Temperature Changes in Primary and Permanent Teeth Dentine of Varying Thicknesses Following Irradiation by Two Light Curing Units.

AIM: This study was performed to determine the temperature rise under human dentin discs of different thicknesses from primary and permanent teeth during the photo-curing process using quartz tungsten halogen (QTH) or light-emitting diode (LED). MATERIALS AND METHODS: The current experimental study sample consisted of 160 dentin discs of different thicknesses (0.5, 1, 1.5, and 2 mm), of which 80 dentin discs were prepared from sound lower second primary molars, and the remaining 80 dentin discs were prepared from sound lower third permanent molars extracted surgically for various reasons. A "K" type of thermal tentacle was placed in the center of an acrylic resin base, followed by the placement of a dentin disc. Then, the thermal changes were measured during the photo-curing of the composite using a second LED or QTH light curing unit for 20 s. Statistical evaluation was performed using the IBM SPSS Statistics® Version 20.0 software system (SPSS Inc., Chicago, IL, USA). RESULTS: The current study found that the temperature rise in primary teeth (1.17-2.96°C) is significantly lower compared to the rise in permanent teeth (1.55-3.33°C), regardless of the dentin disc thickness or light curing unit used. The temperature rise decreases significantly when the thickness of dentin discs increases, regardless of the type of teeth or light curing unit used (P<0.05). Furthermore, QTH causes less temperature rise (1.17-2.65°C) compared to LED (1.61-3.33°C). CONCLUSIONS: The temperature rise during polymerization of the resin composite with the second-generation LED appeared to be below 5.5°C. Hence, it appears to be safe for use during the restoration of primary teeth. Primary teeth dentin might be more effective than permanent teeth dentin in protecting the dental pulp.

Comparison of the effects of operating microscopes with light emitting diode and halogen light source on the eye: a rabbit study.

PURPOSE: To evaluate the potential toxicity of operation microscopes with halogen and light emitting diode (LED) light source on the rabbit eyes. MATERIALS AND METHODS: Thirty-two eyes of 16 male New Zealand pigmented rabbits were involved in the study. The rabbits were divided into two groups according to the type of light source applied. Only one eye of each rabbit was exposed to illumination light, unexposed fellow eyes served as the control group. Experimental groups included group 1 exposed to halogen light for 2 h and evaluated 1 day and 1 week after the illumination, group 2 exposed to LED light for two hours and evaluated 1 day and 1 week after the illumination. On the first and seventh days after exposing the light, we evaluated the rabbit corneas using in vivo confocal microscopy (IVCM). At the end of the seventh day, the Hematoxylin-eosin staining and TUNEL staining were performed to investigate the presence of apoptosis in the retina and retina pigment epithelium. RESULTS: Early IVCM findings revealed corneal epithelial cell ovalization and indistinct intercellular borders in the halogen light group. We also observed more increase in the keratocyte density index (23.7% vs 14.1%, p = 0.001, respectively) and the Bowman reflectivity index (12.4% vs 4.1%, p = 0.001, respectively) at first day of the light exposure in halogen light group compared to LED light group. However, late IVCM indicated that these findings disappeared one week later. No apoptosis was observed in the corneal and retinal layers in early and late examination groups. CONCLUSION: The present experimental study demonstrated that both halogen and LED lights, which were commonly used for microscopic eye surgery, had no sustained adverse effect on the cornea and retina of the rabbits; however, halogen light had a temporary adverse effect on corneal epithelium and stroma, which resolved within 1 week.

The effect of halogen light stimulation on duration of ultrasound parameters of biophysical profile: a randomized clinical trial.

