Association between dental pulp stones and calcifying nanoparticles

A preliminary study on calcifying nanoparticles in dental plaque: Isolation, characterization, and potential mineralization mechanism

OBJECTIVES

Calcifying nanoparticles (CNPs), referred to as nanobacteria (NB), are recognized to be associated with ectopic calcification. This study aims to isolate and culture CNPs from the dental plaque of patients with periodontal disease and investigate their possible role in unravelling the aetiology of periodontal disease.

MATERIAL AND METHODS

Supragingival and subgingival plaques were sampled from 30 periodontitis patients for CNPs isolation and culture. Alkaline phosphatase (ALP) content changes were tracked over time. Positive samples underwent thorough morphological identification via hematoxylin and eosin (HE) staining, Alizarin red S (ARS), and transmission electron microscopy (TEM). The chemical composition of CNPs analysis involved calcium (Ca) and phosphorus (P) content determination, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD).

RESULTS

The subgingival plaque dental group exhibited a higher CNPs isolation rate at 36.67% (11/30) compared to the supragingival dental plaque group at 66.67% (20/30). ALP activity varied among the positive, negative and control groups. Morphological observation characterized the CNPs as round, oval, and ellipsoid particles with Ca deposits. Chemical analysis revealed the Ca/P ratio was 0.6753. Hydroxyl, methyl, carbonate, phosphate, hydrogen phosphate, and dihydrogen phosphate were detected by FTIR; the main chemical components detected by XRD were hydroxyapatite and tricalcium phosphate.

CONCLUSION

CNPs were found in periodontitis-related dental plaque and exhibited the potential to develop calcified structures resembling dental calculus. However, the potential involvement of ALP in CNPs formation requires deeper exploration, as does the precise nature of its role and the interrelation with periodontitis demand a further comprehensive investigation.

Prevalence of Pulp Stones in the Population of Rajasthan: A Cross-Sectional Study in a Tertiary Care Hospital

Introduction This study aimed to use radiography to determine the prevalence of pulp stones in the population of Rajasthan and to evaluate the relationship between pulp stones and tooth status, type, age, and gender. Methods The radiograph data record files collected from the Department of Dentistry, All India Institute of Medical Sciences, Jodhpur, Rajasthan, from September 2018 to October 2019, had a total of 9918 diagnostic quality intraoral periapical radiographs. One examiner examined all the radiographs to identify pulp stones and associated factors. Pearson chi-square test of significance was used for statistical analysis. Results On screening, a total of 889 intraoral periapical radiographs were found to have pulp stones. The presence of pulp stones was significantly higher in mandibular molars (68%) and was more common in the age group of 31-45 years (37%), followed by 13-29 years (35%). Maximum of pulp stones were of attached type (64%) than free pulp stones. Conclusion The prevalence of pulp stones in the population of Rajasthan studied is 8.9%, which is much lower than the reported prevalence in the literature. Pulp stones are predominantly attached and found significantly more often in mandibular molars in the age group of 31-44 years.

A systematic review assessing the dental pulp stone prevalence in the Saudi Arabian population

This Systematic Review (SR) was to report on the prevalence of pulp stones in the Saudi Arabian (KSA) population. The electronic databases were searched for scientific research articles during May 2021. The data search was performed in electronic search engines like PubMed, Scopus, Web of science, and Saudi Digital Library, and 6 original research articles which fulfilled the eligibility criteria were assessed for qualitative data. The prevalence of pulp stones among the KSA population ranged from 4.6% to 50.93% among the study participants and it ranged between 10.2%-13.34% in the teeth assessed. The pulp stones were more frequently reported in decayed teeth, periodontal diseases, attrition, teeth with dental restorations, and higher in the molar teeth in comparison with the premolar teeth. The data on the prevalence of pulp stones among the Saudi population will be helpful for clinicians in planning endodontic procedures.

