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PubMed2006

Effect of surface treatments on the bond strength of brackets bonded with a compomer.

PURPOSE: To evaluate the effectiveness of the compomer Dyract AP for bonding brackets when conditioning the enamel with phosphoric acid and a non-rinsing conditioner (NRC), in comparison with a control group in which the resin orthodontic adhesive system Transbond XT was used. METHODS: The brackets were bonded to extracted premolars which were divided into three groups: (1) Acid/Transbond XT, (2) NRC/Dyract AP and (3) Acid/Dyract AP. Shear bond strength was measured with a universal testing machine. The crosshead speed was 1mm/minute. The adhesive remnant on the tooth after debonding was determined using image analysis equipment. RESULTS: The bond strength of Acid/Transbond XT was significantly higher than bond strengths of Acid/Dyract AP and NRC/Dyract AP (P< 0.017). No significant differences were observed between Acid/Dyract AP and NRC/Dyract APBond strength values (P> 0.017). Acid/Transbond XT left significantly more adhesive on the tooth than Acid/Dyract AP and NRC/Dyract AP, whereas NRC/Dyract AP left significantly less adhesive than Acid/Dyract AP (P< 0.05).

Acid Etching, Dental↗
PubMed1997

Shear bond strength of Dyract compomer material to dentin of primary molars.

The purpose of this study was to measure and compare the shear bond strength and fracture pattern of Dyract compomer material with and without use of PSA prime/adhesive as well as 35% phosphoric acid etching to the buccal dentin of primary first and second molars. In addition, micromorphology of the restorative surfaces opposing the tooth structure following these different surface treatments was evaluated. For shear bond strength measurement and fracture pattern evaluation, 36 extracted non-restored human primary molars with mild to moderate caries divided into 3 groups of 12 teeth each were used. Dyract with and without use of PSA prime/adhesive as well as 35% phosphoric acid etching for 15 seconds prior to placement of PSA prime/adhesive was applied to the buccal surface of exposed dentin. A standardized tube of Dyract was placed on each dentin surface and polymerized. The tubes were sheared off with a Universal testing machine at a cross head speed of 12.7 mm/min. For evaluation of the restorative surfaces opposing the tooth structure, 9 teeth divided into 3 groups of 3 teeth each were used to prepare the specimens, which were then demineralized in 10% hydrochloric acid for 24 hours. Fitting surfaces of these specimens were prepared and examined using scanning electron microscope. Tukey's multiple range test showed that the shear bond strength of Dyract with PSA prime/adhesive (group 1) was statistically significantly higher than Dyract without PSA prime/adhesive (group 2) and phosphoric acid etching (group 3). The shear bond strength in group 1 averaged 5.89 +/- 1.40 (X + SD MPa) while for groups 2 and averaged 1.49 +/- 0.69 and 3.69 +/- 0.89 respectively. Pretreatment of dentin surface with 35% phosphoric acid increased resin tags formation but it did significantly lower shear bond strength of Dyract with PSA prime/adhesive to dentin of primary molars. Bond failure patterns for all groups were only adhesive and mixed type failures.

Adhesives↗
PubMed1997

Laboratory evaluation of compomers in Class V restorations.