INTRODUCTION: The objective is to assess if fetal halogen light stimulation can reduce the time needed to obtain a normal biophysical profile (BPP). METHODS: Patients scheduled for a BPP and who satisfied the inclusion criteria were prospectively randomized to halogen light stimulation and no stimulation groups. The study group was exposed to handheld halogen light for 10 s whenever fetal breathing, movement, or tone was absent through the first 5 min of BPP. The time required to achieve complete BPP score was recorded. In patients with complete BPP score who had delivery within 1 week after the test, perinatal morbidity was examined. RESULTS: A total of 598 patients were randomized (light = 302, no light = 296). There was no difference between the two groups in terms of gestational age, maternal age, body mass index, and indication for BPP except for preterm labor (light: 9%, no light: 4%, p = 0.03). Among the patients who had a normal BPP score (n = 507), the mean (light: 7.1 ± 6 min, no light: 12.3 ± 8 min, p < 0.0001) and median (light: 4.3, no light: 8, p = 0.004) time needed to complete the BPP score was significantly less in the light stimulation group than the no stimulation group. Perinatal outcomes were not different between groups who had delivery during the first week after BPP. CONCLUSION: Fetal halogen light stimulation can be utilized to reduce the time needed to complete a BPP. However, further studies should be conducted in order to determine the effect of this method on decreasing non-reassuring test results. CLINICAL TRIAL REGISTRATION: The study was submitted to the Registry of Clinical Trials on 04/20/2017 (IRCT2017041633470N1). After IRCT registration on 06/07/2017, we recruited patients from 06/08/2017 till 10/15/2017.

A Comparative Evaluation of the Influence of Command Set Methods on Microleakage of Glass Ionomer Cement: An In Vitro Study.

INTRODUCTION: A major challenge when using glass ionomer cement in clinical situation particularly in paediatric dentistry is to overcome the problem of microleakage. Fast or command setting of Type IX glass ionomer cement using external energy source enhances the setting reaction and results in improved initial physical and mechanical properties. AIM: To compare and evaluate the influence of ultrasonic activation, halogen light irradiation and combined effect of both on microleakage of enamel adjacent to Type IX glass ionomer restorations. MATERIALS AND METHODS: For forty premolar teeth, standard Class V cavities prepared were restored with GC Gold Label Type IX glass ionomer cement in vitro. The specimens were randomly divided into four groups: 1) Control group; 2) halogen group; 3) ultrasonic group; 4) ultrasonic with halogen group. The teeth were kept in distilled water for 24 hours. Teeth were exposed to 1500 thermocycles at temperature of 12°C ±2 and 60°C ±2 with alternate immersion in hot and cold water for one minute. First teeth were immersed in dye solution for four hours and then in developing solution for four hours. The samples were sectioned buccolingually through centre of the restorations and degree of dye penetration was assessed under stereomicroscope and scored. One-Way ANOVA model was constructed followed by post-hoc Tukey's test for multiple pair wise comparison of mean values. RESULTS: Statistically significant differences were found in microleakage among the four groups (p<0.001) with respect to dye penetration. Halogen group showed least microleakage followed by control but differences between them were statistically not significant (p>0.05). Similarly the differences between Ultrasonic plus halogen group and ultrasonic group were not significant (p>0.05). The differences between ultrasonic and halogen group were statistically significant (p<0.05). CONCLUSION: Halogen light decreases the microleakage of enamel adjacent to GC Type IX glass ionomer restorations, when used to accelerate the setting reaction of glass ionomers and can be used as command set method in paediatric dentistry.

Full in-vitro analyses of new-generation bulk fill dental composites cured by halogen light.

The objective of this study was to investigate the full in-vitro analyses of new-generation bulk-fill dental composites cured by halogen light (HLG). Two types' four composites were studied: Surefill SDR (SDR) and Xtra Base (XB) as bulk-fill flowable materials; QuixFill (QF) and XtraFill (XF) as packable bulk-fill materials. Samples were prepared for each analysis and test by applying the same procedure, but with different diameters and thicknesses appropriate to the analysis and test requirements. Thermal properties were determined by thermogravimetric analysis (TG/DTG) and differential scanning calorimetry (DSC) analysis; the Vickers microhardness (VHN) was measured after 1, 7, 15 and 30days of storage in water. The degree of conversion values for the materials (DC, %) were immediately measured using near-infrared spectroscopy (FT-IR). The surface morphology of the composites was investigated by scanning electron microscopes (SEM) and atomic-force microscopy (AFM) analyses. The sorption and solubility measurements were also performed after 1, 7, 15 and 30days of storage in water. In addition to his, the data were statistically analyzed using one-way analysis of variance, and both the Newman Keuls and Tukey multiple comparison tests. The statistical significance level was established at p<0.05. According to the ISO 4049 standards, all the tested materials showed acceptable water sorption and solubility, and a halogen light source was an option to polymerize bulk-fill, resin-based dental composites.

Evaluation of bleaching efficacy of 37.5% hydrogen peroxide on human teeth using different modes of activations: An in vitro study.

