Evaluation of three-dimensional contraction of the volume of grafts after staged augmentation of the sinus floor, and an analysis of influential factors

Comparative Insights into Bone Substitutes for Two-Stage Maxillary Sinus Floor Elevation: A Bayesian Network Approach

To investigate the histomorphometric performance of two-stage maxillary sinus floor elevation (TMSFE) with various bone substitutes in the treatment of atrophic posterior maxilla. Four databases (PubMed, Embase, Web of Science, and The Cochrane Library) were searched from the beginning of database establishment to August 8, 2023. The included articles were limited to the English language. A systematic search was performed to identify randomized controlled trials assessing the histological performance of various biomaterials in TMSFE with a follow-up of 5-8 months. The main outcome was an area of new bone, and an additional outcome was residual graft material. Extracted data were analyzed by using a Bayesian approach (the Markov chain Monte Carlo) to establish ranks of various biomaterials in R language. Finally, the search identified 22 studies that reported 22 trials on bone area (17 kinds of biomaterials) and 12 studies on residual graft materials (12 kinds of biomaterials) after the exclusion of one study disconnected from the network plot. No local inconsistency could be found in studies regarding bone formation, while no closed loop was detected in residual graft material. The top 3 probabilities of biomaterials in terms of bone formation were Allograft + Xenograft (AG + X) (87.14%), X + Polymer (75.69%), and Autogenous Bone + Bioactive Glass (AB + BG) (71.44%). AG + X had the highest probability (87.14%) of being the most optimal treatment for bone formation. Biphasic calcium phosphate + Fibrin sealant (BCP + FS) was ranked as the slowest absorbing biomaterial (78.27%) in TMSFE. Within the limitations of the current network meta-analysis, AG + X may represent an optimal biomaterial for bone formation in TMSFE. The use of X in combination with other biomaterials demonstrates superior osteogenic effects in TMSFE. BCP + FS exhibited strong mechanical properties during a short-term observational period. The present findings suggest that AB is not the only feasible standard for bone grafts.

Biomechanical Basis for Bone Healing and Osseointegration of Implants in Sinus Grafts

A thorough comprehension of the mechanisms controlling new bone formation and implant osseointegration after maxillary sinus floor elevation is crucial for aligning our treatment choices with biological principles and enhancing clinical outcomes. The goal of bone regeneration in sinus lift procedures is to provide a sufficient amount of newly-formed tissue to support implant osseointegration. However, it is still unclear whether there is a minimum quantity of vital bone within the newly-formed tissue required for effective support, though it is generally assumed that vital bone is essential for this process. The source and integration of new bone in maxillary sinus floor elevation procedures remain debated. Most clinical studies suggest a paramount role for sinus floor and bony walls, with a centripetal pattern of new bone formation, while conflicting reports exist regarding the osteogenic role of the Schneiderian membrane. The influence of mechanical input on peri-implant bone formation, mineralization, and maturation is significant, with bone remodeling regulated by mechanical strains generated during loading. Defining optimal loading for implants, particularly in sinus lift procedures, is challenging, as early loading may damage interfacial tissue, interfering with osteogenesis. Differences in osseointegration dynamics between native and augmented bone may arise from biological and mechanical factors, but also from patient-specific factors which should be evaluated in treatment planning. Factors to consider include sinus anatomy, patient and site-specific regenerative potential, and the selection of graft material that matches the osteogenic and mechanical requirements. Tailored approaches integrating patient-specific considerations and refined implant strategies will enhance predictability and longevity of treatment.

Three-dimensional volumetric assessment and stability of simultaneously placed implant following sinus floor augmentation with deproteinized human demineralized tooth matrix or deproteinized bovine bone mineral: a randomized controlled clinical trial

PURPOSE

This study aimed to analyze and compare three-dimensional volumetric bone changes and stability of simultaneously placed dental implants following sinus augmentation using deproteinized human demineralized tooth matrix (dpDTM) and deproteinized bovine bone mineral (DBBM).

