Dental cementum: the dynamic tissue covering of the root

Investigating the surface topography of human acellular and cellular tooth cementum by atomic force microscopy

INTRODUCTION

Dental cementum plays a key role in maintaining the health and functional integrity of teeth throughout an individual's life. While different cementum types are distinguished according to location and function, their specific properties are not yet fully understood.

OBJECTIVE

The study aimed to compare the structural properties of different types of tooth cementum by analysing their surface texture using tapping mode atomic force microscopy (TM-AFM).

METHODS

Transverse and longitudinal sections of five anterior teeth extracted from four male individuals were prepared and analysed by TM-AFM (Core AFM) both with and without hydrochloric acid etching. The TM-AFM measurements were further analysed using the Gwyddion software to determine the roughness parameters (root mean square of height irregularities and mean roughness).

RESULTS

The acid-etched sections exhibited distinctive features with regard to fibre structure and orientation compared to the unetched sections, with fundamental differences between acellular and cellular cementum. In contrast to acellular extrinsic fibre cementum (AEFC), cellular intrinsic fibre cementum (CIFC) showed increased roughness values after acid etching, with some variability, both between teeth and between subjects. The relative percentage difference (RPD) between the cementum types varied between 11.4 % in unetched transverse sections and up to 89.8 % in etched sections. The AEFC images revealed finely branched fibres between radial Sharpey's fibre bundles.

CONCLUSION

Our results show that TM-AFM imaging combined with acid etching is a suitable technique for characterising the surface texture of different types of tooth cementum.

Progress in Basic Research and Clinical Strategies for Cementum Regeneration

Periodontitis is a chronic inflammatory disease that inflicts damage to periodontal tissues, leading to loss of teeth, and affects systemic health. Traditional treatments can delay inflammation, whereas regeneration of the periodontal complex (periodontal ligament, cementum, and alveolar bone) can better restore periodontal tissue function. In recent years, the regeneration of alveolar bone and the periodontal ligament has been widely reviewed although cementum has received less attention. As an avascular mineralised structure around the tooth, cementum can anchor periodontal ligament fibres to the root surface, thereby connecting teeth to alveolar bone. The supporting and stabilizing effects of cementum make its regeneration vital for restoring the functionality of the periodontal tissues. In this review, we discuss advancements in basic and clinical research appertaining to cementum regeneration. We describe the molecular mechanisms that contribute to cementum regeneration thereby providing a foundation for further basic research. Finally we summarise the clinical strategies employed for cementum regeneration, including regenerative surgery and utilisation of growth factors and stem cells.

12 real forensic cases solved by the DNA STR-typing of skeletal remains exposed to extreme environment conditions, without the conventional bone pulverization step

DNA identification of human skeletal remains play a valuable role in the forensic field, especially in missing persons and mass disasters investigation. Hard tissues, such as bones and teeth, represent a very common kind of samples analyzed in forensic laboratories because often they are the only biological materials remaining. However, the major limitation in using these compact samples rely on time consuming and labor-intensive treatment of grinding them into powder before proceeding with the conventional DNA purification and extraction step. In this context, a novel DNA extraction assay, called the TBone Ex kit (DNA Chip Research Inc.), was developed to digests bone chips without powdering "as reported by Kitayama (JAMA 12:84-89, 2010)." Here, we simultaneously analyzed bone and tooth samples obtained by our police laboratory that belonged to 15 different forensic cases from Sardinia (Italy). The total of 27 samples were recovered from different scenarios and were exposed to extreme environmental factors, including sunlight, seawater, soil, fauna, vegetation and high temperature and humidity. The TBone Ex kit was used prior to the EZ2 DNA extraction kit on the EZ2 Connect Fx instrument (Qiagen), and high quality autosomal and Y-chromosome STRs profiles were obtained for the 80% of the cases, in a relatively short time frame. This study provides additional support for the use of the TBone Ex kit for digesting bone fragments/whole teeth as an effective alternative to pulverization protocols. We empirically demonstrated the effectiveness of the kit in processing multiple bone samples simultaneously, largely simplifying the DNA extraction procedure, and the good yield of recovered DNA for downstream genetic typing in highly compromised forensic real specimens. In conclusion, the results of this study appear useful for forensic laboratories, to which the various actors of the criminal justice system - such as potential jury members, judges, defense attorneys and prosecutors - require immediate feedback.

Maxillary Dental Anatomy and Physiology: Endodontic and Periodontal

The maxillary sinus floor is formed by the alveolar process of the maxilla. Frequently, the roots of maxillary molars and premolars may protrude into the sinus cavity, with only a thin membrane separating them. Endodontic infections are characterized by mixed biofilms of anaerobic and proteolytic bacteria that can infect the root canal space and accessory anatomy of those teeth producing apical periodontitis. Due to the close relationship with the maxillary sinus, the persistence of apical periodontitis could potentially lead to odontogenic sinusitis. Understanding maxillary sinus anatomy and its relationship with the posterior maxillary dentition is crucial for diagnosing this entity.

Coronal Cementum and Reduced Enamel Epithelium on Occlusal Surface of Impacted Wisdom Tooth in a Human

Background: There is only limited research on the coronal cementum of a tooth, and the mechanisms of its forming process are not well-defined. This report presents a coronal cementum on the occlusal surfaces of enamel in an impacted wisdom tooth in a human, which is not nearly the cervical portion. Materials and Methods: The tooth (Tooth #1) was derived from a 46-year-old female. Histological analysis, including hematoxylin and eosin (HE) and toluidine blue (TB) staining, and Scanning Electron Microscopy and Energy Dispersive X-ray Spectrometer (SEM-EDS) analysis of the extracted tooth were conducted. Radiographic examination showed that Tooth #1 was horizontally impacted in the maxilla and had the apex of a single root placed between the buccal and palatal roots of Tooth #2. Results: Coronal cementum was distributed widely on the enamel, and reduced enamel epithelium was also found with enamel matrix proteins histologically. The formation of acellular cementum was observed to be more predominant than that of the cellular cementum in Tooth #1. SEM showed that the occlusal cementum connected directly with enamel. Calcium mapping revealed an almost similar occlusal cementum and enamel. In addition, the spectrum of elements in coronal cementum resembled the primary cementum according to SEM-EDS. Discussion: Thus, coronal cementogenesis in impacted human teeth might be related to the existence of reduced enamel epithelium.

PTX3 promotes cementum formation and cementoblast differentiation via HA/ITGB1/FAK/YAP1 signaling pathway

Cementum is a vital component of periodontium, yet its regeneration remains a challenge. Pentraxin 3 (PTX3) is a multifunctional glycoprotein involved in extracellular matrix remodeling and bone metabolism regulation. However, the role of PTX3 in cementum formation and cementoblast differentiation has not been elucidated. In this study, we initially observed an increase in PTX3 expression during cementum formation and cementoblast differentiation. Then, overexpression of PTX3 significantly enhanced the differentiation ability of cementoblasts. While conversely, PTX3 knockdown exerted an inhibitory effect. Moreover, in Ptx3-deficient mice, we found that cementum formation was hampered. Furthermore, we confirmed the presence of PTX3 within the hyaluronan (HA) matrix, thereby activating the ITGB1/FAK/YAP1 signaling pathway. Notably, inhibiting any component of this signaling pathway partially reduced the ability of PTX3 to promote cementoblast differentiation. In conclusion, our study indicated that PTX3 promotes cementum formation and cementoblast differentiation, which is partially dependent on the HA/ITGB1/FAK/YAP1 signaling pathway. This research will contribute to our understanding of cementum regeneration after destruction.

Population differences in dental cementum growth rates: Implications for using cementum thickness as a method for age estimation

OBJECTIVES

Age at death estimation is a key element to many research questions in biological anthropology, archeology, and forensic science. Dental cementum is a tissue of choice for the estimation of age at death in adult individuals as it continues deposition for the entirety of an individual's life. Previous works have devised regression formulas correlating cementum thickness to age at death. However, interpopulation variances are unknown, and it is therefore not clear whether regressions based on a single population are applicable to individuals with different ancestries.

