Allergic contact dermatitis from dental composite resins due to aromatic epoxy acrylates and aliphatic acrylates

Contact allergies to dental materials in patients

BACKGROUND

Concerns regarding contact allergies and intolerance reactions to dental materials are widespread among patients. Development of novel dental materials and less frequent amalgam use may alter sensitization profiles in patients with possible contact allergy.

OBJECTIVES

To analyse current sensitization patterns to dental materials in patients with suspected contact allergy.

METHODS

This retrospective, multicentre analysis from the Information Network of Departments of Dermatology (IVDK) selected participants from 169 834 people tested in 2005-2019 and registered with (i) an affected area of 'mouth' (and 'lips'/'perioral'), (ii) with the dental material in question belonging to one of three groups (dental filling materials, oral implants or dentures or equivalents) and (iii) with patch-testing done in parallel with the German baseline series, (dental) metal series and dental technician series.

RESULTS

A total of 2730 of 169 834 tested patients met the inclusion criteria. The patients were predominantly women (81.2%) aged ≥ 40 years (92.8%). The sensitization rates with confirmed allergic contact stomatitis in women (n = 444) were highest for metals (nickel 28.6%, palladium 21.4%, amalgam 10.9%), (meth)acrylates [2-hydroxyethyl methacrylate (HEMA) 4.8%] and the substances propolis (6.8%) and 'balsam of Peru' (11.4%). The most relevant acrylates were HEMA, 2-hydroxypropyl methacrylate, methyl methacrylate, ethylene glycol dimethacrylate and pentaerythritol triacrylate. Few men were diagnosed with allergic contact stomatitis (n = 68); sensitization rates in men were highest for propolis (14.9%) and amalgam (13.6%).

CONCLUSIONS

Allergic contact stomatitis to dental materials is rare. Patch testing should not only focus on metals such as nickel, palladium, amalgam and gold, but also (meth)acrylates and the natural substances propolis and 'balsam of Peru'.

Effects of solvent type and UV post-cure time on 3D-printed restorative polymers

OBJECTIVES

This study evaluated the impact of different solvents and UV post-curing times on properties of 3D printing resins for provisional restorations.

METHODS

The post-processing methods were tested using two solvents (isopropyl alcohol or absolute ethanol) and three UV times (5, 10, or 30 min). The resins tested were Resilab 3D Temp, Printax Temp, and Prizma Bioprov. Microhardness (kgf/mm2), fracture toughness (KIC, MPa√m), surface roughness (Ra, µm), gloss (gloss units), and degree of CC conversion (%DC) were measured (n = 8). All response variables were collected from the same specimen. The specimens were 3D printed using an SLA/LCD printer (150° angulation, 50 µm layer thickness). Light exposure times were adjusted for each material, and the post-processing methods were applied using an all-in-one machine immediately after printing. Data were analyzed using Three-Way ANOVA (α = 0.05).

RESULTS

Microhardness was affected by UV post-cure time and 3D resin. Resilab showed higher microhardness with isopropyl alcohol and 30-min UV time, while Printax had higher microhardness with absolute ethanol. KIC was influenced by solvent type, UV time, and 3D resin, with varying effects on different resins. Roughness was affected by 3D resin and UV time, but no significant differences were seen for Resilab or Prizma. Gloss was influenced by 3D resin, and for Prizma, it was lower with specific solvent/UV time combinations. DC was influenced by 3D resin, with each resin behaving differently.

SIGNIFICANCE

Tailoring the combination of 3D resin, solvent washing type, and UV post-curing time is important to achieve optimal mechanical and aesthetic outcomes for restorations.

Biological aspects of modern dental composites

Biological evaluation of resin-based dental composites has traditionally been based on in vitro endpoint tests with different methods to determine loss of cell viability and cell morphology changes after exposure to the material or monomer constituents. The data reveals a potential for biological effects, but clinical relevance of such data is limited. Positive allergy tests and allergic clinical reactions to dental monomers are observed in dental personnel and patients. The aim of this review is to address newer research on molecular events caused by exposure to resin-based composites to have a better understanding of the potential for clinical adverse effects. A more accurate understanding of the biological aspects of dental composite materials has been found after studying parameters like glutathione depletion, oxidative stress, genotoxicity, and immunomodulatory key effects in various cell culture models. Using omics-based approaches allow for a broader and non-specified search of changes caused by methacrylate exposure. Defense mechanisms and adaption are observed in cells exposed to monomer concentrations relevant to clinical exposure. The above-mentioned methods are the foundations for modified testing strategies. The clinical relevance of most available in vitro endpoint tests is of limited relevance for the patient. Research focusing on molecular mechanisms has given new insight into methacrylate toxicity in exposed cells. Using this knowledge from mechanistic studies to develop standardized in vitro biocompatibility tests will likely improve their clinical relevance.

Influence of postwashing process on the elution of residual monomers, degree of conversion, and mechanical properties of a 3D printed crown and bridge materials

OBJECTIVES

This study aimed to determine the effects of the postwashing method and time on the mechanical properties and biocompatibility of three-dimensional (3D) printed crown and bridge resin.

