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Water sorption in bis (GMA)/TEGDM resin
Abstract
Some water sorption-desorption properties of a heat-cured copolymer of bisphenol-A-glycidyl methacrylate/triethylene-glycol-dimethacrylate [bis(GMA)/TEGDMA] were investigated during three sequential water sorption-desorption cycles at 60, 37, and 60 degrees C. The results showed that the investigated polymer absorbed almost one molecule of water for each bis(GMA)/TEGDMA molecule, causing a volumetric expansion slightly smaller than the volume of the absorbed water. The determined mean value of the sorption and desorption diffusion coefficients for a specific cycle, here named the "true" diffusion coefficient, was about 1.5 X 10(-8)cm2s-1 at 60 degrees C, decreasing to one-third of that value at 37 degrees C. Although there were differences in leaching between the two sorption-desorption cycles at 60 degrees C, no differences in true diffusion coefficients were found during the two cycles at that temperature. However, the sorption process proceeded slower than the desorption process during the first cycle, while the opposite occurred during the second cycle. These variations could be an effect of leaching occurring during the first cycle at 60 degrees C and also the effects of induced swelling stresses on the diffusion process.
... Workers have generally selected similar dimensions; 0.8-1.3 mm thickness x 20 mm diameter (Braden et al. 1976), 1 mm x 15 mm (Pearson 1979), 0.8 mm x 21 mm (Soderholm 1984), 1 mm x 20 mm , 1 mm x 14 mm (Kalachandra 1989) and 1 mm x 15 mm (Kildal and Ruyter 1997;Tanoue et al. 1998C). Clinically, the time taken for all the regions in the composite restoration to be permeated by water, will be more complex, since this is affected by temperature, shape and the varying thickness of the restoration. ...
... Water sorption is reported to provide some benefit in reducing stresses caused by the setting contraction of the composite (Asmussen and Jorgensen 1972). Swelling may further compensate for gaps found around the composite restoration as a result of polymerisation of the resin cement lute, thus contributing to reduced marginal leakage (Soderholm 1984). ...
... Sorption of water has also been reported to breakdown the coupling agent and bond between the coupling agent and the filler, with consequent debonding o f the filler particles from the resin matrix and, over longer periods of water immersion, there appears to be a loss of inorganic ions due to an attack of water on the fillers. This may explain why these restorations have poor wear and abrasion resistance (Craig 1980;Soderholm 1984;Oysaed and Ruyter 1986). ...
Composite resins, while popular on aesthetic grounds, have shown a number of problems including wear, shrinkage and long term degradation. Extra-oral polymerisation has been proposed as a means of reducing bulk polymerisation shrinkage whilst enhancing mechanical properties. However, there still exists a problem with shrinkage associated with the resin cement lute. There are problems obtaining measurement of the cement lute thickness, particularly over the whole fit surface of the restoration. The observed discrepancies between the cavity surface and the fit of the inlay are variable. This study investigates some physical properties of three inlay systems, and attempts to determine the effect of cavity configuration on the dimensional change of the inlay during polymerisation. The physical properties evaluated were flexural strength and hardness to confirm the effect of extra oral polymerisation on the composite. The water sorption and solubility were also determined. Linear shrinkage was measured in different dimensions to determine the effect of the constraining influence of a mould. The apparent cement lute thickness of the inlays in a stylized cavity was assessed using a laser scanning profilometer. An addition silicone impression rubber of similar viscosity to resin cement was used as the luting medium. The greatest shrinkage occurred in width rather than length. Highest values for shrinkage were observed in the system polymerised by heat and pressure. A high solubility value for the heat and light polymerising system (0.53%) was recorded which also showed the lowest water sorption (0.92%). The heat and pressure system had similar solubility values (0.51%), but high water sorption (1.54%). The flexural strength was found to decrease in all samples over a period of 6 months in aqueous solution, the greatest reduction occurring in the laboratory heat and light system. Surface hardness also decreased after 6 months immersion in water. In all cases substantial cement lute thickness was observed and this varied with the cavity configuration. The effect of cavity design on these materials is not clear.
... 39 However, the effect of the enamel preparation and the etching protocol on the bond strength still appears controversial, with studies showing lower bond strengths for intact enamel than for prepared enamel when using a self-etching primer 40 and studies reporting no differences between unprepared and prepared enamel, irrespective of the etching system. [41][42][43] Laboratory studies evaluating the bond strength to enamel should aim to simulate clinical conditions by conducting artificial aging, [44][45][46][47] but most studies reported bond strength values only 24 hours or 3 days after bonding. ...
... Adequate artificial aging should ensure complete water saturation of the bonding interfaces for months. [44][45][46][47] The type of failure observed in this study was predominantly cohesive within the luting composite resin for unprepared and minimally invasively prepared enamel. This contradicts the results of another study 39 where the failure mode was predominantly adhesive, irrespective of the enamel treatments and adhesives. ...
... Owing to an uneven water distribution, that surface swelling will be restrained by the centrally unswollen part. Because o f this restraint, the polymer is stressed since its surface will be in compression while the centre in tension (Soderholm 1984b). As time passes diluent resins and monomer components are being released from the resin opening up spaces for more water to diffuse in. ...
... In the oral environment the time to reach equilibrium could be substantially longer where thick facings are present. During function, the diffusion of water is slowed down when the polymer is in compression, while it is speeded up when the polymer is in tension (Soderholm 1984b). Therefore intraoral loading and the variable dimensions of the facings can frequently lead to variation in the fluid uptake and temporary internal stresses may be set up within the material. ...
This study investigated the behaviour of metal/resin laminates of dimethacrylate resins and cobalt chromium alloy (Co/Cr) when subjected to fatigue stressing by thermo-cycling and cyclical loading, after water storage. The veneering materials used were a microfine (Silux Plus) and a hybrid (Z100) composite, bonded to a Co/Cr alloy through an adhesive interface (Cesead opaque primer and body opaque resin). Characterisation of the two composite resins was carried out with particular attention to water sorption. Laminates were evaluated over a period up to six months, groups of ten specimens were load cycled alone (Ld) (up to 453,600 cycles at 5 Hz), thermo-cycled alone (Th) (up to 25,200 cycles between 4°C, 37°C and 60°C) load cycled and thermo-cycled (Ld/Th) (cycled as above). Following testing, laminates were assessed for their elastic modulus, examined microscopically and the adhesive interface was subjected to a dye penetration study. The microfine resin absorbed more water than the hybrid (2.88% and 1.84% by mass respectively) and lost more soluble material (0.61%, 0.19% of original mass respectively). The laminates of the different veneering resins exhibited differences in their elastic behaviour. The apparent flexural modulus of laminates made with the hybrid resin (initial: 482.3 ± 69.1 GPa, week 24 Ld/Th; 544.7 ± 70.3 GPa) was higher than those made with the microfine resin (initial: 288.1 ± 44.4 GPa, week 24 Ld/Th; 353.7 ± 47.5 GPa). The extension at failure of the hybrid resin laminates appeared to be lower than that of the microfine ones. However, little difference was seen in the stress at failure between groups. Week 24 Ld/Th; (Z100: 833.3 ± 355.8 MPa, Silux Plus: 828.4 ± 122.1 MPa). Both cohesive failure within the veneering resin and adhesive failures between the veneering resin and metal component were noted.
... Adequate artificial aging should provide complete water saturation to the bonded interfaces over months. [37][38][39][40] Thermocycling with prolonged water storage is a common method of imitating thermal stress and water absorption at the bonding interface in an attempt to replicate clinical conditions in vitro. 25,41 To simulate the effect of water absorption, a storage period of 150 days was chosen because the storage period can influence the bond strength to dentin. ...
... 22 In the present study, however, no statistically significant decrease of tensile bond strength was found, which is contrary to some other studies that reported a decrease after thermocycling and artificial aging. 40,42 However, no decrease in tensile bond strength after thermocycling has been reported also in other studies. 13,15,29 One reason for the lack of bond strength reduction could be the improved integration of the smear layer, resulting in a more stable hybrid layer. ...
Statement of problem
The durability of adhesive bonding systems to dentin is of importance for restoration longevity; therefore, new adhesive systems should be tested in vitro with long-term artificial aging before clinical application.
Purpose
The purpose of this in vitro study was to investigate the bonding durability of 3 dual-polymerizing resins and 1 autopolymerizing resin to human dentin with their specific self-etching primers or adhesives.
Material and methods
Acrylic resin tubes filled with composite resin were bonded to human dentin disks using either an autopolymerizing resin system (Panavia 21) or dual-polymerizing resin systems (Panavia V5, RelyX Ultimate, and Variolink Esthetic DC) together with the system-specific primer or adhesive. Tensile bond strength was tested after 3 days of water storage or after 150 days of water storage with 37 500 thermocycles (5 °C to 55 °C). The failure mode was evaluated by using a light microscope. In addition, representative specimens were examined by using a scanning electron microscope.
Results
After 3 days, the median tensile bond strengths ranged from 18.8 to 29.1 MPa. After artificial aging for 150 days, the median tensile bond strengths ranged from 14.7 to 25.6 MPa. The dual-polymerizing resins showed significantly higher bond strength than the autopolymerizing resin (P≤.05). Artificial aging with thermocycling had no statistically significant influence on tensile bond strength for the adhesive resin systems tested (P>.05). The failure mode was mainly adhesive for the autopolymerizing resin, whereas it was mainly cohesive for the dual-polymerizing resins.
