Hardness and in vitro wear of a novel ceramic restorative cement

The aim of the present work was to compare a new ceramic restorative cement for posterior restorations, DoxaDent, with other types of tooth-colored materials for direct use as regards hardness and in vitro wear. Four hybrid resin composites, one polyacid-modified resin composite, one resin-modified glass ionomer cement, one conventional glass ionomer cement, one zinc phosphate cement, an experimental version as well as the marketed version of the ceramic restorative cement, were investigated. Hardness of the materials was tested with the Wallace indentation tester and wear was tested with the ACTA wear machine. All tests were carried out on 2-wk-old specimens. DoxaDent was as hard as the zinc phosphate cement and the hardest resin composite. The ceramic restorative cement wore significantly more than the resin composites, the same as the zinc phosphate cement, and less than the glass ionomer cements. No correlation between hardness and wear was found. It can be concluded that the ceramic restorative cement is a rather hard material but with a relatively low wear resistance.     

Thickness influence of veneering composites on fiber-reinforced systems

ObjectiveShort fiber reinforced composites (SFRC) require a veneering layer of conventional composite when used as restorations in the oral environment. The current study investigates the toughening effects during the path of a preexisting crack propagating through the bilayer system as it confronts the interface, through the attempted alignment of fibers and matrix-fiber interactions in the SFRC, and the distance it travels in the SFRC.MethodsBilayer systems of SFRC and conventional composite were produced with aligned fibers perpendicular to load direction. Single-edge-notched bend (SENB) specimens (25 × 5 × 2.5 mm³) with pre-crack length (a) to width (W) ratios (a/W = 0.2?0.8) were produced and tested in 3-point bending configuration until complete fracture. The specific work of fracture (w_e) was deduced from calculating the area under the load-displacement curves. Fiber alignment was digitally evaluated from images taken from the top and side planes of the specimen.ResultsThe toughness of the bilayer system is optimal when maximum SFRC thickness is used. EWF methods showed toughness and increasing nonessential work of fracture scaling with ligament length. A longer distance is accompanied by a higher distribution of aligned fibers bridging behind the crack wake, reducing crack driving forces at the crack tip.SignificanceSFRC materials provide increasing toughening potential with increasing thickness, and have the ability to be more anisotropic than other composite materials. Clinically, the layer must have a conventional composite cover layer, but which thickness does not affect toughness potential. Therefore the thickness of the conventional composite can be dictated by wear behavior.     

Difference in the color stability of direct and indirect resin composites

Indirect resin composites are generally regarded to have better color stability than direct resin composites since they possess higher conversion degree

Objective

The present study aimed at comparing the changes in color (∆E) and color coordinates (∆L, ∆a and ∆b) of one direct (Estelite Sigma: 16 shades) and 2 indirect resin composites (BelleGlass NG: 16 shades; Sinfony: 26 shades) after thermocycling.

Material and Methods

Resins were packed into a mold and light cured; post-curing was performed on indirect resins. Changes in color and color coordinates of 1-mm-thick specimens were determined after 5,000 cycles of thermocycling on a spectrophotometer.

Results

∆E values were in the range of 0.3 to 1.2 units for direct resins, and 0.3 to 1.5 units for indirect resins, which were clinically acceptable (∆E<3.3). Based on t-test, ∆E values were not significantly different by the type of resins (p>0.05), while ∆L, ∆a and ∆b values were significantly different by the type of resins (p<0.05). For indirect resins, ∆E values were influenced by the brand, shade group and shade designation based on three-way ANOVA (p<0.05).

Conclusion

Direct and indirect resin composites showed similar color stability after 5,000 cycles of thermocycling; however, their changes in the color coordinates were different.     

Clinical evaluation of the bond between composite resin and etched glass ionomer cement

One hundred and thirty-eight non-undercut Class V abrasion lesions were restored using glass ionomer cement overlaid by composite resin. Four techniques were used: enamel and glass ionomer acid-etched, enamel only acid-etched, ionomer only acid-etched, and neither enamel nor glass ionomer acid-etched. The restorations were examined after six months, one year and two years and evaluated for integrity and marginal staining, the latter employing a direct clinical method and a set of photographic standards. The relative failure of restorations at six months was maintained at subsequent time intervals, and at two years the failure incidence was 10, 35, 43 and 58 per cent for the above four techniques respectively. Marginal staining was most evident around those restorations for which only the glass ionomer had been etched. The results indicate that the retention of composite to etched glass ionomer is similar to that of composite to dentine using many dentine bonding agents. The several advantages of glass ionomers over dentine bonding agents are discussed.     

