Dual-cure Composite Resin Research Articles

Effect of temperature on the silane coupling agents when bonding core resin to quartz fiber posts

Objectives To evaluate the effect of different silane agents and air-drying temperatures on bond strength of translucent quartz fibre posts to composite resin. Methods The post surface was etched with 10 vol% hydrogen peroxide for 20 min. A two-liquid coupling agent containing 4-methacryolxyethyl trimellitate anhydride (4-META) and γ-trimethoxysilyil propyl methacrylate (γ-MPTS) and two pre-hydrolyzed single component silanes containing 3-methacryloxypropyltrimethoxysilane (3-MPS) and glycid-oxi-propyl-trimetil-oxi-silane (GPS), respectively, were used for treating the fiber posts. Two different post-silanization drying temperatures were applied (21 and 38 °C). A dual-cure composite resin (Core Paste XP) was selected to build-up the core around posts, obtaining cylindrical specimens that were serially cut in beams and subsequently loaded in tension (μTBS) at a cross-head speed of 1 mm/min until failure. Bond strength data were statistically analyzed by two-way ANOVA and Student–Newman–Keuls tests ( α = 0.05). Results Warm air-drying determined significantly higher bond strengths ( p < 0.001) for glycid-oxi-propyl-trimetil-oxi-silane (11.6 MPa) and 4-methacryolxyethyl trimellitate anhydride/γ-trimethoxysilyil propyl methacrylate silane (11.7 MPa). These two systems exhibited lower bond strengths (6.9 and 8.8 MPa, respectively) than 3-methacryloxypropyltrimethoxysilane (11.0 MPa) when dried at 21 °C. No statistical differences were recorded for 3-methacryloxypropyltrimethoxysilane when drying at 21 or 38 °C. Significance The composition of the silane coupling agent in terms of acidic content, solvent rate or degree of hydrolysis may influence resin/post bond strength when dried at 21 °C. Drying at 38 °C most likely facilitates the evaporation of solvents present in the silane agent, resulting in increased bond strength of the composite resin to the fiber post.

Effect of prolonged photo-irradiation time of three self-etch systems on the bonding to root canal dentine

To evaluate the effect of photo-irradiation time to the adhesive on the regional bond strength of a dual-cure resin core material to root canal dentine using photo and dual-cure adhesives with self-etching primer. Post spaces were prepared in extracted premolars and then the root canal dentine was treated with one of the following bonding procedures: (1) Clearfil SE Bond Primer/Bond (SE), (2) Nano-Bond Primer/Photo-cure adhesive (PNB), (3) Nano-Bond Primer/Dual-cure adhesive (DNB). Photo-irradiation was performed for 10 or 20s from a coronal direction. The post spaces were then filled with a dual-cure composite resin (Build-It FR) and light-cured for 60s. After 24h storage, each specimen was serially sliced into 8, 0.6 x 0.6mm-thick beams for the microTBS test. The bond strength data were divided into coronal and apical regions and analysed using three-way ANOVA and Games-Howell multiple comparison (alpha=0.05). The microTBS of the photo-cure adhesive resin, SE and PNB, significantly decreased (p<0.05) at the apical region when the photo-irradiation time was 10s. However, the bond strength of the SE group was significantly improved at both regions when photo-irradiation time was extended to 20s (p<0.05). There were no differences in microTBS of the photo-cure adhesive resin (PNB) cured for 20s and dual-cure adhesive resin (DNB) (p>0.05). Photo-cure adhesive was effective for application on root canal dentine when the photo-irradiation time was sufficient. Extension of photo-irradiation time to the adhesive improved the bond strength depending on the type of adhesive resin.

ADHESIVE-COMPOSITE INCOMPATIBILITY, PART II

Apart from some questions related to the repairability of resin composite restorations, dentists have always assumed that methacrylate-based resins are compatible with each other. For example, there is no clinically relevant problem in using a microfilled composite to laminate a Class IV restoration made with a hybrid composite, even if they are not of the same brand or manufacturer. In the context of adhesive systems, we have always believed that resin composites, regardless of their type or composition, bond well to all types of bonding agents. However, unexpected debonding of self-cured, core buildup composites that had been bonded with single-bottle adhesive systems was reported about 5 years ago. Subsequent studies demonstrated that there were, indeed, compatibility problems between simplified adhesive systems and self- or dual-cured resin composites. Apparently, when such combinations are used, reduced bond strengths and subsequent failures at the resin-adhesive interface can occur because of adverse reactions between the acidic resin monomers, an integral part of the simplified adhesive systems, and the chemicals involved in the polymerization mechanism of the self- or dual-cured composites, particularly the basic tertiary amines.