METHODS

DLP (digital light processing)-printed specimens produced from Nextdent crown & bridge (C&B) resins were washed separately using an ultrasonic bath and rotary washer with TPM (tripropylene glycol monomethyl ether) for 3 min, 6 min, 10 min, 20 min, and 1 h. Postcuring was applied for 30 min to each specimen after the washing process. The flexural strength, Vickers hardness, water sorption and solubility, degree of conversion (DC), elution of residual monomers, and biocompatibility of the specimens were evaluated.

RESULTS

The ultrasonic bath showed greater washing efficacy by reducing the residual HEMA (2-hydroxyethyl methacrylate) from 2.0634 ppm to 0.1456 ppm and reducing the residual TEGDMA (triethylene glycol dimethacrylate) from 1.4862 ppm to 0.1484 ppm. With prolonged washing, the flexural strength significantly decreased from 129.67 ± 6.66 MPa (mean±standard deviation) to 103.17 ± 7.20 MPa, while the Vickers hardness increased slightly for the first 6 min and then decreased thereafter significantly. The DC was 87.78 ± 1.34% after 3 min and then gradually decreased with extended washing time. The cytotoxicity significantly decreases with the increment of the washing time.

SIGNIFICANCE

The washing effect on the elution of residual monomers was better for an ultrasonic bath than for a rotary washer. Extending the washing time reduces the mechanical properties and cytotoxicity of the Nextdent C&B resin.

Allergic contact dermatitis from resin-modified glass ionomers

Monomers in a variety of dental materials may cause allergic contact dermatitis. While resin materials have been implicated in the onset of this condition, there is a paucity of evidence linking the condition to the resin-modified glass ionomers (RMGIs). This report documents a rare case of a dentist who developed allergic contact dermatitis following exposure to a RMGI. Contact dermatitis occurred despite the use of latex gloves, which were worn during the procedure. Both the acute and chronic stages of the condition were clinically represented. Patch testing was conducted to confirm the diagnosis. A no-touch technique and the routine use of nitrile gloves were subsequently adopted, which resulted in an overall decrease of the condition. Dentists, auxiliary personnel, and students should be aware of the possibility of sensitization to, and the development of allergic contact dermatitis not only from conventional resin materials, but also from the RMGIs.

Amalgam Contact Allergy in Oral Lichenoid Lesions

BACKGROUND

Oral lichenoid lesions (OLLs) cannot be distinguished from oral lichen planus (OLP) except that causative factors can be identified. Amalgam is one of the causative allergens, and replacement may lead to resolution.

OBJECTIVES

The aim of this study was to determine the prevalence, prognosis, and aggravating factors of amalgam contact allergy in patients with OLLs.

METHODS

A clinical retrospective and prospective cohort study was carried out at the Dermatology Department, Siriraj Hospital, Mahidol University. In cases with patch test positive for an amalgam component, patients were suggested to replace their amalgam restorations.

RESULTS

Of 53 patients with OLLs, 39 (73.6%) had positive patch test results, and 31 (58.5%) reacted to at least one amalgam component. The most common causative allergen was mercury (35.8%). Lesions on bilateral buccal mucosa and gingiva tended to have negative patch test results (P < 0.05). Spicy food was the main aggravating factor. Amalgam replacements were performed in 10 patients. Clinical improvement was observed in all cases with complete healing in 3 cases.

CONCLUSIONS

The prevalence of amalgam contact allergy in patients with OLLs was 58.5%. Mercury was the most common allergen, followed by copper sulfate. An association between clinical, topographic relation, and positive patch test results would be a useful predictor for favorable outcome after amalgam removal.

A systematic study of the release of bisphenol A by orthodontic materials and its biological effects

INTRODUCTION

Bisphenol A (BPA) is a synthetic chemical substance used as a starting ingredient in the manufacturing process of a number or orthodontic materials. It is a well-known endocrine disruptor with low estrogenic properties. The aim of this investigation is to present a systematic review regarding the issue of bisphenol A release by orthodontic materials and its impact in orthodontics.

MATERIALS AND METHODS

A systematic analysis was performed by electronic search (between 1936 and 2015) on several data bases. The search was limited by using several specific key-words in two languages, English and French. Two investigators selected the responses, which met the selection criteria.

RESULTS AND DISCUSSION

Of the 376 studies found, only 21 met our selection criteria: 11 of these dealt with the release of bisphenol by orthodontic materials and 10 in vitro studies described the effects of BPA leaching from orthodontic materials on human and murine cells. The rate of BPA release was well below the daily tolerable intake (DTI) (50mg/kg/day in 2006, then 50μg/kg/day in 2015) according to the European Food Safety Authority (EFSA). Theoretical exposure to BPA was 11,000 times lower than recommendations. However, other studies have shown the presence of BPA and of monomers released in large quantities at very low doses. The effects of observed BPA varied significantly (toxic and carcinogenic potential) while some studies found no effects at all. The relatively small number of studies dealing with the release of Bisphenol A by orthodontic materials, apart from orthodontic materials and their significant biological effects, has led to the absence of standard protocols and has hindered precise determination of released BPA. Moreover, the lack of coherence between the various methodological approaches and variations in the experimental protocols have resulted in a low level of proof regarding the impact of BPA by orthodontic materials.

RECOMMENDATIONS

Through this study, the authors encourage clinicians to observe the following recommendations designed to reduce the amount of BPA released by materials used in orthodontics: keep the tip of the light-curing lamp as close as possible to the composite and perform indirect rather than direct light-curing; Pumice-polish the composite after bonding so as to reduce the potential amount of BPA released; reduce exposure by brushing or rinsing with a mouthwash during the first hour after bonding; follow a standardized, reproducible and expert-validated research protocol aimed at better understanding of BPA release.