INTRODUCTION: The aim of this in vitro study is to evaluate the role of light and laser sources in the bleaching ability of 37.5% H2 O2 on extracted human teeth. MATERIALS AND METHODS: About 30 caries-free single-rooted maxillary central incisors were used for the study. Specimens were prepared by sectioning the crown portion of teeth mesiodistally, and labial surface was used for the study. Specimens were then immersed in coffee solution for staining. Color of each tooth was analyzed using Shadestar, a digital shademeter. Specimens were then divided into three groups of 10 each and were subjected to bleaching with 37.5% H2 O2, 37.5% H2 O2 + light activation, and 37.5% H2 O2 + laser activation, respectively. Postbleaching, the color was analyzed for all the specimens immediately and then after 1, 2, and 3 weeks intervals, respectively. RESULTS: All the statistical analyses were done using SPSS version 17. Intra- and inter-group comparisons were done with Friedman test and Kruskal-Wallis ANOVA, respectively. Statistical analysis concluded with a significant improvement in their shade values from baseline in all the three groups. Halogen light activation and laser-activated groups showed comparatively enhanced bleaching results over no-activation group, though the difference was not statistically significant. CONCLUSION: The results of the present study show that bleaching assisted with halogen light and laser showed increased lightness than nonlight activated group. Durability of bleaching results obtained postbleaching was maintained throughout the experimental trail period of 3 weeks for both halogen light and laser activation group, whereas no-light activation group presented with shade rebound after 2 weeks postbleaching.

Antimicrobial photodynamic therapy using chlorin e6 with halogen light for acne bacteria-induced inflammation.

AIMS: The present study was designed to evaluate the therapeutic potential of antimicrobial photodynamic therapy (PDT) using chlorin e6 with halogen light against acne bacteria-induced inflammation. MAIN METHODS: Highly purified chlorin e6 (Ce6), as a second generation photosensitizer, was synthesized from Spirulina chlorophyll. To evaluate the antimicrobial property of Ce6-mediated PDT with halogen light, the broth microdilution method and two-color fluorescence assay were used. The free radicals generated upon irradiating Ce6 with halogen light were measured using 2,7-dichlorofluorescin diacetate. Propionibacterium acnes was intradermally injected into the left ear of the ICR mice, and the anti-inflammatory effect of Ce6-mediated PDT with halogen light was measured by the histological examination. The expressions of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) as well as pro-inflammatory cytokines were also measured by Western blotting. KEY FINDINGS: Chlorin e6-mediated PDT with halogen light (30,000 lx) inactivated various skin bacteria, including P. acnes in a dose-dependent manner. The MIC99 value against P. acnes (KCTC3314) of Ce6 with light was >0.49 µg/ml, whereas the MIC99 for Ce6 alone was >31.25 µg/ml. Ce6-mediated PDT suppressed the expression of P. acnes-induced pro-inflammatory cytokines and iNOS, but not COX-2 in a mouse model. SIGNIFICANCE: This study showed a remarkable therapeutic effect of chlorin e6-mediated PDT with halogen light against P. acnes-induced inflammation. Our results suggest for the first time the potential of Ce6-mediated PDT with halogen light as a more effective and safer alternative treatment to antibiotic therapy against pathogenic infections of the skin.

Comparative Evaluation of the Effects of Light Intensities and Curing Cycles of QTH, and LED Lights on Microleakage of Class V Composite Restorations.

BACKGROUND: The purpose of this study was to evaluate the effects of light intensity and curing cycles of QTH and LED lights on the microleakage of Class V composite restorations. MATERIALS AND METHODS: Eighty freshly extracted human maxillary premolars were used for this study. Standardized Class V cavities were prepared and they were restored with microhybrid resin composite. According to the curing protocol, the teeth were then divided into 4 groups (n=20): QTH curing (standard and soft start modes), and LED (standard and soft start modes) irradiations. Microleakage was evaluated by immersion of the samples in 50% silver nitrate solution. The samples were then sectioned, evaluated under a stereomicroscope, and scored for microleakage. RESULTS: The results of the present in-vitro study showed mean dye leakage scores of 1.9, 1.2, 1.45 and 0.90 for Group I (QTH-Standard mode), Group II (QTH-Soft Start mode), Group III (LED-Standard mode) and Group IV (LED-Soft Start mode) respectively. CONCLUSION: It was thus concluded that the soft start polymerization showed a highly significant difference as compared to the standard curing modes of QTH and LED lights, respectively.