MATERIALS AND METHODS

Here, we use a sample (n = 52) of teeth from individuals with known age at tooth extraction/death of European, African, and East Asian ancestry to assess whether there are interpopulations differences in cementum growth rate. We measured growth rate in four different areas (2nd and 5th decile of both the lingual and buccal aspect of the root) of each tooth and used nonparametric tests to evaluate population differences in growth rate between homologous regions of the teeth.

RESULTS

The results of the analyses show that, even after controlling for tooth size, individuals of European ancestry have significantly lower growth rates than those of both African and East Asian ancestry across all four tooth areas.

DISCUSSION

These results call into question the applicability of the regression formulas derived from European ancestry individuals to individuals of other ancestries.

Platr3/NUDT21/NF-κB Axis Mediates P. gingivalis-Suppressed Cementoblast Mineralization

Porphyromonas gingivalis (P. gingivalis) is one of the major pathogens causing periodontitis and apical periodontitis (AP). Long noncoding RNA (lncRNA) can regulate cellular mineralization and inflammatory diseases. The aim of this study was to investigate the role and mechanism of lncRNA in P. gingivalis-stimulated cementoblast mineralization. In vivo, C57BL/6 mice were divided into the healthy, the AP, and AP + P. gingivalis groups (n = six mice per group). Micro computed tomography, immunohistochemistry staining, and fluorescence in situ hybridization were used to observe periapical tissue. In vitro, cementoblasts were treated with osteogenic medium or P. gingivalis. Pluripotency associated transcript 3 (Platr3), interleukin 1 beta (IL1B), and osteogenic markers were analyzed by quantitative real-time polymerase chain reaction and western blot. RNA pull-down and RNA immunoprecipitation assays were used to detect proteins that bind to Platr3. RNA sequencing was performed in Platr3-silenced cementoblasts. In vivo, P. gingivalis promoted periapical tissue destruction and IL1B expression, but inhibited Platr3 expression. In vitro, P. gingivalis facilitated IL1B expression (P < 0.001), whereas suppressed the expression of Platr3 (P < 0.001) and osteogenic markers (P < 0.01 or 0.001). In contrast, Platr3 overexpression alleviated the repressive effect of P. gingivalis on cementoblast mineralization (P < 0.01 or 0.001). Furthermore, Platr3 bound to nudix hydrolase 21 (NUDT21) and regulated the nuclear factor-κB (NF-κB) signaling pathway. Knocking down NUDT21 suppressed osteogenic marker expression and activated the above signaling pathway. Collectively, the results elucidated that Platr3 mediated P. gingivalis-suppressed cementoblast mineralization through the NF-κB signaling pathway by binding to NUDT21.

Novel Resin-Based Antibacterial Root Surface Coating Material to Combat Dental Caries

Root caries caused by cariogenic bacteria are a burden on a large number of individuals worldwide, especially the elderly. Applying a protective coating to exposed root surfaces has the potential to inhibit the development of caries, thus preserving natural teeth. This study aimed to develop a novel antibacterial coating to combat root caries and evaluate its effectiveness using the antibacterial monomer dimethylaminohexadecyl methacrylate (DMAHDM). DMAHDM was synthesized and incorporated into a resin consisting of 55.8% urethane dimethacrylate (UDMA) and 44.2% TEG-DVBE (UV) at a 10% mass fraction of glass filler. Multiple concentrations of DMAHDM were tested for their impact on the resin's mechanical and physical properties. S. mutans biofilms grown on resin disks were analyzed for antibacterial efficacy. Cytotoxicity was assessed against human gingival fibroblasts (HGFs). The results showed an 8-log reduction in colony-forming units (CFUs) against S. mutans biofilm (mean ± sd; n = 6) (p < 0.05) when 5% DMAHDM was incorporated into the UV resin. There was a 90% reduction in metabolic activity and lactic acid production. A low level of cytotoxicity against HGF was observed without compromising the physical and mechanical properties of the resin. This coating material demonstrated promising physical properties, potent antibacterial effects, and low toxicity, suggesting its potential to protect exposed roots from caries in various dental procedures and among elderly individuals with gingival recession.

Tooth acellular extrinsic fibre cementum incremental lines in humans are formed by parallel branched Sharpey's fibres and not by its mineral phase

In humans, the growth pattern of the acellular extrinsic fibre cementum (AEFC) has been useful to estimate the age-at-death. However, the structural organization behind such a pattern remains poorly understood. In this study tooth cementum from seven individuals from a Mexican modern skeletal series were analyzed with the aim of unveiling the AEFC collagenous and mineral structure using multimodal imaging approaches. The organization of collagen fibres was first determined using: light microscopy, transmission electron microscopy (TEM), electron tomography, and plasma FIB scanning electron microscopy (PFIB-SEM) tomography. The mineral properties were then investigated using: synchrotron small-angle X-ray scattering (SAXS) for T-parameter (correlation length between mineral particles); synchrotron X-ray diffraction (XRD) for L-parameter (mineral crystalline domain size estimation), alignment parameter (crystals preferred orientation) and lattice parameters a and c; as well as synchrotron X-ray fluorescence for spatial distribution of calcium, phosphorus and zinc. Results show that Sharpey's fibres branched out fibres that cover and uncover other collagen bundles forming aligned arched structures that are joined by these same fibres but in a parallel fashion. The parallel fibres are not set as a continuum on the same plane and when they are superimposed project the AEFC incremental lines due to the collagen birefringence. The orientation of the apatite crystallites is subject to the arrangement of the collagen fibres, and the obtained parameter values along with the elemental distribution maps, revealed this mineral tissue as relatively homogeneous. Therefore, no intrinsic characteristics of the mineral phase could be associated with the alternating AEFC incremental pattern.

Inducing the "re-development state" of periodontal ligament cells via tuning macrophage mediated immune microenvironment

INTRODUCTION

Periodontal regeneration, specifically the restoration of the cementum-periodontal ligament (PDL)-alveolar bone complex, remains a formidable challenge in the field of regenerative dentistry. In light of periodontal development, harnessing the multi-tissue developmental capabilities of periodontal ligament cells (PDLCs) and reinitiating the periodontal developmental process hold great promise as an effective strategy to foster the regeneration of the periodontal complex.

OBJECTIVES

This study aims to delve into the potential effects of the macrophage-mediated immune microenvironment on the "developmental engineering" regeneration strategy and its underlying molecular mechanisms.

METHODS

In this study, we conducted a comprehensive examination of the periodontium developmental process in the rat mandibular first molar using histological staining. Through the induction of diverse immune microenvironments in macrophages, we evaluated their potential effects on periodontal re-development events using a cytokine array. Additionally, we investigated PDLC-mediated periodontal re-development events under these distinct immune microenvironments through transcriptome sequencing and relevant functional assays. Furthermore, the underlying molecular mechanism was also performed.

RESULTS

The activation of development-related functions in PDLCs proved challenging due to their declined activity. However, our findings suggest that modulating the macrophage immune response can effectively regulate PDLCs-mediated periodontium development-related events. The M1 type macrophage immune microenvironment was found to promote PDLC activities associated with epithelial-mesenchymal transition, fiber degradation, osteoclastogenesis, and inflammation through the Wnt, IL-17, and TNF signaling pathways. Conversely, the M2 type macrophage immune microenvironment demonstrated superiority in inducing epithelium induction, fibers formation, and mineralization performance of PDLCs by upregulating the TGFβ and PI3K-Akt signaling pathway.

CONCLUSION

The results of this study could provide some favorable theoretical bases for applying periodontal development engineering strategy in resolving the difficulties in periodontal multi-tissue regeneration.

The action of microbial collagenases in dentinal matrix degradation in root caries and potential strategies for its management: a comprehensive state-of-the-art review

Conventional views associate microbial biofilm with demineralization in root caries (RC) onset, while research on their collagenases role in the breakdown of collagen matrix has been sporadically developed, primarily in vitro. Recent discoveries, however, reveal proteolytic bacteria enrichment, specially Porphyromonas and other periodontitis-associated bacteria in subgingivally extended lesions, suggesting a potential role in RC by the catabolism of dentin organic matrix. Moreover, genes encoding proteases and bacterial collagenases, including the U32 family collagenases, were found to be overexpressed in both coronal and root dentinal caries. Despite these advancements, to prove microbial collagenolytic proteases' definitive role in RC remains a significant challenge. A more thorough investigation is warranted to explore the potential of anti-collagenolytic agents in modulating biofilm metabolic processes or inhibiting/reducing the size of RC lesions. Prospective treatments targeting collagenases and promoting biomodification through collagen fibril cross-linking show promise for RC prevention and management. However, these studies are currently in the in vitro phase, necessitating additional research to translate findings into clinical applications. This is a comprehensive state-of-the-art review aimed to explore contributing factors to the formation of RC lesions, particularly focusing on collagen degradation in root tissues by microbial collagenases.

