The color change resulting from storage in water was measured on a number of experimental and proprietary complex resins. The experimental resins contained varying amounts of amine (DEPT or DEBA), benzoyl-peroxide (BPO) and inhibitor (MHQ). The proprietary resins had earlier been analyzed as regards the composition of the monomer and the content of amine and peroxide. The color change of DEPT-containing resins was positively correlated with the DEPT/BPO ratio, and negatively correlated with the monomer content of BISGMA. DEBA-containing resins were more color stable than resins containing equimolar concentrations of DEPT. The color change was independent of MHQ up to a certain concentration; above this the color change increased with the amount of MHQ. In general, the light activated materials were more color stable than the chemically activated materials. The color change was not affected by pH, but decreased when the oxygen had been removed from the storage water. The test for color stability using UV-light irradiation gave results for proprietary resins that were not correlated with the results obtained by water storage.

A method is described, by which retrograde root filling with a composite resin can be performed. The cavity design is a slightly concave dissection of the apical part of the root, which is treated with the bonding agent Gluma followed by an application of Retroplast. Retroplast is a chemically curable composite containing silver for radiopacity and aerosil to obtain a suitable consistency. Endodontically treated teeth with a eugenol-containing root canal sealer did not affect the strength of the bond between Retroplast and apical dentin. A tight seal between the composite and the cavity surface was observed by light and SEM microscopy, and histology of tissue surrounding fillings placed in monkeys revealed absence of inflammatory cells around the filling and a close contact between filling and fibroblasts with collagenous fibers. In some cases, cementum and Sharpey's fibers formed in contact with the filling. Fillings placed in humans performed successfully in most cases, and the main causes of failure were either inadequate hemostasis during filling, or root fracture unnoticed by the time of filling. The retrograde technique promises a new treatment principle, with a root canal effectively sealed and the periapical ligament restored after apicoectomy.

The accuracy (fit) of MOD inlays of three brands of composite resin was determined by measuring the axial discrepancy (marginal opening in the approximal area). The axial discrepancy varied between 17 and 121 microns. Directly manufactured inlays were more accurate (axial discrepancy: 17-26 microns) than indirectly manufactured inlays (axial discrepancy: 40-121 microns). Inlays of a microfilled resin, SR-Isosit, were less accurate than inlays of two hybrid materials, Brilliant and Estilux Posterior C VS (axial discrepancy: 121 microns vs 44 and 41 microns respectively). There was a tendency for 24-hour-old inlays to be less accurate than 10-minute-old inlays. The formation of marginal gaps due to contraction of the resin cement was assessed in a light microscope on cemented single-surfaced inlays. Gaps were not formed when enamel margins were etched or dentin margins treated with a dentin-bonding agent of high efficacy. Gaps (2.4-5.6 micron) were formed, however, at untreated dentin margins and at margins treated with dentin-bonding agents of low efficacy.

Inlay/onlay materials based on composite resins have recently been introduced. It was the aim of the present study to investigate the effect of post-curing temperature on selected mechanical properties. Four different composite resins were produced. The composite resins had identical filler content, but varied with respect to the content of the monomers BISGMA, TEGDMA, UEDMA, and HEMA. After initial curing by light, the materials were post-cured at 37, 100, 125, 150, 175, or 200 degrees C for 1 h. We then measured diametral tensile strength, flexural strength, and modulus of elasticity. These properties were found to vary with the composition of the material. Composites containing UEDMA or UEDMA/HEMA were stronger and stiffer than BISGMA/TEGDMA formulations. The optimum post-curing temperature was 150 degrees C, but the increase in strength and stiffness was moderate, only about 9%.

Using bond strength measurements, we investigated a number of related compounds in order to elucidate the role of the surface-active ingredient, N-phenylglycine (NPG), in experimental two-step and three-step bonding protocols resulting in adhesive bonding to dentin. All active compounds identified for the two-step or the three-step protocol were N-aryl-α-amino acids, and the results delineate some of the key features of the NPG molecule for bonding. For the three-step protocol, there was a requirement for a secondary or tertiary aromatic amino group, a carboxylic acid group, and a single (secondary or tertiary) methylene unit between those two functional groups of the amino acid. For the two-step protocol, additional substitutions at the para position of the phenyl ring on the amine improved the bond strength. In both protocols, para-methyl- and para-chloro-substituted NPG analogues ranked higher than NPG. A "catalytic" effect of the aromatic tertiary amino group on the polymerization of the adhering resin in both procedures could not be ruled out.