ADHESIVE-COMPOSITE INCOMPATIBILITY, PART I

Apart from some questions related to the repairability of resin composite restorations, dentists have always assumed that methacrylate-based resins are compatible with each other. For example, there is no clinically relevant problem in using a microfilled composite to laminate a Class IV restoration made with a hybrid composite, even if they are not of the same brand or manufacturer. In the context of adhesive systems, we have always believed that resin composites, regardless of their type or composition, bond well to all types of bonding agents. However, unexpected debonding of self-cured, core buildup composites that had been bonded with single-bottle adhesive systems was reported about 5 years ago. Subsequent studies demonstrated that there were, indeed, compatibility problems between simplified adhesive systems and self- or dual-cured resin composites. Apparently, when such combinations are used, reduced bond strengths and subsequent failures at the resin-adhesive interface can occur because of adverse reactions between the acidic resin monomers, an integral part of the simplified adhesive systems, and the chemicals involved in the polymerization mechanism of the self- or dual-cured composites, particularly the basic tertiary amines. At least one research group has expanded the information on this issue by further investigating the mechanisms involved in this phenomenon. This group demonstrated that not only adverse chemical reactions but also the permeability of such simplified systems contribute to the compromised bonding. This issue has profound clinical implications in view of the wide use of self- and dual-cured composites as core buildup materials and in the bonding of indirect restorations and endodontic posts. Some of the most representative studies of this group are described in this Critical Appraisal. Part II will appear in the next issue of the Journal.

Volumetric dimensional change of six direct core materials

Objectives. This study evaluated the influence of water on the volumetric dimensional change of six direct placement core build-up materials by using Archimedes' principle. Methods. The effect on dimensional change due to the setting reaction was determined through the use of a silicone oil storage medium. The materials used were two dual-cured resin composites (CoreStore and Build-It FR), two chemically activated resin composites (CorePaste and Ti-Core), one metal-reinforced glass ionomer cement (Ketac-Silver), and one resin-modified glass ionomer (Fuji II LC Core). Using the manufacturers' instructions for each material, cylindrical specimens were prepared with dimensions of 7±0.1 mm in diameter and 2±0.1 mm in height. Each material had four groups ( n=5) based on storage conditions; silicone oil at 23 and 37 °C and distilled water at 23 and 37 °C. A 0.01 mg resolution balance was used to determine volumetric dimensional change using an Archimedean equation. Measurements were made 30 min after mixing, and at the time intervals of 1, 14, and 56 days. Results. All materials exhibited dimensional change. Ketac-Silver had the most shrinkage in silicone oil and Fuji II LC showed the highest expansion in distilled water. The glass ionomer materials showed more change than did any of the resin composite materials. Significance. Current direct placement core materials show variation in the amount of volumetric dimensional change seen over a period of 56 days.

A clinical evaluation of porcelain inlays

Sparse data are available concerning the survival rate of porcelain inlays or onlays to inform the dentist and address the expectations of patients. A total of 25 posterior porcelain inlays were inserted by two dentists at a private Danish clinic; the time elapsed since cementation was 20 to 57 months (average 40.4 months). Tooth preparations for MOD porcelain inlays were completed for 13 premolars and 12 molars but most did not include cuspal coverage. All inlays were constructed at the same commercial dental laboratory and according to the manufacturer's recommendations; they were etched and treated with silane before they were cemented. The cementation included etching of cavosurface enamel and treatment of the dentin with a dentinal bonding system. A thin layer of composite resin luting agent was applied to the tooth preparation before the porcelain inlays were cemented. The first 10 porcelain inlays were cemented with a light-curing composite resin cement and the remaining 11 with a dual-curing composite resin cement. Twelve of the 25 porcelain inlays failed and were replaced during the observation period. Ten failures were due to a fracture of the inlay, one was caused by secondary caries, and the final failure was attributed to a marginal gap between the inlay and proximal tooth surface. Porcelain inlays cemented with light-curing composite resin exhibited more failures (p = 0.05) than those cemented with dual-curing composite resin. In addition, more failures (p = 0.07) were recorded among inlays inserted in molars than among those in premolars.

支台築造用コンポジットレジンに関する研究 第９報サーマルサイクルの影響

In the previous report, the shear bond strength of dual-cured composite core resin to the dentin treated with 14 combinations of pretreatment agents, including primer and bonding agent, was measured before thermocycling. In this study, 6 combinations were selected, and the shear bond strengths after thermocycling 5, 000 and 10, 000 times were measured and compared.The following results were obtained:1. When dentin was treated by the conventional method with K-etchant and Clearfil photo bond, the shear bond strength increased after thermocycling in comparison with before thermocycling. After bond strength tests, interface failure between resin and dentin occurred, and SEM imaging showed some spaces between resin tags and dentinal canals.2. When 10% NaOCL gel was used, the bond strength before thermocycling indicated almost the same value as the other pretreatment agents, but increased remarkably after thermocycling.3. When both ED primer and Panavia 21 were used, bond strength before thermocycling showed comparatively high values, but after thermocycling decreased distinctly unless the pretreatment by 10% NaOCl gel was added.4. The combination of ED primer and Clearfil photo bond was evaluated to be the most desirable of all combinations examined. Furthermore, SEM imaging of the dentin after bond strength tests in this combination showed no spaces between resin tags and dentinal canals.