METHODS

Twenty-four patients who required lateral maxillary sinus floor augmentation with simultaneous dental implant placement were randomly assigned to receive either dpDTM (n = 12) or DBBM (n = 12). Cone-beam computed tomography and resonance frequency analysis of implant stability were conducted immediately after surgery and 6 months postoperatively. Changes in the graft sinus floor and graft height volumes in the sagittal and coronal views, along with the implant stability quotient (ISQ), were analyzed and compared.

RESULTS

Volumetric graft alteration was comparable between dpDTM (120.33 ± 77.48 mm3) and DBBM (108.51 ± 65.15 mm3) (p = 0.690). Reduction in the average graft height was also comparable: dpDTM group ranged from - 0.59 to - 0.93 mm and the DBBM group ranged from - 0.55 to - 0.82 mm (p > 0.05) at most examined levels. However, greater reduction in the mesial-graft height occurred in the dpDTM group (- 1.08 ± 0.70 mm vs. -0.58 ± 0.39 mm, p = 0.04). The ISQ values increased similarly in both groups to reach 70 at 6 months.

CONCLUSION

dpDTM demonstrated comparable stability in graft volume and height during the healing process compared to DBBM and could serve as a viable alternative to DBBM for sinus floor augmentation with simultaneous implant placement.

Deep learning-based automatic segmentation of bone graft material after maxillary sinus augmentation

OBJECTIVES

To investigate the accuracy and reliability of deep learning in automatic graft material segmentation after maxillary sinus augmentation (SA) from cone-beam computed tomography (CBCT) images.

MATERIALS AND METHODS

One hundred paired CBCT scans (a preoperative scan and a postoperative scan) were collected and randomly allocated to training (n = 82) and testing (n = 18) subsets. The ground truths of graft materials were labeled by three observers together (two experienced surgeons and a computer engineer). A deep learning model including a 3D V-Net and a 3D Attention V-Net was developed. The overall performance of the model was assessed through the testing data set. The comparative accuracy and inference time consumption of the model-driven and manual segmentation (by two surgeons with 3 years of experience in dental implant surgery) were conducted on 10 CBCT scans from the test samples.

RESULTS

The deep learning model had a Dice coefficient (Dice) of 90.36 ± 2.53%, a 95% Hausdorff distance (HD) of 1.59 ± 0.82 mm, and an average surface distance (ASD) of 0.38 ± 0.11 mm. The proposed model only needed 7.2 s, while the surgeon took 19.15 min on average to complete a segmentation task. The overall performances of the model were significantly superior to those of surgeons.

CONCLUSIONS

The proposed deep learning model yielded a more accurate and efficient performance of automatic segmentation of graft material after SA than that of the two surgeons. The proposed model could facilitate a powerful system for volumetric change evaluation, dental implant planning, and digital dentistry.

Volumetric changes and graft stability after lateral window sinus floor augmentation: A randomized clinical trial

INTRODUCTION

The present investigation compared the stability and volumetric changes of two different grafting material used for lateral window sinus floor augmentation (LWSFA).

METHODS

Sixteen patients with a total 20 maxillary sinuses in need of LWSFA were included in the present study. The sinuses were grafted with either 100% anorganic bovine bone mineral (ABBM) alone (Group 1) or a mixture (0.8:1 ratio) of ABBM and mineralized cortical allograft (MCA) (Group 2). Cone beam computer tomography (CBCT) was obtained pre-operatively, and at 2-weeks, and 6-months after LWSFA to perform linear measurements including lateral window dimensions, sinus anatomy, residual bone height/thickness (RBH/RBT), and Schneiderian membrane thickness (SMT), among others. Three-dimensional segmentation analysis was used to evaluate changes of bone graft volume/height (GV/GH).

RESULTS

A total of 10 sinuses per group were included in the analysis. No statistically significant difference was found in between groups regarding mean reduction of GV (Group 1: 14.87% ± 16.60%, Group 2: 18.06% ± 9.81%, p = 0.33). Among the linear measurements, only SMT revealed a significant increase after 2-weeks more pronounce in Group 1 (8.70 mm) when compared with Group 2 (5.70 mm) with plausible effect upon LWSFA outcomes. Sinus width showed weak positive correlation with GH reduction after 6 months.