Final Report on Ethyl Methacrylate

Ethyl Methacrylate is the ester of ethyl alcohol and methacrylic acid used as the major structural monomer of artificial fingernail formulations that are cross-linked with one or more multifunctional methacrylates. Ethyl methacrylate monomer is polymerized rapidly and very little free monomer is available even during filing of the fingernails. The oral LD50 for rats ranged from 12.7 to 18.14 g/kg, with lesions in the respiratory system and hemoglobinuria observed in treated animals. Ocular, nasal, and respiratory tract irritation was observed in acute inhalation tests using rats. Very little toxicity was seen in subchronic studies using rabbits. Ethyl Methacrylate caused irritation and vehicle dependent sensitization in animals, but no photosensitization. Evidence of embryotoxic and teratogenic effects were observed in pregnant rats after intraperitoneal injection of Ethyl Methacrylate at a range of concentrations. Both positive and negative mutagenicity test data were found. Clinical testing showed little evidence of irritation, although case studies report allergic contact dermatitis as a result of exposure to Ethyl Methacrylate and related methacrylates with application of artificial fingernails. Occupational contact dermatitis from acrylates and methacrylates are also reported, with some evidence for cross-reactivity between the two chemical classes. Based on the sensitizing potential of this ingredient the CIR Expert Panel recommended that fingernail enhancement formulations with Ethyl Methacrylate be applied only by trained individuals and that the ingredient not be used in products intended for retail sale (currently, these products are believed to be sold only for application by a trained individual). Because of the low likelihood of significant exposure if such formulations are applied properly, the Expert Panel concluded that the ingredient is safe as used, with the caveat that skin contact should be avoided.

Final Report on the Safety Assessment of Glutaral

The dialdehyde Glutaral (also commonly called glutaraldehyde) is used in a wide variety of cosmetics as a preservative. In vitro dermal penetration studies of Glutaral indicate low penetration through animal skin and even less through human skin. The oral LD50 of Glutaral for rats ranged from 66 mg/kg up to 733 mg/kg. A 28-day dermal toxicity study of Glutaral produced skin irritation and slight effects on weight and blood chemistry with concentrations as low as 50 mg/kg/day. Animal skin irritation was dose-dependant, with a no-effect concentration of 1%. Ocular exposure to Glutaral caused severe irritation in rabbits at concentrations 1%, with a no-effect level of 0.1%. Glutaral was not embryotoxic, fetotoxic, or teratogenic at concentrations that did not cause severe maternal toxicity. The no observable adverse effects level for reproduction toxicity was > 1,000 ppm. Bacterial mutagenesis tests produced mixed results, as would be expected for a preservative. In most mammalian system mutagenesis tests, Glutaral was not genotoxic. In a 2-year drinking water study in rats, there was an increase in large granular lymphocytic leukemia (LGLL), but only in females administered 50–1,000 ppm Glutaral. The response was not dose dependent. Clinical studies report some evidence of dermal irritation and sensitization, but no photosensitization. Occupational data and animal studies indicate that inhalation of Glutaral can cause respiratory irritation, in addition to skin effects. Evaluation of the increased incidence of LGLL in the 2-year drinking water study indicated that the incidence was within the historical control levels for this spontaneously occurring neoplasm. These data, however, were not considered sufficient to base a finding of safety of Glutaral in products intended for prolonged use. It was concluded that a 2-year dermal carcinogenicity study following National Toxicology Program (NTP) procedures was needed to complete the safety assessment of Glutaral for use in leave-on products. For rinse-off products, it was concluded that the ocular and dermal irritancy of Glutaral could be substantially avoided if the concentration did not exceed 0.5% and exposure was only brief and discontinuous. Because it can cause respiratory irritation, it was concluded that Glutaral should not be used in aerosolized cosmetic products.

Investigation of contact allergy to dental materials by patch testing

BACKGROUND

Dental products are widely used by patients and dental personnel alike and may cause problems for both. Dental materials could cause contact allergy with varying manifestations such as burning, pain, stomatitis, cheilitis, ulcers, lichenoid reactions localized to the oral mucosa in patients, and hand dermatitis in dental personnel. Patch testing with the dental series comprising commonly used materials can be used to detect contact allergies to dental materials.

AIM

This study aimed to identify contact allergy among patients who have oral mucosal lesions after dental treatment and among dental personnel who came in contact with these materials.

MATERIALS AND METHODS

Twenty patients who had undergone dental procedures with symptoms of oral lichen planus, oral stomatitis, burning mouth, and recurrent aphthosis, were included in the study. Dental personnel with history of hand dermatitis were also included in the study. Patch testing was performed using Chemotechnique Dental Series and results interpreted as recommended by the International Contact Dermatitis Research Group (ICDRG).

RESULTS

Out of 13 patients who had undergone dental treatment/with oral symptoms, six patients with stomatitis, lichenoid lesions, and oral ulcers showed positive patch tests to a variety of dental materials, seven patients with ulcers had negative patch tests, seven dental personnel with hand dermatitis showed multiple allergies to various dental materials, and most had multiple positivities.

