The miniature pig: a useful large animal model for dental and orofacial research

High-Frequency Ultrasound Characterization of Periodontal Soft Tissues Pre- and Post-Bacterial Inoculation

OBJECTIVE

Current diagnostic methods of inflammatory periodontal diseases, e.g., visual evaluation, periodontal probing, and radiographs, are either subjective or insensitive. Intra-oral high-frequency ultrasound was investigated to quantify inflammation by detecting tissue dimensional and perfusion changes.

METHODS

A cohort of 15-month-old mini-pigs, 4 female/male each, was analyzed. Pre-molars (PM) 3 and 4, as well as first molars (M1), were scanned. In bi-weekly time intervals all 4 quadrants were randomly enrolled and bacterial injection followed each quadrant scan in a weekly fashion. Soft tissue dimensions were obtained from B-mode images and statistically analyzed to identify correlations to inoculation time, i.e., response to bacterial loading, tooth type and sex, using analysis of variance and regression analysis. Color flow velocity and power-weighted color pixel density was obtained and statistically analyzed analogous to soft tissue.

RESULTS

Soft tissue thickness increased significantly post-inoculation at 1 and 2 mm below the free gingival margin for both genders and all observed teeth. The significance lasted for weeks 2, 4 and 6, except for female M1s (4 weeks). Color flow velocity was significantly higher compared with baseline for 6 weeks, except for male PM4 (2 weeks). Color flow power did not show significance for PM3 and 4, only in M1 (except male week 4). Significance also extended to tooth type and sex.

CONCLUSION

Periodontal tissue dimension and color flow velocity increased in correlation to bacterial inoculation. Further studies are needed to obtain an understanding of the underlying biology observed here. Eruption of dentition may have been a confounding factor for inflammation interpretation.

Comparison of cone-beam computed tomography with photon-counting detector computed tomography for dental implant surgery

PURPOSE

To compare cone-beam computed tomography (CBCT) with photon-counting detector computed tomography (PCD-CT) at equivalent radiation doses, focusing on qualitative and quantitative parameters relevant to dental implant surgery.

METHODS

This ex vivo comparative study of porcine specimens assessed five imaging protocols with both CBCT and PCD-CT at three effective radiation dose levels (high: 360µSv, standard: 145µSv, low: 20µSv) to evaluate image quality, artifact burden, metal artifact susceptibility, and quantitative bone measurements in the mandibular region. Three blinded readers analyzed the data using a 5-point Likert scale (5 = highest to 1 = lowest rating) and performed linear bone measurements at implant planning sites. Statistical analysis included descriptive statistics and inter-reader reliability assessment using intraclass correlation coefficients (ICC).

RESULTS

Each reader evaluated 30 data sets (12 CBCT, 18 PCD-CT), with 24 implant planning sites per imaging protocol. High-dose PCD-CT demonstrated the best image quality and diagnostic interpretability (4.89 ± 0.27), followed by standard-dose PCD-CT and CBCT (4.50 ± 0.73; 4.33 ± 0.61), with low-dose protocols showing intermediate quality with higher artifact burden. In comparison to CBCT, PCD-CT demonstrated superior performance in reducing implant-induced artifacts across all protocols. Quantitative bone measurements showed minimal variability, meeting clinical precision requirements for computer-assisted implant surgery. Both qualitative (ICCs:0.70-0.89; p < 0.001) and quantitative (ICCs:0.79-1; p < 0.001) analyses demonstrated high reliability, regardless of the reader's experience.

CONCLUSIONS

PCD-CT demonstrated superior image quality and reduced artifacts compared with CBCT at all radiation dose levels. These findings highlight PCD-CT's potential to enhance implant planning and improve clinical outcomes with reduced radiation exposure while maintaining diagnostic accuracy.

Nanotherapy targeting anti-aging skin cells: harnessing ursolic acid from Ocimum sanctum Linn for precision skin rejuvenation - a molecular perspective

The necessity of this work lies in the innovative application of nanotherapy to target anti-ageing skin cells, utilising ursolic acid from Ocimum sanctum Linn for precise and effective skin rejuvenation at a molecular level. Ursolic acid (UA), a pentacyclic triterpenoid compound, found in abundance in the plant O. sanctum Linn, has long been recognised for its potential anti-inflammatory, antioxidant, and anti-ageing properties. Despite its promising benefits, the direct application of UA in skincare has been limited, primarily due to its low aqueous solubility and poor skin penetration. This study explores a groundbreaking molecular approach, employing nanotechnology to enhance the delivery of UA, targeting skin cells for effective anti-ageing treatment. Through a comprehensive investigation, UA was encapsulated into biocompatible nanocarriers, ensuring increased stability, improved dermal penetration, and sustained release of the compound at the targeted site. By harnessing the specificity and efficiency of nanodelivery systems, the study achieved significant improvement in the absorption of UA in the deeper layers of the skin. This targeted intervention at the cellular and molecular level paved the way for maximising the potential of UA as an anti-ageing agent. In conclusion, the nanotherapeutic delivery of UA from O. sanctum Linn offers a paradigm shift in skincare, bringing forth a promising molecular strategy to combat skin ageing. With further advancements, this approach has the potential to revolutionise anti-ageing treatments, integrating traditional botanical wisdom with cutting-edge nanotechnology.

Selective Adipose Cryolysis for Reduction of Lingual Tissue in a Porcine Model

OBJECTIVES

Oropharyngeal fat volume is associated with obstructive sleep apnea (OSA) severity. Selective adipose cryolysis may produce cold-induced adipose cell death while sparing surrounding tissues. This study explored (1) similarities in tongue fat between porcine and human models and (2) the feasibility and potential reduction of lingual fat using selective adipose cryolysis.

STUDY DESIGN

Porcine model.

SETTING

Preclinical research laboratory under IACUC-approved protocols.

METHODS

Anatomical, histological, and biochemical characterizations of tongue tissue from 6 porcine and 4 human cadaver specimens were conducted to establish comparative frameworks. Comparison of fat distribution and composition was conducted via image analysis of histological sections as well as gas chromatography analysis of fatty acid composition. Safety and efficacy of selective adipose cryolysis were evaluated in an additional 16 porcine animals using a prototype cooling system. Histological analysis examined tissue response at 3, 6, 30, and 45 d posttreatment.

RESULTS

Comparative analysis revealed similar fat distribution and composition between human and porcine tongues. Selective adipose cryolysis induced progressive reduction in treated area tongue fat content at all timepoints, from 42% at baseline to 32% (t = 3 d) and 14% (t = 30 d), accompanied by macrophage infiltration, crown-like structure formation, and tissue remodeling.

CONCLUSION

Selective adipose cryolysis holds promise as a targeted therapeutic approach for reducing lingual fat in humans. The porcine model may provide valuable insight into treatment mechanisms and support initial translational work. Further research is warranted to elucidate long-term treatment outcomes and optimize clinical implementation strategies, with the goal of improving management of OSA in humans.

Quantitative Ultrasound for Periodontal Soft Tissue Characterization

OBJECTIVE

Periodontal diseases are a spectrum of inflammatory diseases that affect 45.9% of adults aged ≥30 years in the United States Current standard of care in clinics for the assessment of oral soft tissue inflammation is bleeding on probing,which is invasive, subjective and semi-qualitative. Quantitative ultrasound (QUS) has shown promising results in the non-invasive quantitative characterization of various soft tissues; however, it has not been used in clinical periodontics.

METHODS

Here, we investigated the QUS analysis of two periodontal soft tissues (alveolar mucosa and gingiva) in vivo. The study cohort included 10 swine scanned at four oral quadrants, resulting in 40 scans. Two-parameter Burr and Nakagami models were employed for QUS-based speckle modeling. Parametric imaging of these parameters was also created using an optimal window size estimated in a separate phantom study.

RESULTS

Phantom results suggested a window size of 10 wavelengths as the reasonable estimation kernel. The Burr power-law parameter and Nakagami shape factor were higher in gingiva than alveolar mucosa, while Burr and Nakagami scale factors were both lower in the gingiva. The difference between the two tissue types was statistically significant (p < 0.0001). Linear classifications of these two tissue types using a 2-D parameter space of the Burr and Nakagami models resulted in a segmentation accuracy of 93.51% and 90.91%, respectively. Findings from histology-stained images showed that gingiva and alveolar mucosa had distinct underlying structures, with the gingiva showing a denser stain.

CONCLUSION

QUS results suggest that gingiva and alveolar mucosa can be differentiated using Burr and Nakagami parameters. We propose that QUS holds promising potential for the characterization of periodontal soft tissues and could become an objective and quantitative diagnostic tool for periodontology and implant dentistry to improve dental health care.

