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

Influence of bonding agent application method on the dentin bond durability of a two-step adhesive utilizing a universal-adhesive-derived primer

This study investigated the effect of the bonding agent application method on the dentin bond durability of a two-step adhesive utilizing a universal-adhesive-derived primer. The bonding durability of a universal adhesive was compared with those of two conventional two-step adhesives by shear bond strength testing after thermal cycling. The primer was applied (with or without phosphoric acid pre-etching), and the specimens were divided into three groups based on the bonding agent application method used as follows: (i) strong air-flow application, (ii) gentle air-flow application, and (iii) gentle air-flow + second bonding application. The shear bond strength was determined after thermal cycling. All the factors (bonding agent application method, adhesive system, and storage condition) significantly influenced the dentin shear bond strength both with and without phosphoric acid pre-etching. The specimens exposed to gentle air-flow showed a higher shear bond strength than did those exposed to strong air-flow and gentle air-flow + second bonding. The bond durability of the tested adhesive systems was influenced by the bonding agent application method, and this trend was material dependent. The G2-Bond Universal exhibited the same or greater dentin bond durability to the other two-step adhesive systems.

Sublingual administration of 2-hydroxyethyl methacrylate enhances antibody responses to co-administered ovalbumin and Streptococcus mutans

OBJECTIVE

The oral mucosa of patients undergoing dental procedures is often exposed to residual monomers leaking from incompletely cured acrylic resins. We investigated whether 2-hydroxyethyl methacrylate (HEMA) monomers applied to the sublingual mucosa in mice modulate the antibody responses towards co-administered ovalbumin (OVA) or live oral bacteria.

MATERIAL AND METHODS

OVA, live mouse oral commensal Lactobacillus murinus or live human oral commensal Streptococcus mutans were administered sublingually with or without HEMA to BALB/c mice on four weekly occasions. One week after the last administration, the experiment was terminated and serum antibody levels were analyzed using ELISA.

RESULTS

Significantly increased IgG and IgE anti-OVA antibody activity was found in the sera from mice immunized with OVA together with HEMA, as compared to mice immunized with OVA alone. Likewise, S. mutans together with HEMA induced an IgG anti-S. mutans antibody response that was significantly higher than the antibody response detected after application of S. mutans alone. No IgG anti-L. murinus antibody response was detected in mice immunized with L. murinus together with HEMA, as compared to the background activity.

CONCLUSIONS

We report that HEMA monomers have adjuvant properties when sublingually administered in combination with OVA or S. mutans.

Resin Monomer 2-Hydroxyethyl Methacrylate (HEMA) is a Potent Inducer of Apoptotic Cell Death in Human and Mouse Cells

Mechanisms by which the resin monomer 2-hydroxyethyl methacrylate (HEMA) induces hypersensitivity reactions in humans are not well-established, nor have the direct effects of HEMA on cell death been fully characterized. The objective of this study was to establish whether HEMA is capable of inducing apoptotic cell death, and whether differences exist in the levels of apoptotic death induced by HEMA in cells obtained from healthy individuals and from patients with established HEMA hypersensitivity. HEMA induced apoptotic death in Peripheral Blood Mononuclear Cells (PBMCs) obtained from both healthy and HEMA-sensitized patients and in the murine RAW cells in a dose-dependent manner. However, induction of cell death by HEMA was lower in PBMCs obtained from patients in comparison with healthy individuals. Studies reported in this paper demonstrate that HEMA induces apoptotic death, and that decreased susceptibility of lymphocytes to HEMA-mediated death might be an important mechanism for the generation and persistence of hypersensitivity reactions in patients.

Effect of Phosphoric Acid Pre-etching on Fatigue Limits of Self-etching Adhesives

