Light-curing Units Research Articles

Effect of light irradiation condition on gap formation under polymeric dental restoration; OCT study

ObjectiveTo investigate the effect of two light-curing systems; quartz tungsten-halogen (QTH) and light-emitting diode (LED), and irradiation time on interfacial gap formation of dental composite resin restorations bonded with an adhesive resin using optical coherence tomography (OCT). Materials and MethodsForty cavities were prepared in extracted human molar teeth and divided into four groups (n=10) based on the type of light curing system QTH (LITEX 680A) and LED (Demi Plus) and curing duration (10 s or 40 s). A single-step self-etching dental adhesive (Tetric® N-Bond; Ivoclar Vivadent AG, Schaan, FL, Liechtenstein) was applied and polymerized with QTH for 10 s (QTH-10), or for 40 s (QTH-40). Similarly, the adhesive in LED-10 and LED-40 groups was polymerized with an LED for 10 s or 40 s, respectively. Then, all specimens were restored with Filtek™ Z350 XT flowable composite (3M ESPE AG, St. Paul, MN, USA) and immersed in ammoniacal silver-nitrate contrasting solution. Cross-sectional images were recorded at every 250μm using cross-polarization OCT system (CP-OCT; IVS-300, Santec, Komaki, Aichi, Japan). Image analysis to quantify the percentage of gap at resin-dentin interface was performed using a custom plugin for ImageJ software. ResultsData analysis using one-way ANOVA showed a significant difference in mean gap percentage between the four test groups (p<0.0001). Mean gap percentage values were 75.8%, 53.2%, 9.9% and 5.6%. The highest for LED-10 followed by LED-40 (p <0.05). QTH-40 revealed a slightly better adaptation compared with QTH-10, but the difference between them was not significant (p <0.05). ConclusionCP-OCT with a contrast agent is a useful non-invasive imaging tool for dental composite resin materials. QTH showed better results than LED under the experimental conditions. When using an LED light-curing unit, prolonged irradiation improved interfacial adaptation of dental composite bonded with a self-etching adhesive.

Effect of Curing Light and Exposure Time on the Polymerization of Bulk-Fill Resin-Based Composites in Molar Teeth.

This study examined the influence of different light-curing units (LCUs) and exposure times on the microhardness across bulk-fill resin-based composite (RBC) restorations in a molar tooth. Tip diameter, radiant power, radiant exitance, emission spectra, and light beam profile were measured on two single-emission-peak LCUs (Celalux 3 and DeepCure-S) and two multiple-peak LCUs (Bluephase 20i and Valo Grand). A mold was made using a human molar that had a 12-mm mesial-distal length, a 2.5-mm deep occlusal box, and two 4.5-mm deep proximal boxes. Two bulk-fill RBCs (Filtek Bulk Fill Posterior and Tetric EvoCeram Bulk Fill) were photoactivated for 10 seconds and for 20 seconds, with the light guide positioned at the center of the occlusal surface. Microhardness was then measured across the transverse surface of the restorations. The light that reached the bottom of the proximal boxes was examined. Data were statistically analyzed with the Student t-test, two-way analysis of variance, and the Tukey post hoc test (α=0.05). The four LCUs were different regarding all the tested characteristics. Even when using LCUs with wide tips and a homogeneous beam profile, there were significant differences in the microhardness results obtained at the central and proximal regions of the RBCs (p<0.05). LCUs with wider tips used for 20 seconds produced higher microhardness values (p<0.05). The multiple-peak LCUs produced greater hardness values in Tetric EvoCeram Bulk Fill than did the single-emission-peak LCUs (Celalux 3 and DeepCure-S). Results for the light measured at the bottom of proximal boxes showed that little light reached these regions when the light tip was positioned at the center of restorations. Curing lights with wide tips, homogeneous light beam profiles, and longer exposure times are preferred when light-curing large MOD restorations. Light curing from more than one position may be required for adequate photopolymerization.

