Posterior resin-based composite restorations: a second opinion.
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Adolescent↗
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Effects of bleaching with carbamide peroxide gels on microhardness of restoration materials.
The objective of this in vitro study was to quantitatively assess the effects of bleaching with 10 and 15% carbamide peroxide (CP) on restoration materials by performing superficial microhardness analysis. Acrylic cylindrical containers (4 x 2 mm) were filled with the following restoration products: Charisma (Heraues Kulzer, Vila Santa Catarina, São Paulo, Brazil), Durafill VS (Heraeus Kulzer), Vitremer (3M, Sumaré, São Paulo, Brazil), Dyract (Dentsply, Petrópolis, Rio de Janeiro, Brazil), and Permite C (SDI, São Paulo, São Paulo, Brazil). Sixty samples were prepared of each restoration material. Twenty samples received bleaching treatment with 10% CP, 20 samples received bleaching treatment with 15% CP, and 20 samples were kept submerged in artificial saliva, which was replaced daily. The treatment consisted of immersion of the specimens in 1 cm3 of CP at 10 and 15% for 6 hours per day during 3 weeks, whereupon the test specimens were washed, dried, and kept immersed in artificial saliva for 18 hours. Then the test and control specimens were analyzed using a microhardness gauge. The Knoop Hardness Number (KHN) was taken for each test and control specimen at five different locations by applying a 25 g force for 20 seconds. The values obtained were transformed into KHNs and the mean was calculated. The data were submitted to statistical analysis by analysis of variance and Tukey test, p < .05. The means/standard deviations were as follows: Charisma: CP 10% 38.52/4.08, CP 15% 34.31/6.13, saliva 37.36/4.48; Durafill VS: CP 10% 18.65/1.65, CP 15% 19.38/2.23, saliva 18.27/1.43; Dyract AP: CP 10% 30.26/2.81, CP 15% 28.64/5.44, saliva 33.88/3.46; Vitremer: CP 10% 28.15/3.04, CP 15% 17.40/3.11, saliva 40.93/4.18; and Permite C: CP 10% 183.50/27.09, CP 15% 159.45/5.78, saliva 215.80/26.15. A decrease in microhardness was observed for the materials Dyract AP, Vitremer, and Permite C after treatment with CP at 10 and 15%, whereas no effect on either of the two composites (Charisma and Durafill) was verified. CLINICAL SIGNIFICANCE The application of the carbamide peroxide gels at 10 and 15% did not alter the microhardness of the composite resins Charisma and Durafill. In situ and clinical studies are necessary to enable one to conclude that the reduction in microhardness of the materials effectively results in clinical harm to the restorations.
Analysis of Variance↗
Adhesion to enamel of light-cured poly-acid dental materials.
The purpose of this study was to determine the tensile bond strengths of a resin-modified glass ionomer cement and a poly-acid modified resin composite to enamel. Three different enamel surface preparations (unetched enamel; enamel treated with 10 per cent polyacrylic acid, enamel etched with 35 per cent phosphoric acid), were used. On etched enamel, the glass ionomer cement (15.0 MPa) and the resin composite (14.3 MPa) had significantly higher bond strengths than the other groups tested, but were not significantly different from each other. In the acid treated groups, cohesive failure within the material occurred in all specimens, while in the other groups, all specimens failed adhesively. Further investigation is required to test the clinical efficacy of these restorative materials.
Acid Etching, Dental↗
Clinicians' choices of restorative materials for children.
