Faculty Bibliography

Atsttrin, a therapeutic derivative of progranulin, promotes tissue repair via TNFR2-mediated anti-inflammatory and regenerative signaling. Our group developed an injectable, thermoresponsive graphene oxide-polyethylene glycol/collagen type I hydrogel for sustained and localized delivery of Atsttrin and systematically evaluated its therapeutic efficacy in vitro and in vivo models. The hydrogel demonstrated favorable rheological properties, controlled degradation, high porosity, and sustained Atsttrin release over seven weeks. In vitro cytocompatibility assays confirmed its non-cytotoxic nature, which was further corroborated by long-term in vivo safety assessments indicating the absence of organ toxicity up to three months post-administration. Functional studies using wild-type and 14-3-3ε knockout bone marrow-derived mesenchymal stem cells revealed that Atsttrin significantly enhanced chondrogenic and osteogenic differentiation in WT cells, effects that were markedly reduced in KO cells. Hydrogel-encapsulated Atsttrin elicited more robust regenerative responses compared to administration of free Atsttrin, underscoring the critical role of controlled release in enhancing therapeutic efficacy. In vivo, Atsttrin-loaded hydrogels significantly accelerated fracture healing in both WT and diabetic mice, with diminished efficacy in 14-3-3ε-deficient models. Collectively, these results support an important role for 14-3-3ε in mediating the regenerative effects of Atsttrin and demonstrate the potential of the GO-PEG/Collagen I hydrogel as a localized delivery platform for bone repair.

STATEMENT OF PROBLEM/BACKGROUND:The fatigue behavior under clinically relevant loading conditions of implant-supported screw-retained crowns cemented to titanium bases fabricated from different restorative materials remains insufficiently understood. PURPOSE/OBJECTIVE:The purpose of this study was to evaluate the failure modes, fatigue reliability, and survival probabilities of metal-ceramic (MC), monolithic zirconia (3Y-TZP), and lithium disilicate (LD) single premolar implant-supported screw-retained crowns cemented to titanium bases using step-stress accelerated life testing (SSALT). MATERIAL AND METHODS/METHODS:Sixty crowns were bonded to titanium bases (UNP RH 4 mm, GH 2 mm; Adin Dental Implant Systems Ltd), connected to internal hexagon implants (4.2-mm platform diameter, 10-mm length; Touareg S, Adin Dental Implant Systems Ltd), embedded in acrylic resin blocks, and subjected to single-load-to-failure testing (n=6) to determine stress profiles for SSALT (n=54). Use-level probability Weibull curves were calculated to estimate reliability for a mission of 100 000 cycles at 200 and 300 N. Failed specimens underwent polarized light stereomicroscopy and scanning electron microscopy (SEM) for fractographic analysis. RESULTS:All specimens failed during SSALT loading profiles. Beta (β) values derived from use-level probability Weibull curves were greater than 1 for all groups, indicating fatigue-driven failure behavior. 3Y-TZP crowns demonstrated the highest fatigue reliability, with survival probabilities up to 98% at tested load levels (200 and 300 N). LD showed intermediate performance (93% at 200 N and 88% at 300 N), whereas MC crowns showed the lowest survival probabilities (86% at 200 N and 82% at 300 N). At 200 N, no statistically significant differences were observed among groups. At 300 N, 3Y-TZP crowns showed significantly higher survival probability than MC crowns (P=.038), while LD showed intermediate values and was not significantly different from either group. Fractographic analysis revealed material-specific fracture origins and crack propagation patterns. CONCLUSIONS:All crown types demonstrated high survival probabilities. 3Y-TZP crowns showed higher fatigue reliability than MC crowns, while LD crowns demonstrated intermediate performance.