Comparison of halogen light and vibroacoustic stimulation on nonreactive fetal heart rate pattern.

BACKGROUND: One of the first-line assessment tools for fetal surveillance is nonstress test (NST), although it is limited by a high rate of false-nonreactive results. This study was performed to investigate if external stimulation from vibroacoustic and halogen light could help in provoking fetal responsiveness and altering NST results. MATERIALS AND METHODS: This is a clinical trial. Sampling was done from April to July 2010. One hundred pregnant women with nonreactive NST for 20 min were allocated in two groups: Vibroacoustic stimulated NST (VNST, n = 50) who received vibration from a standard fetal vibratory stimulator and halogen light stimulated NST (LNST, n = 50) who received a halogen light source for 3 and 10 sec, respectively. Results were compared together and then compared to biophysical profile (BPP) scores as a backup test. We used Mann-Whitney U test, Chi-square test, and Fisher's exact test to compare the variables in the two groups through SPSS version 14. P < 0.05 was considered as statistically significant. RESULTS: Following stimulations, 68% nonreactive subjects in halogen light stimulation group and 62% in vibroacoustic stimulation group changed to reactive patterns. Time to onset of the first acceleration (VNST: 2.17 min; LNST: 2.27 min) and the test duration (VNST: 4.91 min; LNST: 5.26 min) were the same in the two groups. In VNST 89.5% and in LNST 87.5% of nonreactivity followed by score 8 in BPP. There was no significant relation between stimulus NSTs and BPPs. CONCLUSION: Vibroacoustic and light stimulation offer benefits by decreasing the incidence of nonreactive results and reducing the test time. Both halogen light stimulation and vibroacoustic stimulation are safe and efficient in fetal well-being assessment services.

Use of light-curing units in orthodontics.

Because of their wide field of applications, light-curing units are now indispensable for orthodontists and general dentists; thus, it is important to be familiar with the various types of light-curing units, their history, specifications, advantages, and disadvantages. For this review, a search of the PubMed database (from 1966 to March 2010) was conducted using the search term "curing lights orthodontics". Eligibility of the selected studies was determined by reading the abstracts of articles identified by the search. All the articles that met the inclusion criteria were selected, and the articles collected. The reference lists of the retrieved articles were also hand searched for any applicable studies that might have been missed in the database searches. When selecting curing lights for an office, many variables need to be considered. Armed with knowledge about each curing-light category, orthodontists can evaluate their unique practice style and select the appropriate light/lights.

Comparison of shear bond strength of orthodontic brackets bonded with halogen and plasma arc light curing.

BACKGROUND: Reduced time and appropriate bond strength of brackets is one of the most important aspects of orthodontic treatments. Prolonged halogen light curing for bonding of brackets is undesirable, so the purpose of this study was to compare the shear bond strength of brackets bonded with halogen light and plasma arc system. MATERIALS AND MEHODS: This was an experimental in vitro study. A total of 60 intact premolar teeth were collected and divided into four groups. Stainless steel orthodontic brackets were bonded to them. In groups 1 and 2, curing was done using halogen light given for 20 seconds from two and four angles. In groups 3 and 4, curing was carried out using the plasma arc system for 6 seconds from two and four angles. The shear bond strength was recorded by Instron. The statistics of ANOVA, Tukey's test, and T-test were used in data analysis. RESULTS: There was a statistically significant difference in shear bond strength among the four groups (P = 0.043) and between group 1 with group 2 (P = 0.035). Yet, there was no statistically significant difference between brackets bonded with plasma arc and those bonded with halogen light or between the two groups of plasma arc. CONCLUSION: Using the plasma arc system is superior to other methods due to reduced curing time. Also, since in using the halogen light system, an increase in curing periods from different angles resulted in a significant increase in shear bond strength; it is advisable to apply the halogen light from different angles.

The effects of halogen and light-emitting diode light curing on the depth of cure and surface microhardness of composite resins.