BACKGROUND: Recently, there has been an expansion in the range of tooth-coloured restorative materials available. In 1999, the National Health and Medical Research Council recommended clinicians use alternatives to amalgam in children 'where appropriate'. METHODS: A three-part 29-item questionnaire was developed, tested in a focus group, and distributed to members of the Australasian Academy of Paediatric Dentistry (AA; paediatric dentists and paediatric dentistry postgraduate students; n=55), and the Australian and New Zealand Society of Paediatric Dentistry, Victorian Branch (SPD; general dentists and dental therapists; n=50). Participant information, material choices, and six hypothetical clinical scenarios were addressed. RESULTS: The overall response rate was 74 per cent. For both groups, the first ranked factor influencing choice of restorative material for vital primary teeth was child age, and caries experience for vital first permanent molars. For moderate-sized Class I and II restorations in primary molars, a tooth-coloured material was chosen by 92 and 84 per cent respondents respectively. For restoring two separate proximal lesions in a primary molar, 65 per cent chose a tooth-coloured material followed by a stainless steel crown (27 per cent; all AA members), then amalgam (8 per cent). The SPD respondents were significantly more likely to choose glass ionomer cement for Class I and II restorations and for restoring two proximal lesions (all p=0.000) in primary molars than AA respondents, who were more likely to choose composite resins/compomers or amalgam/stainless steel crowns for these restorations. Younger respondents (21-40 years) were significantly more likely to choose composite resins/compomers or amalgam/stainless steel crowns (p=0.048) than older respondents (41-65 years), who were likely to choose glass ionomer cement. CONCLUSIONS: For Class I and II restorations in primary molars, glass ionomer cement was the material chosen most frequently (SPD respondents); preference for amalgam or stainless steel crowns was low (both SPD and AA groups). The wide range of materials chosen for the hypothetical clinical scenarios suggests the need for guidelines on selection of restorative materials, and the need for longitudinal studies to follow actual clinical outcomes of the materials chosen.
Adolescent↗
Bond strength of simplified-step adhesives to enamel prepared with two different diamond burs.
BACKGROUND: Self-etching primers are reported to produce considerable etching on flat enamel surfaces. However, little is known about the influence of different enamel surface textures. In this study the influence of grinding enamel on bond strength of two all-in-one and one two-step adhesives was investigated. METHODS: Resin composite was bonded to the ground enamel of extracted human third molars that was reduced 0.5 mm from the buccal or lingual surfaces using either regular- or superfine-grit diamond burs with each of the three adhesives. After 24 hours in 37 degrees C water, the specimens were sectioned into slabs of 0.7 mm thickness, trimmed to an hourglass configuration, and subjected to microtensile bond strength (MTBS) testing. RESULTS: For all adhesive systems, MTBS to enamel ground with a regular-grit diamond bur was not significantly different from that with a superfine-grit diamond bur. The etching patterns of these adhesives were partly varied according to the aggressiveness of the adhesives. CONCLUSION: The use of two different burs does not affect the tensile bond strength of the adhesives to enamel.
Acid Etching, Dental↗
Placement and replacement of restorations by selected practitioners.
BACKGROUND: There are few Australian data on the reasons for placement and replacement of restorations, and the extent to which these are carried out in general practice. METHODS: A survey was carried out of approximately 100 consecutive restorations placed by each of 28 general dental practitioners. The data were coded and statistically analyzed for various associations. RESULTS: Resin composite was used twice as frequently as amalgam as a restorative material, and nearly four times as often as glass-ionomer cement. Secondary caries was the principal reason for replacing restorations, affecting predominantly amalgam restorations in Class I and Class V cavities. Teeth restored with amalgam fractured nearly twice as often as teeth restored with resin composite. The average ages of amalgam, resin composite and glass-ionomers at replacement were 13.6, 7.1 and 5.7 years respectively. CONCLUSIONS: Amalgam has the longest clinical service life, but is associated with more tooth fracture. Secondary caries is the main reason for replacing restorations. The anti-cariogenic effect of glass-ionomer cement is equivocal.
Adolescent↗
Fluoride release and uptake by aged resin-modified glass ionomers and a polyacid-modified resin composite.
Little has been reported of the relationship of fluoride release and weight loss, and the effects of use of different fluoride agents on restorations, for the new generation of glass ionomer cements. The objectives of this study were to compare fluoride release of fresh and aged specimens of a polyacid-modified resin composite (Dyract), and of three resin-modified glass ionomer cements (Fuji II LC, Photac-Fil, Vitremer); and to correlate fluoride release and weight loss of aged specimens after recharging with three different fluoride agents. All materials showed high initial fluoride release immediately after uptake when using the agents. However, the levels of fluoride release dropped rapidly soon afterwards. Although initial fluoride release was significantly different between Dyract and the three resin-modified glass ionomers, when different fluoride agents were used on aged specimens after recharging, no significant differences were found after the first few hours. Linear regression analyses also showed no correlation between cumulative fluoride release and weight loss. Possible beneficial oral health effects may only be expected by frequent exposure of these materials to fluoride agents.
