Evaluation of patch test results with denture material series

Influence of Test Specimen Geometry and Water Soaking on the In Vitro Cytotoxicity of Orthocryl®, Orthocryl® LC, Loctite® EA 9483 and Polypropylene

Depending on their composition, plastics have a cytotoxic potential that needs to be evaluated before they are used in dentistry, e.g., as orthodontic removable appliances. Relevant guidelines set out requirements that a potential new resin in the medical field must meet, with a wide scope for experimental design. In the present study, test specimens of different geometries consisting of varying polymers (Orthocryl^®, Orthocryl^® LC, Loctite^® EA 9483, Polypropylene) were soaked for different periods of time, then transferred to cell culture medium for 24 h, which was subsequently used for 24-h cultivation of A549 cells, followed by cytotoxicity assays (WST-1, Annexin V-FITC-propidium iodide (PI) flow cytometry). In this context, a reduction in the cytotoxic effect of the eluates of test specimens prepared from Orthocryl^® LC and Loctite^® EA 9483 was particularly evident in the Annexin V-FITC-PI assay when the soaking time was extended to 48 h and 168 h, respectively. Consistent with this, a reduced release of potentially toxic monomers into the cell culture medium, as measured by gas chromatography-mass spectrometry, was observed when the prior soaking time of test specimens of all geometries was extended. Remarkably, a significant increase in cytotoxic effect was observed in the WST-1 assay, which was accompanied by a higher release of monomers when the thickness of the test sample was increased from 0.5 to 1.0 mm, although an elution volume adapted to the surface area was used. However, further increasing the thickness to 3.0 mm did not lead to an increase in the observed cytotoxicity or monomer release. Test specimens made of polypropylene showed no toxicity under all test specimen sizes and soaking time conditions. Overall, it is recommended to perform toxicity studies of test specimens using different geometries and soaking times. Thereby, the influence of the different specimen thicknesses should also be considered. Finally, an extension of the test protocols proposed in ISO 10993-5:2009 should be considered, e.g., by flow cytometry or monomer analysis as well as fixed soaking times.

Evaluation of dental material series from patients with dental prostheses and suspicion of delayed hypersensitivity

BACKGROUND

Patients with oral sensitivity are common in our practice. Allergic contact dermatitis is one of the most frequent etiologies.

OBJECTIVES

Evaluate oral contact dermatitis using the Brazilian standard series and complementary dental series in patients using dental prostheses, with or without oral complaints. Determine specific dental Brazilian series.

METHODS

Patients using dental prostheses with or without oral complaints realized patch tests. Brazilian standard series and complementary dental series were used according to ICDRG recommendations. The results were analysed according to age, sex, race, atopic conditions and symptoms associated.

RESULTS

From 54 patients tested, 34 (63%) were positive at least to one substance. Nineteen had oral complaints, such as burning mouth, itch or oral erythema. There was no association between atopic condition and tests results. Without the oral series, just 23(42,6%) patients had a positive result. Using the Brazilian standard series with the complementary dental series we improved the positivity of the patch test to 47%.

CONCLUSION

In patients using prostheses and with oral complaints, patch tests with Brazilian standard series with complementary dental series improve the tests positivity.

Methacrylate and acrylate allergy in dental personnel

BACKGROUND

Methacrylates are important allergens in dentistry.

OBJECTIVE

The study aimed to analyse patch test reactivity to 36 acrylic monomers in dental personnel in relation to exposure.

METHODS

We reviewed the test files at the Finnish Institute of Occupational Health from 1994 to 2006 for allergic reactions to acrylic monomers in dental personnel and analysed the clinical records of the sensitized patients.

RESULTS

32 patients had allergic reactions to acrylic monomers: 15 dental nurses, 9 dentists, and 8 dental technicians. The dentists and dental nurses were most commonly exposed to 2-hydroxyethyl methacrylate (2-HEMA), triethyleneglycol dimethacrylate (TREGDMA), and 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]propane (bis-GMA). 8 dentists and 12 dental nurses were allergic to 2-HEMA. The remaining dentist was positive to bis-GMA and other epoxy acrylates. The remaining 3 dental nurses reacted to diethyleneglycol diacrylate (DEGDA) or triethyleneglycol diacrylate (TREGDA), but not to monofunctional and multifunctional methacrylates. Our dental technicians were mainly exposed and sensitized to methyl methacrylate (MMA) and ethyleneglycol dimethacrylate (EGDMA). 1 technician reacted only to 2-HEMA, and another to ethyl methacrylate (EMA) and ethyl acrylate (EA).

