Shear Bond Strength Of Metallic Brackets Bonded With A New Orthodontic Composite

Aim: The aim of this study was to assess the shear bond strength of orthodontic brackets in different enamel surfaces using the Transbond Plus Color Change composite (TPCC-3M Unitek), and to analyze the Adhesive Remnant Index (ARI). Methods: Seventy-two human premolars were divided into six groups (n = 12), as follows: Group 1(control) - Transbond XT conventional; in Groups 2 to 6, TPCC was used under the following enamel treatment conditions: phosphoric acid and XT-primer; Transbond Plus Self-Etching Primer (TPSEP); phosphoric acid only; phosphoric acid, XT-primer and saliva; and TPSEP and saliva, respectively. Twenty-four hours after bonding, the brackets were debonded with an Instron machine at a crosshead speed of 0.5 mm/min, and ARI was evaluated by using a stereoscopic magnifying glass. Results: The mean shear strength values (MPa) for Groups 1 to 6 were 24.6, 18.7, 17.5, 19.7, 17.5 and 14.8, respectively. Data were submitted to ANOVA and Tukey’s test (? = 0.05). Group 1 had significantly higher shear bond strength values than Groups 3, 5, and 6 (p 0.05). No statistically significant differences (p > 0.05) were found between Groups 2, 3, 4, 5 and 6. Conclusions: Bracket bonding using TPCC showed adequate adhesion for clinical use, and the type of enamel preparation had no influence.8276-8

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

Clinical evaluation of the failure rates of metallic brackets

The aim of this study was to evaluate in vivo the bonding of metallic orthodontic brackets with different adhesive systems. Material and methods: Twenty patients (10.5-15.1 years old) who had sought corrective orthodontic treatment at a University Orthodontic Clinic were evaluated. Brackets were bonded from the right second premolar to the left second premolar in the upper and lower arches using: Orthodontic Concise, conventional Transbond XT, Transbond XT without primer, and Transbond XT associated with Transbond Plus Self-etching Primer (TPSEP). The 4 adhesive systems were used in all patients using a split-mouth design; each adhesive system was used in one quadrant of each dental arch, so that each group of 5 patients received the same bonding sequence. Initial archwires were inserted 1 week after bracket bonding. The number of bracket failures for each adhesive system was quantified over a 6-month period. Results: The number of debonded brackets was: 8- Orthodontic Concise, 2- conventional Transbond XT, 9- Transbond XT without primer, and 1- Transbond XT + TPSEP. By using the Kaplan-Meier methods, statistically significant differences were found between the materials (p=0.0198), and the Logrank test identified these differences. Conventional Transbond XT and Transbond XT + TPSEP adhesive systems were statistically superior to Orthodontic Concise and Transbond XT without primer (p<0.05). There was no statistically significant difference between the dental arches (upper and lower), between the dental arch sides (right and left), and among the quadrants. Conclusions: The largest number of bracket failures occurred with Orthodontic Concise and Transbond XT without primer systems and few bracket failures occurred with conventional Transbond XT and Transbond XT+TPSEP. More bracket failures were observed in the posterior region compared with the anterior region.20222823

Color stability and gloss of esthetic restorative materials after chemical challenges

This study evaluated gloss and color changes of esthetic restorative materials subjected to different acidic beverages. Specimens of resin composites (Z350XT (Z350), IPS Empress Direct (ED), Charisma Diamond (CD)) were prepared and the initial surface gloss and color (ΔE) were measured (n=10). Then, the specimens were immersed in 4 mL of each of the different beverages (cranberry juice; Coca-Cola; coffee or artificial saliva) during 15 min, 3x/day for 14 days and new gloss and color readings were obtained. Color change was evaluated with the ΔE formula and gloss change values were obtained by the formula: (final gloss - initial gloss). Data was submitted to two-way ANOVA followed by Tukey’s post hoc test (a=0.05). CD showed the lowest color change among resin composites. The highest ΔE values were obtained after immersion in coffee and cranberry juice. Coffee promoted the highest gloss change (worst gloss retention), followed by cranberry juice, Coca-cola and artificial saliva (p<0.05). The type of beverage significantly influenced the gloss of resin composites. Coca-cola reduced gloss of the three resin composites in a similar manner. Coffee affected the ED gloss more than that of Z350 and CD, while cranberry juice affected Z350 more than ED and CD. Saliva had a more pronounced effect on the gloss retention of CD than ED. The beverages used in this study influenced the optical surface properties of the composites studied301525

