Surface roughness average and scanning electron microscopic observations of resin luting agents

The objective of this work was to evaluate the surface roughness changes of three current resin cements after tooth brushing simulation, as well as discuss its relation with scanning electron microscopic observations. The materials employed were Enforce Sure Cure (Dentsply), Rely X (3M-ESPE) and Variolink II (Vivadent). They were subjected to brushing abrasion (100,000 strokes for each specimen) and the surface roughness alterations (before and after strokes) were detected. For each roughness test condition, specimens were coated with gold-palladium and observed on a DSM 900 Zeiss scanning electron microscope. Roughness changes values (Ra) were statistically increased after brushing strokes. Based on the microscopic observations and roughness changes analysis, all cements studied became rougher after brushing strokes.     

Effect of surface treatment of titanium posts on the tensile bond strength.

OBJECTIVES: Retention of composite resins to metal can be improved when metal surfaces are conditioned. The purpose of this investigation was to investigate the effect of two conditioning treatments on the tensile bond strength of four resin-based luting cements and zinc phosphate cement to titanium posts. METHODS: The effect on tensile bond strength of (1) air-particle abrasion (50 microm Al2O3) and (2) silica coating (30 microm SiO(x)) and silanization of tapered titanium posts prior to luting with any of the four resin composite luting cements (Compolute) Aplicap, Flexi-Flow cemTM, Panavia 21 EX, Twinlook) were evaluated. The posts luted with zinc phosphate cement (Tenet) were considered as the control group. Following endodontic preparation of 100 intact anterior human teeth with hand instruments, the post spaces were prepared using the opening drills of the corresponding size of the posts. All posts were cemented into the roots according to the manufacturer's instructions of each cement. The specimens were first stored in water at 37 degrees C for 24 h and then subjected to thermocycling (5000 cycles, 5-55 degrees C, 30 s). The tensile strength values were measured on a universal testing machine at a cross-head speed of 0.5 mm/min. Data were analyzed statistically using ANOVA and corrected with Scheffé-test due to the significance levels (P<0.05). RESULTS AND SIGNIFICANCE: The composite resin luting cements did not show significant differences (P<0.05) showing values between (352+/-76N-475+/-104N) when the posts were air-abraded. After silica coating and silanization, significantly higher (P<0.05) tensile strengths were obtained for Compolute Aplicap (600+/-123N) than those of the other luting cements (Flexi-Flow cemTM: 191+/-62N; Panavia 21 EX: 375+/-77; Twinlook: 430+/-78N). No significant differences (P>0.05) were found between the tensile strength of the posts luted with zinc phosphate (414+/-102N) and the resin composite cements. Silica coating and silanization revealed the highest tensile bond strength in posts luted with Compolute Aplicap but it was not effective for the other experimental groups. Zinc phosphate cement exhibited tensile bond strength as good as resin composite cements.     

Microhardness of different resin cement shades inside the root canal

Objectives: To compare microhardness along the root canal post space of two resin cements in different shades and a dual-cure resin core material. Study Design: Root canals of 21 bovine incisors were prepared for post space. Translucent posts (X°Post, Dentsply DeTrey) were luted using one the following resin luting agent: Calibra (Dentsply DeTrey) in Translucent, Medium and Opaque shades, RelyX Unicem (3M ESPE) in Translucent, A2 and A3 shades and the dual-cure resin core material Core°X flow. All materials were applied according to manufacturers' instructions and were all photopolymerized (Bluephase LED unit, Ivoclar Vivadent, 40s). After 24 hours, roots were transversally cut into 9 slices 1 mm thick from the coronal to apical extremes, three corresponding to each root third. Then, VHNs were recorded (100gf, 30 s) on the resin luting materials along the adhesive interface in all sections. Data were analyzed by two-way ANOVA and SNK tests (α=0.05). Results: A significant influence on microhardness of resin luting material in their respective shades (p<0.0001), root third (p<0.0001) and interactions between them was detected (p<0.0001). RelyX Unicem cement showed the highest microhardness values and Calibra the lowest, regardless of the shade selected. All resin luting materials tested exhibited a significantly higher microhardness in the cervical third. Conclusions: Microhardness of resin luting agents tested inside the canal is dependent on material brand and resin cement shade seems to be a less relevant factor. Microhardness decreased along the root canal, regardless of the shade selected.     

