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Objective: To quantitatively assess the impact of early versus late surgical intervention on midfacial growth using a mouse model., Methods: A full-thickness mucoperiosteal flap surgery was performed on newborn (P17) mice and on neonatal (P30) mice. High-resolution micro-computed tomographic imaging coupled with histomorphometric analyses was used to assess craniomaxillofacial growth. Histology and immunohistochemical analyses were used to assess cellular and molecular responses postsurgery., Results: Early surgical intervention at P17 resulted in significant midfacial growth arrest, with pronounced maxillary hypoplasia. Histomorphometric analyses revealed significant (P < 0.05) growth disruptions in the mid-palatal suture complex, including premature removal of the cartilaginous growth plate and its replacement by bone. In the suture itself, cell proliferation was significantly reduced (P < 0.05) compared with controls. The same surgical intervention performed in mice at P30 did not lead to significant midfacial growth arrest., Conclusions: Early surgical intervention in a mouse model mirrors the adverse growth outcomes in children undergoing early cleft repair. Molecular and cellular observations accompanying this midfacial growth arrest may inform therapeutic strategies to mitigate midfacial growth disturbances in patients and highlight the need for refined surgical techniques to minimize adverse growth outcomes., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of Mutaz B. Habal, MD.)

Aims: This study aimed to examine whether surgical treatment for a facial disfigurement influenced an individual's quality of life., Methods and Results: One-on-one interviews were conducted with the aim of synthesizing participant's medical experiences into common themes. Additionally, participants completed the World Health Organization's Quality of Life Brief Version (WHOQOL-BREF) questionnaire. The WHOQL-BREF is a standardized testing instrument with four domains of 26 questions, meant to analyze participants' overall quality of health, physical health, psychological status, social relationships, and environmental health. Our study revealed that women with visible facial differences experienced a quality of life below the average of the general population. However, in those who reported above-average quality of life, a key theme emerged: active participation in the choice to undergo surgical treatment. Participants who felt this sense of agency in the decision-making process also reported a more positive healthcare experience. They felt more respected by others, indicating a strong connection between personal agency, surgical choices, and overall well-being., Conclusions: These findings reveal that personal agency plays an important role in the decision-making process for patients undergoing surgical treatment for facial differences, as it improves quality of life and has a positive impact on overall healthcare experience and well-being., (© 2024 Special Care Dentistry Association and Wiley Periodicals LLC.)

Aim: To qualitatively and quantitatively evaluate the formation and maturation of peri-implant soft tissues around 'immediate' and 'delayed' implants., Materials and Methods: Miniaturized titanium implants were placed in either maxillary first molar (mxM1) fresh extraction sockets or healed mxM1 sites in mice. Peri-implant soft tissues were evaluated at multiple timepoints to assess the molecular mechanisms of attachment and the efficacy of the soft tissue as a barrier. A healthy junctional epithelium (JE) served as positive control., Results: No differences were observed in the rate of soft-tissue integration of immediate versus delayed implants; however, overall, mucosal integration took at least twice as long as osseointegration in this model. Qualitative assessment of Vimentin expression over the time course of soft-tissue integration indicated an initially disorganized peri-implant connective tissue envelope that gradually matured with time. Quantitative analyses showed significantly less total collagen in peri-implant connective tissues compared to connective tissue around teeth around implants. Quantitative analyses also showed a gradual increase in expression of hemidesmosomal attachment proteins in the peri-implant epithelium (PIE), which was accompanied by a significant inflammatory marker reduction., Conclusions: Within the timeframe examined, quantitative analyses showed that connective tissue maturation never reached that observed around teeth. Hemidesmosomal attachment protein expression levels were also significantly reduced compared to those in an intact JE, although quantitative analyses indicated that macrophage density in the peri-implant environment was reduced over time, suggesting an improvement in PIE barrier functions. Perhaps most unexpectedly, maturation of the peri-implant soft tissues was a significantly slower process than osseointegration., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

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-κB (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 Tnfsf11 fl/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, Tnfsf11 fl/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 Tnfsf11 fl/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 Tnfsf11 fl/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., (© 2023 The Authors. Clinical Oral Implants Research published by John Wiley & Sons Ltd.)

The capacity of a tissue to continuously alter its phenotype lies at the heart of how an animal is able to quickly adapt to changes in environmental stimuli. Within tissues, differentiated cells are rigid and play a limited role in adapting to new environments; however, differentiated cells are replenished by stem cells that are defined by their phenotypic plasticity. Here we demonstrate that a Wnt-responsive stem cell niche in the junctional epithelium is responsible for the capability of this tissue to quickly adapt to changes in the physical consistency of a diet. Mechanical input from chewing is required to both establish and maintain this niche. Since the junctional epithelium directly attaches to the tooth surface via hemidesmosomes, a soft diet requires minimal mastication, and consequently, lower distortional strains are produced in the tissue. This reduced strain state is accompanied by reduced mitotic activity in both stem cells and their progeny, leading to tissue atrophy. The atrophied junctional epithelium exhibits suboptimal barrier functions, allowing the ingression of bacteria into the underlying connective tissues, which in turn trigger inflammation and mild alveolar bone loss. These data link the mechanics of chewing to the biology of tooth-supporting tissues, revealing how a stem cell niche is responsible for the remarkable adaptability of the junctional epithelium to different diets., Competing Interests: Declaration of Conflicting InterestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Purpose of Review: There is a growing appreciation within the scientific community that cells exhibit regional variation. Whether the variation is attributable to differences in embryonic origin or anatomical location and mechanical loading has not been elucidated; what is clear, however, is that adult cells carry positional information that ultimately affects their functions. The purpose of this review is to highlight the functions of osteocytes in the craniomaxillofacial (CMF) skeleton as opposed to elsewhere in the body, and in doing so gain mechanistic insights into genetic conditions and chemically-induced diseases that particularly affect this region of our anatomy., Recent Findings: In the CMF skeleton, elevated Wnt/β-catenin signaling affects not only bone mass and volume, but also mineralization of the canalicular network and osteocyte lacunae. Aberrant elevation in the Wnt/β-catenin pathway can also produce micropetrosis and osteonecrosis of CMF bone, presumably due to a disruption in the signaling network that connects osteocytes to one another, and to osteoblasts on the bone surface., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Background: The rate of reparative osteogenesis controls when an implant is sufficiently stable as to allow functional loading. Using a mini pig model, the rate of reparative osteogenesis in two types of implant sites for example, an osteotomy versus a fresh extraction socket were compared., Methods: Eight adult mini pigs were used for the study. In phase I, three premolars were extracted on one side of the oral cavity; 12 weeks later, in phase II, osteotomies were produced in healed extraction sites, and contralateral premolars were extracted. Animals were sacrificed 1, 5, and 12 weeks after phase II. Bone repair and remodeling were evaluated using quantitative micro-computed tomographic imaging, histology, and histochemical assays coupled with quantitative dynamic histomorphometry., Results: One week after surgery, extraction sockets and osteotomy sites exhibited similar patterns of new bone deposition. Five weeks after surgery, mineral apposition rates (MARs) were elevated at the injury sites relative to intact bone. Twelve weeks after surgery, the density of new bone in both injury sites was equivalent to intact bone but quantitative dynamic histomorphometry and cellular activity assays demonstrated bone remodeling was still underway., Conclusions: The mechanisms and rates of reparative osteogenesis were equivalent between fresh extraction sockets and osteotomies. The volume of new bone required to fill a socket, however, was significantly greater than the volume required to fill an osteotomy. These data provide a framework for estimating the rate of reparative osteogenesis and the time to loading of implants placed in healed sites versus fresh extraction sockets., (© 2022 American Academy of Periodontology.)

