Sociodemographic, biological, and timing characteristics of dental caries and fluorosis using mixed-type cluster analysis on 12-year-olds in Ho Chi Minh city, 1989-2019.

Objectives: In 1990, Ho Chi Minh City started Community water fluoridation (CWF) at 0.7 ppm F, and in 2000, it was adjusted to 0.5 ppm F. Here, we analyzed dental caries and fluorosis data in Ho Chi Minh City to explore commonalities associated with CWF among 12-year-old children. Methods: Dental caries and fluorosis data were collected in 1989, 2003, 2012, and 2019 (N = 4773). Trained dentists scored dental caries using the WHO detection criteria and fluorosis using Dean's Fluorosis Index. We used these data and the k-prototypes method by the R package to identify clusters of participants with shared clinical and water fluoride levels. Results: We used datasets 1 (4773 participants) and 2 (4194 participants, missing fluorosis data in 1989). K-prototypes analysis identified three clusters in each dataset. Cluster 1, with 80 % of the sample at 0.5 ppm F area characterized by low caries and fluorosis scores. Cluster 2 with 60 % of the sample non-fluoridated area had high caries and low fluorosis scores. Cluster 3, with 75 % of the sample in 0.7 ppm area, had low caries but borderline high fluorosis scores. Conclusion: Identifying three clusters based on clinical and environmental scores supports the decision to fluoridate the water to prevent caries (0-0.7 ppm) and the shift from 0.7 to 0.5 ppm to keep the caries preventive effect while reducing the risk of fluorosis. Clinical significance: Our results support the effectiveness of CWF in preventing dental caries and the appropriateness of changing the F concentration to reduce the risk of fluorosis while maintaining its effectiveness.

The neutrophil-osteogenic cell axis promotes bone destruction in periodontitis.

The immune-stromal cell interactions play a key role in health and diseases. In periodontitis, the most prevalent infectious disease in humans, immune cells accumulate in the oral mucosa and promote bone destruction by inducing receptor activator of nuclear factor-κB ligand (RANKL) expression in osteogenic cells such as osteoblasts and periodontal ligament cells. However, the detailed mechanism underlying immune-bone cell interactions in periodontitis is not fully understood. Here, we performed single-cell RNA-sequencing analysis on mouse periodontal lesions and showed that neutrophil-osteogenic cell crosstalk is involved in periodontitis-induced bone loss. The periodontal lesions displayed marked infiltration of neutrophils, and in silico analyses suggested that the neutrophils interacted with osteogenic cells through cytokine production. Among the cytokines expressed in the periodontal neutrophils, oncostatin M (OSM) potently induced RANKL expression in the primary osteoblasts, and deletion of the OSM receptor in osteogenic cells significantly ameliorated periodontitis-induced bone loss. Epigenomic data analyses identified the OSM-regulated RANKL enhancer region in osteogenic cells, and mice lacking this enhancer showed decreased periodontal bone loss while maintaining physiological bone metabolism. These findings shed light on the role of neutrophils in bone regulation during bacterial infection, highlighting the novel mechanism underlying osteoimmune crosstalk.

Influence of titanium dioxide and composite on the accuracy of an intraoral scanner for bilateral upper posterior edentulous jaw (Kennedy class I) scanning: An in vitro study.