Conclusions
The 3 tested dual-polymerization resin systems provided durable bond strengths to dentin which were higher than those of the autopolymerizing resin.
... 6,7 It has been known for sometime that dental composites are prone to degradation due to hydrolysis. [8][9][10] Food simulants, also, affect the surface microhardness and wear characteristics of dental composites. 11 The diffusion of moisture through the resin may also lead to the initiation and propagation of micro cracks at the interface and in the resin. ...
... 5 The diffusivity of the ethanol solution in dental composite specimens is greater than that of water. 8,44 There was a non-significant difference in the site of bond failure for specimens immersed in each storage medium for the 1 day storage period, so that most of the specimens showed adhesive failure at the bracket baseadhesive interface (score 1). Specimens stored for 30 days also showed non-significant difference, where score 1 and 2 prevailed and score 3 and 4 where only scarcely found. ...
This investigation was performed to study the effects of aqueous foods, alcoholic foods and fatty foods as represented by dietary simulating liquids (distilled water, corn oil, 8% and 50% aqueous ethanol) and their different exposure times upon the shear bond strength of orthodontic adhesive bonding material and on the type of failure of orthodontic adhesive bonding material. Metal brackets were bonded to 128 extracted human premolars and were randomly divided into four equal groups each with 32 teeth, representing the storage media, which were distilled water (control), 50% aqueous ethanol (alcoholic food), 8% aqueous ethanol (aqueous food) and corn oil (fatty food). Then each group was subdivided into two subgroups with 16 teeth each, representing two storage periods (1 day and 30 days). At the end of the storage period in the immersion media the brackets were debonded by an Instron universal testing machine to measure the shear bond strength. After debonding each bracket base and the corresponding tooth surface were examined by a stereomicroscope and the Adhesive Remnant Index scores were recorded. Results showed that immersion in the food simulants for 30 days significantly reduces the bond strength of no-mix orthodontic adhesive specially ethanol (27.69% for 50% ethanol, 10.06% for 8% ethanol and 6.51% for corn oil), and only 50% ethanol showed a statistically significant effect on the site of bond failure to produced more cohesive failures. In conclusion, food and rinses containing ethanol may be a causative factor in bond failure.
... These results are in accordance with literature, indicating an aging effect caused by water storage and TC, respectively [28][29][30][31][32]. This effect might be explained by the water uptake of the t-c&bs, acting as a plasticizer [15]. ...
... This effect might be explained by the water uptake of the t-c&bs, acting as a plasticizer [15]. Furthermore, certain degradation phenomena on a molecular level between filler and matrix might have played a role in case of Luxatemp AM Plus [29,30,33,34], although not obvious in the SEM micrographs. ...
This study aimed at investigating the influence of fabrication method, storage condition and material on the fracture strength of temporary 3-unit fixed partial dentures (FPDs).
A CrCo-alloy master model with a 3-unit FPD (abutment teeth 25 and 27) was manufactured. The master model was scanned and the data set transferred to a CAD/CAM unit (Cercon Brain Expert, Degudent, Hanau, Germany). Temporary 3-unit bridges were produced either by milling from pre-fabricated blanks (Trim, Luxatemp AM Plus, Cercon Base PMMA) or by direct fabrication (Trim, Luxatemp AM Plus). 10 FPDs per experimental group were subjected either to water storage at 37 °C for 24h and 3 months, respectively, or thermocycled (TC, 5000×, 5-55 °C, 1 week). Maximum force at fracture (Fmax) was determined in a 3-point bending test at 200 mm/min. Data was analyzed using parametric statistics (α = 5%).
Fmax values ranged from 138.5 to 1115.5N. FPDs, which were CAD/CAM fabricated, showed a significant higher Fmax compared to the directly fabricated bridges (p < 0.05). TC significantly affected Fmax for Luxatemp (p < 0.05) but not for the PMMA based materials (p > 0.05). CAD/CAM milled FPDs made of Luxatemp showed significantly higher Fmax values compared to Trim and Cercon Base PMMA (p < 0.05).
CAD/CAM fabricated FPDs exhibit a higher mechanical strength compared to directly fabricated FPDs, when manufactured of the same material. Composite based materials seem to offer clear advantages versus PMMA based materials and should, therefore, be considered for CAD/CAM fabricated temporary restorations.
... Moreover, EPR has previously been used to follow free radical fading in order to determine the diffusion coefficient of oxygen in the bulk of polymers [10]. In addition to oxygen, other substances of the oral environment , such as water [11] [12] or saliva [13] [14], can also interact with the organic matrix, which could have an impact on free radical decay. For example, saliva can cause damage through the reaction of enzymes with compounds of the organic matrix. ...
... For example, saliva can cause damage through the reaction of enzymes with compounds of the organic matrix. The rate of these various reactions increases with temperature [2] [12] [15], and is thus another parameter that needs to be taken into account. In this work, the effect of different storage conditions on free radical kinetics of decrease was studied: two different temperatures , 25 °C (ambient) and 37 °C, and four environments (water, argon, air and oxygen) were investigated. ...
In this work, we used electron paramagnetic resonance to follow the decrease kinetics of free radicals trapped in an experimental resin (ER) and in a commercial composite (Charisma (Ch)) stored under different conditions (in air at 25 and 37 degrees C; in argon, oxygen and water at 25 degrees C). During the first day, the decay was fast (0-24h-rate of decay of allylic radical: 1700-1000a.u. for Ch, 1700-1500a.u. for ER) and the storage conditions had no influence on the kinetics. This phase was ascribed to a post-polymerization phenomenon. From 1day to 1month, the rate of decay depended on the storage environment. In argon, free radicals were quite stable (1day to 1month-rate of decay of allylic radical: 1200-1000a.u. for Ch, 1400-1200a.u. for ER). For the other storage environments, in ER, the rate of decay was higher in water than in oxygen and in air (1day to 1month-rate of decay of allyl radical: 1400a.u. to 100, 500 and 800a.u., respectively). In Ch, free radicals faded quicker than in ER, as undetectable levels were reached before 1month, which attests to the influence of fillers on radical decrease kinetics. Heating experiments were also performed, and free radical concentrations decreased faster at higher temperatures, especially above the glass transition temperature. In conclusion, ambient oxygen is mainly involved in the termination process of free radicals. Therefore, conditions influencing oxygen diffusion have an impact on radical kinetics as well.
... Imazto et al. [27] found that the diffusion coefficient in the polymer made of BisGMA and TEGDMA alone was found to be 1.71 × 10 −12 m 2 /s, corresponding to 68% degree of conversion, while He et al. [28] reported it to be 0.75 × 10 −12 m 2 /s for 85% degree of conversion (with 5% water sorption). For the parent polymer, the experimental diffusion coefficient was reported to be 1.6 to 1.7 × 10 −12 m 2 /s (with different degrees of conversion, temperature, water sorption capacity) [27][28][29]. The diffusion coefficient obtained for MAPOSS resin in this study is closer to this range though the conversion used in the current study is 100% and for a relative humidity of 100%. ...
Methacrylate-based polyhedral oligomeric silsesquioxane (POSS) is one of the new composites used as a dental resin. Both monofunctional methacryl isobutyl POSS (MIPOSS) and multifunctional methacryl POSS (MAPOSS) are reported to be possible resins that possess the desired properties for using them as dental resins. Our group's previous comparative study on these two resins showed that the MAPOSS composite has superior mechanical properties compared with the MIPOSS composite. In this article, molecular dynamic simulations (MD simulations) are performed to study the water sorption in these two composites. Water sorption in dental composites can have several effects on the material properties, performance, and longevity of dental restorations. Water sorption in MAPOSS and MIPOSS composites is analyzed by studying the hydrogen bonding, cluster analysis, density projection calculations, and diffusion coefficient calculation of water molecules within the resin matrix. MD simulations results are further used to understand the interaction of water molecules with the resin matrix comprehensively, which governs the composite's mechanical properties. The water sorption study showed that the MAPOSS composite has less water sorption capacity than the MIPOSS composite. The practical significance of this study is to find properties that affect dental restoration and longevity, which can help in the design of better materials for dental applications.
... Water storage affects the flexural properties of composite materials, slowly penetrating into the structure of the resin composite. Longer storage times in water may cause greater changes in properties [34,35]. The rate and amount of water absorption depend on the resin composition [33]. ...
(1) The interactions in the oral cavity between resin composite blocks for CAD/CAM application and saliva, biofilm, and chemicals and their influence on mechanical properties are still mostly unknown. The purpose of this study is to examine the impact of artificial aging on the flexural strength, flexural modulus, hardness, Weibull modulus, and probability of failure of six resin composite CAD/CAM materials. (2) The aging was conducted by storing the specimens in water at 37 ◦C for 3 months, then a 3-point bending test was applied and measured. The microhardness was measured with a Vickers microhardness tester. Weibull analysis (according to ISO) was also performed. The shape and scale parameters were calculated. (3) After aging, the flexural strength values ranged from 95.51 (SD 9.07) MPa for the aged Shofu Block HC (HC) to 160.28 (SD 10.37) MPa for non-aged Gandio blocks (GR), and the flexural modulus values ranged from 7.75 (SD 0.19) GPa for HC to 16.77 (SD 0.60) GPa for GR. The microhardness (HV01) ranged from 72.71 (SD 1.43) for the Katana Avencia Block (AV) to 140.50 (SD 5.51) for GR. After aging, the Weibull characteristic strength ranged from 99.47 MPa for HC to 169.25 MPA for Brilliant Crios (CR). (4) Water storage led to a decrease in flexural strength and characteristic strength and slightly affected the flexural modulus. Gandio Blocks, Tetric CAD, and Brilliant Crios presented higher flexural strength than others.
