Introduction: The fracturing of abutment screws is a recurrent technical complication in implant-supported prostheses that may compromise prosthetic maintenance. Although multiple retrieval approaches have been described, comparative data under controlled experimental conditions remain limited. Materials and Methods: This in vitro pilot study evaluated the retrievability of fractured abutment screws when using three commonly applied instruments: an ultrasonic scaler, a fissure bur, and a screw removal kit. Eighteen implants from a single implant system were embedded in epoxy resin, and abutment screws were fractured under clockwise monotonic torque either with (w/A) or without (w/oA) abutments (n= 3 per retrieval method). Retrieval success and procedure time were recorded. Scanning electron microscopy (SEM) was performed to qualitatively assess deformation of the implant internal hex and screw thread morphology. Results: Fracture torque values were higher in specimens fractured with abutments compared with those without abutments. Fractures induced without abutments appeared to extend deeper within the screw channel, engaging a greater number of internal threads. In this pilot study, a shorter retrieval time was observed with the screw removal kit and fissure bur compared with the ultrasonic scaler, although retrieval outcomes varied between specimens. SEM observations suggested differing patterns of internal hex deformation between the retrieval techniques. Conclusions: Within the limitations of this in vitro pilot study, different retrieval approaches demonstrated characteristic mechanical behaviors and deformation patterns in the implant internal connection. These preliminary findings provide descriptive insight into the retrievability of fractured screws and may serve as a basis for future studies with larger sample sizes and clinically relevant fracture models.
To address the issues of displacement and insufficient positional stability observed in the clinical use of the PROPEL Mini stent, this study investigates the influence of different biodegradable materials on the mechanical properties of the stent under the constraint of a fixed monofilament braided closed-loop geometry. Finite element analyses are conducted using Abaqus/Explicit to quantitatively evaluate the nonlinear mapping between nominal diameter, axial length, and radial pressure throughout a loading-unloading cycle. The results reveal that while axial behavior is consistent during compression, material-specific plasticity causes irreversible geometric sets in Mg alloy and PLGA models, whereas the PCL stent achieves total elastic recovery to its initial dimensions. During unloading, the Mg alloy stent recovers to a nominal diameter of 28 mm with a reduced axial length of approximately 22 mm, whereas the PLGA stent exhibits a much smaller recovery diameter of 14 mm with an axial length of approximately 23 mm. These post-release configurations directly determine the functional expansion range of the biodegradable stents after implantation. During unloading, the Mg alloy stent provides the highest radial pressure (peak 6.8 kPa) with a functional recovery range up to 26.5 mm, ensuring superior scaffolding stability. In contrast, while PCL achieves the widest recovery (52 mm), its radial pressure is clinically negligible (the maximum value is still less than 165 Pa), and the PLGA model exhibits both insufficient support and a restricted functional recovery limit (13 mm). By using high-strength materials such as Mg alloys, the radial anchoring force of the stent can be effectively enhanced without changing the existing structure, providing a scientific basis for solving clinical displacement problems.
Introduction: The outcome of endodontic microsurgery depends on the integrity of the apical seal and the adaptation of root-end filling materials under functional stresses. The study aims to compare the void volumes and distribution of ProRoot MTA, ERRM, and ERRM combined with Bioceramic sealer under simulated functional loading using micro-computed tomography (micro-CT).
Methods: Forty-four single-rooted mandibular premolars were prepared with 3 mm apical cavities and divided into four groups (n = 11 each): Cavit (Control), ProRoot MTA, ERRM Putty, and ERRM + BC Sealer. Samples were scanned by micro-CT to quantify internal, marginal, and total voids. Each specimen was then subjected to cyclic vertical loading of 20 N for 1,000,000 cycles in a chewing simulator, followed by post-scanning. Pre- and post-loading void volumes and distribution were analyzed and compared statistically (α = 0.05).