OBJECTIVES: The accuracy of 3-dimensional images produced by the intraoral scanner (IOS) is affected by scanning-aid materials. This in vitro study aimed to elucidate the influence of scanning-aid materials on the accuracy (trueness and precision) of digital scanning on the bilateral upper posterior edentulous jaw (Kennedy class I). METHODS: The asymmetrical bilateral upper posterior edentulous model (reference model) was generated using a 3D printer with three groups (application of TiO2 powder - composite and no-treatment control). The experimental scans were executed (n = 10 per group) using TRIOS3 (3shape), while one reference scan was obtained by an industrial scanner (Solutionix - C500). Values of trueness and precision were evaluated using the 3D superimposition method on mean deviation values. The accuracy was assessed using mean deviation values following the 3D superimposition method. RESULTS: IOS had high trueness (20.6 µm), and significant differences were found between the no-treatment and TiO2 groups. Considering the cut-off value of deviations as 300 µm for clinical acceptability, the analysis clarified the most variations in the control group. There was a significant difference between the no-treatment group and others in the maxillary tuberosity area relating to long-span edentulous. The composite group had the best precision values (1.1 µm). Significant differences were found between composite and TiO2 groups (2.7 µm). CONCLUSIONS: The bilateral upper posterior edentulous jaw digital impressions obtained using IOS were accurate. However, the digital images in the palate and maxillary tuberosity area related to long-span edentulous differed significantly. TiO2-containing powder and composite landmarks affected the accuracy and stability of the IOS. CLINICAL SIGNIFICANCE: Scanning aid materials can increase the accuracy of the bilateral upper posterior edentulous jaw scanning with IOS.

Developing and assessing the efficiency of VOSER software in recording dental caries according to WHO's criteria 2013.

Background/purpose: World Health Organization (WHO) oral health survey manual is the main guideline for most oral health surveys worldwide. It has been updated several times since 1971; however, using papers and pens for data recording remains unchanged. This study aimed to develop the Vietnam Oral Survey Electronics Recorder (VOSER) to record dental caries data based on the WHO 2013 criteria and assess its reliability and efficiency. Materials and methods: VOSER was developed and tested for reliability and efficiency by performing clinical examinations on 365 school children in three key indicator age groups: 120 5-year-old students with primary dentition, 123 8-year-old students with mixed dentition, and 122 12-year-old students with permanent dentition. One gold standard examiner and two trained clerks examined these children using either WHO's paper survey form or VOSER's digital form for dental caries. Recording time, spreadsheet time, DMFT/S, and dmft/s were analyzed to compare the efficiency of VOSER to the paper form. Cohen's Kappa, intraclass correlation coefficient, and Wilcoxon signed-rank test were adopted in the data analyses. Results: Median time of using VOSER was significantly shorter than the standard time in all three dentitions (P < 0.001). Cohen's Kappa values between data collected by VOSER and paper form showed almost perfect agreements (0.927-0.958). DMFT/S and dmft/s values calculated from data collected by both methods had good to excellent reliabilities (0.791-0.997). Conclusion: VOSER is efficient and reliable for conducting dental caries surveys according to the WHO 2013 criteria and should be utilized in the era of digital technology.

Reliability of online dental final exams in the pre and post COVID-19 era: A comparative study.

Amidst the fourth COVID-19 wave in Viet Nam, national lockdowns necessitated the closure of numerous dental schools. To assess DDS (Doctor of Dental Surgery) graduation exams, this study analyzed their 2021 implementation in comparison to onsite exams conducted in 2020 and 2022 at the Faculty of Odonto-Stomatology, University of Medicine and Pharmacy at Ho Chi Minh City, Viet Nam (FOS-UMPH). The final online examination comprises two main sessions: a synchronous online examination using FOS-UMPH e-Learning for theories (consisting of 200 MCQs and 3 written tests with 3 clinical situations needed be solved) and a synchronous online examination using Microsoft Teams for practicum (comprising of 12 online OSCE stations). The final grades were evaluated using the same metrics in face-to-face final examinations in 2022 and 2020. A total of 114, 112 and 95 students were recruited for the first-time exams in 2020, 2021 and 2022, respectively. In order to analyze the reliability, histogram and k-mean clustering were employed. The histograms from 2020, 2021 and 2022 showed a striking similarity. However, fewer students failed in 2021 and 2022 (13% and 12.6%, respectively) compared to 2020 (28%), with clinical problem-solving part grades (belonging to theory session) being notably higher in 2021 and 2022. Intriguingly, the MCQ Score results showed the identical patterns. The courses of orthodontics, dental public health, and pediatrics subjects (in the group of prevention and development dentistry) stood out for their exceptional accuracy across both sessions. After examining data gathered over three years, we identified three distinct clusters: the first comprised of scattered average and low scores, the second characterized by high scores but unstable and scattered and the third cluster boasting consistently high and centered scores. According to our study, online and onsite traditional graduation exam results are relatively equivalent, but additional measures are necessary to standardize the final examination and adapt to the new normal trend in dental education.