... Both Bis-GMA and urethane dimethacrylate (UDMA) have high viscosity; hence, TEGDMA needs to be frequently added as a diluent material. TEGDMA consists of ethylene glycol as the main chain and is, therefore, highly flexible and water absorbable [26][27][28] . On the other hand, although UDMA is a hydrophobic monomer, it has a hydrophilic isocyanate group. ...
In this study, we evaluated the characteristics of five commercial resin composites used for provisional restorations. The inorganic filler contents of the resins were measured, and three-point bending, wear, surface hardness, water absorption, and staining tests were performed. The specimens underwent additional three-point bending tests after water storage and undergoing thermal stresses at 5°C and 55°C (10,000 cycles). Data were analyzed using one- or two-way analysis of variance and Bonferroni post-hoc tests. Pearson’s correlation coefficient was used for pairwise comparisons. Each resin composite presented with different mechanical properties, based on variations in the inorganic filler content. The flexural strength of each resin composite was significantly decreased after water storage. There has a positive correlation between flexural strength and dynamic hardness but a negative correlation between flexural strength and maximum wear depth. The types and contents of the inorganic fillers, the composition of the monomer in the resin matrix, and the addition of plasticizers can affect the properties of the material.
... The diffusivity of the ethanol solution in dental composite specimens is greater than that of water in dental composites. (26,27) The solubility parameter describes the ease with which a molecule will penetrate and dissolve within another substance, and the solubility parameter of ethanol is closer to that for the dental composite 3x104 J 1/2 /m 3/2 , while the solubility parameter of water is about 4.8x104 J 1/2 /m 3/2 this value has been shown to fall beyond the solubility parameter ranges for Bis-GMA based composite and thus has little influence on matrix softening, while ethanol has greater permeability. (24) The results further confirmed earlier results by Lee et al, (3,28,29) they suggested that the materials were not very susceptible to chemical breakdown by artificial saliva which contains 90-95% water for up to 30 days of immersion, but a significant decrease in shear bond strength was noticed after exposure to 75% ethanol. ...
The effect of food simulants on the bond strength of orthodontic metal brackets bonded to enamel with light cured composite was studied. One hundred twenty extracted human premolars were selected and randomly divided into three equal groups each with 40 teeth, representing the adhesive bonding generation (5th, 6th and 7th). Each group was subdivided in to two subgroups which represented the storage media, which are distilled water (DW) and 75% aqueous ethanol (Food simulating solution-FSS). Then the storage media group was subdivided into two subgroups with 10 teeth each, representing two storage periods (1 day and 30 days). At the end of the storage period in the immersion media the brackets were debonded by an Instron universal testing machine to measure the shear bond strength. It was found immersion in the food simulants for 30 days significantly reduces the bond strength of light cured composite brackets.
... [10] Concurrently, water is diffused in to the polymer matrix of composites, swells the polymer, and fills the space between the main chains and crosslinks, as well as occupying the microvoids created during the polymerization phenomenon. [20] Time or aging is expected to be a significant factor associated with the amount of water sorption; moreover, composites which absorb more water, will show more decreased surface microhardness. The present study confirmed the latter clarification. ...
Background and aims. Bleaching may exert some negative effects on existing composite resin restorations. The aim of this study was to evaluate the effect of home bleaching on microleakage of fiber-reinforced and particle-filled composite resins.
Materials and methods. Ninety class V cavities (1.5×2×3 mm) were prepared on the buccal surfaces of 90 bovine teeth. The teeth were randomly divided into 6 groups (n=15) and restored as follows: Groups 1 and 2 with Z100, groups 3 and 4 with Z250, and groups 5 and 6 with Nulite F composite resins. All the specimens were thermocycled. Groups 1, 3 and 5 were selected as control groups (without bleaching) and the experimental groups 2, 4 and 6 were bleached with 22% carbamide peroxide gel. All the samples were immersed in 2% basic fuchsin dye for 24 hours and then sectioned longitudinally. Dye penetration was evaluated under a stereomicroscope (×25), at both the gingival and incisal margins. Data were analyzed using Kruskal-Wallis, Mann-Whitney and Wilcoxon tests (a=0.05).
Results. Statistical analyses revealed that bleaching gel increased microleakage only at gingival margins with Z250 (P=0.007). Moreover, the control groups showed a statistically significant difference in microleakage at their gingival margins. Nulite F had the maximum microleakage while Z250 showed the minimum (P=0.006).
Conclusion. Microleakage of home-bleached restorations might be related to the type of composite resin used.
Keywords: Bleaching, composite resin, fiber-reinforced, filler, microleakage
... This accumulated water might interact with the monomer through hydrogen bond, allowing for further accumulation of water molecules inside the polymer. Moreover, resin composites that contained Bis-GMA/TEGDMA co-polymers have up to 3.3% increase in volume due to hygroscopic expansion [45]. Boaro et al. [46] has shown that the same Filtek Supreme resin composite has a high sorption rate compared to seven other resin composite materials, and silorane-based resin composite (a monomer that contains siloxane and oxirane) had a low sorption rate. ...
Purpose
To determine the effect of aging methods on the fracture toughness of a conventional Bis-GMA-based resin composite (Filtek Supreme), an ormocer-based resin composite (Admira), and an experimental hydrophobic oxirane/acrylate interpenetrating network resin system (OASys)-based composite.
Methods
A 25 × 5 × 2.8-mm stainless-steel mold with 2.5 mm single-edge center notch, following ASTM standards [E399-90], was used to fabricate 135 specimens (n = 15) of the composite materials and randomly distributed into groups. For the baseline group, specimens were fabricated and then tested after 24-h storage in water. For the biofilm challenge, specimens were randomly placed in a six-well tissue culture plate and kept at 37 °C with bacterial growth media (Brain Heart Infusion (BHI); Streptococcus mutans) changed daily for 15 days. For the water storage challenge, specimens were kept in 5 ml of deionized distilled autoclaved water for 30 days at 37 °C. μCT evaluation by scanning the specimens was performed before and after the proposed challenge. Fracture toughness (KIc) testing was carried out following the challenges.
Results
μCT surface area and volume analyses showed no significant changes regardless of the materials tested or the challenge. Filtek and Admira fracture toughness was significantly lower after the biofilm and water storage challenges. OASys mean fracture toughness values after water aging were significantly higher than that of baseline. Toughness values for OASys composites after biofilm aging were not statistically different when compared to either water or baseline values.
Conclusion
The fracture toughness of Bis-GMA and ormocer-based dental resin composites significantly decreased under water and bacterial biofilm assault. However, such degradation in fracture toughness was not visible in OASys-based composites.
Clinical significance
Current commercial dental composites are affected by the oral environment, which might contribute to the long-term performance of these materials.
... Absorbed water causes sorption expansion, increasing the effective free volume and the ease of movement of chain segments, thus reducing the elastic modulus of the material (173). Most of the water molecules occupy free volume between the chains and crosslinks as microvoids are created during polymerization (174). Water is considered as a poor solvent for the resin, and therefore exerts a more limited effect compared to other solvents (117). ...
Tübingen, Univ., Diss., 2005 (Nicht für den Austausch).
... In order to test the hydrolytic durability of bonding systems, adequate artificial aging should provide full water saturation of the bonded specimens, which may take several months of immersion in water. 2,7,13,29,41 When bonding to lithium disilicate, group S-MPV (Monobond Plus/Variolink Esthetic) showed the highest initial TBS (45.0 MPa) of all groups; although the bond strength decreased during aging, it was still acceptable after 150 days (25.4 MPa). Monobond Plus contains silane, which can ex- plain the high TBS. ...
Purpose:
To test the bond strength and durability after artificial aging of so-called universal primers and universal multimode adhesives to lithium disilicate or zirconia ceramics.
Materials and methods:
A total of 240 ceramic plates, divided into two groups, were produced and conditioned: 120 acid-etched lithium disilicate plates (IPS e.max CAD) and 120 air-abraded zirconia plates (Zenostar T). Each group was divided into five subgroups (n = 24), and a universal restorative primer or multimode universal adhesive was used for each subgroup to bond plexiglas tubes filled with a composite resin to the ceramic plate. The specimens were stored in water at 37°C for 3 days without thermal cycling, or for 30 or 150 days with 7500 or 37,500 thermal cycles between 5°C and 55°C, respectively. All specimens then underwent tensile bond strength testing.
Results:
Initially, all bonding systems exhibited high TBS, but some showed a significant reduction after 30 and 150 days of storage. After 3, 30, and 150 days, Monobond Plus, which contains silane and phosphate monomer, showed significantly higher bond strengths than the other universal primer and adhesive systems.
Conclusions:
The bond strength to lithium disilicate and zirconia ceramic is significantly affected by the bonding system used. Using a separate primer containg silane and phosphate monomer provides more durable bonding than do silanes incorporated in universal multimode adhesives. Only one of five so-called universal primers and adhesives provided durable bonding to lithium disilicate and zirconia ceramic.
