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PubMed2002

Comparison of post-gel shrinkage strains in light-polymerized composite resins.

STATEMENT OF PROBLEM: Polymerization shrinkage is associated with light-polymerized and polyacid-modified composites. PURPOSE: This in vitro study compared the polymerization shrinkage of a light-polymerized hybrid composite, a posterior composite, and a polyacid-modified composite. MATERIAL AND METHODS: Five disk-shaped specimens (1 cm in diameter and 2 mm in thickness) were prepared in a mold from each of the following test materials: a light-polymerized hybrid composite (3M Valux Plus), a posterior composite (Filtek P60), and a polyacid-modified composite (Dyract AP). The hybrid composite served as the control material. A linear strain gauge was placed at the center of each specimen. After the specimens were light-polymerized for 60 seconds under 400-mW/cm(2) light intensity, microstrains were recorded with the strain indicator continuously every 4 seconds for 120 seconds. The data were evaluated with 1-way analysis of variance (P<.05) followed by a post hoc least significant difference test. RESULTS: During the first 20 seconds of light polymerization, all materials exhibited tensile strains between 6 and 55 mu epsilon that quickly converted into compressive strains and continued rising after the light source was removed. The strains for all materials increased at a declining rate until they reached a constant level between 148 and 180 seconds. The polymerization shrinkage recorded for Filtek P60 was the lowest (-190.56 mu epsilon), followed by 3M Valux Plus (-303.94 mu epsilon) and Dyract AP (-345.64 mu epsilon) (P<.05). The dimensional change between Filtek P60 and Dyract AP and between Filtek P60 and 3M Valux Plus was significant (P=.001). However, the difference between Dyract AP and 3M Valux Plus specimens was not significant (P=.208). CONCLUSION: Within the limitations of this study, the light-polymerized posterior composite tested demonstrated less polymerization shrinkage than the polyacid-modified and hybrid composites tested. Polymerization shrinkage velocity significantly affected the magnitude of strains.

Analysis of Variance↗
PubMed2000

Interfacial adaptation of a Class II polyacid-modified resin composite/resin composite laminate restoration in vivo.

The aim of this in vivo study was to evaluate the interfacial adaptation of Class II resin composite open sandwich restorations with a polyacid-modified resin composite as a stress-absorbing layer (PMRC/RC). Twenty Class II box-shaped, enamel-bordered cavities were prepared in 10 premolars scheduled to be extracted for orthodontic reasons. An open PMRC/RC sandwich restoration was placed in 1 of the cavities of each tooth. The first layer, PMRC, in the proximal box extended to the periphery in the cervical part of the cavity. The following RC layers were placed with a horizontally incremental technique. The PMRC was excluded from the control cavity. The teeth were extracted after 1 month and the interfacial adaptation of the restorations was studied with quantitative scanning electron microscope analysis using a replicate technique. Gap-free interfacial adaptation was observed for the PMRC/RC and RC restorations in cervical enamel in 97% and 73%, respectively (P = 0.006). The gap-free scores for dentin were 87% and 64%, respectively (P = 0.022). Excellent interfacial adaptation was observed in both groups for the occlusal enamel 99% and 100%, respectively. The adaptation to occlusal enamel for the direct resin composite restorations was significantly better than to dentin or cervical enamel. A higher frequency of enamel fractures was observed parallel to the cervical margins compared to the occlusal. No dentin fractures were observed in the experimental groups. The PMRC/RC sandwich technique showed a statistically significant improved interfacial adaptation to dentin and cervical enamel in Class II enamel-bordered cavities. The clinical significance of the differences has to be evaluated.

Absorption↗
PubMed2002

Placement and replacement of restorations in primary teeth.