Acidulated Phosphate Fluoride↗
The influence of oral bacteria on the surfaces of resin-based dental restorative materials--an in vitro study.
Three tooth-coloured, resin-based restorative materials (Charisma, Dyract, and Pertac) were exposed to typical oral bacteria (S. mutans, S. oralis and A. naeslundii) over a period of up to 35 days. The three strains of bacteria all colonised the resin-based materials within a few hours and formed thick bacterial films. Determination of the bacterial glucose consumption and lactate production during the incubation period showed no difference from the controls which contained no resin samples. Following the experimental exposure, the materials were examined by scanning electron microscopy (SEM) for possible surface damage and roughness was measured in a perthometer. Little damage to the resin-based composite material surfaces (Charisma, Pertac) could be observed, whereas the polyacid-modified composite material (Dyract) showed greater damage. There was a significant difference in the resin surface roughness after exposure to S. mutans and to A. naeslundii. The study clearly showed that the bacteria used strongly adhered to the resin-based restorative materials. As a consequence of bacterial colonisation and/or poor oral hygiene, damage to the restorative materials might develop. This suggests the need for dentists to evaluate personal oral hygiene, along with general indications and economic factors, in selecting materials for restorations, since the known anti-bacterial properties of amalgam are considerable.
Actinomyces↗
Dyract versus Tytin Class II restorations in primary molars: 36 months evaluation.
Due to the changed treatment approach of proximal caries and the amalgam controversy, clinicians are in search for new materials. The aim of the present study was to compare amalgam with an adhesive material in deciduous molars in a clinical, split-mouth design study. At baseline 30 polyacid modified composite (Dyract) and 30 amalgam (Tytin) restorations were placed in primary molars, of which 24 and 17 could be evaluated after 24 and 36 months, respectively. Modified USPHS criteria were used for clinical evaluation every 6 months. Annual bite-wing radiographs were taken for evaluation of recurrent caries and cervical gap formation. In the present study, for Dyract as well as for Tytin restorations, low rates of recurrent caries were found, while Dyract restorations showed a better marginal adaptation and surface texture compared to Tytin restorations. In the Dyract group more radiolucencies were found at baseline. In both groups no patient complaint or pain was reported related to the radiolucencies. After 3 years the colour of Dyract was not comparable to the original. For Dyract no excessive wear was noticed compared to enamel. During the study one Dyract (recurrent caries: 18 months) and two Tytin (pulpal aetiology: 6 months, recurrent caries: 36 months) restorations had to be replaced. Even though the restorations were placed in caries risk children, at the 36 months' evaluation of this clinical study, the results indicate that Dyract can be an alternative for Tytin in the primary dentition.
Child↗
An intraoral study of caries induced on enamel in contact with fluoride-releasing restorative materials.
The aim was to study the effect of three fluoride-releasing restorative materials on sound enamel of approximal teeth under cariogenic conditions intraorally. Bovine enamel slabs were paired with four hemispherical samples from each of three test materials (Ketac Molar, ESPE; Vitremer, F-2000, both from 3M) and one control material (Pertac II, ESPE). Their curved surface touched enamel at a contact point allowing space for plaque accumulation. Pairs were inserted in the buccal flanges of 2 lower dentures for 70 days. Initially and upon dismantling, enamel surface microhardness was measured and the increase in length of indentation in micrometers was recorded at a distance of 0, 0.4, 0.8 and 1.2 mm from the contact point. Respective values were: Pertac II: 16.0+/-7.5, 27.6+/-15.4, 38.6+/-23.3, 47.8+/-25.2; F-2000: 11.89+/-9.6, 15.8+/-14.2, 21.0+/-15.0, 25.1+/-15.2; Ketac Molar: 6.6+/-6.8, 9.4+/-7.0, 9.5+/-8.0), 13.4+/-9.4; Vitremer: 2.7+/-4.1, 3.5+/-3.5, 3.6+/-4.5), 7.4+/-5.2. Caries protection was Vitremer 82% > Ketac Molar 69% >F-2000 42% in relation to Pertac II (p<0.001). Sections of the slabs examined with polarized light showed typical subsurface lesions only in the Pertac II group, areas of pseudoisotropy in the F-2000 and Ketac Molar groups and no signs of lesion in the Vitremer group.