Masticatory habits of the adult Neanderthal individual BD 1 from La Chaise-de-Vouthon (France)

OBJECTIVES

The analysis of dental wear provides a useful approach for dietary and cultural habit reconstructions of past human populations. The analysis of macrowear patterns can also be used to better understand the individual chewing behavior and to investigate the biomechanical responses during different biting scenarios. The aim of this study is to evaluate the diet and chewing performance of the adult Neanderthal Bourgeois-Delaunay 1 (BD 1) and to investigate the relationship between wear and cementum deposition under mechanical demands.

MATERIALS AND METHODS

The macrowear pattern of BD 1 was analyzed using the occlusal fingerprint analysis method. We propose a new method for the bilateral measurement of the cementum volume along both buccal and lingual sides of the molar root.

RESULTS

BD 1's anterior dentition is more affected by wear compared to the posterior one. The macrowear pattern suggest a normal chewing behavior and a mixed-diet coming from temperate environments. The teeth on the left side of the mandible display greater levels of wear, as well as the buccal side of the molar crowns. The cementum analysis shows higher buccal volume along the molar roots.

DISCUSSION

BD1 could have been preferably chewing on the left side of the mandible. The exploitation of various food resources suggested by the macrowear analysis is compatible with the environmental reconstructions. Finally, the greater wear on the buccal side of the molar occlusal surface and the greater volume of cementum in that side of the molar roots offers a preliminary understanding about the potential correlation between dental wear and cementum deposition.

Variability in human tooth cementum thickness reflecting functional processes

OBJECTIVE

The aim of this study was to investigate the thickness of acellular extrinsic fibre cementum (AEFC) at four root positions of anterior and posterior teeth with special focus on functional aspects. Furthermore, the correlations between cementum thickness and chronological age and sex are investigated.

BACKGROUND

While numerous studies confirm continuous cementum apposition with age, masticatory forces as well as physiological and orthodontically induced tooth movements also have the potential to affect tooth cementum thickness.

MATERIALS AND METHODS

Undecalcified teeth were embedded in resin and transverse-sectioned in the cervical third of the root. Two sections per root were selected, and digital images at four positions were obtained (mesial, distal, oral, and vestibular) using light microscopy. The AEFC thickness of 99 teeth (anterior = 66, posterior = 33, male = 54, female = 45) were measured in both sections. The differences in mean values between root positions and the association of root position variation with tooth type, age, sex, and subject as well as the overall effects of age and sex were analysed using a mixed model.

RESULTS

First incisors and canines showed the greatest mean AFEC thickness, in contrast to premolars which had the lowest values. Differences were found across the four root positions, with a pattern varying considerably between anterior and posterior teeth and between maxilla and mandible in the anterior teeth. An interaction between root position and subject pointed to the existence of an individual component in the variation of AEFC thickness across the four root positions. There was an age trend with an almost linear increase in cementum thickness of 1 μm per year. Overall, females tended to exhibit a significantly lesser AEFC thickness compared to males.

CONCLUSIONS

Distinct differences in the pattern of thickness values across the four root positions in anterior and posterior teeth support the assumption that the AEFC is strongly affected by functional processes. In addition to sex-specific differences and age-related trends, the root position variation of AEFC thickness varies from individual to individual.

The anatomy, neurophysiology, and cellular mechanisms of intradental sensation

Somatosensory innervation of the oral cavity enables the detection of a range of environmental stimuli including minute and noxious mechanical forces. The trigeminal sensory neurons underlie sensation originating from the tooth. Prior work has provided important physiological and molecular characterization of dental pulp sensory innervation. Clinical dental experiences have informed our conception of the consequence of activating these neurons. However, the biological role of sensory innervation within the tooth is yet to be defined. Recent transcriptomic data, combined with mouse genetic tools, have the capacity to provide important cell-type resolution for the physiological and behavioral function of pulp-innervating sensory neurons. Importantly, these tools can be applied to determine the neuronal origin of acute dental pain that coincides with tooth damage as well as pain stemming from tissue inflammation (i.e., pulpitis) toward developing treatment strategies aimed at relieving these distinct forms of pain.

The essential role of Mkx in periodontal ligament on the metabolism of alveolar bone and cementum

Introduction

The periodontium is a connective tissue which consists of periodontal ligament, alveolar bone, cementum and gingiva. Periodontal ligament (PDL) is a specialized connective tissue that connects the cementum - coating the surface of the tooth - to the alveolar bone. Mohawk homeobox (Mkx) is a transcription factor that is expressed in PDL, that is known to play a vital role in the development and homeostasis of PDL. A detailed functional analysis of Mkx in the periodontal ligament for alveolar bone and cementum metabolism has not yet been conducted.

Materials and methods

Alveolar bone height, bone mineral density (BMD) and bone volume fractions (Bone volume/Total volume: BV/TV) were measured and analyzed using micro-computed tomography (Micro-CT) and 3DBon on 7-week-old male wild-type (WT) (Mkx+/+) (n = 10) and Mkx-knockout (Mkx-/-) (n = 6) rats. Hematoxylin and Eosin (H&E), tartrate-resistant acid phosphatase (TRAP), alkaline phosphatase (ALP) and Masson Trichrome staining were performed on 5, 6, and 7-week-old Mkx+/+ and Mkx-/- rats. Cementum surface area and the number of TRAP-positive osteoclasts/mm were quantified, measured, and compared for 5,6 and 7-week-old Mkx+/+ and Mkx-/- rats (n = 3 each).

Results

The level of alveolar bone height was significantly higher in Mkx-/- rats than in Mkx+/+ rats. On the other hand, there was significantly less BMD in Mkx-/- alveolar bone. A significant increase in cellular cementum could be observed as early as 5 weeks in Mkx-/- rats when compared with Mkx+/+ rats of the same age. More TRAP-positive osteoclasts were observed in Mkx-/- rats.

Conclusion

Our findings further reveal the essential roles of Mkx in the homeostasis of the periodontal tissue. Mkx was found to contribute to bone and cementum metabolism and may be essential to the prevention of diseases such as periodontitis, and could show potential in regenerative treatments.

Matrix Metalloproteinases in the Periodontium-Vital in Tissue Turnover and Unfortunate in Periodontitis

The extracellular matrix (ECM) is a complex non-cellular three-dimensional macromolecular network present within all tissues and organs, forming the foundation on which cells sit, and composed of proteins (such as collagen), glycosaminoglycans, proteoglycans, minerals, and water. The ECM provides a fundamental framework for the cellular constituents of tissue and biochemical support to surrounding cells. The ECM is a highly dynamic structure that is constantly being remodeled. Matrix metalloproteinases (MMPs) are among the most important proteolytic enzymes of the ECM and are capable of degrading all ECM molecules. MMPs play a relevant role in physiological as well as pathological processes; MMPs participate in embryogenesis, morphogenesis, wound healing, and tissue remodeling, and therefore, their impaired activity may result in several problems. MMP activity is also associated with chronic inflammation, tissue breakdown, fibrosis, and cancer invasion and metastasis. The periodontium is a unique anatomical site, composed of a variety of connective tissues, created by the ECM. During periodontitis, a chronic inflammation affecting the periodontium, increased presence and activity of MMPs is observed, resulting in irreversible losses of periodontal tissues. MMP expression and activity may be controlled in various ways, one of which is the inhibition of their activity by an endogenous group of tissue inhibitors of metalloproteinases (TIMPs), as well as reversion-inducing cysteine-rich protein with Kazal motifs (RECK).

