A novel sol-gel-derived calcium silicate cement with short setting time for application in endodontic repair of perforations.

Mineral trioxide aggregate (MTA) is the most frequently used repair material in endodontics, but the long setting time and reduced mechanical strength in acidic environments are major shortcomings. In this study, a novel sol-gel-derived calcium silicate cement (sCSC) was developed using an initial Ca/Si molar ratio of 3, with the most effective mixing orders of reactants and optimal HNO3 catalyst volumes. A Fourier transform infrared spectrometer, scanning electron microscope with energy-dispersive X-ray spectroscopy, and X-ray powder diffractometer were used for material characterization. The setting time, compressive strength, and microhardness of sCSC after hydration in neutral and pH 5 environments were compared with that of MTA. Results showed that sCSC demonstrated porous microstructures with a setting time of ~30 min, and the major components of sCSC were tricalcium silicate, dicalcium silicate, and calcium oxide. The optimal formula of sCSC was sn200, which exhibited significantly higher compressive strength and microhardness than MTA, irrespective of neutral or pH 5 environments. In addition, both sn200 and MTA demonstrated good biocompatibility because cell viability was similar to that of the control. These findings suggest that sn200 merits further clinical study for potential application in endodontic repair of perforations.

Potencial bioativo de cimento à base de silicato de cálcio e ácido poliacrílico em lesões de cárie dentinárias formadas por um modelo de biofilme de microcosmo / Potential bioactive cement based on calcium silicate and polyacrylic acid in dentinal caries lesions formed by a biofilm model of microcosm

O objetivo deste estudo foi avaliar a capacidade de cimentos à base de ácido poliacrílico e silicato de cálcio em aumentar a densidade mineral da dentina desmineralizada por um modelo de biofilme de microcosmo. Além disso, a técnica de dupla energia em micro-CT foi proposta para quantificar a formação de biofilme e a densidade mineral da dentina nas amostras. Quarenta e cinco cavidades em dentina foram preparadas em 9 terceiros molares humanos sadios, sendo 5 em cada dente. As amostras receberam o inóculo bacteriano e foram incubadas em BHI (Brain Heart Infusion) adicionado com 5% de sacarose durante 96h para formação do biofilme. Em seguida, foram realizados dois escaneamentos consecutivos de cada amostra (40kv e 70kv) no micro-CT e cada cavidade foi preenchida com diferentes cimentos experimentais: policarboxilato de zinco (Poly Zinc™), ionômero de vidro convencional (Ketac Molar™) e dois materiais à base de silicato de cálcio (MTA e Biodentine™) enquanto que a cavidade central foi mantida como controle e preenchida com cera utilidade. As amostras foram mantidas durante 45 dias sob simulação da pressão intrapulpar utilizando-se SBF (Simulated Body Fluid) e após o período experimental foram novamente escaneadas. A reconstrução e aquisição foram realizadas utilizando parâmetros padronizados. Os resultados foram testados quanto à normalidade utilizando o teste de Shapiro-Wilk, seguido por métodos não paramétricos. O uso da dupla energia no micro-CT revelou formação de biofilme em todas as cavidades e uma correlação positiva entre o volume da cavidade e o volume do biofilme formado (0,77; p <0,01) foi encontrada. A perda mineral na dentina foi alta (± 90%) para todas as cavidades e mostraram valores de densidade mineral inferior a um limiar definido para a cárie dentinária (1,2g/cm3 ). O aumento da densidade mineral foi maior com MTA ou Poly Zinc™ (43,56% e 41,64%), os quais foram estatisticamente semelhantes, seguido pelo Biodentine™ (36,40%) e Ketac Molar™ (32,54%). Concluiu-se que o modelo de microcosmo bacteriano humano foi capaz de produzir lesões cariosas in vitro e que a técnica de micro-CT por dupla energia provou ser um método eficaz para quantificar a formação de biofilme e a densidade mineral da dentina cariada. Todos os cimentos utilizados apresentaram potencial de aumentar a densidade mineral da dentina desmineralizada, ressaltando o elevado potencial bioativo do cimento policarboxilato de zinco. (AU)