Effects of core buildup composite resin translucency on intraoral scanner accuracy: an in vitro study.

AIM: The accuracy of 3D images produced by an intraoral scanner (IOS) is affected by the optical characteristics of restorative materials such as metal, ceramic, and composite resin. The present in vitro study aimed to investigate the impact of core buildup composite resin translucency on IOS accuracy. MATERIALS AND METHODS: A core buildup procedure was performed on a proprietary 3D-printed model using injectable composite resins in four groups with different levels of translucency (highest to lowest: AE, A3, AO3, and EX). Ten experimental scans per group were performed using a Medit i700 IOS on a phantom head-mounted model. Reference scans were obtained using an industrial scanner (Solutionix C500). Values of accuracy (trueness and precision) for the respective groups were evaluated using mean deviation values following 3D superimposition. RESULTS: Composite resin translucency caused the scale reduction of the optical impressions. Values of trueness showed the highest scale reduction in AE, significantly, followed by A3, AO3, and EX. Considering 50 µm as the cut-off value of deviations for clinical acceptability, the analysis showed most deviations in AE and A3. Similar results were found with precision, where AE showed the highest deviation value statistically, followed by A3, AO3, and EX. CONCLUSIONS: Composite resin translucency affects the accuracy of optical impressions, causing a fitting error of CAD/CAM prostheses. The more translucent the composite resin, the less accurate the optical impression. This suggests the need for proper compensation during prosthesis designing for an optimal clinical result. In addition, practitioners should indicate in the digital workflow the proper restorative materials regarding not only the mechanical properties and esthetics, but also the optical characteristics.

ETS1 governs pathological tissue-remodeling programs in disease-associated fibroblasts.

Fibroblasts, the most abundant structural cells, exert homeostatic functions but also drive disease pathogenesis. Single-cell technologies have illuminated the shared characteristics of pathogenic fibroblasts in multiple diseases including autoimmune arthritis, cancer and inflammatory colitis. However, the molecular mechanisms underlying the disease-associated fibroblast phenotypes remain largely unclear. Here, we identify ETS1 as the key transcription factor governing the pathological tissue-remodeling programs in fibroblasts. In arthritis, ETS1 drives polarization toward tissue-destructive fibroblasts by orchestrating hitherto undescribed regulatory elements of the osteoclast differentiation factor receptor activator of nuclear factor-κB ligand (RANKL) as well as matrix metalloproteinases. Fibroblast-specific ETS1 deletion resulted in ameliorated bone and cartilage damage under arthritic conditions without affecting the inflammation level. Cross-tissue fibroblast single-cell data analyses and genetic loss-of-function experiments lent support to the notion that ETS1 defines the perturbation-specific fibroblasts shared among various disease settings. These findings provide a mechanistic basis for pathogenic fibroblast polarization and have important therapeutic implications.

Periosteal stem cells control growth plate stem cells during postnatal skeletal growth.

The ontogeny and fate of stem cells have been extensively investigated by lineage-tracing approaches. At distinct anatomical sites, bone tissue harbors multiple types of skeletal stem cells, which may independently supply osteogenic cells in a site-specific manner. Periosteal stem cells (PSCs) and growth plate resting zone stem cells (RZSCs) critically contribute to intramembranous and endochondral bone formation, respectively. However, it remains unclear whether there is functional crosstalk between these two types of skeletal stem cells. Here we show PSCs are not only required for intramembranous bone formation, but also for the growth plate maintenance and prolonged longitudinal bone growth. Mice deficient in PSCs display progressive defects in intramembranous and endochondral bone formation, the latter of which is caused by a deficiency in PSC-derived Indian hedgehog (Ihh). PSC-specific deletion of Ihh impairs the maintenance of the RZSCs, leading to a severe defect in endochondral bone formation in postnatal life. Thus, crosstalk between periosteal and growth plate stem cells is essential for post-developmental skeletal growth.