From anatomy to surgery: Effectiveness of virtual simulation adjuvant to traditional methods in the preclinical training of apicoectomy

Anatomy forms the foundation for the training and execution of routine surgical procedures. However, a gap persists in effectively bridging anatomical knowledge with the confident performance of procedures. Virtual simulation (VS) techniques, based on experiential and situated learning theory, hold promise in addressing this challenge. Apicoectomy, a procedure involving root apex resection to preserve a tooth, requires a blend of regional and dental anatomy knowledge, making it an ideal model for assessing the effectiveness of VS. This prospective cohort study evaluated primarily the enhancement of incorporating VS training in the preclinical skill training of apicoectomy for undergraduate dental students, compared to relying solely on traditional methods. VS training includes the simulated dissection process, patient examination, and apicoectomy based on graphically synthesized virtual models. Secondly, the study investigated the influence of exposure to VS training on students' confidence and satisfaction. The training was divided into three progressive levels aligned with students' cognitive processes, employing Miller's competence learning framework. Participants were categorized into the control group (CG) (n = 214) and VS training group (VSTG) (n = 220) based on their classes. The results demonstrated that VSTG showed significantly greater training enhancement (VSTG: 7.14 ± 1.74; CG: 6.57 ± 2.02, p = 0.002) and higher confidence levels (VSTG: 2.94 ± 0.13; CG: 2.69 ± 0.13, p < 0.001), along with greater satisfaction with the training compared to the CG (VSTG: 3.70 ± 0.18; CG: 3.20 ± 0.17, p < 0.001). In conclusion, VS proves to be a valuable adjunct for enhancing procedural skill training in surgical procedures.

Peri-implant bone regeneration in pigs

PURPOSE

To review the current literature to answer the focused question: in the experimental pig model (population), which types of peri-implant bone defects (exposure) have been used evaluate different modes of therapy and what is their capacity for spontaneous healing and regeneration (outcome)?

METHODS

Following PRISMA guidelines, electronic databases were searched for studies reporting peri-implant bone defects in the maxillae or mandibles of pigs. Those studies which reported a control group of untreated defects with assessment of spontaneous regeneration [new bone area (BA)] and/or re-osseointegration [new bone-to-implant contact (BIC)] via quantitative radiography or histomorphometry were included in a random effects meta-analysis for the outcomes BA and BIC.

RESULTS

Overall, 21 studies, mostly performed in the mandibles of minipigs, were included. Most studies reported 'acute' intrabony (circumferential and/or dehiscence; n = 12) or supra-alveolar defects (horizontal; n = 4). Five studies attempted to induce 'chronic' peri-implantitis lesions using ligatures with conflicting results. Meta-analyses revealed pooled estimates (with 95% confidence intervals) of 48.07% BIC (30.14-66%) and 64.31% BA (42.71-85.91%) in intrabony defects, and 52.09% BIC (41.83-62.35%) and 28.62% BA (12.97-44.28%) in supra-alveolar defects. Heterogeneity in the meta-analysis was high (I2 > 90%).

CONCLUSION

Current evidence for peri-implant bone regeneration in pigs is mainly based on acute intrabony defects, which demonstrate a high capacity for spontaneous regeneration and re-osseointegration. The evidence for chronic peri-implantitis is limited and does not clearly indicate a spontaneous progression of the disease in this animal model.

Comparison of Amino Acid Digestibility between Commercial Crossbred Pigs and Mini-Jeju Island Native Pigs

The objectives of this study were to determine the apparent ileal digestibility and standardized ileal digestibility (SID) of crude protein (CP) and amino acids (AA) in feed ingredients, compare the ileal digestibility of CP and AA between commercial crossbred pigs and mini-Jeju Island native pigs (JINP), and develop models for estimating SID of CP and AA for commercial pigs using mini-JINP data. The study involved five crossbred commercial pigs (31.5 ± 1.6 kg of body weight and 11 weeks of age; Landrace × Yorkshire) and five mini-JINP (31.0 ± 3.2 kg body weight and 20 weeks of age). The pigs were surgically equipped with a T-cannula at the end of ileum. Each pig breed was assigned to 5 dietary treatments in a 5 × 10 incomplete Latin square design with 10 periods. Four experimental diets were formulated to contain each of soybean meal, corn gluten feed, copra meal, and sesame expellers as the sole source of nitrogen. A nitrogen-free diet was also prepared to determine basal endogenous losses of CP and AA. No interaction between breed and feed ingredient was observed for the digestibility of CP and all indispensable AA. The SID of CP and all indispensable AA, except Arg, His, and Lys, did not differ between the two breeds of pigs. Prediction equations were developed for SID of CP and AA of commercial pigs using the SID values of mini-JINP: SID of CP (%) = (1.02 × SID of CP in mini-JINP) - 5.20 with r2 = 0.97 and p < 0.05; SID of Lys (%) = (1.12 × SID of Lys in mini-JINP) - 9.10 with r2 = 0.98 and p < 0.05; and SID of Met (%) = (1.08 × SID of Met in mini-JINP) - 4.27 with r2 = 0.96 and p < 0.05. The digestibility for most AA in feedstuffs for commercial pigs can be estimated using data from mini-JINP.

Use of High-Frequency Ultrasound for the Correlation of Epithelial Rete Peg Variation

OBJECTIVE

Rete pegs are projections of the oral epithelium into connective tissue. Their dimensions change during pathological conditions and may correlate with wound-healing status. Non-invasive, high-frequency ultrasound (US) may be able to capture these changes and aid in early detection of histopathological changes. The aim of this preclinical study is to correlate US images with histology and quantify epithelial layers at different tooth sites.

METHODS

Sagittal B-mode images of mid-facial and interproximal oral soft tissue sites were recorded in a preclinical minipig model using a linear array in second harmonic mode (12/24 MHz). Histology samples from the same locations were stained (hematoxylin and eosin), digitized and registered with US images. Manual annotations were used to measure distances D1 (thickness of epithelium on histology vs. hyperechoic zone on US) and D2 (sum of epithelial thickness and length of rete pegs on histology vs. sum of hyperechoic and hypoechoic zone on US) to statistically analyze them.

RESULTS

Ultrasonic-derived dimensions yielded a mean bias of -0.64 (55% coefficient of variance [COV]: -180 to +180 µm) and -12 µm (39% COV: -260 to +240 µm) for D1 and D2, respectively. Individualized analysis of D1 and D2 by tooth type showed similar tends in the ability to differentiate between epithelium at different tooth locations, on both histology and US.

CONCLUSION

Assessing soft tissue dimensions on a sub-millimeter scale using clinical imaging hardware is still a developing area. Future research might open doors for diagnosis of oral pathologies and abnormal wound healing, and may limit false-positive indications for biopsies.

Periodontal disease as a model to study chronic inflammation in aging

Periodontal disease is a chronic inflammatory condition that results in the destruction of the teeth supporting tissues, eventually leading to the loss of teeth and reduced quality of life. In severe cases, periodontal disease can limit proper nutritional intake, cause acute pain and infection, and cause a withdrawal from social situations due to esthetic and phonetic concerns. Similar to other chronic inflammatory conditions, periodontal disease increases in prevalence with age. Research into what drives periodontal disease pathogenesis in older adults is contributing to our general understanding of age-related chronic inflammation. This review will present periodontal disease as an age-related chronic inflammatory disease and as an effective geroscience model to study mechanisms of age-related inflammatory dysregulation. The current understanding of the cellular and molecular mechanisms that drive inflammatory dysregulation as a function of age will be discussed with a focus on the major pathogenic immune cells in periodontal disease, which include neutrophils, macrophages, and T cells. Research in the aging biology field has shown that the age-related changes in these immune cells result in the cells becoming less effective in the clearance of microbial pathogens, expansion of pathogenic subpopulations, or an increase in pro-inflammatory cytokine secretions. Such changes can be pathogenic and contribute to inflammatory dysregulation that is associated with a myriad of age-related disease including periodontal disease. An improved understanding is needed to develop better interventions that target the molecules or pathways that are perturbed with age in order to improve treatment of chronic inflammatory conditions, including periodontal disease, in older adult populations.

Maximizing insights from nonclinical safety studies in the context of rising costs and changing regulations

The traditional paradigm of non-rodent safety assessment studies, primarily reliant on non-human primates (NHPs) and dogs, is undergoing a transformation. During the 2023 Safety Pharmacology Society Annual Meeting, scientists from leading nonclinical contract organizations discussed how traditional IND-enabling studies can benefit from employing underutilized alternative non-rodent models, such as the swine. Swine offer a cost-effective approach to drug development and share many anatomical and physiological similarities with humans. The inclusion of non-traditional species in safety assessments, coupled with advanced measurement techniques, aids in de-risking compounds early on and adapting projects to the evolving cost landscape.