Efek Sari Buah Lemon pada Kekasaran Permukaan Restorasi Alkasit (Penelitian)

Background. Alkasite restoration materials are introduced as dental restoration materials to improve the function, shape and aesthetics of teeth. One of the aesthetic factors that needs to be considered is the smoothness of the surface of the restoration. The smoothness of restoration surface can be affected by various factors, one of which is the degradation due to low pH. Alkasite restoration materials are mentioned to have strong polymer bonds and fillers that can release hydroxide ions which are expected to neutralize acids. Objective. To determine the effect of lemon juice on the surface roughness of alkasite restorative materials. Methods. The samples used in this study were Cention N which was light-cured with LED light-curing unit. Samples were divided into 2 groups to be immersed in lemon juice and water in separate container for 1 hour 45 minutes. Surface roughness was measured before and after immersion using surface roughness tester (Surtronic S128 S-100 Series Handheld Roughness Tester). Results. The results showed significant changes in pH of lemon juice from 2,8 to 5,7 as well as average difference of surface roughness in the Alkasite restoration samples before and after immersion (ΔRa) in lemon juice (0.22680±0.022599 µm) and water (0.04600±0.032303 µm). Conclusion. This study showed that there was an increase of lemon juice pH and Alkasite restoration surface roughness after immersion in lemon juice.

Evaluation of the influence of light-curing units on the degree of conversion in depth of a bulk-fill resin.

BackgroundIt is known that bulk-fill have been widely studied and used by dentists in the clinic. However, the use of light-curing units that do not have the ability to adequately light-cure these materials at the appropriate depth can affect their clinical performance. The aim of this study was evaluating the influence of 5 different light curing units (LCUs) on the degree of conversion (DC) of a bulk-fill resin at depths of 0 to 4 mm and determined the effect of using 20s exposure and 40s. Material and MethodsCylinders of composite were made in a stainless steel matrix (n=10). The specimens were exposed from the top surface using 5 LCUs: Valo® Cordless (VA); Radii Plus (RA); Emitter.D (EM), Biolux Plus (BI), Woodpecker® (WO). The emission wavelength and the power density was determined. After the photoactivation, the Raman vibrational modes were calculated taking as reference the peaks at 1,601 (aromatic bonds C=C) and 1,640 cm-1 (aliphatic bonds C=C). ResultsThe largest difference in DC in 20s, comparing the values obtained in the first and last layer is for BI, with a variation from 61.24% to 53.86%. Comparing the LCUs, the last layer in 40s DC values are 57.40% (BI), 58.21% (WO), 58.97% (VA), 60.90% (RA) and 62.42% (EM). The higher the dose (J/cm²) and the close the λmax is to the maximum CQ absorption length (λmax ~ 470 nm) the better the DC value. ConclusionsThere was a significant difference in the DC values between the LCUs with increasing depth of the bulk-fill increments. Results indicate significant differences in DC among the different LCUs as well as enhanced DC when using 40s exposure compared to 20s. It is suggested that for DC improvement using lower power photoactivator increase the exposure time the exposure time should be 20s to 40s. Key words:Polymerization, Composite Resins, Raman spectroscopy.

Influence of Light-Curing Intensity on Color Stability and Microhardness of Composite Resins.

The purpose of this study was to evaluate the intensity of light-curing units and its relationship with the color stability and microhardness of composite resins with different shades subjected to a thermocycling procedure. Eighty blocks (5.0 × 2.0 mm) of TPH Spectrum composite resin (Dentsply Sirona) were produced and distributed into four groups according to the light-curing units (EC 450, ECEL; Valo, Ultradent) and color of the resin material (A3; C3) (n = 20). Within each group, color stability was measured on half the sample (n = 10) using a UV-2450 visible UV spectrophotometer (Shimadzu), and Knoop hardness was measured on the other half (n = 10) using an HMV 2000 microhardness tester (Shimadzu) before and after thermocycling (12,000 cycles, 5°C and 55°C). Mann-Whitney test was performed on the color stability data; the microhardness data were analyzed using a three-way analysis of variance (ANOVA) and Tukey test (α = .05). The ANOVA results showed that thermocycling, distinct light intensity, and different colors of resin materials influenced the microhardness of the composite resins, which was evidenced by the A3 composite resin light-cured with a Valo polywave showing higher hardness values. There was no statistical difference in the color stability of the A3 composite resin; however, the C3 composite resin light-cured with an EC 450 singlewave light-curing unit showed higher color alteration values. In general, the Valo polywave light-curing unit imparted better mechanical property and color stability to both shades of the composite resins. The different shades of resin material influenced the hardness of the composite resins. Therefore, the light intensity of the light-curing units should be evaluated and monitored, as the amount of light intensity will interfere in the quality and longevity of resin restorations.

