Variações de temperatura ocorridas durante a fotoativação de compositos odontologicos

Orientador: Simonides ConsaniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: Nos últimos anos diversas fontes de luz fotoativadoras de compósitos odontológicos têm sido introduzidas no mercado, cada qual com suas características. No entanto, muitas dúvidas permanecem com relação ao possível aumento de temperatura durante a fotoativação de compósitos restauradores odontológicos. Assim, neste estudo procurou-se avaliar a influência de fatores envolvidos durante o procedimento de fotoativação sobre o grau de elevação da temperatura e suas conseqüências em algumas propriedades dos compósitos fotoativados. Visando o melhor entendimento, a pesquisa foi dividida em três trabalhos. O primeiro trabalho verificou a variação da temperatura durante a fotoativação, com três diferentes fontes de luz, em incrementos de 2 e 3mm utilizando dois compósitos restauradores. A maior espessura de compósito (3mm) contribuiu para a diminuição estatisticamente significante (p<0,05) da variação da temperatura. O fator fonte de luz também produziu diferença estatística significante na variação da temperatura durante a fotoativação (p<0,05), onde a fonte halógena produziu valores superiores de aumento de temperatura quando comparada às fontes de luz emitida por diodos (LED) e arco de plasma de Xenônio (PAC). O fator compósito influenciou no aumento de temperatura observada. O segundo trabalho verificou o aumento de temperatura durante a fotoativação e a dureza, quando utilizadas três fontes de luz e dois compósitos restauradores. A fonte de luz LED produziu menor valor de aumento de temperatura, independente do compósito utilizado ¿ Filtek Flow ou Filtek Z250 ¿quando comparada à fonte de luz halógena, porém com valores de dureza Knoop semelhantes. A luz emitida por arco de plasma de Xenônio gerou os menores valores de elevação da temperatura. Entretanto, esta fonte de luz produziu os menores valores de dureza Knoop quando comparada às fontes LED e halógena. O terceiro trabalho verificou a temperatura e o grau de conversão quando utilizadas três fontes de luz, com tempo de fotoativação indicado pelos fabricantes, tempo necessário para igualar a densidade de energia total e tempo necessário para igualar a densidade de energia na faixa entre 450-490nm do espectro eletromagnético. Quando utilizado o tempo preconizado pelos fabricantes, as fontes de luz halógena e LED produziram valores de grau de conversão estatisticamente semelhantes. Entretanto, o aumento de temperatura gerado pelo LED foi inferior. Quando a densidade total de energia foi padronizada, a fonte PAC produziu grau de conversão similar às demais fontes. Quando a densidade de energia foi igualada na faixa entre 450-490nm, a fonte de luz LED produziu valoresde grau de conversão estatisticamente superiores aos produzidos pela fonte PAC. A fonte PAC produziu os menores valores de variação da temperatura, independente do tempo de exposiçãoAbstract: In the last years several light curing units (LCUs) have been launched in the market, each one with its own characteristics. However, there are still many doubts concerning the possible temperature increase during the photo-activation of restorative dental composites. Thus, the aim of this study was to evaluate the influence of some factors involved during the photo-activation procedure on the degree of temperature increase and its consequences in some properties of photoactivated composites. For a better understanding, the research was divided in three works. The first work verified the temperature increase during photoactivation using three different LCUs in increments of 2 and 3mm using two composites. The thicker composite (3mm) contributed to a statistically significant decrease (p<0.05) in temperature increase. The light source factor also produced significant statistical difference in the temperature increase during photo-activation (p<0.05), where the halogen LCU produced higher values of temperature increase when compared to the sources LED and PAC (p <0.05). Composite type presented a complex behavior influencing temperature increase observed herein. The second work verified the temperature increase during photo-activation and the hardness using three LCUs and two restorative composites. The LED LCU produced lower values of temperature increase, regardless the composite used - Filtek Flow or Filtek Z250 - when compared with the halogen LCU, but with similar Knoop hardness values. The PAC LCU generated the lowest values of temperature increase. However, this light source produced the lowest Knoop hardness values regardless composite used. The third work verified the temperature increase and the degree of conversion using three LCUs, with adequate photo-activation time as recommended by the manufacturer - the amount of time needed to equal the total energy density and the amount of time needed to equal the energy density in the range between 450-490nm of the electromagnetic spectrum. When the time recommended by the manufacturer was used, the light sources QTH and LED produced statistically similar values of degree of conversion. However, the temperature increase generated by LED LCU was lower. When the total energy density was standardized, the PAC LCU produced a degree of conversion similar to the other LCUs. When the energy density was equaled in range between 450- 490nnm, the LED LCU produced values of degree of conversion statistically higher to the ones produced by the PAC LCU. The PAC LCU produced the smallest values of temperature increase, regardless the exposure timeMestradoMateriais DentariosMestre em Materiais Dentário

