Resumo O presente estudo teve por objetivo avaliar a contração de polimerização (CP) usando microtomografia computadorizada (µCT) e a resistência de união por microtração (µTBS) em restaurações classe I de compósitos bulk fill (CBF) e convencional, assim como a correlação entre esses fatores. Cavidades classe I (4 x 5 x 4 mm), fator C=4,2, foram feitas em terceiros molares livres de cárie que foram randomizados e divididos em 4 grupos (n = 6): XTI (Filtek Supreme XTE: técnica incremental); XTB (Filtek Supreme XTE: técnica de preenchimento único); TBF (Tetric Bulk Fill); E SF (SonicFill). Cada dente foi escaneado duas vezes em μCT: T0 -após o preenchimento da cavidade com compósito, e T1 - após a cura à luz. Os dados foram analisados subtraindo o volume do compósito para cada tempo (T1 - T0). Após 1 semana, os dentes foram seccionados transversalmente no sentido vestíbulo-palatino e mesio-distal para obter espécimes com aproximadamente 1 mm² de espessura e fixados em uma máquina de ensaio universal para teste de μTBS. Os testes de Kruskal-Wallis e Dunn mostraram diferença estatisticamente significante para a contração em μCT entre XTI e XTB, e entre SF e XTB. Em relação à μTBS, todos os grupos diferiram do XTB. Compósitos do tipo bulk fill apresentam uma CP similar ao compósito convencional nanoparticulado inserido usando a técnica incremental, porém a resistência de união foi maior para o grupo incremental, que apresentou um menor número de falhas pré-teste quando comparado aos CBF. Não foi observada correlação entre a contração de polimerização e a resistência de união nos compósitos estudados.

Abstract The present study aimed to evaluates polymerization shrinkage (PS) using microcomputed tomography (μCT) and microtensile bond strength (μTBS) in bulk fill composites (BFC) and conventional class I restorations as well as the correlation between these factors. Class I cavities (4 x 5 x 4 mm), factor-C = 4.2, were created in third molars that were free of caries, which were randomly divided in 4 groups (n = 6): XTI (Filtek Supreme XTE: incremental technique); XTB (Filtek Supreme XTE: single fill technique); TBF (Tetric Bulk Fill); and SF (SonicFill). Each tooth was scanned twice in μCT: T0 was after filling the cavity with composite, and T1 was after light curing. The data were analyzed by subtracting the composite volume for each time (T1 - T0). After 1 week, the teeth were sectioned crosswise in the buccolingual and mesiodistal directions to obtain specimens with approximately 1 mm² thickness and fixed in a universal testing machine to perform μTBS. The Kruskal-Wallis and Dunn tests showed a statistically significant difference for shrinkage in µCT among the XTI and XTB and between the SF and XTB. Regarding the μTBS, all the groups differed from XTB. Bulk fill composites type presents a PS similar to that of the conventional nanoparticulate composite inserted using the incremental technique, but the bond strength was higher for the incremental group, which presented a lower number of pre-test failures when compared to BFC. No correlation was observed between the polymerization shrinkage and bond strength in the studied composites.

Abstract: This in vitro study aimed to evaluate the volume of polymerization shrinkage (VS), gap (VG), and void (VV) using computerized microtomography (μCT) in bulk fill resin composites and conventional class I restorations, and to establish a correlation between these factors. Class I cavities (4 x 5 x 4 mm), C-factor = 4.2, were performed on caries-free human third molars and randomly divided into five groups (n = 6): FSI (Filtek Supreme XTE incremental insertion); FSS [(Filtek Supreme XTE single insertion(SI)]; TBF [(Tetric Bulk Fill: SI and manual filling (MF)]; SFM (Sonic Fill: SI/MF); and SFS (SonicFill: SI and sonic filling). The teeth were scanned and analyzed by μCT at T0, after filling the cavity with resin, and at T1, after polymerization for VG and VV, and for VS (T1-T0). There was statistically significant difference in VS in μCT for the FSI and FSS groups and between SFS and FSS as well as some difference in VV for FSI and bulk fill resin composites and no difference in VG between the conventional technique and bulk fill composites. Bulk fill resin composites presented similar VS and gap formation to those of incrementally inserted conventional resin composites. There is a moderate and weak positive correlation between polymerization shrinkage and gap formation and void, respectively. The final gap formation was more dependent on the initial gap than on polymerization shrinkage or void volume.