Efficacy of sintered Zinc-doped fluorapatite scaffold as an antimicrobial regenerative bone filler for dental applications

OBJECTIVES

The objective of this study was to assess whether zinc-doped fluorapatite (ZnFA) could serve as an effective antimicrobial dental bone filler for bone regeneration compared to autografts.

METHODS

FA and 2 % zinc-doped FA (2ZnFA) were synthesized and characterized in-house. Compressed and sintered FA and 2ZnFA disks were incubated with bacteria to assess antimicrobial properties. Adipose-derived stem cells were cultured on these discs to evaluate the surfaces' ability to support cell growth and promote osteogenic differentiation. Surfaces exhibiting the highest expressions of the bone markers osteopontin and osteocalcin were selected for an in vivo study in a rat mandibular defect model. Twenty rats were divided into 5 groups, equally, and a 5 mm surgical defect of the jaw was left untreated or filled with 2ZnFA, FA, autograft, or demineralized bone matrix (DBM). At 12 weeks, the defects and surrounding tissues were harvested and subjected to microCT and histological evaluations.

RESULTS

Standard techniques such as FTIR, ICP-MS, fluoride probe, and XRD revealed the sintered FA and ZnFA's chemical compositions and structures. Bacterial studies revealed no significant differences in surface bacterial adhesion properties between FA and 2ZnFA, but significantly fewer bacterial loads than control titanium discs (p < 0.05). Cell culture data confirmed that both surfaces could support cell growth and promote the osteogenic differentiation of stem cells. MicroCT analysis confirmed statistical similarities in bone regeneration within FA, 2ZnFA, and autograft groups.

CONCLUSION

The data suggests that both FA and 2ZnFA could serve as alternatives to autograft materials, which are the current gold standard. Moreover, these bone fillers outperformed DBM, an allograft material commonly used as a dental bone void filler.

CLINICAL SIGNIFICANCE

The use of FA or 2ZnFA for treating mandibular defects led to bone regeneration statistically similar to autograft repair and significantly outperformed the widely used dental bone filler, DBM. Additional translational research may confirm FA-based materials as superior substitutes for existing synthetic bone fillers, ultimately enhancing patient outcomes.

Treatment of Oral Disease in Eight Pet Pot-Bellied Pigs (Sus scrofa domesticus): A Case Series

Evidence of porcine oral pathology in client-owned domestic pigs has been reported in recent literature. The most common abnormalities are missing teeth and periodontal disease. This case series reviews the diagnosis and treatment of dental disease in 8 pet Vietnamese Pot-Bellied Pigs (Sus scrofa domesticus) over a 6-year period (2015-2021). Inclusion criteria included pigs over 1 year of age that had at least 2 sequential visits involving photographs, full-mouth intraoral radiographs, and dental charting. Eight pigs were identified for study inclusion. The study population included 4 castrated males, 3 spayed females, and 1 intact female. The 8 subjects had a total of 28 visits. Fifty-five intraoral dental extractions were performed and complete healing of 44 extraction sites was observed (11 sites were lost to follow up). Canine tooth reduction was performed on 52 tusks in 7 pigs with exposure of 1 pulp that was treated by partial pulpectomy and direct pulp capping. Restoration of carious lesions was performed on 4 teeth. The most commonly extracted teeth were the right and left maxillary first molars (10 of 47 teeth). Reasons for tooth extraction included: periodontal disease, complicated crown fracture, nonvital +/- periapical pathology, and persistent deciduous teeth. Additional treatments ranged from type 1 crown lengthening with restoration of carious lesions, tusk trimming, closed and open root planing, dental extractions, ultrasonic scaling, and polishing. This article stresses the importance of routine dental healthcare and early intervention for periodontal disease in pigs.

Challenges and Pitfalls of Research Designs Involving Magnesium-Based Biomaterials: An Overview

Magnesium-based biomaterials hold remarkable promise for various clinical applications, offering advantages such as reduced stress-shielding and enhanced bone strengthening and vascular remodeling compared to traditional materials. However, ensuring the quality of preclinical research is crucial for the development of these implants. To achieve implant success, an understanding of the cellular responses post-implantation, proper model selection, and good study design are crucial. There are several challenges to reaching a safe and effective translation of laboratory findings into clinical practice. The utilization of Mg-based biomedical devices eliminates the need for biomaterial removal surgery post-healing and mitigates adverse effects associated with permanent biomaterial implantation. However, the high corrosion rate of Mg-based implants poses challenges such as unexpected degradation, structural failure, hydrogen evolution, alkalization, and cytotoxicity. The biocompatibility and degradability of materials based on magnesium have been studied by many researchers in vitro; however, evaluations addressing the impact of the material in vivo still need to be improved. Several animal models, including rats, rabbits, dogs, and pigs, have been explored to assess the potential of magnesium-based materials. Moreover, strategies such as alloying and coating have been identified to enhance the degradation rate of magnesium-based materials in vivo to transform these challenges into opportunities. This review aims to explore the utilization of Mg implants across various biomedical applications within cellular (in vitro) and animal (in vivo) models.

A labeling study of dentin formation rates during crown and root growth of porcine mandibular first molars

We used fluorochrome labeling to study spatiotemporal variation of dentin apposition (DAR) and extension (DER) rates during crown and root formation of mandibular first molars from wild boar and domestic pigs. DAR was reconstructed along the course of dentinal tubules in four zones of the crown and in the upper root area. In all five zones, mean DAR increased during the first 30% to 40% of apposition, reaching highest values (22-23 μm/day) in the upper-lateral crown zone. Lowest values were recorded near the dentin-pulp interface (DPI). Typically, DARs in contemporaneously formed dentin areas were higher in more cuspally compared to more cervically/apically located zones. DER was high (>200 μm/day) in early postnatal crown dentin and then decreased markedly in cervical direction, with lowest values in the cervical crown zone. After this nadir, DER sharply increased in the upper 30% to 40% of the root extension, reaching values equaling (wild boar) or even surpassing (domestic pigs) those recorded in the upper lateral crown. After this peak, DER again decreased. While DAR did not differ markedly between wild boar and domestic pigs, the DER showed marked differences, both regarding maximum values (208.1 μm/day in wild boar, 272.2 μm/day in domestic pigs) and the timing of the root growth spurt, which occurred earlier in the domestic pigs. We consider the more rapid recruitment of secretory odontoblasts in domestic pigs (reflected by higher DER) a side effect of selection for rapid body growth during pig domestication.

Regeneration of alveolar bone defects in the experimental pig model: A systematic review and meta-analysis

OBJECTIVE

Pigs are emerging as a preferred experimental in vivo model for bone regeneration. The study objective was to answer the focused PEO question: in the pig model (P), what is the capacity of experimental alveolar bone defects (E) for spontaneous regeneration in terms of new bone formation (O)?

METHODS

Following PRISMA guidelines, electronic databases were searched for studies reporting experimental bone defects or extraction socket healing in the maxillae or mandibles of pigs. The main inclusion criteria were the presence of a control group of untreated defects/sockets and the assessment of regeneration via 3D tomography [radiographic defect fill (RDF)] or 2D histomorphometry [new bone formation (NBF)]. Random effects meta-analyses were performed for the outcomes RDF and NBF.

RESULTS

Overall, 45 studies were included reporting on alveolar bone defects or extraction sockets, most frequently in the mandibles of minipigs. Based on morphology, defects were broadly classified as 'box-defects' (BD) or 'cylinder-defects' (CD) with a wide range of healing times (10 days to 52 weeks). Meta-analyses revealed pooled estimates (with 95% confidence intervals) of 50% RDF (36.87%-63.15%) and 43.74% NBF (30.47%-57%) in BD, and 44% RDF (16.48%-71.61%) and 39.67% NBF (31.53%-47.81%) in CD, which were similar to estimates of socket-healing [48.74% RDF (40.35%-57.13%) and 38.73% NBF (28.57%-48.89%)]. Heterogeneity in the meta-analysis was high (I2 > 90%).

CONCLUSION

A substantial body of literature revealed a high capacity for spontaneous regeneration in experimental alveolar bone defects of (mini)pigs, which should be considered in future studies of bone regeneration in this animal model.