Light-Curing Units, Photoinitiators System, and Monomers on Physico-Mechanical Properties of Experimental Composite Resins

This study evaluated the physico-mechanical properties of experimental composite resins made with different resin matrix and light-curing units. Experimental composite groups were divided according to monomers (BisGMA + TEGDMA-BT and BisGMA + BisEMA + UDMA + TEGDMA-BBUT) and photoinitiator system (camphorquinone-CQ and 1-phenyl-1,2-propanedione-PPD). A quartz tungsten halogen (QTH) or light-emitting diode (LED) were used to light cure all materials. Knoop microhardness (n = 10) was determined using Knoop microhardness test. Compressive strength, diametral tensile strength, and Young modulus (n = 7) were obtained using a universal testing machine at crosshead speed of 1.0 mm/min. The data were submitted to a three-way ANOVA and the Tukey post-hoc test (α = 0.05). QTH presented the highest total irradiance values and similar total radiant exposure to LED. For the compressive strength test, BT-PPD light-cured with LED group showed the lowest mean value. BT-CQ light-cured with LED group exhibited the lowest diametral tensile strength results. The BBUT-composite resins presented lowest Young modulus values, with no statistical difference between light-curing units (QTH and LED) and photoinitiators system (CQ and PPD). Application of QTH or LED in BT-based composite resins with PPD photoinitiator generated suitable results regarding the physico-mechanical properties. Keywords: Biomaterials; blends; dental composites; polymerization; shrinkage

Surface Hardness of Nanohybrid and Microhybrid Resin Composites Cured by Light Emitting Diode and Quartz Tungsten Halogen Light Curing Systems: An Invitro Study

Introduction: New generation composite resin materials have revolutionized the art of aesthetic dentistry. The clinical success is dependent on effective polymerisation and surface hardness which in turn are dependent on the performance of Light Curing Units (LCU). This study utilises surface hardness as a measure of degree of polymerisation of composite resins achieved by LCUs. Aim: To evaluate the difference in surface hardness of nanohybrid and microhybrid resin composites cured by light curing systems, Light Emitting Diode (LED) and Quartz Tungsten Halogen (QTH). Materials and Methods: In this invitro experimental study, two types of hybrid composites (Nanohybrid and Microhybrid) were tested for surface hardness by using two different light curing systems (LED and QTH). All the Nanohybrid and Microhybrid specimens were cured using LED and QTH LCUs, thus giving four combinations. A total of 60 specimens (6 mm diameter and 2 mm depth) were prepared using Teflon mould with 15 samples for each combination. Surface hardness was measured on upper and lower surface after 24 hours and hardness ratio was calculated. Data was analysed using independent t-test for intergroup comparison. Level of significance was kept at 5%. Results: Surface hardness of resin composites cured by LED LCU was greater than those cured by QTH LCU. Additionally, the hardness value was greater for the upper surface. Nanohybrids showed better surface hardness than Microhybrids for both the LCUs. Conclusion: Nanohybrid composite resins and LED system were found to be more effective in terms of surface hardness as compared to their counterparts.

Assessing dental light-curing units’ output using radiometers: A narrative review

Introduction:This review aimed to describe dental radiometers and discuss their effectiveness compared to other light-testing devices.Materials and Methods:The search for light-curing units (LCUs), radiometers, and other light-measuring tools available on the market was accomplished on data found on PubMed, Wikipedia, and Google.Results:LCUs are prone to deterioration due to several reasons such as the light’s limited life span, the worsening of the LCU’s filters, light guide, and light tip end; consequently, decreased photopolymerization and insufficient resin conversion may occur. A regular light output assessment is highly recommended in dental daily practice as well as before any new LCU purchase to make sure the light features meet the factory specifications delivered by the manufacturer and they remained stable through time.Discussion:Irradiance values reported by radiometers do not match accurately with those delivered by laboratory power meters. Therefore, dental practitioners as well as dental students are advised to control regularly every LCU by using the same handheld radiometer.

Effects of curing modes on depth of cure and microtensile bond strength of bulk fill composites to dentin.