Incorporation of Apigenin and tt-Farnesol into dental composites to modulate the Streptococcus mutans virulence

ObjectivesThe aim of this in vitro study was to incorporate two anti-caries agents, Apigenin and tt-Farnesol, to resin composite and resin cement to reduce the virulence of Streptococcus mutans around dental restorations.MethodsApigenin (Api, 5 mM) and tt-Farnesol (Far, 5 mM) were added alone, together, and combined with fluoride (F). Biofilm of S. mutans was grown on composite discs, and the dry-weight, bacterial viability, and the polysaccharides (alkali-soluble, intracellular and water-soluble) were quantified. CLSM images of the S. mutans biofilm were obtained after three years of water-storage. The effect of the additions on the physicochemical properties and the composite colorimetric parameters were also analyzed.ResultsThe additions did not affect bacterial viability. Api alone and combined with Far or combined with Far and F decreased the bacterial dry-weight, alkali-soluble and intracellular polysaccharides. After three years, the composites containing the additions presented a greater EPS matrix on the top of biofilm. Statistical difference was obtained for the degree of conversion; however, the maximum polymerization rate and curing kinetics were unaffected by the additions. No difference was observed for the water-soluble polysaccharides, flexural strength, and elastic modulus. Api increased the yellowness of the composites.SignificanceApi, alone and combined, reduced the expression of virulence of S. mutans without jeopardizing the physicochemical properties of the composites.     

Porcelain thickness and cement shade effects on the colour and translucency of porcelain veneering materials

Objective

Purposes of this in vitro study include evaluating colour changes in combinations of feldspathic porcelain and cement resulting from different thicknesses of porcelain and different shades of composite luting agent, and evaluating relative translucency parameter (RTP) values.

Materials and methods

Porcelain discs of shade A1 at nominal thicknesses of 0.5 and 1.0 mm were bonded to cements of three shades in a factorial design. Colours were calculated for CIE D65 Illuminant and Standard Human Observer on black, grey and white backings. A colour difference (CD) was calculated of each possible pair of different porcelain thickness values for the same cement shade and each possible pair of different cement shades for the same porcelain thickness. RTP was analyzed by ANOVA and selected pairwise comparisons.

Results

All mean CDs studied were perceptible and most were at or greater than the clinical acceptability threshold, with the notable exception that the mean CDs and their confidence limits were below the clinical acceptability threshold for a change in porcelain thickness when utilizing the Clear cement shade. Variation in the shade of the resin luting cement will result in CDs which are near or beyond clinical acceptability. A decrease in porcelain thickness did significantly increase RTP when bonded to the resin cement shades studied.

Conclusion

Changes in porcelain thickness or cement shade may adversely affect basic aesthetic properties of these materials. Development of methods for analyzing aesthetic effects over greater ranges of thickness for these materials would improve the prognosis for using these materials.     

根管内屏障对根管治疗牙冠方微渗漏影响的体外研究

完整单根管前磨牙42颗,截去牙冠,常规根管治疗,随机分为4组,2%亚甲基蓝染色,2周后取出,制作透明样本,体视显微镜观察并测量样本微渗漏长度,并对数据进行统计学分析。结果显示阴性对照组未见染料渗入根管,阳性对照组见整个根管被染色(单因素方差分析,P<0.001),微渗漏长度的均数和置信区间由GP(4.80±0.54,4.42～5.19)、ZPC(3.39±0.65,2.92～3.85)、Filtek Z350(2.07±0.27,1.87～2.27)至Fiju VⅡ(1.68±0.15和1.57～1.79)呈递减趋势,两两比较,除Filtek Z350与F ijuVII间差异无统计学意义外(P>0.05),其余各组间差异均有统计学意义(P<0.05)。说明根管内屏障能够提高根管治疗牙冠方封闭能力;Filtek Z350、Fuji VⅡ可作为根管内屏障材料应用于临床。     

Effect of light curing modes on mechanical properties of direct and indirect composites