CONCLUSIONS

2-HEMA was the most important allergen in dentists and dental nurses, and MMA and EGDMA in dental technicians. Reactions to bis-GMA, DEGDA, TREGDA, EMA and EA were relevant in some patients.

Do adverse effects of dental materials exist? What are the consequences, and how can they be diagnosed and treated?

OBJECTIVES

All dental biomaterials release substances into the oral environment to a varying degree. Various preclinical biocompatibility test systems have been introduced, aiming at an evaluation of the potential risks of dental materials. Potential pathogenic effects of released substances from dental materials have been demonstrated. For the biocompatibility of a biomaterial, it is not only important that minimal diffusable substances are released when it is in body contact--the material must also fulfill the function for which it has been designed. This is also very much dependent on the material properties and its handling properties. The aim of this review was to generate an overview of the present status concerning adverse reactions among patients and personnel.

MATERIALS AND METHODS

A systematic review was performed using a defined search strategy in order to evaluate all MEDLINE-literature published between 1996 and 2006.

RESULTS

The compilation of the literature available has revealed that the majority of studies have been carried out on patients compared with personnel. Adverse reactions towards dental materials do occur, but the prevalence and incidence are difficult to obtain. The results were essentially based on cohort studies. Clinical trials, especially randomized-controlled trials, are in the minority of all studies investigated, with the exception of composite and bonding studies, where clinical trials, but not randomized-controlled trials, represent the majority of studies. Patients and personnel were treated separately in the manuscript. Amalgam studies show the lowest degree of verified material-related diagnosis. Even if objective symptoms related to adverse reactions with polymer resin-based materials have been reported, postoperative sensitivity dominates reports concerning composites/bondings. Verified occupational effects among dental personnel show a low frequency of allergy/toxic reactions. Irritative hand eczema seemed to be more common than in the general population.

CONCLUSIONS

Patient- and personnel-related studies are of variable quality and can be improved. There is a need for a better description of the content of materials. A registry for adverse effects of dental materials would be useful to detect the occurrence of low-incidence events.

[Allergy towards bone cement]

Bone cements based on polymethylmethacrylate are typically used for fixation of artificial joints. Intolerance reactions to endoprostheses not explained by infection or mechanical failure may lead to allergological diagnostics, which mostly focuses on metal allergy. However, also bone cement components may provoke hypersensitivity reactions leading to eczema, implant loosening, or fistula formation. Elicitors of such reactions encompass acrylates and additives such as benzoyl peroxide, N,N-dimethyl-p-toluidine, hydroquinone, or antibiotics (particularly gentamicin). Upon repeated contact with bone cement components, e.g., acrylate monomers, also in medical personnel occasionally hand eczema or even asthma may develop. Therefore, in the case of suspected hypersensitivity reactions to arthroplasty, the allergological diagnostics should include bone cement components.

Quantitative analysis of allergenic ingredients in eluate extracted from used denture base resin

Allergenic ingredients extracted from used denture base resin were quantitatively analysed using a gas chromatograph/mass spectrometer and high performance liquid chromatography. Methyl methacrylate (MMA), hydroquinone (HQ), formaldehyde (FMA), benzoyl peroxide (BPO), benzoic acid (BA) and methyl benzoate (MB) were detected in a eluate from all of the dentures, while ethyleneglycol dimethacrylate (DME) was detected in the eluate from 87 dentures in use for <15 years. MMA, HQ, FMA, BPO and MB showed a decrease in correlation to the period of denture use, but continuing to be evident even after 29 years of use. The MMA showed the highest level of elution and a relatively moderate decrease over time. The elution of BA, on the contrary, showed an increase with the period of denture use up to about 10 years and subsequently reached a plateau. Our results indicate that purported allergens exist in the resin base and can be eluted into the oral cavity, even in patients using an old denture for a period of nearly 30 years.

