Faculty Bibliography

Ameloblasts are specialized epithelial cells that form enamel during the secretory and maturation stages, the latter involving an increase in Ca²⁺ transport to mineralize the enamel crystals. During enamel formation, ameloblasts travel several microns while secreting a matrix and are surrounded by several cell layers in the confined space of the enamel organ. Presumably, ameloblasts are subjected to mechanical stimuli e.g. pressure, stretch. Mechanosensitive (MS) or stretch-gated channels are expressed in the membranes of many cells including mineralizing cells. The opening of MS channels occurs in response to physical stimuli and results in the influx of ions. Piezo1 is a non-selective class of MS channel permeable to Ca²⁺ and hence it may contribute to Ca²⁺ homeostasis in ameloblasts. Here we show that secretory and maturation stage ameloblasts express similar protein levels of Piezo1. Cultured rat primary secretory and maturation stage ameloblasts showed stretch-activated currents by patch-clamp. Ameloblasts loaded with the cytosolic Ca²⁺ indicator Fura-2 were also stimulated with the Piezo1-selective activator Yoda1. We show that ameloblasts are sensitive to Piezo1 stimulation which evoked an increase in cytosolic Ca²⁺. This effect was inhibited by Piezo1 blockers. Mechanical analysis of the incisors of Piezo1 cKO mice showed no alterations in hardness or elastic modulus relative to littermate control mice. Our work provides the first evidence that Piezo1 channels are functional in both ameloblast stages and their activation leads to an elevation in cytosolic Ca²⁺, however, Piezo1 does not appear to be essential for enamel mineralization.

Coaxial extrusion-based bioprinting (EBB) is an emerging technology that enables the fabrication of biomimetic tissues with precise structural and biological complexities. This three-dimensional bioprinting technique utilizes specialized concentric nozzles to facilitate the simultaneous extrusion of distinct biomaterials, enabling the fabrication of layered constructs that closely resemble native tissues. Unlike traditional extrusion-based methods, coaxial printing allows for independent control over core and shell materials. This enables multimaterial integration, and tailored microenvironments that conventional extrusion methods cannot achieve. Recent technical innovations in coaxial EBB also include improved nozzle designs and bioink formulations, which have contributed to enhanced functional mimicry of native tissues and mechanical integrity of printed constructs. Coaxial EBB has demonstrated potential in spinal cord injury repair, perfusable small-diameter vessel engineering, accurate tumor microenvironment replication for oncology research, and complex organoid systems for personalized medicine. Despite these advancements, persistent challenges in coaxial EBB include maintaining cell viability under shear stress, optimizing bioink rheology, preventing nozzle clogging, and managing regulatory considerations. Future research directions involve the development of predictive computational models and the incorporation of innovative biomaterials for dynamic functionality. Addressing these challenges would allow the full therapeutic and clinical potential of coaxial bioprinting in regenerative medicine to be achieved. This review discusses and summarizes these advancements and limitations in coaxial EBB over the last decade, with an emphasis on applications in regenerative medicine.

Current evidence suggests that achieving the desired level of osseointegration necessitates a hierarchical approach to implant design. This is particularly relevant for osseointegration around implant systems such as those presenting vertical decompression chambers and acid-etched surfaces which could further be augmented by non-thermal plasma (NTP) treatment. Three implant systems were compared in this study: (i) ND (GM Helix Acqua Implant; Neodent^®, Curitiba, PR, Brazil-hybrid, acid-etched thread design treated with isotonic sodium chloride solution), (ii) Sin (Epikut Plus; S.I.N. Implant System, São Paulo, Brazil-V-shaped, acid-etched thread design treated with nano-hydroxyapatite), and (iii) Mp (Maestro; Implacil De Bortoli, São Paulo, Brazil-buttress, acid-etched thread design with decompressing vertical chambers). The ND and Sin implants were used directly as supplied by the manufacturer. For the Mp implants, the manufacturer-supplied surface was subjected to supplemental acid etching with 37% hydrochloric acid followed by Argon-based NTP treatment administered with a pulsed plasma generator prior to implantation into the iliac crest of n = 12 adult female sheep. Histomorphometric analysis was conducted at 3- and 12-week post-implantation (n = 6 sheep per time point) to assess bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). After 3 weeks in vivo, the healing chambers of all implant groups consisted predominantly of newly forming woven bone. By 12 weeks, bone maturation was observed, with the presence of remodeling sites and some areas of well-organized lamellar structures occupying the healing chambers. At both 3 and 12 weeks, the Mp implants demonstrated significantly higher BAFO values relative to ND (p = 0.015 and p = 0.008, respectively). The combination of vertical healing chambers, acid etching, and NTP treatment promoted early vascular infiltration and sustained bone deposition.