Results: Functional loading significantly increased void volumes in all groups (p < 0.05). Control and MTA showed the highest total and marginal voids (p < 0.05), while ERRM and ERRM + BC maintained significantly lower overall and marginal voids. No difference was detected between ERRM and ERRM + BC (p > 0.05). ERRM and ERRM + BC Sealer showed relatively lower marginal-to-internal voids ratios compared to MTA. Material dislodgement occurred only in Cavit and MTA.
Conclusions: ERRM and ERRM + BC sealer groups exhibited favorable marginal adaptation and significantly lower overall void volumes after low-load functional loading compared to MTA and the control. The findings indicate preserved sealing performance and suggest resistance to void formation under simulated occlusal stresses.
Objective: This retrospective study was conducted to evaluate long-term outcomes lcomplication rates of crown restorations supported by different types of endodontic posts and to determine the influence of post material on biological and technical outcomes. Materials and Methods: Clinical and radiographic data from 437 crowned teeth retained by fiber, metallic, or custom-made posts were collected at Qassim University Dental Hospital between August and November 2025. Biological (secondary caries, periapical lesions) and technical (debonding, fracture, chipping) complications were recorded. Kaplan-Meier and life-table analyses were used to estimate complication-free survival, and Cox regression was employed to identify significant predictors (α = 0.05). Results: The mean observation period was 6.76 ± 4.88 years. The overall complication rate was 56.8%. Crowns restored with fiber posts exhibited the lowest complication rate (40.0%) and the highest 15-year cumulative survival (52%), followed by custom-made (38%) and metallic posts (15%). Fiber posts demonstrated a significantly lower hazard of complications than metal posts (HR = 1.70, p = 0.009). Female sex (HR = 1.69, p = 0.001) and mandibular location (HR = 1.36, p = 0.048) were associated with increased risk. Metal-ceramic crowns showed a protective effect compared to ceramic crowns (HR = 0.56, p = 0.001). Conclusions: The type of post significantly affected long-term prognosis of crowned endodontically treated teeth. Fiber posts provided the most favorable outcomes by minimizing catastrophic root fractures, while metallic and custom-made posts demonstrated higher complication hazards. Crown material, arch location, and patient factors further influenced survival outcomes.
As cancer mortality rates rise globally, malignancies have become the second leading cause of death. Recently, efforts have been made to understand the impact of the tumor microenvironment that involves fluid shear forces. Biomechanical stimulation, which uses shear stress to activate mechanosensitive ion channels, e.g., Piezo1, increases calcium influx into the intracellular space and activates T cells. Novel 3D cancer cultures with T cells have been proposed. Such models use cell/scaffold constructs to recapitulate interactions between cells and the extracellular matrix. In addition, flow perfusion bioreactors investigate the impact of fluid shear forces on immune and/or cancer cells. These bioreactors have biosensors that allow monitoring of immune cell activation. Furthermore, they provide a biomimetic environment for the study of the interaction of T cells and cancer cells. Hence, immune checkpoint inhibitors have demonstrated immunotherapeutic efficacy, but a single-target blockade has often proved insufficient. Co-delivery of CCL19 pDNA and the PD-1/PD-L1 interaction inhibitor BMS-1 using RGD-modified nanocarriers targeting tumor integrins enhanced local antitumor immunity. This review highlights recent insights into how fluid shear stress (FSS) regulates cancer progression and immune responses in three-dimensional in vitro models, with a focus on bioreactors and the surface modification of scaffold materials.
