Properties of four composite veneering materials polymerized with different laboratory photo-curing units

Fracture Resistance of Ceramic Crowns Supported with Indirect Chair-side Composite Cores

Aims and Objectives

To evaluate the influence of indirect chair-side polymerization of resin composite cores on the fracture resistance of overlaying IPS e.max Press crowns.

Materials and Methods

Root canals of 60 extracted premolars were prepared to receive #2 fiber posts after the crowns were sectioned 2 mm above the cervical line. In Groups 1-3 (n = 10 each), posts were luted to the prepared dowel spaces using self-adhesive resin cement. Resin composite cores were then bonded and incrementally built-up using Filtek Z250 XT, Filtek P60, and Filtek P90 resin composites. In Groups 4-6 (n = 10 each), the fabricated post-core systems were subjected to post-curing heat and pressure treatment before cementation to their respective teeth using self-adhesive resin cement. Another 10 sound premolars served as control. All teeth in the test and control groups were then subjected to standardized preparation to receive IPS e.max Press crowns before testing their fracture resistance and the mode of restorations' failure. The collected results were statistically analyzed using ANOVA, Kruskal-Wallis, and Tukey's tests on the past software used at α = 0.05 to stand on the significance of the detected differences.

Results

Significant differences were detected between the fracture resistance of teeth in different groups (ANOVA, P = 2.857E-35). Crowns in Groups 4-6 provided higher fracture resistance than those in Groups 1-3 (Tukey's test, P < 0.05). Crowns in Groups 4 and 6 provided higher fracture resistance than the control, while those in Groups 2 and 3 provided lower fracture resistance than the control (Tukey's test, P < 0.05).

Conclusion

Indirect composite cores improved the fracture resistance of IPS e.max Press crowns when compared to directly fabricated post and cores. The directly and indirectly polymerized nanohybrid, methacrylate-based composite (Filtek Z250 XT) cores yielded the highest fracture resistance for the utilized all-ceramic crowns.

Changes in chroma of two indirect composite materials polymerized with different polymerization systems

This study evaluated chroma change in two composite materials (Sinfony and Pearleste) polymerized with two different systems. Disk specimens were prepared using a metal halide unit (Hyper LII) and an exposure time of 60 to 180 s. The proprietary polymerization systems (Visio and Pearlcure systems) were used as the reference polymerization modes. After storage at 37°C for 24 h, CIE 1976 L*a*b* values were measured by using a dental chroma meter (ShadeEye NCC) with a gray background. The specimens were then immersed in water or tea. Color change from baseline to 4 weeks was evaluated by measuring ΔL*, Δa*, and Δb*, after which ΔE*(ab) values were calculated. The brightness of Sinfony specimens was reduced by tea immersion. The color of both materials shifted to yellow after tea immersion, although color change in Sinfony specimens was greater than that in Pearleste specimens. For both materials, color change was less after polymerization with the metal halide unit. In conclusion, Sinfony polymerized with the Hyper LII unit, and Pearleste polymerized with either system, were stable against discoloration due to tea immersion.

Depth of cure and hardness of indirect composite materials polymerized with two metal halide laboratory curing units

The purpose of this study was to evaluate the depth of cure and Knoop hardness of indirect composite materials polymerized with different laboratory curing units. Five composite materials designed for fixed restoration veneer (Artglass, Ceramage, Epricord, Prossimo, and Solidex) were filled into a cylindrical mold and then light-exposed by using the respective proprietary laboratory curing unit or two metal halide curing units (Hyper LII and Twinkle X). Depth of cure was determined by a scraping technique, as described in ISO 4049. Composites also underwent Knoop hardness testing after immersion in water. The results (n = 5) were analyzed with the Kruskal-Wallis test and Dunn's multiple comparison test. For three materials (Prossimo, Artglass, and Epricord), depth of cure after polymerization with the Twinkle X unit was greater than that after polymerization with the respective proprietary units. For the Ceramage and Artglass materials, the Twinkle X unit resulted in the highest Knoop hardness number (KHN), whereas, for the Prossimo material, the Hyper LII unit resulted in the highest KHN. The metal halide units were effective in enhancing the post-polymerization properties of specific composite materials while reducing exposure time.

