ABSTRACT
Objective: To determine the force decay and discoloration in Generation I and Generation II elastomeric chain on artificial saliva immersion. Material and methods: Generation I and Generation II elastomeric chains stretched on an acrylic board and immersed in artificial saliva for 1, 7, 14, 21, and 28 days according to the group of days. On each specified day, the force of each sample measured by an orthodontic force gauge and the magnitude of the force obtained is entered to the formula to find out the force decay in percentage, whereas discoloration of each sample analyzed by the color reader with CIE Lab analysis. Results: The force decay between Generation I and Generation II elastomeric chains showed a statistically significant difference in every group of days, in which Generation II is more effective in maintaining stretch force. Similar to force decay, the discoloration in Generation I elastomeric chains on the 14th day showed significant value and Generation II elastomeric chains were more stable in maintaining color compared to Generation I. Conclusions: over the entire research period time, Generation II elastomeric chains are more stable in maintaining stretch forces and color compared to Generation I elastomeric chains. (AU)
Objetivo: Determinar a queda de força e descoloração nos elásticos ortodônticos tipo corrente de Geração I e Geração II na imersão em saliva artificial. Material e métodos: Elásticos Geração I e Geração II foram esticados em placas de acrílico e imersas em saliva artificial por 1, 7, 14, 21 e 28 dias, de acordo com o grupo de dias. Em cada dia especificado, a força de cada amostra medida por um medidor de força ortodôntica e a magnitude da força obtida são inseridos na fórmula para descobrir sua queda em porcentagem, enquanto a descoloração de cada amostra foi analisada pelo leitor de cores "CIE Lab". Resultados: A queda da força entre os elásticos Geração I e Geração II apresentou diferença estatisticamente significativa em todos os grupos de dias, sendo que a de Geração II foi mais efetiva na manutenção da força de alongamento. Semelhante à queda de força, a descoloração nos elásticos da Geração I mostrou um valor significativo no 14º dia, e elásticos da Geração II foram mais estáveis na manutenção da cor em comparação com a Geração I. Conclusões: durante todo o período de pesquisa, os elásticos tipo corrente da Geração II foram mais estáveis na manutenção das forças de alongamento e da cor em comparação com os elásticos da Geração I (AU)
Subject(s)
Saliva, Artificial , Tooth Movement Techniques , Bite ForceABSTRACT
Objective To study the safety and effectiveness of the double chain method on the closure of the space of the teeth. Methods Totally 72 cases of different maxillary and mandible dentition space were included in the study. The pulp vitality was measured before and after treatment, the maxillary and mandible first molar teeth. All values were compared to assess the safety of dental pulp vitality. There were 36 cases in tooth extraction group and non-tooth extraction group.The observation period was 4 weeks, the changes of the alveolar space between maxillary and mandible teeth in adult and minor groups were measured before and after treatment. The difference of the total groove spacing before and after treatment were calculated and compared, to assess the effectiveness of space closure. Results In all 72 patients, there was no significant difference in the vitality of the pulp before and after treatment (P>0. 05). Compared to before treatment, the sum of the distance between the upper and lower mandibular groove using the double chain method was significantly reduced for both adult and juvenile patients in the four week tooth extraction group and the nontooth extraction group,the difference was statistically significant (P<0. 05). Conclusion Double chain closed teeth space does not cause pulp degeneration and necrosis. It is safe in clinical practice. Double chain method is effective, and can simplify the clinical operation.
ABSTRACT
OBJECTIVE: This study was performed to investigate an appropriate degree of prestretch for orthodontic synthetic elastomeric chains focusing on time-dependent viscoelastic properties. METHODS: Orthodontic synthetic elastomeric chains of two brands were prestretched to 50, 100, 150, and 200% of the original length in one and three cycles, and the hysteresis areas of the obtained stress-strain curves were determined. Acrylic plates were employed to maintain constant strain during the experiment. A total of 180 samples were classified into nine groups according to brand, and their stresses and permanent deformations were measured immediately after prestretch (0 hour), after 1 hour and 24 hours, and after 1, 2, 3, 4, 5, 6, 7, and 8 weeks. The relationship between stress relaxation and permanent deformation was investigated for various degrees of prestretch, and the estimated stress resulting from tooth movement was calculated. RESULTS: The degree of prestretch and the stress relaxation ratio exhibited a strong negative correlation, whereas no correlation was found between the degree of prestretch and the average normalized permanent strain. The maximal estimated stress was observed when prestretch was performed in three cycles to 200% of the original length. CONCLUSIONS: Although prestretch benefited residual stress, it did not exhibit negative effects such as permanent deformation. The maximal estimated stress was observed at the maximal prestretch, but the difference between prestretch and control groups decreased with time. In general, higher residual stresses were observed for product B than for product A, but this difference was not clinically significant.