CONCLUSION

This study demonstrated that both ABBM alone and ABBM + MCA represent suitable alternatives for LWSFA with adequate graft stability as they revealed similar volumetric and linear dimensional changes 6 months postoperatively.

Radiographic outcome after maxillary sinus floor augmentation with allogeneic adipose tissue-derived stem cells seeded on deproteinized bovine bone mineral. A randomized controlled experimental study

The objective was to test the hypothesis of no difference in radiographic outcome after maxillary sinus floor augmentation (MSFA) with allogeneic adipose tissue-derived stem cells (ASCs) seeded on deproteinized bovine bone mineral (DBBM) (test) compared with excipient on DBBM (control). Eighteen minipigs were assigned into three groups of six animals and euthanised after one month (T1), two months (T2), and four months (T3), respectively. Each maxillary sinus was randomly allocated to either test or control with an equal volume of graft. Computed tomography scans (CTs) after MSFA (T0) were compared with CTs after euthanasia to evaluate graft volume (GV) changes and bone density (BD) using three-dimensional measurements and Hounsfield units. GV was larger in test compared with control at T1 (P = 0.046), whereas GV was larger in control compared with test at T3 (P = 0.01). BD increased from T0 to T1-T3 (P < 0.001) with both treatments. Higher BD was observed in control compared with test at T3 (P = 0.01), while no significant difference was observed at T1 and T2. Conclusively, the present study demonstrate that allogeneic ASCs seeded on DBBM in conjunction with MSFA seemed not to improve the radiographic outcome compared with excipient on DBBM. However, radiological outcomes need to be supplemented by bone histomorphometry before definitive conclusions can be provided about the beneficial use of allogeneic ASCs seeded on DBBM in conjunction with MSFA compared with DBBM alone.

Influence of the contact area of the sub-antral space with sinus bone and the Schneiderian membrane on osteogenesis in lateral window sinus elevation surgery: a prospective experiment

BACKGROUND

Osteogenesis of lateral window sinus elevation surgery is the key to placement of the subsequent implant, excessive collapse of the sub-antral space may adversely affect long-term stability of implants. At present, few studies focus on the influence of the contact area of the sub-antral space on osteogenesis. This study evaluated whether the change in the contact area of the sub-antral space with maxillary sinus bone and the Schneiderian membrane can affect osteogenesis.

METHODS

Cone beam computed tomography (CBCT) images were collected of patients requiring maxillary sinus floor elevation (residual bone height < 6 mm) for standard-length implant placement before surgery, after surgery, and at 6-month follow-up visits. The postoperative sub-antral space volume (V₁) and surface area (S₁), and the remaining volume after six months of healing (V₂) were measured. Then, the contact area of sub-antral space with maxillary sinus bone (S_bc) and the Schneiderian membrane (S_mc), the absorbed volume during healing (V_a), and the percentage of remaining volume (V₂%) and absorbed volume (V_a%) were calculated. The correlation between anatomical parameters was analyzed using multiple linear regression.

RESULTS

A total of 62 maxillary sinuses from 56 patients were augmented, of which 57 were considered for the final analysis (5 withdrew due to perforation). Multiple linear regression results demonstrated that S_bc was significantly positively correlated with V_a (β coefficient = 0.141, p < 0.01) without correlation between S_mc and V_a (β coefficient =  - 0.046, p = 0.470). There was a positive correlation between S_bc and V₂% (β coefficient = 2.269, p < 0.05).

CONCLUSIONS

This study confirmed that the size of the S_bc in lateral window sinus elevation surgery affected osteogenesis after six months of healing. Clinicians should assess the sinus contour type preoperatively, then consider whether it is necessary to expand the range of the Schneiderian membrane elevation to avoid excessive collapse of the sub-antral space.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR), ChiCTR2200057924. Registered 22 March 2022-Retrospectively registered.

Radiographic and Histomorphometric Evaluation of Biomaterials Used for Lateral Sinus Augmentation: A Systematic Review on the Effect of Residual Bone Height and Vertical Graft Size on New Bone Formation and Graft Shrinkage

The aim of the present systematic review was to investigate the effect of residual bone height (RBH) and vertical bone gain on new bone formation (NBF) and graft shrinkage after lateral sinus lifts using different biomaterials.