Color stability of indirect composite materials polymerized with different polymerization systems

The purpose of the current study was to evaluate the color stability of two indirect composite materials (Sinfony and Pearleste) polymerized with different laboratory polymerization systems. Disk specimens were prepared with their proprietary polymerization systems (Visio and Pearlcure systems) or with a metal halide light polymerization unit (Hyper LII) for 60, 120, and 180 s. After storage at 37 degrees C for 24 h, the specimens were immersed in either purified water or tea. Color change between baseline evaluation and after 4 weeks was determined with a dental chroma meter (ShadeEye NCC) using black and white backgrounds. CIE 1976 L(*)a(*)b(*) values were determined, and they were converted into DeltaE(*)(ab) values. The DeltaE(*)(ab) value of the Sinfony material immersed in tea was the highest when the material was polymerized with the proprietary Visio system. The Pearleste material immersed in purified water and tea was not affected substantially by the polymerization systems. Among the 12 groups polymerized with the Hyper LII units, DeltaE(*)(ab) values of 11 groups were significantly lower for the Pearleste material than for the Sinfony material. It can be concluded that the Pearleste material was stable against color change when the material was polymerized with either the Pearlcure system or with the Hyper LII unit.

Depth of cure and hardness of an indirect composite polymerized with three laboratory curing units

This study determined the hardness and curing depth of a light-activated indirect composite polymerized with three laboratory light-polymerizing units for the purpose of comparing the curing performance of the three units. A light-activated composite material for indirect application (Vita Zeta) was polymerized with three light-polymerizing units equipped with the following light sources: 1) one halogen lamp and two fluorescent lamps (alpha-Light II); 2) three halogen lamps (Twinkle HLG); and 3) one metal halide lamp (Twinkle LI). Knoop hardness and curing depth were determined for groups of five specimens using standardized testing methods. The results were compared using analysis of variance (ANOVA) and Scheffé's S intervals (alpha = 0.05). The Knoop hardness number (KHN) generated with the halogen-fluorescent unit (12.5 KHN) was significantly (P < 0.05) lower than those produced by the halogen unit (13.9 KHN) and the metal halide unit (14.2 KHN). Of the three units, the halogen-fluorescent unit exhibited the lowest depth of cure. Both the hardness and curing depth of the composite were influenced by the laboratory polymerizing units employed.

Conventional and High Intensity Halogen Light Effects on Water Sorption and Microhardness of Orthodontic Adhesives

Objective: To test the null hypothesis that when the equivalent total light energy is irradiated to three orthodontic adhesive resins, there is no difference between the microhardness and water sorption values regardless of the curing light sources.

Materials and Methods: Samples were divided into six groups according to the combination of three orthodontic adhesives (Kurasper F, Light-Bond, Transbond XT) and two light intensities (quartz tungsten halogen [QTH] and high intensity quartz tungsten halogen [HQTH]). One half of each of the 40 samples of three adhesive pastes was polymerized for 20 seconds by a QTH light source, and the other half was polymerized for 10 seconds by a HQTH light source. Water sorption was determined and Vickers hardness was established with three measurements per sample at the top, center, and bottom. Statistical analysis was performed using two-way analysis of variance (ANOVA) with multiple comparisons (Tukey-HSD).

Results: Statistically significant differences were found among all adhesives for water sorption and hardness values cured with QTH and HQTH. The HQTH curing unit resulted in higher values than did the QTH. The highest water sorption values were observed for Kurasper F cured with HQTH and the lowest value was observed for Transbond XT cured with QTH. For microhardness Light-Bond cured with HQTH produced the highest values, and Transbond XT cured with QTH produced the lowest.

Conclusions: When the equivalent total light energy is irradiated to three orthodontic adhesive resins, there are significant differences between the microhardness and water sorption values cured with the QTH and HQTH light source. The null hypothesis is rejected.

