Revealing Genetic Dynamics: scRNA-seq Unravels Modifications in Human PDL Cells across In Vivo and In Vitro Environments.

The periodontal ligament (PDL) is a highly specialized fibrous tissue comprising heterogeneous cell populations of an intricate nature. These complexities, along with challenges due to cell culture, impede a comprehensive understanding of periodontal pathophysiology. This study aims to address this gap, employing single-cell RNA sequencing (scRNA-seq) technology to analyze the genetic intricacies of PDL both in vivo and in vitro. Primary human PDL samples (n = 7) were split for direct in vivo analysis and cell culture under serum-containing and serum-free conditions. Cell hashing and sorting, scRNA-seq library preparation using the 10x Genomics protocol, and Illumina sequencing were conducted. Primary analysis was performed using Cellranger, with downstream analysis via the R packages Seurat and SCORPIUS. Seven distinct PDL cell clusters were identified comprising different cellular subsets, each characterized by unique genetic profiles, with some showing donor-specific patterns in representation and distribution. Formation of these cellular clusters was influenced by culture conditions, particularly serum presence. Furthermore, certain cell populations were found to be inherent to the PDL tissue, while others exhibited variability across donors. This study elucidates specific genes and cell clusters within the PDL, revealing both inherent and context-driven subpopulations. The impact of culture conditions-notably the presence of serum-on cell cluster formation highlights the critical need for refining culture protocols, as comprehending these influences can drive the creation of superior culture systems vital for advancing research in PDL biology and regenerative therapies. These discoveries not only deepen our comprehension of PDL biology but also open avenues for future investigations into uncovering underlying mechanisms.

Accuracy of Digital Orthodontic Treatment Planning: Assessing Aligner-Directed Tooth Movements and Exploring Inherent Intramaxillary Side Effects.

Background: The attainment of precise posterior occlusion alignment necessitates a deeper understanding of the clinical efficacy of aligner therapy. This study aims to determine whether the treatment goals defined in the virtual planning of aligner therapy are effectively implemented in clinical practice, with a particular focus on the influence of distalization distances on potential vertical side effects. Methods: In this retrospective, non-interventional investigation, a cohort of 20 individuals undergoing Invisalign® treatment was examined. Pre- and post-treatment maxillary clinical and ClinCheck® casts were superimposed utilizing a surface-surface matching algorithm on palatal folds, median palatine raphe, and unmoved teeth as the stable references. The effectivity of planned versus clinical movements was evaluated. Groupings were based on distalization distances, planned vertical movements, and Class II elastic prescription. Statistics were performed with a two-sample t-test and p-value < 0.05. Results: Clinically achieved distalization was significantly lower than virtually planned distalization, regardless of additional vertical movements, where a lack of implementation was contingent upon the extent of distalization, with no mitigating effects observed with the application of Class II elastics. Intriguingly, no adverse vertical side effects were noted; however, the intended intrusions or extrusions, as per the therapeutic plans, remained unattainable regardless of the magnitude of distalization. Conclusions: These findings underscore the imperative for future investigations to delve deeper into the intricacies surrounding translational mesio-distal and vertical movements, thereby enhancing predictability within orthodontic practice. To facilitate successful clinical implementation of vertical and translational movements via aligners, the incorporation of sliders emerges as a promising strategy for bolstering anchorage reinforcement.

Treatment Efficiency of Maxillary and Mandibular Orovestibular Tooth Expansion and Compression Movements with the Invisalign® System in Adolescents and Adults.