Abstract

Objective. To evaluate the degree of conversion (DC), flexural strength (FS) and Knoop microhardness (KHN) of direct and indirect composite resins polymerized with different curing systems. Materials and methods. Specimens of direct (Z250, 3M/Espe) and indirect (Sinfony, 3M/Espe) restorative materials were made and polymerized using two light curing units: XL2500 (3M/Espe) and Visio system (3M/Espe). Absorption spectra of both composites were obtained on a FTIR spectrometer in order to calculate the DC. FS was evaluated in a universal testing machine and surface microhardness was performed in a microhardness tester (50gf/15s). DC, FS and KHN data were submitted to two-way ANOVA and Tukey's test (α = 0.05). Results. Z250 showed higher DC, FS and KHN compared with Sinfony when the polymerization was carried out with XL2500 (p < 0.05). However, there is no statistical difference in DC between the materials when Visio was used (p > 0.05). Visio showed higher DC and KHN for Z250 and Sinfony than the values obtained using XL2500 light curing (p < 0.05). For FS, no significant difference between curing units was found (p > 0.05). Conclusion. Even though the Visio system could increase DC and KHN for some direct and indirect composites, compared with the conventional halogen curing unit, a high number of monomers did not undergo conversion during the polymerization.     

填料含量对双固化树脂水门汀性能影响的研究

目的：比较二氧化硅无机填料不同含量对树脂水门汀物理性能的影响。方法：在自行研制的双固化型树脂中加入二氧化硅无机填料,根据填料含量不同,分为56%、58%、60%、62%、64%5组,测定材料的挠曲强度、径向拉伸强度、压缩强度、表面硬度、吸水值与溶解值,观察二氧化硅无机填料含量对树脂水门汀物理性能的影响,应用方差分析和LSD检验进行统计分析（α=0.05）。结果：各含量组间挠曲强度、径向拉伸强度、压缩强度及表面硬度均存在显著性差异（P〈0.05）,而吸水值与溶解值各组间无显著性差异（P〉0.05）;二氧化硅无机填料含量在56%～64%范围内,随含量增加,挠曲强度、压缩强度、表面硬度均增大,而径向拉伸强度减小。结论：①.二氧化硅无机填料含量不同,对于EAM基树脂水门汀的挠曲强度、径向拉伸强度、压缩强度、表面硬度各项机械性能均有不同程度影响②.选择无机填料含量为62%～64%的复合树脂做为桩核材料物理性能较理想。     

Viscosity and thermal kinetics of 10 preheated restorative resin composites and effect of ultrasound energy on film thickness

ObjectiveThis study investigated viscosity and thermal kinetics of 10 selected preheated restorative resin composites and the effect of ultrasound energy on film thickness.MethodsA range of different resin composites was tested: Charisma Diamond, IPS Empress Direct, Enamel Plus HRi, Essentia, Estelite Omega, Filtek Z100, Filtek Z350 XT, Gradia, TPH Spectrum and VisCalor. A flowable resin composite (Opallis Flow) and two resin cements (RelyX Veneer, Variolink Esthetic LC) also were tested. Viscosity (Pa s) was measured at 37 °C and 69 °C (preheating temperature) using a rheometer. Film thickness (μm) was measured before and after application of ultrasound energy. Temperature loss within resin composite following preheating (°C/s) was monitored. Data were statistically analyzed (α = 0.05).ResultsViscosity at 69 °C was lower than at 37 °C for all materials except the flowable resin composite. Preheating reduced viscosity between 47% and 92% for the restorative resin composites, which were generally more viscous than the flowable materials. Film thickness varied largely among materials. All preheated resin composites had films thicker than 50 μm without ultrasound energy. Application of ultrasound reduced film thickness between 21% and 49%. Linear and nonlinear regressions did not identify any relationship between filler loading, viscosity, and/or film thickness. All materials showed quick temperature reduction following preheating, showing maximum temperature loss rates after approximately 10 s.SignificanceDistinct restorative resin composites react differently to preheating, affecting viscosity and film thickness. The overall performance of the preheating technique depends on proper material selection and use of ultrasound energy for reducing film thickness.     