支台築造用コンポジットレジンに関する研究 第８報 既製ポストの保持力について

In continuation of our studies concerning composite resins for dowel-cores, a new dentin primer was examined to improve the retentive force of prefabricated posts to the dentin.In this study, four series of treatment procedure to be performed on the root canal dentin before cementation and no treatment as the control were examined. After dentin treatment, prefabricated posts were cemented with dual-cured composite core resin and adhesive resin cement. Then their early retentivities were measured and compared with one another.The following results were obtained;1. A new dentin primer, Teeth Primer, was very effectivity for improving the retentivity of prefabricated posts in the root canal.2. When using dual-cured composite core resin as a luting agent, the combination of Teeth Primer and Clearfil Photo Bond was the most recommendable for clinical use, because of its short treating time as well as the very high retentive force. It means that the fixation of prefabricated posts in the root canal and the fabrication of composite resin cores can be performed at the same time.3. When using paste-type Panavia as a luting agent, acid etching was really effective for retention of the posts. However, the single use of Teeth Primer was estimated to be more desirable clinically because of its shorter treating time.

象牙質および支台築造用材料に対する各種合着材の接着強さ

In this study, human dentin, composite core resin and dental alloy (Ag-Pd-Cu-Au) were bonded to the stainless steel by two kinds of adhesive cements and a glass ionomer cement. The adhesive strength of each specimen was measured after 24 hours (thermocycle 0) and after thermocycling 5, 000 times as well and compared with one another.Furthermore, the influence of pretreating agent on adhesive strength to the composite core resin and the dental alloy was examined.The following results were obtained;1. Panavia 21 exhibited high early bond strength and stable durability to the human tooth andthe dual-cured composite core resin comparing with the other cements.2. Super bond C & B showed high early bond strength to the human tooth, the dual-curedcomposite core resin and the Ag-Pd-Cu-Au alloy, but its durability was very poor.3. After applying pretreating agent, the durability of Panavia 21 to the Ag-Pd-Cu-Au alloydecreased remarkably.4. Fuji BOND indicated low early adhesive strength and very poor durability.

The effect of porcelain color on the hardness of luting composite resin cement

Visible light- and dual-curing composite resin luting cements were cured under porcelain disks of different colors to examine the effect of porcelain color on surface hardness. Knoop microhardness measurements were made at exposure times of 48, 72, and 120 seconds. Higher levels of hardness were obtained with dual-cured resin. Visible light-cured resin irradiated through colored porcelain required more prolonged exposure times to reach a degree of hardness approaching that of dual-cure resin. From the standpoint of microhardness, dual-cured composite resin is preferred for luting porcelain restorations of ≥2 mm thickness.

支台築造用コンポジットレジンに関する研究 第５報 デュアルキュアー型について

Both visible light and chemical cured composite resins have been used in practice for rebuilding of the endodontically treated tooth.In this study, a new type of curing method, dual cure, was fundamentally evaluated. After the irradiation of light to the dual-cured and light-cured resin specimens, their degree of conversion were measured at several depth of the resin specimens by a Fourier transform infrared spectrometer having a microscope and the obtained values were compared with one another.The results were as follows:1. The maximum degree of conversion in dual-cured composite resin was 83% when irradiated for 90 seconds only from the top of the specimen and 92% in visible light-cured one for 90 seconds, 30 seconds from the top and 30 seconds each from the side walls bilaterally.2. There was an inhibition area of polymerization due to the existence of oxygen, up to about 1mm depth from the top of the specimens in both composite resins.3. The maximum degree of conversion in dual-cured resin without the irradiation, actually chemical cure only, amounted to 76% at all depth of the specimens.4. The irradiation from above only showed the highest degree of conversion at the shallow area in both dual-cured and visible light-cured resins. On the other hand, lateral irradiation resulted in the comparatively high degree of conversion at the wide area up to the deep layer.

支台築造用コンポジットレジンに関する研究 第７報 各種象牙質処理剤が接着強さに与える影響について

The adhesive strength of dual-cured composite resin for dowel-cores to the dentin treated with various combinations of pretreatment agents, primers and bonding agent, was measuredand compared with one another. In this study, four trial materials were used, that is 10% NaOClgel, tooth primer, paste-type PANA VIA and dual-cured composite resin.The following results were obtained.1. In all pretreatment agents, there were some combinations of primers and bonding agents, with which high adhesive strength was obtained.2. In consideration of the total treatment time, the combination of tooth primer and Clearfilphoto bond was evaluated to be the most desirable because of high adhesive strength and thereasonable treatment time of 100 sec.3. Paste-type PANAVIA tended to decrease the adhesive strength to the dentin.4. Cohesive failure in the dentin occured after compressive shear adhesive strength tests intwelve of fourteen combinations investigated.5. The SEM image of the dentin treated with tooth primer showed less demineralization thanthat of K-etchant gel.

A CAD‐CAM Ceramic Inlay Technique

This article details the technique of a Cerec computer-aided designed (CAD) and computer-aided manufactured (CAM) inlay. Using a ceramic material the unit can mill an inlay from an optical "impression" that is then bonded to place using a dual-cure composite resin cement.