Mechanical Properties of Light-curing Composites Polymerized with Different Laboratory Photo-curing Units

This study aimed to analyze the microhardness (KHN) and diametral tensile strength (DTS) of two hybrid resin composites (TPH Spectrum and Filtek Z250). To this end, the composites were polymerized with six laboratory photo-curing units (LPUs) and the results compared with an alternative polymerization method using conventional halogen light source in conjunction with additional polymerization in an autoclave (15 minutes/100 degrees C). LPUs were used following the manufacturers' instructions. Diametral tensile strength and Knoop hardness tests were conducted for all groups (n=5). Data were statistically compared using ANOVA and Tukey's test (alpha = 0.05). Among the LPUs, the one that provided light curing in conjunction with heat and nitrogen pressure resulted in a significant increase in KHN and DTS of resin composites. Between the resin composites, Filtek Z250 showed higher hardness values than TPH Spectrum. It was concluded that the use of alternative polymerization with conventional light polymerization and autoclave was feasible with a wide implication for the general public in terms of reduced dental treatment cost.

Use of a light-polymerized composite removable partial denture base for a patient hypersensitive to poly(methyl methacrylate), polysulfone, and polycarbonate: a clinical report

This article describes a light-polymerized composite denture base used for a patient with hypersensitivity to poly(methyl methacrylate) (PMMA), polysulfone (PSF), and polycarbonate (PC). A urethane-dimethacrylate (UDMA) composite was used as an alternative to fabricate both the denture base and the custom artificial teeth. Immediately after placing the new prosthesis, allergic symptoms disappeared from the patient's mucous membrane. The denture has functioned satisfactorily for more than 2.5 years without recurrence of the hypersensitivity.

Effect of metal halide light source on hardness, water sorption and solubility of indirect composite material

This study evaluates the effects of a metal halide light source on the post-polymerization properties of the Sinfony indirect composite material. Two polymerization systems were employed: the Hyper LII system, comprising a metal halide polymerization unit, and the Visio system, comprising two proprietary units designed for polymerizing the Sinfony composite. The composite material was polymerized for 60, 120 or 180 s with the LII system. As a control, the composite was polymerized for 15 min with the Visio system. Knoop hardness, water sorption and solubility were determined. The results were analyzed by Dunnett's T3 multiple comparison test (P<0.05). Knoop hardness was greater for polymerization with the LII unit than for that with the Visio system. Water sorption was greater for polymerization with the Visio system than that with the LII unit. For polymerization with the LII unit for 180 s, solubility was significantly reduced as compared with the Visio system. Within the limitations of the current experiment, it can be concluded that the metal halide unit exhibited better polymerizing performance for the composite material than the proprietary units.

Properties of dual-curable luting composites polymerized with single and dual curing modes

The purpose of this study was to evaluate the influence of visible-light exposure on water absorption, solubility and colour stability of dual-curable luting composites. Using eight dual-curable luting composites (2bond2, Bistite II, G-CERA Cosmotech II, Imperva Dual, Linkmax, Lute-It, Panavia Fluoro Cement and Variolink II), disk specimens were prepared by the following two methods: (i) dual-cured specimens; exposed with visible-light from a light-curing unit, and (ii) chemical-cured specimens; chemically polymerized without exposure. Five specimens were produced for each material and curing mode. Water absorption and solubility were determined according to standardized testing methods, and the data were compared using analysis of variance (ANOVA) and contrasts. With regard to colour stability, the colour difference (DeltaE*) values between 24 h and the other immersion periods (1, 2, 3, 4, 8, 12, 16, 20 and 24 weeks) were calculated and then analysed by repeated measure ANOVA. The dual-cured specimens exhibited significantly lower solubility values than the chemical-cured specimens except for the Lute-It material. The dual-cured Linkmax material exhibited the lowest solubility (0.51 +/- 0.01 microg mm(-3)) and the lowest DeltaE* value after 24 weeks (2.64 +/- 0.39). The dual-curable luting composites should be light-exposed after seating of restorations in order to reduce water absorption and solubility, and to improve colour stability.