Dentin bonding of cements. The bonding of cements with dentin in combination with various indirect restorative materials

The number of both luting agents and restorative materials available on the market has rapidly increased. This study compared various types of luting agents when used to bond different indirect, laboratory restorative materials to dentin. Cylinders were produced of six restorative materials (gold alloy, titanium, feldspathic porcelain, leucite-glass ceramic, zirconia, and an indirect resin composite). Following relevant pretreatment, the end surface of the cylinders were luted to ground, human dentin with eight different luting agents (DeTrey Zinc [zinc phosphate cement], Fuji I [conventional glass ionomer cement], Fuji Plus [resin-modified glass ionomer cement], Variolink II [conventional etch-and-rinse resin cement], Panavia F2.0 and Multilink [self-etch resin cements], RelyX Unicem Aplicap and Maxcem [self-adhesive resin cements]). After water storage at 37 °C for one week, the shear bond strength of the specimens was measured and the fracture mode was examined stereo-microscopically. Restorative material and luting agent both had a significant effect on bond strength and there was a significant interaction between the two variables. The zinc phosphate cement and the glass ionomer cements resulted in the lowest bond strengths, whereas the highest bond strengths were found with the two self-etch and one of the self-adhesive resin cements.     

6种复合树脂粘接剂与纤维增强型复合树脂根管桩的粘接强度研究

目的评价6种复合树脂粘接剂与带有半渗透网状复合基质的纤维增强型复合树脂根管桩的粘接强度。方法实验分为6组,分别为纤维增强型复合树脂根管桩和6种复合树脂粘接剂模块,每组7个样本。用粘接树脂活化剂处理各组根管桩表面5min,将粘接剂模块粘接到根管桩表面并固化,37℃下储存各组样本20h后,万能实验机进行剪切粘接强度测定。结果6种不同复合树脂粘接剂与纤维增强型复合树脂根管桩粘接后,各组根管桩表面剪切粘接强度之间的差异无统计学意义（F=2.32,P=0.45）。结论6种复合树脂粘接剂均适用于纤维增强型复合树脂根管桩的粘接。     

Bonding of resin composite luting cements to zirconium oxide by two air-particle abrasion methods

OBJECTIVE: This study evaluated the shear bond strength of two resin composite luting cements to zirconium oxide ceramic substrate using two air-particle abrasion methods. METHODS: Two resin composite cements, RelyX Unicem (3M ESPE) and Panavia F (Kuraray), each with an acidic composition, were used in combination with a zirconium oxide (DCS Dental AG) substrate containing Al2O3 and SiO2 (Rocatec system, 3M ESPE) and two air-particle abrasion methods. The shear bond strength of the resin composite cement to the substrate was tested after the samples were either water-stored for one week or thermocycled following 24 hours of water storage. RESULTS: The RelyX Unicem resin composite cement specimens with the Rocatec treatment (20.9 +/- 4.6 Mpa and 20.1 +/- 4.2 MPa, respectively, n = 12) demonstrated the highest shear bond strength. Alternatively, the lowest values were obtained for the Panavia F resin cement samples, with Al2O3 air-particle abrasion in both storage conditions, water storage for one week (17.7 +/- 8.9MPa) or thermocycling after 24 hours of water storage (16.3 +/- 4.9 MPa). Neither storage condition or particle abrasion system significantly affected shear bond strengths (ANOVA, p > 0.05). CONCLUSION: It was concluded that two different surface conditioning methods and storage conditions did not significantly affect the bonding properties of Panavia F and RelyX Unicem resin composite luting cements to Zirconia.     

