Enamel-dentin crown fractures bonded with various bonding agents.
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Comparative Study↗
Biomedical subjects
E C Munksgaard
Publications and source records attributed to E C Munksgaard.
Enzymatic hydrolysis of (di)methacrylates and their polymers.
Di- and monomethacrylates hydrolyze to methacrylic acid and the alcohol part at neutral pH catalyzed by an unspecific esterase (hydrolase) and by enzymes in saliva. The rate constants of the enzymatic hydrolysis of various (di)methacrylates increase in the following order: HPMA less than BISGMA less than LAMA less than DECMA less than TEGDMA less than UEDMA less than DEGDMA. Esterase added to aqueous slurries of various powders made of polymerized BISGMA/TEGDMA-mixtures gave rise to liberation of methacrylic acid, presumably deriving from degradation of those of the dimethacrylates only bonded in the matrix by one end of the molecule. It was estimated that a TEGDMA-polymer will be hydrolyzed faster than a BISGMA-polymer. It is proposed that hydrolases in saliva increase the wear rate of composite resin fillings.
Acrylates↗
Enzymatic degradation of BISGMA/TEGDMA-polymers causing decreased microhardness and greater wear in vitro.
The microhardness of the surfaces of BISGMA/TEGDMA-polymers decreased after treatment with pork liver esterase for 48 h in concentrations greater than or equal to 0.05 U/ml. This softening effect on BISGMA/TEGDMA-polymer surfaces was also shown as an increased wear rate of the polymers in the presence of esterase measured by a laboratory abrasion method. In this method, polymer cylinders were vigorously shaken in an aqueous slurry containing abrasive particles. The shaking was performed for 3 s followed by a rest period of either 100 or 200 s. This was repeated for 24 h. A greater mean loss of weight of the cylinders was measured when esterase was present in the slurry and the loss of weight increased significantly from 6.7% to 23.8% (P less than 0.001) when the rest period was increased from 100 s to 200 s. The results indicate that enzymatic hydrolytic activity in the mouth will contribute to a breakdown of composite resin fillings.
Acrylates↗
Amine-induced polymerization of aqueous HEMA/aldehyde during action as a dentin bonding agent.
Aqueous mixtures of HEMA with glutaraldehyde or propionaldehyde polymerize by addition of catalytic amounts of amines or amino acids. The maximal reaction velocity of the transformation of HEMA/glutaraldehyde with glycine was obtained at pH 0.8. Kinetic data suggested a second-order reaction between glutaraldehyde and glycine, and solubility data suggested formation of a cross-linked polymer. A relatively high bond strength between dentin and resin composite was obtained by pre-treatment of dentin with Gluma (35% HEMA, 5% glutaraldehyde in water) adjusted to pH 1.0 with hydrochloric acid. It is proposed that on application of Gluma, amino-group-containing substances in dentin react with glutaraldehyde and start the formation of a HEMA polymer. This product may be cross-linked by an alpha,beta-unsaturated glutaraldehyde aldol condensation product and may bond to dentin by aldehyde fixation to dentin proteins. Resin composite will bond to this product by copolymerization.
Acrylates↗
[Contact dermatitis, due to (di)methacrylates, on the hands of dental personnel].
Eight dentists and one dental assistant have developed allergic contact dermatitis caused by exposure to (di)methacrylates, especially those found in resins, in dentin bonding agents, in rebasement and in prosthetic materials. The eczema is characterized by its location on the first, second and third finger of the left hand showing redness, desquamation, fissuring and excoriations. Patch testing with various test substances revealed positive reactions towards EGDMA in eight cases. It is suggested that this reaction was a cross-reaction and that the sensibilization was caused by MMA, TEGDMA, HEMA and/or BUDMA. One of the eight dentists had to give up practising.
Acrylates↗
Saliva contamination vs. efficacy of dentin-bonding agents.