Effect of combining photoinitiators on cure efficiency of dental resin-based composites

Camphorquinone is the most conventionally used photoinitiator in Dentistry. Although different alternative photoinitiators have been proposed, no photoinitiator was capable of completely substituting camphorquinone. The combination of photoinitiators has been considered the best alternative. Objectives: To evaluate the effect of combining Norrish type I and II photoinitiators on the cure efficiency of dental resin-based composites. Methodology: Experimental composites were produced containing different photoinitiator systems: Norrish type I-only, mono-alkyl phosphine oxide (TPO); Norrish type II-only, camphorquinone (CQ); or its combination, CQ and TPO, in a 1: 1 molar ratio. UV-vis absorption spectrophotometry was performed to assess the consumption of each photoinitiator after curing (n=3). A multi-wave LED (Bluephase® G2, Ivoclar Vivadent) was pre-characterized and used with a radiant exposure of 24 J/cm2. The degree of conversion was evaluated by Raman spectrometry, and the elution of the monomers by nuclear magnetic resonance analysis (n=3). Data were analyzed using ANOVA and Tukey's test (α=0.05; β=0.2). Results: The combination of CQ and TPO increased the consumption of the photoinitiator system compared to CQ-only (p=0.001), but presented similar consumption compared to TPO-only (p=0.52). There was no significant difference in the degree of conversion between the composites regardless of the photoinitiator system (p=0.81). However, the elution of the monomers was reduced when both photoinitiators were combined. TPO-based material presented the highest elution of monomers. Conclusions: The combination of the photoinitiator systems seems to be beneficial for the cure efficiency of dental resin-based composites

Clinical evaluation of the failure rates of metallic brackets

OBJECTIVES: The aim of this study was to evaluate in vivo the bonding of metallic orthodontic brackets with different adhesive systems. MATERIAL AND METHODS: Twenty patients (10.5-15.1 years old) who had sought corrective orthodontic treatment at a University Orthodontic Clinic were evaluated. Brackets were bonded from the right second premolar to the left second premolar in the upper and lower arches using: Orthodontic Concise, conventional Transbond XT, Transbond XT without primer, and Transbond XT associated with Transbond Plus Self-etching Primer (TPSEP). The 4 adhesive systems were used in all patients using a split-mouth design; each adhesive system was used in one quadrant of each dental arch, so that each group of 5 patients received the same bonding sequence. Initial archwires were inserted 1 week after bracket bonding. The number of bracket failures for each adhesive system was quantified over a 6-month period. RESULTS: The number of debonded brackets was: 8- Orthodontic Concise, 2- conventional Transbond XT, 9- Transbond XT without primer, and 1- Transbond XT + TPSEP. By using the Kaplan-Meier methods, statistically significant differences were found between the materials (p=0.0198), and the Logrank test identified these differences. Conventional Transbond XT and Transbond XT + TPSEP adhesive systems were statistically superior to Orthodontic Concise and Transbond XT without primer (p<0.05). There was no statistically significant difference between the dental arches (upper and lower), between the dental arch sides (right and left), and among the quadrants. CONCLUSIONS: The largest number of bracket failures occurred with Orthodontic Concise and Transbond XT without primer systems and few bracket failures occurred with conventional Transbond XT and Transbond XT+TPSEP. More bracket failures were observed in the posterior region compared with the anterior region

Thermocycling effect on chain elastic force degradation / O efeito da termociclagem na degradação de força de elásticos em cadeia

