Inhibition of artificial secondary caries in root by fluoride-releasing restorative materials

This investigation evaluated the fluoride-releasing properties of various fluoride-releasing restorative materials, including resin-modified glass-ionomer cements (Fuji ionomer TypeII LC, Photac-Fil Aplicap, Vitremer), compomers (Ionosit FIL, Compoglass, Dyract) and fluoride-releasing resin composites (Heliomolar radiopaque, Degufill mineral). The study also estimated the effects of those materials on the inhibition of artificial secondary caries around restorations using a bacterial caries-inducing system. The amount of fluoride released from the materials in deionized water was measured every one week for 10 weeks. Class V cavities with the gingival margin located in the root were prepared in extracted human premolars and restored with each of the materials. The restored teeth were incubated in the bacterial artificial caries chamber, and the artificial lesion created around the restoration was observed microradiographically. The resin-modified glass-ionomer cements released the largest amount of fluoride and created a thick radio-opaque zone in the artificial lesion along the restoration-dentin interface. These results indicated that the fluoride-releasing restorative materials have the potential to inhibit secondary caries formation around restorations. Resin-modified glass-ionomer cements presented a particularly strong effect, compared with compomers and fluoride-releasing resin composites.     

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.     

Comparison of Wear-Resistance of Class V Restorative Materials

ABSTRACT: Compomers and resin-modified glass ionomers have been developed to improve the physical properties of traditional glass ionomer cements. This project compared the toothbrush wear-resistance of three compomers (Compoglass, Dyract, Hytac) and three resin-modified glass ionomer restorative materials (Fuji II LC, Photac-Fil, Vitremer) to that of two resin-based composites (Herculite XRV, Silux Plus). Specimens (n = 7) were prepared according to manufacturers' instructions and stored in a humidor for 48 hours prior to testing. The specimens were subjected to 120,000 strokes at 1.5 Hz, using a brush-head force of 200 g on a Manly V-8 cross-brushing machine. The slurry contained a 50:50 (w/w) mixture of toothpaste and deionized water. Abrasion-resistance was calculated by measuring specimen mass-loss prior to and subsequent to brushing. The data were analyzed using a one-way analysis of variance (ANOVA) and the Tukey-Kramer post-hoc test. Significant differences ( p ±.0001) in mass-loss were found, and loss ranged from 0.013 ± 0.003 g (Hytac) to 0.061 ± 0.009 g (Compoglass). No correlation ( p = .959) between wear-resistance and experimentally determined filler content existed. This study showed that all but one hybrid resin-ionomer type material exhibited a resistance to toothbrush wear that was as good as or better than that of the two traditional resin-based composite materials.     

Comparison of wear-resistance of Class V restorative materials.

Compomers and resin-modified glass ionomers have been developed to improve the physical properties of traditional glass ionomer cements. This project compared the toothbrush wear-resistance of three compomers (Compoglass, Dyract, Hytac) and three resin-modified glass ionomer restorative materials (Fuji II LC, Photac-Fil, Vitremer) to that of two resin-based composites (Herculite XRV, Silux Plus). Specimens (n = 7) were prepared according to manufacturers' instructions and stored in a humidor for 48 hours prior to testing. The specimens were subjected to 120,000 strokes at 1.5 Hz, using a brush-head force of 200 g on a Manly V-8 cross-brushing machine. The slurry contained a 50:50 (w/w) mixture of toothpaste and deionized water. Abrasion-resistance was calculated by measuring specimen mass-loss prior to and subsequent to brushing. The data were analyzed using a one-way analysis of variance (ANOVA) and the Tukey-Kramer post-hoc test. Significant differences (p < .0001) in mass-loss were found, and loss ranged from 0.013 +/- 0.003 g (Hytac) to 0.061 +/- 0.009 g (Compoglass). No correlation (p = .959) between wear-resistance and experimentally determined filler content existed. This study showed that all but one hybrid resin-ionomer type material exhibited a resistance to toothbrush wear that was as good as or better than that of the two traditional resin-based composite materials.     

Surface roughness of aesthetic restorative materials: an in vitro comparison.