Composite resin containing silver for radiopacity bonds to the dentin surface of a resected and slightly concave root pretreated with a dentin bonding agent (Gluma). The bond strength between composite and apical dentin is about 18 MPa and is not affected by a preceding root canal filling with eugenol-containing sealer. Contamination with saliva or serum of the Gluma-treated dentin surface reduced the bond strength significantly. No reduction in bond strength is observed when the contamination of the surface is performed before Gluma-application. Microscopy of the borderline between composite and dentin as well as SEM of the composite surface adjacent to dentin revealed a good adaptation which presumably does not allow bacterial penetration.

The effect of immersion in six disinfecting solutions on the accuracy of 10 impression materials was investigated. Impressions were taken of a truncated steel cone. After setting, the impressions were either stored at room temperature for 24 h, for control, or immediately immersed in a disinfecting agent for 60 min (in one case 10 min), and after 24 h poured with gypsum. A steel ring fitting the steel cone was placed on the resulting dies, and the discrepancy between the top surface of the ring and the die was measured. From these measurements the deviation between the base diameter of the die and of the impression was calculated to express the inaccuracy. All impressions except some in Blueprint exhibited a net shrinkage, giving rise to too large die stones and incomplete seating of the steel ring. Blueprint impressions, however, occasionally swelled and resulted in too small die stones and "overseating" of the steel ring. The disinfecting solutions had no significant impact on two impression materials. For the remaining eight materials the accuracy was decreased, increased, or unaffected by the immersion. Generally, the accuracy of the alginates investigated were more affected by the disinfecting solutions than were the elastomeric impression materials. The accuracy of the three alginates was drastically impaired by immersion in 70% ethanol, whereas the remaining five disinfecting solutions had a smaller, though sometimes statistically significant, effect on the accuracy. For the elastomeric materials only a few specific combinations of impression material and disinfecting solution reduced the accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of the content of camphorquinone (CQ), amine (DABE), and inhibitor (MHQ) on the Wallace indentation hardness of light-curing polymers was investigated. The hardness was measured on disc-shaped specimens made from 50 bisphenol-A-glycidyl-dimethacrylate/triethyleneglycol-dimethacryla te-based monomers with various contents of CQ, DABE, and MHQ. When no MHQ had been added, the hardness number decreased with increasing content of CQ. This was also the case with increasing content of DABE, but to a lesser extent. In the presence of MHQ, the contents of CQ and DABE did not influence the hardness number significantly.

In its present version, the Gluma system for bonding restorative resin to dentin involves the application of an enamel bonding agent prior to the composite resin. Conceivably, pretreating the dentin with solutions of amino acids, and incorporating camphorquinone and selected methacrylic monomers into the Gluma adhesive would nullify the need for the enamel bonding agent. A bond strength to dentin of 13.4 MPa was obtained in the control experiment. Using a solution of pyruvic acid and glycine as pretreatment, and an optimized adhesive mixture containing glutaraldehyde, HEMA, BIS-GMA, camphorquinone, and water, bond strengths to dentin of 14.5 MPa and to enamel of 23.3 MPa were obtained. Thus, the new Gluma bonding system gave acceptable bond strengths without the prior application of enamel bonding agents.

Silicoating is a new type of pretreatment of the metal in the resin-bonded bridge technique. The size of bond strength between resin cement and silicoated metal was investigated. Different resin cements, types of metal, and grain sizes of sand used for roughening the metal surface were tested. Furthermore, the effect on the bond strength of contamination with saliva and of thermocycling was measured. There was no difference of importance between the two resin cements tested. Bond strengths obtained with Wirobond were the highest and insensible to changes in resin cement, grain size of sand, and to thermocycling. It was found that sand of the smallest grain size used brought about the highest bond strengths. Contamination with saliva did not significantly reduce the size of the bond strengths. Rinsing the metal surfaces with water or ethanol after contamination restored the bond strengths to their original magnitude. By silicoating, a greater resistance to thermocycling was obtained. Nevertheless, except for Wirobond, a fall in bond strength was measured after thermocycling. Bond strengths of the size of those between etched enamel and composite resin were measured, and the Silicoater method seems a reliable pretreatment of the metal.

