Emma-Christin Lönnroth

Cytotoxicity of liquids and powders of chemically different dental materials evaluated using dimethylthiazol diphenyltetrazolium and neutral red tests.

The purpose of this study was to assess and compare the cytotoxicity of liquid and powder components of chemically different dental materials using 2 basic unspecific cell culture methods. Three chemically cured glass ionomers (Fuji II, Lining cement, and Ketac Silver), 1 light-cured glass ionomer (Fuji II LC), and 2 chemically cured acrylates (Swedon and Super Bond) were tested. The liquids were diluted 1:10 in cell culture medium. The liquids from chemically cured acrylates were further diluted 1:100, 1:1000, and 1:10000. Extracts were made by incubating the powders in cell culture medium for 24 h at 37°C according to the ISO standard 10993-12. The cytotoxicity was assessed in transformed mouse fibroblasts (L-929) using two viability assays, dimethylthiazol diphenyltetrazolium (MTT) and neutral red (NR). Severe cytotoxicity was observed when testing powder extracts of Swedon, Fuji II, and Lining cement, whereas powder extracts of Ketac Silver, Fuji LC, and Super Bond induced slight to non-cytotoxicity. All of the 1:10 liquid dilutions were severely cytotoxic in the MTT assay. In the NR assay, however, four 10% dilutions were severely cytotoxic and 4 moderately cytotoxic. Further dilution of the liquids of the chemically cured acrylates reduced the toxicity, while the Super Bond catalyst was severely cytotoxic even as the 1:100 dilutions.

Toxicity of medical glove materials: a pilot study.

Cytotoxicity of 14 glove materials representing 4 natural rubber latex, 6 synthetic rubber and 4 synthetic polymeric materials was evaluated using dimethylthiazol diphenyltetrazolium (MTT), agar overlay and filter diffusion tests. Cell responses after contact with extracts of glove materials and contact with glove materials were assessed. One synthetic rubber glove (nitrile rubber) and 2 synthetic polymeric gloves (polyvinyl chloride) were non-toxic in all 3 tests, while 5 synthetic rubbers exhibited varying degrees of cytotoxicity, depending on the test. A severe cytotoxic response to both extracts of natural rubber latex materials and contact with natural rubber latex was verified in the 3 tests, indicating a need for consideration when selecting gloves, or other products, used in close skin contact.

Cytotoxicity of dental glass ionomers evaluated using dimethylthiazol diphenyltetrazolium and neutral red tests.

The purpose of this study was to assess the cytotoxicity of some commonly used glass ionomers. Three chemically cured glass ionomers (Fuji II, Lining cement, and Ketac Silver) and one light-cured (Fuji II LC) were tested. Extracts of mixed non-polymerized materials and polymerized specimens were prepared in accordance with ISO standard 10993-12. The polymerized specimens were cured and placed either directly in the medium (freshly cured), left for 24 h (aged), or aged plus ground before being placed in the medium. The cytotoxicity of extracts was evaluated on mouse fibroblasts (L 929), using dimethylthiazol diphenyltetrazolium (MTT)and neutral red (NR) assays. Further, the concentrations of aluminum, arsenic and lead were analyzed in aqueous extracts from freshly cured and aged samples, and the fluoride levels analyzed in aqueous extracts from freshly cured samples. All extracts except that of non-polymerized Ketac Silver were rated as severely cytotoxic in both assays. Extracts of polymerized material were significantly more cytotoxic than extracts of non-polymerized material. All freshly cured glass ionomers released aluminum and fluoride concentrations far above what is considered cytotoxic (aluminum >0.2 ppm and fluoride >20 ppm). Extracts from freshly cured Lining Cement contained the highest concentrations of aluminum and fluoride (215 ppm and 112 ppm). Extracts from freshly cured Ketac Silver had the lowest concentrations of aluminum and fluoride but the highest of lead (100 ppm). It can be concluded that all extracts from non-cured, freshly cured, and aged glass ionomers contained cytotoxic levels of substances. Curing did not reduce the toxicity significantly.

Participatory ergonomics intervention in an industrially developing country--a case study.

In industrially developing countries, a few ergonomists have directed great efforts towards developing ergonomics awareness among managers and workers in organizations. There is little research on the degree of their success, though. Furthermore, access of organizations to ergonomics knowledge is usually very difficult, especially in industrially developing countries. Thus, building ergonomics awareness is certainly the first phase of the process. Three companies from one industry (44 people: 14 females and 30 males) participated in a project aimed at improving their work system. At the beginning, we needed to create a common goal and ensure participation with appropriate ergonomics tools. The findings of this study were the key issue for the ergonomics intervention (i.e., a shared vision, awakened need of change and learning). Further, to build ergonomics awareness and develop a continuous learning process in the company, it was necessary to use more ergonomics tools through workers’ participation in different workplaces.