The efficacy of two dentin-bonding agents (Gluma and Scotchbond Dual Cure) was investigated in vitro with or without saliva contamination of the dentin before or after application of the adhesive. The efficacy of the bonding agents was evaluated by a shear-bond strength test and a cavity test. When the dentin surface was contaminated, either before or after application of one of the bonding agents, the shear bond strength was reduced, but the difference between contaminated and non-contaminated specimens was not statistically significant. In the cavity test, the width and the extent of the marginal contraction gap were markedly increased when the dentin was contaminated with saliva before the bonding agent was applied. If the contamination happened after application of the adhesive, the efficacy of Gluma was further reduced, while that of Scotchbond was significantly improved. (This phenomenon has been investigated in detail in an accompanying paper.) The clinical consequence of saliva contamination seems to be that when Gluma is used as dentin-bonding agent, the contaminated area must be removed operatively, and then each of the various bonding procedures must be repeated.
Dental Bonding↗
Improved efficacy of some phosphate-based dentin-bonding agents.
The gap-reducing efficacy of four phosphate-based dentin-bonding agents was tested after various treatments of the dentin and/or the bonding agents. The investigation was carried out on extracted human teeth. One of the root surfaces was ground flat, and a cylindrical butt-joint cavity was prepared in the ground dentin surface. It was found that the efficacy of two of the adhesives, presumably being chloro-substituted phosphates, could be markedly improved if the primed dentin was rinsed with copious amounts of water, dried by compressed air, and a second layer of bonding agent applied. The mechanism behind this improvement is assumed to be the formation of hydrogen chloride, which dissolves part of the smear layer.
Dental Bonding↗
[Retrograde root obturations employing composite and a dentin bonding agent: adaptions of the filling materials and bond strength].
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.
Composite Resins↗
[Retrograde root canal filling using resin and a dentin bonding agent: analysis of failures].
With Gluma, an aqueous solution of 5% glutaraldehyde and 35% HE-MA, resin may be chemically bonded to a root surface. In the article failures of apical retrograde root fillings with Gluma and resin (retroplast) were studied, clinically and radiographically, as well as by microscopy of ground sections of extracted teeth or by scanning electron microscopy of loosened retroplast fillings. Out of 52 failures, 23 were not related to retroplast (18 had root fracture). Of the remaining 29 cases, 26 were reoperated. More than half of the failures had loose retroplast fillings. The loosening could be caused by: exceeded working time for the resin or moisture, blood or saliva present on the root before filling, debris on the root surface, possibly because of corrosion, or the presence of phenol in the root canal. In five cases of failure there were denuded root canals. Four cases (of 800) with rapidly developing osteitis might have been due to contamination of bone and soft tissue by EDTA, non-polymerized resin, alcohol or glutaraldehyde.
Aldehydes↗
[Retrograde root canal filling using resin and a dentin bonding agent: operative procedures].
Using a specially designed filled resin and the bonding agent Gluma, the aims were to obtain a thin retrograde filling covering the slightly concave root surface which would close all root canals and avoid excess filling material. To achieve a strong bond, the resin must be applied to an absolutely dry Gluma surface, free of all traces of blood or saliva. Hemostasis was obtained primarily by applying 1% adrenalin and by use of a needle suction tip. Absence of moisture was obtained by removing all soft tissues from the cavity, using dry compressed air and avoiding condensed moisture from a cool resin. To avoid loosening of the filling, the working time of the resin must not be exceeded, and removal of excess filling material must not be done before polymerization is complete. Contamination of the various chemicals and filled resin must be avoided in order to avoid damage to the surrounding tissues.
Aldehydes↗
[Retrograde root obturations using resin and a dentin bonding agent: a preliminary histologic study of tissue reactions in monkeys].
The histologic response to a new retrograde root filling procedure using composite and a dentin bonding agent (Gluma) was examined in two monkeys (Cercopithecus aethiops). Infected root canals in canines and incisors were retrograde sealed and a histologic examination performed after 1 year. Among three canines, two showed epithelial proliferation on the resected root surface, apparently originating from the incision which had been placed very close to the level of resection. In the third canine, filled with a composite containing tricalciumphosphate, there was not only reformation of new Sharpey's fibers, but also, seen for the first time, regeneration of new cementum directly upon the retrograde filling material (Fig. 1). Two incisors were extracted, the apices resected, a retrofilling applied, and the incisors replanted. In this way any interference by epithelium could be avoided. After 1 year, both teeth showed a narrow fibrous zone without inflammation opposite the filling material (Fig. 2). The surprising finding that a composite could allow complete PDL regeneration including cementum upon the retrograde material implies that a new biologic retrograde root filling principle is at hand. Experiments are now in progress to further characterize the necessary condition for cementum repair upon composite used as a retrograde root filling material.