Aim: Autologous bone grafts consolidate faster than bone graft substitutes (BGSs) but resorb over time, which compromises implant support. We hypothesized that differences in consolidation rates affected the mechanical properties of grafts and implant stability, and tested whether a pro-osteogenic protein, liposomal WNT3A (L-WNT3A), could accelerate graft consolidation., Materials and Methods: A transgenic mouse model of sinus augmentation with immunohistochemistry, enzymatic assays, and histology were used to quantitatively evaluate the osteogenic properties of autografts and BGSs. Composite and finite element modelling compared changes in the mechanical properties of grafts during healing until consolidation, and secondary implant stability following remodelling activities. BGSs were combined with L-WNT3A and tested for its osteogenic potential., Results: Compared with autografts, BGSs were bioinert and lacked osteoprogenitor cells. While in autografted sinuses, new bone arose evenly from all living autograft particles, new bone around BGSs solely initiated at the sinus floor, from the internal maxillary periosteum. WNT treatment of BGSs resulted in significantly higher expression levels of pro-osteogenic proteins (Osterix, Collagen I, alkaline phosphatase) and lower levels of bone-resorbing activity (tartrate-resistant acid phosphatase activity); together, these features culminated in faster new bone formation, comparable to that of an autograft., Conclusions: WNT-treated BGSs supported faster consolidation, and because BGSs typically resist resorption, their use may be superior to autografts for sinus augmentation., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The roles of Wnt/β-catenin signaling in regulating the morphology and microstructure of craniomaxillofacial (CMF) bones was explored using mice carrying a constitutively active form of β-catenin in activating Dmp1-expressing cells (e.g., daβcat Ot mice). By postnatal day 24, daβcat Ot mice exhibited midfacial truncations coupled with maxillary and mandibular hyperostosis that progressively worsened with age. Mechanistic insights into the basis for the hyperostotic facial phenotype were gained through molecular and cellular analyses, which revealed that constitutively activated β-catenin in Dmp1-expressing cells resulted in an increase in osteoblast number and an increased rate of mineral apposition. An increase in osteoblasts was accompanied by an increase in osteocytes, but they failed to mature. The resulting CMF bone matrix also had an abundance of osteoid, and in locations where compact lamellar bone typically forms, it was replaced by porous, woven bone. The hyperostotic facial phenotype was progressive. These findings identify for the first time a ligand-independent positive feedback loop whereby unrestrained Wnt/β-catenin signaling results in a CMF phenotype of progressive hyperostosis combined with architecturally abnormal, poorly mineralized matrix that is reminiscent of craniotubular disorders in humans.

The main objectives of this work were to assess the efficiency, ease-of-use, and general performance of a novel osseoshaping tool based on first-user clinical experiences and to compare these observations with preclinical data generated in rodents using a miniaturized version of the instrument. All patients selected for the surgery presented challenging clinical conditions in terms of the quality and/or quantity of the available bone. The presented data were collected during the implant placement of 15 implants in 7 patients, and included implant recipient site (bone quality and quantity) and ridge evaluation, intra-operative handling of the novel instrument, and the evaluation of subsequent implant insertion. The instrument was easy to handle and was applied without any complications during the surgical procedure. Its use obviated the need for multiple drills and enabled adequate insertion torque in all cases. This biologically driven innovation in implant site preparation shows improvements in preserving vital anatomical and cellular structures as well as simplifying the surgical protocol with excellent ease-of-use and handling properties.

Objectives: Teeth connect to bone via a periodontal ligament, whereas implants connect to bone directly. Consequently, masticatory loads are distributed differently to periodontal versus peri-implant bone. Our objective was to determine how masticatory loading of an implant versus a tooth affected peri-implant versus periodontal bone remodeling. Our hypothesis was that strains produced by functional loading of an implant would be elevated compared with the strains around teeth, and that this would stimulate a greater degree of bone turnover around implants versus in periodontal bone., Materials and Methods: Sixty skeletally mature mice were divided into two groups. In the implant group, maxillary first molars (mxM1) were extracted, and after socket healing, titanium alloy implants were positioned subocclusally. After osseointegration, implants were exposed, resin crowns were placed, and masticatory loading was initiated. In the control group, the dentition was left intact. Responses of peri-implant and periodontal bone were measured using micro-CT, histology, bone remodeling assays, and quantitative histomorphometry while bone strains were estimated using finite element (FE) analyses., Conclusions: When a submerged osseointegrated implant is exposed to masticatory forces, peri-implant strains are elevated, and peri-implant bone undergoes significant remodeling that culminates in new bone accrual. The accumulation of new bone functions to reduce both peri-implant strains and bone remodeling activities, equivalent to those observed around the intact dentition., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Bone tissue engineering is a rapidly developing field with potential for the regeneration of craniomaxillofacial (CMF) bones, with 3D printing being a suitable fabrication tool for patient-specific implants. The CMF region includes a variety of different bones with distinct functions. The clinical implementation of tissue engineering concepts is currently poor, likely due to multiple reasons including the complexity of the CMF anatomy and biology, and the limited relevance of the currently used preclinical models. The 'recapitulation of a human disease' is a core requisite of preclinical animal models, but this aspect is often neglected, with a vast majority of studies failing to identify the specific clinical indication they are targeting and/or the rationale for choosing one animal model over another. Currently, there are no suitable guidelines that propose the most appropriate animal model to address a specific CMF pathology and no standards are established to test the efficacy of biomaterials or tissue engineered constructs in the CMF field. This review reports the current clinical scenario of CMF reconstruction, then discusses the numerous limitations of currently used preclinical animal models employed for validating 3D-printed tissue engineered constructs and the need to reduce animal work that does not address a specific clinical question. We will highlight critical research aspects to consider, to pave a clinically driven path for the development of new tissue engineered materials for CMF reconstruction., (© 2022 The Authors. Clinical and Translational Medicine published by John Wiley & Sons Australia, Ltd on behalf of Shanghai Institute of Clinical Bioinformatics.)

Tooth extraction triggers alveolar ridge resorption, and when this resorption is extensive, it can complicate subsequent reconstructive procedures that use dental implants. Clinical data demonstrate that the most significant dimensional changes in the ridge occur soon after tooth extraction. Here, we sought to understand whether a correlation existed between the rate at which an extraction socket heals and the extent of alveolar ridge resorption. Maxillary molars were extracted from young and osteoporotic rodents, and quantitative micro-computed tomographic imaging, histology, and immunohistochemistry were used to simultaneously follow socket repair and alveolar ridge resorption. Extraction sockets rapidly filled with new bone via the proliferation and differentiation of Wnt-responsive osteoprogenitor cells and their progeny. At the same time that new bone was being deposited in the socket, tartrate-resistant acid phosphatase-expressing osteoclasts were resorbing the ridge. Significantly faster socket repair in young animals was associated with significantly more Wnt-responsive osteoprogenitor cells and their progeny as compared with osteoporotic animals. Delivery of WNT3A to the extraction sockets of osteoporotic animals restored the number of Wnt-responsive cells and their progeny back to levels seen in young healthy animals and accelerated socket repair in osteoporotic animals back to rates seen in the young. In cases where the extraction socket was treated with WNT3A, alveolar ridge resorption was significantly reduced. These data demonstrate a causal link between enhancing socket repair via WNT3A and preserving alveolar ridge dimensions following tooth extraction.