Three-dimensionally (3D)-printed alpha-tricalcium phosphate (α-TCP) scaffolds, fabricated through a low-temperature hydrothermal dissolution-precipitation process, replicate the structural and compositional features of native bone. Reinforcing hydrothermally processed α-TCP with poly(lactic-co-glycolic acid) (PLGA) as a binder has previously been shown to confer distinct mechanical advantages, supporting its potential as a viable material for bone regenerative scaffolds. Although the hydrothermal processing of α-TCP scaffolds and PLGA-based mechanical reinforcement have each been characterized individually in earlier studies, this work represents the first pre-clinical in vivo assessment of osseoconduction and biocompatibility of 3D-printed, PLGA-reinforced, self-hardening calcium phosphate scaffolds in a large translational animal model. A ceramic ink suitable for extrusion was prepared by combining a 30 wt/vol% poloxamer 407 solution with α-TCP powder at a 0.45 wt/wt ratio (CTRL). A second extrudable ink, consisting of an α-TCP ceramic suspension incorporating a 35 wt/wt% PLGA binder, was formulated at a 0.5 wt/wt ratio (EXP). Cylindrical scaffolds (6 mm × 6 mm) were fabricated at room temperature using a custom-built Direct Ink Write 3D printer, then hydrothermally treated via submersion in water and thermal consolidation at 121 °C. Osteotomies were created in the ilium of adult sheep, with two cylindrical defects (7 mm × 6 mm) per animal, each receiving either a CTRL or EXP scaffold. Animals were euthanized at 3 and 12 weeks post-surgery (n = 6 animals per time point), and samples were collected en bloc for analysis. For both scaffold formulations, hard tissue formed by 12 weeks displayed high cellularity and active vascularization, consistent with early woven bone formation. Quantitative analysis revealed no significant between-group differences in bone formation at either time point (p > 0.05). These findings indicate that 3D-printed, PLGA-reinforced, self-hardening α-TCP scaffolds are osseoconductive and biocompatible, supporting their potential use in orthopedic and craniomaxillofacial bone defect repair.

Critical-sized bone defects remain a significant clinical challenge, and dipyridamole (DIPY)-coated 3D-tricalcium phosphate (β-TCP) scaffolds have shown promising osteogenic efficacy in preclinical models. However, the literature on the systematic physicochemical characterization of this scaffold system, including optimization of DIPY loading parameters, release kinetics, and surface properties, is lacking. This study addresses these gaps by characterizing DIPY-loaded 3D-printed β-TCP scaffolds across solid and porous architectures, three coating concentrations (10, 100, and 1000 µM), and three coating volumes (250, 500, and 1000 µL). Under static PBS conditions, drug release over 21 days was quantifiable only at 1000 µM, and release-kinetics modeling (zero-order, Higuchi, and Korsmeyer-Peppas) was therefore restricted to this highest concentration. At 1000 µM, both scaffold types showed biphasic release profiles, with standard empirical models reasonably approximating the overall kinetics, while not fully capturing the biphasic behavior over the entire duration. Porous scaffolds showed significant volume-dependent release (p = 0.002, η

This study evaluated the effects of glass infiltration and hydrothermal aging on the microstructural and optical properties of minimally processed recycled 3Y-TZP. Unprocessed 3Y-TZP remnants were milled into powder, compacted into discs, and sintered. Specimens were divided into six groups according to glass infiltration and hydrothermal aging (immediate, 50 h, and 100 h at 134 °C/2.2 bar). Particle size was measured by laser diffraction. Density and optical properties (contrast ratio and translucency) were longitudinally evaluated on the same specimens using Archimedes' principle and reflectance measurements (n = 10), whereas crystalline phases (Raman spectroscopy, n = 3), surface and cross-sectional morphology (n = 3), and elemental composition (n = 3) were analyzed on independent specimens allocated to each experimental condition. Color stability and translucency variation were compared with perceptibility (PT = 0.81; TPT = 0.62) and acceptability (AT = 1.77; TAT = 2.62) thresholds (n = 10). Density data were analyzed using one-way repeated-measures ANOVA, while optical properties were analyzed using two-way repeated-measures ANOVA, followed by Tukey's post hoc test. Mean particle size of recycled powder was 1.61 μm. Relative densities for immediate, 50 h, and 100 h groups were 99.68%, 99.24%, and 99.04%. Raman spectra revealed predominance of tetragonal-cubic phases in immediate non-infiltrated group, while monoclinic phase prevailed in others. SEM showed homogeneous surfaces. EDS confirmed zirconium, yttrium, and hafnium in non-infiltrated groups, and silicon, aluminum, sodium, potassium, and calcium in infiltrated. Non-infiltrated groups showed lower contrast ratio and greater translucency than infiltrated, independent of aging. Aging minimally affected optical properties, except infiltrated specimens, where translucency was higher immediately than after 50-100 h. All groups exhibited color and translucency variation below perceptibility and acceptability thresholds. Prolonged hydrothermal degradation influenced the microstructural and optical features of recycled 3Y-TZP, while glass infiltration further modified these characteristics, reducing translucency while increasing opacity and color stability.