To evaluate the effect of graded glass infiltration on the fatigue behavior and mechanical reliability of translucent 4Y-PSZ zirconia before and after hydrothermal aging, disc-shaped specimens were fabricated by uniaxial pressing and divided into control and glass-graded groups (n = 36/group). Glass infiltration was performed on pre-sintered specimens followed by final sintering, and half of the specimens from each group underwent hydrothermal aging (134°C, 2.2 bar, 20 h). Microstructure and phase composition were assessed by scanning electron microscopy and x-ray diffraction. Mechanical performance was evaluated using step-stress accelerated life testing, with Weibull statistics, reliability analysis, and inverse power-law modeling. Glass-graded specimens demonstrated higher reliability and characteristic strength (≈330 MPa increase) with similar Weibull modulus compared to controls. The inverse power-law parameter α₀ was higher for the glass-graded group, indicating extended fatigue life, whereas comparable α₁ values suggested similar life-stress relationships. Hydrothermal aging did not significantly affect mechanical performance, although phase transformation occurred in the control group. Fractography revealed surface-initiated failures in controls and interface-related crack initiation in glass-graded specimens. Graded glass infiltration improved the fatigue reliability and characteristic strength without compromising hydrothermal stability of 4Y-PSZ. These results suggest that glass-graded 4Y-PSZ may expand the clinical applicability of translucent zirconia for long-span (≥4-unit) prosthetic reconstructions.

INTRODUCTION/BACKGROUND:Press-fit acetabular components achieve long-term fixation through osseointegration, yet the extent of bone ingrowth necessary for durable stability in well-functioning implants remains unclear. Postmortem retrievals provide a unique opportunity to directly assess the bone-cup interface in clinically successful total hip arthroplasties (THAs). This study evaluated osseointegration and biomechanical fixation strength in deceased-donor acetabular components to better define the characteristics of stable long-term fixation. METHODS:Cadaver pelvis specimens containing uncemented THAs from a single institution were evaluated. There were 29 acetabular components that underwent axial pull-out testing using a universal testing machine. A total of seven of these were additionally processed for histologic evaluation, including dehydration, acrylic embedding, thin-sectioning, staining, and digital imaging. Osseointegration was quantified by bone-area fraction occupancy (%BAFO), representing the proportion of bone occupying the porous thread spaces of the cup. RESULTS:All 29 specimens failed through fracture of the ilium rather than at the bone-cup interface, indicating that the mechanical integrity of the osseointegrated construct exceeded that of the surrounding bone under axial tension. Among the seven histologically analyzed components, %BAFO ranged from 4.2 to 27.0% (mean 15.1%), despite all implants being clinically stable at the time of death. There were no significant linear correlations observed between %BAFO and time implanted, fracture load, or body mass index. A significant quadratic relationship between %BAFO and age was identified, peaking near 81 years. CONCLUSIONS:Cementless acetabular components exhibited strong fixation despite modest osseointegration, with failure occurring through host bone on axial testing. Durable biological fixation appears achievable with limited, but mechanically favorable bone ingrowth.

