Investigation of a DNA Profiling Method Using Only Cementum More Than 70 Years After Death

Short tandem repeat (STR) typing is widely used not only for blood relationship identification but also for the personal identification of unidentified bodies. However, DNA is susceptible to the effects of environmental factors, consequently leading to reduced DNA yields. Therefore, to maximize the DNA yield required for identification, teeth are generally completely pulverized during DNA extraction. However, this renders subsequent testing after DNA profiling impossible. In this study, we investigated the utility of DNA profiling using only the cementum from teeth that had been left outdoors for long postmortem intervals. We analyzed 90 molars (fresh teeth) that were extracted within six months at a dental clinic and 90 molars (stale teeth) exposed outdoors for over 70 years, and following cementum extraction, the accuracy of STR profiling, optimal site for cementum collection, and minimum amount of cementum required for STR profiling were determined. The results demonstrated that the profiling accuracy of DNA extracted from cementum was comparable to that of DNA from dental pulp and dentin. Furthermore, the collection of cementum from either near the cervical line or from the root apex areas did not show significant differences in DNA profiling accuracy, indicating that securing at least 5 mg of cementum was sufficient to ensure precise DNA profiling. These findings suggest that DNA profiling using only cementum is viable even in teeth that have been subjected to a long postmortem interval.

Runx2 heterozygosity alters homeostasis of the periodontal complex

BACKGROUND AND OBJECTIVE

Haploinsufficiency of Runx2 (Runx2+/- ) causes dental anomalies. However, little is known about the involvement of Runx2 in the maintenance of dentin, cementum, and the periodontal ligament (PDL) during adulthood. This study aimed to observe the effects of Runx2+/- on homeostasis of the periodontal complex.

MATERIALS AND METHODS

A total of 14 three-month-old Runx2+/- mice and their wild-type littermates were examined using micro-computed tomography, histology, and immunohistochemistry. Phenotypic alterations in the dentin, cementum, and PDL were characterized and quantified.

RESULTS

Haploinsufficiency of Runx2 caused cellular changes in the PDL space including reduction of cell proliferation and apoptosis, and irregular attachment of the collagen fibers in the PDL space into the cementum. Absence of continuous thickness of cementum was also observed in Runx2+/- mice.

CONCLUSION

Runx2 is critical for cementum integrity and attachment of periodontal fibers. Because of its importance to cementum homeostasis, Runx2 is essential for homeostasis of periodontal complex.

Acellular Extrinsic Fiber Cementum Is Invariably Present in the Superficial Layer of Apical Cementum in Mouse Molar

The cementum is a highly mineralized tissue that covers the tooth root. The regional differences among the types of cementum, especially in the extrinsic fibers that contribute to tooth support, remain controversial. Therefore, this study used second harmonic generation imaging in conjunction with automated collagen extraction and image analysis algorithms to facilitate the quantitative examination of the fiber characteristics and the changes occurring in these fibers over time. Acellular extrinsic fiber cementum (AEFC) was invariably observed in the superficial layer of the apical cementum in mouse molars, indicating that this region of the cementum plays a crucial role in supporting the tooth. The apical AEFC exhibited continuity and fiber characteristics comparable with the cervical AEFC, suggesting a common cellular origin for their formation. The cellular intrinsic fiber cementum present in the inner layer of the apical cementum showed consistent growth in the apical direction without layering. This study highlights the dynamic nature of the cementum in mouse molars and underscores the requirement for re-examining its structure and roles. The findings of the present study elucidate the morphophysiological features of cementum and have broader implications for the maintenance of periodontal tissue health.

In Vitro Models Used in the Formation of Root Caries Lesions-A Review of the Literature

The management of root caries remains a challenge for clinicians due to its unique anatomical location and structure. There is increasing interest in utilising artificial root caries lesions to develop new strategies for remineralisation. An ideal protocol has not yet been agreed upon. The aim of this review is to provide a structured overview of previously reported in vitro root caries models. The literature was screened and mined for information mainly on substrate selection, model systems utilised, and variables used in the models. Human roots (60%) were the most frequently used substrates, followed by bovine roots (40%). Chemical models (69%) were the most frequently utilised model systems, followed by microbiological models (27%), to form root caries lesions. Acetate buffer solution (80%), pH 5.0 or above (40%), and a demineralisation time of five days (25%) were the common variables used in the chemical systems, while mono-species biofilm was most frequently used (73%) in microbiological models and Streptococcus mutans was the most common bacterial strain utilised in these models (80%). This review highlights the variability amongst the experimental approaches, discusses the advantages and limitations of these approaches, and emphasises that standardisation of experimental conditions along with sustained research will benefit root caries research.

New Insights in Hydrogels for Periodontal Regeneration

Periodontitis is a destructive inflammatory disease characterized by microbial infection that damages the tissues supporting the tooth (alveolar bone, gingiva, periodontal ligament, and cementum), ultimately resulting in the loss of teeth. The ultimate goal of periodontal therapy is to achieve the regeneration of all of the periodontal tissues. Thus, tissue engineering approaches have been evolving from simple membranes or grafts to more complex constructs. Hydrogels are highly hydrophilic polymeric networks with the ability to simulate the natural microenvironment of cells. In particular, hydrogels offer several advantages when compared to other forms of scaffolds, such as tissue mimicry and sustained drug delivery. Moreover, hydrogels can maintain a moist environment similar to the oral cavity. Hydrogels allow for precise placement and retention of regenerative materials at the defect site, minimizing the potential for off-target effects and ensuring that the treatment is focused on the specific defect site. As a mechanism of action, the sustained release of drugs presented by hydrogels allows for control of the disease by reducing the inflammation and attracting host cells to the defect site. Several therapeutic agents, such as antibiotics, anti-inflammatory and osteogenic drugs, have been loaded into hydrogels, presenting effective benefits in periodontal health and allowing for sustained drug release. This review discusses the causes and consequences of periodontal disease, as well as the advantages and limitations of current treatments applied in clinics. The main components of hydrogels for periodontal regeneration are discussed focusing on their different characteristics, outcomes, and strategies for drug delivery. Novel methods for the fabrication of hydrogels are highlighted, and clinical studies regarding the periodontal applications of hydrogels are reviewed. Finally, limitations in current research are discussed, and potential future directions are proposed.

Activation of Wnt signaling in Axin2+ cells leads to osteodentin formation and cementum overgrowth

OBJECTIVES

In this study, we used the mouse incisor model to investigate the regulatory mechanisms of Wnt/β-catenin signaling on Axin2+ cells in tooth development.

MATERIALS AND METHODS

Axin2lacZ/+ reporter mice were used to define the expression pattern of Axin2 in mouse incisors. We traced the fate of Axin2+ cells from postnatal Day 21 (P21) to P56 using Axin2CreERT2/+ and R26RtdTomato/+ reporter mice. For constitutive activation of Wnt signaling, Axin2CreERT2/+ , β-cateninflox(Ex3)/+ , and R26RtdTomato/+ (CA-β-cat) mice were generated to investigate the gain of function (GOF) of β-catenin in mouse incisor growth.

RESULTS

The X-gal staining of Axin2lacZ/+ reporter mice and lineage tracing showed that Axin2 was widely expressed in dental mesenchyme of mouse incisors, and Axin2+ cells were essential cell sources for odontoblasts, pulp cells, and periodontal ligament cells. The constitutive activation of Wnt signaling in Axin2+ cells resulted in the formation of osteodentin featured with increased DMP1 and dispersed DSP expression and overgrowth of cementum.

CONCLUSION

Wnt signaling plays a key role in the differentiation and maturation of Axin2+ cells in mouse incisors.

Differential effects of resolvin D1 and resolvin E1 on cementoblast function

BACKGROUND

Resolvins are endogenous mediators of the resolution of inflammation. They are derived from omega-3 polyunsaturated fatty acid precursors. Resolvin D1 (RvD1) and Resolvin E1 (RvE1) are the best-characterized members for actively promoting periodontal regeneration in experimental animal models. Here, we evaluated the efficacy of RvD1 and RvE1 on cementoblasts, the key cells involved in dental cementum regeneration and the attachment of the tooth to the alveolar bone.

METHODS

Immortalized mouse cementoblasts (OCCM-30) were treated with different concentrations (0.1-1000 ng/mL) of RvD1 and RvE1. Cell proliferation was measured using an electrical impedance-based real-time cell analyzer. Mineralization was evaluated with von Kossa staining. The mRNA expression of mineralized tissue-associated markers of bone sialoprotein (BSP), Type I collagen (COL I), osteocalcin (OCN), osteopontin (OPN), runt-related transcription factor 2 (RunX2), alkaline phosphatase (ALP), osteoprotegerin (OPG), receptor activator of nuclear factor kappa B (NF-κB) (RANK), receptor activator of NF-κB ligand (RANKL), and extracellular matrix-degrading enzymes [matrix metalloproteinase (MMP)-1, MMP-2, MMP-3, MMP-9, and their tissue inhibitors (TIMP-1, TIMP-2)], RvE1 receptor (ChemR23) and RvD1 receptor (ALX/PFR2), cytokines (tumor necrosis factor-alpha {TNF-α}, interleukin {IL}-1β, IL-6, IL-8, IL-10, IL-17), oxidative stress enzymes [superoxide dismutase (SOD), glutathione peroxidase (GPX), and cyclooxygenase-2 (Cox-2)] were analyzed using quantitative polymerase chain reaction (qPCR).

