Faculty Bibliography

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.

Osseointegration is critical for the long-term success of endosteal implants, as it is influenced by factors such as implant design, material selection, and site of implantation. Considering the structural and vascular properties of trabecular bone, it is reasonable to hypothesize that osseointegration could be enhanced in this region. However, emerging evidence indicates that cortical bone frequently offers a more favorable environment for osseointegration. The objective was to conduct a systematic review of preclinical translational studies comparing osseointegration outcomes around implants placed in cortical and trabecular bone. Preclinical studies comparing bone-to-implant contact (BIC) and bone area fraction occupied (BAFO) between cortical and trabecular regions in animals with solid endosteal implants were retrieved from the PubMed, EMBASE, and Cochrane databases. We included randomized and nonrandomized preclinical translational trials published in English between 2014 and 2024 that reported at least one outcome of interest. Exclusion criteria comprised in vitro or ex vivo experiments, research involving human subjects, studies using powder, liquid, or plasma implants, abstracts, technical descriptions, and narrative or systematic reviews. The systematic review comprised 15 studies, which included a total of 298 animals and 877 implants. The mean follow-up period ranged between 4 and 17 weeks. In 13 studies, the cortical bone region demonstrated higher BIC values, with differences in BIC between cortical and trabecular bone ranging from 5.55% to 49.55% during the first 4 weeks, 1.80% to 51.30% between 4 and 8 weeks, and 9.65% to 35.41% following the 8-week healing period. Regarding BAFO values, data were reported in three studies, all of which indicated elevated values in cortical bone. The mean difference in the first 4 weeks ranged from 15.83% to 29.92%, and from 26.33% to 60.11% after 4 weeks of healing. These findings suggest that cortical regions exhibit enhanced short- and long-term osseointegration outcomes compared to trabecular bone regions. Impact Statement The specific site of implantation significantly influences the degree and rate of osseointegration. Trabecular bone, characterized by its high porosity and larger surface area relative to volume, facilitates the diffusion of nutrients and oxygen from the surrounding marrow and blood vessels. Nevertheless, emerging evidence indicates that cortical bone, due to its greater density and superior mechanical properties, often provides a more stable environment for osseointegration compared to trabecular bone. This systematic review of preclinical studies represents the first comprehensive effort to evaluate and compare osseointegration in cortical versus trabecular bone.

Two-photon polymerization (2PP) has enabled three-dimensional printing at micro- and nanometer level resolution, allowing for the fabrication of patient-specific implants and finely structured cell scaffolds. This comprehensive review highlights recent advancements in integrating 2PP across various medical specialties, emphasizing its potential role in clinical and translational settings including ophthalmology, orthopedics, neurology, dermatology, and otolaryngology. Despite technological achievements, significant challenges hinder its widespread use, which are also discussed. This includes scaling of manufacturing processes, ensuring long-term biocompatibility of fabricated structures, and a lack of 2PP research in other medical fields. Advancements in biomaterials, photoinitiators, and integrated fabrication approaches within 2PP could significantly impact clinical practice and further improve patient outcomes.

There has been an increasing trend in using piezoelectric devices in craniofacial surgery to selectively cut bone and reduce collateral soft tissue trauma. Although the benefits of piezosurgery have been well demonstrated for osteotomies, its impact on bone healing during rasping remains understudied. This study evaluated bone regeneration following medial maxillary rasping performed with a manual rasp (MR) compared with piezotome-assisted rasping (PR) in a skeletally mature sheep model. Bilateral defects (rasps: ∼2 cm x ∼2 cm) were created along the coronal plane on the anterodorsal aspect of the nasal bone, with PR used on the anatomic right side and MR on the anatomic left side. Nondecalcified histologic processing and analysis was performed on the nasomaxillary bone at 3 and 12 weeks postoperatively (n=6 sheep/timepoint). At 3 weeks, MR-treated defects showed smoother, intact bone defect margins with minimal bone deposition. PR-treated defects displayed more irregular margins with scattered bone fragments, consistent with ultrasonic microfracturing. By 12 weeks, both techniques demonstrated comparable healing patterns with a regenerating nasal bone contour, maturation of bone architecture, visible osteocytes, and no evidence of bone fragments or inflammatory infiltrates. Semiquantitative scoring of osteogenesis revealed statistically homogenous findings between MR and PR usage (p=0.63 at 3 weeks; p=1.00 at 12 weeks). Within the limits of this model, piezotome-assisted rasping altered early bone surface topography but did not impair long-term bone regeneration compared with manual rasping. This provides preclinical support for piezotome use as an alternative bone-modifying technique in rhinoplasty.

