Conversion degrees of resin composites using different light sources.

OBJECTIVE: The objective of this study was to compare the conversion degree of six different composite materials (Filtek Z 250, Filtek P60, Spectrum TPH, Pertac II, Clearfil AP-X, and Clearfil Photo Posterior) using three different light sources (blue light-emitting diode [LED], plasma arc curing [PAC], and conventional halogen lamp [QTH]). METHODS: Composites were placed in a 2 mm thick and 5 mm diameter Teflon molds and light cured from the top using three methods: LED for 40 s, PAC for 10 s, and QTH for 40 s. A Fourier Transform Infrared Spectroscopy (FTIR) was used to evaluate the degree of conversion (DC) (n=5). The results were analyzed with two-way analysis of variance and Tukey HSD test. RESULTS: DC was significantly influenced by two variables, light source and composite (P<.05). QTH revealed significantly higher DC values than LED (P<.05). However, there were no significant differences between DC values of QTH and PAC or between DC values of LED and PAC (P>.05). The highest DC was observed in the Z 250 composite specimens following photopolymerization with QTH (70%). The lowest DC was observed in Clearfil Photo Posterior composite specimens following photo-polymerization with LED (43%). CONCLUSIONS: The DC was found to be changing according to both light sources and composite materials used. Conventional light halogen (QTH) from light sources and Filtek Z 250 and Filtek P 60 among composite materials showed the most DC performance.

Polymerization capacity of orthodontic composites analyzed by Fourier transform infrared spectroscopy.

INTRODUCTION: The aim of this in-vitro study was to analyze the polymerization capacity of 5 orthodontic composites by determining the degree of monomer conversion (DC). METHODS: Fourier transform infrared spectroscopy was used to evaluate the DC of the orthodontic composites immediately after polymerization and after storage in artificial saliva at 37°C ± 1°C for 30 days. The resin-based adhesive composites investigated were Bisco Ortho (Bisco, Schaumburg, Ill), Heliosit Orthodontics (Ivoclar, Schaan, Liechtenstein), Kurasper F (Kuraray, Okayama, Japan), Light Bond (Reliance Orthodontic Products, Itasca, Ill), and Transbond XT (3M Unitek, Monrovia, Calif), cured with Elipar FreeLight 2 (3M ESPE, St Paul, Minn) for the testing of the DC values. Fifty cylindrical specimens were manufactured in molds. The data were analyzed by 2-factor analysis of variance (ANOVA) and Tukey HSD test. RESULTS: According to 2-way ANOVA, the DC was significantly influenced by composite type (P <0.05); after 30 days, there were no differences among the composite types for the DC. The interaction of orthodontic composites and time played a statistically significant role in the DC (P <0.05), but there was no statistically significant influence of time for the DC (P >0.05). CONCLUSIONS: The DC was found to change according to composite materials used, and Bisco Ortho showed the most DC performance. The DC of orthodontic composites is a complex process that is affected not only by inorganic filler content of the composite but also the monomer type and many other factors. Sufficient DC values of 5 commercially available orthodontic composites can be achieved with a new-generation light-emitting diode curing light.

Effects of thermocycling on the degree of cure of two lingual retainer composites.

The aim of this study was to evaluate the effects of thermocycling on the degree of cure (DC) and water sorption behavior of two lingual retainer composites. A total of 50 composite specimens, 5 mm diameter and 2 mm height, were prepared using Light Cure Retainer (LCR) (Reliance) and Transbond Lingual Retainer (TLR) (3M Unitek). After 40-second curing with a halogen light and after 24-hour water storage, the composite specimens were subjected to different thermocycling regimes. Absorbance peaks to monitor the DC were recorded using Fourier transform infrared (FTIR) spectroscopy, while water sorption was calculated in microg/mm(3). On DC, significant differences among the different thermocycling regimes were observed only for the TLR specimens (p<0.05). On water sorption behavior, an increase in the number of thermal cycles resulted in increased water sorption for both composites, but the statistical differences in these groups were not significant. On the effect of thermocycling up to 20,000 cycles, present findings showed that LCR was less affected than TLR. Further, LCR exhibited higher DC and lower water sorption values than TLR after thermal cycling.

Effect of light curing units and storage time on the degree of conversion of fissure sealants / Efeito das unidades fotopolimerizadoras e do tempo de armazenamento no grau de conversão dos selantes de fissuras

OBJECTIVE: To investigate the effect of light curing units and storage time on the degree of conversion of fissure sealants. MATERIAL AND METHOD: Three different fissure sealants were used: a resin-based pit and fissure sealant (Clinpro SealantTM), a polyacid modified resin composite (Dyract SealTM), and a resin modified glass ionomer cement (VitremerTM). Each fissure sealant was polymerized with a halogen, high intensity quartz tungsten halogen, LED. Half of the specimens were tested to assess the degree of conversion immediately after polymerization and the others after one month’s storage in artificial saliva. The degree of conversion was measured by FTIR. The data were analyzed using two way ANOVA. RESULTS: Statistical analysis of Dyract SealTM showed significant differences between the DC values of samples tested immediately and again after one month’s storage (p < 0.05). The DC values of ClinproTM increased after the storage period (p < 0.05). The DC of VitremerTM showed no change after storage (p > 0.05). Results of the curing units testing showed no significant differences among the DC of samples polymerized with LED, HQTH, OTH tested immediately and again after one month for Dyract SealTM, VitremerTM and Clinpro SealantTM (p > 0.05). CONCLUSION: Light curing units had no effect on the degree of conversion of the fissure sealants. But storage after initial light activation and polymerization for one month in artificial saliva can affects on DC of fissure sealants.