Comprehensive Integrated Single-Cell Whole Transcriptome Analysis Revealed the p-EMT Tumor Cells-CAFs Communication in Oral Squamous Cell Carcinoma.

Cancer-associated fibroblasts (CAFs) and partial epithelial-mesenchymal transition (p-EMT) tumor cells are closed together and contribute to the tumor progression of oral squamous cell carcinoma (OSCC). In the present study, we deeply analyzed and integrated OSCC single-cell RNA sequencing datasets to define OSCC CAFs and p-EMT subpopulations. We highlighted the cell-cell interaction network of CAFs and p-EMT tumor cells and suggested biomarkers for the diagnosis and prognosis of OSCC during the metastasis condition. The analysis discovered four subtypes of CAFs: one p-EMT tumor cell population, and cycling tumor cells as well as TNFSF12-TNFRSF25/TNFRSF12A interactions between CAFs and p-EMT tumor cells during tumor metastasis. This suggests the prediction of therapeutically targetable checkpoint receptor-ligand interactions between CAFs and p-EMT tumor cells in OSCC regarding the metastasis status.

Single-Cell RNA Sequencing Analysis for Oncogenic Mechanisms Underlying Oral Squamous Cell Carcinoma Carcinogenesis with Candida albicans Infection.

Oral squamous cell carcinoma (OSCC) carcinogenesis involves heterogeneous tumor cells, and the tumor microenvironment (TME) is highly complex with many different cell types. Cancer cell-TME interactions are crucial in OSCC progression. Candida albicans (C. albicans)-frequently pre-sent in the oral potentially malignant disorder (OPMD) lesions and OSCC tissues-promotes malignant transformation. The aim of the study is to verify the mechanisms underlying OSCC car-cinogenesis with C. albicans infection and identify the biomarker for the early detection of OSCC and as the treatment target. The single-cell RNA sequencing analysis (scRNA-seq) was performed to explore the cell subtypes in normal oral mucosa, OPMD, and OSCC tissues. The cell composi-tion changes and oncogenic mechanisms underlying OSCC carcinogenesis with C. albicans infec-tion were investigated. Gene Set Variation Analysis (GSVA) was used to survey the mechanisms underlying OSCC carcinogenesis with and without C. albicans infection. The results revealed spe-cific cell clusters contributing to OSCC carcinogenesis with and without C. albicans infection. The major mechanisms involved in OSCC carcinogenesis without C. albicans infection are the IL2/STAT5, TNFα/NFκB, and TGFß signaling pathways, whereas those involved in OSCC carcinogenesis with C. albicans infection are the KRAS signaling pathway and E2F target down-stream genes. Finally, stratifin (SFN) was validated to be a specific biomarker of OSCC with C. albicans infection. Thus, the detailed mechanism underlying OSCC carcinogenesis with C. albicans infection was determined and identified the treatment biomarker with potential precision medicine applications.

Effects of advanced platelet-rich fibrin combined with xenogenic bone on human periodontal ligament stem cells.