... A rigid cross-linked network produced by bis-GMA (1.43 GPa) absorbs less water than TEGD-MA does, but more water than UDMA does. TEGDMA is a hydrophilic monomer, that absorbs great amount of water (20,28). ...
Background
The aim of this study was to analyze the bond strength of aged resin based nanocomposites repaired with the same and bulk fill composites.
Material and Methods
Seventy-two disc shaped resin composites consisted of three different nanocomposite resins (Filtek Ultimate/FU, Herculite XRV Ultra/HXRV, and Reflectys/R) were produced. After storing the samples for 8 weeks in distilled water, each material was combined with the same material or the bulk-fill composite resin system (Filtek Ultimate+Filtek Ultimate/Group-1; Filtek Ultimate+Tetric BF/Group-2; Herculite XRV+Herculite XRV/Group-3; Herculite XRV+Tetric BF/ Group-4; Reflectys+Reflectys/Group 5; Reflectys+Tetric BF/Group-6), for repair. Then specimens were subjected to shear bond strength testing(SBS), and the debonded surfaces were examined.
Results
There was a significant difference among three materials(repaired with itself+bulk fill) for SBS testing values (p=0.001). FU and R were found to be similar, while HXRV was significantly different from them. A significant difference between group-1 and 2 (p=0.006) was detected, while there were no differences between group 3 and 4 (p= 0.142), and 5 and 6 (p=0.346). Among the six groups, repair SBS testing values with TBF were higher than repair with itself except for FU.
Conclusions
The bulk-fill repaired materials showed higher bond strength except for FU, which showed the highest SBS value when repaired with itself. An increased incidence of adhesive fracture was observed at low strengths.
Key words:Resin-based composites, nanofillers, surface treatment, macro-shear, repair.
... 21 The patterns of diffusion are governed by the "free volume theory", in which water passes through nanopores without any chemical reaction with polymer chains, or by the "interaction theory" in which water diffuses through the material binding successively to the hydrophilic groups. 22 Therefore, absorbed water exists in two distinct forms: "unbounded" that occupied free volume between the polymer chains and the nanopores created during polymerization 23 and "bound water" that is attached to polymer chains via hydrogen bonding. 24 The highest value of water absorbency by weight % is observed for Dyract flow material. ...
Aim: Polymerization of resin composite develops polymerization shrinkage and shrinkage stress at the restoration-tooth interface (up to 20 MPa, depending on the material), leading to microleakage and clinical complications. Water sorption in oral cavity may cause an increase in restoration volume and probably a decrease in shrinkage stress. This in turn can reduce the risk of restoration debonding. The aim was to evaluate the influence of water sorption by resin composites on polymerization shrinkage stress generated on the restoration-tooth interface.
Materials-Methods: Two resin composites, one compomer and one giomer were evaluated. The shrinkage stress was measured immediately after curing. The samples stored in water were evaluated after 24 h for 7 days and then once a week up to 90 days. Photoelastic study was performed on photosensitive epoxy resin plates in Transmission Polariscope FL200. The study was based on the analysis of dimension and arrangement of fringes. Shrinkage stress was calculated on the basis of elasticity theory. In order to measure the water sorption and its dynamics, the material samples were weight on analytical scale in the above mentioned time intervals.
Results: The tested materials during polymerization generated shrinkage stresses ranging from 4 to 20 MPa. After conditioning in water, the decrease in shrinkage strain after 72 h was observed. The decrease in value stress in time depended on the type of material.
Conclusions: Polymerizing dental materials generated differentiated shrinkage stress, that decrease in time due to water sorption. The dynamics of stress change is material dependant.
Keywords: water sorption, shrinkage stress, dental composites
... 21 The patterns of diffusion are governed by the "free volume theory", in which water passes through nanopores without any chemical reaction with polymer chains, or by the "interaction theory" in which water diffuses through the material binding successively to the hydrophilic groups. 22 Therefore, absorbed water exists in two distinct forms: "unbounded" that occupied free volume between the polymer chains and the nanopores created during polymerization 23 and "bound water" that is attached to polymer chains via hydrogen bonding. 24 The highest value of water absorbency by weight % is observed for Dyract flow material. ...
Introduction. The elimination or reduction of
shrinkage stress is one of the major problems in the
development of dental composites. Sorption of water
by resin fillings in the moist environment of the oral
cavity and in consequence its volume expansion
should counteract the observed shrinkage contraction.
Aim of the study. To evaluate the influence of water
sorption in resin-based materials on polymerization
shrinkage stress generated on the restoration-tooth
interface. Material and methods. The shrinkage stress
was measured immediately after curing. The samples
stored in water were evaluated after 24 h for 7 days
and then once a week up to 90 days. Photoelastic study
was performed on photosensitive epoxy resin plates
in Transmission Polariscope FL200. The study was
based on the analysis of dimension and arrangement of
fringes. Contraction stress was calculated on the basis
of photoelastic theory. In order to measure the water
sorption and its dynamics, the material samples were
weighed on analytical scale in the above mentioned
time intervals. Results. The tested materials during
polymerization generated shrinkage stresses ranging
from 6 to 17 MPa. After conditioning in water, the
decrease in shrinkage strain after 72 h was observed.
The decrease in value stress in time depended on the
type of material. Conclusions. Polymerizing dental
materials generated differentiated shrinkage stress
that decreased in time due to water sorption. The
dynamics of stress change is materia- dependent.
... The water uptake for composite resins induces stress between the softer matrix and the stiff filler particles, leading to filler-matrix interfacial failure and the formation of cracks in the matrix. The diffusion coefficient (water sorption-desorption properties) of a BisGMA/TEGDMA resin was found to be three times higher for specimens stored at 60° C, when compared to the ones at 37° C (Soderholm 1984). ...
... [10] Concurrently, water is diffused in to the polymer matrix of composites, swells the polymer, and fills the space between the main chains and crosslinks, as well as occupying the microvoids created during the polymerization phenomenon. [20] Time or aging is expected to be a significant factor associated with the amount of water sorption; moreover, composites which absorb more water, will show more decreased surface microhardness. The present study confirmed the latter clarification. ...
Although composite restorations are really valuable for esthetic zones, they have shown less longevity rather than amalgam restorations. Since it may be related to the method used for curing the composite, postcuring could increase the degree of conversion and result in more long-lasting composite restorations. This study was planned to evaluate the effect of two different postcuring techniques on microhardness of indirect composite resin after wet-aging and comparing them with the direct type.
In this experimental study, 99 composite disk-shaped (6.5 × 2.5 mm) specimens of composite (Gradia GC, Japan) were prepared in split mold. The indirect composite specimens were postcured by laboratory light source (Labolite LV-III GC Corp, Japan) or microwave unit (MC 2002 JR, LG, Korea). Then, the aging procedure was done for 24 h, 30 and 180 days in distilled water. The Vicker's Hardness test (VHN) on surface of specmens was measured by Wolpert microhardness tester and the data were analyzed by the two-way analysis of variance (ANOVA) and Tukey's post hoc tests. (P ≤ 0.05).
The statistical analysis revealed that surface microhardness of postcured composite by microwave and laboratory light source was more than that of direct composite (P = 0.0001) and postcuring by microwave was more effective than postcuring by laboratory light source (P = 0.004). The 30 days stored composite demonstrated significant decrease of VHN compared with the 24-h stored samples (P = 0.0001), with a more significant VHN decrease after 180 days of aging (P = 0.045).
Postcuring increased the surface microhardness and aging reduced the surface microhardness of indirect composite.
... The thickness, density and quality of the hybrid layer have been theorized to effect bonding [18.19]. However, if the depth of demineralization during the conditioning step is not met by the applied adhesive systems, then the unprotected collagen fibrils left on the base of the hybrid layer might allow faster water sorption and degradation [24–26]. Denuded collagens decrease the mechanical properties of the adhesive resin and permit the action of host-derived proteases [27]. ...
Multiple adhesive coating is a controversial topic, especially in primary dentition that should be clarified. We evaluated the effect of multiple consecutive adhesive resin coatings on the microshear bond strength (μSBS) of composite resin to primary tooth dentin utilizing a filled (Adper Single Bond Plus) and an unfilled (Adper Single Bond) adhesive resin.
Thirty extracted primary canines were randomly allocated into two groups based on the adhesive used. Dentin occlusal surfaces were exposed and further polished on 400, 600 and 800-grit silicon-carbide paper. The surfaces were divided into two halves in the labial-lingual orientation. After etching, the adhesives were used either in double coats, or four coats on the halves of the same tooth followed by air evaporation for each layer and finally light curing. Cylinders of composite were bonded to the dentin surfaces. After 24 h shear bond testing was evaluated by Bisco tensile tester. ANOVA, Student t test and paired t test were used for statistical analysis.
The mean (standard deviation) for double coats or four coats in single bond were 31.99 (2.94) and 30.25 (2.69), while they were 29.18 (3.35) and 31.26 (2.07) in single bond plus, respectively. No significant differences were found between the double coated specimens and those receiving four coatings with both adhesives (p>0.05). Micro SBS values of Single Bond double coated specimens were significantly higher than Single Bond Plus (p=0.02). In four-coated specimens, there were no significant differences between Single Bond and Single Bond Plus (p=0.26).