OBJECTIVES: Aligners are an effective and esthetic orthodontic treatment option for permanent and mixed dentition. There are only a few studies dealing with the effectiveness of orovestibular tooth movement using aligners and applying adequate examination methods. In the present retrospective study, the aligner efficiency of orovestibular movements for the entire dentition was systematically evaluated using 3D superimposition, taking into account the influence of jaw, tooth type and Invisalign® system. METHODS: Group 1 (n = 18 adults, Invisalign®) and Group 2 (n = 17 adolescents, Invisalign® Teen) were treated with Invisalign® Ex30 aligner material and Invisalign® specific auxiliary means. In this non-interventional retrospective study, pre- and post-treatment maxillary and mandibular plaster cast models were scanned and superimposed with ClinChecks® via Surface-Surface Matching Algorithm on unmoved teeth providing stable references. Effectivity of planned versus clinically realized movements was evaluated for each tooth. Statistics were performed with a t-test and Bonferroni-Holm correction (α = 0.05). RESULTS: Orovestibular movement efficiency was excellent without statistical significance regarding jaw, tooth type or Invisalign® system. Mandibular translational tooth movements were highly effective, and outstanding for premolars (91-98%). Maxillary translational tooth movements were successful for incisors and premolars, but less effective for canines and molars. Almost all teeth were moderately or very effectively corrected by crown tipping, performing better for mandibular (70-92%) than maxillary (22-31%) canines as much as for adolescent upper front teeth (81-85%) and lower canines (92%). CONCLUSIONS: Aligners are able to effectively implement translational orovestibular movements, supported by tilting the crowns for even more efficient implementation of the movements. This phenomenon was observed in our studies for all teeth in both jaws, regardless of the Invisalign® system used. Treatment planning should nevertheless take into account the individual patient parameters with regard to the movements to be performed in order to make the aligner therapy as successful as possible in terms of realizing the desired therapeutic goal.

Role of chaperone-assisted selective autophagy (CASA) in mechanical stress protection of periodontal ligament cells.

OBJECTIVE: The periodontal ligament (PDL) is exposed to constant mechanical forces potentiated by orthodontic tooth movement (OTM). The aim of our study was to investigate the involvement of chaperone-assisted selective autophagy (CASA) in mechanosensing and cellular adaption to forces in the PDL. MATERIALS AND METHODS: Human PDL cells were loaded with 2.5, 5, and 10% of static mechanical strain for 24 h in vitro. Untreated cells served as controls. Gene expression of HSPA8, HSPB8, BAG3, STUB1, SYNPO2 was investigated via RT-qPCR (Quantitative reverse transcription PCR). Western blot evidenced protein expression of these molecules and of Filamin A. In vivo analyses of CASA were performed via immunohistochemistry on teeth with and without OTM. RESULTS: CASA machinery genes were inherently expressed in PDL cells and exhibited transcriptional induction upon mechanical strain. Protein analyses underlined these findings, even though modulation upon force exertion also demonstrated a decrease for some molecules and loading strengths. In vivo results evidenced again the uniform upregulation of HSPA8, HSPB8, BAG3, STUB1, SYNPO2 and Filamin A in teeth with OTM compared to controls. Experiments generally evidenced a pronounced variability in the expression between donors both on the gene and protein level. CONCLUSIONS: Our study is the first to identify both the expression and functional relevance of CASA in the PDL. The data reflect its probable central role in adequate adaption to forces exerted by OTM and in mechanical stress protection of cells. Deeper knowledge of the CASA pathway will allow better assessment of predisposing factors regarding side effects during mechanical force application that can be used in orthodontic practice.

Analogous modulation of inflammatory responses by the endocannabinoid system in periodontal ligament cells and microglia.