The purpose of this study was to compare the surface roughness of three types of aesthetic restorative material. Six standard samples of two brands of each type of material were prepared namely: hybrid composites (Prodigy, Z100), compomers (Compoglass F, Hytac Aplitip) and glass ionomer cements (Photac-Fil, Vitremer) in a perspex mould (N = 36). Upper and lower surfaces were covered with Mylar strips which, in turn, were covered with glass slides and compressed to express excess material. After light curing, specimens were stored in distilled water for 14 days. Thereafter, one side of each specimen was polished sequentially with medium, fine and super fine Soflex discs (treatment). Untreated surfaces served as controls. All surfaces were examined with Talysurf and the surface roughness (Ra) of each specimen was recorded. Three measurements were made of each specimen. A 4-way ANOVA and Tukey's Studentised range test were used to analyse the data. Statistically significant effects were found for both type of material (P = 0.0001) and for treatment process (P = 0.0065). Among unpolished specimens: Compoglass F is significantly rougher than Vitremer, Z100, Prodigy and Hytac Aplitip, and compomers are significantly rougher than hybrids. Among polished specimens: Photac-Fil is significantly rougher than Z100 but does not differ from Compoglass F, Vitremer, Prodigy and Hytac Aplitip, and glass ionomers are also significantly rougher than hybrids. The smoothest surface is obtained when curing materials against a Mylar strip.     

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.     

Fluoride release and uptake capacities of fluoride-releasing restorative materials

Many fluoride-releasing dental materials are being sold on the basis of their cariostatic properties. However, the amount fluoride release of these materials is still uncertain. This study investigated the fluoride release and uptake characteristics of four flowable resin composites (Heliomolar Flow, Tetric Flow, Wave, Perma Flo), one flowable compomer (Dyract flow), one conventional glass ionomer cement mixed with two different powder/liquid ratios (ChemFlex Syringeable and ChemFlex Condensable), one packable resin composite (SureFil), one ion-releasing composite (Ariston pHc) and one resin-modified glass ionomer cement (Vitremer). Seven discs (6-mm diameter and 1.5-mm height) were prepared for each material. Each disc was immersed in 3.5 ml of deionized water within a plastic vial and stored at 37 degrees C. The deionized water was changed every 24 hours and the release of fluoride was measured for 30 days. At the end of this period, the samples were recharged with 2 ml of 1.23% acidulated phosphate fluoride (APF) gel for four minutes. Then, all samples were reassessed for an additional 10 days. The fluoride release of all samples was measured with a specific fluoride electrode and an ionanalyzer. Statistical analyses were conducted using two-way repeated measure ANOVA and Duncan's multiple range tests. For all tested materials, the greatest fluoride release was observed after the first day of the study (p<0.01) but gradually diminished with time. During the test period, Tetric Flow released the lowest amount of fluoride; however, no statistically significant difference was found from Wave and Heliomolar Flow (p>0.05). Ariston pHc released the highest amount of fluoride, followed by ChemFlex Syringeable, Vitremer and ChemFlex Condensable. There were statistically significant differences among these materials (p<0.05). Fluoride release of all materials were significantly increased after the first day following refluoridation and Ariston pHc released the greatest among all materials (p<0.01). At the end of two days of refluoridation, the fluoride release rate for each material dropped quickly and stabilized within three days.     

一种复合体和四种树脂化玻璃离子水门汀的氟离子释放测定

目的 比较１种复合体和４种树脂化玻璃离子水门汀在水中释放氟离子的能力。方法 用氟离子选择电极，分别在第１、７、３０ｄ直径２５３ｄ，５种材料固化后标本浸泡训的氟离子浓度。结果 除复合体以外的所有材料，均显示了高的初期氟离子释入并急剧下降，然后缓慢下降。结论 复合体释放的氟离子比树脂化玻璃离子水门汀少。对于龋病高发的患者，选择高氟离子释放的树脂化玻璃离子水门汀材料较好。     

In vitro microleakage of glass-ionomer composite resin hybrid materials.

The purpose of this study was to evaluate the microleakage of six glass-ionomer composite resin hybrid materials compared with a glass-ionomer cement and a composite resin. Standardized class 5 dentin cavities were prepared on root surfaces of 240 extracted human teeth that were randomly assigned to eight groups and restored using the following restorative systems: (I) Vitremer, (II) Compoglass, (III) Photac-Fil Aplicap, (IV) Variglass, (V) Dyract, (VI) Fuji II LC, (VII) Ketac-Fil Aplicap, and (VIII) Z100. The teeth were thermocycled, placed in a 2% methylene blue solution, and sectioned with diamond disks. Dye penetration was scored on a scale of 0-3. Results showed no significant differences among groups VIII, IV, I, V, VI, III, and II. There were also no significant differences among groups VI, III, II, and VII.     