CONCLUSION

The patch test is a useful, simple, noninvasive method to detect contact allergies among patients and among dental personnel dealing with these products. Long term studies are necessary to establish the relevance of these positive patch tests by eliminating the allergic substances, identifying clinical improvement, and substituting with nonallergenic materials.

Biocompatibility of various dental materials in contemporary dentistry: a narrative insight

In the past few decades, there has been an increase in demand for safety evaluation and control of dental materials used daily in dentistry; however, this task is difficult and cumbersome. Dental materials that are passive and do not react with the oral environment will be more stable and have superior durability. It is expected that dental materials will be universally accepted and will not cause harm or injury to the surrounding structures in the oral cavity. This is an entirely negative approach to the material tolerance and biocompatibility, and hides the possibility that some positive gains can be achieved. Side-effects of dental materials are believed to be rare, and generally, those that have been reported are mild. There are wide varieties of materials used in dentistry, which include liners, irrigants, intracanal filling materials, intracanal medicaments, prosthetic materials, restorative materials, subgingival implants, and mouth rinses. Therefore, in this study, the biocompatibility of various commonly-used clinical materials used in contemporary dentistry was discussed.

Methyl methacrylate and respiratory sensitization: a critical review

Methyl methacrylate (MMA) is a respiratory irritant and dermal sensitizer that has been associated with occupational asthma in a small number of case reports. Those reports have raised concern that it might be a respiratory sensitizer. To better understand that possibility, we reviewed the in silico, in chemico, in vitro, and in vivo toxicology literature, and also epidemiologic and occupational medicine reports related to the respiratory effects of MMA. Numerous in silico and in chemico studies indicate that MMA is unlikely to be a respiratory sensitizer. The few in vitro studies suggest that MMA has generally weak effects. In vivo studies have documented contact skin sensitization, nonspecific cytotoxicity, and weakly positive responses on local lymph node assay; guinea pig and mouse inhalation sensitization tests have not been performed. Cohort and cross-sectional worker studies reported irritation of eyes, nose, and upper respiratory tract associated with short-term peaks exposures, but little evidence for respiratory sensitization or asthma. Nineteen case reports described asthma, laryngitis, or hypersensitivity pneumonitis in MMA-exposed workers; however, exposures were either not well described or involved mixtures containing more reactive respiratory sensitizers and irritants. The weight of evidence, both experimental and observational, argues that MMA is not a respiratory sensitizer.

Identification and quantification of leachable substances from polymer-based orthodontic base-plate materials

The aim of this study was to analyse leachable monomers, additives, and degradation products from polymer-based orthodontic base-plate materials. One heat-cured resin (Orthocryl), one light-cured (Triad VLC), and three thermoplastic materials (Biocryl C, Essix A+, and Essix Embrace) were investigated. Elution was performed in water at 37°C for 10 days. The extract medium was changed and analysed daily. Chromatographic methods were used to identify and quantify the leachables. In addition, the content of residual methyl methacrylate (MMA) was quantified in the poly(methyl methacrylate) (PMMA)-based materials. Statistical analysis of the quantitative results was performed using a t-test for comparison of two independent samples. Monomers and additives leached from the materials polymerized in situ and from the thermoplastic PMMA-based material. No leachable substances were found in the extracts from the other thermoplastic materials. Accumulated over 10 days, a larger amount of MMA leached from the powder-and-liquid material, Orthocryl (42 μg/cm(2)), than from the thermoplastic material, Biocryl C (0.49 μg/cm(2)). The accumulated amounts of monomers leached from Triad VLC were 91 μg/cm(2) of urethane dimethacrylate and 2.2 μg/cm(2) of 2-hydroxyethyl methacrylate. Formaldehyde was found to leach from methacrylate-based materials: 3.2 μg/cm(2) from Orthocryl and 0.16 μg/cm(2) from Triad VLC. However, formaldehyde was not detectable in extracts from Biocryl C. Residual MMA was 5.4 wt % in Orthocryl and 0.4 wt % in Biocryl C. No phthalates were detected in the tested materials. In this in vitro study, minimal leaching was found from the thermoplastic materials, while leaching of methacrylates and formaldehyde was observed from the powder-and-liquid type and the paste material. Within the limitations of this study, the results suggest that prefabricated thermoplastic plates should be preferred for patients with an allergy to methacrylates.

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.

Quantitative analysis of TEGDMA and HEMA eluted into saliva from two dental composites by use of GC/MS and tailor-made internal standards

OBJECTIVES

The use of resin-based dental restorative materials is rapidly increasing, concurrently the biocompatibility of the materials is under investigation. Attention has been placed on studies addressing the cytotoxic, genotoxic and estrogenic potential of these materials. Therefore, the degree of exposure to eluted compounds from the dental materials is of high interest. The aim of this study was to assess the amounts of 2-hydroxyethyl methacrylate (HEMA) and triethyleneglycol dimethacrylate (TEGDMA), released from two composites, eluting into human saliva. To improve the method of quantification, three tailor-made internal standards were synthesized.

METHODS

Specimens made from two composites (Tetric EvoCeram and Filtek Z250) were polymerized and immersed in human saliva for 24h. Eluted TEGDMA and HEMA were identified and quantified. The quantitative analyses were performed by use of combined gas chromatography-mass spectrometry (GC/MS) with tailor-made internal standards synthesized by dissolving HEMA or TEGDMA in methanol and reducing the double bond of the methacrylate group by hydrogenation with 1H2 and 2H2 (D2) gas.

