A metal halide light source for laboratory curing of prosthetic composite materials

Depth of cure, water absorption, and solubility of indirect composites polymerized by light-emitting diode laboratory units

This study investigated the usefulness of a dental laboratory polymerization unit with light-emitting diode (LED) as a light source. The depth of cure (n=15), water absorption and solubility (n=9) of two indirect composite materials (Cesead N and Solidex Hardura) were evaluated by five dental laboratory polymerization units (LED Cure Master, Twinkle LED, α-Light V, α-Light II, and Hyper LII). Statistical analysis was performed by one-way ANOVA and Tukey test or non-parametric tests. Comparison of light sources for curing depth showed that metal halide had the highest value, followed by the LED group with similar values, and halogen lamps with the lowest value. The water absorption and solubility of the composite specimens polymerized with the three LED laboratory polymerization units were within the ISO recommended limit.

Properties of indirect composites polymerized with laboratory light-emitting diode units

This study evaluated the light intensity of light-emitting diode (LED) units and the effects of five laboratory polymerization units on hardness and flexural strength. Two indirect composite materials (Cesead N and Solidex Hardura) were polymerized with five units (α-Light II, Hyper LII, LED Cure Master, Twinkle LED, and α-Light V). The light intensity of the devices was measured with a spectroradiometer. After light exposure, Knoop hardness number, flexural strength, and elastic modulus were determined. Evaluation of light intensity, using a wavelength range of 400 to 500 nm, revealed that the α-Light V and Hyper LII units had the highest light intensity. For the top surface of the two composites, the Knoop hardness number was significantly higher for the α-Light V and Hyper LII. For the two composite materials, flexural strength did not differ among the five polymerizing units. The present results indicate that the Cesead N and Solidex Hardura composites can be adequately polymerized with laboratory LED units.

The influence of polymerization conditions on color stability of three indirect composite materials

The aim of the present study was to evaluate color change and color stability against aqueous media of three indirect composite materials (Epricord, Estenia, and Twiny) that were polymerized with different systems. Disk-shaped specimens were prepared with their proprietary polymerization systems or with a metal halide light polymerization unit (Twinkle X). The specimens were then immersed in water or tea. Change in color from baseline (24 h) to 4 weeks was determined with a chromameter (ShadeEye NCC) using a white background. The L*, a*, and b* values for both states were determined, and ΔE*(ab) values were calculated. The Estenia specimens immersed in tea had significantly lower ΔL* (-7.0 to -5.6) and significantly higher ΔE*(ab) values (6.5 to 8.6) than did the Epricord and Twiny specimens, under all polymerization conditions. The results indicate that after tea immersion the Estenia material was less stable against color change than were the other two materials. The Twinkle X metal halide unit was suitable for polymerization of the three composite materials, using an exposure period of 60 s or longer.

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.

Influence of laboratory light sources on the wear characteristics of indirect composites

The purpose of the current study was to evaluate the influence of light sources on the mechanical properties and wear characteristics of indirect composite materials. The two composite materials used were Estenia C&B and Epricord. The three laboratory polymerization units used, of which the wavelength range was 400-500 nm, were Hyper LII (two metal halide lamps of 4.82 mW/cm(2)), α-Light II (one halogen lamp and two fluorescent tubes of 3.60 mW/cm(2)), and Labolight LV-II (three fluorescent tubes of 0.63 mW/cm(2)). Three-body wear test was performed using indirect composite plate specimens, a gold alloy antagonist, and a polymer slurry. Wear depths of Estenia C&B polymerized with Hyper LII, α-Light II, and Labolight LV-II were 5.7, 18.5, and 64.2 µm respectively, whereas those of Epricord were 12.9, 18.7, and 48.5 µm respectively. Results showed that, after 100,000 cycles of localized loading, high-intensity light sources were effective in enhancing the wear resistance of both composite materials.

Indirect resin composites

Aesthetic dentistry continues to evolve through innovations in bonding agents, restorative materials, and conservative preparation techniques. The use of direct composite restoration in posterior teeth is limited to relatively small cavities due to polymerization stresses. Indirect composites offer an esthetic alternative to ceramics for posterior teeth. This review article focuses on the material aspect of the newer generation of composites. This review was based on a PubMed database search which we limited to peer-reviewed articles in English that were published between 1990 and 2010 in dental journals. The key words used were 'indirect resin composites,' composite inlays,' and 'fiber-reinforced composites.'

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.

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 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.