复合树脂直接与间接修复后的牙体抗力实验研究

目的了解牙齿直接和间接用树脂修复后的牙体的抗力特性。方法40颗无龋前磨牙,制成MOD洞,然后分成4组,分别以Renew树脂直接充填,Renew直接嵌体修复,Tescera间接嵌体修复,制洞后不加修复。另以10颗完整前磨牙为对照。对上述所有牙齿采用力学模型静态力学加载实验,并进行对比分析研究。结果备洞未修复组牙齿的断裂载荷最小,与Renew树脂充填、Renew直接嵌体修复、Tescera间接嵌体修复及完整牙组有显著性差异(P<0.05);Renew树脂充填、Renew直接嵌体修复、Tescera间接嵌体修复和完整牙组之间抗断裂载荷无显著性差异(P>0.05)。在断裂模式上,Renew树脂充填组、Renew直接嵌体修复组和Tescera间接嵌体修复组分别出现9、3和1个样本树脂断裂。结论复合树脂充填和嵌体修复都能提高缺损牙齿的牙体抗力,复合树脂经过复合固化处理后力学性能有所提高。复合树脂不同固化处理对牙体抗力无明显影响。     

The effects of environment and cyclic fatigue on the mechanical properties of an indirect composite

Objectives

The purpose of this study was to examine the flexure strength (σ) and fracture toughness (K_IC) of three indirect dental composites (dentin, body, and incisal) with respect to loading (static and cyclic), testing environments (air and water) and ageing (0 (controls) and 6 months in air and water).

Methods

The specimens were 3 mm × 3 mm × 25 mm bars with the fracture toughness specimens having a 0.75 mm notch machined in the midspan. Static testing utilized 15 bars and cyclic testing 25 bars for each testing variable. All bars were tested using three-point loading and the cyclic testing was for 1000 cycles using a staircase approach.

Results

For flexure strength and fracture toughness, all specimen groups showed a decrease in mean values when exposed to cyclic loading as compared to the static loading mean and when exposed to ageing compared to the control specimens. ANOVA analysis demonstrated that dentin specimens had higher flexure strength and fracture toughness means than incisal and body specimens and that control and water specimens had higher flexure strength and fracture toughness means than aged and air specimens.

Conclusions

Degradation of these materials, as a result of cyclic loading and ageing in an aqueous environment, appears to be influenced by more than just the processing of the composite.     

Effect of different monomer-based composites and acid etching pre-treatment of enamel on the microleakage using self-etch adhesives systems

Objective. To evaluate quantitatively the marginal microleakage of restorations carried out with self-etching adhesives with or without prior phosphoric enamel acid etching of silorane or methacrylate resin-based composite restorations subjected to thermal cycling. Materials and methods. Forty cavities were prepared at the proximal surface of bovine incisors and randomly divided according to the etching of the enamel and restorative system used. The groups were restored with methacrylate [Adper SE Plus adhesive (3M ESPE) + Filtek Z250 (3M ESPE)] or silorane [Filtek LS adhesive (3M ESPE) + Filtek LS composite (3M ESPE)] restorative systems, light-cured using a LED unit (Bluephase 16i, Vivadent). After restorative procedure and thermocycling (1000 cycles), the specimens were immersed in methylene blue for 2 h. The specimens were triturated and the powder was used for analysis in an absorbance spectrophotometer. Data were statistically analyzed by 2-way ANOVA (alpha = 0.05). Results. No statistical difference between the restorative materials tested with or without previous acid etching of enamel in Class II marginal microleakage was observed (p > 0.05). Conclusions. The use of acid etching prior to self-etching adhesives did not interfere on the microleakage of methacrylate- or silorane-based restorations.     

Evaluating the effect of preheating on resin composites in pit-and-fissure caries treatments with a digital intraoral scanner