Assessment of Pulp Stones Among Western Saudi Populations: A Cross-Sectional Study

BACKGROUND

The term "pulp stones" refers to conditions of calcification that can appear in any area of the dental pulp. This study aims to assess the prevalence of pulp stones and examine whether there is any connection between their occurrence and factors such as patient age, gender, tooth location, presence of decay, or dental restorations in a western Saudi subpopulation based on cone-beam computed tomography (CBCT).

METHODOLOGY

500 patients were randomly selected from the College of Dentistry, Taibah University, Madinah, Saudi Arabia, database. The study involved evaluating 2998 teeth in coronal, axial, and sagittal planes by four dental peer examiners observing and recording data (sequentially and simultaneously) that included whether pulp stones were present or absent, the teeth group (anterior, premolars, and molars), tooth location (maxillary or mandibular), presence or absence of restoration, presence or absence of caries, and the patient's gender. Chi-square tests were utilized for statistical analysis, and a significance level of p-value ≤0.05 was established.

RESULTS

Out of 500 individuals (250 females and 250 males), only 130 individuals (26%) and 278 teeth out of 2998 (9.2%) had pulp stones, with no significant statistical correlation identified between the presence of pulp stones and gender. (P = 0.459). Molars exhibited the greatest incidence of pulp stones (238; 85.6%), followed by anterior teeth (30; 10.8%), and premolars had the lowest prevalence (10; 3.6%). Teeth that showed a higher occurrence of pulp stones were associated with caries (74; 26.6%) and restorations (58; 20.9%). The association between pulpal stone and periodontal involvement was seldom significant (0.7%). A significant association was found between the presence of pulp stones and nonintact teeth (P<0.001). There was a statistically significant difference in the distribution of pulp stones between females and males in the maxillary and mandibular (74.7% and 57.3%, respectively) (P = 0.002). Additionally, the frequency of pulp stones was statistically significant when comparing the left and right sides (P<0.001) (48.9% and 51.1%, respectively).

CONCLUSION

Understanding the prevalence and distribution of pulp stones is crucial for dentists and endodontists, as it assists practitioners in devising an appropriate treatment plan for affected teeth that require root canal therapy. One-fourth of the Madinah population was confirmed to have pulp stones, with a higher incidence in molars, caries, and restored teeth. No difference was found between its occurrence and gender. The high prevalence is exhibited in individuals between 45 and 54 years old. However, further studies with equal patient distribution are needed to confirm this observation.

Effects of Orthodontic Treatment on Pulp Stone Formation: A Retrospective Study

Objective

This retrospective study was aimed at determining the incidence of dental pulp stone formation during fixed orthodontic treatment.

Materials and Methods

A total of 100 patients who received fixed orthodontic treatment were included in this study. Pre- and posttreatment panoramic radiographs of the patients were examined to identify pulp stones. The data were analyzed using McNemar's and Pearson's chi-square tests to investigate the correlations between having a dental pulp stone and gender, age, treatment type, and duration.

Results

Dental pulp stones were detected in 17% of patients on pretreatment panoramic radiographs and 35% of patients on posttreatment panoramic radiographs. The incidence of pulp stones sharply increased in the pre- and posttreatment radiographs (38%) (P < 0.001). In addition, there were associations between age, treatment duration, and the incidence of pulp stones (P < 0.05). Nevertheless, no associations were found between treatment type, gender, and the presence of pulp stones. Dental pulp stones were most frequently observed in first molars (62%), followed by second molars (36%).

Conclusion

Fixed orthodontic treatment may trigger pulp irritation and calcification, resulting in the formation of pulp stones. Although pulp stones have no serious consequences, an orthodontist must consider the probability of pulp stone formation because it can cause difficulties in endodontic treatment.

Association between Periodontitis and Pulp Calcifications: Radiological Study

Objective

The presence of intrapulpal calcifications is one of the effects reported as a consequence of periodontal pathology. Although the impact of the pulp pathology on the periodontium is obvious, the contrary remains unclear and controversial. This study was conducted in order to better understand this fact and establish a potential association between periodontitis and intrapulpal calcifications and then to determine the factors associated with their occurrence.