Subject(s)
Elastomers , Relaxation , Tooth Movement TechniquesABSTRACT
The hypothesis tested in this study was that intraoral exposure of elastomeric chains alters their tensile strength. For such purpose, it was evaluated the in situ behavior of different elastomeric chains stretched for 3 weeks. Three kinds of elastomeric chains, Plastic chain (PC), Memory chain (MC) and Super slick chain (SSC), were randomly placed in 3 quadrants of 13 patient in a fixed distance of 16 mm and mean initial force of 180 g. Tensile testing was performed in an universal testing machine at different intervals: initial, 1 h, 24 h, 1 week, 2 weeks and 3 weeks. A two-way ANOVA test was performed to identify the influence of both material and time on the force decrease. A subsequent one-way ANOVAtest with the Tukey's post hoc test was used to identify statistically significant intragroup and intergroup remaining force (g and %) differences at 5% significance level. The effect of both the material and the time factors were significant. All groups showed significant force decrease after the 1-h period (23% for PC and 14% for MC and SSC). At the end of the 3-week period, the remaining force was 57% (96 g), 67% (129 g) and 71% (125 g) for PC, MC and SSC, respectively. In conclusion, intraoral exposure of elastomeric chains altered their tensile strength. In general, the greater force decrease occurred within the first hour. The remaining force of the enhanced chains measured at each time interval was greater than the conventional one (PC). After 3 weeks, only the enhanced chains maintained the force applied over 100 g.
A hipótese testada foi que a exposição dos elásticos em cadeia ao meio bucal altera sua força de tensão. Portanto, o objetivo deste estudo foi avaliar o comportamento, in situ, de diferentes cadeias elastoméricas quando tensionadas durante 3 semanas. Três tipos de elásticos em cadeia Plastic Chain (PC), Memory Chain (MC) e Super Slick Chain (SSC) foram inseridos aleatoriamente em 3 dos quadrantes de 13 pacientes com distância fixa de 16 mm e força inicial de 180 g. Foi realizado ensaio de tração em uma máquina de ensaio universal EMIC nos seguintes intervalos: inicial, 1 h, 24 h, 1 semana, 2 semanas e 3 semanas. O teste ANOVA a dois critérios foi aplicado para verificar a influência do material e do tempo na degradação da força. Subsequentemente, foi utilizado o teste ANOVA a um critério e pós-teste de Tukey para identificar diferenças estatísticas (p<0,05), intra-grupo e inter-grupo, na força remanescente (g e %). Tanto o material quanto o tempo tiveram efeito significativo na degradação da força. Todos os grupos mostraram diminuição significativa da força depois de 1 h sob tensão (23% para o PC e 14% para o MC e SSC). Ao final do período de 3 semanas, a força remanescente foi de 57% (96 g), 67% (129 g) e 71% (125 g) para o PC, MC e SSC, respectivamente. A exposição dos elásticos em cadeia ao meio bucal alterou a força de tensão. No geral, a maior diminuição da força ocorreu na primeira hora. A força remanescente testada em cada intervalo foi maior para os elásticos reforçados (MC e SSC) do que para o elástico convencional (PC). Após 3 semanas, apenas os elásticos reforçados mantiveram a força acima de 100 g.