Animal Models for Investigating Osseointegration: An Overview of Implant Research over the Last Three Decades

Dental implants and bone augmentation are among dentistry's most prevalent surgical treatments; hence, many dental implant surfaces and bone grafts have been researched to improve bone response. Such new materials were radiologically, histologically, and histomorphometrically evaluated on animals before being used on humans. As a result, several studies used animals to evaluate novel implant technologies, biocompatibility, surgical techniques, and osseointegration strategies, as preclinical research on animal models is essential to evaluate bioactive principles (on cells, compounds, and implants) that can act through multiple mechanisms and to predict animal behavior, which is difficult to predict from in vitro studies alone. In this study, we critically reviewed all research on different animal models investigating the osseointegration degree of new implant surfaces, reporting different species used in the osseointegration research over the last 30 years. Moreover, this is the first study to summarize reviews on the main animal models used in the translational research of osseointegration, including the advantages and limitations of each model and determining the ideal location for investigating osseointegration in small and large animal models. Overall, each model has advantages and disadvantages; hence, animal selection should be based on the cost of acquisition, animal care, acceptability to society, availability, tolerance to captivity, and housing convenience. Among small animal models, rabbits are an ideal model for biological observations around implants, and it is worth noting that osseointegration was discovered in the rabbit model and successfully applied to humans.

Induction of Hepatocellular Carcinoma in Conventional Domestic Swine Using N-Diethylnitrosamine and Phenobarbital

Purpose

Large animal models are still used in many studies because of their likeness to humans. It has not been documented that regular-sized conventional farm-breed pigs, generally bred for meat production, can be used to generate hepatocellular carcinoma (HCC) animal models. The goal of this study was to investigate how N-diethylnitrosamine (DENA) and phenobarbital (PB) together can generate HCC in ordinary farmed pigs.

Materials and Methods

Conventional domestic swine (Sus scrofa domesticus) were used. DENA 15 mg/kg was intraperitoneally injected weekly for 12 weeks, while PB tablets (4 mg/kg) were also administered through food for 16 weeks. Blood testing and ultrasonography evaluation were performed to monitor the progress. Subsequently, computed tomography was conducted in cases with suspected nodules, followed by histopathological examination to confirm the diagnosis.

Results

Ten swine (seven males, three females; age: 2 months; weight: 9-15 kg) were included in the study and followed up for 25 months; nine were experimental, and one was control for ethical considerations. The maximum weight of animals during this study reached 162-228 kg. The weight gain seen in the intervention swine was predominantly lower than that documented in the control. The laboratory analysis revealed no notable abnormalities in liver function markers but did demonstrate statistically significant changes in urea (p = 0.028) and creatinine (p = 0.003) levels. Ultrasonography and computed tomography showed multiple liver nodules with characteristics resembling HCC. Serial imaging screening and more extended observations revealed that all animals eventually developed tumors. Histopathological confirmation at 15-22 weeks post-induction revealed that all intervened swine developed multiple nodules of well-differentiated HCC and some with hepatic angiosarcoma.

Conclusion

This study successfully generated HCC in conventional domestic swine with a DENA and PB combination. This investigation required at least 15 months to develop tumors. This model will be beneficial for future investigations of HCC in large animals.

Advancements in Periodontal Regeneration: A Comprehensive Review of Stem Cell Therapy

Periodontal disease, characterized by inflammation and infection of the supporting structures of teeth, presents a significant challenge in dentistry and public health. Current treatment modalities, while effective to some extent, have limitations in achieving comprehensive periodontal tissue regeneration. This comprehensive review explores the potential of stem cell therapy in advancing the field of periodontal regeneration. Stem cells, including mesenchymal stem cells (MSCs) and induced pluripotent stem cells (iPSCs), hold promise due to their immunomodulatory effects, differentiation potential into periodontal tissues, and paracrine actions. Preclinical studies using various animal models have revealed encouraging outcomes, though standardization and long-term assessment remain challenges. Clinical trials and case studies demonstrate the safety and efficacy of stem cell therapy in real-world applications, especially in personalized regenerative medicine. Patient selection criteria, ethical considerations, and standardized treatment protocols are vital for successful clinical implementation. Stem cell therapy is poised to revolutionize periodontal regeneration, offering more effective, patient-tailored treatments while addressing the systemic health implications of periodontal disease. This transformative approach holds the potential to significantly impact clinical practice and improve the overall well-being of individuals affected by this prevalent oral health concern. Responsible regulatory compliance and a focus on ethical considerations will be essential as stem cell therapy evolves in periodontal regeneration.

Exploring the Use of Animal Models in Craniofacial Regenerative Medicine: A Narrative Review

The craniofacial region contains skin, bones, cartilage, the temporomandibular joint (TMJ), teeth, periodontal tissues, mucosa, salivary glands, muscles, nerves, and blood vessels. Applying tissue engineering therapeutically helps replace lost tissues after trauma or cancer. Despite recent advances, it remains essential to standardize and validate the most appropriate animal models to effectively translate preclinical data to clinical situations. Therefore, this review focused on applying various animal models in craniofacial tissue engineering and regeneration. This research was based on PubMed, Scopus, and Google Scholar data available until January 2023. This study included only English-language publications describing animal models' application in craniofacial tissue engineering (in vivo and review studies). Study selection was based on evaluating titles, abstracts, and full texts. The total number of initial studies was 6454. Following the screening process, 295 articles remained on the final list. Numerous in vivo studies have shown that small and large animal models can benefit clinical conditions by assessing the efficacy and safety of new therapeutic interventions, devices, and biomaterials in animals with similar diseases/defects to humans. Different species' anatomical, physiologic, and biological features must be considered in developing innovative, reproducible, and discriminative experimental models to select an appropriate animal model for a specific tissue defect. As a result, understanding the parallels between human and veterinary medicine can benefit both fields.

Effective Modalities of Periodontitis Induction in Rat Model

Induction of periodontal disease using the rat model is the preferred model for human periodontal disease studies that are related to gene expression, mechanisms of inflammatory regulation, microbial and host responses, resolution, and the healing process. There are 3 methods that are frequently used to induce periodontal disease, which are: ligature application, oral bacterial inoculation, and the lipopolysaccharide injection technique. In the ligature model, sterile non-absorbable sutures or orthodontic wires are widely used to induce local irritation and bacterial plaque accumulation. Secondly, mono and mixed cultures of periodontal bacteria are inoculated orally by gavage or topical application. Lastly, lipopolysaccharide extracted from pathogenic bacteria can be directly injected into the gingival sulcus to induce inflammation and stimulate osteoclastogenesis and alveolar bone loss. Among these methods, ligature application induces inflammation and alveolar bone resorption more promptly compared to other methods. This review will provide an overview of the main induction methods in experimental periodontal disease, with their advantages and disadvantages.

A Computed Tomographic Study of the Premolar Teeth of Babyrousa spp

A photographic and computed tomography (CT) scanning study was carried out on the premolar teeth of 18 adult male Babyrousa babyrussa skulls, 10 skulls of Babyrousa celebensis, including 6 adult males, 1 adult female, 1 subadult male, 1 subadult female, and 1 juvenile male. The occlusal morphology of the permanent maxillary premolar teeth of B. babyrussa was very similar to that of B. celebensis. Almost all the maxillary third premolar teeth (107/207) had 2 roots, whereas maxillary fourth premolar teeth (108/208) had 3 or 4 roots. All of the mesial tooth roots of 107/207 and 108/208 were tapering rod-like structures; each contained a single pulp canal. Almost all distal roots of 107/207 were "C" shaped and contained 2 pulp canals. The 108/208 palatal roots were "C" shaped and contained 2 pulp canals. The mesial and distal roots of the mandibular third premolar teeth (307/407) teeth were uniformly rod-like, as were the mesial roots of the mandibular fourth premolar teeth (308/408) teeth. The distal roots of the 308/408 teeth were "C" shaped. All B. babyrussa 307/407 teeth have a single pulp canal located in each of the mesial and distal roots. The 308/408 mesial tooth root contained 1 pulp canal. In all but 3 of the 36 distal 308/408 roots of B. babyrussa teeth and in 7 of the 14 distal roots of B. celebensis teeth there was a single pulp canal; in the other 7 teeth there were 2 pulp canals. Each of the 3 medial roots contained 1 pulp canal.