Reducing the use of synthetic fertilizers and pesticides can limit negative impacts of agriculture on insects and is a crucial step towards sustainable agriculture. In the United States, organic agriculture has the potential to reduce greenhouse gas emissions, pollutant runoff, and biodiversity loss in the Midwestern Corn Belt-an area extending over 500,000 km2 devoted to intensive production of corn Zea mays (Linnaeus 1753) (Poales: Poaceae), often in rotation with soy Glycine max (Linnaeus 1753) (Fabales: Fabaceae) or wheat Triticum aestivum (Linnaeus 1753) (Poales: Poaceae). Working in 30-yr-long landscape experiments in this region, we tested for impacts of conventional versus organic agriculture on ant communities (Hymenoptera: Formicidae) and potential ecosystem services they provide. Organic fields supported higher ant diversity and a slightly more species-rich ant assemblage than conventionally managed fields but did not otherwise differ in community composition. Despite similar community composition, organic and conventional fields differed in seasonal patterns of ant foraging activity and potential for natural pest suppression. Conventional plots experienced higher overall ant foraging activity, but with the timing skewed towards late in the growing season such that 75% of ant foraging occurred after crop harvest in a wheat year and was therefore unavailable for pest suppression. Organic fields, in contrast, experienced moderate levels of ant foraging activity throughout the growing season, with most foraging occurring during crop growth. Organic fields thus supported twice as much pest suppression potential as conventional fields. Our results highlight the importance of timing in mediating ecosystem services in croplands and emphasize the value of managing landscapes for multiple services rather than yield alone., (© The Author(s) 2021. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Systemic inhibition of Notch with γ-secretase inhibitors (GSI) decreases multiple myeloma tumor growth, but the clinical use of GSI is limited due to its severe gastrointestinal toxicity. In this study, we generated a GSI Notch inhibitor specifically directed to the bone (BT-GSI). BT-GSI administration decreased Notch target gene expression in the bone marrow, but it did not alter Notch signaling in intestinal tissue or induce gut toxicity. In mice with established human or murine multiple myeloma, treatment with BT-GSI decreased tumor burden and prevented the progression of multiple myeloma-induced osteolytic disease by inhibiting bone resorption more effectively than unconjugated GSI at equimolar doses. These findings show that BT-GSI has dual anti-myeloma and anti-resorptive properties, supporting the therapeutic approach of bone-targeted Notch inhibition for the treatment of multiple myeloma and associated bone disease. SIGNIFICANCE: Development of a bone-targeted Notch inhibitor reduces multiple myeloma growth and mitigates cancer-induced bone destruction without inducing the gastrointestinal toxicity typically associated with inhibition of Notch., (©2021 American Association for Cancer Research.)

Objectives: Compared to autografts, bone graft substitutes are slower to consolidate. If we understood why, this might open strategies to accelerate new bone formation and thus shorten the time to implant placement. In this study, we aimed at comparing autologous bone graft with a bovine bone graft substitute in a preclinical sinus lift model., Materials and Methods: The mouse posterior paranasal sinus served as a recipient site for grafting. Autograft from the oral cavity was compared against bone graft substitute using molecular, cellular, and histological analyses conducted on post-grafting days (PSD) 0, 9, 18, and 120., Results: Either autografts or bone graft substitutes were positioned on the sinus floor and remained in situ throughout the study. At the time of grafting and until day 9, bone graft substitutes were devoid of cells and alkaline phosphatase (ALP) activity while autografts were comprised of viable cells and showed strong ALP (mineralization) activity. Consequently, new bone formed faster in autografts compared to bone graft substitutes (140.21 ± 41.21 µm vs. 41.70 ± 10.09 µm, respectively, PSD9, p = .0143). By PSD18, osteogenesis was evident in autografted and xenografted sites. Osteoclasts identified by tartrate resistant acid phosphatase attached to, but did not resorb the bone graft substitute matrix. Autograft matrix, however, underwent extensive resorption. Transgenic mice revealed that Wnt-responsive osteoprogenitor cells originated primarily from the internal periosteum of the maxillary bone, and not from the Schneiderian membrane., Conclusion: Autografts produce new bone sooner, but bovine bone graft substitutes eventually consolidate and then resist resorption. Enhancing osteoprogenitor cell recruitment to a bone graft substitute constitutes a viable strategy for accelerating bone formation in a sinus lift procedure., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Introduction: Few interspecies comparisons of alveolar bone have been documented, and this knowledge gap raises questions about which animal models most accurately represent human dental conditions or responses to surgical interventions., Objectives: The objective of this study was to employ state-of-the-art quantitative metrics to directly assess and compare the structural and functional characteristics of alveolar bone among humans, mini pigs, rats, and mice., Methods: The same anatomic location (i.e., the posterior maxillae) was analyzed in all species via micro-computed tomographic imaging, followed by quantitative analyses, coupled with histology and immunohistochemistry. Bone remodeling was evaluated with alkaline phosphatase activity and tartrate-resistant acid phosphatase staining to identify osteoblast and osteoclast activities. In vivo fluorochrome labeling was used as a means to assess mineral apposition rates., Results: Collectively, these analyses demonstrated that bone volume differed among the species, while bone mineral density was equal. All species showed a similar density of alveolar osteocytes, with a highly conserved pattern of collagen organization. Collagen maturation was equal among mouse, rat, and mini pig. Bone remodeling was a shared feature among the species, with morphologically indistinguishable hemiosteonal appearances, osteocytic perilacunar remodeling, and similar mineral apposition rates in alveolar bone., Conclusions: Our analyses demonstrated equivalencies among the 4 species in a plurality of the biological features of alveolar bone. Despite contradictory results from older studies, we found no evidence for the superiority of pig models over rodent models in representing human bone biology., Knowledge Transfer Statement: Animal models are extensively used to evaluate bone tissue engineering strategies, yet there are few state-of-the-art studies that rigorously compare and quantify the factors influencing selection of a given animal model. Consequently, there is an urgent need to assess preclinical animal models for their predictive value to dental research. Our article addresses this knowledge gap and, in doing so, provides a foundation for more effective standardization among animal models commonly used in dentistry.

Aim: To evaluate the similarities and differences in barrier function of a peri-implant epithelium (PIE) versus a native junctional epithelium (JE)., Materials and Methods: A mouse model was used wherein titanium implants were placed sub-occlusally in healed extraction sites. The PIE was examined at multiple timepoints after implant placement, to capture and understand the temporal nature of its assembly and homeostatic status. Mitotic activity, hemidesmosomal attachment apparatus, and inflammatory responses in the PIE were compared against a JE. Additionally, we evaluated whether the PIE developed a Wnt-responsive stem cell niche like a JE., Results: The PIE developed from oral epithelium (OE) that had, by the time of implant placement, lost all characteristics of a JE. Compared with a JE, an established PIE had more proliferating cells, exhibited lower expression of attachment proteins, and had significantly more inflammatory cells in the underlying connective tissue. Wnt-responsive cells in the OE contributed to an initial PIE, but Wnt-responsive cells and their descendants were lost as the PIE matured., Conclusions: Although histologically similar, the PIE lacked a Wnt-responsive stem cell niche and exhibited characteristics of a chronically inflamed tissue. Both features contributed to suboptimal barrier functions of the PIE compared with a native JE., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Bone debris generated during site preparation is generally evacuated with irrigation; here, we evaluated whether retention of this autologous material improved the rate of peri-implant bone formation., Methods: In 25 rats, a miniature implant system composed of an osseo-shaping tool and a tri-oval-shaped implant was compared against a conventional drill and round implant system. A split-mouth design was used, and fresh extraction sockets served as implant sites. Histology/histomorphometry, immunohistochemistry, and microcomputed tomography (μCT) imaging were performed immediately after implant placement, and on post-surgery days 3, 7, 14, and 28., Results: Compared with a conventional drill design, the osseo-shaping tool produced a textured osteotomy surface and viable bone debris that was retained in the peri-implant environment. Proliferating osteoprogenitor cells, identified by PCNA and Runx2 expression, contributed to faster peri-implant bone formation. Although all implants osseointegrated, sites prepared with the osseo-shaping tool showed evidence of new peri-implant bone sooner than controls., Conclusion: Bone debris produced by an osseo-shaping tool directly contributed to faster peri-implant bone formation and implant osseointegration., (© 2020 American Academy of Periodontology.)