This practice-based study aimed to record the use of restorative materials, the type of restoration by class, and the reason for and the age of failed restorations in primary teeth by means of a survey of placement and replacement of restorations in 1996 and 2000/2001. Written alternative criteria for placement and replacement of restorations were provided for the participating clinicians. Details on 2281 restorations showed that primary caries was the main reason for inserting restorations in primary teeth. Replacements of failed restorations represented 14% of the fillings (n = 2040) in 1996 and 9% in 2000/2001 (n = 241). More than 80% or the fillings in primary teeth were of tooth-colored material, predominantly of the light-cured type. About 50% of failed amalgam and glass ionomer-type restorations were replaced due to secondary caries. The median age of amalgam restorations (3 years) was significantly higher than that of tooth-colored restorations (2 years). Any possible advantage of a cariostatic effect of glass ionomer-type materials is apparently annulled by their short longevity compared with amalgam.

Child↗
PubMed2002

Changes in expansion and mechanical strength during water storage of a traditional and three modified resin composites.

Four types of resin composites (Dyract AP (DYR), Definite (DEF), Ariston pHc (ARI), and Spectrum TPH (SPE)) were tested after water storage for up to 180 days. The test parameters were flexural strength, flexural modulus, and marginal gaps at fillings in cylindrical cavities. The cavity tests were performed in two ways. One series of filings was finished shortly after curing and the maximal gaps were followed with time during water storage. Another series was finished immediately before gap size measurement and after water storage for various periods. Absence of or reduced gap sizes at 180 days compared to 1 h or 1 day was obsenred for all materials and with both methods. At 180 days, DYR and ARI showed significantly smaller gap sizes than those observed with DEF and SPE. No significant differences in flexural strength were observed when means at 180 days were compared to those observed at 1 day. DEF, ARI, and SPE showed a significant increase in flexural moduli at 180 days compared to 1 day, while DYR showed none. It is concluded that fillings made of Dyract AP or Ariston pHc may show absence of or very small gap sizes between filling and cavity wall after 6 months and with no significant reduction in mechanical strength.

Analysis of Variance↗
PubMed2003

Flexural strength and modulus of a novel ceramic restorative cement intended for posterior restorations as determined by a three-point bending test.

The aim of this study was to compare a new restorative cement intended for posterior restorations, Doxadent, with other types of tooth-colored materials as regards flexural strength and flexural modulus. The new restorative material consists mainly of calcium aluminate. Four hybrid resin composites, one polyacid-modified resin composite, one resin-modified glass ionomer cement, one conventional glass ionomer cement, one zinc phosphate cement, and an experimental version as well as the marketed version of Doxadent were investigated. Flexural strength and flexural modulus were tested according to ISO standard 4049 and determined after 1 d, 1 week, and 2 weeks. Together with the zinc phosphate cement, Doxadent had the lowest flexural strengths (13-22 MPa). The strongest materials were the resin composites and the polyacid-modified resin composite (83-136 MPa). The highest flexural modulus was found for Doxadent (17-19 GPa). The flexural strength of Doxadent decreased significantly from 1 week to 2 weeks, while flexural modulus remained unchanged. The other materials reacted in different ways to prolonged water storage. It can be concluded that the restorative cement Doxadent had significantly lower flexural strength and significantly higher flexural modulus than today's materials used for direct posterior restorations.

Aluminum Compounds↗
PubMed1998

Shear bond strengths of ceramic brackets bonded with different light-cured glass ionomer cements: an in vitro study.

The purpose of this study was to evaluate the shear bond strengths of four light-cured glass ionomer cements used for direct bonding of ceramic brackets, and to compare the results with a two-paste chemically-cured composite resin. Two commercially available polycrystalline ceramic brackets, with either chemically or mechanically retentive bracket bases, were evaluated. The brackets were bonded to 100 freshly extracted bovine incisors, and, after storage in tap water at room temperature for 24 hours, they were subsequently tested in a shear mode using a universal testing machine. The maximum bond strength and the site of bond failure were recorded. With the mechanically retentive base, Fuji Ortho LC produced the highest bond strength (18.50 MPa), which was not significantly different from the values achieved with Concise (14.88 MPa) (P > 0.1) and Photac Bond (13.86 Mpa) (P = 0.1). The lowest bond strength was provided by locomp A20 (5.23 MPa). With the chemically retentive base, the highest bond strength was measured with Concise (29.27 MPa), which was significantly (P < 0.01) higher than the values for Photac Bond (16.27 MPa) and Fuji Ortho LC (13.48 MPa). Again locomp A20 produced the lowest bond strength (3.21 MPa). Three cements (Dyract Ortho, locomp A20 and Fuji Ortho LC) provided higher shear bond strengths with the mechanical retention system, whereas Concise and Photac Bond gave higher strengths with the silane-treated bracket bases. However, the strengths were statistically significantly different only for locomp A20 (P = 0.001) and Concise (P = 0.001). With the mechanically retentive base, Dyract Ortho and locomp A20 failed at the enamel-adhesive interface, whereas Photac Bond and Concise debonded at the bracket-adhesive interface. Fuji Ortho LC failed at both, the bracket-adhesive (40 per cent) and the adhesive-enamel (60 per cent) interface. With the chemically retentive base, all the adhesives failed at the enamel-adhesive interface. Only one bracket fracture occurred in this study, and no enamel damage was detected.