AIM: Light-emitting diode light curing units (LED LCUs) have become more popular than halogen LCUs in routine dental restorative treatment. The aim of the study was to compare the effects of two conventional halogen (Hilux Plus and VIP) and two LED (Elipar FreeLight 2 and Smart Lite) light curing units on the depth of cure and the microhardness of various esthetic restorative materials. MATERIALS AND METHODS: The curing depth and microhardness of a compomer (Dyract Extra), a resin-modified glass ionomer (Vitremer), a packable composite (Sculpt It), an ormocer (Admira), a hybrid composite (Tetric Ceram), two microhybrid composites (Miris and Clearfil Photo Posterior) and, a nanofil composite (Filtek Supreme) were determined using a scraping method and a hardness tester. A total of 320 samples were prepared using the eight different materials (n = 10 samples for each subgroup). The scraping test was based on ISO 4049:2000. Vicker's microhardness testing was carried out using hardness tester (Zwick 3212). Data were analyzed using one-way analysis of variance (ANOVA), Bonferroni and the Kolmogorov-Smirnov tests. RESULTS: Best microhardness results were obtained with the LED light curing units and Tetric EvoCeram and Filtek Supreme achieved the highest hardness values. The nanofil composite, Filtek Supreme, showed the best curing depth results in all the tested light curing systems. CONCLUSIONS: The LEDs were found to be more successful than the halogen units with respect to both curing depth and microhardness properties.

Effect of light-curing units in shear bond strength of metallic brackets: an in vitro study

OBJECTIVES: To determine the influence of the light curing units on the shear bond strength of orthodontic brackets. MATERIAL AND METHODS: Seventy-two premolars were divided into six groups (n=12): Group I: brackets bonded with Transbond and polymerization with halogen light; Group II: Transbond and LED; Group III: Fuji Ortho and halogen light; Group IV: Fuji Ortho and LED; Group V: Fuji Ortho, without acid and halogen light; Group VI: Fuji Ortho, without acid and LED. The groups were tested to shear strength in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by ANOVA and Tukey's test. RESULTS: The composite resin presented higher shear bond strength than the resin-modified glass ionomer cement (p<0.05). The halogen light and LED sources produced similar shear bond strength (p>0.05). CONCLUSION: The shear bond strength was influenced by the material but not by the light-curing unit. The use of LED reduced the experimental time by approximately 60 percent, with the same curing efficiency.

Influência da fonte de luz fotoativadora nas propriedades ópticas de resína composta, em função da cor, espessura e tempo de armazenamento / Influence of the light-curing unit in optical properties of a composite resin according of shade, thickness, and storage time

Esse estudo se propõe a avaliar as propriedades ópticas (Fluorescência e Absorbância) da resina composta fotoativada (4 SEASONS®) utilizando aparelho fotopolimerizador convencional (luz Halógena Ulttralux - DabiAtlant), e aparelho emissor de Diodo (Radii ­ SDI e Ultralume Led 5- Ultradent), em função da fonte de luz foto-ativadora, cor, espessura e tempo de armazenamento em saliva artificial. Foram confeccionadas 5 amostras (10,0x1,0 mm) para cada grupo experimental. Para a realização do teste de Absorbância foi utilizado aparelho espectrofotômetro de luz visível (Diode Array Spectrophotometer, HP ­ Serial Number: 8452-A). Para a obtenção dos valores de fluorescência emitida pelas amostras, foi utilizado espectrofotômetro (SPEX TRIAX FLUOROLOG 3, Jobin Yvon ­ Serial Number: 0135B-3-99). Os resultados foram julgados estatisticamente conforme a interação entre os fatores de avaliação nos distintos trabalhos. Pode-se concluir que a fonte de luz fotoativadora influenciou apenas a emissão fluorescente da resina de cor TC, não tendo efeito negativo na absorbância; o aumento na espessura da amostra acarretou uma diminuição na emissão fluorescente e na absorbância de todas as cores da resina, independente da fonte de luz; e as diferentes cores da resina exibiram diferentes emissões fluorescentes e absorbância

