Stefan Tangl

Background/Objectives: Immediate implant placement in sites with prolonged ligature-induced periodontal disease during antiresorptive therapy is poorly modeled. This study investigated whether zoledronic acid (ZA) could preserve peri-implant bone sufficiently to support osseointegration in a rat challenge model. Methods: Thirty-two adult male Wistar rats received saline (SAL) or ZA (ZOL). Ligature-induced periodontitis was maintained for seven weeks around the mandibular first molar, followed by extraction and immediate placement of a commercially pure titanium implant. Animals were euthanized after 28 days. Removal torque (RTQ), SEM-EDX, and micro-computed tomography were assessed alongside undecalcified histology, which underwent qualitative evaluation and blinded exploratory semiquantitative scoring. Results: Median RTQ and peri-implant bone volume fraction (BV/TV) were numerically higher in ZOL than SAL animals (RTQ: 4.0 vs. 2.5 N·cm, p = 0.104; BV/TV: 46.5% vs. 28.0%, p = 0.113), but neither difference reached statistical significance. Histology showed near-complete absence of new bone–implant contact, with median scores of 0 in both groups. Compared with SAL, ZOL specimens showed descriptively greater retention of alveolar architecture, while 4 of 8 specimens had no detectable viable bone in the assessed peri-implant region. Epithelial coverage scores were lower in ZOL than in SAL (median: 0 vs. 2; nominal p = 0.027). Conclusions: Under the combined experimental conditions, retention of peri-implant mineralized tissue did not correspond to meaningful regenerative osseointegration. The findings distinguish bone quantity and mechanical anchorage from direct biological integration and should not be extrapolated directly to routine clinical implant therapy.

Background: The lateral angle of the internal acoustic meatus of the petrous bone is a sexually dimorphic feature used for sex determination, particularly in fragmented or cremated remains. However, studies show conflicting results regarding its accuracy, and the reasons for its dimorphism remain unclear. The aim of this study is to analyze sexual dimorphism in subadult individuals and to examine the association of the lateral angle with cranial breadth as an explanation for its sexual dimorphism, as well as interpopulation differences. Methods: We measured the lateral angle and biauricular breadth in 204 individuals (birth to 30 years) using CT scans from Austrian 19th-century anatomical collections and data from the New Mexico Decedent Image Database. Results: This study revealed that the sexual dimorphism of the lateral angle and cranial dimensions manifests during puberty, along with a strong association between the lateral angle and the biauricular breadth. Additionally, this study noted interpopulation variability in cranial breadth, with different levels of sexual dimorphism observed across diverse populations. Conclusions: The findings offer a potential explanation for the observed variability in lateral angle measurements across studies and the limitations of universal cut-off points as a sex-determination method in osteology.

Background: The lateral angle of the internal acoustic meatus of the petrous bone is a sexually dimorphic feature used for sex determination, particularly in fragmented or cremated remains. However, studies show conflicting results regarding its accuracy, and the reasons for its dimorphism remain unclear. The aim of this study is to analyze sexual dimorphism in subadult individuals and to examine the association of the lateral angle with cranial breadth as an explanation for its sexual dimorphism, as well as interpopulation differences. Methods: We measured the lateral angle and biauricular breadth in 204 individuals (birth to 30 years) using CT scans from Austrian 19th-century anatomical collections and data of the New Mexico Decedent Image Database. Results: The study revealed that the sexual dimorphism of the lateral angle and cranial dimensions will manifest during puberty, along with a strong association between the lateral angle and the biauricular breadth. Additionally, the study noted inter-population variability in cranial breadth, with different levels of sexual dimorphism observed across diverse populations. Conclusion: The findings offer a potential explanation for the observed variability in lateral angle measurements across studies and the limitations of universal cutoff points as a sex determination method in osteology.