BACKGROUND: Periodontal ligament (PDL) cells initiate local immune responses, similar to microglia regulating primary host defense mechanisms in neuroinflammatory events of the central nervous system. As these two cell types manifest similarities in their immunomodulatory behavior, this study investigated the thesis that the immunological features of PDL cells might be modulated by the endocannabinoid system, as seen for microglia. METHODS: A human PDL cell line and an Embryonic stem cell-derived microglia (ESdM) cell line were grown in n = 6 experimental groups each, incubated with cannabinoid receptor agonists arachidonoylethanolamine (AEA) (50 µM) or Palmitoylethanolamide (PEA) (50 µM) and challenged with centrifugation-induced inflammation (CII) for 6 and 10 h. Untreated samples served as controls. Quantitative real-time polymerase chain reaction was applied for gene expression analyses of inflammatory cytokines, cannabinoid receptors and ionized calcium binding adaptor molecule 1 (IBA-1). Microglia marker gene IBA-1 was additionally verified on protein level in PDL cells via immunocytochemistry. Proliferation was determined with a colorimetric assay (WST-1 based). Statistical significance was set at p < 0.05. RESULTS: IBA-1 was inherently expressed in PDL cells both at the transcriptional and protein level. AEA counteracted pathological changes in cell morphology of PDL cells and microglia caused by CII, and PEA contrarily enhanced them. On transcriptional level, AEA significantly downregulated inflammation in CII specimens more than 100-fold, while PEA accessorily upregulated them. CII reduced cell proliferation in a time-dependent manner, synergistically reinforced by PEA decreasing cell numbers to 0.05-fold in PDL cells and 0.025-fold in microglia compared to controls. CONCLUSION: PDL cells and microglia exhibit similar features in CII with host-protective effects for AEA through dampening inflammation and preserving cellular integrity. In both cell types, PEA exacerbated proinflammatory effects. Thus, the endocannabinoid system might be a promising target in the regulation of periodontal host response.

Impact of the endocannabinoid system on murine cranial and alveolar bone phenotype.

PURPOSE: The endocannabionoid signaling system has been demonstrated to be present in the skeleton, with involvement in the regulation of skeletal homeostasis. However, investigations substantiating these findings in cranial and alveolar bones are missing to date. The aim of our study was to investigate a potential impact of the endocannabinoid system on cranial and alveolar bone structures and phenotypes. BASIC PROCEDURES: CB1-/-, CB2-/- and WT mice (n = 5) were scanned via µCT. Reconstructed datasets were processed for analyses. Cranial cephalometric measurements were performed with OnyxCeph3TMsoftware. Alveolar bone densities were determined via mean grey value measurements with Mimics research 18.0. Alveolar bone heights around teeth in upper and lower jaws were morphometrically analyzed. Alveolar osteoclasts were quantified via TRAP staining of paraffin-embedded histologies. Bone-marrow derived macrophages isolated from murine hind legs were analyzed for CD40 and MMR expression via flow cytometry. MAIN FINDINGS: CB2-/- mice exhibited significantly higher bone densities with mean grey values of 138.3 ± 22.6 compared to 121.9 ± 9.3 for WT for upper jaws, and 134.6 ± 22.9 compared to 116.1 ± 12.9 for WT 134.6 ± 22.9. Concurrently, CB2 receptor knockout entailed reduced alveolar bone heights of about 50% compared to WT mice. Antigen-presenting cell marker expression of MMR was significantly diminished in bone-marrow derived macrophages of CB2-/- mice. Cranium dimensions as much as alveolar osteoclasts were unaffected by receptor knockouts.CB1 receptor knockout did not involve statistically significant alterations in the parameters investigated compared to WT mice. PRINCIPAL CONCLUSIONS: The endoncannabinoid system, and particularly CB2 receptor strongly affects murine alveolar bone phenotypes. These observations suggest CB2 as promising target in the modulation of oral bone phenotypes, probably by impact on bone dynamics via osteal immune cells.

In vivo and In vitro Identification of Endocannabinoid Signaling in Periodontal Tissues and Their Potential Role in Local Pathophysiology.