Tricalcium phosphate (TCP) bioceramics, available as α- and β-polymorphs, are frequently employed in the production of three-dimensionally (3D) printed bone scaffolds. Although hydrothermal immersion processing (HP) and sintering (S) are commonly adopted as post-printing techniques for bioceramics, a comprehensive comparative analysis of their effects on the osteogenic performance of α- and β-polymorphs in vivo remains inadequately investigated. In this study, α-TCP and β-TCP scaffolds were fabricated via direct ink writing and subjected to hydrothermal immersion processing (α-TCP/HP) and sintering (β-TCP/S) prior to implantation in n = 12 skeletally mature sheep (n = 1 scaffold per group per animal), and the outcome variables were evaluated at 3 and 12 weeks postoperatively (n = 6 sheep per time point). The quantitative results showed no significant differences in bone deposition or scaffold resorption at 3 weeks postoperatively (p = 0.618 and p = 0.898, respectively). However, at 12 weeks, there was a significant increase in osteogenesis and scaffold resorption in the β-TCP/S cohort relative to the α-TCP/HP counterparts (p < 0.001 and p = 0.004, respectively). β-TCP scaffolds subjected to post-print sintering exhibited superior osteoconductive and resorptive profiles compared to hydrothermal immersion-processed α-TCP scaffolds over the 12-week healing period.

Trabecular Metal^TM (TM) dental implants comprise a tantalum (Ta)-based biomimetic open-cell structure designed to replicate the structural, functional, and physiological properties of cancellous bone. Yet, the current literature primarily focuses on the evaluation of osseointegration outcomes surrounding TM implants in uncompromised bone environments and/or brief periods of observation in pre-clinical models. In addition, the performance of TM implants in bony defect environments reconstructed with allogenic grafts and bioactive molecules, such as platelet-rich fibrin (PRF), has not been thoroughly investigated. This longitudinal, randomized clinical trial comprised patients presenting with completely edentulous maxillaries. Guided Bone Regeneration (GBR) was performed using a cortico-cancellous allograft/PRF agglomerate. After 26 weeks, bone biopsies were obtained, followed by the insertion of a TM implant, after which patients were allowed to heal for 52 weeks for assessment of osseointegration. Qualitatively, histomicrographs at 26 weeks confirmed the presence of newly formed bone extending from the periphery of defects and along the direct surface of the allograft. TM implant biopsies at 52 weeks demonstrated osseointegration with bone ongrowth and ingrowth at the interconnected, porous trabecular region. These histological characteristics were consistent across all patients. No metal debris was detected, and the TM implants maintained their porous structure throughout the study period. TM implants placed in PRF-augmented allograft-reconstructed maxillae fostered a conducive environment for osseointegration. By leveraging the open-cell Ta structure, robust new bone formation was achieved without signs of adverse tissue reactions.

Osseodensification (OD) has emerged as a favorable osteotomy preparation technique that preserves and compacts autogenous bone along the osteotomy walls during site preparation, enhancing primary stability and implant osseointegration. While OD has demonstrated promising results in low-density trabecular bone, especially when used in conjunction with acid-etched (AE) implant surfaces, its efficacy in high-density cortical bone remains unclear-particularly in the context of varying implant surface characteristics. In this study, Grade V titanium alloy implants (Ti-6Al-4V, 4 mm × 10 mm) with deep threads, designated bone chambers and either as-machined (Mach) or AE surfaces were placed in 3.8 mm diameter osteotomies in the submandibular region of 16 adult sheep using either OD or conventional (Reg) drilling protocols. Insertion torque values (N·cm) were measured at the time of implant placement to evaluate primary stability. Mandibles were harvested at 3-, 6-, 12-, or 24-weeks post-implantation (n = 4 sheep/time point), and histologic sections were analyzed to quantify bone-to-implant contact (BIC) and bone area fractional occupancy (BAFO). Qualitative histological analysis confirmed successful osseointegration among all groups at each of the healing time points. No statistically significant differences were observed between OD and conventional drilling techniques in insertion torque (p > 0.628), BIC (p > 0.135), or BAFO (p > 0.060) values, regardless of implant surface type or healing interval. The findings indicate that neither drilling technique nor implant surface treatment significantly influences osseointegration in high density cortical bone. Furthermore, as the osteotomy was not considerably undersized, the use of OD instrumentation showed no signs of necrosis, inflammation, microfractures, or impaired osseointegration in dense cortical bone. Both OD and Reg techniques appear to be suitable for implant placement in dense bone, allowing flexibility based on surgeon preference and clinical circumstances.