RESULTS

HEMA was released from both materials, whereas TEGDMA eluted from Filtek Z250 only. Full scan GC-MS analysis of each tailor-made internal standard demonstrated one peak only, which was well separated from the corresponding analyte's peak and with no traces of HEMA or TEGDMA.

SIGNIFICANCE

The quantification method seems well suited for in vivo analysis, and the three standards synthesized represent an improved tool for quantification of the eluted monomers. The synthesis may be applied to other methacrylate monomers to produce tailor-made standards for quantification.

Final report of the safety assessment of methacrylate ester monomers used in nail enhancement products

Methacrylate ester monomers are used in as artificial nail builders in nail enhancement products. They undergo rapid polymerization to form a hard material on the nail that is then shaped. While Ethyl Methacrylate is the primary monomer used in nail enhancement products, other methacrylate esters are also used. This safety assessment addresses 22 other methacrylate esters reported by industry to be present in small percentages as artificial nail builders in cosmetic products. They function to speed up polymerization and/or form cross-links. Only Tetrahydrofurfuryl Methacrylate was reported to the FDA to be in current use. The polymerization rates of these methacrylate esters are within the same range as Ethyl Methacrylate. While data are not available on all of these methacrylate esters, the available data demonstrated little acute oral, dermal, or i.p. toxicity. In a 28-day inhalation study on rats, Butyl Methacrylate caused upper airway irritation; the NOAEL was 1801 mg/m3. In a 28-day oral toxicity study on rats, t-Butyl Methacrylate had a NOAEL of 20 mg/kg/day. Beagle dogs dosed with 0.2 to 2.0 g/kg/day of C12 to C18 methacrylate monomers for 13 weeks exhibited effects only in the highest dose group: weight loss, emesis, diarrhea, mucoid feces, or salivation were observed. Butyl Methacrylate (0.1 M) and Isobutyl Methacrylate (0.1 M) are mildly irritating to the rabbit eye. HEMA is corrosive when instilled in the rabbit eye, while PEG-4 Dimethacrylate and Trimethylolpropane Trimethacrylate are minimally irritating to the eye. Dermal irritation caused by methacrylates is documented in guinea pigs and rabbits. In guinea pigs, HEMA, Isopropylidenediphenyl Bisglycidyl Methacrylate, Lauryl Methacrylate, and Trimethylolpropane Trimethacrylate are strong sensitizers; Butyl Methacrylate, Cyclohexyl Methacrylate, Hexyl Methacrylate, and Urethane Methacrylate are moderate sensitizers; Hydroxypropyl Methacrylate is a weak sensitizer; and PEG-4 Dimethacrylate and Triethylene Glycol Dimethacrylate are not sensitizers. Ethylene Glycol Dimethacrylate was not a sensitizer in one guinea pig study, but was a strong sensitizer in another. There is cross-reactivity between various methacrylate esters in some sensitization tests. Inhaled Butyl Methacrylate, HEMA, Hydroxypropyl Methacrylate, and Trimethylolpropane Trimethacrylate can be developmental toxicants at high exposure levels (1000 mg/kg/day). None of the methacrylate ester monomers that were tested were shown to have any endocrine disrupting activity. These methacrylate esters are mostly non-mutagenic in bacterial test systems, but weak mutagenic responses were seen in mammalian cell test systems. Chronic dermal exposure of mice to PEG-4 Dimethacrylate (25 mg, 2 x weekly for 80 weeks) or Trimethylolpropane Trimethacrylate (25 mg, 2 x weekly for 80 weeks) did not result in increased incidence of skin or visceral tumors. The carcinogenicity of Triethylene Glycol Dimethacrylate (5, 25, or 50%) was assessed in a mouse skin painting study (50 microl for 5 days/week for 78 weeks), but was not carcinogenic at any dose level tested. The Expert Panel was concerned about the strong sensitization and crossor co-reactivity potential of the methacrylate esters reviewed in this report. However, data demonstrated the rates of polymerization of these Methacrylates were similar to that of Ethyl Methacrylate and there would be little monomer available exposure to the skin. In consideration of the animal toxicity data, the CIR Expert Panel decided that these methacrylate esters should be restricted to the nail and must not be in contact with the skin. Accordingly, these methacrylate esters are safe as used in nail enhancement products when skin contact is avoided.

The development and course of patch-test reactions to 2-hydroxyethyl methacrylate and ethyleneglycol dimethacrylate

Because Methacrylic monomers are used in dental work, dental personnel, technicians, and patients are at risk of being sensitized. 2-hydroxyethyl methacrylate (2-HEMA) and ethyleneglycol dimethacrylate (EGDMA) are commonly used. Allergic test reactions to them sometimes appear beyond D7. This study was designed to study the development and course of positive test reactions to 2-HEMA and EGDMA in allergic patients as a mean to elucidate the issue of patch-test sensitization. 12 patients with contact allergy to 2-HEMA and EGDMA were retested with dilution series. The clinical course was followed for 1 month. During the study, 25 positive test reactions to 2-HEMA and 19 to EGDMA were diagnosed. Within the 1st week, 21 were noted for 2-HEMA and 18 for EGDMA. After 10 days, another 2 reactions appeared for 2-HEMA and 1 for EGDMA. All but 1 patient with the latter reactions also had positive reactions within the 1st week. After 1 month, 12 reactions for 2-HEMA and 10 for EGDMA remained. Patch-test reactions to 2-HEMA and EGDMA are long-lasting. The patch-test concentrations of 2.0% for 2-HEMA and EGDMA may be continually used. Positive test reactions emerging after 10 days do not automatically imply active sensitization.