RESULTS

Both RvD1 and RvE1 (10-100 ng/mL) significantly increased the proliferation of cementoblasts and mineralized nodules at all concentrations (p < 0.05). RvE1 increased BSP, RunX2, and ALP compared with the RvD1 dose and time-dependently, while RvD1 and RvE1 differentially regulated COL-I. RvE1 increased OPG mRNA expression, whereas RANK-RANKL mRNA expression decreased by RvE1. MMP-2, MMP-3, MMP-9, TIMP-1, and TIMP-2 expressions were reduced by RvE1 compared with RvD1. Treatment of cementoblasts with RvD1 and RvE1 differentially affected cytokine and oxidative stress enzymes while significantly increasing their receptor expressions (ChemR23 and ALX/PFR2).

CONCLUSIONS

RvD1 and RvE1 regulate proliferation, mineralization, and gene expression in cementoblasts using similar pathways while differentially affecting tissue degradation, suggesting a targeted therapeutic approach for cementum turnover during periodontal regeneration.

Screening of functionalized collagen membranes with a porcine periodontal regeneration model

OBJECTIVES

Current methods for periodontal regeneration do not promote collagen fiber insertions into new bone and cementum. We used a pig wound model to screen different functionalized collagen membranes in promoting periodontal reattachment to root surfaces.

METHODS

Treatment groups included (1) control with no membranes, (2) collagen-coated membranes, (3) membranes with insulin-like growth factor-1 (IGF-1), (4) membranes with amelotin, or (5) membranes attached with calcium phosphate cement (CPC), or with CPC combined with IGF-1. Flap procedures were performed on mandibular and maxillary premolars of each pig.

RESULTS

Histomorphometric, micro-CT, and clinical measurements obtained at 4 and 12 weeks after surgery showed cementum formation on denuded roots and reformation of alveolar bone, indicating that the pig model can model healing responses in periodontal regeneration. Calcium phosphate cement simplified procedures by eliminating the need for sutures and improved regeneration of alveolar bone (p < 0.05) compared with other treatments. There was a reduction (p < 0.05) of PD only for the IGF group. Large observed variances between treatment groups indicated that a priori power analyses should be conducted to optimize statistical analysis.

CONCLUSIONS

Pigs can model discrete elements of periodontal healing using collagen-based, functionalized membranes. Screening indicates that membrane anchorage with calcium phosphate cements improve regeneration of alveolar bone.

Solution NMR structure of cementum protein 1 derived peptide (CEMP1-p1) and its role in the mineralization process

We report the characterization of the three-dimensional structure of the CEMP1-p1 peptide [MGTSSTDSQQAQHRRCSTSN: corresponding to residues 1-20 of the N-terminus of cementum protein 1 (CEMP1)]. This peptide imitates the capacity of CEMP1 to stimulate hydroxyapatite (HA) crystal nucleation and growth, and promotes the differentiation of periodontal ligament cells into a cementoblastic phenotype. Additionally, in experimental models of critical-sized calvarial defects in Wistar rats, CEMP1-p1 has shown osteogenic properties that enhanced the physiological deposition and maturation of newly formed bone. In this work, studies of CEMP1-p1 by circular dichroism (CD) and nuclear magnetic resonance (NMR) were performed in trifluoroethanol D2 (TFED2) and aqueous solution to determine the 3D structure of the peptide. Using the 3D model, experimental data from HA crystals formation and calcium fluorescence emission, we explain the biological mechanisms involved in CEMP1-p1 activity to promote calcium recruitment and its affinity to HA crystals. This information is valuable because it proposes, for the first time, a plausible molecular mechanism during the mineralization process, from a specific cementum protein-derived peptide.

Development, Establishment, and Validation of a Model for the Mineralization of Periodontium Remodelling Cells: Cementoblasts

Chronic kidney disease (CKD) patients undergoing dialysis are at high risk of bone fractures. CKD-induced mineral and bone disorder is extended to periodontal disease due to changes in the ionic composition of saliva in CKD patients, dysregulating mineralization, hindering regeneration and thereby promoting the progression of dental complications. Despite the importance of cementum for overall oral health, the mechanisms that regulate its development and regeneration are not well comprehended, and a lack of sufficient in vitro experimental models has hindered research progress. In this study, the impact of experimental conditions on the calcification of cementoblasts was systematically investigated, aimed at establishing a standardized and validated model for the calcification of cementoblasts. The effects of phosphate, calcium, ascorbic acid, β-glycerolphosphate, dexamethasone, and fetal calf serum on the calcification process of cementoblasts were analyzed over a wide range of concentrations and time points by investigating calcium content, cell viability, gene expression and kinase activity. Cementoblasts calcified in a concentration- and time-dependent manner with higher concentrations of supplements cause a higher degree of calcification but decreased cell viability. Phosphate and calcium have a significantly stronger effect on cementoblast calcification processes compared to osteogenic supplements: ascorbic acid, β-glycerolphosphate, and dexamethasone induce calcification over a wide range of osteogenic signalling pathways, with osteopontin being a central target of gene regulation. Conversely, treatment with ascorbic acid, β-glycerolphosphate, and dexamethasone leads to activating only selected pathways, especially promoting bone sialoprotein expression. The developed and validated cementoblast calcification protocol, incubating up to 60% confluent cementoblasts with 1.9 mmol L-1 of phosphate supplementation for a reasonable, multi-pathway calcification induction and 10 mmol L-1 β-glycerolphosphate, 75 µmol L-1 ascorbic acid and 10 nmol L-1 dexamethasone for a reasonable osteogenic differentiation-based calcification induction, provides standard in vitro experimental models for better understanding cementoblast function and regeneration.

Autophagy mediates cementoblast mineralization under compression through periostin/β-catenin axis

Repair of orthodontic external root resorption and periodontal tissue dysfunction induced by mechanical force remains a clinical challenge. Cementoblasts are vital in cementum mineralization, a process important for restoring damaged cementum. Despite autophagy plays a role in mineralization under various environmental stimuli, the underlying mechanism of autophagy in mediating cementoblast mineralization remains unclear. Here we verified that murine cementoblasts exhibit compromised mineralization under compressive force. Autophagy was indispensable for cementoblast mineralization, and autophagic activation markedly reversed cementoblast mineralization and prevented cementum damage in mice during tooth movement. Subsequently, messenger RNA sequencing analyses identified periostin (Postn) as a mediator of autophagy and mineralization in cementoblasts. Cementoblast mineralization was significantly inhibited following the knockdown of Postn. Furthermore, Postn silencing suppressed Wnt signaling by modulating the stability of β-catenin. Together our results highlight the role of autophagy in cementoblast mineralization via Postn/β-catenin signaling under compressive force and may provide a new strategy for the remineralization of cementum and regeneration of periodontal tissue.

Cementum is key to periodontal tissue regeneration: A review on apatite microstructures for creation of novel cementum-based dental implants

The cementum is the outermost layer of hard tissue covering the dentin within the root portion of the teeth. It is the only hard tissue with a specialized structure and function that forms a part of both the teeth and periodontal tissue. As such, cementum is believed to be critical for periodontal tissue regeneration. In this review, we discuss the function and histological structure of the cementum to promote crystal engineering with a biochemical approach in cementum regenerative medicine. We review the microstructure of enamel and bone while discussing the mechanism underlying apatite crystal formation to infer the morphology of cementum apatite crystals and their complex structure with collagen fibers. Finally, the limitations of the current dental implant treatments in clinical practice are explored from the perspective of periodontal tissue regeneration. We anticipate the possibility of advancing periodontal tissue regenerative medicine via cementum regeneration using a combination of material science and biochemical methods.

A Painless Bump: A Case Report of Cemento-Ossifying Fibroma of the Anterior Maxilla

Cemento-ossifying fibroma (COF) is a benign odontogenic neoplasm. It is considered an ossifying fibroma with traces of interspersed cementum fragments. Here we present a case report of the occurrence of COF in the maxillary anterior region of an elderly woman. A 61-year-old female reported with a painless, progressive, slow-growing swelling on the upper front jaw region for the past five years. A single, localized, swelling on the anterior region of the maxilla which was non-tender and bony hard in consistency. Radiological examination consisting of orthopantomagram (OPG) and cone-beam computed tomography (CBCT) revealed increased thickness of bone over frontal, parietal and maxilla with alteration of trabecular pattern - cotton wool/ground glass. Serum alkaline phosphatase level was found to be 865 U/l, however, serum calcium level and other routine blood investigations (hemogram) were within normal limits. The above radiological and laboratory findings are more in favour of primary bone pathology and with a biopsy later correlating with histopathological findings; it was diagnosed as COF. Under conscious sedation, surgical excision of the bony mass was done along with extraction of associated teeth. The patient is currently on regular follow-up and planning for a dental prosthesis is in progress.