PURPOSE: To evaluate the in vitro microleakage, marginal morphology and resin tags configuration of a compomer restorative material (Dyract) alternatively used with two different bonding systems (Dyract-PSA and Prime & Bond 2.0). A hybrid resin composite (Prisma TPH) used with two different bonding systems (Universal Bond 3 and ProBond) was evaluated as control material. MATERIALS AND METHODS: Class V non-retentive restorations were made in vitro at CEJ and divided at random in four groups: Dyract/PSA, Dyract/P&B 2.0, Prisma TPH/UB3, and Prisma TPH/ProBond. The latter two groups were as controls. After finishing the restorations, an impression material was used to obtain an epoxy resin replica for SEM analysis of margin alterations. Percentage of perfect margin was evaluated under SEM and calculated comparing it with the width/length of restoration margin. The presence of gaps, enamel fractures and other marginal alterations was also recorded inspecting under SEM replicas. Each tooth was then immersed for 24 hours in erythrosin B dye solution at room temperature and evaluated at superficial margins as marginal leakage (ML) for dye penetration. Each sample was then longitudinally sectioned, and leakage was expressed as % dye penetration of the total cavity wall, longitudinal leakage (LL). Finally, each tooth was dissolved (10%H3PO4 for 48 hours and NaOCl solution for additional 24 hours) to leave only the resin restoration. The internal walls of each restoration were then inspected by SEM at x1,000-15,000 to evaluate the presence of resin-dentin infiltrated layer (hybrid layer) and to calculate the ability of primer/bonding to infiltrate peritubular dentin and to form resin tags. RESULTS: Gap widths were 2-6 microns at dentin and lower at enamel. Several enamel fractures along the margin were observed. Resin tags were observed only in deeper dentin. Only Prime & Bond 2.0/Dyract formed resin tags at medium-superficial dentin. The length of resin tags ranged from 1-6 microns for Dyract-PSA primer to 100 microns for Prime & Bond 2.0. Marginal and longitudinal leakage was observed both at dentin and enamel levels. The best dentin seal was obtained with Prime & Bond 2.0/Dyract, while enamel seals were equivalent with both bonding systems (P > 0.05). No correlations were demonstrated between leakage and SEM observations.

Adult↗
PubMed1998

Marginal microleakage around enamel and cementum surfaces of two compomers.

The purpose of this study was to evaluate the marginal microleakage of two compomers, placed in enamel and cementum. The buccal and lingual surfaces of twenty human premolar teeth were used. Materials used were Dyract and Compoglass. Teeth were randomly divided into 4 groups of 5 teeth each. Materials were handled according to the instructions of the manufacturer. Class V cavities were prepared with enamel and cementum margins. The groups with etched surfaces was done using 37% phosphoric acid. Two percent fuchsin was used for microleakage study. Results were evaluated using an analysis of ANOVA. These showed that microleakage in enamel was significantly less than in cementum. No significant differences in microleakage were seen between the two materials or between etched and unetched surfaces.

Acid Etching, Dental↗
PubMed2004

Sequencing from compomers: using mass spectrometry for DNA de novo sequencing of 200+ nt.

One of the main endeavors in today's life science remains the efficient sequencing of long DNA molecules. Today, most de novo sequencing of DNA is still performed using the electrophoresis-based Sanger concept of 1977, in spite of certain restrictions of this method. Methods using mass spectrometry to acquire the Sanger sequencing data are limited by short sequencing lengths of 15-25 nt. We propose a new method for DNA sequencing using base-specific cleavage and mass spectrometry that appears to be a promising alternative to classical DNA sequencing approaches. A single stranded DNA or RNA molecule is cleaved by a base-specific (bio-)chemical reaction using, for example, RNAses. The cleavage reaction is modified such that not all, but only a certain percentage of bases are cleaved. The resulting mixture of fragments is then analyzed using MALDI-TOF mass spectrometry, whereby we acquire the molecular masses of fragments. For every peak in the mass spectrum, we calculate those base compositions that will potentially create a peak of the observed mass and, repeating the cleavage reaction for all four bases, finally try to uniquely reconstruct the underlying sequence from these observed spectra. This leads us to the combinatorial problem of sequencing from compomers and, finally, to the graph-theoretical problem of finding a walk in a subgraph of the de Bruijn graph. Application of this method to simulated data indicates that it might be capable of sequencing DNA molecules with 200+ nt.

Algorithms↗
PubMed2004

The effect of Coca-Cola and fruit juices on the surface hardness of glass-ionomers and 'compomers'.