Bonding of restorative materials to dentin with various luting agents

The aim was to compare eight types of luting agents when used to bond six indirect, laboratory restorative materials to dentin. Cylinders of the six restorative materials (Esteticor Avenir [gold alloy], Tritan [titanium], NobelRondo [feldspathic porcelain], Finesse All-Ceramic [leucite-glass ceramic], Lava [zirconia], and Sinfony [resin composite]) were ground and air-abraded. Cylinders of feldspathic porcelain and glass ceramic were additionally etched with hydrofluoric acid and were silane-treated. The cylinders were luted to ground human dentin with eight luting agents (DeTrey Zinc [zinc phosphate cement], Fuji I [conventional glass ionomer cement], Fuji Plus [resin-modified glass ionomer cement], Variolink II [conventional etch-and-rinse resin cement], Panavia F2.0 and Multilink [self-etch resin cements], and RelyX Unicem Aplicap and Maxcem [self-adhesive resin cements]). After water storage at 37°C for one week, the shear bond strength of the specimens (n=8/group) was measured, and the fracture mode was stereomicroscopically examined. Bond strength data were analyzed with two-factorial analysis of variance (ANOVA) followed by Newman-Keuls' Multiple Range Test (α=0.05). Both the restorative material and the luting agent had a significant effect on bond strength, and significant interaction was noted between the two variables. Zinc phosphate cement and glass ionomer cements produced the lowest bond strengths, whereas the highest bond strengths were found with the two self-etch and one of the self-adhesive resin cements. Generally, the fracture mode varied markedly with the restorative material. The luting agents had a bigger influence on bond strength between restorative materials and dentin than was seen with the restorative material.     

Curing shrinkage and volumetric changes of resin-modified glass ionomer restorative materials

Objectives. The objective of the study was to evaluate initial curing shrinkage and volumetric change during water storage of six resin-modified glass ionomer cements (Dyract, DeTrey Dentsply; Fuji II LC, GC Dental Int.; Ionosit Fil, DMG; VariGlass VLC, DeTrey Dentsply; Vitremer, 3M Dental Products; Photac-Fil, ESPE), a hybrid composite (blend-a-lux, Blendax) and a chemical-cured glass ionomer cement (ChemFil Superior, DeTrey Dentsply).Methods. The curing shrinkage was determined 5 min and 24 h after polymerization and mixing, respectively. Volumetric changes were examined after 14 d and 28 d water storage. Curing shrinkage and volumetric changes were evaluated using the hydrostatic principle. In addition, the total water content of the materials was measured after 28 d water storage.Results. Curing shrinkage of most of the resin-modified glass ionomers was greater than the hybrid composite and the chemical-cured glass ionomer cement. After a 28 d water storage, the resin-modified glass ionomers showed volumetric expansion and the chemical-cured glass ionomer showed volumetric loss. All of the examined glass ionomer materials had a higher total water content than the composite.Significance. The large curing shrinkage of the resin-modified glass ionomer materials measured in this in vitro study could affect the marginal integrity of glass ionomer restorations.     

Mechanical properties of luting cements after water storage

This study determined the effect of water storage on flexural strength (FS) and compressive strength (CS) of 12 luting cements from different material classes. In addition, the influence of the curing method on the mechanical properties was investigated. The materials examined were two zinc phosphate cements (Harvard cement and Fleck's zinc cement), two glass ionomer cements (Fuji I and Ketac-Cem), three resin-modified glass ionomer cements (Fuji Plus, Fuji Cem and RelyX Luting), four resin cements (RelyX ARC, Panavia F, Variolink II and Compolute) and one self-adhesive universal resin cement (RelyX Unicem). The samples were prepared and tested according to ISO specifications. Specimens for FS and CS were loaded to fracture at a constant crosshead speed of 1 mm/minute. The mechanical properties were measured after the materials were stored in distilled water at a temperature of 37.0 +/- 1.0 degrees C for 24 hours and 150 days after mixing. In a one-way ANOVA, multiple mean value comparisons using Duncan's multiple comparison tests were performed. Resin cements had the highest flexural and compressive strengths, followed by self-adhesive universal resin cement. These materials were statistically stronger than resin-modified glass ionomer cements, glass ionomer cements and zinc phosphate cements.     