ObjectiveTo evaluate the effect of preheating on the microleakage and surface hardness of resin composites in the treatment of pit-and-fissure caries with various widths, as measured by an intraoral scanner.MethodsA total of 153 L-shaped cavities with different widths (1 mm, 1.6 mm and 2 mm) were prepared on the buccal or palatal/lingual surfaces of human molars. The cavities were measured in three dimensions by a TRIOS scanner and then filled with various resins (room temperature Z350 flowable resin and room temperature and 60 ℃ Z350 universal resin). Microleakage and gap formation at 2 sites were evaluated by stereomicroscopy and scanning electron microscope. Resin samples were prepared, and the top surface Vickers hardness (VHN_top) of all samples was measured at 1 day and 30 days postirradiation.ResultsNo difference were observed in the 3D scans for the cavities sizes among groups with the same width. For the 1 mm-wide cavity, the lowest microleakage was obtained with the flowable group; for the 1.6 mm-wide cavity, the nonpreheating universal group showed the highest microleakage at site 1, and the preheating group exhibited lower microleakage than that of the nonpreheating universal group at site 2; and for the 2 mm-wide cavity, the preheating group presented lower microleakage at site 2. The gap formations were consistent with the microleakage degrees. The preheating group exhibited the highest VHN_top at 1 day and 30 days postirradiation.SignificanceA digital intraoral scanner could be used to scan the cavities in three dimensions. Preheating technology could reduce the microleakage of Z350 universal resin and enhance its surface hardness.     

The influence of substance loss and ferrule height on the fracture resistance of endodontically treated premolars. An in vitro study

Objective

This study evaluated the effect of different ferrule heights and varying degrees of substance loss on the fracture resistance of endodontically treated premolars.

Methods

Eighty extracted and endodontically treated lower premolars were used and divided into 5 test groups (n = 16) depending on the ferrule height: A (0.0 mm), B (0.5 mm), C (1.0 mm), D (1.5 mm) and E (2.0 mm) respectively. Teeth in subgroups were either with 1 or 2 residual coronal dentin walls which were 3 mm in height and 1 mm in thickness. Teeth were restored with glass fiber posts and cast crowns. All specimens were then subjected to dynamic loading in a masticatory simulator for 1,200,000 loading cycles with a nominal load of 5 kg at 1.2 Hz combined with thermal cycling (5–55 °C, dwell time 30 s). Then specimens were quasi-statically loaded at 30° in a universal testing machine until fractured. Data were analyzed with 2-way ANOVA, followed by multiple comparisons using Tukey HSD test (α = .05).

Results

Mean (SD) failure loads for groups ranged from 679.5 ± 164.9 N to 1084.5 ± 269.9 N. Two-way ANOVA revealed that both the ferrule height and the number of residual coronal walls had a significant influence on the fracture resistance (P < .001 and P = .006, respectively). Significant increases were produced in the final fracture resistance, when the ferrule height was increased, which was reduced to approximately 37% when teeth with 2 mm ferrule height were compared with teeth without a ferrule.

Significance

Under the conditions of this in vitro study, increasing the number of residual coronal walls and ferrule height had a significant effect on the fracture resistance of endodontically treated premolars restored with prefabricated posts.     

The effect of root canal sealers and timing of cementation on the microlekage of the parapost luted with resin cement

Objectives

The objectives of the study were to study the effect of root canal sealers either eugenol or non-eugenol and timing of cementation on microleakage of the parapost luted with resin cement.

Materials and methods

Seventy extracted human, single-rooted teeth were instrumented using a crown-down technique. All teeth were instrumented up to a size 50 .04 taper ProFile followed by the use of Gates Glidden drills from size 2 up to 5. Following instrumentation, the teeth were randomly divided into four experimental groups of fifteen teeth each, based on type of root canal sealer (eugenol or non-eugenol sealer) and timing of post cementation (immediate or delayed). The remaining ten teeth were divided into two control groups with five teeth per group. All teeth were tested for microleakage using a fluid filtration method.

Results

The microleakage of the paraposts luted with resin cement increased over time, irrespective of sealer type or timing of post cementation. Immediate post cementation following obturation with AH26 (non-eugenol sealer) produced the least microleakage at all three time periods at 24 h, 2 months and 3 months.

Conclusions

The microleakage paraposts luted with resin cement was not influenced by either sealer type or timing of post placement. All experimental groups demonstrated a significant increase in microleakage over time as well as the presence of voids at the resin–dentin interface.     