Effect of 1.23 percent APF gel on fluoride-releasing restorative materials

This study evaluated the effect of a 1.23 percent APF gel on the surface morphological characteristics and surface roughness of one high-viscosity (Fuji IX GP), three polyacid-modified resin-based composites (Dyract AP, F2000 and Compoglass F) (PMRC), and two resin-modified glass-ionomer cements (Vitremer and Fuji II LC). A microfilled nonfluoridated resin-based composite (Silux Plus) was used as a control. All materials were handled according to the manufacturers' instructions. The fluoride gel used in the study was a 1.23 percent acidulated phosphate fluoride gel (APF) (Nupro APF). The specimens were repeatedly exposed to the APF gel with cotton applicators for a period that simulated the equivalent of 4 yrs (1 min/6 mo) under prophylactic fluoride treatment. Average surface roughness (Ra) of the control and treated specimens was measured. Three separate Ra measurements along the direction of rotation of the finishing and perpendicular to the finishing direction and edge of the mold were made for each specimen surface. In each group, specimens with Ra closest to the mean were removed from the molds, sputter-coated with gold and examined using a scanning electron microscope. The results showed that all tested materials, except Vitremer, displayed increased surface roughness values following APF treatment. However, this was not statistically significant for Compoglass F, Vitremer and Fuji II LC. Among PMRC materials, F2000 displayed the highest Ra average value, although the differences between F2000 and Dyract AP and of Compoglass F and Dyract AP was not statistically significant. Comparisons of the Ra values between Silux Plus and the other test materials revealed statistically significant differences except for Dyract AP and Compoglass F. No statistically significant difference was found between the Ra values of Vitremer and Fuji II LC following APF treatment. Among all groups, Fuji IX GP displayed the highest surface roughness.     

Fluoride release and antibacterial properties of new-generation tooth-colored restoratives

The aim of this study was to compare the amounts and pattern of fluoride release and antibacterial properties of new-generation restoratives over a 35-day period. Materials evaluated included fluoride-releasing composites (Tetric, Experimental X), compomers (Dyract, Compoglass), and a resin-modified glass-ionomer cement (Fuji II LC). A conventional glass ionomer (Fuji II Cap) was used as a control for fluoride-release testing. Five samples of each restorative material were evaluated for daily fluoride release over a 35-day period by means of ion chromatography. Ranking of materials from least to greatest total fluoride release over 35 days was as follows: Tetric < Experimental X < Dyract < Fuji II LC < Compoglass < Fuji II Cap. Fuji II Cap had significantly greater fluoride release than all other materials evaluated. Fuji II Cap, Fuji II LC, and Compoglass had similar patterns of fluoride release characterized by a high initial release that was many times that released later. The fluoride-releasing composites evaluated stopped releasing fluoride by day 14. Antibacterial testing was conducted using the agar diffusion inhibitory test. Five samples of each restorative were assessed at baseline and weekly intervals up to 35 days. The microorganisms used were Lactobacillus casei, Streptococcus mutans, and Streptococcus sobrinus. IRM, a zinc oxide/eugenol cement, was used as the baseline control. None of the restorative materials evaluated affected the growth of L casei, S sobrinus, or S mutans at all time periods including baseline, where fluoride was detected in the agar beneath the specimen disks. There was no correlation noted between fluoride-release potential and antibacterial properties.     

Fluoride release from restorative materials coated with an adhesive

The retention of both fluoride resins and resin-modified glass ionomer cements to dental tissues can be improved by the association of an adhesive system which promotes the bonding between the resin component and dentin, forming a hybrid layer. The purpose of this investigation was to evaluate if the presence of the adhesive, being part of the hybrid layer composition, interfered with the fluoride released to tooth tissues. The restorative materials studied were: Vitremer (3M), Heliomolar (Vivadent) and Z100 (3M) using an adhesive application (Scotch Bond MultiPurpose Plus--3M). Ten discs of each material were prepared: 5 were covered with the adhesive and 5 were not. The discs were immersed in individual flasks containing artificial saliva which was changed daily. Fluoride release was measured at days 1, 5, 10, 15 and 20 by a fluoride combined electrode (9609 BN--Orion) coupled to an ion analyzer (SA-720 Procyon). One-way ANOVA and the Student-Newman-Keuls test were applied to compare the materials. The results showed that the use of a dental adhesive significantly decreased the fluoride release of Vitremer and reduced the fluoride release of Heliomolar to undetectable levels with the methodology used.     