BACKGROUND AND OBJECTIVE/UNASSIGNED:Personalized medicine tailors interventions to a patient's unique anatomy and physiology. Three-dimensional printing (3DP) enables this precision for complex airway disease, including tracheal stenosis, tracheobronchomalacia, aerodigestive fistulas, and segmental defects, where conventional silicone or metallic stents and surgical reconstruction often fail to provide durable, anatomically congruent solutions. Tissue engineering and 3DP promise patient-specific devices and regenerative scaffolds that maintain patency, resist collapse, and minimize immunogenicity. This review synthesizes clinical and preclinical progress, highlighting materials, design strategies, biologic integration, and translational barriers. METHODS/UNASSIGNED:implantation. Pediatric (<18 years), egg/mouse/rat preclinical studies, review articles, and abstracts were excluded. Data extracted included publication details, participant characteristics, device materials and printing methods, and outcomes. KEY CONTENT AND FINDINGS/UNASSIGNED:From 808 records, 16 clinical and 56 preclinical studies were analyzed. Clinically, indirect 3DP with silicone or metallic alloys predominated, creating Y-stents or straight stents for post-lung transplant (LTx) stenosis, tracheobronchomalacia, granulomatosis with polyangiitis, malignant obstruction, and aerodigestive fistulas. 3DP technologies facilitate the synthesis of customized stents that can better conform to individual airway geometries, offering more precise therapeutic options than conventional one-size-fits-all devices. In parallel, preclinical studies aim to address the limitations observed within clinical settings by focusing on long-term, regenerative solutions. Preclinical studies focused on biodegradable scaffolds, commonly polycaprolactone (PCL), enhanced through surface modification or hybridization with hydrogels such as gelatin methacryloyl (GelMA) or silk fibroin and bioactive factors like transforming growth factor-β (TGF-β) or stromal cell-derived factor-1 (SDF-1). Bilayer constructs with epithelial and chondrogenic components supported epithelialization, cartilage formation, and vascularization. Advanced strategies such as exosome use, ferroptosis inhibition, and heterotopic preconditioning improved integration. CONCLUSIONS/UNASSIGNED:3DP enables anatomically tailored airway implants and promising regenerative scaffolds. Translation is limited by technical variability, regulatory complexity, and sparse long-term data. Standardized protocols, rigorous trials, and multidisciplinary collaboration are essential to bring 3DP airway reconstruction into clinical practice.

Soft tissue augmentation in the oral cavity is limited by mechanical loading, salivary enzymes, and rapid degradation of collagen-based biomaterials. Porcine-derived collagen membranes (PDCMs) may provide an alternative to autografts, but their clinical performance is influenced by membrane architecture, crosslinking, and the surgical environment. This study evaluated the long-term biocompatibility, degradation behavior, and soft tissue healing outcomes of two novel crosslinked PDCMs compared with an established noncrosslinked bilayer membrane in a canine mandibular defect model. Standardized full-thickness mandibular soft tissue defects were created in n=24 beagles and treated with a bilayer PDCM with high crosslinking (HXL), a bilayer PDCM with low crosslinking (LXL), or a predicate bilayer membrane (Mucograft, MG). Untreated defects served as controls. Animals were euthanized at 4, 8, and 12 weeks. Qualitative and semiquantitative analyses assessed membrane presence, inflammation, and subepithelial healing, while membrane thickness was quantified across timepoints. All membranes supported successful healing with decreasing inflammation over time. At 4 weeks, MG demonstrated greater membrane thickness (p = 0.023) and inflammation (p = 0.004) than LXL. At 8 weeks, both HXL and LXL showed reduced membrane presence relative to MG (p = 0.001), and this difference persisted at 12 weeks (p = 0.018). At 12 weeks, LXL achieved superior subepithelial healing compared with MG (p = 0.047), with more organized collagen and improved integration. Overall, LXL provided a favorable balance of stability, integration, and biocompatibility, supporting coordinated soft tissue remodeling.