Metalloproteinases in Restorative Dentistry: An In Silico Study toward an Ideal Animal Model

In dentistry, various animal models are used to evaluate adhesive systems, dental caries and periodontal diseases. Metalloproteinases (MMPs) are enzymes that degrade collagen in the dentin matrix and are categorized in over 20 different classes. Collagenases and gelatinases are intrinsic constituents of the human dentin organic matrix fibrillar network and are the most abundant MMPs in this tissue. Understanding such enzymes' action on dentin is important in the development of approaches that could reduce dentin degradation and provide restorative procedures with extended longevity. This in silico study is based on dentistry's most used animal models and intends to search for the most suitable, evolutionarily close to Homo sapiens. We were able to retrieve 176,077 mammalian MMP sequences from the UniProt database. These sequences were manually curated through a three-step process. After such, the remaining 3178 sequences were aligned in a multifasta file and phylogenetically reconstructed using the maximum likelihood method. Our study inferred that the animal models most evolutionarily related to Homo sapiens were Orcytolagus cuniculus (MMP-1 and MMP-8), Canis lupus (MMP-13), Rattus norvegicus (MMP-2) and Orcytolagus cuniculus (MMP-9). Further research will be needed for the biological validation of our findings.

Spatiotemporal expression of fibroblast growth factor 4 and 10 during the morphogenesis of deciduous molars in miniature pigs

OBJECTIVE

Fibroblast growth factors (FGFs) play pivotal roles in mediating interactions between dental epithelium and mesenchyme throughout tooth initiation and morphogenesis. This study aimed to elucidate the roles of FGF4 and FGF10 in the regulation of tooth development.

DESIGN

In this study, we investigated spatiotemporal expression patterns of FGF4 and FGF10 in the third deciduous molars (DM3) of miniature pigs at the cap, early bell, and late bell stages. Pregnant miniature pigs were obtained, and the samples were processed for histological staining. Non-radioactive in situ hybridization, immunohistochemistry, and real-time PCR were used to detect mRNA and protein expression levels of FGF4 and FGF10.

RESULTS

FGF4 was expressed in the dental epithelium and mesenchyme at the cap stage. At the early bell stage, epithelial expression of FGF4 was reduced while mesenchymal expression got stronger. At the late bell stage, the FGF4 expression was restricted to the inner enamel epithelium (IEE) and differentiating odontoblasts. FGF10 was expressed intensely in both epithelium and mesenchyme at the cap stage. The expression of FGF10 was concentrated in the secondary enamel knots and surrounding mesenchyme at the early bell stage. FGF10 was weakly detected in the IEE by the late bell stage.

CONCLUSIONS

Our results indicated that FGF4 and FGF10 might have partially redundant functions in regulating epithelium morphogenesis. FGF4 may be involved in regulatory signaling cascades mediating interactions between the epithelium and mesenchyme. In addition, the downregulation of FGF10 expression may be associated with the cessation of mesenchymal cell proliferation and initiation of preodontoblast polarization.

Regular medical checkup program (in K-MEDI hub) to enhance the welfare of laboratory dogs and pigs

BACKGROUND

The importance of animal welfare is being recognized worldwide. Recently, the increasing demand for enhanced laboratory animal welfare has led to clinically featured transformations of animal research institutes. This study aims to describe the process and findings of veterinary medical check-ups and its influence on laboratory dogs and pigs welfare. Regular medical checkups were conducted by the attending veterinarian twice a year to ensure the health and welfare of dogs and pigs in our animal research institute. Based on the findings from the medical checkup, we assessed the current health of dogs and pigs,providing reasonable treatments to prevent the risk of complications.

RESULTS

Blood tests and physical examinations revealed clinically relevant findings. Some of these findings were due to insufficient postoperative care after invasive surgical experiments and the remaining were predictable side effects after surgical experiments. However, one finding involved severe gum bleeding due to retained deciduous teeth. This animal was euthanized because it was judged to reach the humane endpoint. Majority of the dogs and pigs at our animal research institute were considered to be healthy, based on the comprehensive results of the medical checkups.

CONCLUSIONS

Regular medical checkups by the attending veterinarian established enhanced animal welfare, ensuring the accuracy and reproducibility of animal studies. This pioneering veterinary animal care program can serve as a potential advanced guideline for animal research institutes to improve dogs and pigs welfare.

Dental implants in large animal models with experimental systemic diseases: A systematic review

This systematic review aims to identify and discuss the most used methodologies in pre-clinical studies for the evaluation of the implementation of dental implants in systemically compromised pigs and sheep. This study provides support and guidance for future research, as well as for the prevention of unnecessary animal wastage and sacrifice. Preferred Reporting for Systematic Reviews and Meta-Analyses (PRISMA) was used as a guideline; electronic searches were performed in PubMed, Scopus, Scielo, Web of Science, Embase, Science Direct, Brazilian Bibliography of Dentistry, Latin American and Caribbean Literature in Health Sciences, Directory of Open Access Journals, Database of Abstracts of Reviews of Effects, and gray literature until January 2022 (PROSPERO/CRD42021270119). Sixty-eight articles were chosen from the 2439 results. Most studies were conducted in pigs, mainly the Göttinger and Domesticus breeds. Healthy animals with implants installed in the jaws were predominant among the pig studies. Of the studies evaluating the effect of systemic diseases on osseointegration, 42% were performed in osteoporotic sheep, 32% in diabetic sheep, and 26% in diabetic pigs. Osteoporosis was primarily induced by bilateral ovariectomy and mainly assessed by X-ray densitometry. Diabetes was induced predominantly by intravenous streptozotocin and was confirmed by blood glucose analysis. Histological and histomorphometric analyses were the most frequently employed in the evaluation of osseointegration. The animal models presented unique methodologies for each species in the studies that evaluated dental implants in the context of systemic diseases. Understanding the most commonly used techniques will help methodological choices and the performance of future studies in implantology.

Anatomic Analysis of Masseteric-to-zygomatic Nerve Transfer in Rat and Pig Models

Background

Nerve transfer from the masseteric branch of the trigeminal nerve is a widely performed procedure for facial reanimation. Despite achieving powerful muscle force, clinical and aesthetic results leave room for improvement. Preclinical animal models are invaluable to establishing new therapeutic approaches. This anatomical study aimed to establish a masseteric-to-zygomatic nerve transfer model in rats and pigs.

Methods

The masseteric branch of the trigeminal nerve and the zygomatic branch of the facial nerve were dissected in 30 swine and 40 rat hemifaces. Both nerves were mobilized and approximated to achieve an overlap between the nerve ends. Over the course of dissecting both nerves, their anatomy, length, and branching pattern were documented. At the coaptation point, diameters of both nerves were measured, and samples were taken for neuromorphometric analysis.

Results

Anatomic details and landmarks were described. Tension-free coaptation was possible in all rat and pig dissections. In rats, the masseteric branch had an average diameter of 0.36 mm (±0.06), and the zygomatic branch average diameter was 0.46 mm (±0.13). In pigs, the masseteric branch measured 0.52 (±0.16) mm and the zygomatic branch, 0.59 (±0.16) mm. No significant differences were found between the diameters and axon counts of both nerves in pigs. In rats, however, their diameters, axon counts, and fascicular areas were significantly different.

Conclusion

Our study demonstrated the feasibility of direct masseteric-to-zygomatic nerve transfer in rats and pigs and provided general anatomic knowledge of both nerves.

Application of metal artifact reduction algorithm for CBCT diagnosis of temporary anchorage device-tooth root contact: inadequate to reduce false-positive rate

OBJECTIVES

It was recently found that when cone beam computed tomography (CBCT) was used to examine temporary anchorage device (TAD)-tooth root contact, it tends to yield high false-positive (FP) diagnoses. This study investigated whether application of a metal artifact reduction (MAR) algorithm or reducing CBCT scan voxel-size can remediate this problem.

METHODS

18 fresh pig cadaver mandibles underwent TAD placement bilaterally at first molar lingual furcation regions. CBCT scans were taken under varied MAR (absence, presence) and voxel-size (400 µm, 200 µm) settings. Then, TADs were removed and a micro-CT scan (27 µm voxel-size) of the TAD placement site was performed. Three raters, blinded of CBCT scan setting, independently diagnosed whether TADs were in contact with roots. The reliability and accuracy of CBCT diagnoses using micro-CT as the gold-standard were statistically examined.

RESULTS

Generally, CBCT diagnoses had intrarater (Cohen's κ: 0.54-1) and interrater (Fleiss' κ: 0.73-0.81) reliability, within the moderate to excellent range, which did not vary with MAR setting or scan voxel-size. For diagnostic accuracy, FP rate among all raters was mostly in the 15-25% range and did not change with MAR or scan voxel-size settings (McNemar tests, p > 0.05) while false-negative rate was relatively minimal and only occurred to one rater (9%).

CONCLUSIONS

When using CBCT to diagnose possible TAD-root contact, applying a currently available Planmeca MAR algorithm or reducing CBCT scan voxel-size from 400 µm to 200 µm may not decrease FP rate. Further optimization of the MAR algorithm for this purpose may be needed.