Effects of daily fluoride exposures on fluoride release by glass ionomer-based restoratives

It is well documented that glass ionomer cements absorb and release fluoride following single fluoride exposures. This study examined fluoride release among three glass ionomer-based restorative materials following multiple daily exposures to three topical fluoride regimens. Using a Delrin mold, 32 cylindrical specimens, each of a glass ionomer (Ketac-Fil), resin-modified glass ionomer (Photac-Fil) and polyacid-modified resin (Dyract AP) were created. Each specimen was subjected to one of four daily treatments (n = 8): (1) no fluoride treatment (control); (2) application of a fluoride dentifrice (1000 ppm) for one minute once daily; (3) application of the same dentifrice for one minute twice daily; (4) the same regimen as (3), plus immersion in a 0.05% sodium fluoride (NaF) mouth rinse (225 ppm) for one minute immediately following the second dentifrice application. Each specimen was suspended in a polyethylene test tube containing 1.0 ml demineralizing solution (pH 4.3) at 37 degrees C for six hours, then transferred to a new test tube containing 1.0 ml remineralizing solution (pH 7.0) at 37 degrees C for 18 hours. Fluoride treatments were completed at the time of transfer daily for seven days. Media solutions were buffered with equal volumes of TISAB II; fluoride levels were measured using a digital ion analyzer and fluoride electrode. Fluoride release decreased significantly from Day 1 to Day 3 for all materials regardless of fluoride treatment (Repeated Measures ANOVA, Tukey HSD, p < 0.05). All specimens released significantly more fluoride in demineralizing solution than in remineralizing solution. For Days 2-7, Treatment 4 produced greater fluoride release than both the control and Treatment 2 for all three materials (p < 0.05); For each material, the fluoride release produced by Treatments 3 and 4 was statistically similar on most days throughout the study. By Day 7, Photac-Fil demonstrated both the greatest total fluoride release and the greatest rechargability, followed by Ketac-Fil and Dyract AP. Although subsequent daily fluoride release never approached that of Day 1, increasing daily fluoride exposures enhanced fluoride release for all three restorative materials.     

Fluoride release and uptake characteristics of aesthetic restorative materials

The aims of this study were firstly to investigate the fluoride-releasing characteristics of two composite resins (Tetric and Valux Plus), two polyacid-modified resin composites (Compoglass and Dyract), and conventional glass-ionomer cement (Ceramfil beta). The second aim was to assess the fluoride uptake and subsequent release from the same range of materials. Fifteen discs (6 mm diameter and 1.5 mm height) were prepared for each material. Each disc was immersed in 4 ML of deionized water within a plastic vial. The release of fluoride was measured daily at 1, 2, 3, 4, 5, 15, 30 and 60 days. After daily fluoride release was measured for 60 days, samples were refluoridated in 1000-ppm sodium fluoride (NaF) solutions (pH 6.6) for 10 min and fluoride release was measured daily for a total of 5 days. The release of fluoride from aesthetic restorative materials was measured by using specific fluoride electrode and an ionanalyser. Results were statistically analysed by two-way repeated measure ANOVA and Duncan's multiple range test. The results revealed that all fluoride-containing materials (Ceramfil beta, Compoglass, Dyract, Tetric) released fluoride initially and the release was greatest at the first day. At any time during the test period Ceramfil beta released the most and Valux Plus did not release any detectable fluoride (P < 0.01). Sample exposures to 1000 ppm NaF solution increased the 24-h fluoride release from all fluoride-containing materials. This difference lasted only 24-48 h after exposure. Ceramfil beta had a tendency to recharge not seen with the other materials (P < 0.05).     

Color Stability of Hybrid Ionomers After Accelerated Aging

Purpose The color stability and surface roughness of three commercial hybrid ionomers were determined in vitro after accelerated aging. Three shades of each hybrid ionomer prepared in light-cured and dark-cured conditions were tested. Materials and Methods Samples were aged in an artificial aging chamber by subjecting them to total ultraviolet light irradiation of 150 kJ/m² over a period of 77 hours. Color (CIE LAB system) was measured before and after aging on a reflection spectrophotometer. Surface roughness was measured with a profilometer. Results After accelerated aging, all samples became lighter. Photac-Fil Aplicap (ESPE-Premier, Norristown, PA) and Fuji II LC (GC America, Chicago, IL) also became less chromatic (less red and less yellow). Among the light-cured samples, Fuji II LC had the greatest change in color followed by Photac-Fil Aplicap and Vitremer (3M Dental Products, St Paul, MN). For the dark-cured samples, Fuji II LC had the greatest change in color followed by Vitremer and Photac-Fil Aplicap. There were no differences in delta E* between the two lightest shades, but the darker shades of each product showed the greatest changes in color. All samples became significantly rougher after aging. Conclusions Hybrid ionomers changed color significantly and perceptibly after in vitro accelerated aging. Surfaces became significantly rougher and showed evidence of cracking and degradation.     