Rhinoplasty is the fifth most commonly performed cosmetic surgery globally. While surgical techniques used for rhinoplasty have evolved significantly in the past century, the creation of precise osteotomies remains a cornerstone of the procedure. Recently, piezotomes have been associated with reduced postoperative pain, edema, ecchymosis, complications, and revision rates in rhinoplasty. Despite these clinically significant benefits, there remains a paucity of histologic analysis of osteotomies performed with piezotomes in a large translational preclinical model. In this study, n=12 adult sheep underwent lateral rhinoplasty of the posterior maxilla using each of the three surgical devices: piezotome, manual osteotome, and oscillatory saw. Subjects were randomized to heal for either 3 or 12 weeks postoperatively (n = 6 animals per cohort). En bloc samples were processed and analyzed histologically. A semiquantitative healing scale was used to quantify bony ingrowth into the osteotomy. Wilcoxon signed-rank tests were used to analyze the outcome variable. No statistically significant differences in semiquantitative grades were observed among groups (p > 0.05) at either time point. However, the piezotome was associated with more uniform, reproducible, and smoother osteotomy walls, and smaller bone chips at 3 weeks. At 12 weeks, all osteotomy techniques had complete or near-complete osteogenesis. Use of the piezotome did not completely prevent soft tissue injury. Some osteotomies demonstrated full-thickness penetration and injury to the underlying cartilage. All groups demonstrated comparable healing outcomes after 12 weeks. However, histologic results indicate that reliance solely on device technology may not be sufficient. Clinical judgement of these techniques and relevant case presentations is required to minimize unintended tissue injury.

Critically sized bone defects are difficult to treat, necessitating tissue engineering strategies to restore form and function. However, translation of these approaches is often constrained by preclinical models that fail to replicate systemic comorbidities commonly seen in clinical practice, such as diabetes, prior irradiation, osteonecrosis, and osteoporosis, and instead favor healthy wound environments that may overestimate efficacy. This comprehensive review aimed to provide a detailed overview of in vivo bone regeneration strategies for critically sized defects specifically within compromised healing environments, summarizing how animal models are developed and how biomaterial, cellular, and drug delivery platforms are tailored to these disease states. Recent work has sought to address key pathological barriers including chronic inflammation, oxidative stress, poor vascularization, hypocellularity, and the limited efficacy of cell-seeding approaches through a range of bioengineered solutions. Strategies include nanoengineered drug delivery systems, bioactive ion-releasing scaffolds, immunomodulatory and antioxidant biomaterials, advanced cell provisioning, and extracellular vesicle-based therapies designed to restore redox balance, promote angiogenesis, and reestablish osteogenesis. Remaining challenges include heterogeneity and poor standardization of defect models, underrepresentation of multimorbidity and treatment-related injury, ethical and logistical barriers to large animal studies, and uncertainty in how best to bridge emerging platforms with regulatory expectations. Future directions will require coordinated refinement of disease-relevant models and development of multifunctional, context-responsive constructs to more reliably predict and improve clinical translation of bone tissue engineering therapies.

OBJECTIVES/OBJECTIVE:To evaluate the reliability and failure modes of 3D-printed crowns fabricated from different resin composites compared to a milled resin composite block, all indicated as definitive restorations. METHODS:Four 3D-printing resins were evaluated: 1) CeramicCrown (CC; SprintRay), 2)VarseoSmile-Crown (VSC, Bego), 3) Crowntec (CRO, Saremco), and 4) Ceramage 3D-Printed (C3D, Shofu), along a milled resin-composite block: Shofu Block HC Super-Hard (SSH, Shofu). Eighteen implant-supported maxillary first-molar crowns were manufactured per group and tested under step-stress accelerated life testing. Weibull statistics were applied, and reliability was calculated for 100,000 cycles at different loads. Fractographic analysis was performed under scanning electron microscopy. RESULTS:All 3D-printed samples failed during fatigue testing, whereas SSH samples survived both the initial protocol and the extended cycling, in which the load profiles were modified to increase the number of cycles (up to 2400,000). Failures were related to material strength (C3D, CC, VSC) or fatigue damage accumulation (CRO). At a mission of 100,000 cycles at 300 N, all 3D printed groups presented high reliability (>99 %). Under higher loads (800-1000 N), CRO and VSC had lower reliability compared to C3D and CC. Characteristic fracture load was highest for C3D and CC, intermediate for CRO, and lowest for VSC. CRO showed the lowest Weibull modulus. Fractographic analysis indicated fracture initiation at the occlusal surface in printed crowns, propagating toward the margins and abutment. SSH crowns exhibited wear marks with no crack formation. SIGNIFICANCE/CONCLUSIONS:While the milled composite demonstrated superior fatigue resistance, 3D-printed definitive crowns exhibited material-dependent fatigue behavior. Among printed groups, CC and C3D presented higher characteristic fracture load and reliability under higher loads compared to CRO and VSC.