The arm of this study is to evaluate optical properties (fluorescence and Absorbance) of a composite resin (4 SEASONS®) using light curing units (LCUs)-(QTH - Ulttralux ­ DabiAtlant and LEDs Radii ­ SDI and Ultralume Led 5- Ultradent) in function of LCUs, shade, thickness and storage times. 5 samples were prepared for each experimental group. To perform the Absorbance test, was used of UV-Vis spectrophotometer (Diode Array Spectrophotometer, HP ­ Serial Number: 8452-A). To obtain the fluorescence emission by samples, we used a spectrophotometer (SPEX TRIAX FLUOROLOG 3, Jobin Yvon ­ Serial Number: 0135B-3-99). The results were deemed statistically as the interaction between the evaluation factors in the different works. It can be concluded that the LCUs only influenced the fluorescent emission of resin color TC, having no negative effect on the absorbance; the increase in thickness of the sample decrease the fluorescent emission and absorbance for colors of the resin, independent of the LCUs; different colors of resin exhibited different fluorescent emission and absorbance

Power density of light curing units through resin inlays fabricated with direct and indirect composites / 대한치과보존학회지

OBJECTIVES: The purpose of this study was to measure the power density of light curing units transmitted through resin inlays fabricated with direct composite (Filtek Z350, Filtek Supreme XT) and indirect composite (Sinfony). MATERIALS AND METHODS: A3 shade of Z350, A3B and A3E shades of Supreme XT, and A3, E3, and T1 shades of Sinfony were used to fabricate the resin inlays in 1.5 mm thickness. The power density of a halogen light curing unit (Optilux 360) and an LED light curing unit (Elipar S10) through the fabricated resin inlays was measured with a hand held dental radiometer (Cure Rite). To investigate the effect of each composite layer consisting the resin inlays on light transmission, resin specimens of each shade were fabricated in 0.5 mm thickness and power density was measured through the resin specimens. RESULTS: The power density through the resin inlays was lowest with the Z350 A3, followed by Supreme XT A3B and A3E. The power density was highest with Sinfony A3, E3, and T1 (p < 0.05). The power density through 0.5 mm thick resin specimens was lowest with dentin shades, Sinfony A3, Z350 A3, Supreme XT A3B, followed by enamel shades, Supreme XT A3E and Sinfony E3. The power density was highest with translucent shade, Sinfony T1 (p < 0.05). CONCLUSIONS: Using indirect lab composites with dentin, enamel, and translucent shades rather than direct composites with one or two shades could be advantageous in transmitting curing lights through resin inlays.

Light-emitting diode versus halogen light curing of orthodontic brackets: a clinical study of bond failure / Colagem de brackets ortodônticos: polimerização da resina por meio de diodos emissores de luz versus luz alógena: estudo clínico de falhas de adesão

OBJECTIVE: The purpose of this study was to evaluate the clinical performance of brackets cured with two light-curing units. MATERIALS AND METHODS: Forty female patients (between12-16 years old) who required fixed appliances were included in this study. Based on the characteristics of their lower arches, study participants were divided into two groups, A and B. In group A, the composites were cured on the right side by Ultralume LED2TM and on the left side by a conventional halogen unit. In group B, the sequence was reversed. A total of 160 brackets were bonded. After 12 months, bond failure rate was evaluated. RESULTS: We found that 18 brackets in the halogen group and 13 bracketsin the LED group were debonded. No statistically significant differences were found in total bond failure rate and no enamel damage was clinically detected for either technique. CONCLUSION: Theseresults suggest that LED dose curing does not result in more bond failure when compared with conventional halogen light curing.

OBJETIVO: O objetivo deste estudo foi avaliar o desempenho clínico de brackets colados utilizando-se de duas unidades de polimerização. MATERIAL E MÉTODO: quarenta pacientes adolescentes com indicação de tratamento ortodôntico fixo foram incluídos no trabalho, divididosem dois grupos, A e B. No grupo A, o compósito foi polimerizado no lado direito com Ultralume LED 2TM e no lado esquerdo com luz halógena convencional. No grupo B, a sequencia foi invertida. Um total de 160 brackets foram colados. Após 12 meses de tratamento, avaliou-se a taxa de falhas de colagem. RESULTADOS: 18 brackets no grupo halógeno e 13 no grupo LED sofreram descolamento. Não houve diferença estatisticamente significante na taxa total de falhas e nãoforam observados danos ao esmalte em ambas as técnicas. CONCLUSÃO: Estes resultados sugerem que a fotopolimerização com LED não resulta em maiores falhas de adesão quandocomparadas com a luz halógena convencional.