Objectives To compare the microtensile bond strength (µTBS) and depth of cure (DOC) of bulk-fill composites cured by monowave (MW) and polywave (PW) LED units using different curing times.Methodology Three composites were tested: Tetric EvoCeram Bulk Fill (TBF), Filtek Bulk Fill (FBF), and Tetric EvoCeram (T; control). Flat dentin surfaces treated with adhesive (AdheSE Universal®, Ivoclar Vivadent) were bonded with 4 mm cylindrical samples of each bulk-fill composite material (n=6) and cured with monowave (Satelec) or polywave (Bluephase Style) curing units for 10 or 20 seconds. After 24 hours, teeth were sectioned into individual 0.9 mm2 beams and tested for µTBS. Failure modes were analysed. Moreover, the DOC scrape test (IOS 4090) was completed (n=5) following the same curing protocols. Two-way ANOVA (a=0.05) was performed, isolating light-curing units.Results For samples cured with the MW light-curing unit, no significant effects were observed in the µTBS results between any of the resin composite brands and the curing times. Conversely, when resins were cured with a PW light unit, a significant effect was observed for TBF resin. In general, bulk-fill composites presented greater DOC and longer curing time resulted in higher DOC for all composites.Conclusion The µTBS of the composites to dentin was not affected by the curing mode of the resins, except for TBF cured with PW light unit. Bulk-fill composites exhibit greater DOC than conventional resin-based composites.

Effect of light intensity, light-curing unit exposure time, and porcelain thickness of ips e.max press and vintage LD press on the hardness of resin cement

Background: Porcelain veneer restoration is the primary choice for indirect restoration, especially for anterior teeth, given its high esthetic properties and lower failure rate than resin composites. Glass-based ceramics such as IPS e.max Press and Vintage LD Press are a choice for veneer due to its superior physical properties. Resin cement is used to attach the veneer restoration to the teeth. The polymerization of resin cement used in veneer restoration affects the stability, mechanical properties, and resistance of the restoration. The composition and thickness of the porcelain material affect the light-curing unit to cured resin cement. Objectives: The aim of this study was to evaluate the influence of porcelain thickness, light intensity, and exposure time in the hardness of resin cement. Methods: Porcelain samples measuring 5 mm in diameter with three types of thicknesses of IPS e.max Press and Vintage LD Press were used in the study. Resin cement in a metal mold was placed under a porcelain sample before curing with a light-emitting diode (LED) intensity of 1300 or 1700 mW/cm2. The hardness test was then carried out on the bottom of the resin cement. Result: The highest hardness value was obtained from a Vintage LD Press with a thickness of 0.7 mm (cured at 1300 mW/cm2 for 20 s). A four-way ANOVA test showed significant differences for brands, thicknesses, and times of exposure (P

Effect of modulated photoactivation of bulkfill composite on microleakage in fluorosed and nonfluorosed teeth: A confocal laser scanning microscopy study.

Aim:The aim of this study is to compare the microleakage of bulkfill composite activated by modulated photoactivation between fluorosed and nonfluorosed teeth using the confocal laser scanning microscope.Methodology:One hundred and twenty intact human premolar teeth with Thylstrup and Fejerskov index fluorosis index 0–4 were stored in 0.5% thymol at the room temperature until further use. Standardized Class V preparations of 2 mm depth, 3 mm width, and 2 mm height were prepared on the buccal surface. The cavities were etched with 37% phosphoric acid, rinsed and primed with Tetric N bond, cured for 20 s with Quartz Tungsten Halogen (QTH) variable intensity light-curing unit spectrum-800 operating at 450 mW/cm2. Later, bulk fill composite was placed in the cavity and cured. Depending on the curing mode used, all the fluorosed and nonfluorosed teeth were divided into three subgroups each (n = 20) – Conventional light curing, stepped curing, and pulse delayed curing. All samples were stored in distilled water at the room temperature for 24 h and subjected to 500 thermocycles. The prepared teeth were placed in 0.6% rhodamine solution for 48 h; sectioned longitudinally using a hard-tissue microtome and scanned under a confocal laser scanning electron microscope. Data were analyzed using the one-way ANNOVA, Wilcoxson signed-rank test, and Kruskal–Wallis test.Results:Significant differences were observed between fluorosed and nonfluorosed groups. Intragroup comparisons showed significant differences between fluorosed step and conventional subgroups.Conclusion:Fluorosed teeth had higher microleakage values than nonfluorosed teeth. Pulse-delayed subgroup had the least microleakage to that of conventional and stepped curing subgroups, in both fluorosed and nonfluorosed groups.