Conductive hydrogels have emerged as promising materials for soft tissue interfacing by combining tissue-like mechanical compliance with electrical conductivity, thereby enabling improved electrical communication with electroactive biological tissues. This work presents an electroconductive composite hydrogel fabricated via light-based vat-polymerization by integrating a choline-based bio-ionic liquid (IL) with gelatin methacryloyl (GelMA). The resulting hydrogels demonstrate tunable conductivity, structural integrity, and high print fidelity when fabricated using digital light processing (DLP) light-based 3D printing. Electrical conductivity was optimized at 20% v/v IL concentration, with the hydrogels demonstrating stable performance for over 28 days. A food-grade photoabsorber was integrated into the formulation to improve DLP resolution and was effectively removed after printing process. The hydrogels supported the human mesenchymal stem cells' viability and proliferation, confirming their cytocompatibility. They also promoted enhanced maturation of primary neurons, demonstrating a supportive microenvironment for neural cells. In vivo implantation of indocyanine green-loaded hydrogels exhibited sustained stability and robust retention of signal over a period of 4 weeks, with histological analysis indicating seamless integration with surrounding tissues. Impedance spectroscopy at both gut and spinal cord interfaces illustrated that GelMA/IL composites achieved the lowest impedance across a range of frequencies, outperforming both GelMA-only and tissue-only conditions. Collectively, these findings position light-based vat-polymerized electroconductive composites as a promising platform for the development of anatomically conformal materials tailored for soft tissue interfacing.

Rhinoplasty is a technically demanding procedure in which the precision of osteotomy creation directly influences cosmetic and functional outcomes. Traditional osteotomes often produce uncontrolled fracture lines and soft tissue trauma. Piezoelectric devices have been introduced as an alternative. They offer selective cutting of mineralized tissue while sparing surrounding soft tissue structures. Although the clinical benefits of this approach have been well documented, the biological processes defining this technique remain unsettled. The current study aimed to compare the histological changes in bone regeneration and long-term healing outcomes within piezotome-induced and osteotome-induced nasal bone defects in a translational, preclinical ovine model. Bilateral osteotomies were created on the nasal bone of n=12 skeletally mature sheep using a piezoelectric bone-cutting system (Piezotome CUBE, Acteon) or a traditional osteotome. Euthanasia was performed at either 3 or 12 weeks postoperatively (6 defects per group per time point). Histological analysis at 3 weeks postoperatively revealed limited bone ingrowth, followed by substantial bone regeneration in both groups by 12 weeks. Osteotome-treated sites displayed irregular margins and bone debris, while piezotome-treated defects demonstrated cleaner margins and less bony fragmentation. Despite qualitative differences, semi-quantitative scoring of new bone formation showed no statistically significant differences in healing between devices at 3 weeks (p=0.500) or 12 weeks (p=0.125). These findings suggest that although piezoelectric osteotomies may offer advantages in intraoperative precision and early postoperative morbidity, long-term bone regeneration appears comparable to that achieved with conventional osteotomes.

Intraoral soft-tissue defects are traditionally managed with autogenous connective tissue grafts, though donor site morbidity has driven interest in xenogeneic collagen matrices as alternatives. However, the impact of matrix architecture on soft-tissue integration remains poorly understood. This study compared soft-tissue responses to a sheet-form collagen matrix (ShCM) and a spongy collagen matrix (SpCM) placed beneath full-thickness flaps in a beagle mandibular defect model. Standardized bilateral defects were created in 23 skeletally mature female beagles. Defects were then assigned to serve as the negative control (sham) or were treated with porcine collagen matrix in (i) sheet form (ShCM) (Regenity Biosciences, Oakland, NJ, USA), or (ii) porous/spongy form (SpCM) (Fibro-Gide^®, Geistlich Pharma North America, West Windsor Township, NJ, USA). The mandibular sites that received no surgical intervention served as positive controls. Experimental conditions were randomized and interpolated within each animal to minimize anatomical site bias and evaluated histologically at 4- (n = 7), 8- (n = 7), and 12-weeks (n = 9) postoperatively. Histologic sections were evaluated for matrix presence, inflammation, subepithelial healing, and matrix thickness. At 4 weeks, both matrices were present, though SpCM showed significantly higher inflammation scores (p = 0.013). By 8 weeks, ShCM demonstrated greater resorption (p = 0.003) alongside an organized collagen layer with fibroblasts and new microvessels, while SpCM remained thick and porous, with a persistent fibrous capsule and elevated inflammation versus both ShCM (p = 0.002) and sham (p = 0.009). At 12 weeks, inflammation declined and subepithelial healing improved similarly across matrix groups. These findings suggest matrix architecture influences soft-tissue healing outcomes in the oral cavity. Sheet-form matrices may be preferable where biocompatibility and predictable integration are priorities, while spongy matrices may better support long-term space maintenance and tissue ingrowth. However, clinical studies are needed to confirm these translational implications.

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.