In vitro wear evaluation of dental materials in primary teeth

PURPOSE: To evaluate the effect of dental materials on primary enamel wear. METHODS: Four composites (Filtek Z250, Heliomolar, Point 4, SureFil), two compomers (Dyract AP, F2000) and a resin-modified glass-ionomer (Vitremer) were placed into box-shaped preparations in buccal surfaces of primary molars and stored for 24 hours in water at 37 degrees C. The specimens (n = 6) were subjected to abrasive three-body wear against a primary enamel cusp. Material wear, enamel wear (adjacent to the material), and wear on enamel cusps were estimated by profilometry and video-analysis software. Results were compared with ANOVA and Tukey's tests (P < 0.05). RESULTS: Vitremer showed the highest wear (P < 0.05), followed by Dyract AP and F2000, which were not statistically different (P > 0.05). There was no significant difference between Filtek Z250 and Dyract AP (P > 0.05). Filtek Z250, Heliomolar, Point 4 and SureFil, showed the lowest wear values and there was no difference among them (P > 0.05). The highest wear values on the enamel adjacent to the material were found with Dyract AP (P < 0.05) and the lowest next to Point 4 and SureFil (P < 0.05). There was no difference in the wear of the enamel next to Vitremer, F2000, Heliomolar and Filtek Z250 (P > 0.05). Vitremer and F2000 caused the highest wear on enamel cusps (P < 0.05), and there was no statistically significant difference (P > 0.05) between them; SureFil caused the lowest wear (P < 0.05) on the opposing enamel. There was a correlation (r = 0.85) between wear of materials and wear on the enamel cusps, but not (r = 0.53) for the wear on enamel besides the restoration and wear on enamel cusps. SEM micrographs showed different surface characteristics of the materials after the wear test.     

Bond strength and interfacial micromorphology of compomers in primary and permanent teeth

Objectives. To (1) test and compare the shear bond strength of compomers (Compoglass, Dyract, Hytac) to primary and permanent dentin, (2) compare the values to those obtained with a resin-modified glass ionomer (Vitremer), and (3) evaluate the material–dentin interfacial morphology.
Sample and methods. The facial and lingual surfaces of 32 primary and 32 permanent teeth were used. The manufacturers' instructions were followed for the bonding procedures. After bonding, the teeth were thermocycled and sheared.
Results . ANOVA and Student-Newman-Keuls test revealed that the shear bond strength for Dyract was significantly higher than for the other restorative systems tested, both for primary ( P <0·001) and permanent ( P <0·01) teeth. Compoglass bond strength was significantly lower than Vitremer for the primary teeth dentin ( P <0·01). The shear bond strength for Compoglass to permanent dentin was significantly lower than for all other restorative systems ( P <0·001). There was a significantly higher shear bond strength for Compoglass ( P <0·05) and Dyract ( P <0·01) restorative systems for prim-ary compared to permanent teeth. For all products tested, all samples revealed cohesive failures. The highest frequency of cohesive failure was reported with Compoglass in both primary and permanent teeth and for Hytac and Vitremer in permanent teeth. Micromorphologically, all restorative systems revealed good adaptation to the underlying dentin; however, there was no evidence of the formation of a hybrid layer or deep resin penetration inside the dentinal tubules. There was no difference in the interfacial morphological adaptation between the primary and permanent teeth.
Conclusions . The compomers tested had shear bond strength values between those of resin-modified glass ionomers and resin composites.     

Effect of fluorosis on shear bond strength of glass ionomer-based restorative materials to dentin