Materials and Methods

To investigate the issue, a retrospective radiological study using periapical preoperative radiographics assessed 332 teeth taken from the records of 79 patients who received treatment for periodontitis. In the second part of the study, 81 of the sample with intact dental crowns presenting an attachment loss were compared to their contralateral with intact dental crowns without any attachment loss. The study of the association between periodontitis and intrapulpal calcifications and the factors associated with their occurrence was performed by the Chi squared and Fisher's exact tests. The significance level was set at 0.05.

Results

The results indicated that 251 (75.6%) teeth had an attachment loss while 102 (30.7%) had intrapulpal calcification. Among the 206 (62%) teeth with intact crown, only 6 (1.8%) showed calcification in the pulp cavity and 20 (6%) showed calcification in the root canals, with a statistically significant difference (p < 0.005) compared to teeth with restorations and caries. For the 32 (19.7%) teeth with coronary calcification, 18 (22.2%) presented an attachment loss versus 14 (17.2%) without attachment loss; the difference was not statistically significant (p=0.6). Similarly, only 13 (16%) of a total of 22 (13.5%) teeth with root canal calcification had attachment loss versus 9 (11.1%) without attachment loss. This difference was not statistically significant (p=0.5).

Conclusion

This radiographic study revealed no association between the presence of periodontitis and the occurrence of intrapulpal calcifications. Although intrapulpal calcifications were present in some teeth with loss of attachment, they were not necessarily the consequence of periodontal disease.

Insights Into Pulp Biomineralization in Human Teeth

Introduction

Mineralized pulp (MP) compromises tooth function and its causation is unknown. The hypothesis of this study is that pulp mineralization is associated with pulpal tissue adaptation, increased mineral densities, and decreased permeabilities of tubular dentin and cementum. Methods will include correlative spatial mapping of physicochemical and biochemical characteristics of pulp, and contextualize these properties within the dentin-pulp complex (DPC) to reveal the inherent vunerabilities of pulp.

Methods

Specimens (N = 25) were scanned using micro X-ray computed tomography (micro-XCT) to visualize MP and measure mineral density (MD). Elemental spatial maps of MP were acquired using synchrotron X-ray fluorescence microprobe (μXRF) and energy dispersive X-ray spectroscopy (EDX). Extracted pulp tissues were sectioned for immunolabelling and the sections were imaged using a light microscope. Microscale morphologies and nanoscale ultrastructures of MP were imaged using scanning electron (SEM) and scanning transmission electron microscopy (STEM) techniques.

Results

Heterogeneous distribution of MD from 200 to 2,200 mg/cc, and an average MD of 892 (±407) mg/cc were observed. Highly mineralized pulp with increased number of occluded tubules, reduced pore diameter in cementum, and decreased connectivity in lateral channels were observed. H&amp;E, trichrome, and von Kossa staining showed lower cell and collagen densities, and mineralized regions in pulp. The biomolecules osteopontin (OPN), osteocalcin (OCN), osterix (OSX), and bone sialoprotein (BSP) were immunolocalized around PGP 9.5 positive neurovascular bundles in MP. SEM and STEM revealed a wide range of nano/micro particulates in dentin tubules and spherulitic mineral aggregates in the collagen with intrafibrillar mineral surrounding neurovascular bundles. EDX and μXRF showed elevated counts of Ca, P, Mg, and Zn inside pulp and at the dentin-pulp interface (DPI) in the DPC.

Conclusion

Colocalization of physical and chemical, and biomolecular compositions in MP suggest primary and secondary biomineralization pathways in pulp and dentin at a tissue level, and altered fluid dynamics at an organ level. Elevated counts of Zn at the mineralizing front in MP indicated its role in pulp biomineralization. These observations underpin the inherent mechano- and chemo-responsiveness of the neurovascular DPC and help elucidate the clinical subtleties related to pulpitis, dentin-bridge, and pulp stone formation.