Platelet-rich fibrin, the coagulated plasma fraction of blood, is commonly used to support natural healing in clinical applications. The rat calvaria defect is a standardized model to study bone regeneration. It remains, however, unclear if the rat calvaria defect is appropriate to investigate the impact of human PRF (Platelet-Rich Fibrin) on bone regeneration. To this end, we soaked Bio-Gide^® collagen membranes in human or rat liquid concentrated PRF before placing them onto 5 mm calvarial defects in Sprague Dawley rats. Three weeks later, histology and micro-computed tomography (μCT) were performed. We observed that the collagen membranes soaked with rat PRF show the characteristic features of new bone and areas of mineralized collagen matrix, indicated by a median mineralized volume of 1.5 mm³ (range: 0.9; 5.3 mm³). Histology revealed new bone growing underneath the membrane and hybrid bone where collagen fibers are embedded in the new bone. Moreover, areas of passive mineralization were observed. The collagen membranes soaked with human PRF, however, were devoid of histological features of new bone formation in the center of the defect; only occasionally, new bone formed at the defect margins. Human PRF (h-PRF) caused a median bone volume of 0.9 mm³ (range: 0.3–3.3 mm³), which was significantly lower than what was observed with rat PRF (r-PRF), with a BV median of 1.2 mm³ (range: 0.3–5.9 mm³). Our findings indicate that the rat calvaria defect model is suitable for assessing the effects of rat PRF on bone formation, but caution is warranted when extrapolating conclusions regarding the efficacy of human PRF.

Bio-Gide^® is a collagen membrane routinely used in guided bone regeneration. Recent studies have shown that this collagen membrane has osteoconductive properties, meaning that it can support the growth of new bone. However, it has also been observed that the collagen membrane has areas of mineralized fibers which can occur spontaneously and independently of osteoblasts. To better understand how this works, we established a model using minced collagen membranes to reduce the active mineralization of intact collagen membranes in favor of passive mineralization. We thus compared the original intact membrane with a minced collagen membrane in a 5 mm calvarial defect model in Sprague Dawley rats. After three weeks of healing, histology and microcomputed tomography (μCT) were performed. Histological analysis confirmed the osteoconductive properties, with new bone growing inside the intact collagen membrane. However, in minced collagen membranes, the osteoconductive properties were restricted to the defect margins. Interestingly, histology revealed large mineralized areas indicating passive mineralization with no signs of bone formation. In the μCT analysis, the intact collagen membranes caused a higher median mineralized volume (1.5 mm³) compared with the minced group (0.4 mm³), but this lacked significance (p = 0.09). The μCT analysis needs to be interpreted carefully, particularly in defects filled with minced membranes, considering that the mineralized tissue may not necessarily be bone but also the result of passive mineralization. Taken together, the findings suggest that Bio-Gide^® collagen membranes support bone formation while also exhibiting potential for passive mineralization.

Objectives: Autologous bone is considered the gold standard for grafting, yet it suffers from a tendency to undergo resorption over time. While the exact mechanisms of this resorption remain elusive, osteocytes have been shown to play an important role in stimulating osteoclastic activity through their expression of receptor activator of NF-kappa B (RANK) ligand (RANKL). The aim of this study was to assess the function of osteocyte-derived RANKL in bone graft remodeling.Materials and Methods: In Tnfsf11fl/fl;Dmp1-Cre mice without osteocyte-specific RANKL as well as in Dmp1-Cre control mice, 2.6 mm calvarial bone disks were harvested and transplanted into mice with matching genetic backgrounds either subcutaneously or subperiosteally, creating 4 groups in total. Histology and micro-computed tomography of the grafts and the donor regions were performed 28 days after grafting.Results: Histology revealed marked resorption of subcutaneous control Dmp1-Cre grafts and new bone formation around subperiosteal Dmp1-Cre grafts. In contrast, Tnfsf11fl/fl;Dmp1-Cre grafts showed effectively neither signs of bone resorption nor formation. Quantitative micro-computed tomography revealed a significant difference in residual graft area between subcutaneous and subperiosteal Dmp1-Cre grafts (p < .01). This difference was not observed between subcutaneous and subperiosteal Tnfsf11fl/fl;Dmp1-Cre grafts (p = .17). Residual graft volume (p = .08) and thickness (p = .13) did not differ significantly among the groups. Donor area regeneration was comparable between Tnfsf11fl/fl;Dmp1-Cre and Dmp1-Cre mice and restricted to the defect margins.Conclusions: The results suggest an active function of osteocyte-derived RANKL in bone graft remodeling.