The resin monomer triethylene glycol dimethacrylate exhibits reproductive toxicity in male mice

The present study evaluated the effect of triethyleneglycol dimethacrylate (TEGDMA) on mouse fertility. Adult male mice were administered TEGDMA (0, 25 and 100 μg kg–1) intragastrically daily for 28 days and then allowed to mate for 10 days with sexually mature untreated female mice; fertility was assessed after a further 10 days. Females mated by males that had been treated with TEGDMA had a significant reduction in pregnancy rate, as well as a significant increase in the total number of resorptions as a percentage of the total number of implantations. Furthermore, the number of animals in which resorption occcurred was increased significantly. Males treated with TEGDMA exhibited a significant reduction in bodyweight, testis weight and the weight of the seminal vesicles and preputial glands. Testicular and epididymal sperm counts, as well as the efficiency of sperm production, were also significantly reduced in TEGDMA-treated males. The results suggest that TEGDMA has adverse effects on the fertility and reproductive system of male mice.

Residual methyl methacrylate monomer, water sorption, and water solubility of hypoallergenic denture base materials

STATEMENT OF PROBLEM

Denture base materials have the potential to cause irritation and allergic reaction to the oral mucosa. Water sorption and water solubility of denture base resins affect dimensional behavior and denture stability. A correlation between residual monomer and water sorption exists.

PURPOSE

This in vitro study compared the amount of residual monomer, quantity of water sorption, and solubility of 4 denture base materials purported to be hypoallergenic with those of a polymethyl methacrylate-based (PMMA) heat-polymerizing acrylic resin.

MATERIAL AND METHODS

The denture base resins Sinomer (heat-polymerized, modified methacrylate), Polyan (thermoplastic, modified methacrylate), Promysan (thermoplastic, enterephthalate-based), and Microbase (microwave polymerized, polyurethane-based), which are purported to be hypoallergenic, and Paladon 65 (heat-polymerized, methacrylate, control group) were examined. Specimens of each material were tested for residual methyl methacrylate (MMA) monomer (% wt, n=3), amount of water sorption (microg/mm3, n=5) and water solubility (microg/mm3, n=5), according to ISO 1567:2000. The residual MMA monomer concentrations were determined by gas chromatography (GC). The data were analyzed with 1-way ANOVA and the Bonferroni-Dunn multiple comparisons post hoc analysis for each test variable (alpha=.05).

RESULTS

Significantly lower residual MMA monomer was shown for Sinomer and Polyan compared to the PMMA control group (0.90 +/- 0.20% wt, P<.05). Sinomer contained 0.31% +/- 0.00% wt MMA monomer, and Polyan exhibited residual MMA monomer content of 0.44% +/- 0.01% wt. Promysan and Microbase did not contain detectable residual MMA. Water sorption of Promysan (16.21 +/- 0.96 microg/mm3) was significantly lower than Paladon 65 (23.04 +/- 3.13 microg/mm3, P<.0001), whereas water solubility of the hypoallergenic denture base materials (0.34-0.84 +/- 0.05-0.09 microg/mm3) was not significantly lower than the PMMA material (0.40 +/- 0.06 microg/mm3, P>.05). Except for Sinomer, the tested denture base resins passed the requirements of ISO 1567 regarding residual MMA monomer (<2.2% wt). Sinomer failed to comply with the requirements for residual MMA monomer because the manufacturer claimed that the material did not contain any MMA. The tested denture base materials fulfilled the requirements regarding water sorption (<32 microg/mm3) and solubility (<1.6 microg/mm3).

CONCLUSION

The tested hypoallergenic denture base materials exhibited significantly lower residual monomer content than PMMA. Promysan and Microbase showed no detectable residual MMA.