Cemental and alveolar bone defects after chronic exposure to amoxicillin in rats (histopathologic and radiographic study)

OBJECTIVES

This study aimed to shed new light on the potential detrimental effects on cementum and adjacent alveolar bone after chronic exposure to amoxicillin.

METHODS

Six pregnant adult Albino rats were equally divided into two groups. Saline solution and amoxicillin (100 mg/Kg) were given to rats of control and amoxicillin group, respectively from the 13th to the 21st day of pregnancy. The same treatment was given to the pups till the 42nd day. The cementum of the first molar teeth and the surrounding alveolar bone were examined qualitatively by histopathological and scanning electron microscope, and quantitatively by energy dispersive X-ray spectroscopy and cone beam computed tomography.

RESULTS

Amoxicillin group depicted cemental and alveolar bone defects along with resorption lacunae. Statistically significant decreases in calcium and calcium/phosphorus ratio in cementum and in calcium only in alveolar bone were evident (p ≤ 0.05). Overall cementum and alveolar bone densities also showed statistically significant decreases (p ≤ 0.05).

CONCLUSION

Chronic amoxicillin administration displayed destructive effects on cementum and the surrounding alveolar bone which may disturb tooth attachment integrity. Therefore, it is recommended to minimize its haphazard usage during pregnancy and early childhood.

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.

Unraveling the Life History of Past Populations through Hypercementosis: Insights into Cementum Apposition Patterns and Possible Etiologies Using Micro-CT and Confocal Microscopy

The "teeth-as-tools" hypothesis posits that Neanderthals used their anterior teeth as a tool or a third hand for non-dietary purposes. These non- or para-masticatory activities (e.g., tool-making or food preparation prior to ingestion) have also been described in other past and extant human populations, and other Primates. Cementum is the mineralized tissue that covers the tooth root surface and anchors it to the alveolar bone. Under certain conditions (e.g., mechanical stress, infection), its production becomes excessive (i.e., beyond the physiological state) and is called 'hypercementosis'. Several studies in dental anthropology have established a correlation between the teeth-as-tools and hypercementosis. The present work aims to characterize the different patterns of cementum apposition on archeological teeth and discuss their supposed etiology. Using microtomography and confocal microscopy, the patterns of cementum apposition (i.e., thickness, location, and surface characteristics) were analyzed in 35 hypercementotic teeth (Sains-en-Gohelle, France; 7th-17th c. A.D.). Four groups were identified with distinct hypercementosis patterns: (1) impacted, (2) infected, (3) hypofunctional, and (4) hyperfunctional teeth. Characterizing hypercementosis can contribute to documenting the oral health status (paleopathology) and/or masticatory activity of individuals, even from isolated teeth. This has implications for the study of fossil hominins, particularly Neanderthals, known for their use of anterior teeth as tools and frequent and substantial occurrence of hypercementosis.

Attenuation of orthodontically induced inflammatory root resorption by using low-intensity pulsed ultrasound as a therapeutic modality- a systematic review

Ultrasound is an effective tool for both diagnostic and therapeutic applications. As an imaging tool, ultrasound has mostly been used for real-time noninvasive diagnostic imaging. As ultrasound propagates through a material, a reflected radio-frequency (RF) signal is generated when encountering a mismatch in acoustic impedance. While traditionally recognized for its diagnostic imaging capabilities, the application of ultrasound has broadened to encompass therapeutic interventions, most notably in the form of Low-Intensity Pulsed Ultrasound (LIPUS). Low-Intensity Pulsed Ultrasound (LIPUS) is a form of mechanical energy transmitted transcutaneously by high-frequency acoustic pressure waves. The intensity of LIPUS (30 mW/cm2) is within the range of ultrasound intensities used for diagnostic purposes (1-50 mW/cm2) and is regarded as non-thermal, non-destructive, permeating living tissues and triggering a cascade of biochemical responses at the cellular level. The LIPUS device produces a 200 µs burst of 1.5 MHz acoustic sine waves, that repeats at a modulation frequency of 1 kHz and provides a peak pressure of 30 mW/cm2. Low-intensity pulsed ultrasound (LIPUS) forms one of the currently available non-invasive healing-enhancing devices besides electro-stimulation (pulsed electro-magnetic field, PEMF). This modality has been leveraged to enhance drug delivery, expedite injury recovery, improve muscle mobility, alleviate joint stiffness and muscle pain, and enhance bone fracture healing. Although LIPUS has been embraced within various medical disciplines, its integration into standard dental practices is still in its nascent stages, signifying an unexplored frontier with potentially transformative implications. Low-intensity pulsed ultrasound (LIPUS) has emerged as an attractive adjuvant therapy in various dental procedures, such as orthodontic treatment and maxillary sinus augmentation. Its appeal lies in its simplicity and non-invasive nature, positioning LIPUS as a promising avenue for clinical innovation. One particular area of interest is orthodontically induced inflammatory root resorption (OIIRR), an oftenunavoidable outcome of the orthodontic intervention, resulting in the permanent loss of root structure. Notably, OIIRR is the second most common form of root resorption (RR), surpassed only by root resorption related to pulpal infection. Given the high prevalence and potential long-term consequences of OIIRR, this literature review seeks to evaluate the efficacy of LIPUS as a therapeutic approach, with an emphasis on assessing its capacity to reduce the severity of OIIRR to a level of clinical significance. To conduct this systematic review, a comprehensive automated literature search was executed across multiple databases, including MEDLINE, Embase, PsycINFO, Web of Knowledge, Scopus, CINAHL, LILACS, SciELO, Cochrane, PubMed, trials registries, 3ie, and Google Scholar. Both forward and backward citation tracking was employed, encompassing studies published from database inception through January 2009 to April 2023. The review focused on randomized controlled trials (RCTs) that specifically evaluated the effects of low-intensity pulsed ultrasound therapy on orthodontically induced inflammatory root resorption (OIIRR), without restrictions of publication date. A stringent selection criterion was applied, and only studies demonstrating high levels of statistical significance were included. Ultimately, fourteen studies met the inclusion criteria and were subjected to further analysis. The overall quality of the included randomized controlled trials (RCTs) was rigorously assessed utilizing the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. This analysis revealed certain methodological limitations that posed challenges in drawing definitive conclusions from the available evidence. Despite these constraints, the review offers invaluable insights that can inform and guide future research. Specifically, it delineates recommendations for targeted populations, necessary interventions, appropriate outcome measures, suitable study designs, and essential infrastructure to facilitate further investigations. The synthesis of these insights aims to enhance the development and application of low-intensity pulsed ultrasound therapy within the field of dentistry, thereby contributing to improved patient outcomes.

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.

[Patterns of hypercementosis and their relationship with possible local etiological factors in radiographs of individuals from a mexican population]

Objective

Hypercementosis (HPC) is an asymptomatic pathology that, according to the existing literature, has a low prevalence, there is a lack of information and research on it, within these studies, few are made by ethnic groups. To determine the prevalence and radiographic patterns of this condition, as well as the analysis of the relationship of the pathology with some of what are considered possible local triggering factors (FDL) in Mexican individuals.

Methodology

1193 orthopantomographies (OPG) were analyzed, randomly selected from patients of both sexes, with a chronological age range between 18 and 90 years, identifying the prevalence of HPC, as well as its relationship between age groups, its morphological patterns (focal, diffuse and sleeve-shaped), its distribution by anatomical region and dental organs (ODs) and the association of its presence with possible local triggering factors.

Results

348 DO with HPC were found in a total of 194 patients (16.30%), with no relevant differences between genders (P> 0.05). There was a significant increase with respect to the presence of HPC in relation to the increase in the age of the patients (P= 0.001), finding it present in 10% of the age group <40 years, in 20.30% in the group of 40 to 60 years and > 60 in 30.20%. It was found more frequently in a diffuse form (75.28%), followed by the focal pattern (19.54%) and finding the sleeve-shaped morphology less common (5.17%). The mandible presented the greatest number of ODs with the presence of HPC, 136 (39.08%), with the left side being the most affected with 86 OD. The dental group with the greatest involvement was that of molars and premolars.