Permanent Tooth Eruption Patterns in Nigerian Local Pigs

Pigs are diphyodonts with heterodont dentition and have been used in studies involving teeth and jawbone regeneration, and dental implants. Patterns of tooth eruption are used to age animals and determine the effects of environmental and genetic influences on occurrence of variations. As with other species, variations exist in the tooth eruption pattern in pigs. The aim of this study was to determine the permanent teeth eruption patterns of Nigerian local pigs. Twenty-six healthy pigs were observed throughout the study period. Pigs were firmly held in dorsal or lateral recumbency and their mouths gently held open to visually examine all quadrants of the dental arches (right and left maxillary, right and left mandibular). Observations were recorded from 16 weeks of age, until the last permanent tooth erupted. Results obtained from the study showed that males had lower mean values for eruption time (54%) of examined teeth in comparison to females. The mean values of eruption time for the maxillary third incisor, the mandibular and maxillary canines, and the mandibular fourth premolar teeth were statistically significant in the males (P = .0017, P = .0088, P = .0002 and P = .0244, respectively). Sixty-nine percent of the adult pigs did not have eruption of the mandibular first premolar, while polydontia was observed in the maxillary and mandibular incisors. These results show that intra-breed and inter-breed variations exist in the dental eruption pattern in pigs. The data obtained from this study can be used for comparative dental studies and can aid further research on the developmental anatomy of Nigerian local pigs.

Salivary gland regeneration: from salivary gland stem cells to three-dimensional bioprinting

Hyposalivation and severe dry mouth syndrome are the most common complications in patients with head and neck cancer (HNC) after receiving radiation therapy. Conventional treatment for hyposalivation relies on the use of sialogogues such as pilocarpine; however, their efficacy is constrained by the limited number of remnant acinar cells after radiation. After radiotherapy, the salivary gland (SG) secretory parenchyma is largely destroyed, and due to the reduced stem cell niche, this gland has poor regenerative potential. To tackle this, researchers must be able to generate highly complex cellularized 3D constructs for clinical transplantation via technologies, including those that involve bioprinting of cells and biomaterials. A potential stem cell source with promising clinical outcomes to reserve dry mouth is adipose mesenchymal stem cells (AdMSC). MSC-like cells like human dental pulp stem cells (hDPSC) have been tested in novel magnetic bioprinting platforms using nanoparticles that can bind cell membranes by electrostatic interaction, as well as their paracrine signals arising from extracellular vesicles. Both magnetized cells and their secretome cues were found to increase epithelial and neuronal growth of in vitro and ex vivo irradiated SG models. Interestingly, these magnetic bioprinting platforms can be applied as a high-throughput drug screening system due to the consistency in structure and functions of their organoids. Recently, exogenous decellularized porcine ECM was added to this magnetic platform to stimulate an ideal environment for cell tethering, proliferation, and/or differentiation. The combination of these SG tissue biofabrication strategies will promptly allow for in vitro organoid formation and establishment of cellular senescent organoids for aging models, but challenges remain in terms of epithelial polarization and lumen formation for unidirectional fluid flow. Current magnetic bioprinting nanotechnologies can provide promising functional and aging features to in vitro craniofacial exocrine gland organoids, which can be utilized for novel drug discovery and/or clinical transplantation.

Thirty years of telemetry-based data acquisition for cardiovascular drug safety evaluation: Applications and optimization

Conducting safety evaluations of new drugs using conscious animals has been a specialty of our working group for thirty years. In this article, we review the various technical challenges and solutions dealt with over the years to improve both the data quality and the well being of our animal subjects. Of particular interest for us has been the use of telemetry-based data acquisition for conducting studies on cardiovascular (CV) function. This includes the evolving technical aspects of the studies, as well as the development of new applications that take advantage of this technical approach.

Detailed anatomical study of the peripheral motor branches of the facial nerve in the swine model: A novel investigative approach for facial paralysis research

INTRODUCTION

Large animal models aid in innovating surgical approaches and developing medical devices for the treatment of facial paralysis. However, there is a lack of information on facial nerve anatomy in swine. This study aimed to investigate the branching pattern and histologic characteristics of the swine facial nerve, thereby establishing the anatomical patterns of preclinical models in facial paralysis research.

MATERIAL AND METHODS

The five peripheral motor branches of the facial nerve were dissected in 30 hemifaces of fresh swine cadavers. Starting at the stylomastoid foramen, the course, branching pattern, and diameter of each motor branch was recorded. Samples were taken at the start of each branch for epoxy embedding, toluidine blue staining, and histomorphologic analysis.

RESULTS

The dissections demonstrated consistent anatomy of the buccal and marginal mandibular branches in contrast to the temporal and zygomatic branches, which showed more variation in branching patterns. The buccal branch had the largest mean diameter of 1.34 mm (± 0.26 mm), whereas the marginal mandibular branch had the largest fascicular area of 0.558 mm² (± 0.12 mm²) and highest axon count of 3636.35 (± 526.36). The zygomatic branch had both the smallest diameter of 0.74 mm (± 0.25 mm) and fascicular area of 0.187 mm² (± 0.14 mm²).

CONCLUSIONS

The swine facial nerve is anatomically similar to the human facial nerve, making the pig a suitable large animal model. Detailed anatomical and histological information is crucial for developing preclinical models of novel facial nerve reconstruction approaches.

Dental Disorders in Wild and Domestic Pigs (Sus Scrofa): A Review

Teeth in the mouth of vertebrates represent the modified descendants of bony dermal plates of ancestral fishes. Dental disorders, which are deviations of dental tissues origins, are derived from any or all of the dental tissues; enamel, dentin or cementum, and include dental abnormalities and diseases. These disorders can be influenced by genetic or environmental factors, or an interplay of both factors. This article reviews disorders that have been reported in both wild and domestic pigs and the frequency of occurrence of these conditions.

A 3D-Bioprinted Functional Module Based on Decellularized Extracellular Matrix Bioink for Periodontal Regeneration

Poor fiber orientation and mismatched bone-ligament interface fusion have plagued the regeneration of periodontal defects by cell-based scaffolds. A 3D bioprinted biomimetic periodontal module is designed with high architectural integrity using a methacrylate gelatin/decellularized extracellular matrix (GelMA/dECM) cell-laden bioink. The module presents favorable mechanical properties and orientation guidance by high-precision topographical cues and provides a biochemical environment conducive to regulating encapsulated cell behavior. The dECM features robust immunomodulatory activity, reducing the release of proinflammatory factors by M1 macrophages and decreasing local inflammation in Sprague Dawley rats. In a clinically relevant critical-size periodontal defect model, the bioprinted module significantly enhances the regeneration of hybrid periodontal tissues in beagles, especially the anchoring structures of the bone-ligament interface, well-aligned periodontal fibers, and highly mineralized alveolar bone. This demonstrates the effectiveness and feasibility of 3D bioprinting combined with a dental follicle-specific dECM bioink for periodontium regeneration, providing new avenues for future clinical practice.

Type-2 epithelial-mesenchymal transition in oral mucosal nonneoplastic diseases

The oral mucosa is a membranous structure comprising epithelial and connective tissue that covers the oral cavity. The oral mucosa is the first immune barrier to protect the body against pathogens for systemic protection. It is frequently exposed to mechanical abrasion, chemical erosion, and pathogenic invasion, resulting in oral mucosal lesions, particularly inflammatory diseases. Epithelial-mesenchymal transition (EMT) is a crucial biological process in the pathogenesis of oral mucosal disorders, which are classified into three types (types 1, 2, and 3) based on their physiological consequences. Among these, type-2 EMT is crucial in wound repair, organ fibrosis, and tissue regeneration. It causes infectious and dis-infectious immunological diseases, such as oral lichen planus (OLP), oral leukoplakia, oral submucosal fibrosis, and other precancerous lesions. However, the mechanism and cognition between type-2 EMT and oral mucosal inflammatory disorders remain unknown. This review first provides a comprehensive evaluation of type-2 EMT in chronically inflammatory oral mucosal disorders. The aim is to lay a foundation for future research and suggest potential treatments.