In an effort to improve bone response, predictably regenerate lost tissue, and provide an anatomically pleasing ridge contour for biomechanically favorable and prosthetically driven implant placement, guided bone regeneration (GBR) procedures have been indicated. This study provides the first direct in vivo comparison of the biocompatibility of an experimental porcine-derived collagen membrane (CMI, Regenity Biosciences, Paramus, NJ, USA) and a commercially available bovine-derived collagen membrane (CopiOs, ZimVie, Palm Beach Gardens, FL, USA) in a beagle mandibular model for the purposes of GBR. Four bilateral defects of 10 mm × 10 mm through the mandibular thickness were placed in each of n = 16 adult beagle dogs. Defects were filled with a deproteinized porcine-derived particulate graft and were covered either with CMI or CopiOs to allow compartmentalized healing. Animals were euthanized after 4, 8, 12, or 16 weeks post-operatively (n = 4 beagles/time point). Bone regenerative capacity, graft, and soft tissue presence were evaluated by histomorphometric and microtomographic analyses. Outcome variables were compared using a mixed model analysis with fixed factor variables of time and material. Qualitatively, no histomorphological differences in healing were observed between the membrane groups at any time point. Histomorphometrically, CMI and CopiOs presented statistically significant differences in bone (mean ± SD: 38.27% ± 15.20 vs. 17.43% ± 15.49, respectively, p = 0.016) and soft tissue presence (mean ± SD: 50.88% ± 11.83 vs. 68.21% ± 16.98, respectively, p = 0.026) at 8 weeks. These results might influence treatment timing in clinical practice, by enabling early implant placement or shorter healing intervals. No significant differences were detected in these parameters at any other healing time point (p > 0.05). CMI and CopiOs showed no signs of adverse immune response and led to similar trends in bone regeneration after 16 weeks of permitted healing. Both membranes minimized soft tissue infiltration and maintained defect stability over the observed healing periods without adverse events such as inflammation and/or foreign body reaction.

Peri-implant disease and gingival recession may be partially attributed to inadequate keratinized tissue. Soft tissue augmentation procedures utilizing non-autologous biomaterials, such as porcine-derived collagen membranes, have been gaining prominence and exogenous crosslinking is being actively investigated to improve the collagen membrane's stability and potential for keratinized tissue gain. The aim of this preclinical study was to evaluate the performance of a novel, crosslinked porcine collagen membrane (Zderm^TM, Osteogenics Biomedical, Lubbock, TX, USA) relative to an established, commercially available, non-crosslinked counterpart (Mucograft^®, Geistlich Pharma North America Inc., Princeton, NJ, USA) in a canine mandibular model. Bilateral split-thickness mucosal defects were created in adult beagles (n = 17), with each site receiving one membrane. Qualitative and quantitative histomorphometric analyses of groups were performed after 4, 8, and 12 weeks of healing and compared to unoperated, positive controls from the same subject. No significant differences in membrane presence were observed between Zderm^TM and Mucograft^® at 4, 8, and 12 weeks of permitted healing (p > 0.05). Similarly, the average keratinized tissue (KT) length between Zderm^TM and Mucograft^® groups was statistically equivalent across all healing times (p > 0.05). However, qualitative histological evaluation revealed greater rete ridge morphology amongst defects treated with Zderm^TM in comparison to Mucograft^®. Nevertheless, both membranes exhibited excellent biocompatibility and are well-suited for soft tissue augmentation procedures in the oral cavity.