The interaction of tooth-coloured dental restorative materials (a conventional glass-ionomer, two resin-modified glass-ionomers and two compomers) with acidic beverages has been studied with the aim of investigating how long-term contact affects solution pH and specimen surface hardness. For each material (ChemFil Superior, ChemFlex, Vitremer Core Build-Up/Restorative, Fuji II LC, Dyract AP and F2000) disc-shaped specimens were prepared and stored in sets of six in the following storage media: 0.9% NaCl (control), Coca-Cola, apple juice and orange juice. After time intervals of 1 day, 1 week, 1 month, 3 months, 4 months, 6 months and 1 year, solution pH and Vickers Hardness Number were determined for each individual specimen. Differences were analysed by anova followed by Student-Newman-Keuls post hoc analysis. All materials were found to reduce the pH of the 0.9% NaCl, but to increase the pH of the acidic beverages. The conventional glass-ionomers dissolved completely in apple juice and orange juice, but survived in Coca-Cola, albeit with a significantly reduced hardness after 1 year. The other materials survived in apple juice and orange juice, but showed greater reductions in surface hardness in these beverages than in Coca-Cola. Fruit juices were thus shown to pose a greater erosive threat to tooth coloured materials than Coca-Cola, a finding which is similar to those concerning dentine and enamel towards these drinks.

Beverages↗
PubMedDate not supplied

Radiopacity of compomers, flowable and conventional resin composites for posterior restorations.

The objective of this study was to densitometrically determine the relative radiopacity (aluminum [Al]-equivalent values) of dentin, enamel, and 20 resin composite materials currently used for posterior restorations. Specimens 5 mm in diameter and 2 mm thick were fabricated from 20 materials (n = 7) for a total of 140 specimens. Human molars were longitudinally sectioned 2.0 mm thick to include both enamel and dentin. The optical densities of enamel, dentin, restorative materials, lead, and aluminum step wedge were obtained from radiographic images, using a transmission photodensitometer. The Al equivalent (mm) for each material was calculated from the linear regression equation of the log of normalized optical density and Al mm thickness obtained from the step wedge. A linear regression of the logarithm of normalized optical density and Al mm thickness was plotted (r2 = 0.9953), and the relative radiopacities, expressed as equivalent thickness of Al, were ranked ordinally. All materials tested, with the exception of an unfilled resin adhesive, complied with ISO Standard 4049, being at least as radiopaque as a 2.0 mm thickness of 99.6% pure Al. Four of six flowable composites had radiopacity values that fell between that of dentin and enamel, while two materials were more radiopaque than enamel. The three compomers tested had radiopacities greater than enamel. In addition, all traditional light- and chemical-cure resin composite materials tested were more radiopaque than enamel. All materials tested, with the exception of one adhesive resin, were at least as radiopaque as dentin and complied with ISO Standard 4049. Clinicians should be able to distinguish these restorative materials radiographically from recurrent decay, voids, gaps, or other defects that lead to clinical failure. Utilization of materials ranked more radiopaque than enamel would enable clinicians to distinguish the restorative material from tooth structure.

Absorptiometry, Photon↗
PubMed1997

Barcoll hardness of resin-modified glass-ionomer cements and a compomer.

The objective of this study was to evaluate the influence of several factors on the hardness of resin-modified glass-ionomer cements (hybrid ionomers) and polyacid-modified resin composites (compomers). Disk-shaped specimens were prepared from the following materials: Vitremer, Fuji II LC, Photac-Fil, and Dyract. Three specimens of each product were irradiated with a light-curing device and three were not. Barcoll hardness was determined on both sides of the specimen 10 minutes after irradiation and after 48 hours of immersion in 37 degrees C water. A factorial design was used to evaluate the factors that influenced the results. The Dyract group that was not light cured was not included in the analysis because the product did not harden under this circumstance. Analysis of variance revealed a significant effect of material, time, and specimen side when light curing was carried out. The use or nonuse of light curing was also significant. For some hybrid ionomers (e.g., Photac-Fil), light curing is a more essential step than for others to obtain adequate hardness values.

Analysis of Variance↗
PubMed1997

Marginal adaptation to enamel of a polyacid-modified resin composite (compomer) and a resin-modified glass ionomer cement in vivo.