OBJECTIVES: In this study, we aimed to investigate the effects of a mixture of advanced platelet-rich fibrin (A-PRF) and xenogenic bone substitute material (XBSM) on the proliferation and migration of human periodontal ligament stem cells (hPDLSCs) based on the in vitro release of growth factors. MATERIAL AND METHODS: The concentrations of platelet-derived growth factor-AB (PDGF-AB) and vascular endothelial growth factor (VEGF) released by the A-PRF-XBSM mixture were estimated using enzyme-linked immunoassay for up to 7 d. The A-PRF-XBSM mixture exudate was incubated with hPDLSCs. At Days 1, 3, 5, and 7, cell proliferation and migration were investigated by cell counting and wound-healing assays. RESULTS: PDGD-AB and VEGF were released from the A-PRF-XBSM mixture exudate for up to 7 days. hPDLSCs were cultured in media with various concentrations of the A-PRF-XBSM mixture exudate and exhibited their proliferation and migration ability. Furthermore, the factors released from the 100% A-PRF-XBSM mixture exudate had a substantial effect on cell migration, whereas those released from 4% and 20% A-PRF-XBSM mixture exudates stimulated hPDLSC proliferation. CONCLUSIONS: A-PRF-XBSM mixture continuously released growth factors over 7 days and enhanced hPDLSC proliferation and migration. Therefore, A-PRF in combination with XBSM might provide potential advantages for periodontal tissue regeneration.

Effect of Photobiomodulation Therapy on Reducing Acute Pain and Inflammation Following Surgical Removal of Impacted Mandibular Third Molars: A Randomized, Split-Mouth Clinical Trial.

Objective: This study aimed to compare the effects of photobiomodulation therapy (PBMT) on analgesic and inflammatory reduction with that of ibuprofen following surgical removal of impacted mandibular third molars (IMTMs). Methods: A randomized, split-mouth clinical trial was performed on patients undergoing bilateral IMTM removal. PBMT [gallium aluminum arsenide (GaAlAs) laser] with specific parameters (wavelength of 810 nm, power of 0.5% ± 20% W, and energy density of 4 J/cm2) was applied randomly on one side of the mouth immediately after surgery and 1 and 2 days after surgery. The pain level was self-rated with a Likert scale at 2, 4, 6, 24, and 48 h postoperatively. Swelling and trismus were measured on the first and second day after surgery. Saliva was collected for measuring pre- and postoperative salivary immunoglobulin A (sIgA) concentrations with the sandwich ELISA test. Results: The study sample included 25 patients (average age of 22.88 years) with 50 bilateral symmetrical IMTMs. Pain level was highest at 2 h after surgery in both groups and gradually decreased over time (p < 0.01). Swelling and trismus at 48 h were higher than at 24 h (p < 0.01). Within the first 48 h postoperatively, pain level, swelling, and trismus were significantly lower in the PBMT group (p < 0.05). Postoperative sIgA was also significantly lower in the PBMT group (p < 0.05). Conclusions: In short-term and specific conditions of this study, it was found that PBMT helped promote postoperative pain relief and anti-inflammation after surgical removal of IMTMs. The results suggested that there may be a link between a decrease in salivary sIgA levels and decrease in inflammatory processes after PBMT. Trial Registration No. NCT04280809 at ClinicalTrials.gov.

Effects of non-surgical periodontal treatment in rheumatoid arthritis patients: A randomized clinical trial.

BACKGROUND: The periodontal condition has a reciprocal relationship with rheumatoid arthritis (RA). Rheumatoid arthritis patients are reported to present with more serious periodontal disease (PD) as compared to non-RA patients. OBJECTIVES: This study aimed to evaluate the effects of non-surgical periodontal treatment on Vietnamese patients with active RA and PD, where the clinical characteristics and serum indices of the patients were of interest. MATERIAL AND METHODS: We conducted a randomized clinical trial (RCT) on 82 RA patients with PD. The patients were randomly divided into 2 groups: the intervention group, consisting of patients who received oral hygiene instructions, scaling and root planing; and the control group, consisting of patients who received oral hygiene instructions only. Both groups received the same treatment plan for RA. The Disease Activity Score 28 based on C-reactive protein (DAS28-CRP), disease activity classification, rheumatoid factor (RF), erythrocyte sedimentation rate (ESR), anti-citrullinated protein autoantibodies (ACPAs), and C-reactive protein (CRP) were monitored, with the measurements taken at 3 months and 6 months following the treatment. RESULTS: The 2 groups exhibited similar parameters at baseline. In the intervention group, DAS28-CRP and disease activity classification were significantly reduced at 3 months after treatment as compared to the baseline data. At 6 months following the treatment there was a significant decrease in ESR, ACPAs and DAS28-CRP in the intervention group, while the control group showed a decrease only in ACPAs. Further, when comparing the intervention and control groups at 6 months following the treatment, there were no differences between the groups in the ACPAs, RF and CRP serum levels. CONCLUSIONS: Non-surgical periodontal treatment can significantly reduce DAS28-CRP, disease activity classification, ESR, and the ACPAs level in serum, and can be applied to reduce RA severity in RA patients with PD.