Nanomaterials for Periodontal Tissue Regeneration: Progress, Challenges and Future Perspectives

Bioactive nanomaterials are increasingly being applied in oral health research. Specifically, they have shown great potential for periodontal tissue regeneration and have substantially improved oral health in translational and clinical applications. However, their limitations and side effects still need to be explored and elucidated. This article aims to review the recent advancements in nanomaterials applied for periodontal tissue regeneration and to discuss future research directions in this field, especially focusing on research using nanomaterials to improve oral health. The biomimetic and physiochemical properties of nanomaterials such as metals and polymer composites are described in detail, including their effects on the regeneration of alveolar bone, periodontal ligament, cementum and gingiva. Finally, the biomedical safety issues of their application as regenerative materials are updated, with a discussion about their complications and future perspectives. Although the applications of bioactive nanomaterials in the oral cavity are still at an initial stage, and pose numerous challenges, recent research suggests that they are a promising alternative in periodontal tissue regeneration.

Knockout of Bone Sialoprotein in Cementoblasts Cell Lines Affects Specific Gene Expression in Unstimulated and Mechanically Stimulated Conditions

One of the major components in cementum extracellular matrix is bone sialoprotein (BSP). BSP knockout (Ibsp) mice were reported to have a nonfunctional hypo-mineralized cementum, as well as detachment and disorganization of the periodontal ligament tissue. However, studies investigating the influence of Ibsp in cementoblasts are missing yet. This study investigates the influences of Bsp in three cementoblasts cell lines (OCCM.30-WT,Ibsp^ΔNterm, and Ibsp^KAE). The mRNA expression of cementoblast and osteoclast markers (Col1a1, Alpl, Ocn, Runx2, Ctsk, Rankl and Opg) and the cell morphology were compared. Additionally, a functional monocyte adhesion assay was performed. To understand the influence of external stimuli, the effect of Ibsp was investigated under static compressive force, mimicking the compression side of orthodontic tooth movement. Cementoblasts with genotype Ibsp^ΔNterm and Ibsp^KAE showed slight differences in cell morphology compared to OCCM.30-WT, as well as different gene expression. Under compressive force, the Ibsp cell lines presented expression pattern markers similar to the OCCM.30-WT cell line. However, Cathepsin K was strongly upregulated in Ibsp^ΔNterm cementoblasts under compressive force. This study provides insight into the role of BSP in cementoblasts and explores the influence of BSP on periodontal ligament tissues. BSP markers in cementoblasts seem to be involved in the regulation of cementum organization as an important factor for a functional periodontium. In summary, our findings provide a basis for investigations regarding molecular biology interactions of BSP in cementoblasts, and a supporting input for understanding the periodontal and cellular cementum remodeling.

Assessment of the Periodontal Cementum Ablation Depth during Root Planing by an Er:YAG Laser at Different Energy Densities: An Ex Vivo Study

INTRODUCTION

An important and non-adapted delivered energy of Er:YAG laser can eliminate the total thickness of root cementum during root planing. Conversely, the preservation of a partial layer of cementum covering the roots is vital for any periodontal ligament regeneration. Thus, the assessment of the cementum ablation depth produced by each energy density of Er:YAG laser is essential before considering its use for the periodontal planing and treatment of the cementum and root surfaces.

AIM OF THE STUDY

Assessment of the cementum ablation depth at different energy densities of the Er:YAG laser is the aim of this study.

MATERIALS AND METHODS

A total of 48 human caries free molars were collected and used in this study. Areas to be irradiated were delimited by two longitudinal grooves (0.5 mm depth). Roots were divided randomly into four groups (4 × n = 12). An Er:YAG laser (2.94 µm) was used with a side-firing tip (R600T) with a 600 µm diameter and a frequency of 20 Hz combined with a cooling system of air 6 mL/min and water 4 mL/min. We used a super short pulse mode (SSP: pulse duration: 50 μs). We used a single irradiation passage backward from apex to cervical parts at 1 mm/s with a slight contact and at an angle of 15° to 30° between the tip and the root surface. Different energies were selected: 30 mJ, 40 mJ, 50 mJ, and 60 mJ.

RESULTS

Microscopic observations showed that the average of the ablation depth increased with the increase of the delivered energy from 30 mJ to 60 mJ. Mean values of the ablation depths were respectively as follows: 43.75 ± 4.89 µm for the energy of 30 mJ, 50.05 ± 3.72 µm for 40 mJ, 65.56 ± 10.35 µm for 50 mJ, and 74.80 ± 15.23 µm for 60 mJ. A statistically significant difference existed between the ablation depth of all groups.

CONCLUSION

Based on our results, the depth of cementum debridement is related to the level of the delivered energy. The lowest energy levels (30 mJ and 40 mJ) can ablate the root cementum surface for a variable depth from 43.75 ± 4.89 μm to 50.05 ± 3.72 μm.

Loss of β-catenin causes cementum hypoplasia by hampering cementogenic differentiation of Axin2-expressing cells

BACKGROUND AND OBJECTIVE

Although cementum plays an essential role in tooth attachment and adaptation to occlusal force, the regulatory mechanisms of cementogenesis remain largely unknown. We have previously reported that Axin2-expressing (Axin2⁺ ) mesenchymal cells in periodontal ligament (PDL) are the main cell source for cementum growth, and constitutive activation of Wnt/β-catenin signaling in Axin2⁺ cells results in hypercementosis. Therefore, the aim of the present study was to further evaluate the effects of β-catenin deletion in Axin2⁺ cells on cementogenesis.

MATERIALS AND METHODS

We generated triple transgenic mice to conditionally delete β-catenin in Axin2-lineage cells by crossing Axin2^CreERT2/+ ; R26R^tdTomato/+ mice with β-catenin^flox/flox mice. Multiple approaches, including X-ray analysis, micro-CT, histological stainings, and immunostaining assays, were used to analyze cementum phenotypes and molecular mechanisms.

RESULTS

Our data revealed that loss of β-catenin in Axin2⁺ cells led to a cementum hypoplasia phenotype characterized by a sharp reduction in the formation of both acellular and cellular cementum. Mechanistically, we found that conditional removal of β-catenin in Axin2⁺ cells severely impaired the secretion of cementum matrix proteins, for example, bone sialoprotein (BSP), dentin matrix protein 1 (DMP1) and osteopontin (OPN), and markedly inhibited the differentiation of Axin2⁺ mesenchymal cells into osterix⁺ cementoblasts.

CONCLUSIONS

Our findings confirm the vital role of Axin2⁺ mesenchymal PDL cells in cementum growth and demonstrate that Wnt/β-catenin signaling shows a positive correlation with cementogenic differentiation of Axin2⁺ cells.

Inactivation of Sufu in cementoblasts accelerates external tooth root resorption

Cementum has been empirically regarded as an antiresorptive barrier against tooth roots. However, little is known about the factors of homeostasis and resistant mechanisms of tooth roots against resorption. Here, we investigated cementum factors and their interaction against resorption using transgenic mice exhibiting external cervical root resorption (ECRR). Ectopically thickened cervical cementum caused by functional inactivation of ectonucleotide pyrophosphotase/phosphodiesterase 1 (Enpp1) was susceptible to ECRR with aging. In addition, the inactivation of the suppressor of fused (Sufu), a Hedgehog signaling inhibitor, in cementoblasts led to ECRR. Interestingly, concurrent inactivation of Sufu and Enpp1 in cementoblasts remarkably exacerbated ECRR with higher Rankl expression. Cellular and molecular analyses using cementoblasts and bone marrow-derived macrophages indicated that Dickkopf-related protein 1 (Dkk1) induced by the inactivation of Sufu in cementoblasts has roles in the acceleration of ECRR triggered by Enpp1 inactivation. Using compound mutant mice for concurrent Wntless and Enpp1 inactivation, this synergistic cooperation of Dkk1 and Npp1 for resorption found in double mutant Sufu and Enpp1 mice was confirmed by the reproduction of amplified ECRR. On the basis of these findings, we conclude that proper Npp1 function and sustained Wnt activity in the cervical cementum are essential for the homeostasis of tooth roots against resorption in a physiological state.