Effect of Different LED Light-curing Units on Degree of Conversion and Microhardness of Bulk-fill Composite Resin

The aim of this study is to compare the effect of the use of second-generation and third-generation LED light-curing units (LCUs) on the degree of conversion (DC) and microhardness (VHN) of bulk-fill resin composites. Thirty cylindrical specimens (each n = 5) of Tetric N-Ceram Bulk-Fill, Filtek™ Bulk-Fill Posterior Restorative, and SDR flow were prepared in metal molds (5 mm in diameter and 4 mm in thickness) and cured with second-generation LED (SmartLite® Focus®, Dentsply Sirona) and third-generation LED (Bluephase® style, Ivoclar Vivadent) resulting in six groups. Degree of conversion was determined using Fourier transform infrared spectroscopy (FTIR), and microhardness with Vickers microhardness tester. Data were statistically analyzed using one-way ANOVA and least significance difference (LSD) test, and DC and microhardness were correlated using Pearson's correlation (α = 0.05). There was a significant difference between DC and VHN between all groups of bulk-fill which were cured by second-generation LED curing light and third-generation LED curing light. Then there is no significant difference between DC of the three composite bulk-fill resins by (second-generation LED vs third-generation LED curing light). The second-generation LED curing light can still be used to cure bulk-fill resin composites by increasing the duration of irradiation. In the microhardness test, there was a significant difference in the Filtek™ Bulk-Fill Posterior Restorative resin composites.

The effect of repeated preheating on diametral tensile strength of composite resin with different fillers

Background: The development of adhesive systems has made the removal of carious lesion a minimally invasive procedure. Composite resin is the material of choice today, but the filler composition of the resin varies. Packable composite resin has good mechanical properties, but its high viscosity makes it hard to manipulate. Several methods, such as preheating, are used to decrease this viscosity. A syringe of composite resin might be preheated several times, but the effect of repeated preheating is unknown. Objectives: The purpose of this research was to analyze the effect of repeated preheating on the mechanical properties of a composite resin with different fillers. Method: Microhybrid, nanohybrid, and nanofill composite resins were preheated (ten times, twenty times, and control), molded into cylinder molds 6 mm in diameter and 3 mm in height, flattened with a celluloid strip, and polymerized with an light-emitting diode light-curing unit for 40 s. A total of 180 specimens were tested. The specimens were divided into two groups: Group 1 was immediately tested using a universal testing machine. Group 2 was soaked in 37°C artificial saliva for 24 h before testing. Each specimen was tested using the universal testing machine with the pressure side with a 1 mm/s crosshead speed. Result: Nanohybrid composite resin had the most stable diametral tensile strength after repeated preheating, whereas nanofill composite had the weakest strength. The increase and decrease in the diametral tensile strength in each group were not statistically significant. Conclusion: Repeated preheating does not significantly affect the diametral tensile strength of composite resin.

Color stability of a bulk-fill composite resin light-cured at different distances.

The aim of this in vitro study was to evaluate the color stability of a bulk-fill (Filtek One Bulk Fill, 3M ESPE) and a conventional (Filtek Z350 XT, 3M ESPE) composite resin light-cured at different distances, before and after being submitted to staining with a coffee solution. Sixty specimens of each composite resin were prepared and light-cured at distances of 0, 2 and 4 mm, using a LED light-curing unit (Valo, Ultradent). The specimens were separated (n = 10) for immersion in either distilled water or coffee solution (10 minutes a day for 8 days) to stimulate staining. Color evaluations were performed before and after immersion in the solutions, according to CIELab (△Eab), CIEDE2000 (△E00) and the Whiteness Index for Dentistry (△WID). Kruskal Wallis and Dunn tests, Mann-Whitney tests and Wilcoxon test were applied (α = 5 %). The a* value for conventional composite resin showed a significant increase after immersion in coffee and distilled water (p < 0.05). Both composite resins showed greater b* values when immersed in coffee than in distilled water, with no significant difference among the light-activation distances (p > 0.05). There was no significant difference for L* among the light-activation distances; both resins showed significant decrease in L* after immersion in coffee (p < 0.05). Color change (△Eab, △E00) and difference in whiteness (△WID) were higher for conventional resin when immersed in the coffee solution at all the light-activation distances. Conventional composite resin presented a higher staining value than bulk-fill composite resin, regardless of the light-activation distance.