Recently, new restoratives, such as resin-modified glass ionomer cements (RMGIC) and polyacid-modified resin composites (PMC) were introduced for class III and class V cavities. Both materials use simplified cavity conditioning methods. The well-established treatment of enamel with phosphoric acid has been replaced with treatment using weaker acids. The purpose of this study was to investigate in vivo the quality and durability of the marginal bond to enamel of these restorative system and compare it with a resin composite restorative, Seventeen patients received class III restorations of each of the three restoratives. At baseline and after 1 year replica impressions were made for investigation of the vestibular margins with the scanning electron microscope. Semi-quantitative analysis of the enamel-restorative interfaces was performed at x200 and x1000 magnifications. The three restorative systems showed good marginal adaptation and high percentages of the length of the margins investigated at baseline were gap-free (82%-92%). The resin composite showed significantly better adaptation than the other materials. The marginal quality decreased significantly after 1 year for the resin composite and the polyacid-modified resin composite. The RMGIC showed improved sealing after 1 year in vivo, probably due to continuing water uptake. The percentages of gap-free margins of the total marginal length observed at 1 year were 73%, 90%, and 84%, respectively, for the PMC, the RMGIC and the resin composite. The difference between the PMC and the RMGIC was significant. In conclusion, a good marginal quality was seen for all three restorative systems in class III cavities after a period of 1 year.

Acid Etching, Dental↗
PubMed1998

Interfacial adaptation of in vivo aged polyacid-modified resin composite (compomer) restorations in primary molars. A SEM evaluation.

Polyacid-modified resin composite (PMC) restorations are being increasingly used in class II cavities in primary teeth. The aim of this study was to evaluate the interfacial adaptation of 1-month- and 30-month-old in vivo restorations by quantitative scanning electron microscopy (SEM) evaluation. Twelve PMC restorations were performed under clinically controlled conditions in primary molars planned for extraction 1 month later for orthodontic reasons. Eleven other PMC restorations, aged 30 months (range 1.5-3 years) and part of a multicenter study, were collected after exfoliation. To observe the interfacial adaptation of each restoration at several levels a thin layer of the proximal surface was ground off 2-3 times. Replica impressions of each level were prepared for SEM. The interfaces of the replicas were evaluated at x200 and x1000. In the 1-month-old restorations gap-free adaptation to enamel was found in 87% and to dentin in 84% of the total interfacial length investigated. For the 30-month-old restorations gap-free adaptation was registered in 59 and 63%, respectively. The interfacial quality was significantly better in the 1-month-old restorations than in those 30 months of age. Adaptation to enamel was significantly better in the cervical part of the 1-month-old restorations than in the axial walls, whereas there was no significant difference in dentin. No significant difference was found between the cervical and axial cavity walls of the 30-month-old restorations. Enamel fractures were registered in 31 and 24%, respectively of the interfacial length of the 1-month- and 30-month-old restorations. The corresponding findings in dentin were 0 and 0.9%. It can be concluded that restorations aged for a short time showed a high percentage of sealing, which decreased significantly for the 30-month-old ones.

Analysis of Variance↗
PubMed2004

Fluoride release and recharge in giomer, compomer and resin composite.

OBJECTIVES: The aim of this study was to examine the fluoride recharging and releasing abilities of resin-based materials containing fluoridated glass filler to determine whether the extent of the glass-ionomer matrix of the material affects these properties. METHODS: Three materials having a different proportion of the hydrogel matrix surrounding the glass filler, namely: Reactmer paste, Dyract AP and Xeno CF, were used for this study. Five disk specimens of each material were placed into distilled/deionized water and the fluoride release measured during 38 days. For fluoride recharge the disks were exposed to 250 ppm F solution for 1 h and the pre- and post-recharge fluoride release were determined using an ion-selective electrode (total fluoride ions) and ion chromatography (free fluoride ions). RESULTS: The amounts of total and free fluoride release from each material at the initial period in descending order were Reactmer paste > Dyract AP > Xeno CF (p < 0.05 ANOVA and Scheffe's test). After fluoride recharge, Reactmer paste showed a greater amount of fluoride release than the other materials. Dyract AP and Xeno CF showed a similar total level of fluoride release after recharging. For Xeno CF the amount of total fluoride released after recharging was significantly greater than that of free fluoride, but there was no significant difference between total and free fluoride released after recharging for Dyract AP (p = 0.05 paired t-test). SIGNIFICANCE: These results suggested that the extent of the glass-ionomer matrix of the glass filler played an important role for fluoride-releasing and recharging abilities of the resin-based materials.