STATEMENT OF PROBLEM: Several studies have investigated the adhesion of glass ionomer-based restorative materials to nonfluorotic teeth, but there appears to be no information on the bond strength of these restorative materials to dentin in fluorotic teeth. PURPOSE: This study investigated the effect of dental fluorosis on the bond strength of Ketac-fil conventional glass ionomer cement, Vitremer resin-modified glass ionomer cement, and Dyract polyacid modified resin to dentin. MATERIAL AND METHODS: Ninety posterior teeth were classified according to the severity of fluorosis, by using the Thylstrup and Fejerskov index, TFI. The teeth were divided into 3 equal groups (TFI = 0,TFI = 1-3, TFI = 4+) of 30 teeth, which were again divided into 3 equal subgroups for testing each of the3 restorative materials. Occlusal surfaces of mounted teeth were ground flat to expose dentin. Cylindrical specimens (4 mm diameter and 4 mm high) of the restorative materials were bonded to the middle of the cleaned exposed dentin surfaces, according to the manufacturers' instructions. After storing the specimens in 100% humidity at 37 degrees C for 24 hours, shear bond strengths of the restorative materials were measured with an Instron testing machine at crosshead speed of 0.5 mm/min. RESULTS: Two-way analysis of variance and Tukey-B test revealed that Dyract had significantly higher shear bond strength to dentin than Ketac-fil or Vitremer cements, regardless of severity of fluorosis (P <.05). Furthermore, there was an inverse relationship between shear bond strength and the severity of fluorosis for each of the restorative materials. Cohesive mode of failure was most prevalent in nonfluorotic teeth (TFI = 0), especially with Ketac-fil cement, whereas Dyract cement had the greatest propensity for adhesive failure. CONCLUSION: Fluorosis reduces the shear bond strength of glass ionomer-based restorative materials to dentin.     

Correlation between the amount of linear polymerization shrinkage and cuspal deflection

This study evaluated the relationship between the amount of cuspal deflection and linear polymerization shrinkage in resin composites and polyacid modified resin composites (compomers). Materials included were Dyract AP, Compoglass F, Z100, SureFil, Pyramid, Synergy Compact, Heliomolar and Heliomolar HB. To measure polymerization shrinkage, a custom-made linometer (R&B, Daejon) was used. Ten measurements were made for each group, and the amount of linear shrinkage that occurred in 60 seconds was statistically compared by one-way ANOVA analysis and Tukey's test. To measure the cuspal deflection of teeth, standardized MOD cavities were prepared in extracted maxillary premolars. After a self-etching adhesive was applied, the cavities were bulk filled with one of the filling materials. Fifteen teeth were used for each material. Cuspal deflection was measured by a custom-made cuspal-deflection measuring device. One-way ANOVA analysis and Tukey's test were used to determine differences between the materials. The correlation of polymerization shrinkage vs cuspal deflection was analyzed by regression analysis. The amount of polymerization shrinkage from least to greatest was Heliomolar, SureFil < Heliomolar HB < Z100, Synergy Compact < Dyract AP < Pyramid, Compoglass F (p < 0.05). The amount of cuspal deflection from least to greatest was Z100, Heliomolar, Heliomolar HB, Synergy Compact, SureFil, < Compoglass F < Pyramid, Dyract AP (p < 0.05). Both the amount of polymerization shrinkage and cuspal deflection were highly correlated (p < 0.001).     

Mechanical properties of compomer restorative materials.

The purpose of this study was to measure the compressive strength, flexural strength, microhardness, and surface roughness of three compomers (Compoglass, Dyract, and Hytac) and compare the values to the ones obtained for a resin-modified glass-ionomer cement (Vitremer) and a resin composite (Z100). All materials were handled according to the manufacturers' instructions. There was a significant difference (P < 0.01) among Vitremer, Hytac and Z100 composite with regard to yield strength. Vitremer values were lower than for Hytac, which were lower than for Z100. The yield strength values for Compoglass and Dyract were significantly lower than for Hytac and Z100 composite and significantly higher than for Vitremer (P < 0.01). There was no significant difference in the strain at yield among Vitremer, Hytac, and Z100, but their values were significantly higher than for Compoglass and Dyract (P < 0.01). The flexural strength data displayed a significant difference between Vitremer and Hytac (P < 0.05). Z100 was significantly stronger than the other products tested. The values of strain at break for Vitremer, Hytac, and Z100 were significantly lower than for Compoglass and Dyract (P < 0.01). The compressive strength results showed significantly higher values for Dyract, Compoglass, and Hytac than for Vitremer (P < 0.01). Z100 displayed higher values than the other products tested (P < 0.01). Hytac strength was significantly higher than for Dyract (P < 0.01). The microhardness of Compoglass and Dyract was not significantly different (P < 0.05). Hytac displayed microhardness values higher than for Vitremer, Compoglass, and Dyract (P < 0.01). However, all products tested showed values significantly lower than for Z100 (P < 0.01). The surface roughness values for Compoglass, Dyract, Hytac, and Z100 were not significantly different. Vitremer displayed a significantly higher value than Dyract, Hytac, and Z100 (P < 0.05).