Pulp Stones: Diagnostic Significance in Early Diagnosis and Radiographic Correlation with Ischemic Heart Diseases

Context and Aim Sufficient evidence exists in the literature which indicates that patients with ischemic heart diseases (IHDs) show higher degree of pulp calcifications. The present study was, therefore, planned to estimate the prevalence of pulp stones in patients diagnosed with/or undergoing treatment for IHDs. Materials and Methods The present study, which consisted of 300 subjects within the age range of 25 to 65 years, was divided into two groups: study group comprising 150 patients (113 males and 37 females) and 150 age- and sex-matched healthy controls. Pulp stones were imaged using bitewing radiographs and paralleling technique under standard conditions. Statistical Analysis Used Statistical analysis was done using IBM SPSS Statistics for Windows version 21 (IBM Corp, Armonk, USA), while independent t -test and Chi-square test were done to check the prevalence of pulp stones in the study and control groups, based on gender-, arch-, region- and side-wise distribution. p < 0.05 was considered statistically significant. Results The patients with IHDs exhibited 100% prevalence of pulp stones and the difference was found to be statistically significant, although there was a significant difference in the mean number of pulp stones observed in the study and control groups, with the study group revealing 2217 pulp stones as against 639 pulp stones observed in the control group ( p < 0.001). Furthermore, maxillary arch and posterior teeth were predominantly affected in both the groups, although the difference was not found to be statistically significant. Conclusions The findings of the present study suggested a positive correlation between pulp stones and IHDs, highlighting the significance of dental radiographic examination, which may have a possibility for an early detection of IHDs.

Assessing the Prevalence and Association of Pulp Stones with Cardiovascular Diseases and Diabetes Mellitus in the Saudi Arabian Population-A CBCT Based Study

The detection of pulp stone in a patient suffering from undiagnosed systemic diseases can be an early diagnostic indicator. Thus, the aim of the study was to assess the prevalence of pulp stones in the Saudi Arabian population with cardiovascular diseases and diabetes mellitus. In a retrospective study, we included cone-beam computed tomography (CBCT) scans of 73 patients with cardiovascular disease and 76 patients with diabetes mellitus as group I and II, respectively. Group III comprised of CBCT scan of 80 healthy controls. From a total of 229 scans, 4807 teeth were screened for pulp stones throughout the arches. A chi-square test was used for comparing the prevalence of pulp stones among the groups. Univariable and multivariable analysis was done to evaluate the independent risk indicators for pulp stones. The tooth-wise prevalence of pulp stones in group I, II, and III was found to be 16.65%, 9.01%, and 3.86%, respectively. Patient-wise (p < 0.01) and tooth-wise (p < 0.01) prevalence was recorded significantly highest in the cardiovascular group followed by the diabetic group. The control group had the least prevalence. Significantly (p < 0.01) higher number of pulp stones were found in cardiovascular patients with age > 50 years compared to other groups. Similarly, a significantly increased number of pulp stones were seen in the 1st molar (p < 0.05) and the maxillary jaw (p < 0.05) of patients with cardiovascular diseases. Subjects with cardiovascular disease and diabetes were found to have 2.94 times (p < 0.001; CI 1.54-3.10) and 1.81 times (p < 0.01; CI 0.48-2.06) higher risk of having pulp stones in comparison to healthy subjects. The first molar has 2.20 times (p < 0.001; CI 0.84-2.45) increased the risk of having pulp stones compared to other tooth types. Systemic disease such as cardiovascular disease and diabetes mellitus poses a higher risk for the development of pulp stones. Among the systemic disease group, patients in the cardiovascular group showed a higher risk for pulp stones and also reported the maximum number of pulp stones compared to the diabetic and healthy subjects.