The aim of this study was to evaluate the effect of polyacrylic acid-based and calcium silicates cements in increasing mineral density of demineralized dentin produced by a microcosm model for caries formation. Moreover, a dual energy micro-CT technique was used to quantify biofilm formation and mineral density. Forty-five dentin cavities were prepared in 9 sound human third molars, 5 in each tooth. Samples received the bacterial inoculum and were incubated in BHI (Brain Heart Infusion) added with 5% of sucrose for 96h to allow biofilm formation. After that, two consecutive micro-CT scans were acquired from each specimen (low energy - 40kv and high energy - 70kv) and then, each cavity was filled with different experimental cements, namely: a zinc polycarboxilate (Poly Zinc™), a conventional glass ionomer (Ketac Molar™) and two calcium silicate based materials (MTA and Biodentine™) while the central cavity was kept as control and filled with dental wax. Specimens were kept for 45 days under simulated pulp pressure using SBF (Simulated Body Fluid) and after the experimental period they were again scanned. Reconstruction and acquisition were accomplished using standardized parameters. Data was tested for normality using the Shapiro-Wilk test, followed by non-parametric methods. Dual-energy micro-CT technique disclosed biofilm formation in all cavities and a positive correlation between cavity volume and volume of formed biofilm was obtained (0.77, p<0.01). The mineral decrease obtained in dentin was high (± 90%) for all cavities and all demineralized areas showed mineral density values lower than a defined threshold for dentin caries (1.2g/cm3 ). Increase in mineral density of dentin was best achieved using MTA or Poly Zinc™ (43.56% and 41.64% remineralization), where both were not statistically different. These were followed by Biodentine™ (36.40%) and Ketac Molar™ (32.54%). It is possible to conclude that a microcosm human bacterial biofilm model was able to produce carious lesions in vitro and a dual energy micro-CT technique proved to be an effective method to quantify biofilm formation and mineral density of carious dentin. All cements showed potential to increase mineral density, especially zinc policarboxylate cement.(AU)

[A contractor with damaged knees]. / Een aannemer met kapotte knieën.

A 51-year-old man developed burn wounds on both knees after finishing a cement floor. Cement burns are caused by wet cement, which is highly alkaline Initial treatment consists of lavage. Further management can be conservative but in full thickness injuries excision and grafting should be considered.

Cell markers, cytokines, and immune parameters in cement mason apprentices.

OBJECTIVE: Cement masons are known to have significant silica exposure, and silica exposure and silicosis are thought to increase risk of autoimmune disease. Because the mechanisms remain obscure, with inconclusive reports of systemic immune effects following silica exposure, our goal was to identify potential early markers of silica-related immunologic and respiratory effects. METHODS: We conducted a cross-sectional study of cement mason apprentices and electrician (control) apprentices. Demographics, dust exposure history, symptoms, spirometry, exhaled nitric oxide, and blood (for immunoglobulins, cytokines, cell counts, and surface markers) were obtained from 11 cement mason apprentices and a comparison group of 21 electrician apprentices. RESULTS: Masons had significantly higher (P < 0.05) masonry dust exposure (42 versus 9 dust-hour-years), serum interleukin-1beta (IL-1beta; 12 versus 9 pg/ml), IL-2 (20 versus 8 pg/ml), IL-4 (193 versus 67 pg/ml), IL-10 (44 versus 21 pg/ml), and interferon-gamma (139 versus 65 pg/ml) compared with electricians. In contrast, masons had significantly lower percentages of CD25+ (12% versus 20%) and CD69+ (4% versus 9%) lymphocytes. CONCLUSION: Mason apprentices had higher levels of serum proinflammatory cytokines and lower percentages of CD25+ and CD69+ lymphocytes than did electrician apprentices. These preliminary findings suggest that mason apprentices may be at greater risk of a systemic proinflammatory state that is potentially linked to immune dysregulation. Although distinct limitations of this preliminary data are recognized, this is consistent with early biologic effects leading to increased incidence of autoimmune disease among silica-exposed workers. Prospective studies are needed to validate these initial findings and clarify the temporal sequence of observed relationships.

Cytotoxicity of partial-stabilized cement.