Exposure to volatile methacrylates in dental personnel

Dental personnel are exposed to acrylates due to the acrylic resin-based composites and bonding agents used in fillings. It is well known that these compounds can cause contact allergy in dental personnel. However, in the 1990s, reports emerged on asthma also caused by methacrylates. The main volatile acrylates in dentistry are 2-hydroxyethyl methacrylate and methyl methacrylate. The aim of this study was to quantify the exposure to these acrylates in Swedish dental personnel. We studied the exposure to 2-hydroxyethyl methacrylate and methyl methacrylate in five randomly selected public dental clinics and at the Faculty of Odontology at Göteborg University. In total, 21 whole-day and 46 task-specific short-term (1-18 min) measurements were performed. The median 8-hour time-weighted averages were 2.5 microg/m3 (dentists) and 2.9 microg/m3 (dental nurses) for 2-hydroxyethyl methacrylate, and 0.8 microg/m3 (dentists) and 0.3 microg/m3 (dental nurses) for methyl methacrylate. The maximum short-term exposure levels were 79 microg/m3 for 2-hydroxyethyl methacrylate and 15 microg/m3 for methyl methacrylate, similar in dentists and dental nurses. The observed levels are much lower than in complete denture fabrication. We found only one previous study in dentistry and it showed similar results (though it reported short-term measurements only). Irritant effects would not be expected in healthy people at these levels. Nevertheless, occupational respiratory diseases due to methacrylates may occur in dental personnel, and improvements in the handling of these chemicals in dentistry are warranted. This includes better vials for the bonding agents and avoiding evaporation from discarded materials.

The sex of the individual as a factor in allergic contact dermatitis

Exogenous and endogenous factors have been implicated in allergic contact dermatitis (ACD); this review explores the sex of the individual as a possible endogenous factor. While there is a clinical impression that women are more skin-reactive than men, upon review this hypothesis appears oversimplified. This review explores sex differences in controlled testing of adult ACD, occupational ACD and juvenile ACD. Further, geographical location and socioeconomic and cultural factors in relation to sex differences in allergic contact dermatitis are discussed. We conclude that female sex could be a factor predisposing to allergic contact dermatitis not so much because of possible differences in intrinsic skin characteristics between the sexes, but more because of different exposure patterns. This conclusion has practical consequences regarding product labelling requirements, occupational risk assessment and legislation.

Orofacial reaction to methacrylates in dental materials: a clinical report

This clinical report presents an unusual response of acute gingivostomatitis caused by contact sensitivity to the methacrylate compounds present in a dental restorative material.

Synergistic effects of H2O2 with components of dental restorative materials on gluconeogenesis in rat kidney tubules

No data are available about (toxic) effects of dental materials administered in combination with H(2)O(2) from dental bleaching compounds. The effect of dental composite components triethyleneglycoldimethacrylate (TEGDMA) and hydroxyethylmethacrylate (HEMA) as well as mercuric chloride (HgCl(2)) and methylmercury chloride (MeHgCl), each in combination with H(2)O(2), was investigated on gluconeogenesis in kidney cells. From rats kidney tubules were prepared. Every 10 min up to 60 min 1-ml samples were drawn from the cell suspension for quantitating the glucose content. Glucose formation in controls was 3.5+/-0.3 nmol/mg.per min (mean+/-SEM, n=21). Relative rates of glucose formation were obtained by expressing individual rates as percentage of the corresponding control. X-Y concentration curves (effective concentration, EC) of the substances were calculated by fitting a four-parametric sigmoid function to the relative rates of the glucose formation at various test concentrations. At the end of the incubation period cell viability was assessed by trypan blue exclusion. Cell viability decreased within the 60 min interval from 90% to approx. 80% (controls), <25 (HEMA), <20 (TEGDMA), <20 (H(2)O(2)) <10 (MeHgCl), and <10 (HgCl(2)). Values of 50% effective concentration (EC(50)) were calculated from fitted curves. EC(50) values were (mmol/l; mean+/-SEM; n=4): HEMA, 17.2+/-2.8; TEGDMA, 1.9+/-0.2; H(2)O(2) 0.22+/-0.03, MeHgCl, 0.016+/-0.0005; and HgCl(2), 0.0017+/-0.0005. No significant decrease of the EC(50) values was found when kidney cells were exposed to HEMA, HgCl(2), or MeHgCl in addition with H(2)O(2) (1-100 microM), compared to those EC(50) values of each compound without H(2)O(2) addition. A significant decrease of the TEGDMA EC(50) values to about 0.25 or 0.04 (mmol/l) was found when cells were exposed to TEGDMA in combination with H(2)O(2) (75 or 100 microM), compared to that TEGDMA EC(50) value without H(2)O(2) addition. The addition of H(2)O(2) (75 and 100 microM) resulted in a synergistic toxic effect of TEGDMA.