The endocannabinoid system (ECS) with its binding receptors CB1 and CB2 impacts multiple pathophysiologies not only limited to neuronal psychoactivity. CB1 is assigned to cerebral neuron action, whereas CB2 is mainly expressed in different non-neuronal tissues and associated with immunosuppressive effects. Based on these tissue-selective CB receptor roles, it was the aim of this study to analyze potential expression in periodontal tissues under physiological conditions and inflammatory states. In vivo, CB receptor expression was investigated on human periodontal biopsies with or without bacterial inflammation and on rat maxillae with or without sterile inflammation. In vitro analyses were performed on human periodontal ligament (PDL) cells at rest or under mechanical strain via qRT-PCR, Western blot, and immunocytochemistry. P < 0.05 was set statistical significant. In vivo, CB1 expression was significantly higher in healthy PDL structures compared to CB2 (13.5% ± 1.3 of PDL tissues positively stained; 7.1% ± 0.9). Bacterial inflammation effected decrease in CB1 (9.7% ± 2.4), but increase in CB2 (14.7% ± 2.5). In contrast, sterile inflammation caused extensive CB1 (40% ± 1.9) and CB2 (41.7% ± 2.2) accumulations evenly distributed in the tooth surrounding PDL. In vitro, CB2 was ubiquitously expressed on gene and protein level. CB1 was constitutively expressed on transcriptional level (0.41% ± 0.09), even higher than CB2 (0.29% ± 0.06), but undetectable on protein level. Analyses further revealed expression changes of both receptors in mechanically loaded PDL cells. CB1 and CB2 are varyingly expressed in periodontal tissues, both adjusted by different entities of periodontal inflammation and by mechanical stress. This indicates potential ECS function as regulatory tool in controlling of periodontal pathophysiology.

Influence of tooth dimension on the initial mobility based on plaster casts and X-ray images : A numerical study.

AIMS: The goal was to determine the influence of different geometric parameters of the tooth on the initial tooth mobility and the position of the center of resistance employing numerical models based on scaled X-ray images and plaster casts. METHODS: The dimensions of tooth 21 were measured in 21 patients, using radiographs and dental casts. Length and mesiodistal width of the tooth were obtained from the X-ray image and the orovestibular diameter from the plaster cast. Finite element models were generated. Cortical and cancellous bone and the periodontal ligament were simulated to create realistic models. Root length (11-17 mm), mesiodistal width (6-10 mm) and orovestibular thickness (7-9 mm) were varied in 1-mm steps to generate 105 models. In the simulation, each model was loaded with a force of 10 N in vestibulopalatinal direction and with a torque of 10 Nmm to determine tooth displacements and center of resistance. RESULTS: Initial tooth displacement and thus mobility increased with decreasing total root surface. The shortest, slimmest and thinnest tooth showed a total deflection of 0.14 mm at the incisal edge, while the longest, widest and thickest tooth showed a total deflection of 0.10 mm. Changes in mesiodistal width had the greatest influence on initial tooth mobility and changes in orovestibular thickness the least. The teeth's center of resistance was positioned between 37 and 43% of the root length measured from the cervical margin of the alveolar bone. The center of resistance of the longest dental root investigated was located around 6% more cervically compared to the one of the shortest dental root. The influence of root width and thickness on the position of the center of resistance was significantly lower than root length. CONCLUSION: Geometric parameters significantly impact initial tooth mobility and position of the center of resistance. Thus, tooth dimensions should be considered in orthodontic treatment planning. Dental radiographs represent a sufficient validation tool to estimate the quality of a pure dental tipping during orthodontic treatment, as the orovestibular thickness has little influence. However, for three-dimensional tooth displacements all geometric parameters should be determined accurately using plaster casts or DVT.

In vivo determination of tooth mobility after fixed orthodontic appliance therapy with a novel intraoral measurement device.

OBJECTIVE: Valid measurement systems recording tooth mobility upon displacement within the subtle range of physiological strains are missing. Here, we introduce a novel in vivo measurement device and demonstrate a first clinical application by monitoring tooth mobility changes during retention after fixed multibracket appliance therapy. MATERIALS AND METHODS: Tooth mobility was measured in vivo on 21 patients (11 female, 10 male; mean age 16.1 ± 3.1 years) by displacing the upper first incisor 0.2 mm lingually for 0.2, 0.5, 1, 2, 5, and 10 s with the novel intraoral device. Measurements were recorded directly after, as much as 2, 7, and 14 days and up to 6 months after appliance debonding. RESULTS: Device performance was precise and valid in clinical use. Data revealed significant interindividual varying tooth mobility, which was very high during the first 2 days after appliance removal. After 1 week, mobility values decreased, but were generally higher upon short loadings compared to long ones. After 3 months, tooth mobility was significantly lower than directly after debonding. Interestingly, males exhibited significantly less mobility than females. CONCLUSIONS: Our work is the first using an in vivo measurement device capable of performing and recording tooth displacements within this delicate range and in such precision. Furthermore, our findings elucidate tooth mobility changes after multibracket treatment, giving important information for retention periods. CLINICAL RELEVANCE: Establishment of this novel measurement device in clinical use is an important improvement when approaching the complexity of tooth mobility in vivo regarding different issues like orthodontics, periodontal disease, or bruxism.