Various conditioning methods for root canals influencing the tensile strength of titanium posts

Conditioning the root canal is frequently advised to achieve high post-retention when resin composite luting cements are used. However, manufacturers' instructions for this purpose differ widely from one another. The aim of this study was to compare the tensile bond strengths of passive, tapered, titanium root posts that were luted with four different resin composite cements (Compolute Aplicap, Flexi-Flow cem, Panavia 21 EX, Twinlook) in the root canals at three conditions, namely (i) no conditioning, (ii) etching with 37% phosphoric acid, and (iii) etching + bonding agent application. Panavia 21 EX was further tested after using the primer for the post-surface according to the manufacturer's recommendations. The posts luted with zinc phosphate cement (Tenet) acted as the control group. Following endodontic preparation of 140 intact anterior teeth with hand instruments, the post-spaces were prepared using the opening drills of the corresponding size of the posts. The samples were first stored in water at 37 degrees C for 24 h and then thermocycled (5000 cycles, 5-55 degrees C, 30 s). The tensile strength values were measured with the universal testing machine at a crosshead speed of 0.5 mm min(-1). The data were analysed statistically using anova and corrected with Scheffé test due to the significance levels (P < 0.05). The tensile bond strengths of the titanium posts after luting with various cements and thermocycling were affected by the conditioning systems used for the root canals. Tensile bond strengths were the highest with Flexi-Flow (475 +/- 78 N) followed in descending order by Panavia 21 EX (442 +/- 97 N), Twinlook (430 +/- 78 N) and Compolute Aplicap (352 +/- 76 N) after conditioning the root canal. The use of primer on the post improved the tensile bond strength compared with the non-conditioned group for the Panavia 21 EX group (375 +/- 77 N) (P < 0.001). Tensile bond strengths obtained after luting the posts with zinc phosphate cement (414 +/- 102 N) were not significantly different (P < 0.05) than those of resin composite cements. Although the importance of conditioning the root canal was evident for Panavia 21 EX, it was not the case for the other luting cements tested.     

Curing efficiency of a photo- and dual-cured resin cement polymerized through 2 ceramics and a resin composite

PURPOSE: The influence of the curing mode (dual vs light) and of the photopolymerization through ceramic or resin composite on the degree of remaining carbon bonds was investigated via infrared spectroscopic analysis for 1 resin cement (Calibra, Caulk/Dentsply). MATERIALS AND METHODS: The 0.5-mm cement layer was photopolymerized for 40 s through the 2-mm-thick ceramic Empress 2 (Ivoclar) and Vitadur Alpha (Vident) and the laboratory-processed resin composite Sinfony (3M/ESPE). RESULTS: The dual-cured system polymerized better than the light mode. Photopolymerization of the resin cement through the translucent materials reduced its curing efficiency in both curing modes. The resin composite induced a more negative effect than the 2 ceramics tested. CONCLUSION: The curing mode and photopolymerization of dual-cured resin cements through esthetic restorative materials affects the degree of remaining double carbon bonds.     

Effect of toothbrushing on fluoride release of polyacid-modified composite resins

The aim of the study was to evaluate the fluoride release of polyacid-modified composite resins (Dyract, Compoglass) submitted to brushing abrasion. Twenty samples were taken from each material and stored in a buffer solution (pH 4.0) for 12 days. Each day, the samples were transferred to a fresh solution. Ten samples of each material were brushed in an automatic tooth-brushing machine (250 strokes, 260-g load) every fourth day. The remaining samples were not subjected to brushing. Fluoride content of the solutions was measured with a fluoride sensitive electrode after the addition of TISAB. Statistical analysis demonstrated significant differences between the two materials with regard to cumulative fluoride release within the 12 days of the experiment. However, no difference was observed between the fluoride release of the brushed samples compared to the unbrushed specimens. This was true for both, the cumulative fluoride release and its release on the day following brushing. It is assumed that regular brushing of the tested materials did not influence their release of fluoride and that brushing of polyacid-modified composite resins does not lead to maintaining their initially high level of fluoride release. Received: 6 May 1999 / Accepted: 21 July 1999     

Evaluation of weight loss and surface roughness of compomers after simulated toothbrushing abrasion test