Properties of a new photo-activated composite polymerized with three different laboratory photo-curing units

This study determined the hardness, solubility and curing depth of a new photo-activated composite polymerized with three different laboratory photo-curing units for the purpose of evaluating the post-curing properties of the material. A new photo-activated composite material for both direct and indirect applications (DiamondCrown) was polymerized with three photo-curing units equipped with the following light sources: (i) two halogen lamps (DiamondLite-VL. Halogen Light Curing Booth); (ii) two metal halide lamps (Hyper LII) and (iii) two xenon stroboscopic tubes (UniXS II). Knoop hardness, water solubility and curing depth were determined for groups of five specimens according to standardized testing methods. All data were compared using analysis of variance (anova) and Scheffe's S intervals (P < 0.05). The Knoop hardness number (KHN) generated with the metal halide unit (63.3 +/- 2.4 KHN) was statistically (P < 0.05) greater than those produced by the other two curing units. Water solubility values for both the halogen unit (2.5 +/- 0.5 microg mm(-3)) and the metal halide unit (2.5 +/- 0.5 microg mm(-3)) were significantly (P < 0.05) lower than for the xenon unit (3.8 +/- 0.5 microg mm(-3)). Of the three photo-curing units, the metal halide curing-unit consistently exhibited the greatest depth of cure. The composite material appears to be reliable, although its post-curing properties were found to be influenced by the type of curing unit.

Knoop hardness depth profiles and compressive strength of selected dental composites polymerized with halogen and LED light curing technologies

After the first light-emitting diode (LED) light curing units (LCUs) became available commercially, a comparison of mechanical properties between materials polymerized with conventional halogen lamps and this new technology was required. This study, therefore, investigated the curing performance of two conventional commercial halogen LCUs (Translux CL, Spectrum800), a custom-made LED LCU prototype, and one of the first commercially available LED LCUs (LUXoMAX). The Spectrum800 was adjusted to a similar irradiance to the custom-made LED LCU prototype. Both technologies were compared by measuring compressive strength and Knoop hardness depth profiles for selected dental composites polymerized for 20 or 40 s. Four dental composites (Z100, Spectrum TPH, Solitaire2, and Definite) were used. Two of these composites (Solitaire2 and Definite) contain co-initiators in addition to the standard photoinitiator camphorquinone. In general, the material hardness obtained with the LUXoMAX was statistically significantly (p < 0.05) lower at the depths of 0.1, 1.0, 1.9, and 3.1 mm, for all composites and curing times, than for the other three LCUs. The LED LCU prototype achieved, with one exception, up to a depth of 1.9 mm a material hardness for the composites Z100, Spectrum TPH and Solitaire2 that was not statistically significant different (p < 0.05) from the hardness obtained with the halogen LCUs. At a greater depth (3.1 mm), however, the LED LCU prototype showed statistically significantly lower hardness values than the halogen units. The compressive strength test showed at a 95% confidence level that similar compressive strengths were achieved with the LCUs LUXoMAX and Spectrum800, and the Translux and LED LCU prototype.

[Correlation between degree of conversion, microhardness and inorganic content in composites]

The purpose of this study was to evaluate the correlation between degree of conversion and microhardness in dental composites, as well as the effect of the inorganic content and type of photo-curing unit on these parameters. Three indirect composites (Artglass, Solidex and Zeta LC) were polymerized by means of three different laboratorial units (UniXS, Solidilite and an experimental device). For each material, fifteen samples were prepared using a metal matrix. The degree of conversion was analyzed by means of infrared spectroscopy, and microhardness was also assessed. The inorganic content was measured by means of thermogravimetric analysis (TGA). The Pearson s test was carried out in order to determine correlations. The degree of conversion of Artglass ranged from 37.5% to 79.2%, and its microhardness, from 32.4 to 50.3 (r = 0.904). The degree of conversion of Solidex ranged from 41.2% to 60.4%, and its microhardness, from 33.3 to 44.1 (r = 0.707). The degree of conversion and the microhardness of Zeta LC ranged from 62.0% to 78.0% and from 22.6 to 33.6, respectively (r = 0.710). It was concluded that the utilization of different photo-curing units caused variations on the degree of conversion, as a result of specific characteristics of each unit. For each material, there was strong correlation between the degree of conversion and microhardness. In addition, when different materials were compared, microhardness was more affected by filler content than by the degree of conversion.

Analysis of composite type and different sources of polymerization light on in vitro toothbrush/dentifrice abrasion resistance

OBJECTIVES

This study examined toothbrush/dentifrice abrasion of a photo-activated prosthetic composite (dentin and enamel variations) for the purpose of evaluating the influence of polymerization sources on abrasive wear.