METHODS

An electronic search was conducted on three databases to identify randomized controlled trials (RCTs) published until January 2021 with at least one follow-up at 6 months and at least five patients treated, comparing biomaterials used for maxillary sinus augmentation with a lateral approach. Graft volumetric changes, RBH, vertical bone gain, implant failure, and post-operative complications were evaluated. The risk of bias was assessed using the Cochrane tool.

RESULTS

We used 4010 identified studies, of which 21 were RCTs. Overall, 412 patients and 533 sinuses were evaluated. Only three publications had an overall low risk of bias. After 6 months, xenograft (XG) showed the least volume reduction (7.30 ± 15.49%), while autogenous graft (AU) was the most reabsorbed (41.71 ± 12.63%). NBF appeared to not be directly correlated with RBH; on the contrary, the overall linear regression analysis showed that NBF significantly decreased by 1.6% for each mm of postoperative vertical graft gain. This finding suggests that the greater the augmentation, the lower the NBF. A similar tendency, with a regression coefficient even higher than the overall one, was also observed with alloplast (AP) and XG.

CONCLUSIONS

The present results suggested that NBF was essentially independent of preoperative bone height. On the contrary, the smaller the volume was of the graft placed, the higher the amount of new bone formed, and the smaller the graft shrinkage was. Minimizing the augmentation volume might be beneficial to graft healing and stability especially when using AP and XG.

Maxillary Sinus Floor Augmentation with Autogenous Bone Graft Compared with a Composite Grafting Material or Bone Substitute Alone: a Systematic Review and Meta-Analysis Assessing Volumetric Stability of the Grafting Material

Objectives

Test the hypothesis of no difference in the volumetric stability of the grafting material following maxillary sinus floor augmentation with autogenous bone graft compared with composite grafting material or bone substitute alone applying the lateral window technique.

Material and Methods

MEDLINE (PubMed), Embase, Cochrane library and hand-search of relevant journals were conducted. Human studies published in English until the 9^th of October 2020 were included. Outcome measures included three-dimensional volumetric changes of the grafting material and potential predictive parameters. Volumetric changes were evaluated by descriptive statistics and meta-analysis including 95% confidence interval.

Results

Electronic search and hand-searching resulted in 102 entries. Four randomized controlled trials with unclear risk of bias fulfilled the inclusion criteria. The volumetric stability of the grafting material was significantly improved by mixing autogenous bone graft with a non-resorbable xenograft compared with autogenous bone graft. Meta-analyses assessing absolute and relative volumetric changes demonstrated no significant differences between autogenous bone graft compared with allogeneic bone graft, synthetic biomaterials combined with autogenous bone graft or used alone. Association between volumetric changes of the grafting material and potential predictive parameters were not assessed in the included studies.

Conclusions

Volumetric reduction of the augmented area seems inevitable following maxillary sinus floor augmentation regardless of the grafting material. The volumetric stability of autogenous bone graft is improved with addition of xenograft compared with autogenous bone graft. However, conclusions drawn from this systematic review should be interpreted with caution since only four studies using three-dimensional radiographic measurements were included.

Three-dimensional visualization of the alveolar bone and posterior superior alveolar foramen in gender

The present study applied a three-dimensional (3D) program to measure the distances from the maxillary sinus floor (MSF) to the lingual and buccal alveolar bone and also to the posterior superior alveolar foramen (PSAF), with the aim of determining differences according to gender. The study also attempted to verify the accuracy of measurements obtained from 3D images by performing comparisons with the results obtained in a preliminary study. The results showed that the alveolar bone length and the MAF-PSAF were generally larger in males than in females. It is also predicted that the accuracy of data obtained from a 3D program will be higher than that of data derived from conventional two-dimensional (2D) images. The accurate measurements obtained in this study are anticipated to prove useful in assessments related to dental implantation and anatomical structures. The fundamental data obtained in this study may also assist in setting the goals of future studies utilizing 3D programs.