Analysis of Variance↗
PubMed2005

Clinical evaluation of composite and compomer restorations in primary teeth: 24-month results.

PURPOSE: This split-mouth, blind study evaluated the clinical performance of Dyract AP, F2000, and Heliomolar placed in primary molars of 30 children (mean age, 6 years and 2 months). MATERIALS AND METHODS: From a total of 79 restorations accomplished, 27 were built with Heliomolar (18 Class I, and 9 Class II), 30 were with F2000 (21 Class I and 9 Class II), and 22 were built with Dyract AP (14 Class I and 8 Class II). All of teeth restored had primary caries lesions. At 6, 12, 18 and 24 months, 60 restorations (75%) were evaluated using USPHS criteria for: color match (CM), marginal adaptation (MA), marginal discoloration (MD), anatomic form (AF) and secondary caries (SC) by three calibrated operators. The Alpha+Bravo score percentage was considered as clinical success. The data were subjected to statistical analysis by Mann-Whitney and Kruskal-Wallis tests (p<0.05). RESULTS: Heliomolar showed the smallest success clinical at 12 months for marginal adaptation and secondary caries, and at 18 months for marginal discoloration. Regarding color match and anatomic form, no significant differences were found among the groups at each evaluation period. When materials were compared, Heliomolar did not show a significant difference among the evaluated periods for any criteria, remaining with the lowest scores. Significant differences were observed at 12 months for F2000 (marginal adaptation), and at 24 months for Dyract AP (marginal discoloration and secondary caries) and for F2000 (color match and marginal discoloration). CONCLUSIONS: It was concluded that Dyract AP and F2000 showed the best clinical performance over 24 month-evaluations for marginal discoloration and secondary caries, and color match and marginal adaptation, respectively. The use of the resin composite Heliomolar in Class I/II restorations in primary molars should be carefully considered.

Acrylic Resins↗
PubMed2002

Marginal integrity of different resin-based composites for posterior teeth: an in vitro dye-penetration study on eight resin-composite and compomer-/adhesive combinations with a particular look at the additional use of flow-composites.

OBJECTIVE: To determine improvements in marginal adaptation of resin-based composite restorative systems by means of flow-composites (Solitaire 2/Gluma Solid Bond, Solitaire 2/Flow Line/Gluma Solid Bond, Point 4/Optibond Solo Plus, Point 4/Revolution/Optibond Solo Plus) and to determine the equality of simplified bonding systems (Solitaire 2/Gluma Comfort Bond, Tetric Ceram/Tetric Flow/Excite, Dyract AP/Prime & Bond NT/NRC, Pertac II/Prompt-L-Pop) in marginal gap formation. METHODS: The marginal dye penetration (2% methylene-blue) was investigated separately for the approximal boxes of Class II mod-cavities with one cervical margin of the approximal box within enamel, the other within cementum. The surface analysis determined the percentage of dye-penetrated cervical and lateral margins of the approximal boxes, while the in depth investigation reported the mean dye penetration (mm) at both different cervical margins. RESULTS: After thermocycling (5000 x , 5-55 degrees C) the percentage of dye penetration at the cervical cementum margins ranged from 16.5 +/- 5.9% (Solitaire/Flow Line/Gluma Solid Bond) to 82.8 +/- 5.7% (Pertac II/Prompt L-Pop), for the cervical enamel margins from 10.1 +/- 5.2% (Dyract AP/NRC/P & B NT) to 72.7 +/- 7.9% (Pertac II/Prompt L-Pop), and for the lateral enamel margins of the approximal boxes from 4.8 +/- 2.3% (Dyract AP/NRC/P & B NT) to 53.9 +/- 6.8% (Pertac II/Prompt L-Pop). In the in-depth dye penetration investigation the mean dye penetration ranged from 0.2 +/- 0.2 mm (Point 4/Revolution/Optibond Solo Plus) to 1.7 +/- 0.2 mm (Pertac II/Prompt L-Pop) at the cementum margins. At the enamel margins only Pertac II/Prompt L-Pop and Solitaire 2/Gluma Solid Bond showed mean in depth dye-penetrations deeper than 0.1 mm. SIGNIFICANCE: Pertac II/Prompt-L-Pop showed a statistically significant (significance level alpha = 0.05, Wilcoxon test) higher percentage of dye-penetrated margins than most of the other restorative systems.