METHODS

A photo-activated prosthetic composite material (Artglass) was assessed. Dentin and enamel variations were polymerized using a proprietary photo-curing unit with two xenon stroboscopic lamps (UniXS), and other enamel specimens were polymerized either with a laboratory photo-curing unit with three fluorescent tubes or with a high intensity unit with two metal halide lamps. All specimens were stored in water for 14days and subjected to toothbrush/dentifrice abrasion (350g vertical load) using an abrasive slurry (Colgate Fluoriguard) and a toothbrush (Oral-B 40). The amount of vertical loss and the surface roughness of the specimens after 20,000 strokes were determined by profilometer. Average values of groups of five specimens were compared using analysis of variance (ANOVA) and Sheffe's S intervals (p<0.05).

RESULTS

When polymerizing with the proprietary unit, the abrasion and surface roughness of the enamel material required respective means of 34.08microm (+/-3.66) and 1.00microm (+/-0.08), and the those of the dentin material required means of 42.02microm (+/-5.62) and 1.23microm (+/-0.20). Both abrasion and surface roughness after toothbrushing of the enamel material were significantly smaller than were those of the dentin material. The abrasion of specimens polymerized with the metal halide unit required a mean of 23.89microm (+/-6.17) and demonstrated minimal wear.

CONCLUSIONS

The use of a high intensity metal halide photo-curing unit effectively enhanced the abrasion resistance of the composite. Surfaces of restorations should be covered with the enamel material in order to achieve smoothness and wear resistance.

Wear and surface roughness of current prosthetic composites after toothbrush/dentifrice abrasion

STATEMENT OF PROBLEM

Surface changes of prosthetic composites caused by toothbrushing are known, although composite materials have been improved and are now widely used for various kinds of prosthetic restorations.

PURPOSE

This study evaluated the influence of toothbrushing on abrasive wear and surface roughness of current prosthetic composites.

MATERIAL AND METHODS

Seven composite materials (Artglass, Axis, Cesead II, Conquest Sculpture, Estenia, Infis, and Targis) were assessed, and a machinable ceramic material (Cerec 2 Vitablocs) was used as a reference. Composite specimens polymerized with their proprietary curing units and sectioned ceramic specimens were stored in water for 14 days, and subsequently subjected to toothbrush-dentifrice abrasion. The amount of vertical loss and the surface roughness of each specimen after 20,000 strokes were determined with a profilometer. Average values of groups of 5 specimens were compared with ANOVA and Duncan new multiple range test.

RESULT

Significantly (P < .05) less wear was observed with respect to the Targis (10.01 microm; SD = 0.53 microm) and Estenia (13.04 microm; 1.95 microm) materials than for the other composites assessed, whereas Artglass (34.08 microm; 3.66 microm) and Conquest Sculpture (31.78 microm; 4.67 microm) materials demonstrated the most wear. The least surface roughness was exhibited by Conquest Sculpture (Ra, 0.54 microm; 0.07 microm) material, and the greatest by Cesead II (1.10 microm; 0.13 microm). Ceramic material showed a more wear-resistant (4.54 microm; 0.79 microm) and smoother (0.26 microm; 0.02 microm) surface than any of the composite materials.

CONCLUSION

Abrasion and surface roughness of the prosthetic composites caused by toothbrushing varied in accordance with the material. Type of prosthetic composite significantly influenced the surface condition after toothbrushing.

Depth of cure and compressive strength of dental composites cured with blue light emitting diodes (LEDs)

OBJECTIVE

The primary objective of this pilot study was to test the hypotheses that (i) depth of cure and (ii) compressive strength of dental composites cured with either a light emitting diode (LED) based light curing unit (LCU) or a conventional halogen LCU do not differ significantly. The second objective of this study was to characterise irradiance and the emitted light spectra for both LCUs to allow comparisons between the units.

METHODS

Dental composite (Spectrum TPH, shades A2 and A4) was cured for 40 s with either a commercial halogen LCU or a LED LCU, respectively. The LED LCU uses 27 blue LEDs as the light source. The composites' depth of cure was measured for 10 samples of 4 mm diameter and 8 mm depth for each shade with a penetrometer. The results were compared using a Student's t-test. Compressive strengths were determined after 6 and 72 h, for six samples of 4 mm diameter and 6 mm depth for each shade after being polymerised for 40 s from each end of the mould. Groups were compared using a three way ANOVA.