The purpose of this study was to use shear bond strength (SBS) and shear fatigue limit (SFL) testing to determine the effect of phosphoric acid pre-etching of enamel and dentin prior to application of self-etch adhesives for bonding resin composite to these substrates. Three self-etch adhesives—1) G- ænial Bond (GC Corporation, Tokyo, Japan); 2) OptiBond XTR (Kerr Corp, Orange, CA, USA); and 3) Scotchbond Universal (3M ESPE Dental Products, St Paul, MN, USA)—were used to bond Z100 Restorative resin composite to enamel and dentin surfaces. A stainless-steel metal ring with an inner diameter of 2.4 mm was used to bond the resin composite to flat-ground (4000 grit) tooth surfaces for determination of both SBS and SFL. Fifteen specimens each were used to determine initial SBS to human enamel/dentin, with and without pre-etching with a 35% phosphoric acid (Ultra-Etch, Ultradent Products Inc, South Jordan, UT, USA) for 15 seconds prior to the application of the adhesives. A staircase method of fatigue testing (25 specimens for each test) was then used to determine the SFL of resin composite bonded to enamel/dentin using a frequency of 10 Hz for 50,000 cycles or until failure occurred. A two-way analysis of variance and Tukey post hoc test were used for analysis of SBS data, and a modified t-test with Bonferroni correction was used for the SFL data. Scanning electron microscopy was used to examine the area of the bonded restorative/tooth interface. For all three adhesive systems, phosphoric acid pre-etching of enamel demonstrated significantly higher (p<0.05) SBS and SFL with pre-etching than it did without pre-etching. The SBS and SFL of dentin bonds decreased with phosphoric acid pre-etching. The SBS and SFL of bonds using phosphoric acid prior to application of self-etching adhesives clearly demonstrated different tendencies between enamel and dentin. The effect of using phosphoric acid, prior to the application of the self-etching adhesives, on SBS and SFL was dependent on the adhesive material and tooth substrate and should be carefully considered in clinical situations.

Five-year clinical performance of a HEMA-free one-step self-etch adhesive in noncarious cervical lesions

OBJECTIVES

The objective of this randomized controlled trial was to evaluate the clinical performance of a 2-hydroxyethyl methacrylate (HEMA)-free one-step adhesive.

MATERIALS AND METHODS

Two hundred sixty-seven cervical lesions in 52 patients were restored with the composite Gradia Direct (GC), bonded with either the one-step self-etch adhesive G-Bond (GC) or the three-step etch-and-rinse adhesive Optibond FL (Kerr) in a random order. The restorations were evaluated for retention, marginal integrity, marginal discoloration, and caries occurrence after 5 years. Specific statistics were used to account for the clustered data (multiple restorations per patient).

RESULTS

The clinical success rate for G-Bond (87.4 %) was not significantly different from that of Optibond FL (90.9 %). Both adhesives showed progressive marginal deterioration, but G-Bond exhibited more small enamel defects and marginal discoloration, and unlike previous recalls, several restorations failed because of deep microleakage. Large sclerotic lesions were a significant risk factor for retention loss with G-Bond. Irrespective of the adhesive, almost all restorations with retention loss were located in the lower jaw.

CONCLUSION

After 5 years of clinical service, restorations bonded with the HEMA-free one-step adhesive did not need repair or replacement more often than those with the three-step etch-and-rinse adhesive, and both adhesives had a high retention rate (>90 %). There were indications that G-Bond did not (self-)etch enough in some clinical situations, as G-Bond exhibited more incisal defects and marginal discolorations, and sclerotic lesions were at higher risk of retention loss.

CLINICAL RELEVANCE

The clinical performance of the HEMA-free one-step adhesive was clinically acceptable after 5 years.

HEMA enhances IgG1 production by human B-cells in vitro

We have previously shown that the resin monomer 2-hydroxyethylmethacrylate (HEMA) affects mouse B-lymphocyte activity, leading to increased IgG1 antibody production in vivo. In the present study, we tested, in vitro, the hypothesis that HEMA also affects human B-lymphocyte activity. The in vitro production of IgG1, IgM, and IgA in supernatants from purified human CD19+ B-lymphocyte cultures, containing different concentrations of HEMA, was assayed with ELISA. Proliferation was measured by [methyl-(3)H] thymidine incorporation. Of the different HEMA concentrations used, the lower concentrations caused a significant increase in IgG1 production, but not in IgM or IgA production, in vitro. The lower HEMA concentrations did not significantly change B-cell proliferation. At the highest concentration, HEMA significantly suppressed IgG1 and IgM production, as well as B-cell proliferation, in vitro. In conclusion, HEMA can, at certain concentrations, selectively enhance human B-lymphocyte IgG1 production.

ABBREVIATIONS

2-hydroxyethylmethacrylate (HEMA), Dulbecco's Modified Eagle's Medium supplemented with heat-inactivated fetal bovine serum, gentamycin, penicillin, and streptomycin (D-MEM++++), Enzyme-linked Immuno-sorbent Assay (ELISA), phosphate-buffered saline (PBS), ovalbumin (OVA), pokeweed mitogen (PWM), counts per minute (CPM).