Changes in trophic niche-the pathways through which an organism obtains energy and nutrients-are a fundamental way in which organisms respond to environmental conditions. But the capacity for species to alter their trophic niches in response to global change, and the ways they do so when able, remain largely unknown. Here we examine food webs in three long-term and large-scale experiments to test how resource availability and nutritional requirements interact to determine an organism's trophic niche in the context of one of the largest global trends in land use-the rise in bioenergy production. We use carbon and nitrogen stable isotope analyses to characterize arthropod food webs across three biofuel crops representing a gradient in plant resource richness (corn monocultures, fields dominated by native switchgrass and restored prairie), and to quantify changes in the trophic niche of a widespread generalist ant species across habitats. In doing so, we measure the effects of basal resource richness on food chain length, niche breadth and trophic position. We frame our results in the context of two hypotheses that explain variation in trophic niche-the niche variation hypothesis which emphasizes the importance of resource diversity and ecological opportunity, and the optimal diet hypothesis which emphasizes dietary constraints and the availability of optimal resources. Increasing plant richness lengthened food chains by 10%-20% compared to monocultures. Niche breadths of generalist ants did not vary with resource richness, suggesting they were limited by optimal diet requirements and constraints rather than by ecological opportunity. The ants instead responded to changes in plant richness by shifting their estimated trophic position. In resource-poor monocultures, the ants were top predators, sharing a trophic position with predatory spiders. In resource-rich environments, in contrast, the ants were omnivores, relying on a mix of animal prey and plant-based resources. In addition to highlighting novel ecosystem impacts of alternate bioenergy landscapes, our results suggest that niche breadth and trophic diversification depend more on the presence of optimal resources than on ecological opportunity alone., (© 2020 British Ecological Society.)

Some genetic disorders are associated with distinctive facial features, which can aid in diagnosis. While considerable advances have been made in identifying causal genes, relatively little progress has been made toward understanding how a particular genotype results in a characteristic craniofacial phenotype. An example is sclerosteosis/van Buchem disease, which is caused by mutations in the Wnt inhibitor sclerostin (SOST). Affected patients have a high bone mass coupled with a distinctive appearance where the mandible is enlarged and the maxilla is foreshortened. Here, mice carrying a null mutation in Sost were analyzed using quantitative micro-computed tomographic (µCT) imaging and histomorphometric analyses to determine the extent to which the size and shape of craniofacial skeleton were altered. Sost -/- mice exhibited a significant increase in appositional bone growth, which increased the height and width of the mandible and reduced the diameters of foramina. In vivo fluorochrome labeling, histology, and immunohistochemical analyses indicated that excessive bone deposition in the premaxillary suture mesenchyme curtailed overall growth, leading to midfacial hypoplasia. The amount of bone extracellular matrix produced by Sost -/- cells was significantly increased; as a consequence, osteoid seams were evident throughout the facial skeleton. Collectively, these analyses revealed a remarkable fidelity between human characteristics of sclerosteosis/van Buchem disease and the Sost -/- phenotype and provide clues into the conserved role for sclerostin signaling in modulating craniofacial morphology.

Wnt signaling maintains homeostasis in the bone marrow cavity: if Wnt signaling is inhibited then bone volume and density would decline. In this study, we identified a population of Wnt-responsive cells as osteoprogenitor in the intact trabecular bone region, which were responsible for bone development and turnover. If an implant was placed into the long bone, this Wnt-responsive population and their progeny contributed to osseointegration. We employed Axin2Cre CreERT2/+; R26 mTmG/+ transgenic mouse strain in which Axin2-positive, Wnt-responsive cells, and their progeny are permanently labeled by GFP upon exposure to tamoxifen. Each mouse received femoral implants placed into a site prepared solely by drilling, and a single-dose liposomal WNT3A protein was used in the treatment group. A lineage tracing strategy design allowed us to identify cells actively expressing Axin2 in response to Wnt signaling pathway. These tools demonstrated that Wnt-responsive cells and their progeny comprise a quiescent population residing in the trabecular region. In response to an implant placed, this population becomes mitotically active: cells migrated into the peri-implant region, up-regulated the expression of osteogenic proteins. Ultimately, those cells gave rise to osteoblasts that produced significantly more new bone in the peri-implant region. Wnt-responsive cells directly contributed to implant osseointegration. Using a liposomal WNT3A protein therapeutic, we showed that a single application at the time of implant placed was sufficient to accelerate osseointegration. The Wnt-responsive cell population in trabecular bone, activated by injury, ultimately contributes to implant osseointegration. Liposomal WNT3A protein therapeutic accelerates implant osseointegration in the long bone.

The most fundamental function of an epithelial tissue is to act as a barrier, regulating interactions between the external environment and the body. This barrier function typically requires a contiguous cell layer but since teeth penetrate the oral epithelium, a modified barrier has evolved, called the junctional epithelium (JE). In health, the JE attaches to the tooth, sealing the inside of the body against oral micro-organisms. Breakdown of the JE barrier results in periodontal ligament (PDL) disintegration, alveolar bone resorption, and ultimately tooth loss. Using lineage tracing and DNA pulse-chase analyses, we identified an anatomical location in the JE that supported both fast- and slow-cycling Wnt-responsive stem cells that contributed to self-renewal of the tissue. Stem cells produced daughter cells with an extraordinarily high rate of turnover that maintained JE integrity for 1.4 y in mice. Blocking cell proliferation via a chemotherapeutic agent 5-fluorouracil (5-Fu) eliminated fast-cycling stem cells, which caused JE degeneration, PDL destruction, and bone resorption. Upon removal of 5-Fu, slow-cycling stem cells regenerated both the structure and barrier function of the JE. Taken together, our studies identified a stem cell population in the JE and have potential clinical implications for prevention and treatment of periodontitis.

Our understanding of the mechanisms underlying fracture healing is rapidly developing and is contributing to new therapeutic strategies to enhance repair. To gain new insights, animal models must also evolve. From initially imprecise, uncontrolled bone defects we now have precise injury models that still capture all of the stages and phases of bone repair yet do so in a highly reproducible manner. The simple mono-cortical defect model allows assessment of bone repair through a cartilage intermediate, e.g., endochondral ossification, as well as direct bone repair, e.g., intramembranous healing. Cellular contributions of the periosteum can be distinguished from contributions originating in the bone marrow. In this chapter, we focus on the advantages of this bone repair model, as well as its limitations.