Plasma cells promote osteoclastogenesis and periarticular bone loss in autoimmune arthritis.

In rheumatoid arthritis (RA), osteoclastic bone resorption causes structural joint damage as well as periarticular and systemic bone loss. Periarticular bone loss is one of the earliest indices of RA, often preceding the onset of clinical symptoms via largely unknown mechanisms. Excessive osteoclastogenesis induced by receptor activator of NF-κB ligand (RANKL) expressed by synovial fibroblasts causes joint erosion, whereas the role of RANKL expressed by lymphocytes in various types of bone damage has yet to be elucidated. In the bone marrow of arthritic mice, we found an increase in the number of RANKL-expressing plasma cells, which displayed an ability to induce osteoclastogenesis in vitro. Genetic ablation of RANKL in B-lineage cells resulted in amelioration of periarticular bone loss, but not of articular erosion or systemic bone loss, in autoimmune arthritis. We also show conclusive evidence for the critical contribution of synovial fibroblast RANKL to joint erosion in collagen-induced arthritis on the arthritogenic DBA/1J background. This study highlights the importance of plasma-cell RANKL in periarticular bone loss in arthritis and provides mechanistic insight into the early manifestation of bone lesion induced by autoimmunity.

Stepwise cell fate decision pathways during osteoclastogenesis at single-cell resolution.

Osteoclasts are the exclusive bone-resorbing cells, playing a central role in bone metabolism, as well as the bone damage that occurs under pathological conditions1,2. In postnatal life, haematopoietic stem-cell-derived precursors give rise to osteoclasts in response to stimulation with macrophage colony-stimulating factor and receptor activator of nuclear factor-κB ligand, both of which are produced by osteoclastogenesis-supporting cells such as osteoblasts and osteocytes1-3. However, the precise mechanisms underlying cell fate specification during osteoclast differentiation remain unclear. Here, we report the transcriptional profiling of 7,228 murine cells undergoing in vitro osteoclastogenesis, describing the stepwise events that take place during the osteoclast fate decision process. Based on our single-cell transcriptomic dataset, we find that osteoclast precursor cells transiently express CD11c, and deletion of receptor activator of nuclear factor-κB specifically in CD11c-expressing cells inhibited osteoclast formation in vivo and in vitro. Furthermore, we identify Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 (Cited2) as the molecular switch triggering terminal differentiation of osteoclasts, and deletion of Cited2 in osteoclast precursors in vivo resulted in a failure to commit to osteoclast fate. Together, the results of this study provide a detailed molecular road map of the osteoclast differentiation process, refining and expanding our understanding of the molecular mechanisms underlying osteoclastogenesis.

OPG Production Matters Where It Happened.

Osteoprotegerin (OPG) is a circulating decoy receptor for RANKL, a multifunctional cytokine essential for the differentiation of tissue-specific cells in bone and immune systems such as osteoclasts, medullary thymic epithelial cells (mTECs), and intestinal microfold cells (M cells). However, it is unknown whether OPG functions only at the production site or circulates to other tissues acting in an endocrine fashion. Here we explore the cellular source of OPG by generating OPG-floxed mice and show that locally produced OPG, rather than circulating OPG, is crucial for bone and immune homeostasis. Deletion of OPG in osteoblastic cells leads to severe osteopenia without affecting serum OPG. Deletion of locally produced OPG increases mTEC and M cell numbers while retaining the normal serum OPG level. This study shows that OPG limits its functions within the tissue where it was produced, illuminating the importance of local regulation of the RANKL system.