Sialometric and Sialochemical Analysis in Individuals With Pulp Stones

The aim of this study was to analyze the saliva of patients with pulp stones, with sialometric and sialochemical tests. Eighty individuals, aged between18 and 65 years, of both sexes, were investigated. Patients were included in the pulp stone group when radiographic examination was suggestive of pulp stones in at least one permanent tooth, whereas those without this alteration were considered controls. Saliva was collected by stimulation, followed by salivary flowrate (SFR) and pH analysis tests. The organic components, such as urea (URE), glucose (GLU), total proteins (TPTs), alkaline phosphatase, creatinine (CRE), salivary amylase (SAM), and uric acid (URA), and the inorganic components, such as calcium, iron, and phosphorus, were evaluated by colorimetric techniques in an ultraviolet–visible (UV–vis) spectrophotometer. Differences among pulp stones and control groups were compared using Student’s t-test, with a significance level of p < 0.05. In both groups prevailed the female. Statistically significant differences between groups were observed for pH (p = 0.027), SFR (p = 0.002), alkaline phosphatase (p = 0.008), and URA (p = 0.005). None of the inorganic components showed significant difference (p > 0.05). In the analyses stratified by sex, difference between groups was observed for pH (p = 0.007) and URA (p = 0.003) in women. In conclusion, sialometric and sialochemical alterations occurred in patients with pulp stones, with significantly higher levels of pH, SFR, alkaline phosphatase, and URA.

Pulp Stones as Risk Predictors for Coronary Artery Disease

Background:

Coronary artery disease (CAD) has been the leading cause of morbidity and mortality worldwide. Studies indicate that patients with CAD show higher degree of pulp calcifications. Localized pulp calcifications are microscopically apparent in more than half of the teeth in young adolescents. However, pulp stones extending to the entire dentition are infrequent and need further evaluation to predict the risk of other probabilities of associated diseases. The present study was planned to estimate the prevalence of pulp stones in patients diagnosed with or, undergoing treatment for CAD.

Methods:

The present study consisted of 300 subjects within an age range of 20-55 years who were divided into the study group consisting of 150 patients including 108 males and 42 females as well as 150 age- and sex-matched healthy controls. Pulp stones were imaged using bitewing radiographs using paralleling technique under standard conditions.

Statistical Analysis Used:

The statistical analysis was performed using IBM SPSS statistics 20 Core system software (SPSS Inc., Chicago, IL, USA) while Chi-square test was used to check the prevalence of pulp stones in patients with CAD in addition to their arch-wise and region-wise distribution. P value <0.05 was considered statistically significant.

Results:

The present study revealed 100% prevalence of pulp stones in the study group while 90% of the subjects in the control group were also afflicted with pulp stones, though the total number of pulp calcifications observed were lesser in number in the control group compared to the study group (P < 0.05). No significant difference was found, although in the gender predilection for the development of pulp stones in the study group while the control group revealed a definite male predilection with around 96.24% of the males afflicted with pulp stones (P < 0.05). Furthermore, maxillary teeth had a statistically significant predilection for the development of pulp stones in both the study as well as the control groups (P < 0.05).

Conclusions:

The patients with CAD have high chance of being affected with pulp stones. Higher prevalence of this entity in multiple teeth may warrant such an individual, in the presence of other compounding risk factors, as a candidate for CAD to be ruled out.

Radiographic Assessment of the Prevalence of Pulp Stones in a Yemeni Population Sample

Objective:

To determine the prevalence and distribution of pulp stones in the posterior teeth of a sample of adult Yemeni dental patients using digital panoramic radiographs.

Methods:

In total, 913 panoramic radiographs from patients attending the hospital dental clinics of at University of Sciences and Technology, Sana’a, Yemen, from January 2013 to December 2014 were examined. The occurrence of pulp stones in the posterior teeth of adult subjects was recorded. Associations between pulp stones and gender, age, arch, side and tooth type were studied.

Results:

The overall prevalence of pulp stones was 18.6% for individuals (170 out of 913 subjects) and 3.99% for examined teeth (351 out of 8802 teeth). The pulp stone occurrence was significantly higher in the maxilla than in the mandible for each tooth type and location (P<0.001). Pulp stones occurred more often on the right side (P<0.001). First molars represented 71% of the affected teeth with the maxillary right first molar showing the highest occurrence. Fifty-six percent of the affected subjects had pulp stones in more than one tooth. No significant difference in the occurrence of pulp stones was detected between genders or among age groups (P>0.05).