Effect of the increase of energy density on knoop hardness of dental composites light-cured by conventional QTH, LED and xenon plasma arc

The aim of this study was to evaluate the effect of the increase of energy density on Knoop hardness of Z250 and Esthet-X composite resins. Cylindrical cavities (3 mm in diameter X 3 mm in depth) were prepared on the buccal surface of 144 bovine incisors. The composite resins were bulk-inserted and polymerized using different light-curing units and times: conventional QTH (quartz-tungsten-halogen; 700 mW/cm²; 20 s, 30 s and 40 s); LED (light-emitting diode; 440 mW/cm²; 20 s, 30 s and 40 s); PAC (xenon plasma arc; 1700 mW/cm²; 3 s, 4.5 s and 6 s). The specimens were stored at 37°C for 24 h prior to sectioning for Knoop hardness assessment. Three measurements were obtained for each depth: top surface, 1 mm and 2 mm. Data were analyzed statistically by ANOVA and Tukey's test (p0.05) were found for QTH. Knoop hardness values decreased with the increase of depth. The increase of energy density produced composites with higher Knoop hardness means using LED and PAC.Este estudo teve como objetivo avaliar o efeito do aumento da densidade de energia na dureza Knoop das resinas compostas Z250 e Esthet-X. Cavidades cilíndricas (3 mm de diâmetro X 3mm de profundidade) foram preparadas na superfície vestibular de 144 incisivos bovinos. As resinas compostas foram inseridas em incremento único e fotopolimerizadas com diferentes unidades e tempos de fotopolimerização: luz halógena convencional (700 mW/cm²; 20 s, 30 s and 40 s); LED (diodo emissor de luz; 440 mW/cm²; 20 s, 30 s and 40 s); PAC (arco de plasma de xenônio; 1700 mW/cm²; 3 s, 4,5 s and 6 s). Os espécimens foram armazenados a 37°C durante 24 h, previamente à realização das leituras de dureza Knoop. Foram realizadas três leituras por profundidade: superfície, 1 mm e 2 mm. Os dados foram submetidos à ANOVA e ao teste de Tukey (p0.05). Os valores de dureza Knoop diminuíram com o aumento da profundidade. O aumento da densidade de energia produziu compósitos com maior dureza Knoop quando o LED e o PAC foram utilizados como fontes de polimerização.21822

Evaluation of Root Perforation Treatments with Mineral Trioxide Aggregate: A Retrospective Case Series Study

This study aimed to evaluate the long-term clinical success of the use of mineral trioxide aggregate (MTA) as root canal sealer in root perforation treatments. Therefore, the dental records of 53 patients were analyzed, and treatment data was collected (age, gender, tooth location, jaw, presence or absence of radiolucent lesion, fallow up time and final radiographic/clinical assessment). All procedures were performed by a single specialist. Two examiners analyzed three radiographs from the records of each patient and classified the treatments as successful or unsuccessful. Data was analyzed statistically using parametric chi-square (P≤0.05). The examiners classified 69.8% of the cases as successful, with a follow-up time of 1-16.25 years (average: 6 years). The presence of initial radiolucent lesion was observed in 79.2% of the teeth, with a higher index of treatment in maxillary teeth (62.3%). However, the majority of successful cases were located in the maxilla (73.0%), while most unsuccessful ones were located in the mandible (62.5%) (P=0.014). There was no statistically significant difference regarding presence of previous lesions in successful (75.7%) and unsuccessful cases (87.5%) (P=0.330). In the present study, root perforations sealed with MTA had a success rate of 69.8% within 1-16.25 years. The presence of initial injury did not influence the prognosis, and maxillary teeth presented a higher success rate.Keywords: Mineral Trioxide Aggregate; Perforation; Endodontic

Do new matrix formulations improve resin composite resistance to degradation processes?