Relationship between periodontitis and rheumatoid arthritis in Vietnamese patients.

Objective: This study aimed to survey periodontal status of Vietnamese patients with rheumatoid arthritis (RA) and investigates the association between periodontitis and RA in these patients.Materials and methods: We conducted a cross-sectional descriptive study on 150 RA patients and another 150 patients with osteoarthritis (OA). RA was evaluated using the DAS28 disease activity score based on C-reactive protein levels (DAS28-CRP), disease activity classification, and serum levels of RA biomarkers. Periodontal status was determined using periodontal indices.Results: The proportion of periodontitis cases in the RA group was significantly higher than the OA group (67 and 28%, respectively). The rate of severe periodontitis observed in the RA group was also significantly higher than that in the OA group (22.7 and 8%, respectively). RA patients with periodontitis had higher DAS28-CRP scores, disease activity levels, ACPA positivity and higher serum levels of CRP and ACPAs. Periodontitis is associated with an increased risk for RA (odds ratio [OR]: 5.14, 95% confidence interval [CI]: 3.14 - 8.41) and with higher disease activity classification (OR: 2.7, 95% CI: 1.14 - 6.42).Conclusions: Vietnamese RA patients often presented with a more serious periodontal condition than OA patients. We observed an association between periodontal disease (PD) status and clinic symptoms and biochemical/immunological characteristics of RA.

Histone deacetylases and their roles in mineralized tissue regeneration.

Histone acetylation is an important epigenetic mechanism that controls expression of certain genes. It includes non-sequence-based changes of chromosomal regional structure that can alter the expression of genes. Acetylation of histones is controlled by the activity of two groups of enzymes: the histone acetyltransferases (HATs) and histone deacetylases (HDACs). HDACs remove acetyl groups from the histone tail, which alters its charge and thus promotes compaction of DNA in the nucleosome. HDACs render the chromatin structure into a more compact form of heterochromatin, which makes the genes inaccessible for transcription. By altering the transcriptional activity of bone-associated genes, HDACs control both osteogenesis and osteoclastogenesis. This review presents an overview of the function of HDACs in the modulation of bone formation. Special attention is paid to the use of HDAC inhibitors in mineralized tissue regeneration from cells of dental origin.

Simplified conditions for storing and cryopreservation of dental pulp stem cells.

OBJECTIVES: This study aimed to simplify the collection, isolation and cryopreservation procedure of human dental pulp stem cells (DPSCs) to ease the establishment of dental stem cell banking. DESIGN: Extracted third molars were collected and stored either in growth medium or in gentamicin-saline (480µg/ml) for 6, 9 or 12h. DPSCs were isolated and subjected to cryopreservation by a controlled-rate or rapid freezing method in 5 or 10% DMSO. Flow cytometry and growth pattern of DPSCs before and after cryopreservation were conducted. RESULTS: Rate of contamination by which the extracted teeth were stored in control and gentamicin-saline were 9.1% (N=33) and 2.3% (N=43), respectively. Successful cell isolation rate of teeth preserved in gentamicin-saline at 6h (92.9%) was comparable to those of growth media group (90.3%). At 9 and 12h, the rates dropped significantly to 75% and 54%, respectively. Cryopreservation by controlled-rate freezing either in 5 or 10% DMSO resulted in a significantly higher percentage of viable cells than by rapid freezing. Cells conserved by controlled-rate freezing in 5% DMSO showed a pattern of growth similar to control unfrozen cells; 10% DMSO significantly deteriorated the growth pattern of the cells. After thawing, DPSCs conserved by controlled-rate freezing still expressed stemness characteristics, although hematopoietic stem cell markers were slightly increased. CONCLUSION: Gentamicin-saline was effective in preserving human teeth for DPSC isolation. Controlled-rate freezing in 5% DMSO gave the highest rate of cell viability. This study simplifies the storage conditions and proposes a simple method for cryopreservation of DPSCs.