A simple, low-cost method to age mammals? An alternative to cementum annuli analysis

One of the most common and ubiquitous methods to age mammals is by counting the cementum annuli in molars, premolars, incisors, or canines. Despite the ubiquity and perceived simplicity of the method, cementum annuli analysis can be time-consuming, expensive, inaccurate, and imprecise, and require specialized equipment. Using beavers (Castor canadensis) as a test species, we developed a straightforward method to age mammals that requires little specialized equipment. The method consists of: (1) digitizing longitudinally sectioned teeth and measuring the proportion of tooth surface area comprised of cementum ("proportion cementum"), (2) evaluating the relationship between proportion cementum and specimen age (determined from either known-age samples or cementum annuli analysis), and (3) using the modeled relationship to estimate the age of other individuals based solely on proportion cementum. The relationship between proportion cementum and age was strongly correlated (R ² = .97-.98 depending on observer), similar between observers, and similar between known-age specimens and those aged via cementum annuli analysis. Using this proportion cementum method, two independent observers accurately predicted the age of 80%-84% of specimens within 0.5 year and 96%-98% within 1 year. We suggest this aging method will likely work with most mammal species given the relatively consistent deposition of cementum throughout mammals' lives and has promise to be a simple and quick alternative to cementum annuli analysis regardless of whether one develops proportion cementum models using known-age specimens or those aged via alternative methods.

Human Dental Pulp Stem Cells Differentiate into Cementoid-Like-Secreting Cells on Decellularized Teeth Scaffolds

Periodontitis is a common inflammatory disease that in some cases can cause tooth loss. Cementum is a mineralized tissue that forms part of the insertion periodontium and serves to fix the teeth to the alveolar bone. In addition, it acts as a reservoir of different growth and differentiation factors, which regulate the biology of the teeth. Cementogenesis is a complex process that is still under investigation and involves different factors, including dentin sialophosphoprotein (DSPP). In this work we studied the role of surface microtopography in the differentiation of human dental pulp stem cells (hDPSCs) into cementoid-like secreting cells. We cultured hDPSCs on decellularized dental scaffolds on either dentin or cementum surfaces. Cell morphology was evaluated by light and electron microscopy. We also evaluated the DSPP expression by immunohistochemistry. The hDPSCs that was cultured on surfaces with accessible dentinal tubules acquired an odontoblastic phenotype and emitted characteristic processes within the dentinal tubules. These cells synthesized the matrix components of a characteristic reticular connective tissue, with fine collagen fibers and DSPP deposits. The hDPSCs that was cultured on cementum surfaces generated a well-organized tissue consisting of layers of secretory cells and dense fibrous connective tissue with thick bundles of collagen fibers perpendicular to the scaffold surface. Intra- and intercellular deposits of DSPP were also observed. The results presented here reinforce the potential for hDPSCs to differentiate in vitro into cells that secrete a cementoid-like matrix in response to the physical stimuli related to the microtopography of contact surfaces. We also highlight the role of DSPP as a component of the newly formed matrix.

L-arginine protects cementoblasts against hypoxia-induced apoptosis through Sirt1-enhanced autophagy

BACKGROUND

L-arginine (L-arg) can reduce apoptosis in a variety of cells. Cementoblast apoptosis is related to root resorption during orthodontic treatment. In the present study, we aimed to study the regulatory effect and potential mechanism of L-arg on cementoblast apoptosis and root resorption.

METHODS

The apoptosis-related mRNA and protein expression of murine cementoblast (OCCM-30) was assessed after L-arg treatment. To investigate the role of Sirtuin 1 (Sirt1) and autophagy in L-arg resistance to cementoblast apoptosis and root absorption, resveratrol, and EX527 were used to activate or inhibit Sirt1, and chloroquine (CQ) was used to inhibit autophagy.

RESULTS

In vitro, L-arg inhibited hypoxia-induced apoptosis in OCCM-30. Further, L-arg increased Sirt1 expression whereas Sirt1 suppression by EX527 reversed the inhibitory effect of L-arg on cell apoptosis. Sirt1 activator resveratrol increased the ratio of microtubule-associated protein light chain 3 (LC3) II/I and decreased the expression of SQSTM1/p62 (p62), suggesting autophagy activation. Autophagy enhancement could reduce apoptosis. Caspase-3 and Bax expression was decreased, and Bcl-2 expression was increased. When autophagy was inhibited by CQ, the positive effects of Sirt1 were attenuated. In vivo, L-arg application reduced root resorption in rats, as demonstrated by decreased root absorption volume. Similarly, L-arg upregulated Sirt1, which activated autophagy in the root resorption model, and less root resorption was observed in the Sirt1 activation group.

CONCLUSION

L-arg reduced cementoblast apoptosis in hypoxia and reduced root resorption induced by loading force in rats, which may be partly mediated by Sirt1-enhanced autophagy.

Between a rock and a hard place: Regulation of mineralization in the periodontium

The periodontium supports and attaches teeth via mineralized and nonmineralized tissues. It consists of two, unique mineralized tissues, cementum and alveolar bone. In between these tissues, lies an unmineralized, fibrous periodontal ligament (PDL), which distributes occlusal forces, nourishes and invests teeth, and harbors progenitor cells for dentoalveolar repair. Many unanswered questions remain regarding periodontal biology. This review will focus on recent research providing insights into one enduring mystery: the precise regulation of the hard-soft tissue borders in the periodontium which define the interfaces of the cementum-PDL-alveolar bone structure. We will focus on advances in understanding the molecular mechanisms that maintain the unmineralized PDL "between a rock and a hard place" by regulating the mineralization of cementum and alveolar bone.

Clinical, Diagnostic and Histological Findings Involving Cheek Teeth Hypercementosis in Nine Horses

Hypercementosis is infrequently reported to affect the cheek teeth of horses and presents as mineral deposits either attached (peripheral) or solitary ovoid (nodular) structures in the tooth bearing region. There is overlap between radiological and histological appearance of hypercementosis, cementoma, and equine odontoclastic tooth resorption and hypercementosis (EOTRH). The clinical presentation, imaging features, surgical management, and histological findings of nine horses that presented for dental lesions and associated hypercementosis of cheek teeth are reported. Horses were 4-15 years old and presented for either nasal discharge or facial swelling. Peripheral and nodular mineral structures were identified using radiographs or computed tomography in six and three horses, respectively. Eight of nine cases involved maxillary cheek teeth. Of six cases with peripheral hypercementosis, three had enlargement of the apical cross-sectional area that was greater than the coronal cross-sectional area thus preventing extraction along the normal eruption pathway and necessitating sectioning (two cases) and repulsion. Nodular hypercementosis lesions were extracted in three of the four cases. Post-extraction complications occurred in five cases; four cases required additional procedures. All horses returned to their intended use, ie riding or pasture. Histology of extracted dental and proliferative mineral material revealed hypercementosis characterized by large sheets of eosinophilic matrix with lacunae (usually empty; presumed artifact) and frequent, irregular, basophilic cement lines. All cases had evidence of chronic inflammation, such as caries, chronic fractures and/or pulpitis. The findings of this case series share many features with previous published descriptions of cementoma and with histological findings of hypercementosis lesions of EOTRH. Further investigation into differentiation of these entities is warranted.

Dynamic alternations of RANKL/OPG ratio expressed by cementocytes in response to orthodontic‑induced external apical root resorption in a rat model

The aim of the present study was to investigate the alterations in the formation of cementocytes in response to orthodontic forces and to evaluate the contribution of these cells in the biological changes of tooth movement and associated root resorption. A total of 90 Sprague Dawley rats were randomly assigned to the control, high force, and low force groups. Intrusion forces of 10 and 50 g were applied on the rat molar to induce tooth intrusion. The tooth movement was observed from 0 to 14 days by micro-computed tomography, bone histometric analysis, tartrate-resistant acid phosphatase staining, as well as reverse transcription-quantitative PCR and immunofluorescence staining assays. The results suggested that under low force conditions, osteoclasts were distributed at a higher frequency on the bone side than on the root side. Under high force conditions, both sides suffered osteoclast infiltration. In the low force group, the cementocytes exhibited downregulated sclerostin (SOST) and osteoprotegerin (OPG) mRNA levels and a lower receptor activator of nuclear factor-κB ligand (RANKL)/OPG ratio over a certain period of time. The expression levels of these genes were lower compared with those of the osteocytes at each time-point. In the high force group, both cementocytes and osteocytes upregulated the SOST and RANKL/OPG ratio on days 7 and 14, while the cementocytes expressed higher levels of SOST mRNA than those noted in the osteocytes. These data suggested that cementocytes responded to the orthodontic force via modulation of the RANKL/OPG ratio and SOST expression. The biological response of cementocytes contributed to the mechanotransduction and homoeostasis of the roots under compression. Excessive forces may act as a negative factor of this regulatory role. These results expand our knowledge on the function of cementocytes.

Concrescence of the right maxillary second and third molars: A case report

Herein, we reported a rare case of concrescence of #17 and #18, including the clinical and imaging findings. After extracting the concrescence, the fistula on #17 gradually disappeared. In addition, we analyzed the histological etiology and clinical diagnosis and treatment of concrescence from the sight of periodontal functional stimulation.