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 different types of medical protective gloves to acrylic monomers

Dental personnel and orthopedic surgeons are at risk when manually handling products containing methyl methacrylate (MMA). Dental products may also contain cross-linking agents such as ethylene glycol dimethacrylate (EGDMA) or 1,4-butanediol dimethacrylate (1,4-BDMA). Skin contact with monomers can cause hand eczema, and the protection given by gloves manufactured from different types of material is not well known. The aim of this study was to determine the breakthrough time (BTT, min) as a measure of protection (according to the EU standard EN-374-3) for a mixture consisting of MMA, EGDMA and 1,4-BDMA. Fifteen different gloves representing natural rubber latex material, synthetic rubber material (e.g. nitrile rubbers), and synthetic polymer material were tested. The smallest monomer MMA permeated within 3 min through all glove materials. A polyethylene examination glove provided the longest protection period to EGDMA and 1, 4-BDMA (> 120 min and 25.0 min), followed by the surgical glove Tactylon (6.0 min and 8.7 min) and the nitrile glove Nitra Touch (5.0 min and 8.7 min). This study showed that the breakthrough time (based on permeation rate) cannot be regarded as a 'safe limit'. When the permeation rate is low, monomers may have permeated before BTT can be determined. Using double gloves with a synthetic rubber inner glove and a natural rubber outer glove provided longer protection when the inner glove was rinsed in water before placing the outer glove on top.

Cadmium concentration in maternal and cord blood and infant birth weight: a study on healthy non-smoking women

The aim of our study was to measure, at delivery, maternal and cord blood cadmium levels (by means of atomic absorption spectrometry) in 45 healthy non-smoking pregnant women exposed to a low cadmium challenge, and to evaluate the relationship between these cadmium levels and the birth weight of the infants. Our results showed fairly low cadmium levels in maternal blood, in accordance with the fact that all women enrolled in this study lived in areas with low toxic metal contamination and that they did not smoke during their pregnancy. Furthermore, a highly significant direct correlation was found between maternal and cord blood cadmium concentrations. Since cadmium concentration appeared of the same order of magnitudine both in cord and maternal serum, one could speculate that cadmium is transferred easily from the mother to the fetus through the placenta. Finally, we found that birth weight is inversely correlated with maternal and cord blood cadmium concentrations; thus birth weight might be negatively influenced by cadmium levels as a result of the toxic effects of the metal on the placenta. Although preliminary, our data show that (also not-predictable) prenatal exposure to even low cadmium levels might be a risk factor for developmental impairment in infants.

HEMA bound to self-protein promotes auto-antibody production in mice

While several studies report that acrylic monomers contained in dental materials may cause hypersensitivity reactions, little is known of the associated immune response. Here we address the potential of 2-hydroxyethyl-methacrylate (HEMA) to bind to endogenous protein and elicit auto-antibody production in vivo. Albumin was incubated with HEMA at various times and pH. Following confirmation of the conjugation by inhibition of trinitrophenyl (TNP) binding, female Balb/c mice received HEMA conjugated to mouse serum albumin (MSA) in Freund's incomplete adjuvant or saline subcutaneously. ELISA was used to determine the serum antibody responses to native and modified MSA. IL-2 production in spleen cell cultures stimulated with HEMA-conjugated MSA was measured. HEMA reacted with serum albumin at physiological conditions. HEMA-conjugated MSA induced IL-2 secretion and production of IgG antibodies to native MSA. The results suggest that modification of an endogenous protein like serum albumin with HEMA may defeat the control of immune responses to this self-protein.