Cytotoxicity of ingredients of various dental materials and related compounds in L2- and A549 cells

Various ingredients of dental materials and related compounds were tested for cytotoxicity in two alveolar epithelial cell lines (L2 and A549 cells). Release of lactate dehydrogenase (LDH) from cells was measured after incubation with the test substances for time intervals up to 48 h and expressed as percentage of total LDH content of lysed cells. Furthermore, the glutathione content of cells was determined in the nonmalignant L2 cells. Additionally, cell viability was assessed by microscopic examination. The highest cytotoxicity was observed with mercury compounds (methylmercuric chloride and mercury dichloride) in the range of 5-20 micromol/l. The composite components 2-hydroxyethylmethacrylate (HEMA) and triethleneglycoldimethacrylate (TEGDMA) showed time- and concentration-dependent effects of cytotoxicity at high concentrations (about 1-5 mmol/l). A time dependence for GSH decrease was mainly found for the composite components up to 12 h of cellular exposure. L2 cells were more sensitive to both mercury and composite compounds than A549 cells. Gold compounds (sodiumaurothiomalate and gold particles < 1.5 microm) did not produce any sign of toxic reactions. A time-dependent increased toxicity in pulmonary cell lines was found for the composite components HEMA and TEGDMA, but not for mercury and gold compounds.

Amended final report on the safety assessment of ethyl methacrylate

Ethyl Methacrylate is a methacrylate ester used as a chemical additive in artificial fingernail enhancement products. These products may be applied by trained professionals or be provided directly to consumers with instructions for use. Ethyl Methacrylate readily polymerizes and rapidly reacts with multifunction methacrylates to form a highly cross-linked polymer. The oral LD(50) of Ethyl Methacrylate for rats ranged from 12.7 to 18.14 g/kg. In acute studies with rats, hemoglobinuria and respiratory tract lesions were observed. Animal studies indicate that Ethyl Methacrylate is a skin irritant and sensitizer. In some cases the results were dependent on the vehicle. Evidence of embryotoxicity and teratogenicity were observed in rats injected intraperitoneally with 0.1223 to 0.4076 ml/kg Ethyl Methacrylate. Positive evidence of mutagenicity was observed in the L5178Y mouse lymphoma cell assay, but not in two Ames tests. Case reports cite examples of individuals suffering allergic contact dermatitis from exposure to Ethyl Methacrylate and related methacrylates, and some degree of cross-reactivity appears to exist between widely used acrylates and methacrylates. Information from several clinical registries of sensitization reactions to various agents reported that Ethyl Methacrylate is a sensitizer, but not a potent one. Because Ethyl Methacrylate monomer is short-lived in the normal course of using artificial fingernail-enhancement products, the primary hazard is expected to be inadvertant skin contact. In order to avoid sensitization, it is necessary to avoid skin contact. It is recommended that fingernail-enhancement products containing Ethyl Methacrylate include directions to avoid skin contact because of the sensitizing potential. Based on the available data on the formulation of nail products containing this ingredient, it is concluded that Ethyl Methacrylate is safe as used, when application is accompanied by directions for use as above.

Cross-reactions of multifunctional methacrylates and acrylates

Dental acrylic monomers (that is, acrylates and methacrylates) are important occupational sensitizers. Acrylic monomers may also cause allergic reactions in dental care. Unfortunately, acrylic monomers cross-react--that is, allergic sensitization induced by one acrylic compound extends to one or more other acrylic compounds. Therefore, sensitized individuals are often multiallergic and, accordingly, cannot be exposed to any of the compounds. In the present review aspects of cross-reactivity in general and data from animal studies of cross-reactivity of multifunctional methacrylates and acrylates are summarized. A multitude of acrylic monomers is used in dentistry, and when patients or dental personnel become sensitized, it is of great importance to identify the dental acrylic preparations to which the sensitized individual can be exposed. Sensitized dental workers are known to have ceased working in dentistry owing to occupational allergic contact dermatitis or asthma, caused by dental acrylic monomers. Unfortunately, cross-reactivity of acrylic monomers used in dentistry is not sufficiently mapped to enable selection of an appropriate compound for the sensitized person. Another important aspect is that product declarations of dental acrylic materials should show all acrylic compounds present in the products--even acrylic monomers/impurities with lower concentrations than 1%. This could help to select a product that the sensitized individual could use.

Occupational dermatitis in dental personnel: contact dermatitis with special reference to (meth)acrylates in 174 patients

Between 1995 and 1998, 174 dental personnel were referred as patients to the Department of Occupational and Environmental Dermatology, Stockholm. After clinical examination, 131 were patch tested with the Swedish standard series and 109 with a dental screening series. Furthermore, 137 were tested for IgE-mediated allergy to natural rubber latex (NRL). Hand eczema was diagnosed in 109/174 (63%), 73 (67%) being classified as irritant contact dermatitis and 36 (33%) as allergic. Further diagnoses included other eczemas, urticaria, rosacea, psoriasis, tinea pedis, bullous pemphigoid or no skin disease. 77/131 (59%) had positive reactions to substances in the standard series and 44/109 (40%) to substances exclusive to the dental series. 24/109 (22%) patients had positive reactions to (meth)acrylates, the majority with reactions to several test preparations. Reactions to HEMA (2-hydroxyethyl methacrylate), EGDMA (ethyleneglycol dimethacrylate) and MMA (methyl methacrylate) were most frequent. 9 of the 24 were positive only to (meth)acrylates, the remaining 15 also had reactions to allergens in the standard series. 23 of these had hand eczema and 1 facial eczema. In 17 of the 24 allergic to (meth)acrylates, the dermatitis had started in 1995 or later, in 15 within the previous 12 months. Of 8 who had been sick-listed, 7 also had a history of atopy and 6 were allergic to nickel. The most frequent allergens besides (meth)acrylates were nickel, cobalt, palladium, fragrance mix, colophonium and thiuram mix. Allergy to natural rubber latex was diagnosed in 14/137 (10%). In conclusion, irritant hand dermatitis was the dominant diagnosis. Contact allergy to (meth)acrylate was seen in 22% of the patch tested patients, with reactions to 3 predominant test substances. 1/3 of the patients with allergy to (meth)acrylates had been sick-listed for dermatitis, but in all these cases the (meth)acrylate allergy was seen together with atopy and/or further contact allergies.