Incremental lines in human acellular tooth cementum - new insights by SEM analysis

BACKGROUND

Tooth cementum covers the surface of the root dentine and is produced and laid down in thin layers continuously throughout life. Functionally, different types of tooth cementum can be distinguished, which can be roughly divided into acellular (primary cementum) and cellular (secondary cementum) forms. One main type is acellular extrinsic fibre cementum (AEFC), which covers the cervical and middle third of the root. Light microscopic examinations of transverse sections of AEFC show lamellar patterns of alternating light and dark lines called growth or incremental lines. Following mammalian research, a seasonal rhythm of incremental line formation is also assumed in humans. Previous attempts at visualising incremental lines in the AEFC by scanning electron microscopy (SEM) were not particularly successful. The aim of the present study was to detect incremental lines in the AEFC and to analyse their underlying structure by SEM.

METHODS

For this purpose, non-embedded and resin-embedded transverse and longitudinal sections of three single-rooted teeth obtained from different patients were investigated. The thin sections were not pre-treated (e.g. by etching, grinding or coating).

RESULTS

Lamellar structures, which could be identified as incremental lines, were detectable in both transverse and longitudinal sections, with transverse orientation in the cross-section and longitudinal orientation in the longitudinal section. The lamellar pattern was created by broad fibre-rich layers alternating with narrow fibre-poor layers. The orientation of the collagen fibres changed from layer to layer from transverse to radial direction. The visibility of the layered structure discovered varied significantly.

CONCLUSIONS

The study demonstrate that it is possible, in principle, to detect incremental lines in AEFC and to identify their basic structure using SEM. Our results suggest that the density and orientation of the fibres play an essential role in the formation of incremental lines. Functional aspects seem to be of particular importance.

Functional Adaptation of LPS-affected Dentoalveolar Fibrous Joints in Rats

INTRODUCTION

The functional interplay between cementum of the root and alveolar bone of the socket is tuned by a uniquely positioned 70-80 µm wide fibrous and lubricious ligament in a dentoalveolar joint (DAJ). In this study, structural and biomechanical properties of the DAJ, periodontal ligament space (PDL-space also known as the joint space), alveolar bone of the socket, and cementum of the tooth root that govern the biomechanics of a lipopolysaccharide (LPS)-affected DAJ were mapped both in space and time.

METHODS

The hemi-maxillae from 20 rats (4 control at 6 weeks of age, 4 control and 4 LPS-affected at 12 weeks of age, 4 control and 4 LPS-affected at 16 weeks of age) were investigated using a hybrid technique; micro-X-ray computed tomography (5 µm resolution) in combination with biomechanical testing in situ. Temporal variations in bone and cementum volume fractions were evaluated. Trends in mineral apposition rates (MAR) in additional six Sprague Dawley rats (3 controls, 3 LPS-affected) were revealed by transforming spatial fluorochrome signals to functional growth rates (linearity factor - RW) of bone, dentin, and cementum using a fast Fourier transform on fluorochrome signals from 100-µm hemi-maxillae sections.

RESULTS

An overall change in LPS-affected DAJ biomechanics (a 2.5-4.5X increase in tooth displacement and 2X tooth rotation at 6 weeks, no increase in displacement and a 7X increase in rotation at 12 weeks; 27% increase in bone effective strain at 6 weeks and 11% at 12 weeks relative to control) was associated with structural changes in the coronal regions of the DAJ (15% increase in PDL-space from 0 to 6 weeks but only 5% from 6 to 12 weeks compared to control). A significant increase (p < 0.05) in PDL-space between ligated and age-matched control was observed. The bone fraction of ligated at 12 weeks was significantly lower than its age-matched control, and no significant differences (p > 0.05) between groups were observed at 6 weeks. Cementum in the apical regions grew faster but nonlinearly (11% and 20% increase in cementum fraction (CF) at 6 and 12 weeks) compared to control. Alveolar bone revealed site-specific nonlinear growth with an overall increase in MAR (108.5 µm/week to 126.7 µm/week after LPS treatment) compared to dentin (28.3 µm/week in control vs. 26.1 µm/week in LPS-affected) and cementum (126.5 µm/week in control vs. 119.9 µm/week in LPS-affected). A significant increase in CF (p < 0.05) in ligated specimens was observed at 6 weeks of age.

CONCLUSIONS

Anatomy-specific responses of cementum and bone to the mechano-chemo stimuli, and their collective temporal contribution to observed changes in PDL-space were perpetuated by altered tooth movement. Data highlight the "resilience" of DAJ function through the predominance of nonlinear growth response of cementum, changes in PDL-space, and bone architecture. Despite the significant differences in bone and cementum architectures, data provided insights into the reactionary effects of cementum as a built-in compensatory mechanism to reestablish functional competence of the DAJ. The spatial shifts in architectures of alveolar bone and cementum, and consequently ligament space, highlight adaptations farther away from the site of insult, which also is another novel insight from this study. These adaptations when correlated within the context of joint function (biomechanics) illustrate that they are indeed necessary to sustain DAJ function albeit being pathological.

A Review of Tissue Engineering for Periodontal Tissue Regeneration

Periodontal disease is one of the most common diagnoses in small animal veterinary medicine. This infectious disease of the periodontium is characterized by the inflammation and destruction of the supporting structures of teeth, including periodontal ligament, cementum, and alveolar bone. Traditional periodontal repair techniques make use of open flap debridement, application of graft materials, and membranes to prevent epithelial downgrowth and formation of a long junctional epithelium, which inhibits regeneration and true healing. These techniques have variable efficacy and are made more challenging in veterinary patients due to the cost of treatment for clients, need for anesthesia for surgery and reevaluation, and difficulty in performing necessary diligent home care to maintain oral health. Tissue engineering focuses on methods to regenerate the periodontal apparatus and not simply to repair the tissue, with the possibility of restoring normal physiological functions and health to a previously diseased site. This paper examines tissue engineering applications in periodontal disease by discussing experimental studies that focus on dogs and other animal species where it could potentially be applied in veterinary medicine. The main areas of focus of tissue engineering are discussed, including scaffolds, signaling molecules, stem cells, and gene therapy. To date, although outcomes can still be unpredictable, tissue engineering has been proven to successfully regenerate lost periodontal tissues and this new possibility for treating veterinary patients is discussed.

3D Mesoscopic Architecture of a Heterogeneous Cellular Network in the Cementum-Periodontal Ligament-Alveolar Bone Complex

Cell-to-cell communication orchestrates various cell and tissue functions. This communication enables cells to form cellular networks with each other through direct contact via intercellular junctions. Because these cellular networks are closely related to tissue and organ functions, elucidating the morphological characteristics of cellular networks could lead to the development of novel therapeutic approaches. The tooth, periodontal ligament (PDL), and alveolar bone form a complex via collagen fibres. Teeth depend on the co-ordinated activity of this complex to maintain their function, with cellular networks in each of its three components. Imaging methods for three-dimensional (3D) mesoscopic architectural analysis include focused ion beam/scanning electron microscopy (FIB/SEM), which is characterised by its ability to select observation points and acquire data from complex tissue after extensive block-face imaging, without the need to prepare numerous ultrathin sections. Previously, we employed FIB/SEM to analyse the 3D mesoscopic architecture of hard tissue including the PDL, which exists between the bone and tooth root. The imaging results showed that the cementum, PDL, and alveolar bone networks are in contact and form a heterogeneous cellular network. This cellular network may orchestrate mechanical loading-induced remodelling of the cementum-PDL-alveolar bone complex as the remodelling of each complex component is coordinated, as exemplified by tooth movement due to orthodontic treatment and tooth dislocation due to occlusal loss. In this review, we summarise and discuss the 3D mesoscopic architecture of cellular networks in the cementum, PDL, and alveolar bone as observed in our recent mesoscopic and morphological studies.

Regeneration of rat periodontium by cementum protein 1-derived peptide

BACKGROUND AND OBJECTIVE

Cementum protein 1 (CEMP1) has the capacity to promote differentiation of periodontal ligament (PDL) cells toward a cementoblastic phenotype in vitro and bone regeneration in vivo. In this study, we tested the capabilities of a synthetic cementum protein 1-derived peptide, MGTSSTDSQQAGHRRCSTSN (CEMP1-p1), to promote regeneration of periodontal structures in a periodontal fenestration defect in rats.

MATERIAL AND METHODS

Fenestration defects were created using an extra-oral approach in the buccal aspect of the mandibular first molar roots. Eighteen male Wistar rats were divided into three groups. Two controls (defects non-treated or defects treated with a gelatin matrix scaffold [GMS] only) and the experimental group treated with 5 µg/dose of CEMP1-p1 embedded in GMS. After 28 days, the animals were sacrificed, and the mandibles processed for histopathological examination. Expression of cementum proteins, cementum attachment protein (CAP), CEMP1, integrin binding sialoprotein (IBSP), and osteocalcin (OCN), was assessed using immunofluorescence. The formation of new cementum, bone, and PDL fibers were compared between control and experimental groups.