Quantification of porosity in composite resins delivered by injectable syringes using X-ray microtomography

Objective To assess whether composite polymer resin delivered in compules include pores and the possible effect on the amount of porosity in dental restorations. Method and materials Original compules containing unpolymerised composite polymer resin (CPR) were scanned in a micro-CT. Four products were examined, which comprised universal composites (Herculite XRV Ultra, Ceram.X Universal, Tetric Evo Ceram) and a flowable bulk-fill composite (SDR) (n = 10 per group). The pore size distribution and amount of porosity (vol.%) were estimated for the unpolymerized and polymerized material used to restore a standardised cavity in a typodont tooth. Manufacturers’ instructions were followed regarding material handling, and polymerisation by use of a calibrated light-curing unit. The pore characteristics and their size distribution, and the amount of porosity in the dental restoration were contrasted with the values measured in the compule. Non-parametric tests were used to analyse differences between the four products. Results All the composite polymer resin compules contained unpolymerised material that included pores. The universal composite compules included pores predominantly in the sub-100 µm sizes. In contrast, the flowable bulk-fill compules included a few pores with a diameter >100 µm, which were assumed to be air-bubbles. The unpolymerised material within the compule included consistently more pores compared to the extruded portion from the compule tip, and in the final restoration (p < .001). The amount of porosity in the restorations differed amongst the tested materials, with the flowable bulk-fill composite showing the lowest amount of porosity (p < .01).

Comparative Evaluation of the Surface Hardness of Different Esthetic Restorative Materials: An In Vitro Study.

ABSTRACTAim:The aim of this study was to evaluate the surface hardness of a newly developed fiber-reinforced composite and bulkfill composites.Materials and Methods:Fiber-reinforced composite and other commercially available bulkfill composites were used. Fifteen cylindrical specimens (5 mm × 5 mm) were made from each material in metal template. Molds were filled in one increment for both bulkfill composites and fiber-reinforced composite and cured using Ivoclar blue phase light-curing unit at a wavelength of 850 mW/cm2. A dark container was used to store specimens to keep dry at room temperature for 24 h before testing. Vickers hardness number (VHN) on the top and bottom surfaces of each specimen was measured by a microhardness tester. Data for VHN were analyzed by using analysis of variance (ANOVA) and pair-wise Newman–Keuls test.Results:No significant difference was observed in Vickers hardness test. The mean value of VHN on the top and bottom surfaces showed significant difference from each other. Fiber-reinforced composite showed the highest VHN as compared with other materials.Conclusion:Fiber-reinforced composite has the highest Vickers hardness ratio indicating highest degree of conversion and better clinical performance.

Assessment of the radiant emittance of damaged/contaminated dental light-curing tips by spectrophotometric methods.

ObjectivesThis study investigated the effects of physically damaged and resin-contaminated tips on radiant emittance, comparing them with new undamaged, non-contaminated tips using 3 pieces of spectrophotometric laboratory equipment.Materials and MethodsNine tips with damage and/or resin contaminants from actual clinical situations were compared with a new tip without damage or contamination (control group). The radiant emittance was recorded using 3 spectrophotometric methods: a laboratory-grade thermopile, a laboratory-grade integrating sphere, and a portable light collector (checkMARC).ResultsA significant difference between the laboratory-grade thermopile and the laboratory-grade integrating sphere was found when the radiant emittance values of the control or damaged/contaminated tips were investigated (p < 0.05), but both methods were comparable to checkMARC (p > 0.05). Regardless of the method used to quantify the light output, the mean radiant emittance values of the damaged/contaminated tips were significantly lower than those of the control (p < 0.05). The beam profile of the damaged/contaminated tips was less homogeneous than that of the control.ConclusionsDamaged/contaminated tips can reduce the radiant emittance output and the homogeneity of the beam, which may affect the energy delivered to composite restorations. The checkMARC spectrophotometer device can be used in dental offices, as it provided values close to those produced by a laboratory-grade integrated sphere spectrophotometer. Dentists should assess the radiant emittance of their light-curing units to ensure optimal curing in photoactivated, resin-based materials.