Aim: To identify the molecular mechanisms mediating the persistent defensive functions of the self-renewing junctional epithelium (JE)., Materials and Methods: Two strains of Wnt reporter mice, Axin2 CreErt2 /+ ;R26R mTmG /+ and Axin2 LacZ /+ , were employed, along with three clinically relevant experimental scenarios where the function of the JE is disrupted: after tooth extraction, after a partial gingivectomy, and after a complete circumferential gingivectomy., Results: Using transgenic Wnt reporter strains of mice, we established the JE is a Wnt-responsive epithelium beginning at the time of its formation and that it maintains this status into adulthood. After tooth extraction, progeny of the initial Wnt-responsive JE population directly contributed to healing and ultimately adopted an oral epithelium (OE) phenotype. In the traditional partial gingivectomy model, the JE completely regenerated and did so via progeny of the original Wnt-responsive population. However, following circumferential gingivectomy, the OE was incapable of re-establishing a functional JE., Conclusions: A Wnt-responsive niche at the interface between tooth and oral epithelia is required for a functional JE., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Autologous bone can be harvested from the flutes of a conventional drill or from a bone scraper; here we compared whether autologous bone chips generated by a new slow-speed instrument were more osteogenic than the bone chips generated by conventional drills or bone scrapers. Additionally, we tested whether the osteogenic potential of bone chips could be further improved by exposure to a Wnt signaling (WNT) therapeutic., Methods: Osteotomies were prepared in fresh rat maxillary first molar extraction sockets using a conventional drill or a new osseo-shaping instrument; titanium alloy implants were placed immediately thereafter. Using molecular/cellular and histologic analyses, the fates of the resulting bone chips were analyzed. To test whether increasing WNT signaling improved osteogenesis in an immediate post-extraction implant environment, a WNT therapeutic was introduced at the time of implant placement., Results: Bone collected from a conventional drill exhibited extensive apoptosis; in contrast, bone generated by the new instrument remained in situ, which preserved their viability. Also preserved was the viability of the osteoprogenitor cells attached to the bone chips. Exogenous treatment with a WNT therapeutic increased the rate of osteogenesis around immediate post-extraction implants., Conclusions: Compared with conventional drills or bone scrapers, a new cutting instrument enabled concomitant site preparation with autologous bone chip collection. Histology/histomorphometric analyses revealed that the bone chips generated by this new tool were more osteogenic and could be further enhanced by exposure to a WNT therapeutic. Even though gaps still existed in placebo controls and liposomal WNT3A (L-WNT3A) cases, the area of peri-implant bone was significantly greater in L-WNT3A treated sites., (© 2020 American Academy of Periodontology.)

Objectives: Oral implants transmit biting forces to peri-implant bone. In turn, those forces subject peri-implant bone to mechanical stresses and strains. Here, our objective was to understand how peri-implant bone responded to conditions of normal versus hyper-loading in a mouse model., Material and Methods: Sixty-six mice were randomly assigned to 2 groups; both groups underwent bilateral maxillary first molar extraction followed by complete healing. Titanium alloy implants were placed in healed sites and positioned below the occlusal plane. After osseointegration, a composite crown was affixed to the implant so masticatory loading would ensue. In controls, the remaining dentition was left intact but in the hyper-loaded (test) group, the remaining molars were extracted. 3D finite element analysis (FEA) calculated peri-implant strains resulting from normal and hyper-loading. Peri-implant tissues were analyzed at multiple time points using micro-computed tomography (µCT) imaging, histology, enzymatic assays of bone remodeling, and vital dye labeling to evaluate bone accrual., Results: Compared to controls, hyper-loaded implants experienced a 3.6-fold increase in occlusal force, producing higher peri-implant strains. Bone formation and resorption were both significantly elevated around hyper-loaded implants, eventually culminating in a significant increase in peri-implant bone volume/total volume (BV/TV). In our mouse model, masticatory hyper-loading of an osseointegrated implant was associated with increased peri-implant strain, increased peri-implant bone remodeling, and a net gain in bone deposition., Conclusion: Hyper-loading results in bone strain with catabolic and anabolic bone responses, leading to a net gain in bone deposition., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: in an effort to identify and validate which animal models are best suited for dental implant research, we used multiscale analyses to examine tooth extraction wound healing in a well-accepted model, the Yucatan mini pig and a more controversial model, the laboratory mouse., Methods: first molar extractions were performed in adult, skeletally mature mini pigs and mice. Alveolar bone repair was evaluated at early, intermediate and late timepoints using quantitative micro-computed tomographic (μCT) imaging, histology, molecular, and cellular assays. Vital dye labeling was employed to quantify mineral apposition rates (MAR) in both species., Results: Despite a 3000-fold difference in weight, the relative proportions of the mini pig and murine maxillae and are equivalent. Quantitative μCT demonstrated that within the posterior alveolar bone, the volume of mineralized bone was lower in mini pig than in the mice; during healing, however, the bone volume fraction was equivalent. The histologic appearance of healing sites was also comparable, and alkaline phosphatase (ALP) and tartrate resistant acid phosphatase (TRAP) staining showed a similar temporal and spatial distribution of bone remodeling. Vital dye labeling indicated equivalent MAR between the species. The absolute duration of the healing period differed: in mice, complete healing was accomplished in ∼21 days. In mini pigs, the same process took four times longer., Conclusions: Extraction socket healing is histologically equivalent between mini pigs and mice, supporting the hypothesis that the underlying mechanisms of alveolar bone healing are conserved among species., (© 2020 American Academy of Periodontology.)

The disconnect between preclinical and clinical results underscores the imperative for establishing good animal models, then gleaning all available data on efficacy, safety, and potential toxicities associated with a device or drug. Mini pigs are a commonly used animal model for testing orthopedic and dental devices because their skeletons are large enough to accommodate human-sized implants. The challenge comes with the analyses of their hard tissues: current methods are time-consuming, destructive, and largely limited to histological observations made from the analysis of very few tissue sections. We developed and employed cryo-based methods that preserved the microarchitecture and the cellular/molecular integrity of mini pig hard tissues, then demonstrated that the results of these histological, histochemical, immunohistochemical, and dynamic histomorphometric analyses e.g., mineral apposition rates were comparable with similar data from preclinical rodent models. Thus, the ability to assess static and dynamic bone states increases the translational value of mini pig and other large animal model studies. In sum, this method represents logical means to minimize the number of animals in a study while simultaneously maximizing the amount of information collected from each specimen.

Purpose/Aim : The aim of this study was to explore whether dentinogenesis imperfecta (DGI)-related aberrations are detectable in odontogenic tissues. Materials and Methods : Morphological and histological analyses were carried out on 3 teeth (two maxillary 1 st molars, one maxillary central incisor) extracted from a patient with DGI Type II. A maxillary 2 nd molar teeth extracted from a healthy patient was used as control. A micro-computed tomographic (μCT) data-acquisition system was used to scan and reconstruct samples. Pentachrome and picrosirius red histologic stains were used to analyze odontogenic tissues and their collagenous matrices. Results : Our findings corroborate DGI effects on molar and incisor root elongation, and the hypo-mineralized state of DGI dentin. In addition to these findings, we discovered changes to the DGI pulp cavity: Reactionary dentin formation, which we theorize is exacerbated by the early loss of enamel, nearly obliterated an acellular but still-vascularized DGI pulp cavity. We also discovered an accumulation of lamellated cellular cementum at the root apices, which we hypothesize compensates for the severe and rapid attrition of the DGI tooth. Conclusions : Based on imaging and histological data, we propose a novel hypothesis to explain the complex dental phenotypes observed in patients with DGI Type II.