Acrylic Resins↗
PubMed1998

Electrothermal bonding: shear bond strength of orthodontic brackets after two weeks.

Electrothermal bonding is based on acceleration of the setting reaction of a bonding: resin by the selective application of heat to the orthodontic bracket through the passage of a low voltage electric current. The purpose of this study was to compare the shear bond strength of nine resins comprising chemically-cured, light-cured, and glass ionomer types, 14 days after electrothermal and conventional bonding. Mean shear and bond strengths ranged from a low of 7.4 MPa for Sequence (electrothermally bonded) to a high of 15.4 MPa Concise (control). There was no statistically significant difference between the electrothermal and conventional bonding methods. All the resins produced bond strengths adequate for clinical orthodontics at 14 days.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2000

An ex vivo assessment of resin-modified glass ionomer bonding systems in relation to ceramic bracket debond.

This ex vivo study assessed three new resin-modified glass ionomer cements (Fuji ORTHO LC, Vitremer, and Dyract-Cem) in relation to ceramic bracket removal. It was hypothesized that the use of these cements would facilitate bracket removal and eliminate debond complications Eighty extracted premolar teeth were divided into four groups of 20 teeth and bonded with Intrigue brackets using each of the resin-modified cements (groups 1, 2, and 3), the control group 4 was bonded with Concise chemically-cured adhesive. The teeth were debonded by applying a shear load using an Instron universal testing machine. The mean force to debond was calculated for each group and each tooth was examined under the stereomicroscope to record the site of bond failure and the Adhesive Remnant Index (ARI). The results showed that the resin-modified cements were very effective at eliminating ceramic bracket debond problems. Bracket fracture was eliminated compared with a 40 per cent fracture rate with the control and the ARI scores were all reduced. The elimination of debond problems appears to be related to the significantly reduced (P < 0.001 using ANOVA and Tukey tests) mean and maximal debond forces compared with the control.

Acrylic Resins↗
PubMed2000

Penetration of the pulp chamber by bleaching agents in teeth restored with various restorative materials.

It is thought that externally applied bleaching agents may penetrate into the pulp chamber. This study was conducted to evaluate the diffusion of peroxide bleaching agents into the pulp chamber of teeth restored with various restorative materials. Sixty-five human extracted anterior maxillary teeth were separated into the 13 groups containing 5 teeth. Five teeth (control group) were not subjected to any cavity preparation and restoration. Standardized class V cavities were prepared in the other 60 teeth and restored using composite resin (Charisma), polyacid modified composite resin (Dyract), or resin-modified glass ionomer cement (Vitremer). All teeth were sectioned 3 mm apical to the cementoenamel junction to remove the intracoronal pulp tissue, and the pulp chamber was filled with acetate buffer to absorb and stabilize any peroxide that might penetrate. Vestibular crown surfaces of teeth in the experimental groups were subjected to four different bleaching agents for 30 min at 37 degrees C, whereas the teeth in the control groups were exposed only to distilled water. Then the acetate buffer solution in the pulp chamber of each tooth was removed, and the pulp chamber of each tooth was rinsed with 100 ml of distilled water twice. Leukocrystal violet and enzyme horseradish peroxidase were added to the mixture of the acetate buffer and rinse water. The optical density of the resulting blue solution was determined spectrophotometrically and converted into microgram equivalents of hydrogen peroxide. Higher hydrogen peroxide concentrations resulted in a higher pulpal peroxide penetration. The highest pulpal peroxide penetration was found in resin-modified glass ionomer cement groups, whereas composite resin groups showed the lowest pulpal peroxide penetration.