Application of HEMA on intact mouse skin - effects on the immune system

Previously, we have shown that 2-hydroxyethylmethacrylate (HEMA) can bind to protein and that autoantibodies were induced in mice by immunization with a self-protein in vitro conjugated with HEMA. The present study aimed to develop a model for HEMA-induced sensitivity by the application of the substance on intact skin. Female BALB/c mice were painted on the dorsum of each ear with 50% HEMA in vehicle twice a week for 6 weeks. The anti-CD3epsilon-stimulated lymph node production and the spontaneous spleen-cell production of the cytokines interleukin (IL)-2, IL-4, IL-6, IL-10 and interferon-gamma were assessed by enzyme-linked immunosorbent assay. In another experiment, the cytokines were followed after subcutaneous HEMA injections. Animals painted with HEMA had a significantly higher IL-6 production by anti-CD3epsilon-stimulated lymph node cells and significantly suppressed IL-10 production by spleen cells compared to vehicle-treated mice. This correlated to some extent with the spontaneous spleen-cell production induced by subcutaneously administered HEMA. An injection of 20 micromol of HEMA induced an increased production of IL-6, while injection of 40 micromol depressed both IL-6 and IL-10 production. Although there was no sign of inflammation on the ears, findings suggest that HEMA had penetrated the skin and induced a reaction in the immune system.

Inflammatogenic and adjuvant properties of HEMA in mice

2-Hydroxyethylmethacrylate (HEMA), a common constituent in dental materials, is known to cause hypersensitivity reactions. While the means by which this small molecule causes adverse responses has not been ascertained, we have previously demonstrated that it binds to protein and in mice induces the production of autoantibodies to HEMA-conjugated self-protein. The present study explores the inflammatory and adjuvant properties of HEMA in response to the subcutaneous injection of HEMA and a protein. Ovalbumin (OVA) was used as a 'reporter antigen', and mouse serum albumin (MSA), conjugated in vitro with HEMA (MSA(H)) to a low degree (0.5 molecules of HEMA per molecule of MSA on average), was used to mimic a possible in vivo situation. Inflammatory responses at injection sites were scored by using an ordinal scale, and immunoglobulin (Ig)G1, IgG2a, and IgE activities to OVA or MSA were assessed by enzyme-linked immunosorbent assay (ELISA). Injections of 20 micromol HEMA induced overt inflammatory skin responses, the severity of which was influenced by the co-administered substances. A significantly higher IgG1 and IgE response to OVA was induced by the presence of HEMA. Interestingly, injections with low conjugated MSA(H) only induced the production of autoantibodies if free HEMA was included at the time of immunization. These findings suggest that HEMA is an inflammatogenic substance with adjuvant properties.

Low HEMA conjugation induces high autoantibody titer in mice

2-hydroxyethylmethacrylate (HEMA) is a known causal agent of hypersensitivity to resin composites. We have reported that immunization with HEMA conjugated to mouse serum albumin (MSA) induces an autoantibody response in mice. In this study, we investigated both the activity and the avidity of autoantibodies induced by immunization with various HEMA conjugations to MSA. Female Balb/c mice were given MSA carrying 3, 7, 15, or 22 HEMA molecules. Antigen-specific IgG and IgE antibodies were determined by ELISA, and average antibody avidity by thiocyanate dissociation. Immunization with MSA carrying the lowest number of HEMA molecules induced a significantly higher IgG and IgE anti-MSA autoantibody response, with significantly higher IgG antibody avidity, than did the more heavily conjugated preparations. The results suggest that the lower the degree of HEMA conjugation to self-protein, the higher the risk for autoantibody production to the carrier protein. These findings suggest a mechanism of potential relevance in humans.

Immunological Consequences of Methamphetamine Protein Glycation

The drug of abuse methamphetamine has been found to participate in the aberrant glycation of proteins. The importance of this chemical process has been shown wherein mouse albumin was readily modified with methamphetamine, and injection of this protein into mice yields a significant immune response, even in the absence of adjuvants. Competition experiments revealed that although methamphetamine binds weakly to the elicited antibodies, the primary epitope is composed of both the methamphetamine moiety and glucose-derived cross-linking region. Implications of this phenonomenon in the context of drug addiction are discussed.

Future directions in bonding resins to the dentine-pulp complex

Resin-based materials are rapidly becoming the primary restorative material to replace tooth structure and the low percentage of biological problems reported for resin-based restorations is testimony to their relative biocompatibility. Despite considerable advances in the understanding of the mechanisms, which govern the integration of resin composite materials with the dentine-pulp complex, considerable potential for improvement remains. Most of these improvements centre around a better understanding of the biological and microbiological risks of resin materials and will only be possible with improved in vitro and in vivo models. There are also a number of possible future developments in materials, clinical techniques and diagnostic methods that may improve the long-term success and reliability of resin-based restorations. The remainder of this paper describes the most likely avenues for future improvements.