Applying four coats of adhesive did not improve the μSBS to primary tooth dentin.
... 19 In addition, the cross-linking agent ethylene glycol dimethacrylate present in the Lucitone 550 resin may have restricted the rotation of polymeric chains, decreasing the velocity of water diffusion to the polymer. 44 However, even considering all of the effects on the polymer matrix, the experiments with rhodanine showed that only free Ag + could react with this organic molecule; therefore, the results regarding the Ag release (Figs 4 and 5) are conclusive about the absence of Ag + in the PMMA/Ag nanocomposite. The glass transition temperature (T g ) is another physical property involved in the diffusion of liquid substances in polymeric materials. ...
Purpose: The aim of this study was to evaluate a denture base resin containing silver colloidal nanoparticles through morphological analysis to check the distribution and dispersion of these particles in the polymer and by testing the silver release in deionized water at different time periods.
Materials and Methods: A Lucitone 550 denture resin was used, and silver nanoparticles were synthesized by reduction of silver nitrate with sodium citrate. The acrylic resin was prepared in accordance with the manufacturers’ instructions, and silver nanoparticle suspension was added to the acrylic resin monomer in different concentrations (0.05, 0.5, and 5 vol% silver colloidal). Controls devoid of silver nanoparticles were included. The specimens were stored in deionized water at 37°C for 7, 15, 30, 60, and 120 days, and each solution was analyzed using atomic absorption spectroscopy.
Results: Silver was not detected in deionized water regardless of the silver nanoparticles added to the resin and of the storage period. Micrographs showed that with lower concentrations, the distribution of silver nanoparticles was reduced, whereas their dispersion was improved in the polymer. Moreover, after 120 days of storage, nanoparticles were mainly located on the surface of the nanocomposite specimens.
Conclusions: Incorporation of silver nanoparticles in the acrylic resin was evidenced. Moreover, silver was not detected by the detection limit of the atomic absorption spectrophotometer used in this study, even after 120 days of storage in deionized water. Silver nanoparticles are incorporated in the PMMA denture resin to attain an effective antimicrobial material to help control common infections involving oral mucosal tissues in complete denture wearers.
... This phenomenon may be explained by the increasing water uptake into the polymer network. This causes the polymer network to swell which is associated with a reduction of the intermolecular forces between the polymer chains [50,52]. In addition, hydrolysis phenomena between the matrix and fillers may also play a role (hydrolysis of the silane layer which promotes crack propagation in the periphery of the filler particles) [23,50,53] as the bond between filler particles and matrix has a noticeable effect on the fracture toughness [54,55]. ...
Temporary crowns and fixed partial dentures are exposed to considerable functional loading, which places severe demands on the biomaterials used for their fabrication (= temporary crown & bridge materials, t-c&b). As the longevity of biopolymers is influenced by the ability to withstand a crack propagation, the aim of this study was to investigate the fracture toughness of cross-linked and non-cross-linked t-c&bs.
Four different t-c&bs (Luxatemp AM Plus, Protemp 3 Garant, Structur Premium, Trim) were used to fabricate bar shaped specimens (2mmx5mmx25mm, ISO 13586). A notch (depth 2.47mm) was placed in the center of the specimen using a diamond cutting disc and a sharp pre-crack was added using a razor blade. 60 specimens per material were subjected to different storage conditions (dry and water 37 degrees C: 30min, 60min, 4h, 24h, 168h; thermocycling 5-55 degrees C: 168h) prior to fracture (3-point bending setup). The fracture sites were inspected using SEM analysis. Data was subjected to parametric statistics (p=0.05).
The K(IC) values varied between 0.4 and 1.3MPam(0.5) depending on the material and storage time. Highest K(IC) were observed for Protemp 3 Garant. Fracture toughness was significantly affected by thermocycling for all dimethacrylates (p<0.05) except for Structur Premium. All dimethacrylates showed a linear-elastic fracture mechanism, whereas the monomethacrylate showed an elasto-plastic fracture mechanism.
Dimethacrylates exhibit a low resistance against crack propagation immediately after curing. In contrast, monomethacrylates may compensate for crack propagation due to plastic deformation. However, K(IC) is compromised with increasing storage time.
... To some extent, the limited effect of the age of composite on repair bond strength observed in this study may also be a result of the specific matrix chemistry of the resin composite used. The Bis-GMA adduct used in Spectrum TPH is more hydrophobic than unmodified Bis-GMA due to the substitution of two hydroxy groups [13] which may reduce water sorption and related detrimental effects [13,26,28,30,32]. ...
The aim of this study was to investigate the effect of different mechanical and adhesive treatments on the bond strength between pre-existing composite and repair composite using two aging times of the composite to be repaired. Standardized cylinders were made of a microhybrid composite (Spectrum TPH) and stored in saline at 37 degrees C for 24 h (n = 140) or 6 months (n = 140). Three types of mechanical roughening were selected: diamond-coated bur followed by phosphoric acid etching, mini sandblaster with 50-microm aluminum oxide powder, and 30-microm silica-coated aluminum oxide powder (CoJet Sand), respectively. Adhesive treatment was performed with the components of a multi-step bonding system (OptiBond FL) or with a one-bottle primer-adhesive (Excite). In the CoJet Sand group, the effect of a silane coupling agent (Monobond-S) was also investigated. The repair composite (Spectrum TPH) was applied into a mould in three layers of 1 mm, each separately light-cured for 40 s. Repair tensile bond strengths were determined after 24-h storage. Mechanical and adhesive treatment had significant effects on repair bond strength (P < 0.001). The age of the pre-existing composite had no significant effect (P = 0.955). With one exception (CoJet Sand/OptiBond FL Adhesive), adhesive treatments significantly increased repair bond strengths to 6-month-old composite when compared to the controls without adhesive. Adhesive treatment of the mechanically roughened composite is essential for achieving acceptable repair bond strengths. The more complicated use of silica-coated particles for sandblasting followed by a silane coupling agent had no advantage over common bonding systems.
Objectives
The aim of this study was to assess the fatigue loading behavior and fracture resistance of endodontically treated teeth restored with adhesively luted bundled fiber posts in comparison to solid fiber posts. Image analysis (2D and 3D) was applied to evaluate modes of failure and to characterize susceptible parts of the post-and-coreinterface.
Method
Crowns of 72 human similar-sized central upper incisors were removed and roots received a conventional root canal filling prior to establishing 4 groups of core build-up: No Post group (nP) received a 4 mm deep filling made of composite inside the canal with no dental post, fiber post group (FP) received a conventional solid post, and two experimental groups received bundles of 6 (FB6) or 12 (FB12) 0.3 mm thin fiber posts, respectively. Posts were placed adhesively inside the root canal using a dual-curing build-up composite in combination with a self-etch adhesive, the latter was also used for nP group. Upon completion of core build-ups, all teeth received full-ceramic crowns that recreated the original tooth form. Samples were subjected in a 135° angle to thermo-mechanical loading (TML) for 1.2 Mill. chewing cycles followed by static load tests (fracture resistance). Fracture modes as well as intracanal failure modes with respect to failed interfaces were analyzed using optical and electron microscopy (SEM). Microcomputer tomography (μCT) was used to exemplary compare pre and post TML geometries.
Results
Static load test was significantly different between groups (p < 0.0005; Kruskal-Wallistest). Pairwise comparison showed that the nP group (221 ± 103N) failed at significantly lower forces compared to the FP (454 ± 184N), FB6 (477 ± 250N) and FB12 (478 ± 260N) groups (p ≤ 0,001; Mann-Whitney-U-test). Fracture modes were significantly affected by the presence or absence of a post (p ≤ 0,016; Chi-square test) revealing increased incidence of restorable fractures at the cervical region for nP group. Microscopic analysis revealed more intracanal failures at interfaces between post surfaces and composite for solid posts, whereas fiber bundled posts mostly failed at the interfaces between composite and dentin. Micro-CT analysis showed no alterations of the root-post-and-core structure after TML except slight deformations of occasionally entrapped voids.
Conclusion
Fracture resistance and fracture modes were significantly affected by the presence or absence of a post, whereas the investigated post groups did not differ from each other. However intracanal failure revealed differences in adhesive failures between solid fiber posts and bundled fiber posts. Deformations of entrapped voids, revealed by micro-CT analyses after TML, indicate that applied forces lead to alterations especially in the regions of voids.
In order to improve the durability of the adhesive layer, we experimentally prepared an HEMA-ethanol base primer containing 4-META (ME) or MDP adding a fluorine compound, and a bonding agent consisting of Bis-GMA/TEGDMA (Bis/3G), and evaluated its adhesive strength. As a result, it was found that the addition of 2,2,2-trifluoroethyl methacrylate (FM) was useful in improving the durability of adhesion to dentin. Affinity of the primer containing FM for bonding agents is not completely clear as yet, however. In the present study, the durability of the adhesive layer using bonding agents of different viscosities, i. e., Bis/3G, UDMA (UD) and UD/3G, was evaluated with the aim of improving the penetration and diffusion of bonding agents within the dentin treated with the primer containing FM. Five kinds of experimental primer containing MDP with addition of no FM and containing ME with addition of 0, 0.5, 1.0 and 5.0 wt% FM were applied to the dentin of the crown of bovine teeth, respectively. Three kinds of experimental bonding agent, Bis/3G, UD, and UD/3G, were applied, and photo-irradiated. Then, they were filled with Clearfil AP-X and used as specimen. After 1 day and 6 months of water storage and a 4℃/60℃ thermal cycling test, the shear bond strength of each specimen was measured with a cross head speed of 1 mm/min. Under all experimental conditions, the ME primer showed a significantly stronger adhesion to the dentin than the MDP primer. Irrespective of the different kinds of bonding agent applied, the ME primer containing FM showed no significant decrease in adhesion to dentin after water storage for 6 months or after a thermal cycling test, and maintained a nearly stable adhesive strength. In addition, the combined use of 5.0 wt% FM containing ME primer and UD/3G showed the strongest adhesive strength. On the other hand, the MDP primer used in combination with different bonding agents showed no effectiveness. Thus, the results showed that combination of a self-etching primer containing ME with the addition of FM and a UD/3G bonding agent formed an adhesive layer of the highest durability.