Occupational contact allergy to (meth)acrylates

Among 13,833 patients suspected of contact dermatitis examined during the years 1978-1999, occupational contact allergy to (meth)acrylates was diagnosed in 31 patients. The 3 most common sensitizers were ethyleneglycol dimethacrylate (17 positive patch tests), 2-hydroxyethyl methacrylate (14) and triethyleneglycol dimethacrylate (6). The aim of this report was to assess the different occupations and industries responsible for occupational sensitization to (meth)acrylates. 14 of the 31 patients work in the dental sector, either as a dentist or as a student of dental technology, where (meth)acrylate-containing dental prostheses and dental composites are mainly responsible for allergy to (meth)acrylates. An increasing trend in dermatological problems related to the expansion of the use of (meth)acrylates is clearly reflected in the patient population of our dermatology department.

Biocompatibility of resin-modified filling materials

Increasing numbers of resin-based dental restorations have been placed over the past decade. During this same period, the public interest in the local and especially systemic adverse effects caused by dental materials has increased significantly. It has been found that each resin-based material releases several components into the oral environment. In particular, the comonomer, triethyleneglycol di-methacrylate (TEGDMA), and the 'hydrophilic' monomer, 2-hydroxy-ethyl-methacrylate (HEMA), are leached out from various composite resins and 'adhesive' materials (e.g., resin-modified glass-ionomer cements [GICs] and dentin adhesives) in considerable amounts during the first 24 hours after polymerization. Numerous unbound resin components may leach into saliva during the initial phase after polymerization, and later, due to degradation or erosion of the resinous restoration. Those substances may be systemically distributed and could potentially cause adverse systemic effects in patients. In addition, absorption of organic substances from unpolymerized material, through unprotected skin, due to manual contact may pose a special risk for dental personnel. This is borne out by the increasing numbers of dental nurses, technicians, and dentists who present with allergic reactions to one or more resin components, like HEMA, glutaraldehyde, ethyleneglycol di-methacrylate (EGDMA), and dibenzoyl peroxide (DPO). However, it must be emphasized that, except for conventional composite resins, data reported on the release of substances from resin-based materials are scarce. There is very little reliable information with respect to the biological interactions between resin components and various tissues. Those interactions may be either protective, like absorption to dentin, or detrimental, e.g., inflammatory reactions of soft tissues. Microbial effects have also been observed which may contribute indirectly to caries and irritation of the pulp. Therefore, it is critical, both for our patients and for the profession, that the biological effects of resin-based filling materials be clarified in the near future.

Human and rat mononuclear cell proliferation show different sensitivity, in vitro, to single constituents of dental composite resins

The aim of this study was to evaluate the effect of 11 constituents of dental composite resins on ConA-induced proliferation of rat mononuclear cells. We also wanted to compare the sensitivity of rat and human mononuclear cells, to find out if results from a rat cell assay could be extrapolated to human conditions. The variable used for this purpose was the dose at 50% inhibition of proliferation (ID(50)). Mononuclear cells derived from rat spleens and human venous blood were used. The effects of the substances on rat and human cell proliferation were evaluated with and without stimulation by Concanavalin A. The ID(50) rank order of the tested substance categories was similar for both species, i.e., the monomers inhibited at the lowest concentration, the stabilizer at intermediate, and the initiators at the highest concentrations. In spite of a similar inhibition rank order, there were significant differences in sensitivity to the substances between the species. In conclusion, the results from this study together with the fact that the substances are handled by and used in humans, would favor the use of human cells when studying the effect of constituents of dental composite resins in vitro.

Allergic contact dermatitis in dentistry

Allergic contact dermatitis (ACD) in dentistry may affect dentists and orthodontists, technicians, nurses and patients. Changes to dental practice in recent years have altered the reported frequencies of allergens causing ACD in both dental personnel and patients. Allergic contact dermatitis to medicaments, metals and glutaraldehyde were previously common allergens in dentistry; however, widespread adoption of rubber gloves by staff has resulted in a significant increase in ACD to glove allergens in both dental staff and their patients, while affording protection against the traditional allergens. Both public concerns about potential toxicity of metals in oral restorations and a greater demand for cosmetic dentistry, have resulted in greater use of acrylics and resins by dental personnel, exposing them to highly allergenic materials. Dermatologists need to be aware of the newer allergenic materials used in dentistry in order to correctly manage skin diseases in this high-risk group.