This study aimed at analyzing the compomers wear by an "in vitro" toothbrushing abrasion test. The null hypotheses tested were that there would be no differences in weight loss and no significant changes in surface roughness of the compomers after this test. The utilized commercial brands were Dyract (Dentsply), Dyract AP (Dentsply), Compoglass F (Vivadent), Freedom (SDI), F2000 (3M ESPE), which were compared to the two resin composites Z100 (3M ESPE) and Silux Plus (3M ESPE). Ten cylindrical specimens for each commercial brand were prepared with 5mm diameter and 3mm thickness. An appropriate machine with soft bristle tips containing dentifrice solution and deionized water was used. A total of 100,000 brushing cycles were performed. The amount of weight loss was measured by the percentage alteration between the initial (before toothbrushing) and final weight (after toothbrushing), measured by a Sartorius analytical balance. The surface roughness change was determined by the percentage difference between initial and final means after 5 tracings by a T 1000 Hommel Tester roughness meter on the specimen's surfaces before and after toothbrushing abrasion test. The statistical analysis (Students paired t-test, ANOVA and Tukey, á=0.05) showed that all materials presented statistically significant weight loss and roughness increase after abrasion test. All compomers presented higher weight loss than resin composites. Freedom and Dyract AP presented the lowest weight loss among compomers. F2000 presented the worst abrasion resistance, without statistical differences with Dyract. For roughness changes, Dyract, Dyract AP, Z100, Compoglass F and Silux Plus showed the lowest surface roughness alteration, in increasing order, without statistical differences between them. Freedom was the statistically roughest material of the study.     

Effect of topical fluoride application on toothbrushing abrasion of resin composites.

OBJECTIVES: This in vitro study assesses toothbrushing abrasion of a microfill (Heliomolar Radioopaque) and a hybrid composite (Herculite XRV) after application of two acidic fluoride agents. METHODS: Thirty-six specimens of each resin composite were fabricated, ground flat and polished. Subsequently the 36 samples of each material were evenly assigned to three groups. In the first group, samples were treated with the fluoride varnish Bifluorid 12 (5.5% F, pH 5.6), in the second group with Elmex Fluid (1.25% F, pH 4.3). In the third group, specimens remained unfluoridated (controls). After 8h, the samples were subjected to toothbrushing abrasion (2000 brushing strokes, load: 250 g) in an abrasive slurry. Fluoridation and brushing abrasion were repeated twice. Afterwards, abrasion of the materials was quantitatively determined with a laser profilometer and statistically analyzed (ANOVA). RESULTS AND SIGNIFICANCE: With Herculite both, Bifluorid 12 (P = 0.0001) and Elmex Fluid (P = 0.0001) led to a significant increase of brushing abrasion compared to the non-fluoridated group. However, no significant difference was observed between the two fluoridation regimes. Heliomolar showed a tendency towards higher abrasion after treatment with Elmex Fluid compared to Bifluorid 12 (P = 0.0496) and the non-fluoridated group (P = 0.0496), whereas treatment with Bifluorid 12 yielded no significant difference compared to the non-fluoridated Heliomolar specimens. Fluoridation of Herculite resulted in a 106-121% increase of abrasion, whereas Heliomolar only showed an increase by 5-30%. Application of the acidic fluoride products used led to an increase in toothbrushing abrasion of the tested composite restorative materials. However, clinical long-term studies are needed to determine the effect of topical fluoride regimes on resin composite materials.     

Flexural Strength, Elastic Modulus, and pH Profile of Self-etch Resin Luting Cements

Purpose: To determine the flexural strength, modulus of elasticity, and 24‐hour pH profile of three self‐etching resin luting cements and to obtain comparative data for representative conventional resin and resin‐modified glass ionomer luting cements. Materials and Methods: Three self‐etching resin luting cements [RelyX Unicem (3M ESPE), Maxcem (Kerr), Embrace Wetbond (Pulpdent)] were tested and compared with two conventional resin cements [RelyX ARC (3M ESPE), Linkmax (GC)] plus two resin‐modified glass ionomer luting cements [Fuji Plus (GC), RelyX Luting Plus (3M ESPE)]. Flexural strength and modulus of elasticity were determined using bar‐shaped specimens (2 × 2 × 25 mm³) at 24 hours, using an Instron universal testing machine. Setting pH was measured using a flat‐surface pH electrode at 0, 2, 5, 15, and 30 minutes and 1, 2, 4, 6, and 24 hours after mixing. Testing was performed under both dual‐cured and self‐cured conditions for all dual‐cure cements. Data analysis included ANOVA and Tukey's test (p < 0.05). Results: The self‐etching cements showed similar flexural strength to the conventional resin cements, except for Embrace Wetbond self‐cured, which was considerably lower. Modulus of elasticity results were both higher and lower than for conventional resin cements. All photopolymerized conventional and self‐etch dual‐cure cements showed markedly higher flexural strength and modulus than when solely self‐cured. The resin‐modified glass ionomer cements were characterized by lower flexural strength and elastic modulus. Self‐etching resin cements showed lower initial pH (2.0 to 2.4) than conventional resin cements (4.8 to 5.2) and a wide range of final pH values (3.9 to 7.3) at 24 hours. One self‐etching cement (Unicem) revealed a unique pH profile characterized by a more rapid rise in pH to neutrality both when dual‐cured (15 minutes) and when auto‐cured (1 hour). Conclusions: The self‐etching resin cements evaluated in this study displayed disparate properties and cannot be considered a homogeneous group. Flexural strength properties were most uniform and were similar to those of the conventional resin cements, whereas moduli of elasticity showed greater variation. Setting pH profiles differed, depending on the brand and mode of cure, even within the same category of luting cement. All cements with dual‐cure capability, both conventional and self‐etch, showed significantly superior properties when photopolymerized.     