In this study, trans-1,2-dimethacryloyloxycyclohexane (DMC) was synthesized as a monomer with low viscosity for crown and bridge resin. The mechanical characteristics of the composite resin which was comprised of UDMA-DMC and silica were examined. The viscosity of DMC was the same as TEGDMA, and the water sorption of its polymer was lower than that of TEGDMA. The mechanical properties of the UDMA-TEGDMA which was photocured were higher than that of the UDMA-DMC. However, when the specimen was heattreated, the mechanical properties increased. The elastic modulus and Knoop hardness of the UDMA-DMC gave a higher value than that of the UDMA-TEGDMA.
To improve the hydrolytic stability of photo cure composite resin, 1, 2-dimethacryloyloxy benzene (DMB) was synthesized. After adding DMB to urethane dimethacrylate (UDMA), the effect on the mechanical properties of the copolymers and photo cure composite resin was investigated. The bending strength of the copolymer with added DMB did not decrease, even though the specimen was immersed in water for 30 days at 60℃. This is due to the fact that the water absorption of the copolymer was decreased by the addition of DMB. However, the bending strength of composite resin was decreased by water absorption. This decrease in the bending strength by the addition of DMB to the matrix resin was less than that by the addition of TEGDMA. We conclude that the addition of DMB to photo cure composite resin could improve hydrolytic stability.
A review with 78 references covering the linear and volumetric contraction producing internal stresses in photocured dental restorative resin composites. The stresses are partially reduced by the flow of resin, ingress of air bubbles, and absorption of water. Computer simulations allow to predict the directions of shrinkage vectors. Polymerization shrinkage of (meth)acrylate monomers can be reduced by fillers (up to 80%) or prepolymers added to the base monomer mix. Free-radical ring-opening polymerization of suitable monomers decreases volume contraction because some covalent bonds are cleft to give near Van der Waals bond distances.
Objectives:
Dental resin-based restorative materials are used in a variety of dental treatment modalities such as root-end filling, perforation sealing, and adhesion of fractured roots. However, the prognosis after such treatments is not necessarily favorable because they fail to promote healing of the surrounding alveolar tissue. In the present study, non-biodegradable poly-2-hydroxyethyl methacrylate (polyHEMA)-based hydrogel particles were fabricated as a carrier vehicle for drug delivery that is applied to dental resins.
Methods:
The loading and release characteristics of bovine serum albumin (BSA) and fibroblast growth factor-2 (FGF-2) from the polyHEMA-based hydrogel particles were evaluated over time in culture. The hydrogel particles were immersed into an aqueous FITC-labeled BSA solution and were observed using confocal laser scanning microscopy (CLSM). To determine the activity of the FGF-2 released from the particles, the proliferation of osteoblast-like cells cultured with eluates collected from the particles for up to 14 days was determined.
Results:
CLSM revealed that BSA was adsorbed to the surface of the hydrogel particles. A sustained release of BSA and FGF-2 from the particles was detected for up to 14 days. The eluates from the FGF-2-loaded particles increased the proliferation of the osteoblast-like cells, suggesting that the activity of FGF-2 was maintained for at least 2 weeks within the particles.
Significance:
These polyHEMA-based non-degradable hydrogel particles may be useful tools that can be applied to dental restorative materials to achieve sustained delivery of drugs that promote tissue regeneration.
This study evaluated the change in the ultimate tensile strength (UTS) of five polymerised resin blends of increasing hydrophilicity, after ageing in distilled water or silicon oil. Resin blocks were prepared from each resin blend by dispensing the uncured resin into a flexible, embedding mould, containing multiple cavities. The resins were polymerised in the moulds under nitrogen at 551.6 kPa and light-activated at 125°C for 10 min. After dry ageing for 24 h at 37°C, the middle third of each resin specimen was trimmed into an ‘I’ shape. Fifteen control specimens were randomly selected from each resin blend for baseline UTS evaluation. The UTS of the experimental specimens were determined after 1, 3, 6 and 12 months of ageing in water or oil. The UTS of each group of resins at different storage periods in water or oil were analysed using the Friedman multiple ANOVA on ranks and Dunn's multiple comparison tests at 95% confidence level. Significant reduction (p<0.01) in UTS was observed in Groups II–V resins after 12-month storage in water, while the most hydrophobic Group I resin showed no significant change (p>0.05) in the same period. The percentage reduction in UTS increased with the hydrophilicity of the resin blends. Long-term water storage of hydrophilic resin blends such as those employed in dentine adhesives, resulted in a marked reduction in their mechanical strength that may compromise the durability of resin–dentine bonds.
Purpose:
To evaluate in vitro the effect of using titanium tetrafluoride as an alternative etchant prior to the silanization of the bonding surface on the long-term resin bond strength to lithium disilicate ceramic.
Materials and methods:
Disk-shaped specimens made of lithium disilicate ceramic were ground with abrasive paper, then etched with aqueous solutions (2.5% and 5%) of titanium tetrafluoride for 60 s, 120 s and 240 s. Positive control specimens were etched with 5% hydrofluoric acid for 20 s and negative control specimens were not etched. Afterwards, bonding surfaces of all specimens were silanized. Plexiglas tubes filled with a composite resin were bonded to the specimens using an alignment apparatus and a composite luting resin. After storage in 37°C tap water for three days (n = 8) and after storage in 37°C tap water for 150 days interrupted by 5 x 7500 thermal cycles (n = 8), tensile bond strength (TBS) was measured in a universal testing machine at a crosshead speed of 2 mm/min.
Results:
After artificial aging, all specimens etched with titanium tetrafluoride debonded spontaneously resulting in a TBS of 0 MPa. Therefore, statistical analysis revealed a highly significant difference between the positive control and the test groups after 150 days storage.
Conclusion:
Etching the bonding surface of lithium disilicate ceramic restorations with hydrofluoric acid is still a "gold standard" and cannot be replaced by titanium tetrafluoride.
Purpose:
To evaluate the influence of different adhesive strategies (etch-and-rinse and self-etching adhesives) and type of field isolation (absolute or relative) on the clinical performance of restorations of noncervical carious lesions (NCCLs).
Materials and methods:
One hundred forty NCCLs were selected from 38 patients, according to previously established inclusion/exclusion criteria, and assigned to one of four groups (n = 35): etch-and-rinse/rubber-dam (ERR), etch-and-rinse/cotton roll (ERC), self-etching/rubber-dam (SER) and self-etching/cotton roll (SEC). The adhesive systems used were: Adper Single Bond 2 (3M ESPE) and Adper SE Plus (3M ESPE), with restorations made using a composite resin (Z350, 3M ESPE). Using the USPHS modified criteria, 140 restorations were evaluated by two calibrated examiners at 5 different times: immediately after placement, at 7 days, and 2, 6, and 12 months. In order to evaluate the presence of gingival recession after the use of the #212 rubber-dam clamp, the clinical crowns of the teeth from groups ERR and SER were measured at six different periods (baseline, immediately, and at 7 days, 2, 6, and 12 months). Data were subjected to McNemar's, chi-square, and Student's t-tests.
Results:
Both adhesive strategies reduced tooth sensitivity beyond the second period of evaluation (7 days); tooth sensitivity disappeared after the third period of evaluation (2 months). There were no statistically significant differences between the adhesive techniques or isolation techniques, except for a Bravo score for marginal discoloration in group SEC at 6 months, which was significantly different from the other groups. The rubber-dam isolation technique was more uncomfortable for the patient and resulted in short-term gingival recession.
Conclusion:
No significant differences were found between the types of isolation or adhesive strategy in this clinical evaluation, with the exception of 2 restorations in group SEC that showed marginal discoloration, possibly due to inadequate enamel etching by the self-etching adhesive. Class V restorations perform equally well placed with or without rubber-dam.
Four commercial bisphenol-glycidilmethacrylate based composites used mainly for dental applications have been investigated. Differential thermal analysis performed on samples aged in water for different times indicated a small residual monomer reactivity which disappeared after ageing. A further crosslinking reaction facilitated by water plasticization and a monomer loss could be the main reasons for such 8 phenomenon. The embrittlement of these materials with ageing time has been detected from flexural mechanical properties. Water sorption/desorption experiments have been performed on G!! the materials studied at different temperatures. The decrease of diffusion coefficients with increasing water content together with the microscopic analysis of the fracture surfaces demonstrated good filler/matrix adhesion for all the four composites. The decrease of water diffusion coefficients with time for Miradapt, Silar and Adaptic has been explained on the base of the presence in the polymeric networks of different density regions due to inhomogeneous polymerization. This hypothesis is also in line with the Miradapt, Silar and Adaptic hysteresis phenomena observed in the sorption/desorption cycles.