Compomers↗
PubMed1998

Acid-base reaction and fluoride release profiles in visible light-cured polyacid-modified composite restoratives (compomers).

OBJECTIVE: The aim of the study was to evaluate the extent of the acid-base reaction and F- release in Compoglass (Vivadent) and Dyract (Dentsply/DeTrey) restoratives. METHODS: For evaluation of the extent of the acid-base reaction, two groups of three specimens (7 mm x 5 mm x 1 mm) were prepared for each material. The first group was immersed in distilled water, while the second was kept in dark and dry conditions. Micro-MIR FTIR spectroscopy was used to determine the extent of the acid-base reaction on directly irradiated material surfaces immediately after irradiation and following water storage for 30 min, 3 d, 1, 2, 4, 8 and 12 wks. The in-depth extent of the acid-base reaction of the specimens stored in water for 4 weeks was studied by sequential spectra acquisition after removal of the uppermost 20, 70, 100, 240 and 400 microns layer by controlled grinding and 1 wk re-immersion in water of the 400 microns reduced specimens. For the F- release measurements, five disk-shaped specimens (10 mm x 1.5 mm) were prepared from each material and stored in distilled water. The amount of F- released for the storage periods reported above was measured using an ionometer with an F- electrode. Statistical analysis was performed by ANOVA, Scheffé's test and regression analysis. RESULTS: Storage in water promoted the development of an acid-base reaction on directly irradiated surfaces which reached a saturation point after 4 weeks. Depth profiling of the 4 wk immersed specimens revealed high salt concentration at the uppermost 100 microns layer. Re-immersion in water for 1 week of the 400 microns reduced specimens increased the salt concentration again at the uppermost region. Statistically significant differences were found in the acid-base rates and the in-depth salt yields between the materials (p < 0.05). The fluoride release after a 1 week initial "bursting" period was stabilized below 2 mg l-1 (p > 0.05) in both products. No positive correlation was found between acid-base reaction and fluoride release. SIGNIFICANCE: The development of a carboxylate-rich surface layer on polyacid-modified composite restoratives after water storage may explain their lower wear resistance compared with resin composites. The dynamic nature of these surfaces may provide several advantages regarding their interaction potential with hard dental tissues and their anticariogenic properties, but also some disadvantages concerning the quality of the surface texture obtained.

Alkalies↗
PubMed2000

Marginal integrity of large compomer Class II restorations with cervical margins in dentine.

OBJECTIVES: The aim of the present study was to investigate the marginal integrity of total-bond Dyract AP restorations in large Class II restorations with cervical margins in dentine. The efficacy of a new non-rinse conditioner and the effect of beveling the enamel margins were also studied. METHODS: Large MOD cavities with cervical margins located 1mm below the CEJ were prepared in 48 extracted human molars. Six groups (n=8) were filled using a total-bond technique with Spectrum TPH or Dyract AP or a sandwich technique with Dyract in combination with Spectrum TPH. For Dyract AP total-bond restorations, a new non-rinse conditioner was tested vs. a total-etch with 36% phosphoric acid in beveled and butt-joint cavities. After water storage for 21 days and thermocycling (2000x, 5-55 degrees C), replicas were produced for quantitative marginal analysis in the SEM. Afterwards, teeth were immersed in 0.5% basic fuchsin for 24h and dried. Percent dye penetration over the total margin length was analysed in three layers using a sequential grinding technique. Statistical analysis was performed with non-parametric tests and the Bonferroni correction for multiple comparisons at p<0.05. RESULTS: All restoration types showed microleakage. On cervical margins in dentine, Dyract AP restorations showed better marginal adaptation than Spectrum TPH total-bond restorations (marginal openings (MO), median 33.8 vs. 79.6%), but were inferior to Dyract/Spectrum TPH sandwich restorations (MO: 0. 0%). The non-rinse conditioner improved the marginal adaptation of Dyract AP restorations in dentine (MO: 4.7 vs. 38.4%, p=0.0206 for beveled cavities, 12.2 vs. 33.8%, p=0.0238, for butt-joint cavities) and yielded similar results in enamel margins provided that enamel margins were beveled. Beveling of enamel significantly reduced the occurrence of enamel microcracks. CONCLUSIONS: The use of a non-rinse conditioner in combination with Dyract AP may improve the marginal adaptation of Class II restorations compared to composite restorations. The sandwich technique with Dyract results in better marginal adaptation in cervical dentine compared to all other restorative techniques tested in this study. However, microleakage cannot predictably be prevented with the sandwich technique.