OBJETIVO: Investigar o efeito de unidades de polimerização por luz no grau de conversão dos selantes de fissuras. MATERIAL E MÉTODO: Três diferentes selantes foram utilizados: um selante resinoso de fissuras (Clinpro SealantTM, uma resina composta poliácida modificada (DyractSealTM) cimento de ionômero de vidro modificado (VitremerTM). Cada selante de fissura foi polimerizado por LED halógeno de quartzo/tungstênio. Metade dos espécimes foi testada para assegurar o grau de conversão imediatamente após polimerização e outros após um mês de armazenamento em saliva artificial. O grau de conversão foi medido por FTIR. Os resultados foram analisados por meio do ANOVA. RESULTADOS: A análise estatística do Dyract SealTMdemonstrou diferenças estatisticamente significantes entre os valores DC dos espécimes testados imediatamente e novamente após um mês de armazenamento (p < 0,05). Os valores do ClimproTM aumentaram após o período de armazenamento (p < 0.05). O DC do VitremerTM não demonstraram alterações após o armazenamento (p > 0.05). Os resultados das unidades de fotopolimerização não mostraram diferenças significantes ente DC de amostras polimerizadas com LED, HQTH, O TH testados imediatamente e novamente após um mês para o Diract SealTM, VitremerTM e Climpro SealantTM. CONCLUSÃO: Unidades de fotopolimerização não tiveram efeito no grau de conversão dos selantes de fissuras. Porém, armazenamento após ativação inicial e polimerização por um mês em saliva artificial pode afetar o DC dos selantes de fissuras.

Degree of conversion of two lingual retainer adhesives cured with different light sources.

The aim of this study was to evaluate the degree of conversion (DC) of two lingual retainer adhesives, Transbond Lingual Retainer (TLR) and Light Cure Retainer (LCR), cured with a fast halogen light, a plasma arc light and a light-emitting diode (LED) at various curing times. A conventional halogen light served as the control. One hundred adhesive samples (five per group) were cured for 5, 10 or 15 seconds with an Optilux 501 (fast halogen light), for 3, 6 or 9 seconds with a Power Pac (plasma arc light), or for 10, 20 or 40 seconds with an Elipar Freelight (LED). Samples cured for 40 seconds with the conventional halogen lamp were used as the controls. Absorbance peaks were recorded using Fourier transform infrared (FT-IR) spectroscopy. DC values were calculated. Data were analysed using Kruskal-Wallis and Mann-Whitney U-tests. For the TLR, the highest DC values were achieved in 6 and 9 seconds with the plasma arc light. Curing with the fast halogen light for 15 seconds and with the LED for 40 seconds produced statistically similar DC values, but these were lower than those with the plasma arc light. All of these light exposures yielded a statistically significantly higher DC than 40 seconds of conventional halogen light curing. The highest DC value for the LCR was achieved in 15 seconds with the fast halogen light, then the plasma arc light curing for 6 seconds. These two combinations produced a statistically significantly higher DC when compared with the 40 seconds of conventional halogen light curing. The lowest DC for the LCR was achieved with 10 seconds of LED curing. The overall DC of the LCR was significantly higher than that of the TLR. The results suggest that a similar or higher DC than the control values could be achieved in 6-9 seconds by plasma arc curing, in 10-15 seconds by fast halogen curing or in 20 seconds by LED curing.

The efficiency of different light sources to polymerize composite beneath a simulated ceramic restoration.

STATEMENT OF PROBLEM: Inadequate polymerization diminishes the physical properties of composite and compromises material strength. Newly developed light-polymerizing units (plasma arc and high intensity halogen) operate at relatively high intensity and are purported to provide optimum properties to composites in a shorter time. PURPOSE: The aim of this in vitro study was to examine the polymerization efficacy of 3 different polymerization units through a simulated ceramic restoration by determining degree of monomer conversion of a composite luting Material. MATERIAL AND METHODS: A conventional halogen light, a plasma arc light, and a high-intensity halogen light were used to polymerize a composite (Variolink II) with or without catalyst. A pressable ceramic block (5 mm in diameter, 2 mm in height) was used as an interface between the polymerizing light tip and composite. The composite/veneer combination was exposed to 2 different polymerization time protocols for each polymerization unit: (1) 20 or 40 seconds for conventional halogen light, (2) 3 or 6 seconds for plasma arc light, and (3) 10 or 20 seconds (under ramp mode) for the high-intensity halogen light. Using different light units, 120 composite specimens were evaluated (n = 5). Fourier transformation infrared spectroscopy was used to determine the level of light polymerization of the resin through the ceramic material with each of the light sources immediately after polymerization or after 24 hours. Degree of conversion was calculated as a percentage of experimentally polymerized versus maximally polymerized composite. The data were analyzed by 4-factor analysis of variance (alpha = .05). Independent t tests (alpha = .05) were used to detect differences between groups defined by the specific interacting variables. RESULTS: Degree of conversion values varied with the light source (P < .05), polymerization type (P < .05), testing time (P < .01), and exposure to each light source (P < .01). Significant interactions were present between light source and polymerization type (P = .00), light source and testing time (P = .007), and polymerization type and testing time (P = .004). The degree of conversion values were significantly higher in dual-polymerized specimens after 24 hours (P < .01), but there were no significant differences in light-polymerized specimens after 24 hours. The degree of conversion values achieved were significantly lower (P < .05) when specimens were dual polymerized by conventional halogen light and measured immediately (31.59 +/- 7.76). The degree of conversion values achieved were significantly (P < .05) higher with dual polymerization by high-intensity halogen measured after 24 hours (65.06 +/- 8.14). There were no other significant differences among groups. CONCLUSION: The highest degree of conversion values of composite were achieved with polymerization by high-intensity halogen. The plasma arc light achieved similar polymerization of composite through ceramic material in a markedly shorter period than conventional halogen light.