GABAB Receptors as Modulating Target for Inflammatory Responses of the Periodontal Ligament.

PDL cells express GABAB1 and GABAB2 receptors, which are regulated by inflammation and thus might be implicated in periodontal immunology. It was the aim of this study to elucidate the functional role of GABAB receptors in immunomodulation regarding activation of proregenerative versus proinflammatory mechanisms. Human PDL cells were exposed to GABA and/or GABAB receptor antagonist CGP-52432 alone or in combination with IL-1ß to mimic inflammation. The influence on marker expression for inflammatory tissue destruction was determined via qRT-PCR and Luminex assays. Proliferation and biomineralization were assessed by MTS assay and von Kossa staining. Statistical significance was set at p < 0.05. GABAB receptor blockade inhibited expression of IL-6, TNFα, MMP-3, and MMP-8 in an inflammatory milieu on transcriptional and on protein level, mediated by NF-κB. Besides, receptor blockade enhanced proliferation, especially under inflammatory conditions, and reduced mineralization in a non-inflammatory milieu. GABAB receptor activity on PDL cells is involved in the modulation of osteoimmunological processes in the periodontium and decides on the initiation versus prevention of host protective mechanisms. This implies anabolic potential for a therapeutic preservation or reestablishment of periodontal tissues under physiological and pathological conditions. In summary, GABAB receptor modulation in PDL cells might become an important target in immunoinflammatory settings.

Verification of γ-Amino-Butyric Acid (GABA) Signaling System Components in Periodontal Ligament Cells In Vivo and In Vitro.

CNS key neurotransmitter γ-amino-butyric acid (GABA) and its signaling components are likewise detectable in non-neuronal tissues displaying inter alia immunomodulatory functions. This study aimed at identifying potential glutamate decarboxylase (GAD)65 and GABA receptor expression in periodontal ligament (PDL) cells in vivo and in vitro, with particular regard to inflammation and mechanical loading. Gene expression was analyzed in human PDL cells at rest or in response to IL-1ß (5 ng/ml) or TNFα (5 ng/ml) challenge via qRT-PCR. Western blot determined constitutive receptor expression, and confocal laser scanning fluorescence microscopy visualized expression changes induced by inflammation. ELISA quantified GAD65 release. Immunocytochemistry was performed for GABA component detection in vitro on mechanically loaded PDL cells, and in vivo on rat upper jaw biopsies with mechanically induced root resorptions. Statistical significance was set at p < 0.05. GABAB1, GABAB2, GABAA1, and GABAA3 were ubiquitously expressed both on gene and protein level. GABAA2 and GAD65 were undetectable in resting cells, but induced by inflammation. GABAB1 exhibited the highest basal gene expression (6.97 % ± 0.16). IL-1ß markedly increased GABAB2 on a transcriptional (57.28-fold ± 12.40) and protein level seen via fluorescence microscopy. TNFα-stimulated PDL cells released GAD65 (3.68 pg/ml ± 0.17 after 24 h, 5.77 pg/ml ± 0.65 after 48 h). Immunocytochemistry revealed GAD65 expression in mechanically loaded PDL cells. In vivo, GABA components were varyingly expressed in an inflammatory periodontal environment. PDL cells differentially express GABA signaling components and secrete GAD65. Inflammation and mechanical loading regulate these neurotransmitter molecules, which are also detectable in vivo and are potentially involved in periodontal pathophysiology.

Histopathological Verification of Osteoimmunological Mediators in Peri-Implantitis and Correlation to Bone Loss and Implant Functional Period.