Acid Etching, Dental↗
PubMed2003

Effect of filler fraction on strength, viscosity and porosity of experimental compomer materials.

OBJECTIVE: The primary goal is to develop a self-cured polyacid-modified resin composite with good mechanical and rheological properties. To achieve such a goal, the aim of this study is to determine how volume filler fraction (VFF) affects mechanical properties and viscosities of such materials containing different filler volumes. METHODS: A series of self-cured polyacid-modified composites made from polyacid modified resins and TEGDMA, mixed with filler particles, were evaluated regarding compressive strength (CS), diametral compressive strength (DCS) and viscosity. The maximum filler content, which could be incorporated into the materials, was calculated from CS tests as well as from viscosity measurements using Mooney's equation. Porosity contents were also determined in an attempt to explain different failure behaviours. RESULTS: The CS values peaked at 18.9 vol.% filler particles and declined afterwards for self-cured polyacid-modified resin composites cured in air. Using photopolymerisation and barium filler in the polyacid-modified resin composites resulted in the highest CS and DCS values. The viscosity increased continuously with increased VFF. VFF results determined experimentally and with Mooney's equation at shear rates of 0.01, 0.1, 1.0, and 10.0 s(-1) revealed that the maximal filler fraction values were 54.9+/-1.8, 55.9+/-1.3, 56.3+/-0.9, and 56.8+/-0.8 vol.%, respectively. The largest porosity content occurred at a VFF value of 53 vol.% CONCLUSIONS: We conclude that an increase in filler fraction of the investigated experimental polyacid-modified resin composite materials above a certain value (20-30 vol.%) does not result in improved mechanical properties.

Analysis of Variance↗
PubMed2001

Fluoride release from glass-ionomer cements, compomers and resin composites.

The short and long-term fluoride release of 16 products (seven conventional glass-ionomers, five light-activated glass-ionomers, two polyacid-modified resin composites and two resin composites) commercialized as fluoride-releasing materials were measured. A potential link between the material type and its level of fluoride release was researched. The fluoride release was evaluated after different time intervals. Initial fluoride release from all materials was highest during the first 24 h and decreased sharply over the first week. Some groups of materials appeared to be significantly different after, respectively, 7 and 91 days. However, it was impossible to correlate the fluoride release of the materials by their type (conventional or resin-modified glass-ionomers, polyacid-modified resin composite and resin composite) except if we compared the products from the same manufacturer. The link between fluoride release and an acid-base reaction seems to be confirmed. The glass-ionomer composition (glass particles and polyacid's type, powder/liquid ratio) should have more influence on fluoride release than material type.

Acids↗
PubMed2005

Antibacterial activity of glass-ionomer cements, compomers and resin composites: relationship between acidity and material setting phase.

Agar diffusion testing was used with four different media to evaluate the antibacterial activity of six products (one conventional glass-ionomer cement (GIC), two light-activated glass-ionomers, two polyacid-modified resin composites and one resin composite) on Streptoccoccus mutans. Their respective antibacterial activities were also compared during and after setting. The relationship between product acidity and antibacterial activity was evaluated. All the GICs demonstrated antibacterial properties in contrast to the polyacid-modified resin composites and resin composite which did not shown any antibacterial effects. Vitrebond GIC exhibited higher antibacterial action, probably because of a cytotoxic photo-initiator diphenyliodoniumchloride. A direct relationship between material acidity and growth inhibition of S. mutans was observed.

Anti-Bacterial Agents↗