The aim of this study was to determine the degradation resistance of three new formulations-silorane-, Ormocer- and dimer-acid-based materials-and compare them to the traditional dimethacrylate-based materials. One silorane- (Filtek P90, P90), one Ormocer- (Ceram-X, CX), one dimer-acid- (N'Durance, ND) and two dimethacrylate-based (Filtek P60, P60; Tetric Ceram, TC) materials were investigated. Water sorption (Wsp) and solubility (Wsl) were determined after the materials were immersed in water for 28 days. Knoop hardness (KH) was determined before and after 24 h immersion in pure ethanol. The flexural-strength (FS) was determined by the bending test after one-week storage in a dry environment or after one-week immersion in pure ethanol. Data were submitted to analysis of variance (ANOVA) and Tukey's test (95%). The three new formulations showed lower Wsp than the dimethacrylate-based formulation. CX (0.50 &#177; 0.17%) and ND (0.72 &#177; 0.19%) exhibited the lowest Wsp, whereas P90 (0.02 &#177; 0.03%) and P60 (0.04 &#177; 0.03%) showed the lowest Wsl. All resins showed reduced Knoop hardness number (KHN) after ethanol immersion. P60 presented the lowest decrease in KH value (19 &#177; 5%). TC (48 &#177; 3%) and P90 (39 &#177; 9%) showed the highest KHN decrease after ethanol storage. The FS of CX, ND and TC were affected by ethanol storage. The new formulations did not improve the degradation resistance, as compared with the traditional methacrylate-based materials.41041