Dentin surfaces were treated with various amino acids. The treatment caused an alteration of the dentin surface that influenced the tensile bond strength to a restorative resin obtained with the Gluma system. The bond strengths varied between 5.6 and 14.2 MPa. Among the amino acids tested, N-phenylglycine produced the strongest bonds.

Tensile bond strengths between dentin and a typical restorative resin were measured after the dentin was treated with Gluma. Solutions of phosphoric, pyruvic, nitric, or oxalic acid, also containing various amino acids, were used as pretreatments. Without amino acids in the solutions, the pretreatments conferred bonds of low strength. Use of acidic solutions containing glycine or N-phenylglycine was found to give bonds of high strength to both dentin and enamel.

Effective bonding between restorative resins and hard dental tissues would eliminate the need for retentive undercuts and prevent the formation of marginal gaps. While bonding to enamel has found a satisfactory solution with the advent of the acid etch technique, bonding to dentine has been more elusive. Restorative resins may bond to dentine through mechanisms involving either the inorganic or the organic constituents of the dentine. In the present work the possibility of bonding to the organic part of dentine was investigated. Since the water present in the surface of moist dentine may impede bonding, the research was focused on adhesives that are operational in aqueous environments. Aqueous mixtures of aldehydes and certain active monomers constitute such adhesives. The strength of the bond between a restorative resin and dentine was measured using the mixtures as intermediaries. To remove the smear layer the dentine was pretreated with 0.5 M EDTA, pH = 7.4. Among the aliphatic aldehydes especially propionic aldehyde and glutaraldehyde were found to be effective. Aromatic aldehydes resulted in bonds of low strength. Among the monomers investigated HEMA (hydroxyethyl-methacrylate) gave rise to the bond of highest strength. Using an adhesive based on HEMA and propionic aldehyde or HEMA and glutaraldehyde bond strengths of 15 and 18 MN/m2, respectively, were obtained. The latter adhesive significantly reduced the width of the polymerization contraction gaps between resin and dentine.

The bonding of restorative resins to dentin by means of formaldehyde used in conjunction with an OH-containing monomer as intermediary was investigated. In this way a bonding to the organic constituent of dentin is conceivable. Mean bond strengths of 0.6 kg/mm2 were obtained. Bond strengths of this order of size may be of clinical interest.

The fatigue properties of resinous materials may be interesting from several points of view. A good resistance to fatigue failure is desirable in a denture base material. The possible relationship between fatigue strength and wear constitutes another aspect of interest. The purpose of the present work was to investigate the fatigue strength of various types of resinous materials used in dentistry. It was found that heat-cured denture base materials do not necessarily have higher fatigue strength than cold-cured materials. At low levels of stress a tendency was demonstrated for microfilled resins to show higher fatigue strength than other types of resinous materials. On this basis a connection between wear and fatigue properties may be surmised.

It has been hypothesized that the Wallace indentation hardness of smooth surface resins is a factor of prime importance for the abrasion by food of Class 1 restorations. In the present work factors affecting the hardness of polymers were investigated. In addition the tensile strength of composite resins was measured and related to the catalytic system of the polymer. It was found that for a given composition of the monomer the Wallace hardness number increased with increasing content of inhibitor, decreased with increasing content of peroxide, and was unaffected by changes in the content of amine. The hardness was well correlated with the quantity of double bonds remaining in the polymer. BISGMA-based polymers showed no variation in hardness when the originating monomer varied with respect to content of a bi- or a trifunctional diluting monomer. Light-polymerized polymers were relatively hard as compared to chemically cured materials of adequate setting time. The tensile strength of composite resins was predominantly determined by the monomer content of peroxide and increased herewith. The tensile strength was well correlated with the quantity of remaining double bonds in the constituting polymer.