RESULTS

The histological analysis revealed that the control group without any treatment new cementum or oriented PDL fibers were not observed. However, the presence of newly bone was detected. In the control group treated with GMS, new cementum formation was not detectable, the PDL fibers were oriented parallel to the longitudinal root axis, and new bone formation was observed. The experimental group showed deposit of acellular extrinsic fiber cementum (AEFC) in a lamellae-like feature with inserted Sharpey's fibers, formation of cellular mixed stratified cementum (CMSC) with the presence of cementocytes, and newly formed bone close to the cementum-enamel junction. Cementoblast cells adjacent to new cementum expressed CAP, CEMP1, IBSP, and OCN.

CONCLUSION

These studies show that CEMP1-p1 promotes the formation of AEFC, CMSC, new PDL with Sharpey's fibers inserted in cementum and bone, thus providing strong evidence that the synthetic peptide CEMP1-p1 promotes periodontal regeneration in a rat fenestration model.

Cemental tear: Literature review, proposed classification and recommendations for treatment

Cemental tears are an important condition of relevance to Endodontics but are often overlooked. A cemental tear is the partial or complete detachment of the cementum from the cemento-dentinal junction or along the incremental line within the body of cementum. The limited attention received is most likely due to the limited awareness amongst dental professionals and challenges in accurately diagnosing them, resulting in misdiagnosis and erroneous treatment. The aim of this review is to describe the: (i) epidemiology and predisposing factors; (ii) clinical, radiographic and histological features and (iii) the clinical management and treatment outcomes of cemental tear. The review included 37 articles published in English that comprised eight observational studies and 29 case reports. The prevalence of cemental tears was reported to be lower than 2%; whilst the incidence remains unknown. Internal factors due to the inherent structural weakness of cementum and its interface with the dentine, and external factors that are associated with stress have been proposed as the two mechanisms responsible for the development and propagation of cemental tears. Predisposing factors that have been implicated were tooth type, gender, age, previous root canal treatment, history of dental trauma, occlusal trauma and excessive occlusal force; however, evidence is limited. Common clinical and radiographic manifestations of cemental tears resemble the presentations of primary endodontic diseases, primary periodontal diseases and combined endodontic-periodontal lesions. Clinical management tended to focus on complete removal of the torn fragments and periodontal treatment, often combined with regenerative treatment. In this article, a new classification for cemental tears is developed that consists of classes 0 to 6 and stages A, B, C and D based on the: (i) location and accessibility of the torn cemental fragment; (ii) the pattern and extension of the associated bony defect in relation to the root length and (iii) the number of root surface/s affected by the cemental tear/s and the associated bony defect. Recommendations for treatment strategies are also provided and linked to the classification to aid in streamlining the process of treatment decision making.

Taurodontism in dental genetics

Taurodontism is a dental anomaly defined by enlargement of the pulp chamber of multirooted teeth with apical displacement of the pulp floor and bifurcation of the roots. Taurodontism can be an isolated trait or part of a syndrome. A study was conducted to document the dental and craniofacial aspects of genetic thin bone disorders in South Africa. Sixty-four individuals with Osteogenesis imperfecta (OI), one individual with Pyle disease and one with Torg-Winchester syndrome respectively, were assessed clinically, radiographically and at a molecular level. Ten patients with OI XI and those with Pyle disease and Torg-Winchester syndrome had taurodontism. Taurodontism has been identified in several genetic disorders necessitating cognizance of the possible existence and implications of this characteristic when managing patients in the dental environment. Further studies should be directed toward identifying the incidence, etiology, and molecular pathways leading to taurodontism and its relationship to genetic syndromes.

Compressive force regulates cementoblast migration via downregulation of autophagy

BACKGROUND

Migration of cementoblasts to resorption lacunae is the foundation for repairing root resorption during orthodontic tooth movement. Previous studies reported that autophagy was activated by compression in periodontal ligament cells. The aim of this study was to investigate the migration of cementoblasts and determine whether autophagy is involved in the regulation of cementoblast migration under compressive force.

METHODS

Flow cytometry was employed to examine the apoptosis of murine cementoblasts (OCCM-30) at different compression times (0, 6, 12, and 24 hours) and magnitudes (0, 1.0, 1.5, and 2.0 g/cm² ). Cell proliferation was examined using the CCK-8 method. Wound healing migration assays and transwell migration assays were performed to compare the migration of cementoblasts. Chloroquine (CQ) and rapamycin were used to inhibit and activate autophagy, respectively. The level of autophagy was determined using western blotting and immunofluorescence staining. The expression of matrix metalloproteinases (MMPs) was assessed using quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blot analysis, and enzyme-linked immunosorbent assay (ELISA).

RESULTS

Cell apoptosis and proliferation did not significantly change in OCCM-30 cells under mechanical compression at magnitude of 1.5 g/cm² for 12 hours. However, the migration of cementoblasts was significantly inhibited after the application of compressive force. MMP2, MMP9, and MMP13 mRNA expression was decreased, and MMP9 and MMP13 protein expression and secretion level were also decreased. Further, autophagic activity was inhibited in cementoblasts under compressive force. Treatment with chloroquine reduced the cellular migration, and rapamycin partially relieved the inhibition of cementoblast migration induced by the compressive force. MMP9 and MMP13 mRNA expression, protein expression, and secretion levels showed a similar trend.

CONCLUSION

Migration of OCCM-30 cells was inhibited under compressive force partially dependent on the inhibition of MMPs, which was mediated by downregulation of autophagy. The findings provide new insights into the role of autophagy in biological behaviors of cementoblasts under compressive force and a potential therapeutic strategy for reducing external root resorption.

Histological analysis of ankylothecodonty in Silesauridae (Archosauria: Dinosauriformes) and its implications for the evolution of dinosaur tooth attachment

Dinosaurs possess a form of tooth attachment wherein an unmineralized periodontal ligament suspends each tooth within a socket, similar to the condition in mammals and crocodylians. However, little information is known about tooth attachment and implantation in their close relatives, the silesaurids. We conducted a histological survey of several silesaurid taxa to determine the nature of tooth attachment in this phylogenetically and paleoecologically important group of archosaurs. Our histological data demonstrate that these early dinosauriforms do not exhibit the crocodilian/dinosaur condition of a permanent gomphosis, nor the rapid ankylosis that is plesiomorphic for amniotes. Instead, all sampled silesaurids exhibit delayed ankylosis, a condition in which teeth pass through a prolonged stage where the teeth are suspended in sockets by a periodontal ligament, followed by eventual mineralization and fusion of the tooth to the jaws. This suggests that tooth attachment in crocodylians and dinosaurs represent the further retention of an early ontogenetic stage compared to silesaurids, a paedomorphic trend that is mirrored in the evolution of synapsid tooth attachment. It also suggests that the dinosaur and crocodylian gomphosis was convergently acquired via heterochrony or, less likely, that the silesaurid condition represents a reversal to a plesiomorphic state. Moreover, if Silesauridae is nested within Ornithischia, a permanent gomphosis could be convergent between the two main dinosaur lineages, Ornithischia and Saurischia. These results demonstrate that dental characters in early archosaur phylogenies must be chosen and defined carefully, taking into account the relative duration of the different phases of dental ontogeny.

Application of Adipose Tissue Stem Cells in Regenerative Dentistry: A Systematic Review

AIM

The aim of this study was to systematically review the applications of adipose tissue stem cells (ADSCs) in regenerative dentistry.

MATERIALS AND METHODS

An electronic search was conducted in Medline (PubMed) and Scopus databases. The original research associated with the role of ADSCs in regeneration of alveolar bone, periodontal ligament (PDL), cementum as well as the dental pulp was evaluated. Among the included studies, three animal studies and one human study had low risk of bias.

RESULTS

A total of 33 relevant studies were included in the review. The animal models, in vivo human, and in vitro studies revealed that ADSCs had a significant osteogenic differentiation potential. Besides, they had potential to differentiate into PDL, cementum, and dental pulp tissue.

CONCLUSION

The ADSCs may be specifically applied for bone tissue engineering in the management of alveolar bone defects, specifically in dental implants and periodontal disease. However, their role in regeneration of PDL, cementum, and dental pulp requires further investigations. Overall, their applications in regenerative dentistry needs further verification through human clinical trials.