对四种粘接剂系统抗压强度及挠曲强度的评估

目的：对比研究4种粘接剂抗压强度及挠曲强度的差异.方法：选用树脂粘接剂Compolute,复合树脂Resinomer,树脂加强型玻璃离子Vitremer Luting及传统玻璃离子Ketac Cem4种粘接剂,分别制作抗压强度及挠曲强度的标准试件,每组10个.万能试验机测试其抗压强度及挠曲强度值,采用单因素方差分析及组间两两比较的LSD-t检验进行统计分析.结果：抗压强度组：Compolute为245.73±23.17MPa,Resinomer为153.50±18.59MPa,Vitremer Luting为61.89±10.92MPa,Ketac Cem为163.78±17.07 MPa.Ketac Cem和Resinomer组,其余各组组间两两比较差异均有统计学意义,P＜0.05.抗压强度由高到低的顺序为Compolute＞Ketac Cem＞Resinomer＞Vitremer Luting;挠曲强度组：Compolute为79.40±15.02MPa,Resinomer为102.18±19.61MPa,Vitremer Luting为20.70±3.89MPa,Ke切c Cem为21.04±4.02MPa.除后两组外,其余各组两两比较差异均有统计学意义,P ＜0.05.挠曲强度由高到低的顺序为Resinomer＞Compolute＞Ketac Cem＞Vitremer Luting.结论：与Vitremer Luting及Ketac Cem相比,Compolute表现较高的抗压强度及挠曲强度,Resinomer则具有较高的挠曲强度及较低的抗压强度,临床上可根据不同修复需求选择合适的粘接系统.     

Effect of chemical and mechanical degradation on surface roughness of three glass ionomers and a nanofilled resin composite

SUMMARY Nanofillers have been incorporated into glass ionomer (GI) restorative materials to improve their mechanical and surface properties. The aim of this present laboratory study was to compare the superficial roughness (Ra) of nanofilled GI (Ketac N100) with that of conventional GI (Fuji IX GP), resin-modified GI (Vitremer), and a nanofilled resin composite (Filtek Supreme) after pH cycling and toothbrush abrasion. Ten specimens of each material were made using Teflon molds, which were polished using aluminum-oxide abrasive disks. Three measurements of Ra were made of each specimen to serve as baseline values. The specimens were submitted to pH cycling for 10 days in a demineralization solution for six hours (pH 4.3) and were then stored in remineralization solution for 18 hours (pH 7.0). Ra measurements were recorded after the pH cycling. Specimens were then submitted to toothbrush abrasion in a brushing machine with a 200g load for 30,000 cycles at 250 cycles/min. The Ra values were then recorded. The surface morphology of specimens from each group was analyzed using a scanning electron microscope. Data were analyzed by analysis of variance, Tukey, and t-tests. After toothbrushing, only Fuji IX GP (1.10 ± 0.80) showed Ra values that were statistically different from those of the other materials evaluated. Ketac N100 (0.68 ± 0.16) showed intermediate Ra values, but it did not differ statistically from the results associated with Vitremer (1.04 ± 0.46) and Filtek (0.30 ± 0.15). Ketac N100 showed intermediate values of superficial roughness among the conventional glass ionomer cement, resin-modified glass ionomer cements, and the nanofilled resin after chemical and mechanical degradation.     

