Telmo Bandeira Berthold

Degree of conversion and hardness of an orthodontic resin cured with a light-emitting diode and a quartz - tungsten - halogen light

The purpose of this study was to assess the influence of two light units, a quartz-tungsten-halogen (QTH) and a light-emitting diode (LED), on the hardness and degree of conversion of an orthodontic composite resin. Sixty specimen disks were prepared from Transbond XT composite resin (3M Unitek) and light cured for 10, 20, and 30 seconds with a QTH (Curing Light XL 3000, 3M Unitek) or a LED (Ortholux, 3M Unitek) light-curing unit for 5, 10, and 15 seconds. Composite resin polymerization was evaluated by Fourier-transform infrared (FTIR) spectrophotometry and Knoop hardness number (KHN). The results were statistically analysed using analysis of variance and Tukeys multiple comparisons test (alpha = 0.05). The highest KHN was obtained with the QTH at 30 (25.19 KHN) and 20 (24.01) seconds, which did not differ statistically, and in the LED 15 second (21.86) group. The QTH 10 second group (20.53) did not differ statistically from the QTH 20 second or the LED 5 (19.96) and 15, or 10 second (18.95) groups. According to FTIR, there was no statistical difference for the degree of conversion among the groups, QTH 10 (43.42 per cent), QTH 20 (46.12 per cent), QTH 30 (45.30 per cent), LED 10 (47.02 per cent), or LED 15 (47.24 per cent) seconds. The lowest degree of conversion was obtained for the LED 5 second group (38.97 per cent), which did not differ statistically from the QTH 10 second group. Light curing with the LED resulted in a reduction of 50 per cent in the time recommended for use of the QTH light with the composite resin, Transbond XT.

Treatment of Class II division 1 malocclusion in a patient with traumatized central incisors: a case report

OBJETIVO: O objetivo deste trabalho e relatar o caso clinico de uma paciente portadora de maloclusao Classe II divisao 1 com incisivos centrais superiores traumatizados com reabsorcao interna e externa e a opcao de tratamento de extrai-los, seguido de fechamento do espaco com a mesializacao dos incisivos laterais superiores. DESCRICAO DO CASO: Paciente do sexo feminino com 10 anos de idade relatou trauma facial, apos queda de bicicleta, e avulsao e reimplante dos incisivos centrais superiores aos 9 anos de idade. Optou-se pela extracao dos incisivos centrais superiores mesializando os incisivos laterais para a posicao dos centrais, restaurando-os para ficar esteticamente aceitavel. CONCLUSAO: A extracao dos incisivos centrais superiores nao e um protocolo de tratamento comum. Porem, para pacientes portadores de maloclusao Classe II divisao 1 com incisivos centrais traumatizados e com reabsorcao radicular externa e interna pode ser uma boa solucao para a correcao do sobrepasse aumentado.

Influence of plasma arc and quartz-tungsten-halogen curing lights on the polymerization of orthodontic composite resin

Purpose: To analyze, in vitro, the influence of a quartz-tungsten-halogen (QTH) and a plasma arc (PAC) on the degree of conversion and hardness of a composite resin, as well as the heat generated by the units. Methods: Transbond XT disks were prepared and light-cured for 10, 20 and 30 seconds with a QTH (Curing Light XL 3000) or with a PAC (Apollo 95E) for 1, 2 and 3 seconds. The composite resin polymerization was evaluated by infrared spectrophotometry (FTIR) and Knoop hardness number (KHN). The temperature at the curing tip was evaluated. The results were analyzed using ANOVA and Tukey test (α=0.05). Results: According to FTIR and KHN, the polymerization of the composite resin was statistically higher with the QTH. The temperature obtained with the QTH 20 s (45.44oC) and 30 s (45.84oC) was statistically higher than the QTH 10 s (39.90oC). The PAC 1 s (27.12oC), 2 s (28.48oC) and 3 s (29.96oC) presented the lowest temperature and did not differ statistically among them. Conclusion: Transbond XT light-activated for 10, 20 and 30 seconds with the QTH presented higher degree of conversion and hardness in comparison with those obtained with the PAC for 1, 2 and 3 seconds, and the QTH generated more heat than the PAC.