Objectives: Our objective was to test the hypothesis that local delivery of a WNT protein therapeutic would support osseointegration of an unstable implant placed into an oversized osteotomy and subjected to functional loading., Materials and Methods: Using a split-mouth design in an ovariectomized (OVX) rat model, 50 titanium implants were placed in oversized osteotomies. Implants were subjected to functional loading. One-half of the implants were treated with a liposomal formulation of WNT3A protein (L-WNT3A); the other half received an identical liposomal formulation containing phosphate-buffered saline (PBS). Finite element modeling estimated peri-implant strains caused by functional loading. Histological, molecular, cellular, and quantitative micro-computed tomographic (µCT) imaging analyses were performed on samples from post-implant days (PID) 3, 7, and 14. Lateral implant stability was quantified at PID 7 and 14., Results: Finite element analyses predicted levels of peri-implant strains incompatible with new bone formation. Micro-CT imaging, histological, and quantitative immunohistochemical (IHC) analyses confirmed that PBS-treated implants underwent fibrous encapsulation. In those cases where the peri-implant environment was treated with L-WNT3A, µCT imaging, histological, and quantitative IHC analyses demonstrated a significant increase in expression of proliferative (PCNA) and osteogenic (Runx2, Osterix) markers. One week after L-WNT3A treatment, new bone formation was evident, and two weeks later, L-WNT3A-treated gaps had a stiffer interface compared to PBS-treated gaps., Conclusion: In a rat model, unstable implants undergo fibrous encapsulation. If the same unstable implants are treated with L-WNT3A at the time of placement, then it results in significantly more peri-implant bone and greater interfacial stiffness., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Objective: Compared to autologous bone grafts, allogeneic bone grafts integrate slowly, which can adversely affect clinical outcomes. Here, our goal was to understand the molecular mechanisms underlying graft incorporation, and then test clinically feasible methods to accelerate this process., Methods: Wild-type and transgenic Wnt "reporter" mice were used in a vertical ridge augmentation procedure. The surgery consisted of tunneling procedure to elevate the maxillary edentulous ridge periosteum, followed by the insertion of bone graft. Micro-computed tomographic imaging, and molecular/cellular analyses were used to follow the bone graft over time. Sclerostin null mice, and mice carrying an activated form of β-catenin were evaluated to understand how elevated Wnt signaling impacted edentulous ridge height and based on these data, a biomimetic strategy was employed to combine bone graft particles with a formulation of recombinant WNT protein. Thereafter, the rate of graft incorporation was evaluated., Results: Tunneling activated osteoprogenitor cell proliferation from the periosteum. If graft particles were present, then osteoprogenitor cells attached to the matrix and gave rise to new bone that augmented edentulous ridge height. Graft particles alone did not stimulate osteoprogenitor cell proliferation. Based on the thicker edentulous ridges in mice with amplified Wnt signaling, a strategy was undertaken to load bone graft particles with WNT; this combination was sufficient to accelerate the initial step of graft incorporation., Significance: Local delivery of a WNT protein therapeutic has the potential to accelerate graft incorporation, and thus shorten the time to when the graft can support a dental implant., (Copyright © 2020 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.)

Introduction: Physiological root resorption is a common occurrence in mammalian teeth, which suggests that there must be a corollary consisting of physiological cementum repair. The mechanism(s) responsible for this physiological repair process is unknown and was the focus of this study., Methods: Using a rat model, we explored first the prevalence of physiological root resorption and then asked whether this prevalence changed as a result of an osteoporotic phenotype. The cellular mechanisms of resorption were characterized using a combination of finite element modeling coupled with in-vivo histologic, molecular, and cellular analyses in rats. A potential molecular mechanism for cementum repair was uncovered using a strain of transgenic mice in which Wnt-responsive cells could be labeled and followed over time., Results: In rats, most resorption lacunae were concentrated on the distal surfaces of the roots. Rat molars undergo a physiological tooth drift distally, and using finite element modeling, we calculated the magnitude of the compressive strains that accumulated on these surfaces in response to mastication. Although the overall strain magnitudes were low, they were constant and coincided with the presence of resorption lacunae. Where resorption lacunae were present, progeny from a Wnt-responsive population of stem cells, embedded in the periodontal ligament, directly contributed to the repair of the lacunae., Conclusions: Despite the fact that both are clastic conditions, an osteoporotic phenotype in rats was not associated with an increase in the prevalence of physiological root resorption. The location of the resorption lacunae corresponded to sites of low but constant compressive strains produced by physiological distal drift. At least 1 mechanism responsible for physiological cementum repair involved the contribution of Wnt-responsive stem or progenitor cells originating in the periodontal ligament. These data point toward a potential Wnt-based strategy to regenerate cementum in subjects with disease or damage., (Copyright © 2020 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Aims: Surgeons and most engineers believe that bone compaction improves implant primary stability without causing undue damage to the bone itself. In this study, we developed a murine distal femoral implant model and tested this dogma., Methods: Each mouse received two femoral implants, one placed into a site prepared by drilling and the other into the contralateral site prepared by drilling followed by stepwise condensation., Results: Condensation significantly increased peri-implant bone density but it also produced higher strains at the interface between the bone and implant, which led to significantly more bone microdamage. Despite increased peri-implant bone density, condensation did not improve implant primary stability as measured by an in vivo lateral stability test. Ultimately, the condensed bone underwent resorption, which delayed the onset of new bone formation around the implant., Conclusion: Collectively, these multiscale analyses demonstrate that condensation does not positively contribute to implant stability or to new peri-implant bone formation. Cite this article: Bone Joint Res. 2020;9(2):60-70., Competing Interests: ICMJE COI statement: J. Brunski reports payments from Nobel Biocare for consultancy and lectures., (© 2020 Author(s) et al.)

Autologous bone grafts constitute the second most transplanted tissue in medicine today. The viability, and consequently the osteogenic capacity, of an autograft is directly impacted by the interval between harvest and transplantation, but how the temperature and the solution in which the graft is held intraoperatively affect viability is not clear. Using a syngeneic mouse model and in vivo bone-forming assays, these variables were tested for their effects on programmed cell death, osteoprogenitor cell proliferation, and the ability of the autograft to ultimately produce new bone in an ectopic site. Based on these results, the intraoperative treatment with a WNT protein therapeutic was tested for its effects on the viability and osteogenic capacity of an autograft. Viability, programmed cell death, mitotic activity, osteogenic protein expression, and bone-forming capacity were assessed. Experimental results demonstrated that the osteogenic capacity of an autograft is significantly improved by intraoperative storage in L-WNT3A at physiological temperature., (© 2019 John Wiley & Sons, Ltd.)

Objective: Primary stability is a prerequisite for implant osseointegration. Some degree of misfit between an implant and its osteotomy is required to ensure primary stability, and this is typically achieved by undersizing an implant osteotomy. In this preclinical study, we aimed at understanding the relationship between misfit, insertion torque, implant stability, and their cumulative short- and longer-term effects on peri-implant bone., Materials and Methods: We placed implants in maxillary extraction sites of a rat; in the control group, these implants had minimal misfit while those in the test group had a high degree of misfit and therefore osseo-densified the peri-implant bone., Results: Compared to controls, the misfit-induced stresses produced by osseo-densification led to micro-fractures in the peri-implant bone and an extensive zone of dying osteocytes. High interfacial pressures produced a pro-resorptive environment as shown by tartrate-resistant acid phosphatase activity and cathepsin K immunostaining (IHC). The lack of alkaline phosphatase activity and collagen I IHC supported the absence of new bone formation. Collectively, micro-computed tomography imaging, quantification of bone-implant contact (BIC), vimentin, and IL1-β IHCs demonstrated that implant failure occurred soon afterward, which presented as a crater-like lesion filled with fibrous, inflamed granulation tissue around the test implants., Conclusion: By controlling every other risk indicator, we confirmed how excessive osseo-densification can lead directly to osseo-destruction., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Epithelia of the oral cavity exhibit variations in morphologies and turnover rates. Are these differences related to environment or to region-specific stem cell populations? A lineage-tracing strategy allowed visualization of Wnt-responsive cells, and their progeny, in the hard and soft palates. In both anatomic locations, Wnt-responsive basal cells self-renewed and gave rise to supra-basal cells. Palatal injuries triggered an enlargement of this population, and their descendants were responsible for wound re-epithelialization. Compared with the hard palate, soft palate stem cells exhibited an earlier, more robust burst in proliferation, culminating in significantly faster repair. Thereafter, excess Wnt-responsive basal cells were removed, and stem cell numbers were restored back to homeostatic level. Thus, we uncovered a stem cell population in oral mucosa, and its relative abundance is correlate with the rate of oral wound healing. Besides the activation during injury, an endogenous mechanism exists to constrain the stem cell pool after repair., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