The shear bond strength between luting cements and zirconia ceramics after two pre-treatments

This study evaluated the shear-bond strength of 11 luting cements from different material classes to manufactured pre-treated zirconia ceramics (Lava: 97% ZrO2, stabilized with 3% Y2O3). In addition, the influence of the curing method on shear-bond strength was investigated. The cements examined were one zinc-phosphate cement (Fleck's zinc cement), two standard glass-ionomer cements (Fuji I, Ketac-Cem), three resin-modified glass-ionomer cements (Fuji Plus, Fuji Cem, RelyX Luting), four standard resin cements (RelyX ARC, Panavia F, Variolink II, Compolute) and one self-adhesive universal resin cement (RelyX Unicem). The ceramic surface was sand-blasted with 100-microm alumina or tribochemically coated with silica. After bonding procedure, one group was tested after 30 minutes (Time I), the other group was stored in distilled water at 37 degrees C for 14 days and subsequently thermocycled 1000 times (Time II). Statistical analysis was performed by multifactorial ANOVA models with interactions. For multiple pairwise comparisons, the Tukey method was used. After sandblasting, the highest shear-bond strength was obtained for the self-adhesive universal resin cement at 9.7 MPa (Time I) and 12.7 MPa (Time II), respectively. When using the Rocatec system, the highest values were found for one of the resin cements at 15.0 MPa (Time I) and for the self-adhesive universal resin cement at 19.9 MPa (Time II).     

Profilometric and microradiographic studies on the effects of toothpaste and acidic gel abrasivity on sound and demineralized bovine dental enamel

The objective of this study was to assess the abrasive effects of toothpastes and acidic F gels on sound and demineralized enamel. Pairs of enamel specimens were cut from bovine incisors, embedded in epoxy resin and polished. An artificial subsurface lesion of 80-90 microm depth was created in one specimen from each pair. The samples were covered with adhesive tape, thereby exposing the enamel for abrasivity testing. All samples were divided into six groups of 15 and brushed with a slurry (1:3) of F gel or toothpaste and human saliva. Brushing with water (control) or with slurry was carried out (16,000 strokes) using a medium toothbrush (load 275 g) mounted in a brushing machine. Abrasion was evaluated using laser profilometry, and was about 50% less on sound than on demineralized enamel (p < 0.001). In the latter, brushing with water (0.09 +/- 0.03 microm) or with fluoride-free gel (0.08 +/- 0.03 microm) resulted in negligible wear. With a medium-abrasive paste (1.76 +/- 0.85 microm) and an acidic F gel (2.48 +/- 0.72 microm), brushing abrasion was significantly greater (p < 0.001) than with a low-abrasive paste (0.84 +/- 0.38 microm). The greatest wear (16.6 +/- 10.8 microm) was observed with high-abrasive paste (p < 0.001), and here transversal microradiography revealed a complete loss of the pseudointact surface after brushing. In vitro formed caries-like lesions can be abraded (by toothbrushing) more easily than sound enamel; hence, initial white spot lesions should preferably be brushed with oral hygiene products of low abrasivity.     

The evaluation of bond strength of a composite and a compomer to white mineral trioxide aggregate with two different bonding systems

The purpose of this study was to evaluate the bond strength of a resin composite and a polyacid modified composite or "compomer" to white mineral trioxide aggregate (WMTA) with two different bonding systems (total-etch one bottle and self-etch one step). Forty specimens of WMTA were prepared and divided into four groups. In group one, Single Bond (3M/ESPE, St Paul, MN) and Z250 (3M/ESPE) were placed over WMTA. In group two, Prompt L-Pop (3M Dental Products, St Paul, MN) and Z250 were applied. In group three, Single Bond was applied with Dyract AP (Dentsply DeTrey, Konstanz, Germany), and, in group four, Prompt L-Pop was applied with Dyract AP. The shear bond strength was measured, and the fractured surfaces were examined. The results of the shear bond strength tests were analyzed by one-way analysis of variance test. The results of this study have suggested that the total-etch one-bottle adhesive system mediated a stronger bond to WMTA for both the resin composite and the compomer investigated. The placement of composite (Z250) and compomer materials (Dyract AP), used with total-etch one-bottle adhesive (Single Bond), over WMTA as final restoration may be appropriate.