Effects of Active Vitamin D or FGF23 Antibody on Hyp Mice Dentoalveolar Tissues

Mutations in the PHEX gene lead to X-linked hypophosphatemia (XLH), a form of inherited rickets featuring elevated fibroblast growth factor 23 (FGF23), reduced 1,25-dihydroxyvitamin D (1,25D), and hypophosphatemia. Hyp mutant mice replicate the XLH phenotype, including dentin, alveolar bone, and cementum defects. We aimed to compare effects of 1,25D versus FGF23-neutralizing antibody (FGF23Ab) monotherapies on Hyp mouse dentoalveolar mineralization. Male Hyp mice, either injected subcutaneously with daily 1,25D or thrice weekly with FGF23 blocking antibody from 2 to 35 d postnatal, were compared to wild-type (WT) controls and untreated Hyp mice. Mandibles were analyzed by high-resolution micro-computed tomography (micro-CT), histology, and immunohistochemistry. Both interventions maintained normocalcemia, increased serum phosphate levels, and improved dentoalveolar mineralization in treated versus untreated Hyp mice. 1,25D increased crown dentin volume and thickness and root dentin/cementum volume, whereas FGF23Ab effects were limited to crown dentin volume. 1,25D increased bone volume fraction, bone mineral density, and tissue mineral density in Hyp mice, whereas FGF23Ab failed to significantly affect these alveolar bone parameters. Neither treatment fully attenuated dentin and bone defects to WT levels, and pulp volumes remained elevated regardless of treatment. Both treatments reduced predentin thickness and improved periodontal ligament organization, while 1,25D promoted a more profound improvement in acellular cementum thickness. Altered cell densities and lacunocanalicular properties of alveolar and mandibular bone osteocytes and cementocytes in Hyp mice were partially corrected by either treatment. Neither treatment normalized the altered distributions of bone sialoprotein and osteopontin in Hyp mouse alveolar bone. Moderate improvements from both 1,25D and FGF23Ab treatment regimens support further studies and collection of oral health data from subjects receiving a newly approved anti-FGF23 therapy. The inability of either treatment to fully correct Hyp mouse dentin and bone prompts further experiments into underlying pathological mechanisms to identify new therapeutic approaches.

A Biphasic Feature of Gli1+-Mesenchymal Progenitors during Cementogenesis That Is Positively Controlled by Wnt/β-Catenin Signaling

Cementum, a specialized bony layer covering an entire molar root surface, anchors teeth into alveolar bone. Gli1, a key transcriptional activator in Hedgehog signaling, has been identified as a mesenchymal progenitor cell marker in various tissues, including the periodontal ligament (PDL). To address the mechanisms by which Gli1⁺ progenitor cells contribute to cementogenesis, we used the Gli1^lacZ/+ knock-in line to mark Gli1⁺ progenitors and the Gli1^CreERT2/+; R26R^tdTomato/+ line (named Gli1^Lin) to trace Gli1 progeny cells during cementogenesis. Our data unexpectedly displayed a biphasic feature of Gli1⁺ PDL progenitor cells and cementum growth: a negative relationship between Gli1⁺ progenitor cell number and cementogenesis but a positive correlation between Gli1-derived acellular and cellular cementoblast cell number and cementum growth. DTA-ablation of Gli1^Lin cells led to a cementum hypoplasia, including a significant reduction of both acellular and cellular cementoblast cells. Gain-of-function studies (by constitutive stabilization of β-catenin in Gli1^Lin cells) revealed a cementum hyperplasia. A loss of function (by conditional deletion of β-catenin in Gli1⁺ cells) resulted in a reduction of postnatal cementum growth. Together, our studies support a vital role of Gli1⁺ progenitor cells in contribution to both types of cementum, in which canonical Wnt/β-catenin signaling positively regulates the differentiation of Gli1⁺ progenitors to cementoblasts during cementogenesis.

Histochemical characterization of bone and cementum using modified gallego's iron fuschin stain and van gieson stain and its application in fibro-osseous lesions

Objectives

Fibro-osseous lesions (FOLs) of the jaws exhibit an overlapping histomorphologic spectrum with respect to nature of calcifications. Sometimes these calcifications may be difficult to characterize as bone and cementum on routine Hematoxylin and Eosin (H&E) staining. This causes difficulty in assessing the origin and diagnosis of these lesions. Thus the study aimed to characterize bone, cementum, and hard tissue components in FOLs using special stains.

Method

The study included a histochemical evaluation of 20 samples of bone and cementum and 12 cases each of fibrous dysplasia (FD) and ossifying fibroma (OF). Three consecutive sections of each tissue were stained with H and E, modified Gallego's iron fuschin stain and Van Gieson stain. H and E and modified Gallego's iron fuschin stained sections were analyzed under light microscope whereas Van Gieson stained section was analyzed under polarizing microscope.

Results

It was found that cementum stained red and bone stained greenish-yellow in color. The calcifications seen in fibrous dysplasia stained greenish-yellow in color. Three cases of OF showed greenish-yellow calcifications and nine cases showed reddish calcifications. Polarization study of bone showed lamellar pattern and tooth cementum showed quilt pattern. Four cases of FD showed lamellar pattern and eight cases showed haphazard pattern. In OF, three cases showed lamellar pattern and nine cases quilt pattern.

Conclusion

Calcifications having lamellar pattern and greenish-yellow color suggest their osteogenic origin thus having aggressive nature and requiring aggressive treatment. Calcifications having quilt pattern and reddish color suggest periodontal ligament origin thus having less aggressive behavior and less extensive treatment.

Cementoblastoma of a primary molar: A rare pediatric occurrence

Cementoblastoma is a relatively uncommon, benign odontogenic mesenchymal tumor that is associated with and attached to the roots of teeth. It is considered to be the only true neoplasm of cemental origin. Its prevalence has been reported to vary from 0.69% to 8% of all odontogenic tumors. The tumor is frequently seen in the second and third decades of life and affects the molar and premolar regions of the mandible predominantly. We herein describe a case of cementoblastoma occurring in association with primary teeth in a 5-year-old male patient with a brief review of literature. Only 20 cases of cementoblastoma involving primary teeth were found after the English literature search, the current case being the 21^st. Moreover, the deciduous teeth-associated cementoblastomas (14 out of 20) show a distinct predilection for the right side of the face. The current case is the seventh one to involve the left side.

Inflammation in the Human Periodontium Induces Downregulation of the α1- and β1-Subunits of the sGC in Cementoclasts

Nitric oxide (NO) binds to soluble guanylyl cyclase (sGC), activates it in a reduced oxidized heme iron state, and generates cyclic Guanosine Monophosphate (cGMP), which results in vasodilatation and inhibition of osteoclast activity. In inflammation, sGC is oxidized and becomes insensitive to NO. NO- and heme-independent activation of sGC requires protein expression of the α₁- and β₁-subunits. Inflammation of the periodontium induces the resorption of cementum by cementoclasts and the resorption of the alveolar bone by osteoclasts, which can lead to tooth loss. As the presence of sGC in cementoclasts is unknown, we investigated the α₁- and β₁-subunits of sGC in cementoclasts of healthy and inflamed human periodontium using double immunostaining for CD68 and cathepsin K and compared the findings with those of osteoclasts from the same sections. In comparison to cementoclasts in the healthy periodontium, cementoclasts under inflammatory conditions showed a decreased staining intensity for both α₁- and β₁-subunits of sGC, indicating reduced protein expression of these subunits. Therefore, pharmacological activation of sGC in inflamed periodontal tissues in an NO- and heme-independent manner could be considered as a new treatment strategy to inhibit cementum resorption.

In Vitro Study of Surface Changes Induced on Enamel and Cementum by Different Scaling and Polishing Techniques

PURPOSE

To determine how the currently available techniques of scaling and root planing, used either alone or with additional polishing techniques, affect the substance thickness and surface roughness of enamel and cementum.

MATERIALS AND METHODS

After extraction, impacted third molars were prepared and subjected to air polishing with a nonabrasive powder, ultrasonic scaling, or hand instrumentation. All three techniques were performed alone and in combinations for a total of 9 treatment groups. The control group consisted of untreated surfaces. Optical microcoordination measurements were conducted to separately assess substance loss, mean roughness depth (Rz), and roughness average (Ra) on enamel and cementum. The Rz results were analysed using a t-test for paired samples.

RESULTS

Air polishing alone and with additional rubber-cup polishing using a paste were the only two approaches which caused no enamel loss. Both groups also entailed less cementum loss (≤ 20 μm) than any of the other seven groups, and both yielded the most favorable Rz results on enamel. Air polishing alone was the only group to reveal no significant change in Rz from untreated cementum (p = 0.999). The other 8 approaches statistically significantly reduced the surface roughness of cementum (p ≤ 0.017).

CONCLUSION

Air polishing with a nonabrasive powder yielded the best hard-tissue preservation. Combining any of the scaling techniques with additional polishing was not beneficial; on the contrary, they caused even more abrasion of hard tissue on both enamel and cementum.