Peri-implantitis (PI) is characterized by inflammation and bone resorption eventually leading to implant failure, but the characteristic pathologic determinants are undefined to date. This study aims to elucidate the parameters involved in PI pathogenesis, including intraoral implant retention time, extent of bone loss, smoking history, and identification of osteoimmunological markers for inflammation and bone loss. Peri-implant tissues (n = 21) displaying clinically diagnosed PI from patients with vertical bone loss ranging from 0-12 mm and implant function period between 1 and 60 months were evaluated by histochemistry and immunohistochemistry for TRAP, CD3, RANK, RANKL, OPG, and TNF-α. Statistical analyses were performed with the Welch test and correlation coefficients were calculated. Most bone resorption occurred during the first 12 months of implant function and correlated with the extent of inflammation, although histological signs of inflammation strongly varied between samples from minimal appearance of inflammatory cells to extended infiltrates. Implant function period and smoking history did not significantly affect the degree of inflammation. Higher RANK levels emerged in the first 12 months of implant function compared to longer retention times and were negatively correlated to the occurrence of RANKL. Additionally, histological signs of inflammation were about two-fold higher in specimens with bone resorption up from 5 mm compared to under 5 mm. CD3(+) cells were more prevalent in extensive inflammatory infiltrates and samples derived from smokers. Our analyses proved that PI-induced bone loss is differentially influenced by the parameters evaluated in this study, but a distinct interconnection between disease severity and implant retention time can be established.

Symmetric and asymmetric expansion of molars using a Burstone-type transpalatal arch. Biomechanical and clinical analysis.

OBJECTIVES: A transpalatal arch (TPA) directly connecting the maxillary first molars can be used in passive (for stabilization) and active (for molar or segment movement) modes. Activation may be symmetric or asymmetric. This study was performed to analyze the effectiveness of TPAs for transverse expansion treatment by measuring both the force systems they deliver and the clinical tooth movements thus achieved. MATERIALS AND METHODS: Ten patients (six with symmetric and four with asymmetric transverse discrepancies) were treated using a TPA made of titanium-molybdenum alloy (TMA) and fitted with 0.032" × 0.032" Burstone lingual brackets. The force systems exerted by these TPAs and the resultant tooth movements were first simulated and measured inside the orthodontic measurement and simulation system (OMSS). All TPAs, whether used in the symmetric or asymmetric activation mode, were adjusted to an expansive force of 4 N. After a treatment of 12 weeks, their effectiveness was analyzed by comparing the clinical tooth movements to the movements simulated in the OMSS. RESULTS: Clinically, the symmetric treatments resulted in a mean correction of 4.5 ± 1.0 mm and a mean of buccal crown tipping of 10.1°, compared to 9.6° for the movements simulated in the OMSS. The four cases of unilateral crossbite were treated with an asymmetrically activated TPA (including a force on one side and a combination of force and negative torque on the other side). The intended unilateral expansion was achieved in all four cases. Vertical side effects were acceptably small in both the symmetric and the asymmetric treatment cases. The tooth movements could be implemented as planned in all 10 patients, whereby in 5 patients complete correction of the occlusal width discrepancy was achieved by the end of the 12-week treatment. CONCLUSION: Given this combination of good efficacy and minor side effects, the TMA/TPA appliance may be recommended as a suitable approach to correct transverse discrepancies. Recommendations expressed in previous studies for the use of Burstone-type TMA/TPA in these situations is confirmed by our study.

Freehand Condyle-Positioning During Orthognathic Surgery: Postoperative Cone-Beam Computed Tomography Shows Only Minor Morphometric Alterations of the Temporomandibular Joint Position.