Animals↗
[Retrograde root filling utilizing resin and a dentin bonding agent: indication and applications].
With Gluma a methacrylate-based resin may be chemically bonded to dentin with considerable strength. Resin may therefore be used for retrograde root fillings. Whereas a retrograde amalgam filling demands a box-like preparation, retroplast (Gluma and resin) may be applied to a slightly concave root surface. It may therefore be employed in areas normally inaccessible with amalgam technique. Retroplast can thus be used on roots of all molars and to restore root perforations, root resorptions, cracks, grooves and defects of the root. In addition on lateral canals, on extremely thin roots and to cover perforating root canal posts, this technique can also be used. Dentin/root-cement transplantation may be performed for the purpose of reattachment. The article discusses the technique and its applications with examples showing that it may result in satisfactory healing.
Composite Resins↗
Effect of load-cycling on bond between composite fillings and dentin established by Gluma and various resins.
Cylindrical dentin cavities, pretreated with Gluma and various resins, were filled with Silux, P-30, or Concise. Marginal integrity was in most instances obtained when experimental resins containing propionic aldehyde were used. The bond between composite and dentin established in this way was tested by load-cycling. Cervical located cavities in extracted human teeth, approximately one-half of the margins in dentin, were etched and treated as above. Fillings made of Silux, P-30, or Concise exhibited margins without stain upon axial loading in most cases. The frequency of staining increased when Dycal was used as cavity liner, but were absent in all cases when Concise was used as filling material. The content of propionic aldehyde in the intermediary resin layer may reduce the oxygen tension at the interface and thereby increase the rate of the polymerization at this location.
Acrylic Resins↗
Bonding of restorative resins to dentine: status of dentine adhesives and impact on cavity design and filling techniques.
In conjunction with the acid etch technique for bonding of restorative resins to enamel, an effective bonding to dentine would eliminate the need for retentive undercuts and ensure a tight marginal seal. Bonding to dentine can be achieved through dentine adhesives. These may be divided into Ca2+-bonding and collagen-bonding types. Several Ca2+-bonding adhesives are based on phosphate methacrylates. Adhesives of this type mediate a bond strength to dentine not exceeding 10 MPa. In contrast, Bowen's bonding system and the Gluma system yield bond strengths higher than 10 MPa. The two latter systems have recently been conceived in simplified versions. In general, the higher the bond strength to dentine mediated by an adhesive, the smaller are the marginal gaps formed by a composite resin polymerizing in a dentine cavity treated by the adhesive. The size and the shape of the cavity influence the width of the marginal gaps. A cavity having a V-shape gives rise to smaller gaps than box-shaped cavities. A filling technique with two 'inclining' layers reduces the width of marginal gaps. Combination of certain Ca2+-bonding and collagen-bonding adhesives results in increased bond strength and smaller marginal gaps.
Adhesives↗
Dentin-polymer bond established by Gluma and tested by thermal stress.
The walls of cylindrical cavities in human dentin were treated with Gluma and various resins before filling with either a microfilled or a macrofilled composite (Silux, P-30 or Concise). The extent of gaps (crevices) along the tooth/filling interface was observed before and after thermal cycling at restorations polished either 10 min or 24 h after curing of the composite. Application of a resin containing polymerization initiators and 1% propanal before filling with Silux or Concise resulted in restorations without contraction gaps along the tooth/filling interface. When P-30 was used in this procedure, one of six of the fillings exhibited gaps, but none of the six did so when removal of the marginal excess was postponed for 24 h.
Aldehydes↗
Wall-to-wall polymerization contraction of composite resins versus filler content.
Various amounts of microfiller, condensed microfiller, prepolymer plus microfiller, or macrofiller were added to an unfilled light-curable resin. The marginal adaptation of these experimental resin/filler mixtures was studied by measuring the wall-to-wall polymerization contraction (wtw-contraction) in dentin cavities in vitro. The investigation showed that increasing amounts of microfiller did not affect the wtw-contraction. However, mixtures made by the three other fillers showed a decreasing wtw-contraction with increasing filler concentration.
Bisphenol A-Glycidyl Methacrylate↗
[Polymer-dentin adhesion on the basis of various adhesives and GLUMA].
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Adhesiveness↗