Conclusion:

The prevalence of pulp stones is different among populations. Pulp stones were found in approximately one-fifth of subjects in the Yemeni population, where up to 90% of the population have a Qat-chewing habit. This habit usually causes mechanical and chemical irritation and results in pulp calcification.

The relationship between pulp calcifications and salivary gland calcifications

Aim: Pulp stones are discrete calcified bodies found in the dental pulp. Sialolithasis is the most common salivary gland disease. The aim of the present study was to determine the relationship between the pulp stones and salivary gland stones. Material and Methods: 196 patients were randomly selected from the out patient department for the study. The periapical radiographs for all patients were evaluated for the presence or absence of the narrowing of dental pulp chambers and pulp canals. The intra oral occlusal radiographs were also evaluated to determine the presence or absence of salivary stones. The results were compared and analyzed using the Chi-square test (p<0.001). Results: Salivary gland calcifications were detected in 5 patients. 191 patients had pulp narrowing and 118 patients had pulp stones. There was no statistical correlation between pulp narrowing and salivary stones (p>0.001) and also between pulp stones and salivary gland stones (p>0.001). Conclusions: However, the incidental findings of salivary gland stones on intra oral occlusal radiographs can provide useful information in the early diagnosis of the condition, but in the present study no significant relationship was found between the presence of pulp stones and salivary gland stones.

Key words:Pulp stone, salivary gland stone, periapical radiograph, occlusal radiograph.

Incidence and distribution of pulp stones found in radiographic dental examination of adult Turkish dental patients

Background:

Pulp stones (PS) are discrete calcified masses found in the dental pulp, in the pulp tissue or become attached to or embedded into the dentine. The formation of pulp stones is still something of an enigma, leading to existence of some epidemiological gaps.

Aim:

To determine the prevalence and distribution of pulp stones in posterior tooth group by using panoramic radiograph.

Materials and Methods:

Panoramic radiographs from 6912 patients attending Kirikkale University Dental Faculty Hospital, Kirikkale, Turkey during the period from July 2009 to August 2011 were reviewed for the presence of pulp stones. The overall incidence of pulp stones in the patients and their correlations between female and male patients and between the right-side and left-side occurrences were analyzed by computer program, SPSS 15. (SPSS Inc. Chicago, USA) with using the χ² test. Differences were considered as significant when P < 0.05.

Results:

Pulp stones were detected in 879 out of 6912 patients (person prevalence 12.7%). Pulp stones were detected in 2009 teeth out of a total of 96240 teeth to give a tooth prevalence of 2.1%. Their occurrence was higher in the maxilla than in the mandible for each tooth type. Pulp stones were found to involve the right side more (1224/2009) (61%) than the left side (785/2009)(39%) and they were significantly more common in females than males (P < 0.001).

Conclusions:

Attention should be paid to the presence of pulp stones and the treatment problems associated with them.

Clinical implications of calcifying nanoparticles in dental diseases: a critical review

BACKGROUND

Unknown cell-culture contaminants were described by Kajander and Ciftçioğlu in 1998. These contaminants were called nanobacteria initially and later calcifying nanoparticles (CNPs). Their exact nature is unclear and controversial. CNPs have unique and unusual characteristics, which preclude placing them into any established evolutionary branch of life.

AIM

The aim of this systematic review was to assess published data concerning CNPs since 1998 in general and in relation to dental diseases in particular.

MATERIALS AND METHODS

The National Library of Medicine (PubMed) and Society of Photographic Instrumentation Engineers (SPIE) electronic and manual searches were conducted. Nanobacteria and calcifying nanoparticles were used as keywords. The search yielded 135 full-length papers. Further screening of the titles and abstracts that followed the review criteria resulted in 43 papers that met the study aim.

CONCLUSION

The review showed that the existence of nanobacteria is still controversial. Some investigators have described a possible involvement of CNPs in pulpal and salivary gland calcifications, as well as the possible therapeutic use of CNPs in the treatment of cracked and/or eroded teeth.