OBJECTIVES: Purpose of this study was to evaluate changes in the temporomandibular joint (TMJ) position after bilateral sagittal split osteotomy (BSSO) of the mandible by the help of pre- and postoperative cone-beam computed tomography (CBCT) images. MATERIALS AND METHODS: A collective of n = 78 patients was investigated between 2009 and 2011 before and after BSSO of the mandible in mono- or bimaxillary orthognathic surgery procedures. No intraoperative fixation of the condyles was administered. CBCT scans were performed in all patients before and immediately after surgery with the KaVo 3DeXam device in the position of terminal occlusion. Subsequently, all scans were analyzed by help of the eXam Vision program and the ImageJ image processing software. Alterations of the TMJs were quantified by determining pre- to postoperative differences of the intercondylar distance, the mandibular angle on both sides, and the condylar angles in the transversal plane. RESULTS: The difference between pre- and postoperatively ascertained values was minimal (means: lateral condylar distance -0.17  mm; distance of condylar centers -0.32  mm; medial condylar distance -0.49  mm; left mandibular angle +1.06°; right mandibular angle +2.06°; condylar angles in relation to a reference line: left -2.93, right -0.75; angle of cutting +3.42). There is no apparent tendency toward a positional change in any of the 3 examined planes. Between bi- and monomaxillarily operated patients there was no difference either, except for the osteotomy plane. CONCLUSIONS: A 3-dimensional analysis of CBCT data of the TMJ seems to be appropriate to determine the condylar position pre- and postoperatively. Performed by an experienced orthognathic surgeon, BSSO of the mandible does not effectuate any relevant changes of the TMJ-position, thus making an intraoperative condyle-fixation unnecessary.

The p53/miR-17/Smurf1 pathway mediates skeletal deformities in an age-related model via inhibiting the function of mesenchymal stem cells.

Osteoporosis is an age-related progressive bone disease. Trp53 (p53) is not only a famous senescence marker but also a transcription regulator which played a critical role in osteogenesis. However, how p53 contributes to the bone mass loss in age-related osteoporosis is still unclear. Here, we found that bone mass and osteogenic differentiation capacity of mesenchymal stem cells (MSCs) is significantly reduced with advancing age. Serum levels of TNF-α and INF-γ and senescence-associated ß-galactosidase, p16, p21 and p53 are significantly increased in elder mice, but antipodally, osteogenic marker expression of Runx2, ALP and osterix are reduced. Overexpression p53 by lentivirus inhibits osteogenesis in young MSCs in culture and upon implantation in NOD/SCID mice through inhibiting the transcription of miR-17-92 cluster, which is decreased in old mice. In addition, miR-17 mimics could partially rescue the osteogenesis of old MSCs both in vitro an in vivo. More importantly, Smurf1 as a direct target gene of miR-17, plays an important role in the p53/miR-17 cascade acting on osteogenesis. Our findings reveal that p53 inhibits osteogenesis via affecting the function of MSCs through miRNA signaling pathways and provide a new potential target for treatment in future.

Manganese superoxide dismutase is required to maintain osteoclast differentiation and function under static force.

Bone homeostasis is maintained by the balance of osteoblasts (OBs) and osteoclasts (OCs). Increased activity of OCs not only contributes to pathological bone resorption, such as osteoporosis and periodontitis, but also is responsible for physiological conditions like orthodontic tooth movement (OTM). However, the detailed mechanism by which orthodontic force promotes the formation of OCs is still poorly understood. In this study, we confirmed that static force promoted the differentiation of human cord monocytes (HMNCs) into OCs depending on loading time and magnitude. Protein expression profiles among HMNCs, HMNCs subjected to static force and mature OCs were established via 2-DE and MALDI-TOF-MS analyses. Total respective protein spot numbers of 549 ± 13, 612 ± 19 and 634 ± 16 were detected in each of the gels by image analysis. The five proteins identified were plasminogen activator inhibitor 2 (PAI-2, Spot 1), peroxiredoxin-6 (PRD-6, Spot 3), manganese superoxide dismutase (SOD2, Spot 6), Rho GDP-dissociation inhibitor 2 (Rho-GDI2, Spot 11) and L-lactate dehydrogenase B chain (L-LDH, Spot 15). More importantly, we revealed that SOD2 was required to maintain monocyte differentiation into functional OCs and may become a potential target for regulating the efficiency of OTM in the future.

Tissue reactions after simultaneous alveolar ridge augmentation with biphasic calcium phosphate and implant insertion--histological and immunohistochemical evaluation in humans.