Diagnosis and treatment of allergic skin disorders in the elderly

Allergic skin disorders in the elderly may arise from contact with or ingestion of offending allergens. Itching associated with skin allergy must be distinguished from other causes of itching in the elderly such as xerosis, itching due to systemic disease and bullous disease. Although elderly people have somewhat decreased cell-mediated immunity and may be harder to sensitise under experimental conditions, they have had many years to acquire allergic responses, and therefore develop contact dermatitis frequently. Patch testing is a valuable tool to diagnose contact allergy and should be used often in the elderly, particularly in patients at high risk of contact dermatitis, such as those with chronic lower extremity dermatitis or ulcers due to venous stasis. When prescribing topical medications to high risk patients, a knowledge of the common sensitisers is important. In addition to allergy to medicaments and dressings used to treat stasis ulcers, contact allergy to dental prostheses and medications used to treat ocular disease are common in the elderly as a result of increased usage and exposure. Rash caused by ingested allergens is much more commonly due to medications than to food in the elderly. Allergic noneczematous dermatoses in the elderly are commonly drug-induced. Urticarial skin reactions are often associated with the administration of antibacterials, nonsteroidal anti-inflammatory drugs (NSAIDs), antidepressants or opioids. Morbilliform rashes are a common sign of systemic reaction to anticonvulsants, gold, allopurinol or diuretics. Phototoxic reactions may be associated with the administration of tetracyclines, diuretics, NSAIDs and antihyperglycaemic agents. Patient-specific variables such as HLA type and concomitant medication may affect the likelihood of an allergic response to medication. Many elderly patients take multiple medications, which can make diagnosis of drug allergy difficult because diagnosis is most commonly accomplished by observing clinical response once the medication is withdrawn. In the case of lichenoid cutaneous reactions, clinical improvement may take several months after withdrawal of the offending drug. Laboratory tests to detect drug-induced allergic skin disorders may be available in the future.

Allergic contact stomatitis caused by acrylic monomer in a denture

A 71-year-old edentulous man developed a severely painful red mouth at sites of contact with a new denture. Patch testing showed allergy to samples of the denture material and to 2-hydroxyethyl methacrylate. Patch testing to methyl methacrylate was negative. Prolonged boiling of the denture resulted in reversal of his symptoms and samples of this fully cured denture material produced negative patch tests. While allergy to acrylates is a rare cause of stomatitis, this possibility must be considered in patients presenting with oral symptoms. Material safety data sheets are unreliable in providing information regarding the type of acrylate present in the material. Hence, patch testing should be performed with a battery of acrylate allergens as well as with small samples of the denture material.

Contact dermatitis in Korean dental technicians

The high risk of occupational contact dermatitis in dental personnel are well accepted throughout the world. There are few reports concerning occupational skin disease in dental personnel in Korea. The purposes of this study were to investigate the frequency, characteristics and causative factors of contact dermatitis in Korean dental technicians. Recording of personal history, physical examination and patch tests with the Korean standard series and dental screening series were performed in 49 dental technicians. Most of the subjects were exposed to a variety of compounds, including acrylics, metals, plaster, alginate, etc. 22 (44.9%) subjects had contact dermatitis, present or past, and the site involved was the hand in all 22. The most common clinical feature of hand dermatitis was itching (77.3%); scaling, fissuring and erythema were other common clinical features. Metals, including potassium dichromate (24.5%), nickel sulfate (18.4%), mercury ammonium chloride (16.3%), cobalt chloride (12.2%) and palladium chloride (10.2%), showed high positive rates in patch test results of 49 dental technicians. 7 positive reactions to the various acrylics were found in 3 subjects. In our study, the frequency and clinical features of the contact dermatitis showed a similarity to other reports, though the patch test results were somewhat different; a higher patch-positive reaction to metals and a relatively lower patch-positive reaction to acrylics than the patch test results reported in Europe.

Contact and irritant stomatitis

Contact stomatitis is rather uncommon because of the relative resistance of the oral mucosa to irritant agents and allergens. The clinical manifestations of contact stomatitis are extremely variable and include erythema, erosions, ulcerations, leukoplakia-like lesions, and lichenoid reactions. Clinical signs are frequently less pronounced than subjective symptoms, and patients commonly experience severe functional problems despite only mild mucosal alterations. Allergic stomatitis is rare and almost always attributable to metallic mercury and gold salts. A careful history and an accurate examination of the oral cavity, teeth, and dental restorations are essential for a correct diagnosis. Patch testing is indicated in all lesions that are not clearly related to trauma or physical injuries. Patch testing is not useful in the burning mouth syndrome. Evaluation of clinical relevance of patch test results is always very difficult and requires an interdisciplinary approach to the patient. Successful treatment requires the identification and elimination of the causative factor, when possible. It is important to bear in mind that replacement of dental restorations and prostheses may be very expensive and stressful for the patient and thus should not be recommended when their causative role is doubtful.