Polymerization shrinkage stress of composites photoactivated by different light sources

The purpose of this study was to compare the polymerization shrinkage stress of composite resins (microfilled, microhybrid and hybrid) photoactivated by quartz-tungsten halogen light (QTH) and light-emitting diode (LED). Glass rods (5.0 mm x 5.0 cm) were fabricated and had one of the surfaces air-abraded with aluminum oxide and coated with a layer of an adhesive system, which was photoactivated with the QTH unit. The glass rods were vertically assembled, in pairs, to a universal testing machine and the composites were applied to the lower rod. The upper rod was placed closer, at 2 mm, and an extensometer was attached to the rods. The 20 composites were polymerized by either QTH (n=10) or LED (n=10) curing units. Polymerization was carried out using 2 devices positioned in opposite sides, which were simultaneously activated for 40 s. Shrinkage stress was analyzed twice: shortly after polymerization (t40s) and 10 min later (t10min). Data were analyzed statistically by 2-way ANOVA and Tukey's test (a=5 percent). The shrinkage stress for all composites was higher at t10min than at t40s, regardless of the activation source. Microfilled composite resins showed lower shrinkage stress values compared to the other composite resins. For the hybrid and microhybrid composite resins, the light source had no influence on the shrinkage stress, except for microfilled composite at t10min. It may be concluded that the composition of composite resins is the factor with the strongest influence on shrinkage stress.

Este estudo comparou a contração de polimerização de resinas compostas fotoativadas por luz halógena (QTH) e diodo emissor de luz (LED). Foram confeccionados bastões de vidro (5,0 mm x 5,0 cm), e uma de suas extremidades sofreu jateamento com óxido de alumínio, sobre a qual foi aplicado um adesivo e fotoativado com luz halógena. Os bastões de vidro foram acoplados verticalmente, em pares, em uma máquina universal de ensaios (EMIC DL-2000) e as resinas compostas aplicadas no bastão inferior. A distância entre os bastões foi padronizada em 2 mm e um extensômetro foi acoplado a eles. As resinas foram fotoativadas (n=20), sendo 10 por QTH e 10 por LED utilizando dois aparelhos posicionados em lados opostos, acionados simultaneamente por 40 s. A tensão de contração foi analisada em dois momentos: logo após a polimerização (t40s) e 10 min após (t10min). A tensão de contração apresentada por todas as resinas foi maior em t10min do que em t40s, independente da fonte ativadora. A resina de micropartículas apresentou menores valores de tensão de contração com valores estatisticamente significantes em relação às demais resinas. Para as resinas híbrida e microhíbrida não houve influência da unidade ativadora sobre a tensão de contração, com exceção para a resina de micropartículas em t10min. Concluiu-se que a composição da resina composta foi o fator que mais interferiu na tensão de contração da resina composta.

Variação térmica da câmara pulpar e do gel clareador bloqueador de infravermelho ativado com lâmpada halógena / Temperature changes of pulpal chamber and infrared-blocking bleaching gel activated with halogen light

Objetivo: Avaliar a temperatura da câmara pulpar (CP) e do gel clareador bloqueador de infravermelho na superfície dental (SUP), durante a ativação com fotopolimerizadores com lâmpadas halógenas que emitem radiação na faixa do infravermelho (IV). Metodologia: Os géis clareadores Whiteness HP Maxx (com bloqueador de IV - MX) e Whiteness HP (controle - CON) foram aplicados em 10 incisivos centrais superiores. A ativação com luz foi realizada com os fotopolimerizadores (FP) Optilight (600mW/cm2, OP) e Jet Lite (1200mW/cm2, JL), sendo quatro ativações de 40s, sem intervalo (total de 3min e 20s). As temperaturas foram aferidas a cada 40s com um termômetro digital com dois termopares tipo K, um no interior da CP e outro na superfície dental (SUP). Os dados foram analisados com ANOVA a 3 fatores (tipo de gel - TG, FP e tempo de ativação) e teste de Tukey. Resultados: Houve efeito significativo de TG e FP e para a interação FP/TG. As médias (DP) (em graus Celsius) foram: PC:[GT={MX-6,38(3,25)a, CON-7,70(2,91)b}, FC={OP-5,51(2,54)a, JL-8,56(2,93)b}]; SUR: [GT={CON-9,85(3,89)a, MX-14,21(7,76)b}, FC={OP-7,32(2,50)a, JL-16,74(5,82)b}]. Conclusões: O gel bloqueador de IV resultou em menor aquecimento da CP e maior aquecimento do gel que o controle. O FP Jet Lite promoveu maior aquecimento que o Optilight.