Aplication of alternative photoinitiator systems in dental resin composites

Orientador: Simonides ConsaniTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: O presente estudo teve como objetivo investigar a aplicação de sistemas fotoiniciadores alternativos em compósitos odontológicos. Para melhor entendimento, o trabalho foi dividido em três Capítulos. O Capítulo 1 teve como objetivos específicos 1) avaliar a taxa de polimerização máxima (TPmax), grau de conversão (GC), dureza e grau de amarelo (GA) de compósitos contendo canforoquinona (CQ), fenil-propanodiona (PPD) ou a combinação (CQ/PPD) em três diferentes concentrações; 2) avaliar a densidade de potência absorvida (DPabs, em mW/cm3) pelos sistemas fotoiniciadores (parâmetro utilizado para estimar a correlação entre os espectros de absorção dos fotoiniciadores e o espectro emitido pela fonte de luz). As hipóteses testadas foram: a) PPD e/ ou CQ/PPD poderia reduzir GA e TPmax sem reduzir GC e dureza; b) TPmax, GC e dureza são dependentes da DPabs. TP foi avaliada por calorimetria diferencial de varredura (DSC), GC por espectroscopia transformada de Fourier (FTIR), dureza por endentação Knoop e GA por um colorímetro (eixo b). Concluiu-se que: 1) apenas CQ/PPD reduziu a TPmax sem reduzir GC e dureza; 2) uma redução do GA foi possível apenas quando PPD foi utilizada em baixa concentração e 3) TPmax, GC e dureza são dependentes da DPabs. O Capítulo 2 avaliou o efeito da proporção de amina na TPmax, GC, dureza Knoop, sorção de água (Wsr), solubilidade em água (Wsl) e alterações de cor (?E) em função do tempo para compósitos formulados com CQ, PPD e CQ/PPD. Foram testadas as proporções fotoiniciador:amina 2:1, 1:1, 1:1.5 e 1:2, em peso. TPmax foi avaliada por DSC, GC por DSC e FTIR, dureza por endentação Knoop, Wsr e Wsl adaptadas da ISO 4049; e ?E por um colorímetro. Quanto maior a proporção de amina empregada, maior foi GC, TPmax e dureza, e menor foi Wsl, independentemente do fotoiniciador usado. O uso do PPD resultou em piores propriedades do que CQ e CQ/PPD. Diversos fatores afetam ?E. A maior quantidade de amina usada foi responsável pelos maiores níveis de amarelo para as formulações de CQ e CQ/PPD. Concluindo, o uso do PPD sozinho não foi vantajoso, se comparado com CQ e CQ/PPD; a eficiência do fotoiniciador foi dependente da proporção de amina empregada, independentemente do tipo de fotoiniciador; a quantidade de amina influenciou o GA para compósitos formulados com CQ e CQ/PPD. O estudo descrito no Capítulo 3 verificou a influência dos diferentes sistemas fotoiniciadores (CQ, PPD e CQ/PPD) no desenvolvimento da tensão de polimerização e propriedades resultantes (GC e densidade de ligações cruzadas, DLC) de compósitos restauradores. A hipótese testada foi de que PPD e/ou CQ/PPD poderia reduzir a tensão de polimerização sem reduzir GC e DLC. TPmax foi aferida por DSC e a tensão por um sistema de alavanca (Bioman). GC, avaliado por FTIR, e DLC (medido indiretamente pelo coeficiente inchamento) foram determinados a partir das amostras removidas do Bioman. De acordo com os resultados, pode-se concluir que o sistema CQ/PPD foi capaz de reduzir a taxa máxima de tensão sem reduzir o GC e a DLCAbstract: The aim of the present study was to evaluate the application of alternative photoinitiators in dental resin composites. The work was divided into two Chapters in order to make the objectives clearer. The specific aims of the Chapter 1 were: 1) to evaluate the maximum rate of polymerization (Rpmax), degree of conversion (DC), hardness and yellowing of resin composites formulated with camphorquinone (CQ), phenylpropanedione (PPD) or CQ/PPD at three different concentrations; 2) to evaluate the absorbed power density (PDabs, in mW/cm3) by the different systems (parameter used to estimate the correlation between photoinitiators¿ absorption and light emission spectra). The hypotheses tested were: a) PPD and/ or CQ/PPD could reduce the yellowing degree and Rpmax without reduction in the DC and hardness; b) Rpmax, DC and hardness are directly dependent on the PDabs. Rate of polymerization was evaluated with differential scanning calorimetry (DSC), DC with Fourier transformed infrared spectroscopy (FTIR), hardness with Knoop indentation and yellowing with a chromameter (b axis). According the results, it was concluded that: 1) CQ/PPD reduced the Rpmax without affecting DC and hardness; 2) the yellowing reduction by PPD formulations was possible only at low concentration and 3) Rpmax, DC and hardness are dependent on the PDabs. The 2nd study evaluated the effect of amine ratio on the Rpmax, DC, hardness, water sorption (Wsp), water solubility (Wsl) and color changes (?E) over time of composites formulated with CQ, PPD and CQ/PPD. Photoinitiator:amine ratios 2:1, 1:1, 1:1.5 and 1:2, by weight, were used in experimental composites. Rpmax wasevaluated with DSC, DC with DSC and FTIR, hardness with Knoop indentation, Wsp and Wsl adapted from ISO 4049; and ?E with a chromameter. The results showed that the higher the amine ratio, the higher was DC, Rpmax, hardness and lower was Wsl, regardless of the photoinitiator type. The use of PPD alone resulted in poorer properties than CQ and CQ/PPD. Many factors seem to affect the ?E. The higher was the amine ratio, the higher was the yellowing for CQ and CQ/PPD formulations. Thus, it is possible to conclude that the use of PPD alone was not advantageous; the photoinitiator efficiency was dependent on the amine ratio, regardless of the photoinitiator type; and the amine ratio affected the yellowing for composites with CQ and CQ/PPD. The third study evaluated the influence of different photoinitiator systems (CQ, PPD or CQ/PPD) on the stress of polymerization development and composites¿ resultant properties (DC and crosslinking density, CLD). The hypothesis tested was that PPD and/ or CQ/PPD could reduce the stress development without affecting the final DC and CLD. Besides the DSC evaluation, stress development was checked with a cantilever apparatus (Bioman), DC with a FTIR and CLD was indirectly assessed trough the swelling coefficient. The combination CQ/PPD reduced the rate of stress development without reduction on the DC and CLDDoutoradoMateriais DentariosDoutor em Materiais Dentário

Temperature Change And Hardness With Different Resin Composites And Photo-activation Methods.

This study verifies whether there is any temperature change during photoactivation of two resin composites (Filtek Z250 and Filtek Flow) with three different light curing methods (conventional halogen light curing unit, light emitting diodes curing unit and xenon plasma arc curing unit) and the relationship of temperature change with resin composite hardness. A type-K thermocouple registered the temperature rise peak in an elastomer mold during photoactivation. After photoactivation, the specimens were submitted to Knoop hardness test performed by an indenter (HMV-2000) under a load of 50g for 15 seconds. Both the temperature change data and results of the Knoop hardness test were submitted to ANOVA and Tukey's test at the 5% significance level. No statistical differences in temperature rise were recorded for the different composites following processing by light curing unit (p>0.05). The conventional halogen source produced statistically higher temperatures (p<0.05) than the other units. The plasma arc source promoted statistically lower (p<0.05) Knoop hardness values and temperature changes than the other light curing units.30516-2