硅烷化过程中不同加热温度对瓷和树脂粘接强度的影响

目的比较硅烷化过程中不同加热温度对瓷和树脂粘接强度的影响。方法选用2种不同类型硅烷偶联剂处理瓷表面,分别在20℃,40℃,60℃,80℃,100℃条件下干燥5m in。将经过表面处理的瓷试件与树脂粘接并测试剪切强度。结果20℃～60℃范围内,随加热温度的提高,瓷和树脂粘接强度上升;60℃～100℃范围内,随加热温度的提高,粘接强度下降。结论将硅烷化过程中加热温度提高至60℃左右时,硅烷偶联剂能够在瓷和树脂之间产生最佳粘接强度。     

Relationship between ceramic primer and ceramic surface pH on the bonding of dual-cure resin cement to ceramic

OBJECTIVES: This study examined the relationship between a ceramic primer and ceramic surface pH on the microtensile bond strength of dual-cure resin cement to ceramic. METHODS: Ceramic blocks (Vita Celay Blanks) were cut into multiple 3mm-thick slices and polished using 600-grit SiC paper. Two pairs were left untreated (controls), six pairs were treated with 40% phosphoric acid (PA), six pairs were treated with 20% hydrofluoric acid (HFA), and rinsed with water for either 15, 30 or 60 s. Half the specimens were silanated with Tokuso ceramics primer (TCP) (Tokuyama) and the other half with TCP formulated without phosphate monomer (TCP-NoPM). All the pairs were bonded with Bistite II dual-cure resin cement (Tokuyama) and light-cured. After 24 h water storage at 37 degrees C, the bonded specimens were cut into 6x0.7x0.7 mm(3) beams and their microtensile bond strengths (micro TBS) determined. Failure modes were determined using a confocal laser-scanning microscope. For scanning chemical analysis, the polished slices were cut into quarters, divided into seven groups of six, and treated in a similar manner as described for the micro TBS test. Surface pH was then determined using a scanning chemical microscope. For SEM examination, one ceramic quarter from each of the seven groups was used. RESULTS: Three-way ANOVA revealed that the micro TBS of TCP was significantly higher than TCP-NoPM with no acidic treatment (p<0.05). However, after treatment of the ceramic surface with either PA or HFA, and 15 s rinsing, there was a significant reduction in surface pH (p<0.05), and no significant difference in micro TBS between TCP and TCP-NoPM (p>0.05). For TCP, there were no significant differences in micro TBS and failure mode between the control, PA, and HFA treated groups when the water rinsing time was increased. Whereas, for TCP-NoPM and surface treatment with PA, an increase in rinsing time resulted in a significant reduction in micro TBS and a significant increase in surface pH (p<0.05). SIGNIFICANCE: Acidic treatment of the ceramic surface did not significantly increase dual-cure resin/ceramic bond strengths when the ceramic primer, TCP, was used. It is suggested that when no phosphate monomer is present in a ceramic primer, dual-cure resin cement/ceramic bond strength is dependent upon the concentration of H(+) ions on the ceramic surface.     

The influence of resin composite and bonded amalgam restorations on dentine permeability in Class II cavities in vitro

OBJECTIVES: This study was conducted to measure and compare dentine permeability reduction in Class II preparations, after restoration with resin composite or bonded amalgam, using either a multi-step or one-bottle dental adhesive system. METHODS: An in vitro fluid transport model was used to measure initial dentine permeability in Class II cavities with an intact smear layer in crown segments from extracted human premolars. One week and 3 months after restoration with resin composite or bonded amalgam, using either multi-step or one-bottle dental adhesive system, the measurements were repeated and the reduction in permeability was calculated as a percentage of the initial values. The data were analyzed statistically using a one-way ANOVA and Least Significant Difference tests. RESULTS: After 1 week the resin composite with one-bottle dental adhesive system provided the highest reduction in dentine permeability, whereas after 3 months the bonded amalgam caused the highest reduction. At both time intervals the resin composite with multi-step adhesive system provided the lowest reduction. (P=0.036 at 1 week, P=0.016 at 3 months). After 3-months storage in water a significant increase in dentine permeability reduction was found in the bonded amalgam group only (P=0.017). The reduction in dentine permeability provided by resin composite with one-bottle dental adhesive system and bonded amalgam in Class II cavities was similar at both time intervals. (P=0.182 at 1 week, P=0.750 at 3 months). SIGNIFICANCE: The results of this study indicated that on the basis of reducing dentine permeability in vitro, resin composite restorations with the investigated one-bottle adhesive system was superior to its multi-step equivalent and bonded amalgam can also be preferred in Class II restorations.