RESULTS

The conventional halogen LCU cured composites significantly (p < 0.05) deeper (6.40 mm A2, 5.19 mm A4) than did the LED LCU (5.33 mm A2, 4.27 mm A4). Both units cured the composite deeper than required by both ISO 4049 and the manufacturer. A three way ANOVA showed that there were no significant differences in the compressive strengths of samples produced with either the LED LCU or the halogen LCU (p = 0.460). Significant differences in compressive strength of samples stored for 6 and 72 h (p = 0.0006) and of samples of different shades (p = 0.035) were found as confirmed by the three way ANOVA. The light spectra of both units differed strongly. While the halogen LCU showed a broad distribution of wavelengths with a power peak at 497 nm, the LED LCU emitted most of the generated light at 465 nm. The LED LCU produced a total irradiance of 350 mW cm-2 whereas the halogen LCU produced a total irradiance of 755 mW cm-2.

SIGNIFICANCE

The results showed that both units provided sufficient output to exceed minimum requirements in terms of composites' depth of cure according to ISO 4049 and the depth of cure and the composites' compressive strength stated by the manufacturer. Compressive strengths of dental composites cured under laboratory conditions with a LED LCU were statistically equivalent to those cured with a conventional halogen LCU. With its inherent advantages, such as a constant power output over the lifetime of the diodes, LED LCUs have great potential to achieve a clinically consistent quality of composite cure.

Effectiveness of polymerization of a prosthetic composite using three polymerization systems

STATEMENT OF PROBLEM

Although properties of laboratory-polymerized composite materials are influenced by the type of polymerizing unit, little information is available regarding the comparison between use of a high-intensity light source and application of secondary heat treatment.

PURPOSE

This study examined properties of a prosthetic veneering composite polymerized with 3 polymerizing systems to evaluate the effects of varying polymerization modes on hardness, solubility, and depth of cure.

MATERIAL AND METHODS

A composite material designed for a prosthetic veneer (Conquest Crown and Bridge) was polymerized using 3 methods: (1) exposure in the proprietary photopolymerizing unit with 2 halogen lamps (Cure-Lite Plus), followed by heating in an oven (Conquest Automatic Curing Unit); (2) exposure in a photopolymerizing unit with a xenon stroboscopic light source (Dentacolor XS); and (3) exposure in a photopolymerizing unit with 2 metal halide lamps (Hyper LII). Knoop hardness, water solubility, and depth of cure were determined for groups of 5 specimens, according to standardized testing methods. Data were compared using analysis of variance and the Duncan new multiple range test (P <.05).

RESULT

The hardness number generated with the metal halide unit was statistically greater than those produced by the other 2 methods, and material component released into water was minimal when the material was exposed with the metal halide unit (P <.05). Among the 3 photopolymerizing units, the metal halide unit consistently exhibited the greatest depth of cure.

CONCLUSION

Certain properties generated with the use of the high-intensity polymerizing unit exceeded those obtained from a proprietary system that requires a postheat treatment.

Curing depth of prosthetic composite materials polymerized with their proprietary photo-curing units

This study examined curing depth of eight prosthetic composite materials polymerized by means of six photo-curing units for the purpose of evaluating the curing performance of material-curing unit combinations. Each composite material was exposed with a photo-curing unit recommended by the manufacturer. The light sources of the units were halogen/fluorescent, xenon, metal halide, fluorescent, and halogen lamps, and exposure periods were 20, 30, 60, and 90 s. Curing depth of the materials was determined according to the method described by the International Organization for Standardization (ISO 4049). The results were analysed by factorial analysis of variance (ANOVA) and multiple comparison intervals. Two-factor ANOVA revealed that the depth of cure was influenced both by the material-unit combination and by the exposure period (P = 0.0001). Among the eight combinations, a hybrid composite material (Prywood color) polymerized with a metal halide curing unit (Hyper LII) exhibited the greatest depth of cure after 90-s exposure. For all combinations, longer exposure increased the depth of cure.