Periodontal Stem Cells Synthesize Maresin Conjugate in Tissue Regeneration 3

Periodontal disease is a significant public health problem worldwide. Excess unresolved chronic inflammation destroys the periodontal tissues that surround and support the teeth, and efforts to control inflammation by removal of bacterial deposits on the teeth have limited long-term impact. Likewise, procedures aimed at regeneration of the periodontal tissues have shown limited success. Recent advances in stem cell research have shown promising novel prospects for the use of periodontal ligament stem cells (PDLSCs) in tissue regeneration; however, control of inflammation remains a barrier. Human PDLSCs have been shown to release specialized proresolving lipid mediators (SPMs) that modulate the immune response and promote resolution of inflammation, tissue repair, and regeneration. Studies on stem cell biology in periodontology have also been limited by the lack of a good large animal model. Herein, we describe PDLSC biology of the Yorkshire pig (pPDLSCs). pPDLSCs were isolated and characterized. Using lipid mediator profiling, we demonstrate for the first time that pPDLSCs biosynthesize cysteinyl-containing SPMs (cys-SPMs), specifically, maresin conjugates in tissue regeneration 3 (MCTR3) and its authentication using liquid chromatography/tandem mass spectrometry. The exogenous addition of the n-3 precursor docosahexaenoic acid enhances MCTR3 biosynthesis. Using immunocytochemistry, we show that pPDLSCs express 4 of the SPM biosynthetic pathway enzymes necessary for SPM biosynthesis, including 5-lipoxygenase, 12-lipoxygenase, and 15-lipoxygenase-1. In addition, we identified and quantified the cytokine/chemokine profile of pPDLSCs using a 13-plex immunology multiplex assay and found that the pretreatment of pPDLSCs with MCTR3 in an inflammatory environment reduced the production of acute and chronic proinflammatory cytokines/chemokines. Together, these results suggest that enhancing resolution of inflammation pathways and mediators may be a possible key early event in predictable periodontal regeneration.

The sialodynamic test: A preliminary porcine head study

Objectives

To provide a concept of measuring pressure changes under constant fluid infusion for the diagnosis of sialolithiasis, termed the sialodynamic test, in a porcine head model.

Methods

Using a porcine head model, a constant infusion of water into the submandibular gland of the two groups over 30 s was performed and the outlet pressure was measured. Metal beads were inserted into the salivary duct for obstruction simulation after the normal submandibular gland sialodynamic measurements were completed. Statistical analyses were performed to evaluate the differences between the measured individuals and the experimental group (n = 3).

Results

The results showed no significant difference between individuals in the control group, but intergroup variation was noted in the simulated sialolithiasis group. The volume-dependent linear increase in pressure was exacerbated in the simulated sialolithiasis group compared with the control.

Conclusion

This study indicated that evaluating the relationship between pressure and volume changes can help to determine whether stones are present in the submandibular gland. The sialodynamic test might serve as a potential diagnostic method for salivary diseases.

The optimization of ligature/bone defect-induced periodontitis model in rats

The destruction of alveolar bone is a crucial manifestation of severe chronic periodontitis, which stem cell-based bioengineered therapies are expected to cure. Therefore, a cost-effective, reproducible, quantifiability and easier to administrate animal model that mimics human periodontitis is of great importance for further endeavor. In this study, we created periodontitis rat models in silk ligation group, bone defect group and bone defect/silk ligation group, respectively. Obvious periodontal inflammation but slight alveolar bone resorption was observed in the ligation group, while surgical trauma was not robust enough to continually worsen the constructed bone defect area in the bone defect group. In the bone defect/ligature group, significant and stable periodontal inflammation was the most enduring with similar evolving pathological patterns of human periodontitis. It also exhibited enhanced clinical similarity and confirmed its superiority in quantitativeness. The present rat model is the first study to reproduce a pathological process similar to human periodontitis with reliable stability and repeatability, manifesting a priority to previous methods. Day 9-12 is the best time for reproducing severe periodontitis syndromes with vertical bone resorption in this model.

Photoacoustic imaging of posterior periodontal pocket using a commercial hockey-stick transducer

SIGNIFICANCE

Photoacoustic imaging has shown advantages over the periodontal probing method in measuring the periodontal probing depth, but the large size of conventional photoacoustic transducers prevents imaging of the more posterior teeth.

AIM

Our aim is to develop a photoacoustic imaging system to image the more posterior periodontal pocket.

APPROACH

We report a clinical "hockey-stick"-style transducer integrated with fibers for periodontal photoacoustic imaging. Cuttlefish ink labeled the periodontal pocket as the photoacoustic contrast agent.

RESULTS

We characterized the imaging system and then measured the pocket depth of 35 swine teeth. Three raters evaluated the performance of the hockey-stick transducer. The measurements between the Williams probing (gold standard) and the photoacoustic methods were blinded but highly correlated. We showed a bias of ∼0.3  mm for the imaging-based technique versus Williams probing. The minimum inter-reliability was over 0.60 for three different raters of varying experience, suggesting that this approach to measure the periodontal pocket is reproducible. Finally, we imaged three pre-molars of a human subject. We could access more upper and posterior teeth than conventional linear transducers.

CONCLUSIONS

The unique angle shape of the hockey-stick transducer allows it to image more posterior teeth than regular linear transducers. This study demonstrated the ability of a hockey-stick transducer to measure the periodontal pocket via photoacoustic imaging.

A Porcine Model Using Adipose Stem Cell-Loaded Scaffolds for Alveolar Ridge Augmentation

Tooth loss greatly affects a person's quality of life and many turn to dental implants to replace lost teeth. The success of a dental implant depends on the amount of alveolar bone supporting the implant, and thus, bone augmentation is often necessary to preserve or build up bone volume in the alveolar ridge. Bone can be augmented with autogenous bone, allografts, or xenografts, but the limitations of such natural bone grafts prompt researchers to develop synthetic scaffolds supplemented with cells and/or bioactive agents as alternative bone grafts. The translation of these combination scaffolds from the laboratory to the clinic requires reliable experimental models that can simulate the clinical conditions in human patients. In this article, we describe the use of a porcine alveolar defect model as a platform to evaluate the efficacy of a novel combination of a three-dimensional-printed polycaprolactone-tricalcium phosphate (PCL-TCP) scaffold and adipose-derived mesenchymal stem cells (AD-MSCs) in lateral alveolar augmentation. The surgical protocol for the defect creation and regenerative surgery, as well as analytical methods to determine the extent of tissue regeneration, are described and discussed.

Bone Union Quality after Fracture Fixation of Mandibular Head with Compression Magnesium Screws

For some years now, fixation devices created with resorbable magnesium alloys for the mandibular head have been clinically available and are beginning to be used. It is thus valuable to evaluate the quality of unions in these cases. The aim of this study was radiological comparison of magnesium versus titanium open reduction and rigid fixations in the mandible condylar head. Thirty-one patients were treated for fractures of the mandibular head with magnesium WE43 alloy headless compression screws (diameter 2.3 mm) and, as a reference group, 29 patients were included with similar construction titanium screws (diameter 1.8 mm). The 12-month results of the treatment were evaluated by the texture analysis of CT. Near similar treatment results were found with magnesium screws in traditional titanium fixation. Magnesium screws result in a higher density of the bone structure in the mandibular head. Conclusions: The quantitative evaluation of bone union after surgical treatment of mandibular head fracture with magnesium compression headless screws indicates that stable consolidation was achieved. Undoubtedly, the resorption process of the screws was found to be incomplete after 12 months, evidenced by a marked densification of the bone structure at the fracture site.

The de novo assembly of a European wild boar genome revealed unique patterns of chromosomal structural variations and segmental duplications

The rapid progress of sequencing technology has greatly facilitated the de novo genome assembly of pig breeds. However, the assembly of the wild boar genome is still lacking, hampering our understanding of chromosomal and genomic evolution during domestication from wild boars into domestic pigs. Here, we sequenced and de novo assembled a European wild boar genome (ASM2165605v1) using the long‐range information provided by 10× Linked‐Reads sequencing. We achieved a high‐quality assembly with contig N50 of 26.09 Mb. Additionally, 1.64% of the contigs (222) with lengths from 107.65 kb to 75.36 Mb covered 90.3% of the total genome size of ASM2165605v1 (~2.5 Gb). Mapping analysis revealed that the contigs can fill 24.73% (93/376) of the gaps present in the orthologous regions of the updated pig reference genome (Sscrofa11.1). We further improved the contigs into chromosome level with a reference‐assistant scaffolding method. Using the ‘assembly‐to‐assembly’ approach, we identified intra‐chromosomal large structural variations (SVs, length >1 kb) between ASM2165605v1 and Sscrofa11.1 assemblies. Interestingly, we found that the number of SV events on the X chromosome deviated significantly from the linear models fitting autosomes (R² > 0.64, p < 0.001). Specifically, deletions and insertions were deficient on the X chromosome by 66.14 and 58.41% respectively, whereas duplications and inversions were excessive on the X chromosome by 71.96 and 107.61% respectively. We further used the large segmental duplications (SDs, >1 kb) events as a proxy to understand the large‐scale inter‐chromosomal evolution, by resolving parental‐derived relationships for SD pairs. We revealed a significant excess of SD movements from the X chromosome to autosomes (p < 0.001), consistent with the expectation of meiotic sex chromosome inactivation. Enrichment analyses indicated that the genes within derived SD copies on autosomes were significantly related to biological processes involving nervous system, lipid biosynthesis and sperm motility (p < 0.01). Together, our analyses of the de novo assembly of ASM2165605v1 provides insight into the SVs between European wild boar and domestic pig, in addition to the ongoing process of meiotic sex chromosome inactivation in driving inter‐chromosomal interaction between the sex chromosome and autosomes.