O objetivo deste estudo foi avaliar o efeito da variação da temperatura na degradação das forças da cadeia de elásticos de diferentes marcas. Para compor os grupos experimentais (G), foram confeccionados 100 segmentos de elásticos, sendo 20 de cada marca: G1 - American Orthodontics; G2 - TP Ortodôntica; G3 - 3M Unitek / ESPE; G4 - GAC; e, G5 - Rocky Mountain (RM). Metade dos elásticos (n = 10) foi submetida à termociclagem e a outra metade armazenada em água destilada a 37ºC. Todas as amostras foram submetidas à análise de degradação de força na máquina universal de ensaios Instron, sendo a primeira leitura realizada após a confecção dos corpos-de-prova e repetida após um período de 28 dias. Nesse período, os elásticos permaneceram esticados em placas de acrílico. Os dados foram submetidos a modelos mistos para medidas repetidas e os dados foram submetidos à Análise de Variância 2 fatores e ao teste de Tukey (? = 0,05). O Grupo G2 apresentou resistência média significativamente maior nos tempos inicial e final, com e sem termociclagem. O grupo G1 apresentou média de força significativamente maior em relação aos grupos G3, G4 e G5 no momento inicial (p &lt;0,05). No tempo final, G1 apresentou força significativamente menor que G5 sem pedalar e menor que G4 e G5 com pedalada. Não houve diferença significativa entre os grupos com e sem ciclismo, com diminuição significativa da força em todas as marcas. Ao analisar a degradação da força nos tempos inicial e final, observa-se maior degradação nos grupos submetidos à termociclagem, sendo que G1 apresentou maior degradação da força, enquanto os grupos G4 e G5 apresentaram menor degradação. Conclui-se que a variação da temperatura aumentou a degradação dos elásticos na cadeia para todas as marcas analisadas. Os elásticos da American Orthodontics apresentaram a maior degradação da resistência, enquanto os elásticos GAC e RM apresentaram a menor degradação

Evaluation of the wire flexibility used in the Mandibular Advancement Device submitted to thermal cycling / Avaliação da flexibilidade do fio utilizado no Dispositivo de Avanço Mandibular submetido ao ciclagem térmica

Este estudo teve como objetivo avaliar a flexibilidade de fios utilizados na confecção de molar lock do Mandibular Advancement Device (MAD), submetidos à variação de temperatura. Foram utilizados 64 segmentos de fios ortodônticos (n = 8), assim alocados: G1) Dentauro; G2) Leoni; G3) Leoni (Bio Steel); G4) Morelli; G5) Dentaurum + Termociclagem (TC); G6) Leoni + TC; G7) Leoni (Bio Steel) + TC; G8) Morelli + TC. Os segmentos foram analisados pelo método de flexão em três pontos, com auxílio de Máquina Universal de Ensaios. Os grupos submetidos à termociclagem foram submetidos a um total de 2300 ciclos térmicos (5 ° C e 55 ° C) correspondentes a 8 meses. Após esse período, os corpos-de-prova foram novamente imersos em água destilada a 37 ° C e mantidos em estufa por 24 horas. A partir desse processo de termociclagem, as amostras foram submetidas a um ensaio de flexão em três pontos. Os dados foram submetidos à análise de variância (ANOVA-two-way) seguida do teste de Tukey, considerando o nível de significância de 5%. Não houve diferença significativa na flexibilidade entre os grupos com e sem ciclismo, considerando a mesma marca e mesmo ponto (p = 0,05). Sem pedalar, a marca Dentaurum apresentou maior flexão média no ponto de 0,5mm, e Morelli apresentou maior flexão no ponto de 1,0mm (p &lt;0,05). A marca Leoni apresentou valores maiores em 2 e 3 mm, e maiores que a marca Dentaurum no ponto de 2 mm (p &lt;0,05). Para os grupos submetidos à termociclagem, nos pontos de 0,5 mm, não houve diferença estatística entre os grupos, exceto para o grupo Leoni, obtendo maior resistência à flexão em relação ao fio da marca Dentaurum (p &lt;0,05). Em 1, 2 e 3 mm, o fio da marca Leoni apresentou maior flexibilidade em relação ao Dentaurum e Leoni (Bio Steel) e Morelli (p &lt;0,05). A variação da temperatura não influencia nas propriedades de flexibilidade dos fios utilizados na confecção do MAD, porém, existem diferenças entre as diferentes marcas quando avaliadas nas mesmas condições