Introduction: Odontoblasts produce dentin throughout life and in response to trauma. The purpose of this study was to identify the roles of endogenous Wnt signaling in regulating the rate of dentin accumulation., Methods: Histology, immunohistochemistry, vital dye labeling, and histomorphometric assays were used to quantify the rate of dentin accumulation as a function of age. Two strains of Wnt reporter mice were used to identify and follow the distribution and number of Wnt-responsive odontoblasts as a function of age. To show a causal relationship between dentin secretion and Wnt signaling, dentin accumulation was monitored in a strain of mice in which Wnt signaling was aberrantly elevated., Results: Dentin deposition occurs throughout life, but the rate of accumulation slows with age. This decline in dentin secretion correlates with a decrease in endogenous Wnt signaling. In a genetically modified strain of mice, instead of tubular dentin, aberrantly elevated Wnt signaling resulted in accumulation of reparative dentin or osteodentin secreted from predontoblasts., Conclusions: Wnt signaling regulates dentin secretion by odontoblasts, and the formation of reparative or osteodentin is the direct consequence of elevated Wnt signaling. These preclinical data have therapeutic implications for the development of a biologically based pulp capping medicant., (Copyright © 2019 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.)

Our goal was to evaluate alveolar bone healing in OVX mice, and to assess the functional utility of a WNT-based treatment to accelerate healing in mice with an osteoporotic-like bony phenotype., Introduction: Is osteoporosis a risk factor for dental procedures? This relatively simple question is exceedingly difficult to answer in a clinical setting, for two reasons. First, as an age-related disease, osteoporosis is frequently accompanied by age-related co-morbidities that can contribute to slower tissue repair. Second, the intervals at which alveolar bone repair are assessed in a clinical study are often measured in months to years. This study aimed to evaluate alveolar bone repair in ovariectomized (OVX) mice and provide preclinical evidence to support a WNT-based treatment to accelerate alveolar bone formation., Methods: OVX was performed in young mice to produce an osteoporotic-like bone phenotype. Thereafter, the rate of extraction socket healing and osteotomy repair was assessed. A liposomal WNT3A treatment was tested for its ability to promote alveolar bone formation in this OVX-induced model of bone loss., Results: Bone loss was observed throughout the murine skeleton, including the maxilla, and mirrored the pattern of bone loss observed in aged mice. Injuries to the alveolar bone, including tooth extraction and osteotomy site preparation, both healed significantly slower than the same injuries produced in young controls. Given sufficient time, however, all injuries eventually healed. In OVX mice, osteotomies healed significantly faster if they were treated with L-WNT3A., Conclusions: Alveolar bone injuries heal slower in OVX mice that exhibit an osteoporotic-like phenotype. The rate of alveolar bone repair in OVX mice can be significantly promoted with local delivery of L-WNT3A.

Chronic periodontitis (ChP) is a prevalent inflammatory disease affecting 46% of the US population. ChP produces a profound local inflammatory response to dysbiotic oral microbiota that leads to destruction of alveolar bone and tooth loss. ChP is also associated with systemic illnesses, including cardiovascular diseases, malignancies, and adverse pregnancy outcomes. However, the mechanisms underlying these adverse health outcomes are poorly understood. In this prospective cohort study, we used a highly multiplex mass cytometry immunoassay to perform an in-depth analysis of the systemic consequences of ChP in patients before ( n = 28) and after ( n = 16) periodontal treatment. A high-dimensional analysis of intracellular signaling networks revealed immune system-wide dysfunctions differentiating patients with ChP from healthy controls. Notably, we observed exaggerated proinflammatory responses to Porphyromonas gingivalis -derived lipopolysaccharide in circulating neutrophils and monocytes from patients with ChP. Simultaneously, natural killer cell responses to inflammatory cytokines were attenuated. Importantly, the immune alterations associated with ChP were no longer detectable 3 wk after periodontal treatment. Our findings demarcate systemic and cell-specific immune dysfunctions in patients with ChP, which can be temporarily reversed by the local treatment of ChP. Future studies in larger cohorts are needed to test the boundaries of generalizability of our results.

Despite an extensive literature documenting the adaptive changes of bones and ligaments to mechanical forces, our understanding of how tissues actually mount a coordinated response to physical loading is astonishingly inadequate. Here, using finite element (FE) modeling and an in vivo murine model, we demonstrate the stress distributions within the periodontal ligament (PDL) caused by occlusal hyperloading. In direct response, a spatially restricted pattern of apoptosis is triggered in the stressed PDL, the temporal peak of which is coordinated with a spatially restricted burst in PDL cell proliferation. This culminates in increased collagen deposition and a thicker, stiffer PDL that is adapted to its new hyperloading status. Meanwhile, in the adjacent alveolar bone, hyperloading activates bone resorption, the peak of which is followed by a bone formation phase, leading ultimately to an accelerated rate of mineral apposition and an increase in alveolar bone density. All of these adaptive responses are orchestrated by a population of Wnt-responsive stem/progenitor cells residing in the PDL and bone, whose death and revival are ultimately responsible for directly giving rise to new PDL fibers and new bone.

Vertebrate teeth are attached to the jawbones using a variety of methods but in mammals, a fibrous connection is the norm. This fibrous periodontal ligament (PDL) allows teeth to move in the jawbones in response to natural eruptive forces, mastication, and orthodontic tooth movement. In some disease states the PDL either calcifies or is replaced by a mineralized tissue and the result is ankylosis, where the tooth is fused to the alveolar bone. To understand how the PDL maintains this fibrous state, we examined a strain of mice in which tooth movement is arrested. Daβcat Ot mice express a stabilized form of β-catenin in DMP1-positive alveolar bone osteocytes and cementocytes, which results in elevated Wnt signaling throughout the periodontium. As a consequence, there is an accrual of massive amounts of cellular cementum and alveolar bone, the PDL itself calcifies and teeth become ankylosed. These data suggest that to maintain its fibrous nature, Wnt signaling must normally be repressed in the PDL space., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

Osteoporosis is associated with decreased bone density and increased bone fragility, but how this disease affects alveolar bone healing is not clear. The objective of this study was to determine the extent to which osteoporosis affects the jaw skeleton and then to evaluate possible mechanisms whereby an osteoporotic phenotype might affect the rate of alveolar bone healing following tooth extraction. Using an ovariectomized mouse model coupled with micro-computed tomographic imaging, histologic, molecular, and cellular assays, we first demonstrated that the appendicular and jaw skeletons both develop osteoporotic phenotypes. Next, we demonstrated that osteoporotic mice exhibit atrophy of the periodontal ligament (PDL) and that this atrophy was accompanied by a reduction in the pool of osteoprogenitor cells in the PDL. The paucity of PDL-derived osteoprogenitor cells in osteoporotic mice was associated with significantly slower extraction socket healing. Collectively, these analyses demonstrate that the jaw skeleton is susceptible to the untoward effects of osteoporosis that manifest as thinner, more porous alveolar bone, PDL thinning, and slower bone repair. These findings have potential clinical significance for older osteopenic patients undergoing reconstructive procedures.