Conclusions

The prevalence of hypercementosis was 16.30% in the Mexican individuals evaluated. Its presence increases as the age of the patients advances. Its main location is the mandibular region with a predilection for premolars and molars. Even though the idiopathic origin is the most frequent, it was observed that dental impaction is a possible local triggering factor.

Hypercementosis in Late Pleistocene Homo sapiens fossils from Klasies River Main Site, South Africa

OBJECTIVE

To examine early Homo sapiens fossils from the Late Pleistocene site of Klasies River Main Site, South Africa for evidence of hypercementosis. The specimens represent seven adult individuals dated to between 119,000 and 58,000 years ago. These observations are contextualized in relation to the incidences of hypercementosis among recent human populations and fossil human samples and the potential etiologies of hypercementosis.

DESIGN

The fossils were investigated utilizing micro-CT and nano-CT scanning to visualize and measure cementum apposition on permanent incisor, premolar and molar roots. Cementum thickness was measured at mid-root level, and the volume of the cementum sleeve was calculated for the two fossil specimens that display marked hypercementosis.

RESULTS

Two of the fossils display no evidence of cementum hypertrophy. Three exhibit moderate cementum thickening, barely attaining the quantitative threshold for hypercementosis. Two evince marked hypercementosis. One of the Klasies specimens with marked hypercementosis is judged to be an older individual with periapical abscessing. The second specimen is a younger adult, and seemingly similar in age to other Klasies fossils that exhibit only minimal cementum apposition. However, this second specimen exhibits dento-alveolar ankylosis of the premolar and molars.

CONCLUSIONS

These two fossils from Klasies River Main Site provide the earliest manifestation of hypercementosis in Homo sapiens.

Periodontal regeneration: Lessons from the periodontal ligament-cementum junction in diverse animal models

The attachment of the roots of mammalian teeth of limited eruption to the jawbone is reliant in part on the mineralization of collagen fibrils of the periodontal ligament (PDL) at their entry into bone and cementum as Sharpey's fibers. In periodontitis, a high prevalence infection of periodontal tissues, the attachment apparatus of PDL to the tooth root is progressively destroyed. Despite the pervasiveness of periodontitis and its attendant healthcare costs, and regardless of decades of research into various possible treatments, reliable restoration of periodontal attachment after surgery is not achievable. Notably, treatment outcomes in animal studies have often demonstrated more positive regenerative outcomes than in human clinical studies. Conceivably, defining how species diversity affects cementogenesis and cementum/PDL regeneration could be instructive for informing novel and more efficacious treatment strategies. Here we briefly review differences in cementum and PDL attachment in commonly used animal models to consider how species differences may lead to enhanced regenerative outcomes.

M2 macrophages with inflammation tropism facilitate cementoblast mineralization

BACKGROUND

Cementum regeneration was regarded as the critical goal for periodontal regeneration, and M2 macrophage-based therapy was expected to be a promising strategy. However, little is known about the effects of M2 macrophages on cementoblast mineralization and tropism, especially under inflammation. Here we investigated for the first time the crosstalk between M2 macrophages and Porphyromonas gingivalis (Pg)-stimulated cementoblasts.

METHODS

M2 macrophages were induced with interleukin (IL)-4, and identified. CC-chemokine ligand 2 (CCL2) expression and secretion of inflammatory cementoblasts were detected by reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), western blotting (WB), immunohistochemistry for apical periodontitis (AP) mice, and by enzyme-linked immunosorbent assay. Crystal violet staining was used to observe macrophage migration. Conditional medium (CM) and transwell coculture methods were applied to evaluate the effects of M2 macrophages on cementum mineralization with or without Pg, and to explore the mechanism. Mineralization-related markers and pathway-related proteins were measured by RT-qPCR and WB.

RESULTS

M2 macrophages were identified successfully. We found an increase of CCL2 in cementoblasts and their supernatant. Also, higher CCL2 in cementoblasts was observed in the AP model. Superior recruitment of M2 macrophages to supernatant from Pg-stimulated cementoblasts or CCL2-containing medium was verified. Moreover, CM2 and Trans-M2 showed better mineralization-accelerating and rescuing effects when compared to their controls, and application of p38 inhibitor partially blocked the promotion.

CONCLUSIONS

Our study demonstrated the inflammation-targeting and mineralization-promoting effects of M2 macrophages on cementoblasts, which may provide evidence for M2 macrophage-based cementum regeneration.

Insights into the aetiologies of hypercementosis: A systematic review and a scoring system

OBJECTIVES

This paper aims to better define hypercementosis, investigate its described potential aetiologies, and determine whether there are different patterns of cementum apposition and if they are a function of their supposed aetiology.

DESIGN

A literature review was undertaken using the Medline, DOSS, Scopus and Cochrane Library electronic databases. Two co-authors selected the published works independently, extracted the data in accordance with the PRISMA statement.

RESULTS

Among 546 articles, 75 articles were finally selected. Eight different supposed aetiologies were identified: (1) intensive masticatory effort, (2) systemic disease, (3) carious lesion and apical periodontitis, (4) impaction, (5) periodontal disease, (6) concrescence, (7) super-eruption, and (8) drugs. Some of these aetiologies can be combined in the same tooth. Hypercementosis manifestations are various in nature and extent with different patterns that may be aetiology-specific. To improve the description and associated consistency in the characterisation of hypercementosis, in this review but also in future studies, we propose a new qualitative scoring system to quickly characterise hypercementosis and determine its most relevant aetiology.

CONCLUSIONS

This systematic review demonstrates that hypercementosis is a complex and not yet well-defined condition. Some forms of apposition are specific to a given aetiology. The hypercementosis characterisation may contribute to document the oral condition and/or the individuals masticatory activity.

Effect of silver nanoparticles associated with fluoride on the progression of root dentin caries in vitro

OBJECTIVES

To assess the anti-proteolytic effect and potential to inhibit dentin root caries progression of a silver nanoparticle and fluoride solution (CNanoF) in comparison to silver diamine fluoride (SDF).

METHODS

48 specimens of root dentin artificial caries lesion were treated with 38% SDF, CNanoF, CNano or F (n = 6 per group). Ph cycling with demineralization and remineralization solutions simulated caries lesion progression. In addition, specimens were incubated with or without bacterial collagenase in the remineralization solution to induce dentin proteolytic degradation. Dentin degradation was assessed by weight loss rate and hydroxyproline (Hyp) release. Changes in cross-sectional microhardness, and lesion permeability and collagen integrity as determined by confocal laser scanning microscopy indicated potential for further demineralization inhibition. The effect of the solutions on the activity of metalloproteinases (MMP) -2 and -9 was also investigated. Statistical analysis consisted of ANOVA, Kruskal-Wallis, and linear mixed models with post-hoc pairwise Tukey, Dunn, and t-tests (α = 0.05).

RESULTS

Treatment with SDF resulted in lower weight loss rate than did other solutions, but all groups showed similar Hyp release (p = 0.183). SDF resulted in greater microhardness at superficial layers of the caries lesions (p<0.05), while there were no differences among CNanoF, CNano, and F. Lesion permeability was similar among all groups after pH cycling (p>0.05), with or without the use of collagenase (p = 0.58). No statistically significant difference was noted among solutions regarding collagen integrity after pH cycling; however, SDF-treated dentin had a significant decrease in collagen integrity when collagenase was used (p = 0.003). Interestingly, only SDF was able to completely inactivate MMP-2 and -9.

CONCLUSIONS

CNanoF and SDF both potentially prevent dentin degradation during caries lesion progression in vitro; however, SDF was more effective at inhibiting further tissue demineralization.

Effect of EDTA Gel on Residual Subgingival Calculus and Biofilm: An In Vitro Pilot Study

BACKGROUND

Residual calculus, following scaling and root planing (SRP), is associated with persistent inflammation and the progression of periodontitis. This study examined the effects of a 24% neutral ethylenediaminetetraacetic acid (EDTA) gel on subgingival calculus and biofilms.

METHODS

Eleven single-rooted teeth extracted because of severe periodontal disease were randomly assigned to the following treatment groups: (1) three teeth served as untreated controls; (2) three teeth were treated by scaling and root planing (SRP) only; and (3) three teeth were treated by SRP + EDTA. The remaining two teeth, one SRP only and the other SRP + EDTA were designated for energy-dispersive X-ray spectroscopy (EDS) analysis. EDTA gel was placed on the SRP surface for 2 min and then burnished with a sterile cotton pellet.