The minipig intraoral dental implant model: A systematic review and meta-analysis

OBJECTIVES

The objective of this report was to provide a review of the minipig intraoral dental implant model including a meta-analysis to estimate osseointegration and crestal bone remodeling.

METHODS

A systematic review including PubMed and EMBASE databases through June 2021 was conducted. Two independent examiners screened titles/abstracts and selected full-text articles. Studies evaluating titanium dental implant osseointegration in native alveolar bone were included. A quality assessment of reporting was performed. Random-effects meta-analyses and meta-regressions were produced for bone-implant contact (BIC), first BIC, and crestal bone level.

RESULTS

125 out of 249 full-text articles were reviewed, 55 original studies were included. Quality of reporting was generally low, omissions included animal characteristics, examiner masking/calibration, and sample size calculation. The typical minipig model protocol included surgical extraction of the mandibular premolars and first molar, 12±4 wks post-extraction healing, placement of three narrow regular length dental implants per jaw quadrant, submerged implant healing and 8 wks of osseointegration. Approximately 90% of studies reported undecalcified incandescent light microscopy histometrics. Overall, mean BIC was 59.88% (95%CI: 57.43-62.33). BIC increased significantly over time (p<0.001): 40.93 (95%CI: 34.95-46.90) at 2 wks, 58.37% (95%CI: 54.38-62.36) at 4 wks, and 66.33% (95%CI: 63.45-69.21) beyond 4 wks. Variability among studies was mainly explained by differences in observation interval post-extraction and post-implant placement, and implant surface. Heterogeneity was high for all studies (I2 > 90%, p<0.001).

CONCLUSIONS

The minipig intraoral dental implant model appears to effectively demonstrate osseointegration and alveolar bone remodeling similar to that observed in humans and canine models.

Transplantation of Mature Adipocyte-Derived Dedifferentiated Fat Cells Facilitates Periodontal Tissue Regeneration of Class II Furcation Defects in Miniature Pigs

Adipose tissue is composed mostly of adipocytes that are in contact with capillaries. By using a ceiling culture method based on buoyancy, lipid-free fibroblast-like cells, also known as dedifferentiated fat (DFAT) cells, can be separated from mature adipocytes with a large single lipid droplet. DFAT cells can re-establish their active proliferation ability and transdifferentiate into various cell types under appropriate culture conditions. Herein, we sought to compare the regenerative potential of collagen matrix alone (control) with autologous DFAT cell-loaded collagen matrix transplantation in adult miniature pigs (microminipigs; MMPs). We established and transplanted DFAT cells into inflammation-inducing periodontal class II furcation defects. At 12 weeks after cell transplantation, a marked attachment gain was observed based on the clinical parameters of probing depth (PD) and clinical attachment level (CAL). Additionally, micro computed tomography (CT) revealed hard tissue formation in furcation defects of the second premolar. The cemento-enamel junction and alveolar bone crest distance was significantly shorter following transplantation. Moreover, newly formed cellular cementum, well-oriented periodontal ligament-like fibers, and alveolar bone formation were observed via histological analysis. No teratomas were found in the internal organs of recipient MMPs. Taken together, these findings suggest that DFAT cells can safely enhance periodontal tissue regeneration.

Spatiotemporal Expression Patterns of Critical Genes Involved in FGF Signaling During Morphogenesis and Odontogenesis of Deciduous Molars in Miniature Pigs

The fibroblast growth factor (FGF) pathway plays an important role in epithelial-mesenchymal interactions during tooth development. Nevertheless, how the ligands, receptors, and antagonists of the FGF pathway are involved in epithelial-mesenchymal interactions remains largely unknown. Miniature pigs exhibit tooth anatomy and replacement patterns like those in humans and hence can serve as large animal models. The present study investigated the spatiotemporal expression patterns of critical genes encoding FGF ligands (FGF3, FGF4, FGF7, and FGF9), antagonists (SPRY2 and SPRY4) and receptors (FGFR1, FGFR2, and FGFR3) in the third deciduous molars of miniature pigs at the cap (embryonic day 40, E40), early bell (E50), and late bell (E60) stages. The results of in situ hybridization (ISH) with tyramide signal amplification and of qRT-PCR analysis revealed increased expression of FGF7, FGFR1, FGFR2, and SPRY4 in dental epithelium and of FGF7 and FGFR1 in mesenchyme from E40 to E50. In contrast, the results revealed decreased expression of FGF3, FGF4, FGF9, and FGFR3 in dental epithelium and of FGF4, FGF9, FGFR2, and FGFR3 in the mesenchyme from E40 to E60. Mesenchyme signals of FGF3, FGF4, FGF7, SPRY2, FGFR2, and FGFR3 were concentrated in the odontoblast layer from E50 to E60. The distinct expression patterns of these molecules indicated elaborate regulation during dental morphogenesis. Our results provide a foundation for further investigation into fine-tuning dental morphogenesis and odontogenesis by controlling interactions between dental epithelium and mesenchyme, thus promoting tooth regeneration in large mammals.

Integrated analysis of DNA methylome and transcriptome reveals the differences in biological characteristics of porcine mesenchymal stem cells

BACKGROUND

Bone marrow (BM) and umbilical cord (UC) are the main sources of mesenchymal stem cells (MSCs). These two MSCs display significant differences in many biological characteristics, yet the underlying regulation mechanisms of these cells remain largely unknown.

RESULTS

BMMSCs and UCMSCs were isolated from inbred Wuzhishan miniature pigs and the first global DNA methylation and gene expression profiles of porcine MSCs were generated. The osteogenic and adipogenic differentiation ability of porcine BMMSCs is greater than that of UCMSCs. A total of 1979 genes were differentially expressed and 587 genes were differentially methylated at promoter regions in these cells. Integrative analysis revealed that 102 genes displayed differences in both gene expression and promoter methylation. Gene ontology enrichment analysis showed that these genes were associated with cell differentiation, migration, and immunogenicity. Remarkably, skeletal system development-related genes were significantly hypomethylated and upregulated, whereas cell cycle genes were opposite in UCMSCs, implying that these cells have higher cell proliferative activity and lower differentiation potential than BMMSCs.

CONCLUSIONS

Our results indicate that DNA methylation plays an important role in regulating the differences in biological characteristics of BMMSCs and UCMSCs. Results of this study provide a molecular theoretical basis for the application of porcine MSCs in human medicine.

Transient Activation of Hedgehog Signaling Inhibits Cellular Senescence and Inflammation in Radiated Swine Salivary Glands through Preserving Resident Macrophages

Salivary gland function is commonly and irreversibly damaged by radiation therapy for head and neck cancer. This damage greatly decreases the patient’s quality of life and is difficult to remedy. Previously, we found that the transient activation of Hedgehog signaling alleviated salivary hypofunction after radiation in both mouse and pig models through the inhibition of radiation-induced cellular senescence that is mediated by resident macrophages in mouse submandibular glands. Here we report that in swine parotid glands sharing many features with humans, the Hedgehog receptor PTCH1 is mainly expressed in macrophages, and levels of PTCH1 and multiple macrophage markers are significantly decreased by radiation but recovered by transient Hedgehog activation. These parotid macrophages mainly express the M2 macrophage marker ARG1, while radiation promotes expression of pro-inflammatory cytokine that is reversed by transient Hedgehog activation. Hedgehog activation likely preserves parotid macrophages after radiation through inhibition of P53 signaling and consequent cellular senescence. Consistently, VEGF, an essential anti-senescence cytokine downstream of Hedgehog signaling, is significantly decreased by radiation but recovered by transient Hedgehog activation. These findings indicate that in the clinically-relevant swine model, transient Hedgehog activation restores the function of irradiated salivary glands through the recovery of resident macrophages and the consequent inhibition of cellular senescence and inflammation.