Effectiveness of polymerization of a prosthetic composite using three polymerization systems

Structural and mechanical analysis of three orthodontic adhesive composites cured with different light units

OBJECTIVE

To evaluate the effects of three different curing units on the physical and mechanical features of three different orthodontic adhesive resin materials.

MATERIAL AND METHODS

45 specimens (5 mm in diameter, and 2 mm in thickness) of each of the three different adhesive composite resin materials (Transbond XT, Grēngloo™ Adhesive and Light Bond Paste) were cured with three different light units (a polywave third generation (Valo), a monowave (DemiUltra), and a second-generation LED (Optima 10)). To quantify degree of conversion (DC), the Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy was used in transmission mode (ALPHA FT-IR Spectrometer, Bruker Optics, Germany). Vickers hardness value was recorded under constant load 100 g for 10 s with a microhardness tester (HMV M-1, Shimadzu Corp., Kyoto, Japan). The data were statistically analyzed using Kruskal-Wallis and chi-square tests. The level of significance was considered p < 0.05.

RESULTS

The highest DC values were obtained as a result of curing with Optima 10. This rate was followed by Demi Ultra and Valo, respectively. Transbond XT samples showed a lower level of conversion than the samples of Light Bond Paste and Grēngloo™ Adhesive. The top surfaces of each material showed higher hardness values than the bottom surfaces (p < 0.05). The Light Bond Paste showed the highest hardness values both on the top and bottom surfaces among the three materials, followed by Grēngloo™ Adhesive. While the hardness values of the top surfaces of the samples cured with Demi Ultra and Valo light units were similar, higher hardness values are recorded with Valo on the bottom surfaces (Valo; 85.200/75.200 (top/bottom) versus Demi Ultra; 86.100/66.000 (top/bottom)).

CONCLUSIONS

The different DC and the surface hardness properties were recorded for the resin as orthodontic adhesives depending on different light units. Shorter radiation time caused lower DC and surface hardness values.

An In vitro Evaluation of Flexural Bond Strength of Indirect Composites Fused to Metal

With the advent of newer indirect composite resin materials for crown and bridge prosthesis, it has become imperative to evaluate their strength to serve as long term replacements as a substitute to metal ceramic restorations. This study aimed to evaluate and compare the flexural bond strength of three composite resin veneering material to metal, cured by different methods. Specimen were fabricated with pattern resin by duplicating it with machined metal die and divided into three groups. Three composite resin materials were used in this study. Group (A) received Adoro, Group (B) received Targis and Group (C) received Tescera. The bond strength of all specimens was tested with Lloyd's universal testing machine under three point loading. The highest values for fracture resistance were displayed by light, heat and pressure cured composites followed by composites cured using a temperature of 104 °C and composites with curing temperature of 95 °C. The results indicate that there is a significant difference between the three groups, with the Tescera group specimens exhibiting the highest flexural bond strength. Of the other two groups, Adoro group exhibited higher flexural bond strength than Targis group. The results of this study suggest that Tescera group with curing temperature of 130 °C and pressure of 80 Psi, cured with metal halide unit exhibited the highest flexural bond strength when compared to Adoro and Targis groups.

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.

Flexural strengths of fiber-reinforced composites polymerized with conventional light-curing and additional postcuring

INTRODUCTION

The purpose of this study was to evaluate the effect of hand light-curing (Optilux 501; SDS Kerr, Danbury, Conn) and secondary oven polymerization (Liculite; Dentsply, Dreieich, Germany) on the mechanical properties of 2 sizes (diameters, 0.6 and 1.2 mm) of fiber-reinforced composites (FRCs) (Ever Stick; Stick Tech, Turku, Finland).

METHODS

The FRC samples were divided into 8 groups. Each group consisted of 10 specimens. Each FRC sample was evaluated with a 3-point bending test with a universal testing machine. Groups 1, 3, 5, and 7 were hand light-cured with a halogen curing unit for 40 seconds. Groups 2, 4, 6, and 8 were light-cured with the same curing unit for 40 seconds, followed by polymerization for 15 minutes in a light-curing oven. Groups 1 through 4 were tested at 1-mm deflection, and groups 5 through 8 at 2-mm deflection.

RESULTS

The results of ANOVA indicated significant differences among the various groups (P = .000). The post-hoc test showed that the 2-mm deflection groups had significantly higher flexural strengths than the 1-mm deflection groups (P = .000). Moreover, the 1.2-mm FRCs showed significantly higher flexural strength than the 0.6-mm FRCs (P = .000). No significant differences (P >.05) were found between the hand light-cured and the oven-polymerized groups.