Acetates↗
PubMed2002

Intracoronal sealing ability of two dental cements.

The purpose of this study was to compare the efficacy of sealing the coronal 2-mm of the root canals versus covering the entire pulpal floor with one of two dental-resin cements (Principle or C&B Metabond). Sixty-two molars with the occlusal half of the crowns and the apical half of the roots removed were used. Each canal was enlarged by using a #3 Gates Glidden bur and obturated with unsealed gutta-percha cones. The teeth were randomly assigned to four groups, each containing 15 teeth, plus a negative and a positive control. In group 1, 2 mm of Principle were placed over the entire pulpal floor. In group 2, Principle was placed 2 mm into each canal orifice. Groups 3 and 4 were the same as groups 1 and 2, except C&B Metabond cement was used. After the cement set, the gutta-percha was removed and the integrity of the seal was tested by fluid filtration at a pressure of 20 cm H2O at 1 h and at 1, 2, and 4 weeks. The data were analyzed by a three-way ANOVA and the Student-Newman-Keuls tests at alpha = 0.05. The controls behaved as expected. Results showed that there were no statistically significant differences among the materials used or the location (p > 0.05), but there was a significant difference with respect to time. Principle leaked significantly more than C&B Metabond at 1 h (p < 0.05), but the seal became tighter over time. C&B Metabond leaked less early (p < 0.05) but increased in leakage at 4 weeks. Both materials sealed well over the 4-week study. Principle was easier to use, and sealing the entire pulpal floor was easier than sealing only the canal orifice.

Analysis of Variance↗
PubMed2002

An assessment of microbial coronal leakage of temporary filling materials in endodontically treated teeth.

This in vitro study evaluated the microbial leakage of Cavit, IRM, and Dyract when used as temporary filling materials after root canal treatment. The degree of coronal leakage was assessed by using a microbiological marker consisting of Streptococcus faecalis and Candida albicans. For each of the two organisms, a set of 15 maxillary premolars were prepared chemomechanically and obturated with thermoplasticized gutta-percha. A 3.5-mm thick layer of one of the three temporary filling materials was inserted in the access cavities of the teeth from each group (each group was compromised of five teeth). The control teeth (four positive and four negative) lacked any filling material over the gutta-percha, whereas the orifice and the apical foramen of the negative control were completely sealed with nail polish. Each tooth was placed in a well of a 24-well tissue culture plate and embedded in trypticase soy broth and 0.5% Bactoagar. An organism suspension was inoculated in the access cavity, and microbial penetration was detected as an increase in turbidity of the broth. At the end of 30 days, the results showed that all positive control teeth leaked within 1 week, whereas those that served as negative control remained uncontaminated throughout the test period. With both organisms, IRM started to leak after 10 days, whereas Cavit and Dyract leaked after 2 weeks.

Analysis of Variance↗
PubMed2004

Effect of dentin on the antibacterial activity of dentin bonding agents.

Dentin bonding agents with antibacterial effects may inhibit secondary caries formation and pulp inflammation by eliminating residual bacteria in and on dentin. Therefore, the antibacterial effects of Prime & Bond NT (PB), Prime & Bond NT without fluoride (PBNF), Gluma Comfort Bond (GL), ABF, Xeno CF II (XE), 2-hydroxyethyl methacrylate (HEMA), triethylene glycol dimethacrylate (TEG-DMA), and 0.2% chlorhexidine were tested against Streptococcus mutans, S. sobrinus, and Lactobacillus acidophilus using the agar-diffusion method with and without bovine-dentin disks (200 microm and 500 microm thickness) placed between the bacteria and the test substances. Without dentin, ABF Primer showed growth inhibition for all bacterial strains. XE inhibited S. mutans and S. sobrinus, and PB S. sobrinus. ABF Bonding inhibited L. acidophilus. PBNF, HEMA, and TEGDMA did not have any antibacterial effects. Dentin disks of 500 microm thickness reduced the inhibitory effect of chlorhexidine to 23% to 54% compared with direct application. ABF Primer (nonpolymerized) produced inhibition zones against all tester strains regardless of dentin disks interposed or not. XE (against S. mutans and S. sobrinus) and PB (against S. sobrinus) did not produce any inhibition zones on 200 microm thick dentin. After polymerization, the ABF system did not inhibit bacterial growth on 200 microm thick dentin disks. A dentin barrier reduces significantly the antibacterial activity of chlorhexidine and dentin bonding agents.