Subject(s)
Humans , Dental Materials/chemistry , Elastomers/chemistry , Orthodontic Appliances , Dental Stress Analysis/instrumentation , Elasticity , Materials Testing , Orthodontic Appliance Design , Orthodontic Space Closure/instrumentation , Plastics/chemistry , Stress, Mechanical , Tensile Strength , Time Factors , Tooth Movement Techniques/instrumentationABSTRACT
INTRODUÇÃO: os materiais elastoméricos são considerados importantes fontes de força para a movimentação ortodôntica. OBJETIVO: avaliar a liberação de tensões de quatro marcas comerciais de elásticos ortodônticos em cadeia (Morelli, Ormco, TP e Unitek), em função do tempo, quando mantidas tensionadas por uma força inicial de 150g e imersas em saliva artificial a 37ºC. MÉTODOS: os elásticos em cadeia foram tensionados entre pinos de aço, fixados em uma placa de resina acrílica à distância de 15mm (Morelli e TP) e de 16mm (Unitek e Ormco), ambas medidas correspondendo a uma força de 150g. A leitura da quantidade de tensão liberada pelos elásticos foi realizada com um dinamômetro nos intervalos 30 minutos, 7, 14 e 21 dias. Os dados obtidos foram submetidos à análise de variância (ANOVA) (p<0,05) e ao teste de Comparações Múltiplas de Tukey. RESULTADOS: após 30 minutos de teste, verificou-se redução entre 19 por cento e 26,67 por cento na quantidade de tensão liberada pelos elásticos; e entre 36,67 por cento e 57 por cento após 21 dias de estiramento constante. CONCLUSÕES: os elásticos em cadeia que apresentaram comportamento mais estável foram os da marca TP, pois relataram menor perda de potencial elástico nos intervalos de tempo testados. Os da marca Unitek demonstraram maior redução de tensão liberada. As marcas Ormco e Morelli obtiveram resultados semelhantes entre si.
INTRODUCTION: Elastomeric materials are considered important sources of orthodontic forces. OBJECTIVE: To assess force degradation over time of four commercially available orthodontic elastomeric chains (Morelli, Ormco, TP and Unitek). METHODS: The synthetic elastics were submerged in 37 ºC synthetic saliva and stretched by a force of 150 g (15 mm - Morelli and TP; 16mm - Unitek and Ormco). With a dynamometer, the delivered force was evaluated at different intervals: 30 minutes, 7 days, 14 days and 21 days. The results were subjected to ANOVA and Tukey's test. RESULTS: There was a force decay between 19 percent to 26.67 percent after 30 minutes, and 36.67 percent to 57 percent after 21 days of activation. CONCLUSIONS: TP elastomeric chains exhibited the smallest percentage of force decay, with greater stability at all time intervals tested. Meanwhile, the Unitek chains displayed the highest percentage of force degradation, and no statically significant difference was found in force decay between Ormco and Morelli elastomeric chains during the study period.
Subject(s)
Biomedical and Dental Materials , Elasticity , Elastomers , Mouthwashes , Dental Materials/analysis , Polymers , Saliva, Artificial , OrthodonticsABSTRACT
The purpose of this study was to evaluate the force degradation rate of synthetic elastomeric chains during space closing phase of orthodontic treatment. Two kinds of synthetic elastomeric chains(RMO, 3M) were selected which were commonly used in clinics. All of the samples were extended and tested for 4 weeks under the simulated intraoral condition. The results can be summarized as follows : 1. Time related residual force showed typical logarithm function. Residual force after 4 weeks was 41.2~64.6 % of original force, and difference between two kinds of elastomeric chain existed. 2. Elastic force decreased greatly during first 10 minutes, so 20~25 % of original force disappeared. After that, this decreasing tendency was diminished significantly, average rate of elastic force after 1 week to 4 weeks were 1.5 % demonstrating rather constant force. 3. Even though the same brand of elastomeric chiain was used, as extension rate of elastomeric chain increased, force degradation rate increased by decreasing of residual force.
Subject(s)
ElastomersABSTRACT
Forces needed for orthodontic tooth movement are obtained from various appliances such as orthodontic wires or elastic rubber. Orthodontic elastic rubber is widely used clinically, but permanent deformation and force decay may occur from the environmental changes, time of clinical use and the extent of the stertch, making the prediction of force being applied difficult. The present study examined and compared the changes in residual force between three brands of elastomertc chains (Ormco : Generation II Power Chains ; brand A, RMO : Energy-Chain ; brand B, Unitek : Alastik ; brand C) under various environmental conditions, amout of inital force, types of elastomer and the rate of extension. The characteristic physical properies of the elastomeric chains were as follows. 1. In all three brands, the residual force ratio was largest when the chains were stored in air, with no difference between water and saliva. 2. In all three brands, after 24 hours, there was no statistical difference in residual force ratio according to the initial force level. 3. In Brand A and B, the presence of filament had no correlation with the residual force ratio. In Brand C force decay was more severe when the chain contained filament. 4. In each brand, rate of extension had no effect on residual force ratio. 5. Brand B showed relatively higher residual force ratio compared to other brands.