Purpose: To evaluate temperature changes of pulpal chamber (PC) and infrared blocking bleaching gel on dental surface (SUR) during the activation with photocuring units with halogen lights that emit radiation in the infrared (IR) range. Methods: The bleaching gels Whiteness HP Maxx (IR-blocker - MX) and Whiteness HP (control - CON) were used in ten maxillary central incisors. Light-activation was performed by using the photocuring units (FC) Optilight (600mW/cm2, OP) or Jet Lite (1200mW/cm2, JL) with four 40s-activation procedures with no interval (total time: 3min 20s). The temperature was measured each 40s using a digital thermometer with two type K thermocouples placed inside the PC and on dental surface (SUR). Data were analyzed with 3-way ANOVA (gel type - GT, FC and activation time) and Tukey's test. Results: A significant effect was found for the main factors FC and GT, and for their interaction. The means (SD) (in Celsius degree) were: PC:[GT={MX-6,38(3,25)a, CON-7,70(2,91)b}, FC={OP-5,51(2,54)a, JL-8,56(2,93)b}]; SUR: [GT={CON-9,85(3,89)a, MX-14,21(7,76)b}, FC={OP-7,32(2,50)a, JL-16,74(5,82)b}]. Conclusions: MX resulted in lower pulp chamber heating and higher gel heating than the control group. JL promoted greater heating than OP.

Effect of light-curing units and activation mode on polymerization shrinkage and shrinkage stress of composite resins

The aim of this study was to evaluate the polymerization shrinkage and shrinkage stress of composites polymerized with a LED and a quartz tungsten halogen (QTH) light sources. The LED was used in a conventional mode (CM) and the QTH was used in both conventional and pulse-delay modes (PD). The composite resins used were Z100, A110, SureFil and Bisfil 2B (chemical-cured). Composite deformation upon polymerization was measured by the strain gauge method. The shrinkage stress was measured by photoelastic analysis. The polymerization shrinkage data were analyzed statistically using two-way ANOVA and Tukey test (p<0.05), and the stress data were analyzed by one-way ANOVA and Tukey's test (p<0.05). Shrinkage and stress means of Bisfil 2B were statistically significant lower than those of Z100, A110 and SureFil. In general, the PD mode reduced the contraction and the stress values when compared to CM. LED generated the same stress as QTH in conventional mode. Regardless of the activation mode, SureFil produced lower contraction and stress values than the other light-cured resins. Conversely, Z100 and A110 produced the greatest contraction and stress values. As expected, the chemically cured resin generated lower shrinkage and stress than the light-cured resins. In conclusion, The PD mode effectively decreased contraction stress for Z100 and A110. Development of stress in light-cured resins depended on the shrinkage value.

Effects of light curing method and exposure time on mechanical properties of resin based dental materials.

OBJECTIVES: The aim of this study was to investigate microhardness and compressive strength of composite resin (Tetric-Ceram, Ivoclar Vivadent), compomer (Compoglass, Ivoclar, Vivadent), and resin modified glass ionomer cement (Fuji II LC, GC Corp) polymerized using halogen light (Optilux 501, Demetron, Kerr) and LED (Bluephase C5, Ivoclar Vivadent) for different curing times. METHODS: Samples were placed in disc shaped plastic molds with uniform size of 5 mm diameter and 2 mm in thickness for surface microhardness test and placed in a diameter of 4 mm and a length of 2 mm teflon cylinders for compressive strength test. For each subgroup, 20 samples for microhardness (n=180) and 5 samples for compressive strength were prepared (n=45). In group 1, samples were polymerized using halogen light source for 40 seconds; in group 2 and 3 samples were polymerized using LED light source for 20 seconds and 40 seconds respectively. All data were analyzed by two way analysis of ANOVA and Tukey's post-hoc tests. RESULTS: Same exposure time of 40 seconds with a low intensity LED was found similar or more efficient than a high intensity halogen light unit (P>.05), however application of LED for 20 seconds was found less efficient than 40 seconds curing time (P=.03). CONCLUSIONS: It is important to increase the light curing time and use appropriate light curing devices to polymerize resin composite in deep cavities to maximize the hardness and compressive strength of restorative materials.