With over 200 million dental restorations performed each year, the importance of developing a restorative material with tooth-like appearance and properties cannot be underestimated. In this article, the use of poly (multimethacrylates) as dental composites is summarized from both fundamental and practical sides. Detail is provided regarding the utilization, procedures, and problems with polymeric composite restoratives, and a complete discussion of the polymerization kinetics and the polymer structural evolution is presented. In the final sections, properties of current composite materials and suggestions for what areas of research would prove most promising are presented.
Objectives:
Post-cure heat treatments have been shown to increase the fracture toughness and elastic modulus of composites. The objective of this study was to determine if the increase remained after the composites were aged in water. METHODS. The fracture toughness (K(lc)), flexural modulus and flexural strength of four experimental and one commercial composite (Z-100, 3M Dental Products) were tested after 1, 7, 30, 60 and 180 d of aging in 37 degrees C water. The four experimental composites were made with a BisGMA/TEGDMA resin and were characterized as follows: Micro = 38 vol% silane-treated silica, Fine = 65 vol% silane-treated quartz of 1-2 micrometer average size, Hybrid = 65 vol% silane treated quartz of a mixture of 1-2 micrometer average and 8 micrometer average size, and Large = 65 vol% quartz of 8 micrometer average size (of which only 75% were silane-treated). All specimens were light-cured (normal-cured; Triad II - 80 s). One set of each composite was further heat-cured at 120 degrees C for 10 min (heat-cured). A third set of the Hybrid was heat-cured with simultaneous light exposure (Elipar, Espe) for the first 3 min.
Results:
By 30 d, normal-cured and heat-cured specimens showed significant (ANOVA/Tukey's test; p < or = 0.05) reductions in fracture toughness (avg. 16% and 22%, respectively), flexural modulus (avg. 11% and 11%, respectively) and flexural strength (avg. 25% and 29%, respectively). Further aging had little effect. The use of additional light-curing during heating did not affect the properties more than heat-curing alone.
Significance:
The improvements in some of the properties of composites produced by heat-treating are of only short-term benefit, and are for the most part negated due to an alteration of the resin matrix as the composite equilibrates with water.
Objectives:
The aim of this study was to test the effect of adhesive temperature on the bond strength to dentin (muTBS) and silver nitrate uptake (SNU) of an ethanol/water (Adper Single Bond 2 [SB]) and an acetone-based (Prime&Bond 2.1 [PB]) etch-and-rinse adhesive system.
Methods:
The bottles of each adhesive were kept in various temperatures (5 degrees C, 20 degrees C, 37 degrees C and 50 degrees C) for 1h previously to its application in the occlusal demineralized dentin of 40 molars. Bonded sticks (0.8 mm(2)) were tested in tension (0.5 mm/min) immediately (IM) or after 6 months (6 M) of water storage. Two bonded sticks from each hemi-tooth were immersed in silver nitrate and analyzed by SEM. Data were analyzed by two-way repeated measures ANOVA and Tukey's test (alpha=0.05).
Results:
No significant difference in muTBS was detected for both adhesives at 5 degrees C and 20 degrees C. The highest bond strength for PB was observed in the 37 degrees C group while for SB it was in the 50 degrees C. Significant reductions of bond strengths were observed for PB at 37 degrees C and SB at 50 degrees C after 6 M of water storage. Silver nitrate deposition was seen in all hybrid layers, irrespective of the group. Lower silver nitrate deposition (water trees) in the adhesive layer was seen for PB and SB at higher temperatures.
Conclusions:
The heating or refrigeration of the adhesives did not improve their resin-dentin bond resistance to water degradation over time.
To examine the effect of hydrogen peroxide on the microhardness and color change of resin composites containing nanofillers.
Three resin nanocomposites with three different shades and two different tooth whitening agents were used. The specimens were given a 3-week treatment with one of three protocols: (1) 7 hours/day treatment of carbamide peroxide (CP) + 17 hours/day immersion in distilled water (DW); (2) 1 hour/week treatment of hydrogen peroxide (HP) + immersion in DW for the rest of the week; and (3) immersion in DW for 24 hours/day. The microhardness and color changes were measured after treatment.
After treatment with the whitening agents, there was an 8.1-10.7% decrease in the original microhardness. These values were similar to those obtained from the samples treated with distilled water. In the same resin product, the decrease was similar regardless of the test agents used. In most cases, the color change was only slight (deltaE*=0.5-1.4). Hydrogen peroxide enhanced the color change but the absolute color change values were similar in the same product and shade, regardless of the test agent used.
The aim of this clinical trial was to evaluate the effects of application mode on the clinical performance of a two-step etch-and-rinse adhesive in class V cavities over 24 months. Forty patients with at least three similar-sized non-carious cervical lesions participated in this study. A total of 120 restorations with Prime & Bond NT were placed, 40 in each group. The adhesive was applied with no rubbing action, with slight rubbing action, or with vigorous rubbing action. The restorations were placed incrementally using the composite resin Esthet-X. The restorations were evaluated at baseline and after 6, 12, and 24 months following the modified United States Public Health Service criteria. Statistical analysis was conducted using Friedman repeated measures analysis of variance by rank and using the Wilcoxon signed-rank test for significance at each pair (α = 0.05). The 24-month retention rates of Prime & Bond NT were 82.5% for the no rubbing group, 82.5% for the slight rubbing group, and 92.5% for vigorous rubbing group. No significant difference in the retention rates in each recall period was detected among groups (p > 0.05); however, the retention rates in the 24-month recall was statistically lower than the baseline only for no rubbing or slight rubbing groups. The use of a vigorous application mode can be a clinical approach to improve the retention of restorations placed in non-carious cervical lesions.
The method of porosity analysis by water absorption has been carried out by the storage of the specimens in pure water, but it does not exclude the potential plasticising effect of the water generating unreal values of porosity.
The present study evaluated the reliability of this method of porosity analysis in polymethylmethacrylate denture base resins by the determination of the most satisfactory solution for storage (S), where the plasticising effect was excluded.
Two specimen shapes (rectangular and maxillary denture base) and two denture base resins, water bath-polymerised (Classico) and microwave-polymerised (Acron MC) were used. Saturated anhydrous calcium chloride solutions (25%, 50%, 75%) and distilled water were used for specimen storage. Sorption isotherms were used to determine S. Porosity factor (PF) and diffusion coefficient (D) were calculated within S and for the groups stored in distilled water. anova and Tukey tests were performed to identify significant differences in PF results and Kruskal-Wallis test and Dunn multiple comparison post hoc test, for D results (α=0.05).
For Acron MC denture base shape, FP results were 0.24% (S 50%) and 1.37% (distilled water); for rectangular shape FP was 0.35% (S 75%) and 0.19% (distilled water). For Classico denture base shape, FP results were 0.54% (S 75%) and 1.21% (distilled water); for rectangular shape FP was 0.7% (S 50%) and 1.32% (distilled water). FP results were similar in S and distilled water only for Acron MC rectangular shape (p>0.05). D results in distilled water were statistically higher than S for all groups.
The results of the study suggest that an adequate solution for storing specimens must be used to measure porosity by water absorption, based on excluding the plasticising effect.
This double-blind randomized clinical trial compared different ethanol/water and acetone-based systems in non-carious cervical lesions over 36 months.
Eighty-four patients having at least one non-carious cervical lesion [NCCL] under occlusion were enrolled in this study. A total of 84 restorations were placed, half for each group (Adper Single Bond [SB] + FiltekA110 or One Step [OS] + MicroNew). All the materials were placed by two calibrated operators. Two other independent examiners evaluated the restorations at baseline, 6, 12, 18 and 36 months, according to slightly modified USPHS criteria. Statistical analysis between materials in each period was conducted using the Fisher's exact test (alpha=0.05), and performance of the materials in the baseline in comparison to each period was evaluated by McNemar's test (alpha=0.05).
The 12-, 18- and 36-month retention rates for SB were 95.2% (12 and 18 months) and 92.3% (36 months). For OS, the retention rates were 83.3%, 73.8% and 56.4%, respectively, for each recall period. After 36 months, 10 OS restorations (25.7%) and seven SB restorations (17.9%) were rated as Bravo in the marginal discoloration item.
The ethanol/water-based adhesive (Single Bond) that was evaluated showed a higher retention rate than the acetone-based system (One Step) after 36 months of clinical service.
This study examined the effect of temperature on water sorption and solubility characteristics of four commercial dental adhesives. The null hypothesis tested was that temperature has no effect on the water sorption and solubility characteristics of these adhesives.
The tested materials were: three-step etch-and-rinse (All-Bond 2, AB), two-step etch-and-rinse (One-Step, OS), two-step self-etch (Clearfil SE Bond, SE) and one-step self-etch (Clearfil S3 Bond, S3) adhesives. Seven resin disks (6mm in diameterx1mm in thickness) were prepared from each tested material and were stored in deionized water at 23 degrees C, 37 degrees C and 55 degrees C. Water sorption and solubility of the resin disks were measured before and after water immersion and desiccation following two consecutive sorption and desorption cycles. The water sorption and solubility values obtained were analyzed using two-way ANOVA and Tukey's multiple comparison tests. The relationships between maximum water sorption, solubility and kinetics of water diffusion with temperature were evaluated by means of Pearson correlation statistic.