Physicochemical modification of titanium implants aims to enhance early osseointegration by improving bioactivity. This study deposited and evaluated an anatase TiO2 film on clinically relevant sandblasted, acid-etched titanium (Ti-SLA) to enhance in vitro bioactivity and osteogenic responses. An ~8 µm TiO2-anatase coating was deposited on Ti-SLA by reactive pulsed DC magnetron sputtering. Surface characterization included FE-SEM, helium ion microscopy, and XRD. Wettability and surface free energy (SFE) were evaluated by contact angle analysis. In vitro bioactivity was assessed by hydroxyapatite (HA) formation in twofold-concentrated simulated body fluid (2× SBF). Osteoblast responses were evaluated through cell adhesion, viability, alkaline phosphatase activity, gene expression, and mineralization. The coating produced hierarchical multi-globular microstructures decorated with faceted anatase nanocrystals. Ti-SLA's initial hydrophobicity converted to a superhydrophilic, high-energy surface with increased polar SFE. Homogeneous HA crystallites deposited exclusively on SLA-anatase in 2× SBF. SAOS-2 cells showed enhanced metabolic activity, ALP activity, osteogenic gene upregulation, and improved mineralized matrix, while primary human osteoblasts exhibited increased metabolic activity and calcium deposition. The anatase coating produced a superhydrophilic, high-energy micro-nano surface that accelerates HA formation and enhances osteoblast function in vitro, warranting in vivo validation for early osseointegration.
Over the past decade, endodontic biomaterials have shifted from being passive fillers to bioactive systems that can support repair and regeneration through validated physicochemical and biological mechanisms [...].
Ex vivo human tooth culture models preserve the native dentine-pulp complex and offer a translational platform to study pulp-capping biomaterials. This systematic review aimed to synthesize the evidence on histological pulp tissue responses to calcium silicate-based cement (CSCs) used for direct pulp capping in human tooth culture models. The review followed PRISMA 2020 guidance. Eligible studies were ex vivo whole human tooth culture models with direct pulp exposure treated with commercial or experimental CSCs and reporting histological outcomes. Risk of bias was assessed using the QUIN tool. Thirteen studies were included. Most used immature human third molars (from 15- to 19-year-old patients) and culture periods up to 28 days, with a minority extending observation to 45-90 days. Across hydraulic CSCs, Biodentine was the most frequently evaluated material, followed by ProRoot MTA and several experimental hydraulic and resin-modified formulations. Overall, hydraulic CSCs were consistently associated with biocompatible pulp responses and a pro-mineralization pattern characterized by periexposure mineralized foci/osteodentin-like tissue; where assessed, immunohistochemistry supported odontoblast-like differentiation. In contrast, the resin-modified CSC TheraCal LC and other experimental resin-modified CSCs showed more heterogeneous findings, with reports of absent, delayed, or less prominent mineralization compared with reference hydraulic CSCs. In intact human tooth culture models, hydraulic CSCs show reproducible biocompatibility and early mineralization features consistent with reparative dentinogenesis, whereas resin-modified CSCs demonstrate more variable histological performance.
Background: Autogenous tooth-derived grafts have been proposed as an alternative to xenografts for alveolar ridge preservation, offering biological similarity to bone and potentially more favorable remodeling. This study compared the healing outcomes of a collagenated xenograft, and a tooth-derived graft prepared with an automated processing device.
Methods: Six Beagle dogs underwent bilateral extraction of the third and fourth mandibular premolars. Each animal contributed two sockets grafted with root-derived particulate prepared using an automated device for tooth cleaning, grinding, and demineralization, and two sockets grafted with a collagenated xenograft, all covered by a collagen membrane. After 3 months, histological sections were analyzed to assess crestal dimensions and the relative proportions of mature (lamellar) and immature bone (woven/parallel fibered), residual graft material, and soft tissues.
Results: Lingual crest height did not differ between groups, whereas the buccal crest was slightly higher at xenograft sites compared with the tooth-graft sites. The tooth-graft group exhibited significantly fewer residual particles (0.5 ± 1.1%) and a higher proportion of total bone (65.6 ± 9.1%) compared with the xenograft group, which showed 19.7 ± 16.0% graft remnants (p = 0.032). Corticalization at the socket entrance was observed predominantly in the tooth-graft sites. No inflammatory infiltrates were detected in the examined section.
Conclusions: Tooth-derived grafts promoted an almost complete replacement by vital bone with minimal residual material, whereas xenografts provided slightly better buccal contour preservation but resulted in regenerated tissues containing persistent graft particles. The biological differences observed may have implications for subsequent implant placement.
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