Partial-stabilized cement (PSC) is a kind of modified calcium silicate cement used for root-end surgery. Minor transition metal elements Co, Cr, and Zn were added for enhancing the setting property of to PSC. In our previous study, minor transition metal additions greatly improved the setting property of PSC. However, the concern of metal toxicity was raised, as the material would be used in the human body. In this study, we evaluated the cytotoxicity of PSC in comparison with mineral trioxide aggregate (MTA), which is one of the commercialized materials used for dental root-end filling. Primary osteoblast cell was used as the target cell. Cell proliferation, cytotoxicity, viability, function, and senescence were analyzed. The cytotoxicity of the PSC-Zn group (PSC with Zn addition) was similar to that of MTA. PSC-Zn is not only nontoxic at the cellular level but also has adequate mechanical property, which makes it a potential root-end filling material for apical surgery.

[Cause-specific mortality of asbestos-cement workers compensated for asbestosis in the city of Bari]. / Mortalità per causa specifica dei lavoratori del cemento amianto di Bari titolari di rendita per asbestosi.

The cause-specific mortality of 233 asbestos cement workers employed by the Fibronit company in Bari and compensated for asbestosis was investigated. Cohort members were enrolled on 31.12.1979 and followed through 30.4.1997; follow-up was completed for 98.3% of study subjects, and causes of death were ascertained for 96.6% of deceased subjects. Observed mortality was contrasted to that expected according to cause-sex-age- and calendar time-specific rates of the population resident in the Apulia Region. All causes observed mortality exceeded expected value (SMR: 117, 87 observed), due to a significant' increase in pneumoconiosis (SMR: 11238, 14 observed) and malignant neoplasms (SMR: 163, 38 observed)). A significant decrease of circulatory diseases was found (SMR: 64, 18 observed). Among cancer deaths, the following sites showed a significant excess: lung (SMR: 206, 17 observed), pleura (SMR: 2551, 4 observed), mediastinum (SMR: 2367, 2 observed) and peritoneum (SMR: 2877, 2 observed). The excess mortality due to asbestosis, respiratory cancer and peritoned neoplasms can be causally attributed to occupational asbestos exposure.

[Clinical investigations and cytological examinations of the nose in subject exposed to cement dust]. / Badania kliniczne i cytologiczne nosa u osób eksponowanych na dzialanie pylu cementowego.

Mucous membranes of the nose of 90 persons exposed to cement dust were investigated clinically and cytologically. We found atrophic changes in 37.8% persons and hypertrophic changes in 13.3%. In a halt of the investigated persons abnormality in epithelium forms in cytological examination was demonstrated. The connection of inflammatory changes and pathological forms of the epithelium has been documented. The correlation between presentation of cement deposits and inflammatory infiltrations and atrophic and hypertrophic changes was confirmed.

[Lung cancer mortality in Casale Monferrato (Italy) and attributable risk to occupations in the asbestos-cement production]. / Mortalità per tumore del polmone a Casale Monferrato e rischio attribuibile al lavoro nella produzione del cemento amianto.

The study presents mortality rates for lung cancer in the town of Casale Monferrato, where the largest Italian asbestos cement-plant was located. Cases of lung cancer dying in 1989-94 were exhaustively searched for in the register of deaths. Each case of lung cancer has been identified as ever or never employed in the factory with a linkage to the rosters of employees in the plant. Women were also identified as ever or never married to an asbestos-cement worker. The number of person-years at risk for asbestos cement workers and their wives was measured on the basis of the most recent follow-up. Mortality rates were computed separately for those exposed (workers and wives of workers) and for those with no evidence of exposure. Mortality rates for non-exposed were similar to rates in Piedmont (the region where Casale is located). The relative risk (ever exposed vs. never exposed) was 2.8 among men and 2.1 among women. Attributable risk among the exposed was 64.5% for men and 53.1% for women while among the general population it was 18.1% for men and 13.2% for women. The study confirms the dramatic effect of occupational asbestos exposure in Casale Monferrato but does not suggest an increase in lung cancer mortality among people with no occupational activity in the asbestos-cement production.

Wet cement: a poorly recognized cause of full-thickness skin burns.

Cement is a rare cause of full-thickness burns. We have examined the aetiology, frequency and severity of these burns, and assessed public awareness of the potential of cement as a caustic agent. Of patients, 95 per cent were unaware of the potential of cement to cause burns, and none had seen precautionary warnings on cement bags or delivery dockets. Factors important in burn production appear to be alkalinity, duration of contact and the abrasive nature of the cement particles. It is concluded that doctors, especially casualty officers, should know of the potential of progressive full-thickness burns from wet cement. General public awareness should be increased. The cement manufacturers were asked to comment on the content of this paper.