Resistance of Medical Gloves to Permeation by Methyl Methacrylate (MMA), Ethylene Glycol Dimethacrylate (EGDMA), and 1,4-Butanediol Dimethacrylate (1,4-BDMA)

Gloves afford hand protection by minimizing skin contact. The effectiveness of medical gloves to protect against permeation of the monomers, methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDMA), and 1,4-butanediol dimethacrylate (1,4-BDMA), was assessed focusing on permeation rates and degradation of glove materials caused by monomer contact. Fifteen different brands of gloves were tested using a European Standard procedure. Surface images of glove materials before and after exposure to the monomer mixture were obtained using a scanning electron microscope. The standard is not applicable as the only method for estimating the safety of gloves, but it is useful as guideline together with the cumulative permeation of acrylic monomers. Monomer contact on the outside resulted in substantial swelling of most glove materials, and structure changes of the inside surface.

Permeability of medical gloves to mono- and dimethacrylate monomers in dental restorative materials.

Dental personnel manually handle methacrylate-based restorative materials, which can cause skin irritation and allergies. The protection given by different types of medical gloves is not well known. Breakthrough time (BTT, min) was used as a measure of protection according to a European standard, using 2 test mixtures consisting of respectively 3 and 5 monomers. Fourteen gloves representing natural rubber latex, synthetic rubber, and synthetic polymeric material were tested. The BTT ranged from some minutes to more than 2 hrs for the 4 monomers with a molecular mass less than 300. The longest protection was recorded for Nitra Touch (nitrile rubber), Tactylon (synthetic rubber), and Metin (PVC).

Users' demands regarding dental safety glasses. Combining a quantitative approach and grounded theory for the data analysis.

Eye infections are common among dentists and many are concerned, but few are using proper eye protection. To understand users’ demands behind the low use of safety glasses, all dental teams in Sweden were asked which factors they found most important when choosing dental safety glasses, and rate the importance of 31 statements regarding ergonomic aspects of dental safety glasses in a questionnaire. Data were analysed using the Grounded Theory and a quantitative approach. Results showed that dentists ranked the visual aspects as most important and chair assistants the protective aspects. The highly visual demanding work performed by dentists requires safety glasses that are not yet available on the market, which might explain the low use.

Evaluating the Potential Occupational Hazard of Handling Dental Polymer Products Using the HET-CAM Technique

The irritation potencies of 8 dental polymer products, used as dental restorative materials, adhesives, or temporary constructions, were tested using the HET-CAM (hens egg test-chorioallantoic membrane) technique. Liquid and powder components, and extracts of cured and freshly mixed non-cured materials of 5 glass ionomers, 1 bonding, 1 composite, and 1 cold-cured acrylate were examined. Results showed that the liquid component of all products had a strong irritation capacity but powder suspensions and extracts from cured and freshly mixed non-cured materials had no effect on the CAM. Thus, dental personnel who handle liquid and powder manually are exposed to components with a high irritation potential, in contrast to patients who are exposed to the cured and mixed non-cured materials with low irritation potential. This illustrates the importance of safe handling procedures and practices for dental personnel who handle non-cured polymers manually.

The Correlation Between Symptoms, Frequent Use of Dental Polymers, and Evaluation of Health Risk

Dental personnel are at risk as they manually handle polymer products containing monomers and additives that cause irritation and induce allergy. Gloves and face masks can be easily penetrated by monomers. A total of 587 dental personnel and a referent group (585) in the 2 most northern regions of Sweden were included in a questionnaire study (response rate 76%). Questions were asked regarding symptoms of atopy, asthma, conjunctivitis, atopic dermatitis, hand dermatitis, and hay fever/rhinitis. The dental personnel were asked to give the name of polymer products used in their practice and the frequency of use. They were also asked to risk evaluate 5 different types of polymer materials on a scale from 1 to 5. Analysis was done to find if the occurrence of a symptom was associated with a high risk evaluation of a polymer material, or with frequent use of a certain polymer product. Significantly more dentists reported symptoms of atopic dermatitis and conjunctivitis compared to referents and chair assistants. Results show that dental personnel with symptoms risk evaluated most materials significantly higher than dental personnel without symptoms. Further, the occurrence of some symptoms was associated with frequent use of 8 polymer products.

Welcoming the millennium from a decade of growth and development in ergonomics education and promotion

Welcoming the millennium from a decade of growth and development in ergonomics education and promotion