Animals↗
PubMed2005

Shear bond strengths of two composite core materials after using all-in-one and single-bottle dentin adhesives.

PURPOSE: The purpose of this study was to compare the shear bond strengths of 2 composite core materials after using all-in-one and single-bottle dentin bonding materials. MATERIAL AND METHODS: The occlusal surfaces of 100 extracted, intact human third molars were ground to expose a flattened area of dentin and polished with 600-grit silicon carbide paper. Specimens were divided into 5 main groups (n= 20). Three all-in-one (AQ Bond, One-Up Bond, Xeno-CF Bond) and 2 single-bottle adhesives (Single Bond, One-Step Plus) were used. Each group was further divided into 2 subgroups. Ti-Core and Built-it F.R. core materials were applied using a translucent plastic ring (diameter: 3 mm, height: 5 mm). After storage in 37 degrees C water for 24 hours, shear bond strengths were measured using a Universal testing machine with a crosshead speed of 0.5 mm/min. Debonded dentin surfaces were examined with SEM. Two-way analysis of variance (ANOVA) and multiple comparison (Tukey) tests were used for statistical analysis of data. RESULTS: Two-way ANOVA revealed that the type of core material did not significantly influence the shear bond strength (p > 0.05), whereas there were significant differences in shear bond strength among the types of bonding agents (p < 0.0001). Shear bond strengths for single-bottle adhesive systems were significantly higher than those for all-in-one adhesive systems (p < 0.05). Furthermore, the interaction of these 2 parameters was not significant (p > 0.05). The fracture modes were predominantly adhesive for all-in-one adhesives and cohesive for single-bottle adhesives. CONCLUSION: Bonding of composite core materials with the newly developed all-in-one dentin adhesives produced lower shear bond strengths as compared with single-bottle adhesives.

Analysis of Variance↗
PubMed2004

Surface wear on cervical restorations and adjacent enamel and root cementum caused by simulated long-term maintenance therapy.

BACKGROUND: In an in vitro study, the surface wear on cervical restorations and adjacent enamel and root cementum caused by different tooth-cleaning methods in simulated long-term therapy was investigated. METHODS: Cervical restorations of amalgam (Oralloy), modified composite resin (Dyract), glass-ionomer cement (ChemFill Superior), and composite (Tetric) were instrumented by POL (polishing), CUR+POL (curette and polishing), US+POL (ultrasonic device with polishing) and the polishing agents Cleanic and Proxyt in a computer-controlled test bench. Treatment time corresponding to a real-time period of 5 or 10 years. Substance loss from instrumented surfaces was measured with a digital gauge. A three-way anova was used in the statistical evaluation. RESULTS: The results showed that POL led to slight substance loss, which was greater using Cleanic (27 microm) than Proxyt (5 microm). CUR+POL produced a significantly greater substance loss than did US+POL, with 186 microm versus 35 microm on glass-ionomer cement, respectively, and 123 microm versus 18 microm, respectively, on root cementum, followed by composite (111 microm versus 27 microm, respectively), polyacid modified composite resin/compomer (89 microm versus 36 microm), amalgam (75 microm versus 19 microm), and enamel (32 microm versus 23 microm). CONCLUSIONS: As opposed to the use of US+POL or POL, substance loss on cervical restorations and especially root cementum must be expected to result from tooth-cleaning during long-term maintenance treatment using CUR+POL.

Analysis of Variance↗
PubMed1996

Comparison of two- and three-body wear of glass-ionomers and composites.

