeneic bone rings and PRP) consistently outperforms the control group (two-stage protocol) across all tissue and implant stability parameters.

Comparison of tissue parameters and stability

The numerical results highlight better volume preservation and superior biological integration in the group using Maxgraft Bonering bone rings combined with PRP gel:

Parameter (at 36 months)	Study Group (n=76)	Control Group (n=48)	p-value
Sinus mucosal thickness (SM MMP)	2.83 ± 0.14 mm	4.84 ± 0.72 mm	p < 0.01
Sub-antral bone tissue height (MMP CT)	10.83 ± 0.43 mm	9.23 ± 0.46 mm	p < 0.05
Implant Stability Quotient (ISQ)	80.44 ± 0.27 units	78.51 ± 0.62 units	p < 0.05

Qualitative observations and healing kinetics

CBCT imaging and clinical follow-up identified several key points regarding the postoperative biological response:

• Mucosal stability: The study group shows a significantly more stable and physiological Schneiderian membrane thickness (2.83 mm). Conversely, the control group displays a more pronounced mucosal hypertrophy (4.84 mm), suggesting an inflammatory reaction or a less favorable remodeling compared to powder filling materials.
• Osseointegration dynamics: Overall statistical differences (p < 0.001 for temporal and inter-group variations) confirm progressive and more robust osseointegration with the bone ring technique.
• Postoperative follow-up: The authors report a reduction in postoperative edema in the main group. No major complications, such as perforation of the Schneiderian membrane, compromised the results in the one-stage protocol.

In summary, the simultaneous use of allogeneic rings and PRP not only achieves a higher final bone height (gain of 1.6 mm compared to the control), but also ensures higher primary and secondary stability, validated by ISQ values exceeding 80 units.

Clinical analysis of results

The major contribution of this study lies in the demonstration that a one-stage surgical approach using allogenic bone rings (Maxgraft Bonering) and PRP outperforms the conventional two-stage technique. Clinically, achieving an Implant Stability Quotient (ISQ) of 80.44 compared to 78.51 at 36 months confirms that the density and structural organization of the allogenic ring promote superior osseointegration. Even more striking, the stability of the sinus mucosal thickness (2.83 mm versus 4.84 mm for the control group) suggests that the combined use of solid allograft and PRP limits the reactionary mucosal hypertrophy often observed with mineralized powders, thereby reducing the risk of long-term inflammatory complications.

Study limitations and comparison

The study presents a notable numerical inconsistency in its sample size (62 patients announced for a total of 124 cases divided into n=48 and n=76), which requires caution in the interpretation of the global data. Nevertheless, the results are in favor of a drastic reduction in overall treatment time without compromising bone volume. Where the literature typically reports resorption of the powder substitute during the healing phase, the design of the allogenic ring ensures superior vertical maintenance (10.83 mm vs 9.23 mm).

Implications for practice

For the implantologist, these data validate the viability of the simultaneous sinus lift protocol with implantation, even in cases of severe atrophy, provided that a stable graft (ring) combined with growth factors (PRP) is used. This strategy does not merely simplify the patient journey; it optimizes the peri-implant biological environment by minimizing the risks of Schneiderian membrane perforation and ensuring immediate primary stability conducive to a more confident loading.

Summary of results

The study conducted on 124 sites (76 experimental, 48 control) demonstrates that a one-stage approach with allogeneic bone rings and PRP offers superior results at 36 months compared to conventional sinus lift. Patients in the experimental group show more stable mucosa (2.83±0.14 mm vs 4.84±0.72 mm, p<0.01), greater bone height (10.83 mm versus 9.23 mm), and optimized implant stability (ISQ) at 80.44 (p<0.05).

In concrete terms, for the practitioner:

• Prioritizing the one-stage procedure: The use of allogeneic bone rings (Maxgraft Bonering type) allows for predictable loading while achieving superior vertical bone gain compared to the conventional powder technique.
• Integrating PRP: The addition of platelet-rich plasma stabilises the Schneiderian membrane and reduces postoperative inflammation, limiting mucosal hypertrophy after the augmentation.
• CBCT Precision: Rigorous preoperative tomographic analysis is essential to validate the initial sinus thickness and secure the monobloc ring/implant placement.

Sinus lift remains a delicate procedure where the stability of soft and hard tissues determines long-term success. This comparative clinical study, conducted on 62 patients (aged 25 to 65 years) presenting with alveolar process atrophy, challenges conventional protocols by comparing the classic two-stage approach to an innovative simultaneous technique.

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