Mortality and cancer morbidity among cement workers.

OBJECTIVE: To explore associations between exposure to cement dust and cause specific mortality and tumour morbidity, especially gastrointestinal tumours. DESIGN: A retrospective cohort study. SUBJECTS AND SETTING: 2400 men, employed for at least 12 months in two Swedish cement factories. MAIN OUTCOME MEASURES: Cause specific morality from death certificates (1952-86). Cancer morbidity from tumour registry information (1958-86). Standardised mortality rates (SMRs; national reference rates) and standardised morbidity incidence rates (SIRs; regional reference rates) were calculated. RESULTS: An increased risk of colorectal cancer was found > or = 15 years since the start of employment (SIR 1.6, 95% confidence interval (95% CI) 1.1-2.3), mainly due to an increased risk for tumours in the right part of the colon (SIR 2.7, 95% CI 1.4-4.8), but not in the left part (SIR 1.0, 95% CI 0.3-2.5). There was a numerical increase of rectal cancer (SIR 1.5, 95% CI 0.8-2.5). Exposure (duration of blue collar employment)-response relations were found for right sided colon cancer. After > or = 25 years of cement work, the risk was fourfold (SIR 4.3, 95% CI 1.7-8.9). There was no excess of stomach cancer or respiratory cancer. Neither total mortality nor cause specific mortality were significantly increased. CONCLUSIONS: Diverging risk patterns for tumours with different localisations within the large bowel were found in the morbidity study. Long term exposure to cement dust was a risk factor for right sided colon cancer. The mortality study did not show this risk.

Histological type of lung carcinoma in asbestos cement workers and matched controls.

Histological types of lung carcinoma were examined in a case series of workers exposed to asbestos cement dust (n = 29) and matched controls (n = 87). The proportion of adenocarcinomas was 31% among the exposed subjects and 15% among the controls (mid-p = 0.05). Among workers with high exposure the proportion of adenocarcinoma was even higher (45%, 5/11; mid-p = 0.03). The proportion of peripheral tumours tended to be higher among exposed cases than controls (24 v 12%, mid-p = 0.12). Lobe of origin did not differ, however, between exposed cases and controls. Thus the study indicates an association between the degree of exposure to asbestos and adenocarcinoma of the lung, and a peripheral rather than central localisation of the tumours, but with virtually the same distribution of lobe of origin as in the general population.

Dental pulp inflammation; experimental studies in human and monkey teeth.

Data from several studies performed during the last 15 years indicate that bacteria and their products are the main etiological factor for dental pulp inflammation. The present series of investigations was conducted in order to determine the irritating effect from various oral bacterial components and restorative measures on dental pulpal tissue and to ascertain reaction patterns of inflamed pulp tissue. The different bacterial materials were tested in an experimental model where the test substance was applied and enclosed in buccal class V cavities prepared in human or monkey teeth. The pulp tissue response was evaluated from tooth specimens after both short (8 hours) and long time (150 days) challenge with the test substance. Intra and extra cellular components from pure bacterial species, cell wall material and a crude mixture of 8 bacterial species were used as representative test materials for oral bacteria associated with growth on or in dentin. Silicate cement restorations were also used as a pulp irritating restorative procedure. The degree of pulpal inflammation was classified according to a descriptive method. In order to obtain a better evaluation method for pulp tissue reactions, a stereo morphometric technique was developed. This method was used in the last study to evaluate the pulp tissue reactions to silicate cement restorations after dentin treatment with calcium hydroxide. The chemotactic effect of the different bacterial materials were also tested in wound chambers implanted in the back of rats. Results from these studies showed that components from different bacterial species had varying capacity to induce pulpal inflammation over cut dentin. The severity of the early inflammatory response was not altered after decomplementation. The tested bacterial products had a similar chemotactic effect on the pulp tissue as on ordinary connective tissue. If the pulp was challenged with bacterial products for a long time period, healing and repair were frequently found, although if the pulp tissue was primary severely inflamed. The inflammatory reactions and repair patterns in human teeth were similar to those of monkey teeth. Treatment of exposed dentin with calcium hydroxide reduced the pulp irritating effect of silicate cement restorations, but induced only limited volumes of irregular secondary dentin formation.