Erik Christian Munksgaard

Permeability of protective gloves by HEMA and TEGDMA in the presence of solvents

The breakthrough times and permeation rates of two commonly used allergenic components in dentin bonding agents or resins, HEMA and TEGDMA, were measured for 5 types of latex gloves and 5 types of nitrile gloves. In addition, the breakthrough times and permeation rates for the gloves were measured for HEMA and TEGDMA when diluted with either ethanol or acetone-solvents often appearing in dentin bonding agents. The mean breakthrough times for the 5 latex gloves for HEMA and TEGDMA, concentrated, diluted in ethanol, or diluted in acetone, were 4.9, 4.8, and 2.8 min, respectively. For the 5 nitrile gloves the equivalent breakthrough times were 15.7, 9.9, and 2.8 min, respectively. There were great variations between the various gloves, and 1 nitrile glove showed a breakthrough time of 28-30 min when tested with concentrated HEMA and TEGDMA. Compared to latex gloves, nitrile gloves have a longer-lasting protection against skin contamination with methacrylates in the absence of solvents. The longer protection was reduced or not present for methacrylates diluted in organic solvents, especially acetone. In addition, the nitrile gloves showed fairly high permeation rates in the presence of this solvent. The results indicate that latex and nitrile gloves only give a limited protection against allergenic methacrylates in dentin bonding agents when they contain acetone.

Relative gap formation adjacent to ceramic inlays with combinations of resin cements and dentin bonding agents

This study investigated the effect of combining dentin bonding agents (DBAs) with various resin cements on contraction gap formation at the cavity floor of resin-cemented ceramic inlays. Cylindrical dentin cavities were pretreated with one of five DBAs before luting of ceramic inlays with one of four dualcuring resin cements. Measurements of cross sections showed that mean gap widths were reduced from 46% to 93% compared with control specimens prepared without a DBA. The extent of the gap reduction was dependent on the type of bonding agent and resin cement. Although none of the resin cement-dentin bonding agent combinations tested were able to completely eliminate development of interfacial contraction gaps, some combinations produced considerable reductions in gap size.

Wet or dry, normal or deproteinized dentin surfaces as substrate for dentin adhesives

Bond strength between resin composite and dentin mediated by several dentin adhesives applied to dry or wet acid-etched dentin or to dry or wet acid-etched and deproteinized dentin were measured and analyzed. Human dentin were A)acid-etched and blot-dried for 1 sec (= wet), B)as A but dried with air for 10 sec (= dry), C)acid-etched and treated with hypochlorite and then dried for 1 sec, and D)as C but dried with air for 10 sec. Eight dentin adhesives were used in each group for bond strength measurements. The results were compared by means of ANOVA and the Tukey test. Collagen removal increased significantly the strength of the bond by 10-18 MPa for five adhesives when tested dry (D versus A). When tested wet, collagen removal increased the strength by 10-12 MPa for three adhesives (C versus A). Normal etched dentin showed a reduction in strength of 14-15 MPa for three of the adhesives when tested dry instead of wet (B versus A). For one dentin adhesive no significant change in bond strength due to collagen removal and/or drying conditions was observed. It was hypothesized that low technique sensitivity of an adhesive may be linked to its ability to wet and adhere to collapsed collagen fibers and to the surface of the underlying mineralized tissue. Comparisons of bond strengths obtained by using dried or wet acid-etched dentin and dried or wet acid-etched and deproteinized dentin may be useful for evaluating the efficiencies of dentin adhesives.

Changes in expansion and mechanical strength during water storage of a traditional and three modified resin composites.

Four types of resin composites (Dyract AP (DYR), Definite (DEF), Ariston pHc (ARI), and Spectrum TPH (SPE)) were tested after water storage for up to 180 days. The test parameters were flexural strength, flexural modulus, and marginal gaps at fillings in cylindrical cavities. The cavity tests were performed in two ways. One series of fillings was finished shortly after curing and the maximal gaps were followed with time during water storage. Another series was finished immediately before gap size measurement and after water storage for various periods. Absence of or reduced gap sizes at 180 days compared to 1 h or 1 day was observed for all materials and with both methods. At 180 days, DYR and ARI showed significantly smaller gap sizes than those observed with DEF and SPE. No significant differences in flexural strength were observed when means at 180 days were compared to those observed at 1 day. DEF, ARI, and SPE showed a significant increase in flexural moduli at 180 days compared to 1 day, while DYR showed none. It is concluded that fillings made of Dyract AP or Ariston pHc may show absence of or very small gap sizes between filling and cavity wall after 6 months and with no significant reduction in mechanical strength.