RESULTS

SRP + EDTA treated specimens exhibited severely damaged biofilm and the disruption of the extracellular polymeric matrix. EDS scans of the smear layer and calculus featured reductions in the Weight % and Atomic % for N, F, Na, and S and increases in Mg, P, and Ca.

CONCLUSIONS

A 25% neutral EDTA gel was applied after SRP severely disrupted the residual biofilm and altered the character of dental calculus and the smear layer as shown by reductions in the Weight % and Atomic % for N, F, Na, and S and increases in Mg, P, and Ca.

Life history in primate teeth is revealed by changes in major and minor element concentrations measured via field-emission SEM-EDS analysis

Overcoming the non-specificity of histological accentuated growth lines in hard tissues is an ongoing challenge. Identifying season at death and reproductive events has profound implications for evolutionary, ecological and conservation studies. Dental cementum is a mineralized tissue with yearly periodicity that continues deposition from tooth formation until death, maintaining a record spanning almost the entire life of an individual. Recent work has successfully employed elemental analysis of calcified incremental tissues to detect changes in extrinsic conditions such as diet and climate and to identify two important life-history milestones: weaning and sexual maturity. Here, we employ field-emission scanning electron microscopy and energy-dispersive X-ray analysis to measure the relative concentrations of calcium, phosphorous, oxygen, magnesium and sodium in the cementum of 34 teeth from seven male and female rhesus macaques with known medical and life-history information. We find that changes in relative magnesium concentrations correspond with reproductive events in females and breastfeeding in infants. Additionally, we observe seasonal calcium patterns in 77.3% of the samples.

Npp1 prevents external tooth root resorption by regulation of cervical cementum integrity

Tooth roots embedded in the alveolar bone do not typically undergo resorption while the bone continues remodeling in its physiological state. In this study, we analyzed genetically modified mice with the functional inactivation of nucleotide pyrophosphatase 1 (Npp1), encoded by ectonucleotide pyrophosphatase/phosphodiesterase 1 (Enpp1). This mutation leads to the formation of ectopic cervical cementum vulnerable to external tooth root resorption. Cementoblasts with the inactivation of Enpp1 extensively expressed non-collagenous matrix proteins enriched with bone sialoprotein (Bsp), dentin matrix protein 1 (Dmp1), and osteopontin (Opn), which have roles in mineralization through nucleation and in cell adhesion through the Arg-Gly-Asp (RGD) motif. In cementoblasts with the inactivation of Enpp1, β-catenin was significantly activated and induced the expression of these non-collagenous matrix proteins. In addition, adenosine triphosphate (ATP), which is the most preferred substrate of Npp1, accumulated extracellularly and autocrinally induced the expression of the receptor activator of nuclear factor κB ligand (Rankl) in cementoblasts with inactivated Npp1. Consequently, these results strongly suggest that functional Npp1 preserves cervical cementum integrity and supports the anti-resorptive properties of tooth roots through ATP homeostasis in the physiological state of cervical cementum.

Contact ratio and adaptations in the maxillary and mandibular dentoalveolar joints in rats and human clinical analogs

Spatial maps of function-based contact areas and resulting mechanical strains in bones of intact fibrous joints in preclinical small-scale animal models are limited. Functional imaging in situ on intact dentoalveolar fibrous joints (DAJs) in hemimandibles and hemimaxillae harvested from 10 male Sprague-Dawley rats (N = 5 at 12 weeks, N = 5 at 20 weeks) was performed in this study. Physical features including bone volume fraction (BVF), bone pore diameter and pore density, and cementum fraction (CF) of the molars in the maxillary and mandibular joints were evaluated. Biomechanical testing in situ provided estimates of joint stiffness, changes in periodontal ligament spaces (PDL-space) between the molar and bony socket, and thereby localization of contact area in the respective joints. Contact area localization revealed mechanically stressed interradicular and apical regions in the joints. These anatomy-specific contact stresses in maxillary and mandibular joints were correlated with the physical features and resulting strains in interradicular and bony socket compartments. The mandibular joint spaces, in general, were higher than maxillary, and this trend was consistent with age (younger loaded: Mn - 134 ± 55 μm, Mx - 110 ± 47 μm; older loaded: Mn - 122 ± 49 μm, Mx - 105 ± 48 μm). However, a significant decrease (P < 0.05) in mandibular and maxillary joint spaces with age (younger unloaded: Mn - 147 ± 51 μm; Mx - 125 ± 42 μm; older unloaded: Mn - 134 ± 46 μm; Mx - 116 ± 44 μm) was observed. The bone volume fraction (BVF) of mandibular interradicular bone (IR bone) increased significantly with age (P < 0.05) with the percent porosity of coronal mandibular bone lower than its maxillary counterpart. The contact ratio (contact area to total surface area) of maxillary teeth was significantly greater (P < 0.05) than mandibular teeth; both maxillary interradicular and apical contact ratios (IR bone: 41%, 56%; Apical bone: 4%, 12%) increased with age, and were higher than the mandibular (IR bone: 19%, 44%; Apical bone: 1%, 4%) counterpart. Resulting higher but uniform strains in maxillary bone contrasted with lower but higher variance in mandibular strains at a younger age. Anatomy-specific colocalization of physical properties and functional strains in bone provided insights into form-guided adaptive dominance of the maxilla compared to material property-guided adaptive dominance of the mandible. These age-related trends from the preclinical animal model paralleled with age- and tooth position-specific variabilities in mandibular craniofacial bones of adolescent and adult patients following orthodontic treatment.

The early wear susceptibility of cementum, enamel and dentine in vitro

OBJECTIVES

To assess the differential early wear susceptibility of cementum, enamel and dentine at a micron level.

METHODS

Whole human molar buccal surfaces incorporating natural enamel and cementum (n = 20) confirmed by imaging (digital microscopy: Keyence, VHX-7000 Milton Keynes, UK), were mounted, scanned (profilometry: XYRIS 4000, Taicaan, Southampton, UK), and allocated to receive erosion (citric acid, pH 2.7, 30 min (n = 10)) or erosion/abrasion challenges (3 cycles of (citric acid, pH 2.7, 10 min, 60 300 g linear abrasion strokes), n=10). Samples were polished and the experiment repeated on polished enamel, and polished coronal and radicular dentine within the same tooth. Profilometric wear data were obtained using superimposition: GeoMagic (3Dsystems, Darmstadt, Germany) and subtraction: MountainsMap (DigitalSurf, Besancon, France). Data were normal. A general linear model was used to assess differences between groups and substrates.

RESULTS

The mean step height (SD) for natural enamel was 8.82 μm (2.53) for erosion and 11.48 μm (2.95) for erosion/abrasion. For natural cementum, the mean step height was 6.00 μm (2.29) for erosion and 4.67 μm (1.58) for erosion/abrasion. Dentine step heights ranged from 7.20 μm (1.53) for erosion and 9.79 μm (1.01) for erosion/abrasion with no statistical differences in dentine wear. Natural cementum surfaces had the lowest wear (p<0.001). Dentine had significantly less wear than natural enamel (p<0.02).

CONCLUSIONS

Cementum surfaces demonstrated the most wear resistance, followed by dentine under erosion dominant conditions in this in vitro study. Further in-vivo investigations are needed to confirm the intraoral stability of cementum.

CLINICAL SIGNIFICANCE

Cementum may be the least susceptible of dental substrates to wear and dentine does not wear at a faster rate than enamel under erosive conditions. This adds to our knowledge on the development of non-carious cervical lesions and questions whether wear rates will accelerate once dentine is exposed.