Aged↗
X-ray diffraction study of acid-degradable glasses.
The composition of the degradable glasses used in commercial dental glass-ionomer cements determines their leaching behavior and hence the properties of the cement. The objective of the present study was to assess if the composition and leaching in acetic acid solutions are reflected in the x-ray diffraction characteristics of these glasses. The position (2theta) of the maximum of the first sharp diffraction peak shifts to higher diffraction angles with increasing number and ionic radius of mono- and bivalent cations in the glass. Upon acid-leaching, these ions are preferentially leached out, so that (2theta) decreases. These results can be related to the decreasing Si-Si distance in the glass network with increasing modifier radius.
Acetates↗
The extent to which resin can infiltrate dentin by acetone-based adhesives.
The combined methodologies of fractography and laser-Raman spectroscopic analysis were used for evaluation of the resin-dentin bonds made with wet and dry bonding. Resin-dentin-bonded beams were produced by means of 2 acetone-based adhesives (One-Step and Prime & Bond NT). The micro-tensile bond test was conducted, and the fractured surfaces of all specimens were examined by SEM and an image analyzer. The amount of resin infiltration within the hybrid layer was quantified by means of a laser-Raman spectroscope. In Raman analysis, the amount of resin impregnation within the hybrid layer of the dry bonding was found to be significantly lower (approximately 50%) than that in the wet one. Under fractographic analysis, a correlation was found between the bond strength and the failure mode. Based on those findings, it was suggested that the integrity between the bonding resin and the top of the hybrid layer played a major role in bond strength.
Acetone↗
Comparative physico-mechanical characterization of new hybrid restorative materials with conventional glass-ionomer and resin composite restorative materials.
The recently developed hybrid restorative materials contain the essential components of conventional glass ionomers and light-cured resins. The objective of this study was to determine several physical and mechanical properties of eight such materials in comparison with two conventional glass ionomers, one micro-filled, and one ultrafine compact-filled resin composite. The two resin composites and two of the three polyacid-modified resin composites could be polished to a higher gloss than the conventional as well as the resin-modified glass ionomers. After abrasion, surface roughness increased for all materials, but not at the same extent, being the least for the conventional resin composites and one polyacid-modified resin composite, Dyract. In contrast to the later resin composites, of which the surface roughness is principally determined by the presence of protruding filler particles above the resin matrix, roughness of conventional and resin-modified glass ionomers results from both protruding filler particles and intruding porosities. The mean particle size of the hybrid restorative materials fell between the smaller mean particle size of the resin composites and the larger one of the conventional glass ionomers. The micro-hardness and Young's modulus values varied substantially among all eight hybrid restorative materials. For all the resin-modified glass-ionomer restorative materials, the Young's modulus reached a maximum value one month after mixing and remained relatively stable thereafter. The Young's modulus of the conventional and the polyacid-modified resin composites decreased slightly after one month. The conventional glass-ionomer materials undoubtedly set the slowest, since their Young's modulus took six months to reach its maximum. The flexural fatigue limit of the hybrid restorative materials is comparable with that of the micro-filled composite. From this investigation, it can be concluded that the physico-mechanical properties vary widely among the eight hybrid restorative materials, indicating that these materials probably have yet to achieve their optimum properties. Their mechanical strength is inadequate for use in stress-bearing areas, and their appearance keeps them from use where esthetics is a primary concern.
Acrylic Resins↗
Stoichiometry of the leaching process of fluoride-containing aluminosilicate glass-ionomer glasses.
Dental glass-ionomer cements (GIC) set by an acid-base reaction between a polyalkenoic acid and an ion-leachable glass. The exact relationship between the glass composition and the setting and final properties of GIC is not yet fully elucidated. As part of a systematic study of this relationship, we studied the leaching stoichiometry of glasses used in commercial formulations to correlate the glass composition with its leaching properties. The leaching experiments were performed in acetic acid solutions at pH = 3.4 by means of a pH-stat method. After predetermined time intervals, the suspension was filtered and the filtrate was analyzed for the glass constituents. The usefulness of the pH-stat method for the determination of glass reactivity was corroborated. The deviation of the leaching stoichiometry with respect to the pure glass stoichiometry decreased with increasing relative content of mono- and bivalent glass network dwellers and modifiers. Indications were found that the latter can be leached out independently and preferentially, while the leaching of network dwellers is coupled with the aluminum release. The F content as well as the reactivity of the glass affect the amount of fluoride available for release from a set GIC. It could be concluded that the leaching stoichiometry of GIC glasses can be correlated with their absolute and relative composition.