Of all geometric shapes, a tri-oval one may be the strongest because of its capacity to bear large loads with neither rotation nor deformation. Here, we modified the external shape of a dental implant from circular to tri-oval, aiming to create a combination of high strain and low strain peri-implant environment that would ensure both primary implant stability and rapid osseointegration, respectively. Using in vivo mouse models, we tested the effects of this geometric alteration on implant survival and osseointegration over time. The maxima regions of tri-oval implants provided superior primary stability without increasing insertion torque. The minima regions of tri-oval implants presented low compressive strain and significantly less osteocyte apoptosis, which led to minimal bone resorption compared to the round implants. The rate of new bone accrual was also faster around the tri-oval implants. We further subjected both round and tri-oval implants to occlusal loading immediately after placement. In contrast to the round implants that exhibited a significant dip in stability that eventually led to their failure, the tri-oval implants maintained their stability throughout the osseointegration period. Collectively, these multiscale biomechanical analyses demonstrated the superior in vivo performance of the tri-oval implant design.

A soft food diet leads to changes in the periodontal ligament (PDL). These changes, which have been recognized for more than a century, are ascribed to alterations in mechanical loading. While these adaptive responses have been well characterized, the molecular, cellular, and mechanical mechanisms underlying the changes have not. Here, we implicate Wnt signaling in the pathoetiology of PDL responses to underloading. We show that Wnt-responsive cells and their progeny in the PDL space exhibit a burst in proliferation in response to mastication. If an animal is fed a soft diet from the time of weaning, then this burst in Wnt-responsive cell proliferation is quelled; as a consequence, both the PDL and the surrounding alveolar bone undergo atrophy. Returning these animals to a hard food diet restores the Wnt signaling in PDL. These data provide, for the first time, a molecular mechanism underlying the adaptive response of the PDL to loading.

The preservation of bone viability at an osteotomy site is a critical variable for subsequent implant osseointegration. Recent biomechanical studies evaluating the consequences of site preparation led us to rethink the design of bone-cutting drills, especially those intended for implant site preparation. We present here a novel drill design that is designed to efficiently cut bone at a very low rotational velocity, obviating the need for irrigation as a coolant. The low-speed cutting produces little heat and, consequently, osteocyte viability is maintained. The lack of irrigation, coupled with the unique design of the cutting flutes, channels into the osteotomy autologous bone chips and osseous coagulum that have inherent osteogenic potential. Collectively, these features result in robust, new bone formation at rates significantly faster than those observed with conventional drilling protocols. These preclinical data have practical implications for the clinical preparation of osteotomies and alveolar bone reconstructive surgeries., Competing Interests: The authors declare no conflicts of interest.

Purpose: This systematic review was prepared as part of the Academy of Osseointegration (AO) 2018 Summit, held August 8-10 in Oak Brook Hills, Illinois, to assess the relationship between the primary (mechanical) and secondary (biological) implant stability., Materials and Methods: Electronic and manual searches were conducted by two independent examiners in order to address the following issues. Meta-regression analyses explored the relationship between primary stability, as measured by insertion torque (IT) and implant stability quotient (ISQ), and secondary stability, by means of survival and peri-implant marginal bone loss (MBL)., Results: Overall, 37 articles were included for quantitative assessment. Of these, 17 reported on implant stability using only resonance frequncy analysis (RFA), 11 used only IT data, 7 used a combination of RFA and IT, and 2 used only the Periotest. The following findings were reached: ·Relationship between primary and secondary implant stability: Strong positive statistically significant relationship (P < .001). ·Relationship between primary stability by means of ISQ and implant survival: No statistically significant relationship (P = .4). ·Relationship between IT and implant survival: No statistically significant relationship (P = .2). ·Relationship between primary stability by means of ISQ unit and MBL: No statistically significant relationship (P = .9). ·Relationship between IT and MBL: Positive statistically significant relationship (P = .02). ·Accuracy of methods and devices to assess implant stability: Insufficient data to address this issue., Conclusion: Data suggest that primary/mechanical stability leads to more efficient achievement of secondary/biological stability, but the achievement of high primary stability might be detrimental for bone level stability. While current methods/devices for tracking implant stability over time can be clinically useful, a robust connection between existing stability metrics with implant survival remains inconclusive.

With the introduction of high-speed cutting tools, clinicians have recognized the potential for thermal damage to the material being cut. Here, we developed a mathematical model of heat transfer caused by drilling bones of different densities and validated it with respect to experimentally measured temperatures in bone. We then coupled these computational results with a biological assessment of cell death following osteotomy site preparation. Parameters under clinical control, e.g., drill diameter, rotational speed, and irrigation, along with patient-specific variables such as bone density were evaluated in order to understand their contributions to thermal damage. Predictions from our models provide insights into temperatures and thresholds that cause osteocyte death and that can ultimately compromise stability of an implant.

The objective of our experiments was to identify new therapeutic strategies to stimulate dentin formation in an adult tooth. To address this objective, we evaluated dentin production in 2 acute trauma models: one involving a pulp exposure and the other involving a superficial dentin injury. Molecular, cellular, and histologic analyses revealed that in response to a severe injury, where the pulp is exposed to the oral cavity, cell death is rampant and the repair response initiates from surviving pulp cells and, to a lesser extent, surviving odontoblasts. When an injury is superficial, as in the case of a dentin injury model, then disturbances are largely confined to pulp tissue immediately underneath the damaged dentin tubules. We found that the pulp remained vital and innervated; primary odontoblasts upregulated HIF1α; and the rate of mineralization was significantly increased. A tamoxifen-inducible Axin2 CreERT2/+ ; R26R mTmG/+ reporter strain was then used to demonstrate that a population of long-lived Wnt-responsive odontoblasts, which secreted dentin throughout the life of the animal, were responsible for depositing new dentin in response to a superficial injury. Amplifying Wnt signaling in the pulp stimulates dentin secretion, and in the dentin injury model, we show that a liposomal formulation of human WNT3A protein passes through dentinal tubules and is capable of upregulating Wnt signaling in the pulp. These data provide strong proof of concept for a therapeutic pulp-capping material to stimulate Wnt signaling in odontoblasts and thus improve the pulp repair response.

The aim of this study was to gain insights into the biology and mechanics of immediate postextraction implant osseointegration. To mimic clinical practice, murine first molar extraction was followed by osteotomy site preparation, specifically in the palatal root socket. The osteotomy was positioned such that it removed periodontal ligament (PDL) only on the palatal aspect of the socket, leaving the buccal aspect undisturbed. This strategy created 2 distinct peri-implant environments: on the palatal aspect, the implant was in direct contact with bone, while on the buccal aspect, a PDL-filled gap existed between the implant and bone. Finite element modeling showed high strains on the palatal aspect, where bone was compressed by the implant. Osteocyte death and bone resorption predominated on the palatal aspect, leading to the loss of peri-implant bone. On the buccal aspect, where finite element modeling revealed low strains, there was minimal osteocyte death and robust peri-implant bone formation. Initially, the buccal aspect was filled with PDL remnants, which we found directly provided Wnt-responsive cells that were responsible for new bone formation and osseointegration. On the palatal aspect, which was devoid of PDL and Wnt-responsive cells, adding exogenous liposomal WNT3A created an osteogenic environment for rapid peri-implant bone formation. Thus, we conclude that low strain and high Wnt signaling favor osseointegration of immediate postextraction implants. The PDL harbors Wnt-responsive cells that are inherently osteogenic, and if the PDL tissue is healthy, it is reasonable to preserve this tissue during immediate implant placement.