The effect of in-office bleaching applications on the color and translucency of composite resins

Aim: The study aimed to evaluate the relationship between the caries frequency, which was determined using different caries indexes Objective: The aim of this study was to investigate the effect of in-office bleaching agents on the color and translucency of different resin composites. Materials and Methods: Twenty-four disk-shaped specimens with 1 mm thickness and 8 mm diameter were fabricated from five different resin composites. The specimens were then divided into three subgroups, two office bleaching groups (40% Opalescence Boost, 38% Whitesmile Power Whitening) and one control group (n=8). All specimens were polymerized for 40 s with a LED light-curing unit. Color measurement was performed using a spectrophotometer. Bleaching agents were applied to the experimental groups in accordance with the manufacturer's instructions for 14 days, while the specimens in the control group were kept in distilled water only. Translucency parameters of the specimens before and after bleaching and the color changes after bleaching were calculated using CIE L*a*b* color coordinates. Data were analyzed using the paired sample t-test and ANOVA (α=0.05).Results: Statistically significant differences were found between the control group and the bleached groups according to color change values (p0.05). The highest mean color change value was observed in the Ceram-X / Opalescence Boost group. The Ceram-X / Opalescence Boost, Majesty Esthetic / Opalescence Boost, and Ceram-X / Whitesmile Power specimens showed clinically non-acceptable color changes. Translucency parameter values in each group between baseline and the end of the 14th day revealed no statistically significant difference (p>0.05).Conclusions: The office bleaching agents may affect the color and translucency parameters of composite resins depending on the structural properties.

Labor and birth outcomes in term low-risk adolescent pregnancies

Aim: The study aimed to evaluate the relationship between the caries frequency, which was determined using different caries indexes Objective: The aim of this study was to investigate the effect of in-office bleaching agents on the color and translucency of different resin composites. Materials and Methods: Twenty-four disk-shaped specimens with 1 mm thickness and 8 mm diameter were fabricated from five different resin composites. The specimens were then divided into three subgroups, two office bleaching groups (40% Opalescence Boost, 38% Whitesmile Power Whitening) and one control group (n=8). All specimens were polymerized for 40 s with a LED light-curing unit. Color measurement was performed using a spectrophotometer. Bleaching agents were applied to the experimental groups in accordance with the manufacturer's instructions for 14 days, while the specimens in the control group were kept in distilled water only. Translucency parameters of the specimens before and after bleaching and the color changes after bleaching were calculated using CIE L*a*b* color coordinates. Data were analyzed using the paired sample t-test and ANOVA (α=0.05).Results: Statistically significant differences were found between the control group and the bleached groups according to color change values (p0.05). The highest mean color change value was observed in the Ceram-X / Opalescence Boost group. The Ceram-X / Opalescence Boost, Majesty Esthetic / Opalescence Boost, and Ceram-X / Whitesmile Power specimens showed clinically non-acceptable color changes. Translucency parameter values in each group between baseline and the end of the 14th day revealed no statistically significant difference (p>0.05).Conclusions: The office bleaching agents may affect the color and translucency parameters of composite resins depending on the structural properties.

Factors associated with light curing units: a questionnaire survey

Introduction: The introduction of light-cured resin-based materials is a revolutionary step in restorative dentistry. Despite their wide distribution and daily use, the interaction between visible curing light and composite resins is not understood well enough by most dentists. Aim: The aim of this study is to check dentists’ level of knowledge about different factors affecting the polymerization process of resin-based composites and the use of light curing units (LCUs). Materials and Methods: The task was performed by an anonymous questionnaire survey, consisting of 15 questions, which was filled out by 112 dentists from the whole country. Results and Discussion: The analysis of the results shows that most of the dentists are poorly acquainted with the factors affecting the polymerization of resin-based composites. Dentists often make mistakes when placing their adhesive restorations, which leads to the incomplete polymerization of the material and all the consequences from that – risk of fractures, lower wear resistance, elution of unreacted monomers, higher microleakage, and lower adhesive bonding strength. Light intensity is one of the main factors that determine the necessary curing time. However, more than the half of the participants in the survey (52%) do not know their LCU’s output and 21% do not use any protection, which leads to a serious risk of eye damage. Conclusion: It is necessary for dentists to improve their knowledge about LCUs and the polymerization process of resin-based composites, which will significantly increase the longevity of their composite fillings.