CONCLUSIONS

This investigation demonstrated that oven postcuring does not increase the flexural strength values of 0.6- and 1.2-mm FRCs compared with conventional hand light-curing. Thus, hand light-curing of FRCs is recommended directly in the mouth for orthodontic purposes.

Hardness measured with traditional Vickers and Martens hardness methods

OBJECTIVE

To determine the differences, if any, between hardness measured with traditional Vickers and Martens hardness test methods on denture teeth under 2, 10 and 50 N loads.

METHOD

Hardness of acrylic resin (VIV), composite resin (ORT) and porcelain (POR) denture tooth materials was measured using a traditional Vickers hardness (HV) method and Martens hardness (HM) method at 2, 10 and 50N test loads. Vickers hardness was also calculated from the force-indentation depth curves (HVfid) that were recorded during Martens hardness. Indentation creep of the three test materials was also determined during Martens hardness testing.

RESULTS

HM values were the same irrespective of the test force used. However, HV values were different for the three test forces. ANOVA using Tukey's test of the HM data showed that the hardness of POR was significantly higher than VIV or ORT (P<0.001). Moreover, ORT had a significantly higher hardness than VIV (P<0.001). The statistical analysis of HVfid data showed similar results. ANOVA of the HV data showed the hardness of VIV to be significantly higher than ORT (P<0.001) under 2, 10 and 50 N test load. The HV values for POR under 2 and 10 N test load could not be calculated because of inability to measure the indentation diagonals. Under the 50 N load, the hardness of POR was significantly higher than VIV and ORT. POR had a significantly lower creep value than any other material tested while VIV showed a statistically significantly higher creep than ORT.

SIGNIFICANCE

This study confirms that the visco-elastic recovery of the materials has a very significant effect on the outcome of the hardness tests of denture teeth and the Martens hardness test method has obvious advantages when testing dental materials.

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.

Effects of various light curing methods on the leachability of uncured substances and hardness of a composite resin

The purpose of this study was to evaluate the effect of the various light curing units (plasma arc, halogen and light-emitting diodes) and irradiation methods (one-step, two-step and pulse) using different light energy densities on the leachability of unreacted monomers (Bis-GMA and UDMA) and the surface hardness of a composite resin (Z250, 3M). Leachability of the specimens immersed for 7 days in ethanol was analysed by HPLC. Vicker's hardness number (VHN) was measured immediately after curing (IC) and after immersion in ethanol for 7 days. Various irradiation methods with three curing units resulted in differences in the amount of leached monomers and VHN of IC when light energy density was lower than 17.0 J cm(-2) (P = 0.05). However, regardless of curing units and irradiation methods, these results were not different when the time or light energy density increased. When similar light energy density was irradiated (15.6-17.7 J cm(-2)), the efficiency of irradiation methods was different by the following order: one-step > or = two-step > pulse. These results suggest that the amount of leached monomers and VHN were influenced by forming polymer structure in activation and initiation stages of polymerization process with different light source energies and curing times.

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.

Depth of cure and microleakage with high-intensity and ramped resin-based composite curing lights

BACKGROUND

The authors conducted a study to determine whether high-intensity curing lights in high and ramped intensity modes affect microleakage of resin-based composite restorations and whether different types of resin-based composites meet American National Standards Institute/American Dental Association Specification no. 27 (1993): 7.7 for depth of cure when polymerized using these lights.

METHODS

The authors compared five high-intensity lights, three plasma arc lights and two quartz-tungsten-halogen lights in their regular and ramped intensity modes with a quartz-tungsten-halogen 40-second light. The parameters tested were microleakage one month after bonding and curing depth for different resin-based composite types. The authors measured curing depth using a scratch test.

RESULTS

Light curing with Optilux 501 (Kerr/Demetron, Orange, Calif.) for 10 seconds and ADT Power PAC (American Dental Technologies, Corpus Christi, Texas) for 10 seconds resulted in higher microleakage values than light curing with other lights (P < .05). The microhybrid resin-based composite was the only material that met the specification when light cured with all of the lights tested. The flowable resin-based composite did not meet the specification when light cured with all lights tested. Microhybrid resin-based composite had the greatest depth of cure, and flowable resin-based composite had the least depth of cure.

CONCLUSIONS

Microhybrid resin-based composite microleakage is affected by some light-curing modes. Different categories of resin-based composites are cured to different depths using high-intensity lights.

CLINICAL IMPLICATIONS

Light curing with some high-intensity lights compared with halogen lights may result in higher microleakage values. Use caution when light curing flowable resin-based composite with the high-intensity lights. Place increments less than 2 millimeters in depth when using this material.

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.

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.