Functionalizing biomaterials with conditioned media (CM) from mesenchymal stromal cells (MSC) is a promising strategy for enhancing the outcomes of guided bone regeneration (GBR). This study aimed to evaluate the bone regenerative potential of collagen membranes (MEM) functionalized with CM from human bone marrow MSC (MEM-CM) in critical size rat calvarial defects. MEM-CM prepared via soaking (CM-SOAK) or soaking followed by lyophilization (CM-LYO) were applied to critical size rat calvarial defects. Control treatments included native MEM, MEM with rat MSC (CEL) and no treatment. New bone formation was analyzed via micro-CT (2 and 4 weeks) and histology (4 weeks). Greater radiographic new bone formation occurred at 2 weeks in the CM-LYO group vs. all other groups. After 4 weeks, only the CM-LYO group was superior to the untreated control group, whereas the CM-SOAK, CEL and native MEM groups were similar. Histologically, the regenerated tissues showed a combination of regular new bone and hybrid new bone, which formed within the membrane compartment and was characterized by the incorporation of mineralized MEM fibers. Areas of new bone formation and MEM mineralization were greatest in the CM-LYO group. Proteomic analysis of lyophilized CM revealed the enrichment of several proteins and biological processes related to bone formation. In summary, lyophilized MEM-CM enhanced new bone formation in rat calvarial defects, thus representing a novel ‘off-the-shelf’ strategy for GBR.

A static magnetic field generated by neodymium–iron–boron (NdFeB) magnets placed in the inner cavity of dental implants can enhance bone regeneration in rabbits. It is, however, unknown whether static magnetic fields support osseointegration in a canine model. We therefore determined the potential osteogenic effect of implants carrying NdFeB magnets inserted in the tibia of six adult canines in the early stages of osseointegration. Here, we report that after 15 days of healing, magnetic and regular implants showed a high variation with a median new bone-to-implant contact (nBIC) in the cortical (41.3% and 7.3%) and the medullary (28.6% and 44.8%) region, respectively. Consistently, the median new bone volume/tissue volume (nBV/TV) in the cortical (14.9% and 5.4%) and the medullary (22.2% and 22.4%) region were not significantly different. One week of healing only resulted in negligible bone formation. These findings suggest that considering the large variation and the pilot nature of this study, magnetic implants failed to support peri-implant bone formation in a canine model.

Research in maxillary sinus floor augmentation (MSFA) focussed on the optimisation of microstructural parameters such as microporosity and particle size of bone substitute particles (BS). However, little is known about the impact of BS packing and the corresponding (void) interparticular space on bone regeneration. The aim of this study was to characterise the spatial distribution of BS and its association with BS integration 6 ± 1 months after MSFA. Histological thin-ground sections of 70 human sinus biopsies were histomorphometrically analysed: In serial zones of 100 µm proceeding from the sinus floor (SF) up to the apical end of the biopsy, we measured the distribution of BS particles within these zones in terms of volume (BSV/TV), number and size of BS particles, interparticle spacing (BS.Sp) and bone-to-BS contact. BS particles were not homogeneously distributed over the length of biopsies: The first 200 µm directly adjacent to the SF represented a zone poor in BS particles but with high osteogenic potential. Graft packing density increased from the SF towards the apical part of the AA. Integration of BS particles was inversely associated with the distance to the SF and the graft packing density. A high packing density through excessive compaction of BS particles should be avoided to optimise the macrostructural environment for bone regeneration.