Idiopathic dental pulp calcifications in a tertiary care setting in South India

Background:

Dental pulp calcifications are unique and represent the dental pulp regenerative process. Dental pulp calcifications are sometimes routine findings in oral radiographs and may later serve as an important diagnostic criterion for a hidden aspect of systemic illness.

Objective:

The purpose of this study was to assess the patterns and prevalence of idiopathic dental pulp calcifications in a tertiary care setting in South India.

Materials and Methods:

A total of 227 patients were included in the study fulfilling the inclusion criteria. Age range of the study population was from 15 to 70 years. Teeth were examined under digital panoramic radiograph. The presence or absence of pulp stones was recorded. The presence of pulp stone were categorized according to the types classified as Type I, Type IA, Type II, Type IIA, Type II B, and Type III. The frequency of occurrence of pulp stones with sex, tooth type, dental arches, and types were compared with the types of calcification.

Results:

Total no. of patients with pulpal calcification were 227 [females 133 (58.59%) and males 94 (41.40%)]. The most common type between both sexes was Type I (48%). Total no. of teeth with calcification was 697; maxilla (48%), mandible (52%). The prevalence of pulp stone was found to be higher in the molars in both the arches. Most no. of pulp stones are reported at the third and fourth decade of life.

Conclusion:

Idiopathic dental pulp calcifications are incidental radiographic findings of the pulp tissue and also may be an indicator of underlying disease.

Association between calcifying nanoparticles and placental calcification

BACKGROUND

The purpose of this study was to examine the possible contribution of calcifying nanoparticles to the pathogenesis of placental calcification.

METHODS

Calcified placental tissues and distal tissue samples were collected from 36 confirmed placental calcification cases. In addition, 20 normal placental tissue samples were obtained as a control group. All the tissue samples were cultured using special nanobacterial culture methods. The cultured calcifying nanoparticles were examined by transmission electron microscopy (TEM), and their growth was monitored by optical density (OD) at a wavelength of 650 nm. 16S rRNA gene expression of the cultured calcifying nanoparticles was also isolated and sequenced.

RESULTS

Novel calcifying nanoparticles wrapped with electron-dense shells between 50 nm to 500 nm in diameter were observed in the extracellular matrix of calcified placental tissues. They were detected in placental villi and hydroxyapatite crystals, and contained "nucleic acid-like materials". After isolation and four weeks of culture, 28 of 36 calcified placental tissue samples showed white granular precipitates attached to the bottom of the culture tubes. OD(650) measurements indicated that the precipitates from the calcified placental tissues were able to grow in culture, whereas no such precipitates from the control tissues were observed. The 16S rRNA genes were isolated from the cultured calcifying nanoparticles and calcified placental tissues, and their gene sequencing results implied that calcifying nanoparticles were novel nanobacteria (GenBank JF823648).

CONCLUSION

Our results suggest that these novel calcifying nanoparticles may play a role in placental calcification.

Evaluation of the interaction between calcifying nanoparticles and human dental pulp cells: a preliminary investigation

Calcifying nanoparticles (CNPs, previously called nanobacteria) are self-propagating, cultivable macromolecular complexes. Their extraordinary characteristic is that they can aggregate carbonate apatite on their envelope from soluble calcium and phosphorus at physiologic concentrations and display cytotoxic effects on murine and human fibroblast cell lines. The question arises whether CNPs contribute to the degeneration of pulp tissue and thus result in clinically significant human dental pulp stones as nidies. This study evaluates CNPs’ effects upon human dental pulp cells (HDPCs, the host cells in pulp tissue). We observed the ultrastructural variation of HDPCs attacked by CNPs. The spatial relationship of HDPCs and CNPs after coculture was also identified by immunofluroscence staining. Furthermore, it was verified by MTT viability assay that CNPs isolated from dental pulp stones exerted cytotoxic effect on HDPCs. Therefore, it could be concluded that the existence of CNPs might interfere with the normal physiologic function of the cells, and that might lead to dental pulp calcification. Elucidation of the cytotoxic characteristics of CNPs may offer a new perspective for understanding the etiology of human dental pulp stones.