The two-body and three-body wear of glass-ionomers (GIC), visible light cured glass-ionomers (VLC-GIC), and composites were compared. The wear simulations were performed for the two-body wear in an artificial mouth and for the three-body wear with the so-called ACTA machine. The tested materials were different conventional glass-ionomers, light cured glass-ionomers, composites, and amalgam. The wear rates of 8 specimens of each material for the two-body and 16 for the three-body wear test were compared. After 10(5) cycles with each testing device, the wear shapes were measured. All measurements were related to the wear rate of amalgam. For the two-body wear method, the worn materials were qualitatively judged by scanning electron microscopy. The two different wear testing methods lead to similar results with slight differences in ranking. Amalgam showed the lowest wear rates with both methods. Photac Fil, a newly developed VLC-GIC, showed dramatically lower wear resistance than composites and conventional GIC with both methods. Further investigations are necessary to identify the material-specific parameters influencing the wear behaviour of a material in relation to different wear testing methods.

Acrylic Resins↗
PubMed2005

Color stability of resin-based filling materials after aging when cured with plasma or halogen light.

The influence of curing devices and curing times on the color stability of filling resins was investigated by measuring the CIE-Laboratory-values after performing dry storage, water storage, and a Suntest (EN ISO 7491). Eight samples each of Charisma (CH), Durafill (DU), Definite (DE), and Dyract AP (DY) were light cured by using Translux Energy (TE) for 20, 40 or 60 s, or by using Apollo 95E (AP) for 3, 10 or 20 s. Minor color changes occurred for all dry stored materials, devices and curing times. The TE-cured, water-stored samples behaved similarly to the dry-stored ones, but the samples cured with AP revealed very strong color changes, mainly because of a drastic bleaching process. The bleaching of DU was significantly less than that of the other materials, but a strong white shift occurred. CH, DE, and DU showed very little (and even acceptable) discolorations after the Suntest when TE-cured. DY showed a drastically discoloration. All samples cured using AP drastically bleached and shifted to white for DU and DY but to dark for DE. In conclusion, the extent of discoloration depends on (i) the material, (ii) the test method, (iii) curing time, and (iv) the curing device. The halogen light-cured samples performed best.

Color↗
PubMed1999

Effects of air abrasion and acid etching on the microleakage of preventive Class I resin restorations: an in vitro study.

PURPOSE: To evaluate the effects of air abrasion, acid etching, and the combination of both procedures on the microleakage of preventive Class I resin restorations. MATERIALS AND METHODS: Eighty-four extracted human molar teeth were randomly assigned to seven groups with 12 teeth each. Occlusal fissures were opened with a diamond bur and etched with phosphoric acid (groups I and VI); prepared with a diamond bur without etching (group VII); air abraded with the KCP 1000, using 50-micron aluminum oxide particles without etching (group II), and with phosphoric acid etching (group III); or air abraded with 27-micron aluminum oxide particles without etching (group IV), and with phosphoric acid etching (group V). Preparations were filled with a low-viscosity resin composite (Liquicoat, groups I to V) or with a low-viscosity polyacid-modified resin composite (PrimaFlow, groups VI and VII). Six teeth in each group were thermocycled (5 degrees-55 degrees C, 2500 cycles). Dye penetration (methylene blue) was evaluated in ordinal scale. RESULTS: The number of non-thermocycled and thermocycled specimens revealing no microleakage was as follows: group I, 6 and 1; group II, 2 and 2; group III, 4 and 3; group IV, 0 and 0; group V, 1 and 0; group VI, 3 and 2; and group VII, 0 and 0, respectively. No significant differences existed between the thermocycled specimens and non-thermocycled specimens, except within group I. CLINICAL SIGNIFICANCE: Results indicated that (1) air-abrasion treatment with 27-micron particles is less effective in preventing microleakage compared to 50-micron particles, (2) air abrasion should be combined with acid etching to reduce microleakage of preventive Class I resin restorations, and (3) acid etching significantly reduces microleakage of the low-viscosity polyacid-modified resin composite in preventive Class I restorations.

Acid Etching, Dental↗