Dentoalveolar Defects of Hypophosphatasia are Recapitulated in a Sheep Knock-In Model

Hypophosphatasia (HPP) is the inherited error-of-metabolism caused by mutations in ALPL, reducing the function of tissue-nonspecific alkaline phosphatase (TNAP/TNALP/TNSALP). HPP is characterized by defective skeletal and dental mineralization and is categorized into several clinical subtypes based on age of onset and severity of manifestations, though premature tooth loss from acellular cementum defects is common across most HPP subtypes. Genotype-phenotype associations and mechanisms underlying musculoskeletal, dental, and other defects remain poorly characterized. Murine models that have provided significant insights into HPP pathophysiology also carry limitations including monophyodont dentition, lack of osteonal remodeling of cortical bone, and differing patterns of skeletal growth. To address this, we generated the first gene-edited large-animal model of HPP in sheep via CRISPR/Cas9-mediated knock-in of a missense mutation (c.1077C>G; p.I359M) associated with skeletal and dental manifestations in humans. We hypothesized that this HPP sheep model would recapitulate the human dentoalveolar manifestations of HPP. Compared to wild-type (WT), compound heterozygous (cHet) sheep with one null allele and the other with the targeted mutant allele exhibited the most severe alveolar bone, acellular cementum, and dentin hypomineralization defects. Sheep homozygous for the mutant allele (Hom) showed alveolar bone and hypomineralization effects and trends in dentin and cementum, whereas sheep heterozygous (Het) for the mutation did not exhibit significant effects. Important insights gained include existence of early alveolar bone defects that may contribute to tooth loss in HPP, observation of severe mantle dentin hypomineralization in an HPP animal model, association of cementum hypoplasia with genotype, and correlation of dentoalveolar defects with alkaline phosphatase (ALP) levels. The sheep model of HPP faithfully recapitulated dentoalveolar defects reported in individuals with HPP, providing a new translational model for studies into etiopathology and novel therapies of this disorder, as well as proof-of-principle that genetically engineered large sheep models can replicate human dentoalveolar disorders. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Progress of Research on the Application of Triple Antibiotic Paste and Hydrogel Scaffold Materials in Endodontic Revascularization: A Systematic Review

Objective

To evaluate the application of hydrogel scaffold materials and triple antibiotic paste in endodontic regeneration through literature review.

Methods

An electronic search of the literature published on PubMed, Wangfang database, and CNKI database using the search terms “endodontic regeneration,” “pulp blood flow reconstruction,” “recanalization,” “triple antibiotic paste,” and “scaffold material” was conducted. The searched literature was used for analysis. Results and Conclusion. Hydrogels regulate stem cell fates, modulate growth factor release, and encapsulate antibacterial and anti-inflammatory drugs. The triple antibiotic paste is composed of metronidazole, ciprofloxacin, and minocycline, which exhibits promising antibacterial effects and duration at appropriate concentrations, with low cytotoxicity, and effectively promotes the preservation and regeneration of pulp tissues and the formation of dental hard tissues. However, issues such as tooth discoloration and bacterial drug resistance also exist. The present article reviews the progress of research on the application of hydrogel scaffold materials and triple antibiotic paste in endodontic revascularization.

Development and regeneration of periodontal supporting tissues

Periodontal tissues, including gingiva, cementum, periodontal ligament, and alveolar bone, play important roles in oral health. Under physiological conditions, periodontal tissues surround and support the teeth, maintaining the stability of the teeth and distributing the chewing forces. However, under pathological conditions, with the actions of various pathogenic factors, the periodontal tissues gradually undergo some irreversible changes, that is, gingival recession, periodontal ligament rupture, periodontal pocket formation, alveolar bone resorption, eventually leading to the loosening and even loss of the teeth. Currently, the regenerations of the periodontal tissues are still challenging. Therefore, it is necessary to study the development of the periodontal tissues, the principles and processes of which can be used to develop new strategies for the regeneration of periodontal tissues. This review summarizes the development of periodontal tissues and current strategies for periodontal healing and regeneration.

The prostacyclin analogue iloprost promotes cementum formation and collagen reattachment of replanted molars and upregulates mineralization by human periodontal ligament cells

OBJECTIVES

This study evaluated the use of the prostacyclin analogue, iloprost, as a root surface treatment agent in promoting acellular cementum(AC) formation and collagen reattachment following tooth replantation in vivo. In addition, its effect on human periodontal ligament cell(hPDLC) mineralization was assessed in vitro.

METHODS

First molars of 8-weeks-old Wistar rats were extracted. In one group, the root surfaces were treated with Hank's Balanced Salt Solution(HBSS) and the other group's root surfaces were treated with 10^-6 M iloprost before re-plantation. At day 30, maxillae were prepared for microCT and histomorphometric analysis. The effect of iloprost on mineralization by hPDLCs were analyzed by mineralized nodule formation and qPCR at 7 and 14 days.

RESULTS

MicroCT demonstrated a significant higher bone-volume in the iloprost-groups, whereas the HBSS-groups had extensive bone and root resorption. Histologic analysis revealed deposition of a thick AC layer along the root in iloprost-group with well-organized PDL fibers inserted into the cementum. The HBSS-group demonstrated more osteoclasts than the iloprost-group. In vitro, iloprost-treated hPDLCs had a significantly increased RUNX2, OSX, BSP, and ALP gene expression that coincided with an increased deposition of mineralized nodules. These effects were abrogated by a PGI₂-receptor inhibitor.

CONCLUSION

Our results revealed that iloprost promoted PDL regeneration in replanted molars. Furthermore, resorption of the roots was decreased, whereas AC deposition was stimulated. Iloprost-treatment increased hPDLC mineralization and was mediated by PGI₂-receptor activation. These observations indicate that iloprost may be a promising root surface treatment agent.

Comparative hard x-ray tomography for virtual histology of zebrafish larva, human tooth cementum, and porcine nerve

Purpose: Synchrotron radiation-based tomography yields microanatomical features in human and animal tissues without physical slicing. Recent advances in instrumentation have made laboratory-based phase tomography feasible. We compared the performance of three cutting-edge laboratory systems benchmarked by synchrotron radiation-based tomography for three specimens. As an additional criterion, the user-friendliness of the three microtomography systems was considered. Approach: The three tomography systems-SkyScan 2214 (Bruker-microCT, Kontich, Belgium), Exciscope prototype (Stockholm, Sweden), and Xradia 620 Versa (Zeiss, Oberkochen, Germany)-were given 36 h to measure three medically relevant specimens, namely, zebrafish larva, archaeological human tooth, and porcine nerve. The obtained datasets were registered to the benchmark synchrotron radiation-based tomography from the same specimens and selected ones to the SkyScan 1275 and phoenix nanotom m^® laboratory systems to characterize development over the last decade. Results: Next-generation laboratory-based microtomography almost reached the quality achieved by synchrotron-radiation facilities with respect to spatial and density resolution, as indicated by the visualization of the medically relevant microanatomical features. The SkyScan 2214 system and the Exciscope prototype demonstrated the complementarity of phase information by imaging the eyes of the zebrafish larva. The 3 - μ m thin annual layers in the tooth cementum were identified using Xradia 620 Versa. Conclusions: SkyScan 2214 was the simplest system and was well-suited to visualizing the wealth of anatomical features in the zebrafish larva. Data from the Exciscope prototype with the high photon flux from the liquid metal source showed the spiral nature of the myelin sheaths in the porcine nerve. Xradia 620 Versa, with detector optics as typically installed for synchrotron tomography beamlines, enabled the three-dimensional visualization of the zebrafish larva with comparable quality to the synchrotron data and the annual layers in the tooth cementum.

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.

A Review of In Vivo and Clinical Studies Applying Scaffolds and Cell Sheet Technology for Periodontal Ligament Regeneration

Different approaches to develop engineered scaffolds for periodontal tissues regeneration have been proposed. In this review, innovations in stem cell technology and scaffolds engineering focused primarily on Periodontal Ligament (PDL) regeneration are discussed and analyzed based on results from pre-clinical in vivo studies and clinical trials. Most of those developments include the use of polymeric materials with different patterning and surface nanotopography and printing of complex and sophisticated multiphasic composite scaffolds with different compartments to accomodate for the different periodontal tissues' architecture. Despite the increased effort in producing these scaffolds and their undoubtable efficiency to guide and support tissue regeneration, appropriate source of cells is also needed to provide new tissue formation and various biological and mechanochemical cues from the Extraccellular Matrix (ECM) to provide biophysical stimuli for cell growth and differentiation. Cell sheet engineering is a novel promising technique that allows obtaining cells in a sheet format while preserving ECM components. The right combination of those factors has not been discovered yet and efforts are still needed to ameliorate regenerative outcomes towards the functional organisation of the developed tissues.