Acetates↗
Fatigue of restorative materials.
Failure due to fatigue manifests itself in dental prostheses and restorations as wear, fractured margins, delaminated coatings, and bulk fracture. Mechanisms responsible for fatigue-induced failure depend on material ductility: Brittle materials are susceptible to catastrophic failure, while ductile materials utilize their plasticity to reduce stress concentrations at the crack tip. Because of the expense associated with the replacement of failed restorations, there is a strong desire on the part of basic scientists and clinicians to evaluate the resistance of materials to fatigue in laboratory tests. Test variables include fatigue-loading mode and test environment, such as soaking in water. The outcome variable is typically fracture strength, and these data typically fit the Weibull distribution. Analysis of fatigue data permits predictive inferences to be made concerning the survival of structures fabricated from restorative materials under specified loading conditions. Although many dental-restorative materials are routinely evaluated, only limited use has been made of fatigue data collected in vitro: Wear of materials and the survival of porcelain restorations has been modeled by both fracture mechanics and probabilistic approaches. A need still exists for a clinical failure database and for the development of valid test methods for the evaluation of composite materials.
Compomers↗
Infrared spectrometric study of acid-degradable glasses.
The composition of glasses used in glass-ionomer cements affects their leaching behavior and hence the properties of the cement. The aim of this study was to correlate the composition and leaching behavior of these glasses with their infrared absorption characteristics. The wavenumber of the absorption band of the Si-O asymmetric stretching vibration shifts to a higher value with decreasing content of mono- and bivalent cations in the glass. This effect can be ascribed to the influence of these extraneous ions on the glass network order and connectivity. Preferential leaching of these ions induces an increase of asymmetric stretching vibration and a general modification of the band profile. The results can be correlated with the x-ray diffraction characteristics of the glass.
Acetates↗
Effects of fluoride and aluminum from ionomeric materials on S. mutans biofilm.
Ionomeric materials release different proportions of fluoride and aluminum. Their simultaneous effect on the acidogenicity and composition of S. mutans biofilm is unknown. Six cylindrical specimens of each material (Ketac-fil, Vitremer, Fuji-Ortho LC, F-2000, and Z-100) were incubated with S. mutans GS-5 in culture media containing 5% sucrose (w/v). The media were changed daily for seven days, during which the pH and concentrations of fluoride and aluminum were determined. Furthermore, the concentrations of these ions and insoluble polysaccharide were determined in the biofilm formed at the end of the experimental period. The results showed that all the materials tested released fluoride. However, Vitremer released the highest amount of aluminum and was the most effective in reducing the acidogenicity of S. mutans biofilms. It also significantly affected both biofilm formation and composition. Thus, this study suggests that aluminum released by ionomeric materials may enhance the biological effects of fluoride.
Acrylic Resins↗
In vivo and in vitro permeability of one-step self-etch adhesives.
Adhesive dentistry should effectively restore the peripheral seal of dentin after enamel removal. We hypothesize that non-rinsing, simplified, one-step self-etch adhesives are effective for minimizing dentin permeability after tooth preparation procedures. Crown preparations in vital human teeth were sealed with Adper Prompt, Xeno III, iBond, or One-Up Bond F. Epoxy resin replicas were produced from polyvinyl siloxane impressions for SEM examination. Dentin surfaces from extracted human teeth were bonded with these adhesives and connected to a fluid-transport model for permeability measurements and TEM examination. Dentinal fluid droplets were observed from adhesive surfaces in resin replicas of in vivo specimens. In vitro fluid conductance of dentin bonded with one-step self-etch adhesives was either similar to or greater than that of smear-layer-covered dentin. TEM revealed water trees within the adhesives that facilitate water movement across the polymerized, highly permeable adhesives. Both in vitro and in vivo results did not support the proposed hypothesis.
Acid Etching, Dental↗