OBJECTIVES: Simultaneous lateral augmentation and implant placement is considered as standard procedure in deficient edentulous ridges in oral implantology. Histological studies monitoring osteogenesis after application of alloplastic bone substitutes in humans are scarce. Bone formation upon simultaneous augmentation with biphasic calcium phosphate (BCP) and implantation was histologically investigated after 6 months in situ. The results of this secondary analysis are reported tempting to ascribe specific observations to uneventful submerged healing or compromised healing of soft tissues including occurrence of dehiscences and premature graft exposure. MATERIALS AND METHODS: Histology of biopsies from lateral, crestal bone augmentations using alloplastic BCP comprising seven sites with compromised, prematurely exposed healing and six sites with uneventful submerged healing was investigated for expression of osteogenic, osteoclastogenic, and angiogenic differentiation markers. RESULTS: Histology revealed alkaline phosphatase (ALP)-positive osteoblasts and immunoreactivity for osteogenic markers osteocalcin and collagen type I in biopsies with submerged healing, while inflammatory infiltrates and accumulations of multinucleated giant cells around BCP granules were observed in compromised sites. All specimens presented adequate vessel density. Multinucleated giant cells showed inconsistent staining for the osteoclast marker tartrate-resistant acid phosphatase (TRAP). CONCLUSIONS: The histological findings of this study indicate an osteoconductive nature of the BCP applied. Premature exposure of the bone substitute reduced new bone formation and may bear a risk for inflammatory and foreign body reactions. CLINICAL RELEVANCE: A predictable appositional bone formation in simultaneously augmented sites using BCP is linked to an uneventful healing process.

Different bracket-archwire combinations for simulated correction of two-dimensional tooth malalignment: Leveling outcomes and initial force systems.

OBJECTIVES: Self-ligating brackets are widely believed to be more effective in clinical use and to involve less friction and force. Thus, the goal of this in vitro investigation was to experimentally assess the effectiveness of different bracket-archwire combinations and the force levels exerted in two-dimensional direction during correction of tooth malalignment. An important aspect of this objective was to determine whether the behaviors of conventional bracket systems with an elastic or steel ligature differ from that of self-ligating brackets. MATERIALS AND METHODS: Three conventional (Mini Taurus®, RMO; Synergy®, RMO; Victory Series™, 3M Unitek) and three self-ligating bracket systems (Speed™, Strite; Smart Clip™, 3M Unitek; Time 3, American Orthodontics) were analyzed. All brackets had 0.018-inch (0.46-mm) slots and--except for the self-ligating brackets-were tested with both a steel ligature (0.25 mm; Remanium, Dentaurum) and an elastic rubber ligature (1.3 mm in diameter; Dentalastics, Dentaurum). They were fitted with four different round wires: a 0.30-mm stainless steel (3M Unitek), 0.38-mm stainless steel coaxial (Advanced Orthodontics), 0.30-mm Thermalloy NiTi (RMO), and 0.30-mm Orthonol NiTi (RMO) archwire. The orthodontic measurement and simulation system (OMSS) was used to simulate a two-dimensional (2 mm of infraocclusion and 2 mm of vestibular displacement) malalignment of tooth 21 inserted in a resin replica of a Frasaco model. Four brackets of the same type were assessed and four individual measurements taken per bracket to analyze initial force systems and corrective malalignment outcomes. RESULTS: The initial force systems and tooth movements varied distinctly between the different material combinations in conjunction with the ligation systems and archwire types used. The force systems generated were readily reproducible across individual measurements. Leveling outcomes and force systems between conventional steel-ligated and self-ligating brackets coincided in most cases. Both of these device configurations corrected the malalignment by 78-99 % on average. Rubber-ligated conventional brackets, by contrast, performed significantly worse due to exertion of significantly higher forces and 60 % less of a leveling effect. CONCLUSION: Our investigation demonstrates that both conventional steel-ligated brackets and self-ligating brackets, which are highlighted in the literature as highly efficient systems, lead to equivalent corrective outcomes in the treatment of tooth malalignments.