Assessing supernumerary roots occurrence as a possible adaptation enhancing teeth performance in Mediterranean deer populations

Teeth root morphology and integrity are essential to provide appropriate attachment, allowing for continuous and functional movement, with implications for adequate food processing, animal performance and longevity. We studied the occurrence of supernumerary roots in mandibular molariform teeth of red deer (Cervus elaphus Linnaeus, 1758) from seven separate populations spanning a range of latitudes in the Iberian Peninsula. We analyzed the influence of several factors, including sex, origin (native vs. reintroduced), lineage and habitat to assess extra root prevalence variations. The highest prevalence of supernumerary roots in deciduous teeth was found in pm3 (14%) and in permanent teeth in M1 (3%). We found significant differences between areas, lineages and soil type; however, no significant relationships were found with the origin, or with the sex of individuals. We speculate that the high prevalence of supernumerary roots in M1 might be related to increased wear in grazers. Furthermore, we suggest that this high prevalence in deciduous teeth might be associated with a hard diet, dry climatic conditions and a harsh weaning period, which suggest supernumerary roots might have adaptive value.

Yttrium Trifluoride as a Marker of Infiltration Rate of Decalcified Root Cementum: An In Vitro Study

Research related to the development of a dental infiltrant for minimally invasive treatment of initial caries of hard dental tissues is presented. The formulation of the developed infiltrant material includes typical methacrylate monomers used in dentistry, an author’s adhesion monomer containing metronidazole, a photoinitiating system and yttrium trifluoride (YF₃). The main objective of the study was to evaluate penetration into decalcified root cementum using scanning electron microscope of an experimental preparation with the characteristics of a dental infiltrant compared to a commercial preparation with the addition of YF₃ as a contrast agent. Microscopic observations showed that YF₃ particles virtually did not penetrate deep into the root cementum—this was mainly due to the particle size of YF₃. Observations of cementum and root dentin tissue infiltration: resin tissue infiltration was visible to a depth of about 80 to 120 μm without the use of a tracer, which, due to agglomeration and particle size, remained on the cementum surface or in the resin used for inlaying. There were no differences between the degree of penetration of an experimental preparation with the characteristics of a dental infiltrant, as compared to a commercial preparation.

Dental cementum virtual histology of Neanderthal teeth from Krapina (Croatia, 130-120 kyr): an informed estimate of age, sex and adult stressors

The evolution of modern human reproductive scheduling is an aspect of our life history that remains vastly uncomprehended. The present work aims to address this gap by validating a non-destructive cutting-edge methodology to infer adult life-history events on modern teeth with known life history and then applying it to fossil specimens. We use phase-contrast synchrotron X-ray microtomography to visualize the dental cementum of 21 specimens: nine contemporary humans; 10 Neanderthals from Krapina (Croatia, 130-120 kyr); one Neolithic Homo sapiens from Ajmana (Serbia); and one Mesolithic H. sapiens from Vlasac (Serbia). We were able to correctly detect and time (root mean square error = 2.1 years; R2 = 0.98) all reproductive (menarche, parturition, menopause) and other physiologically impactful events in the modern sample. Nonetheless, we could not distinguish between the causes of the events detected. For the fossil specimens, we estimated age at death and age at occurrence of biologically significant events. Finally, we performed an exploratory analysis regarding possible sexual dimorphism in dental cementum microstructure, which allowed us to correctly infer the sex of the Neolithic specimen, for which the true value was known via DNA analysis.

Single-Cell Transcriptomic Analysis Reveals Developmental Relationships and Specific Markers of Mouse Periodontium Cellular Subsets

The periodontium is essential for supporting the functionality of the tooth, composed of diversity of mineralized and non-mineralized tissues such as the cementum, the periodontal ligament (PDL) and the alveolar bone. The periodontium is developmentally derived from the dental follicle (DF), a fibrous tissue surrounding the developing tooth bud. We previously showed through in vivo lineage-tracing experiments that DF contains mesenchymal progenitor cells expressing parathyroid hormone-related protein (PTHrP), which give rise to cells forming the periodontal attachment apparatus in a manner regulated by autocrine signaling through the PTH/PTHrP receptor. However, the developmental relationships between PTHrP⁺ DF cells and diverse cell populations constituting the periodontium remain undefined. Here, we performed single-cell RNA-sequencing (scRNA-seq) analyses of cells in the periodontium by integrating the two datasets, i.e. PTHrP-mCherry⁺ DF cells at P6 and 2.3kb Col1a1 promoter-driven GFP⁺ periodontal cells at P25 that include descendants of PTHrP⁺ DF cells, cementoblasts, osteoblasts and periodontal ligament cells. This integrative scRNA-seq analysis revealed heterogeneity of cells of the periodontium and their cell type-specific markers, as well as their relationships with DF cells. Most importantly, our analysis identified a cementoblast-specific metagene that discriminate cementoblasts from alveolar bone osteoblasts, including Pthlh (encoding PTHrP) and Tubb3. RNA velocity analysis indicated that cementoblasts were directly derived from PTHrP⁺ DF cells in the early developmental stage and did not interconvert with other cell types. Further, CellPhoneDB cell-cell communication analysis indicated that PTHrP derived from cementoblasts acts on diversity of cells in the periodontium in an autocrine and paracrine manner. Collectively, our findings provide insights into the lineage hierarchy and intercellular interactions of cells in the periodontium at a single-cell level, aiding to understand cellular and molecular basis of periodontal tissue formation.

Analysis of the nano and microstructures of the cervical cementum and saliva in periodontitis: A pilot study

OBJECTIVES

During the progression of periodontitis, the structures of the cementum and saliva are altered due to pathological changes in the environment. This study aimed to analyze the nanostructures of the cervical cementum and saliva in patients with periodontitis.

METHODS

Patients with periodontitis (n = 10) and periodontally healthy controls (n = 8) were included. Single-rooted teeth with indications for extraction were obtained from individuals. The cervical-thirds of the roots were sectioned transversely to obtain 1 mm thick sections. Unstimulated whole saliva samples were collected from each individual. The nanostructures of the cementum and saliva were analyzed using small and wide-angle X-ray scattering methods.

RESULTS

The mean radius and distance values of the cementum nanoparticles in the periodontitis and control groups were 368 Å and 1152 Å, and 377 Å and 1186 Å, respectively. The mean radius and distance values of the saliva nanoparticles in the periodontitis and control groups were 425 Å and 1359 Å, and 468 Å and 1452 Å, respectively. More wide-angle X-ray scattering profile peaks were observed in the cementum of the controls. Similarities were observed between the 3D profiles of the cementum and the saliva nanoparticles.

CONCLUSIONS

According to the results of the present study, (i) the cementum and saliva nanoparticles were of similar size in periodontitis and healthy controls, (ii) the cementum was more crystalline according to the (002) crystallographic plane in controls, and (iii) the similarities in the 3D-profile of the cementum and saliva nanoparticles suggest some interactions between them in the sulcus/periodontal pocket at the nanolevel.

Role of Cell Death in Cellular Processes During Odontogenesis

The development of a tooth germ in a precise size, shape, and position in the jaw, involves meticulous regulation of cell proliferation and cell death. Apoptosis, as the most common type of programmed cell death during embryonic development, plays a number of key roles during odontogenesis, ranging from the budding of the oral epithelium during tooth initiation, to later tooth germ morphogenesis and removal of enamel knot signaling center. Here, we summarize recent knowledge about the distribution and function of apoptotic cells during odontogenesis in several vertebrate lineages, with a special focus on amniotes (mammals and reptiles). We discuss the regulatory roles that apoptosis plays on various cellular processes during odontogenesis. We also review apoptosis-associated molecular signaling during tooth development, including its relationship with the autophagic pathway. Lastly, we cover apoptotic pathway disruption, and alterations in apoptotic cell distribution in transgenic mouse models. These studies foster a deeper understanding how apoptotic cells affect cellular processes during normal odontogenesis, and how they contribute to dental disorders, which could lead to new avenues of treatment in the future.