Patrícia Alves Ferreira Amato1, Renato Parsekian Martins2, Carlos Alberto dos Santos Cruz3, Marisa Veiga Capella4, Lídia Parsekian Martins5. 1. Private practice, Ribeirão Preto, São Paulo, Brazil. 2. Invited professor, Orthodontic Program, Araraquara School of Dentistry, São Paulo State University, Araraquara, São Paulo, Brazil; private practice, Araraquara, São Paulo, Brazil. Electronic address: dr_renatopmartins@hotmail.com. 3. Associate professor, Department of Dental Materials and Prosthodontics, Araraquara School of Dentistry, São Paulo State University, Araraquara, São Paulo, Brazil. 4. Assistant professor, Department of Physical Chemistry, Araraquara Institute of Chemistry, São Paulo State University, Araraquara, São Paulo, Brazil. 5. Chairman, Department of Orthodontics, Araraquara School of Dentistry, São Paulo State University, Araraquara, São Paulo, Brazil.
Abstract
INTRODUCTION: The aim of this study was to assess the influence of curing time and power on the degree of conversion and surface microhardness of 3 orthodontic composites. METHODS: One hundred eighty discs, 6 mm in diameter, were divided into 3 groups of 60 samples according to the composite used-Transbond XT (3M Unitek, Monrovia, Calif), Opal Bond MV (Ultradent, South Jordan, Utah), and Transbond Plus Color Change (3M Unitek)- and each group was further divided into 3 subgroups (n = 20). Five samples were used to measure conversion, and 15 were used to measure microhardness. A light-emitting diode curing unit with multiwavelength emission of broad light was used for curing at 3 power levels (530, 760, and 1520 mW) and 3 times (8.5, 6, and 3 seconds), always totaling 4.56 joules. Five specimens from each subgroup were ground and mixed with potassium bromide to produce 8-mm tablets to be compared with 5 others made similarly with the respective noncured composite. These were placed into a spectrometer, and software was used for analysis. A microhardness tester was used to take Knoop hardness (KHN) measurements in 15 discs of each subgroup. The data were analyzed with 2 analysis of variance tests at 2 levels. RESULTS: Differences were found in the conversion degree of the composites cured at different times and powers (P <0.01). The composites showed similar degrees of conversion when light cured at 8.5 seconds (80.7%) and 6 seconds (79.0%), but not at 3 seconds (75.0%). The conversion degrees of the composites were different, with group 3 (87.2%) higher than group 2 (83.5%), which was higher than group 1 (64.0%). Differences in microhardness were also found (P <0.01), with lower microhardness at 8.5 seconds (35.2 KHN), but no difference was observed between 6 seconds (41.6 KHN) and 3 seconds (42.8 KHN). Group 3 had the highest surface microhardness (35.9 KHN) compared with group 2 (33.7 KHN) and group 1 (30.0 KHN). CONCLUSIONS: Curing time can be reduced up to 6 seconds by increasing the power, with a slight decrease in the degree of conversion at 3 seconds; the decrease has a positive effect on the surface microhardness.
INTRODUCTION: The aim of this study was to assess the influence of curing time and power on the degree of conversion and surface microhardness of 3 orthodontic composites. METHODS: One hundred eighty discs, 6 mm in diameter, were divided into 3 groups of 60 samples according to the composite used-Transbond XT (3M Unitek, Monrovia, Calif), Opal Bond MV (Ultradent, South Jordan, Utah), and Transbond Plus Color Change (3M Unitek)- and each group was further divided into 3 subgroups (n = 20). Five samples were used to measure conversion, and 15 were used to measure microhardness. A light-emitting diode curing unit with multiwavelength emission of broad light was used for curing at 3 power levels (530, 760, and 1520 mW) and 3 times (8.5, 6, and 3 seconds), always totaling 4.56 joules. Five specimens from each subgroup were ground and mixed with potassium bromide to produce 8-mm tablets to be compared with 5 others made similarly with the respective noncured composite. These were placed into a spectrometer, and software was used for analysis. A microhardness tester was used to take Knoop hardness (KHN) measurements in 15 discs of each subgroup. The data were analyzed with 2 analysis of variance tests at 2 levels. RESULTS: Differences were found in the conversion degree of the composites cured at different times and powers (P <0.01). The composites showed similar degrees of conversion when light cured at 8.5 seconds (80.7%) and 6 seconds (79.0%), but not at 3 seconds (75.0%). The conversion degrees of the composites were different, with group 3 (87.2%) higher than group 2 (83.5%), which was higher than group 1 (64.0%). Differences in microhardness were also found (P <0.01), with lower microhardness at 8.5 seconds (35.2 KHN), but no difference was observed between 6 seconds (41.6 KHN) and 3 seconds (42.8 KHN). Group 3 had the highest surface microhardness (35.9 KHN) compared with group 2 (33.7 KHN) and group 1 (30.0 KHN). CONCLUSIONS: Curing time can be reduced up to 6 seconds by increasing the power, with a slight decrease in the degree of conversion at 3 seconds; the decrease has a positive effect on the surface microhardness.
Authors: Lorena Marques Ferreira de Sena; Dayanne Monielle Duarte Moura; Isabelle Helena Gurgel de Carvalho; Leopoldina de Fatima Dantas de Almeida; Nathalia Ramos da Silva; Rodrigo Othávio de Assunção E Souza Journal: J Orofac Orthop Date: 2022-10-17 Impact factor: 2.341
Authors: Andrés Fernando Montenegro Arana; Barbara Justus; Andrés DÁvila-SÁnchez; Michele de Oliveira Sugahara; Ulisses Coelho; Paulo Vitor Farago; Cesar Arrais Journal: Dental Press J Orthod Date: 2021-03-10