OS exhibited the highest water sorption and solubility values in the second sorption-desorption cycle at 55 degrees C (p<0.001). This is followed by S3, SE and AB with no significant difference between SE and AB. Significant positive correlations were observed between maximum water sorption (r=0.307, p<0.01), solubility (r=0.244, p<0.05), water sorption (r=0.651, p<0.001) and desorption (r=0.733, p<0.001) diffusion coefficients (obtained using Fick's law of diffusion) with temperature in the second cycle.
High temperatures increased water sorption of simplified adhesives. Such water sorption may contribute to the failure of resin-dentin bonds.
The aim of the present study was to investigate which parameters (chemical nature, time after mixing, surface characteristics) might affect the repair strength of temporary crown and bridge materials (t-c&b).
Four different t-c&bs (Cool Temp Natural, Protemp 3 Garant, Structur Premium, Trim) were investigated using a shear-bond strength (SBS) setup. A cylinder (2 mm x 2.37 mm) of identical t-c&b (n=10) was bonded onto a specimen surface of either freshly set t-c&b (10 min after mixing) or onto specimens that were stored for 24h (37 degrees C, distilled water) and 7 days (thermocycling x 5,000, 5-55 degrees C=TC), respectively. The specimen surface was roughened with SiC paper (grit size 320) or left as it was (specimens stored for 10 min) prior to repair to retain the oxygen-inhibition layer. In addition, mono-block specimens were fabricated as control. The thickness of the oxygen-inhibition layer and the surface morphology was determined. Statistical analysis was carried out with an ANOVA followed by parametric tests (p=0.05).
SBS values ranged from 10 to 40 MPa. Trim showed lowest SBS values for most storage conditions. Material, surface characteristics and time after mixing significantly affected the SBS (ANOVA p<0.001). TC significantly reduced the SBS (p<0.05) for all t-c&bs except for Trim (p>0.05).
In case of monomethacrylates, storage and surface condition do not affect the repair strength. In contrast, the repair quality of dimethacrylates greatly depends on the material. In any case, roughening the surface is recommended, even if an oxygen-inhibition layer is present.
A near infrared (NIR) method using the 5200 cm(-1) absorption of water has been employed to examine water absorbed in photopolymerized dental resins and composites in the form of 0.01-cm- to 0.15-cm-thick specimens. The concentration, c [mol L(-1)], of absorbed water in specimens of thickness t [cm] was calculated by means of Beer's law, A = e ct. A is the NIR absorbance and e is the absorptivity of absorbed water. e depends on the environment of the water molecule and it is necessary to estimate e for water in each material. Water sorption was determined gravimetrically and correlated to the absorbance in the NIR spectrum. Once the relationship between e and water content was known for a material, water sorption was determined rapidly on very thin specimens for faster equilibration. Where dissolution of the specimen occurred, the solubility behavior of the specimen was evaluated from a comparison of NIR and gravimetric measurements. The NIR absorptivity, e, of water absorbed in a polymeric medium was found to be inversely related to the degree of hydrophilicity and hydrogen bonding capability of the polymer. The presence of water clusters in a polyethylene oxide methacrylate polymer was inferred from convex-up curvature in the plot of e vs. water content.
The uptake of solvent and the elution of molecules from a dental composite and an unfilled resin were monitored with time during soaking in either water or an ethanol/water mixture. The results showed that approximately 50% of the leachable species were eluted from the composite within three hours of soaking in water, while 75% of the leachable molecules were eluted into the ethanol/water mixture. Elution of nearly all of the leachable components was complete within a 24-hour period in either solvent. The study lends support to the view that dental composites do not provide a chronic source of unreacted monomer to the pulp or other oral tissues, due to a rapid and complete elution of the molecules.
Six different dental composite materials were investigated regarding leaching of filler elements such as silicon, barium, and zinc. The leaching was conducted by storing the samples in distilled water at 60 degrees C for half a year. The results could not prove that the leaching behavior of filler elements in most of the investigated cases decreases with time. The practical implications of this study could be important. If other elements follow the same leaching pattern, therapeutic elements such as fluoride could be incorporated in filler particles. The tendency of composites to leach filler elements almost linearly with time, could be used to generate a constant release rate of such therapeutic elements over time. Such an application could have a major impact on controlling caries adjacent to composite restorations and sealants.
Polymethacrylate networks were made by copolymerization of a range of compositions of bis-GMA and triethylene glycol dimethacrylate (TEGDM). Polymerization was initiated both by heating with benzoyl peroxide or by photopolymerization (lambda greater than 400 nm) using camphoroquinone as sensitizer. The uptake of water increased from 3 to 6% as the proportion of TEGDM increased from 0 to 1.0. Intermediate compositions took up less water than would be predicted from the law of mixtures. Volumetric changes were determined and clinical significance discussed. A copolymer prepared by photopolymerization took up more water as the temperature was increased from 24-60 degrees C. In this range, values of the diffusion coefficient (D) conformed to the Arrhenius equation, D = Do exp (-E/RT), giving E = 42-46 kJ/mol and Do = 0.13 cm2 s-1.
Since their introduction, composite resin filling materials have replaced direct filling resins and the silicate cements as the materials of choice for anterior restorations where aesthetics are of the primary importance. These materials have met with wide acceptance in spite of several performance shortcomings. It has been reported that many of the commercial composite resin materials exhibit some leakage at the margins of the restoration (1–4) and gross surface disintegration (5). Many investigators have attempted to trace these problems to some basic properties of the system, such as water sorption and polymerization shrinkage (6). Due to the complex nature of this system, the results of these investigations have not been conclusive.
Recent experiments have indicated that the diffusion properties of a penetrant-polymer system may change with time as diffusion proceeds. It is thought that two possible explanations of these time effects are slow changes of polymer structure accompanying diffusion and internal stresses exerted by one part of the polymer sheet on another as it swells. Two theoretical models are set up in order to express these effects quantitatively. The first model is essentially that in terms of which mechanical and other properties of polymers are commonly discussed, involving the concept of an instantaneous change of diffusion coefficient when the concentration changes, followed by a slow drift toward an equilibrium value. The second model expresses the effect of stresses set up between the outer swollen layers and the unattacked center of a polymer sheet during sorption. These stresses are slowly relieved as the diffusion proceeds, leading to a time-dependent diffusion coefficient. The main features of diffusion behavior are established by calculation and the models are shown to account for the various types of sorption and desorption curves observed experimentally under different conditions, e.g., for sheets of different thicknesses and for different ranges of penetrant concentration. As examples, sorption and desorption curves calculated from the first model are shown to agree reasonably well with experimental curves for the methylene chloride-polystyrene system. The rate of sorption and of the associated change in area of the sheet are accounted for by the second model. The presence of internal stresses also provides an explanation for the observation that there may be an appreciable interval of time during which a thin sheet takes up more penetrant than a thicker one under corresponding conditions. On the other hand, it is the slow structural changes which cause the rate of sorption to be not always inversely proportional to the square of the thickness of the sheet. It is concluded that both polymer relaxation and internal stresses play a part in determining diffusion behavior. The particular experimental results examined can be accounted for if the half-life of the slow structural changes is comparable with that of the sorption experiment itself, and if the internal stresses change the diffusion coefficient by a factor of two or three.
The uptake of water by composite filling materials seems to be a diffusion-controlled process; the magnitudes of the diffusion coefficients obtained are consistent with the uptake base through the resin matrix. The diffusion coefficients measured show the diffusion coefficient to decrease with increasing water concentration, which accounts for the protracted nature of the attainment of equilibrium uptake. Diffusion coefficients are generally lower in these composites based on difunctional methacrylates, compared with methyl methacrylate, presumably because of the highly cross-linked nature of the former.
Earlier published measurements of the polymerization shrinkage and water-absorption expansion of plastic filling materials are often difficult to relate to the clinical application of the materials. In the present work an attempt has been made to rectify this situation. The following materials were investigated: Adaptic, Addent XV, Blendànt, Concise, D.F.R., Palakav, capsulated Palakav, TD 71, Palavit 55, Sevriton Simplified and Swedon. The filling materials were placed in cavities cut in extracted teeth. Dimensional changes of the fillings were measured in a microscope. The complete investigation was conducted in a thermostat room maintained at 37°C. The fillings were examined either shortly after initial set or after varying periods of immersion in water. Immediately after initial set a marginal gap at both the enamel and dentin levels of the walls was observed. Polishing the fillings at this time resulted in a zone of fractured enamel 20—40 microns wide. If the fillings were stored in water, the width of the marginal gaps was reduced; for some brands the gaps were completely closed in less than 32 days. Polishing of fillings with closed shrinkage gaps resulted in a minimum of fractures of the enamel margins.
Four aromatic, thermosetting, composite dental restorative materials were evaluated for their mechanical and physical properties. The properties of two materials approached those of dentin and dental amalgams. One of the materials tested appeared to have the necessary requirements for use as both an anterior and posterior restorative material.
A degradation of untreated fillers in composites stored in distilled water was indicated by an increased sodium and hydroxy ion concentration in storage water, and by examination of the fillers with SEM. Silane treatment of the fillers retarded the leaching process, while cycling stresses accelerated it.