Veneering technique for a Ti-6Al-7Nb framework used in a resin-bonded fixed partial denture with a highly filled indirect composite

This article presents a veneering technique for fixed partial denture frameworks made from a Ti-6Al-7Nb alloy. The fixed partial denture framework was prepared with a magnesia-based mold material and a centrifugal casting machine. An esthetic veneer was fabricated with a highly filled dual-polymerized composite material and a metal-conditioning agent. This technique can be applied as a standardized veneering procedure for the titanium alloy, for which porcelain fusing is currently difficult.

[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.

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.

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

Post-curing properties of composite materials are influenced by the type of base monomer, activation system, filler content, and also by the type of light source employed. This study examined curing depth of four composite veneering materials polymerized by means of two different high-intensity photo-curing units for the purpose of evaluating the curing performance of the combinations of composite material and photo-curing unit. Two microfilled and two hybrid composite materials designed for prosthetic veneer were assessed. The composite materials were cured using two photo-curing units, one with a xenon light source and one with two metal halide light sources, and exposure periods varied from 20 to 90 s. Curing depth of the materials was determined with a scraping technique described by the International Organization for Standardization (ISO 4049). Three-factor analysis of variance revealed that the depth of cure was influenced by the type of composite material as well as by the photo-curing unit, and also by the exposure period (P = 0.0001). A microfilled composite material (Dentacolor) demonstrated the greatest depth of cure (4.69 mm) after 90 s irradiation with a metal halide unit (Hyper LII). Of the two photo-curing units, the metal halide curing unit consistently exhibited greater depth of cure than the xenon curing unit (Dentacolor XS). Longer exposure increased the depth of cure for all combinations.

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

This study examined properties of four composite veneering materials polymerized with two different photo-curing units for the purpose of evaluating curing performance of the combination of composite material and curing unit. Two microfilled (Dentacolor and Thermoresin LC II) and two hybrid (Cesead II and Solidex) composite materials designed for prosthetic veneer were selected. The respective light sources of the units were a xenon (Dentacolor XS) and a metal halide (Hyper L II) lamp. The composite materials were exposed with the photo-curing unit for 60 s on each side (i.e. from top and bottom). Knoop hardness, compressive strength, flexural strength, flexural modulus, water absorption and water solubility were determined according to standardized testing methods. The specimens exposed with the metal halide unit generally exhibited greater Knoop hardness number, and compressive strength and lower solubility than those exposed with the xenon unit. A microfilled material (Thermoresin LC II) cured with the metal halide unit exhibited significantly improved results for all tests as compared with the same material cured with the xenon unit.

Curing depth of a composite veneering material polymerized with seven different laboratory photo-curing units

Properties of laboratory-cured composite materials are affected by the type of activation system as well as by the photo-curing unit light source. This study examined curing depth of a composite veneering material polymerized by means of various photo-curing units with the aim of evaluating the curing performance of the light sources. A microfilled composite material designed for prosthetic veneer was cured with seven photo-curing units. The light sources of the units were halogen/fluorescent, xenon, metal halide, fluorescent, halogen, halogen and mercury lamps. Exposure periods were 20, 30, 60 and 90 s. The curing depth of the material was determined using the method described by the International Organization for Standardization (ISO 4049). Two-factor analysis of variance revealed that the depth of cure was influenced both by the type of curing unit and by the exposure period (P = 0.0001). Among the seven photo-curing units, a metal halide curing unit consistently exhibited the greatest depth of cure. For all units, longer exposure increased the depth of cure.

Dental materials citations: Part A, January to June 1997

OBJECTIVE

A search was conducted in biomedical journals published from January 1997 to June 1997 to identify all dental materials publications and sort them into major categories.

METHODS

Tables of contents for 79 journals for the period of January to June, 1997 were inspected and divided into 17 categories. Citations were analyzed by both frequency in journals and in categories, as well as compared to frequencies for previous years.

RESULTS

A total of 445 citations were detected in 79 journals for the period January 1997 to June 1997. Certain journals (n = 19) demonstrated a higher citation frequency (> or = 10 citations for 6 months) and represented 77.8% of all citations. The greatest number of citations continued to involve bonding (n = 97), resin-based restorative materials (composites; glass ionomers) (n = 95), prosthodontic materials (n = 51), and pulp protection/luting materials (n = 48). Frequencies by category were very similar to those for the last four years.

SIGNIFICANCE

The compiled literature citations provide a supplement for researchers and academicians seeking information in existing electronic databases.