Tooth attachment and pleurodont implantation in lizards: Histology, development, and evolution

Squamates present a unique challenge to the homology and evolution of tooth attachment tissues. Their stereotypically pleurodont teeth are fused in place by a single "bone of attachment", with seemingly dubious homology to the three-part tooth attachment system of mammals and crocodilians. Despite extensive debate over the interpretations of squamate pleurodonty, its phylogenetic significance, and the growing evidence from fossil amniotes for the homology of tooth attachment tissues, few studies have defined pleurodonty on histological grounds. Using a sample of extant squamate teeth that we organize into three broad categories of implantation, we investigate the histological and developmental properties of their dental tissues in multiple planes of section. We use these data to demonstrate the specific soft- and hard-tissue features of squamate teeth that produce their disparate tooth implantation modes. In addition, we describe cementum, periodontal ligaments, and alveolar bone in pleurodont squamates, dental tissues that were historically thought to be restricted to extant mammals and crocodilians. Moreover, we show how the differences between pleurodonty and thecodonty do not relate to the identity of the tooth attachment tissues, but rather the arrangements of homologous tissues around the teeth.

Synchrotron radiation-based X-ray tomography reveals life history in primate cementum incrementation

Cementum is a mineralized dental tissue common to mammals that grows throughout life, following a seasonally appositional rhythm. Each year, one thick translucent increment and one thin opaque increment is deposited, offering a near-complete record of an animal's life history. Male and female mammals exhibit significant differences in oral health, due to the contrasting effects of female versus male sex hormones. Oestrogen and progesterone have a range of negative effects on oral health that extends to the periodontium and cementum growth interface. Here, we use synchrotron radiation-based X-ray tomography to image the cementum of a sample of rhesus macaque (Macaca mulatta) teeth from individuals of known life history. We found that increased breeding history in females corresponds with increased increment tortuosity and less organized cementum structure, when compared to male and juvenile cementum. We quantified structural differences by measuring the greyscale 'texture' of cementum and comparing results using principal components analysis. Adult females and males occupy discrete regions of texture space with no overlap. Females with known pregnancy records also have significantly different cementum when compared with non-breeding and juvenile females. We conclude that several aspects of cementum structure and texture may reflect differences in sexual life history in primates.

Remodelling compartment in root cementum

Bone remodelling represents the most remarkable bone response to mechanical stress and mineral homeostasis. It is the consequence of complex highly orchestrated and tightly regulated cellular processes taking place in a specialized entity - the Bone Remodelling Compartment (BRC). Cementum is an understudied tissues that requires more research to understand its biology, pathology, and potential for regeneration. Although analogue to bone in structure and composition distinct structural and functional differences were ascribed to each of these mineralized tissues. The precise role of cementocytes in cementum turnover is unclear but they may work the same way as osteocytes in bone remodelling, regulating the full process. Although cementum is not liable to regular physiological remodelling as bone is, pathological cases triggered by orthodontic forces or large periapical periodontitis, those lesions can acutely induce cementum remodelling. Nevertheless, the cellular mechanisms behind this particular remodelling process are yet to be identified, as its eventual involvement of specialized anatomic structures as the BRC. Hypothesizing that similar cellular mechanisms underlie bone and cementum remodelling, the present work shows, for the first time, the histological evidence of a specialized remodelling compartment in dental hard tissues.

Tooth-Supporting Hard Tissue Regeneration Using Biopolymeric Material Fabrication Strategies

The mineralized tissues (alveolar bone and cementum) are the major components of periodontal tissues and play a critical role to anchor periodontal ligament (PDL) to tooth-root surfaces. The integrated multiple tissues could generate biological or physiological responses to transmitted biomechanical forces by mastication or occlusion. However, due to periodontitis or traumatic injuries, affect destruction or progressive damage of periodontal hard tissues including PDL could be affected and consequently lead to tooth loss. Conventional tissue engineering approaches have been developed to regenerate or repair periodontium but, engineered periodontal tissue formation is still challenging because there are still limitations to control spatial compartmentalization for individual tissues and provide optimal 3D constructs for tooth-supporting tissue regeneration and maturation. Here, we present the recently developed strategies to induce osteogenesis and cementogenesis by the fabrication of 3D architectures or the chemical modifications of biopolymeric materials. These techniques in tooth-supporting hard tissue engineering are highly promising to promote the periodontal regeneration and advance the interfacial tissue formation for tissue integrations of PDL fibrous connective tissue bundles (alveolar bone-to-PDL or PDL-to-cementum) for functioning restorations of the periodontal complex.

Cellular network across cementum and periodontal ligament elucidated by FIB/SEM tomography

Cementocytes in cementum form a lacuna-canalicular network. However, the 3D ultrastructure and range of the cementocyte network are unclear. Here, the 3D ultrastructure of the cementocyte network at the interface between cementum and periodontal ligament (PDL) was investigated on the mesoscale using FIB/SEM tomography. The results revealed a cellular network of cementocytes and PDL cells. A previous histomorphological study revealed the osteocyte-osteoblast-PDL cellular network. We extended this knowledge and revealed the cementum-PDL-bone cellular network, which may orchestrate the remodeling and modification of periodontal tissue, using a suitable method for imaging of complex tissue.

Nucleation and growth inhibition of biological minerals by cementum attachment protein-derived peptide (CAP-pi)

Biomineralization is a highly regulated process where proteins/peptides-crystal interactions contribute to the shaping, phasing and aggregation of minerals. We have identified and synthesized a cementum attachment protein-derived peptide (CAP-pi), which corresponds to amino acids 40-53 of the N-terminal CAP domain (MASSDEDGTNGGAS) and its phosphorylated variant (MASpSpDEDGTNGGASp) (CAP-pip). The peptide is composed of polar and negatively charged amino acids, which are disordered, according to in silico analysis. Our results show that CAP-pi inhibits hydroxyapatite (HA) formation and growth. However, it possesses low capacity to inhibit calcium oxalate crystal growth. CAP-pip showed a stronger inhibitory effect on the formation and growth of HA. As well as a high capacity to inhibit calcium oxalate monohydrate growth, mainly due to adsorption on specific growth faces. Small peptides have many advantages over the full-size protein, including low-cost production and modulation characteristics that allow for structural changes. Our findings suggest that CAP-pip-derived peptide could possess therapeutic potential to prevent or treat pathological calcifications such as renal stones and vascular calcification.

Establishment of in vitro three-dimensional cementocyte differentiation scaffolds to study orthodontic root resorption

Orthodontic-induced root resorption is a severe side effect that can lead to tooth root shortening and loss. Compressive force induces tissue stress in the cementum that covers the tooth root, which is associated with activation of bone metabolism and cementum resorption. To investigate the role of cementocytes in mechanotransduction and osteoclast differentiation, the present study established an in vitro three-dimensional (3D) model replicating cellular cementum and observed the effects of static compression on the cellular behavior of the cementocytes. Cell Counting Kit-8 assay, alkaline phosphatase staining and dentin matrix protein 1 quantification were used to evaluate the cementocyte differentiation in the 3D scaffolds. Cellular viability under static compression was evaluated using live/dead staining, and expression of mineral metabolism-related genes were analyzed via reverse transcription-quantitative PCR. The results suggested that the cementocytes maintained their phenotype and increased the expression of osteoprotegerin (OPG), receptor activator of NF-κB ligand (RANKL) and sclerostin (SOST) in the 3D model compared with cells cultured in two dimensions. Compression force increased cell death and induced osteoclastic differentiation via the upregulation of SOST and RANKL/OPG ratio, and the downregulation of osteocalcin. The effect of compression showed a force magnitude-dependent pattern. The present study established an in vitro model of cellular cementum to study the biology of cementocytes. The results indicated that cementocytes are sensitive to mechanical loading and may serve potential roles in the metabolic regulation of minerals during orthodontic root resorption. These findings provide a novel tool to study biological processes in the field of orthodontics and expand knowledge of the biological function of cementocytes.

Glycosaminoglycans accelerate biomimetic collagen mineralization in a tissue-based in vitro model

Mammalian teeth are attached to the jawbone through an exquisitely controlled mineralization process: unmineralized collagen fibers of the periodontal ligament anchor directly into the outer layer of adjoining mineralized tissues (cementum and bone). The sharp interface between mineralized and nonmineralized collagenous tissues makes this an excellent model to study the mechanisms by which extracellular matrix macromolecules control collagen mineralization. While acidic phosphoproteins, localized in the mineralized tissues, play key roles in control of mineralization, the role of glycosaminoglycans (GAGs) is less clear. As several proteoglycans are found only in the periodontal ligament, it has been hypothesized that these inhibit mineralization of collagen in this tissue. Here we used an in vitro model based on remineralization of mouse dental tissues to determine the role of matrix GAGs in control of mineralization. GAGs were selectively removed from demineralized mouse periodontal sections via enzymatic digestion. Proteomic analysis confirmed that enzymatic GAG removal does not significantly alter protein content. Analysis of remineralized tissue sections by transmission electron microscopy (TEM) shows that GAG removal reduced the rate of remineralization in mineralized tissues compared to the untreated control, while the ligament remained unmineralized. Protein removal with trypsin also reduced the rate of mineralization, but to a lesser extent than GAG removal, despite a much larger effect on protein content. These results indicate that GAGs promote mineralization in mineralized dental tissues rather than inhibiting mineral formation in the ligament, which may have broader implications for understanding control of collagen mineralization in connective tissues.