<p>O objetivo deste estudo foi avaliar a influência dos sistemas adesivos simplificados (condicionamento ácido total e auto-condicionante) e fluorfosfato acidulado a 1,23% (FFA) na resistência de união ao microcisalhamento (μ-RUC) de resinas compostas em molares e incisivos decíduos. O esmalte vestibular de quarenta molares e quarenta incisivos decíduos foi tratado com Clearfil SE Bond (CSE, Kuraray) ou Adper Single Bond 2 (SB2, 3M/ESPE). Cada grupo foi subdividido com base no tratamento prévio do esmalte com ou sem aplicação tópica de FFA a 1,23%. Em seguida, matrizes foram posicionadas e preenchidas com resina composta e posterior fotopolimerização. Depois da armazenagem em água destilada a 37±1 °C por 24 h, os espécimes foram submetidos ao μ-RUC em uma máquina de ensaio universal. Teste Kruskal-Wallis e Mann-Whitney (p<0,05) mostraram que a aplicação prévia de FFA a 1,23% levou a uma redução significativa na resistência de união. O tipo de adesivo não exerceu influência significativa na resistência de união. Na análise intergrupos, entretanto, redução significativa na resistência de união foi encontrada para os incisivos quando CSE foi empregado sem FFA. Falha adesiva foi o tipo de fratura mais comum. A resistência de união foi afetada pela aplicação de FFA a 1,23% e tipo de dente.</p>

<p>The aim of this study was evaluate in vitro the influence of simplified adhesive systems (etch-and-rinse and self-etching) and 1.23% acidulated phosphate fluoride (APF) on the microshear bond strength (μ-SBS) of composite resins on primary molars and incisors. Forty primary molars and forty incisors vestibular enamel was treated with either the self-etching Clearfil SE Bond (CSE, Kuraray) or etch-and-rinse Adper Single Bond 2 (SB2, 3M/ESPE) adhesive system. Each group was subdivided based on the prior treatment of the enamel with or without the topical application of 1.23% APF. Thereafter, matrices were positioned and filled with composite resin and light cured. After storage in distilled water at 37±1°C for 24 h, the specimens were submitted to μ-SBS in a universal testing machine. Kruskal-Wallis and Mann-Whitney tests (p<0.05) showed that the prior application of 1.23% APF led to a significant reduction in bond strength. The type of adhesive exerted no significant influence bond strength. In the inter-group analysis, however, significantly bond strength reduction was found for the incisors when CSE was employed with APF. Adhesive failure was the most common type of fracture. The bond strength was affected by the prior application of 1.23% APF and type of tooth.</p>

AIM: To evaluate the influence of varying the water/powder ratio on the compressive strength of type IV mineral and synthetic casts. METHODS: Four commercial brands of type IV mineral and synthetic casts were evaluated: Durone, Herostone, Fuji Rock, and Elite Rock. Ninety-six test samples were prepared from a silicone matrix, according to ADA's standard no. 25. The samples were prepared according to the manufacturer's recommendations with a normal water/powder ratio (n = 12) and with 20% extra water (n = 12), forming the control (A) and experimental (B) subgroups, respectively. Compressive strength tests were performed using a universal testing machine EMIC (DL 2000) with a load cell of 2,000 kgf/cm2. The obtained data were analyzed statistically using two-way ANOVA and Tukey's test (α=5%). RESULTS: The synthetic Elite Rock cast was statistically different from the one obtained when the portion of water indicated by the manufacturer was used; no significant differences were found in the remaining casts when the proportion of water was increased by 20%. CONCLUSIONS: the groups of synthetic and mineral casts differed and the water increase (20%) did not cause significant difference on the compressive strength of the materials.

The aim of this study was to evaluate the shear bond strength (SBS) of polycrystalline ceramic brackets (PCB) bonded after bleaching treatment using different composite resins and enamel etching times. A total of 144 bovine incisors were randomly divided into two study groups (n = 72, each) as follows: G1, enamel bleached with 35% hydrogen peroxide, and G2 (control group), enamel unbleached. After the bleaching treatment, the samples were stored in artificial saliva for 14 days. These groups were further divided into two subgroups (n = 36, each) as follows: GA, brackets bonded with Transbond XT (3M) and GB, brackets bonded with Filtek Z250 (3M). For each resin used, three different etching times with 37% phosphoric acid (15, 30 and 60 seconds) were tested. SBS tests were performed using a universal testing machine (EMIC), and the adhesive remnant index (ARI) score was verified. Significant differences among the three experimental conditions and interactions between the groups were observed. The type of composite resin accounted for 24% of the influence on the bond strength, whereas the etching time and bleaching treatment accounted for 14.5% and 10% of the influence on bond strength, respectively. The ARI revealed that the most common area of adhesion failure was at the composite resin-bracket interface. The type of composite resin, etching time and external bleaching significantly influenced the SBS of PCB on enamel, even after 14 days of saliva storage.

O objetivo deste estudo foi o de avaliar in vitro a resistência adesiva de bráquetes após o pré-tratamento do esmalte com diferentes soluções fluoretadas. Foram utilizados 48 incisivos bovinos hígidos recém-extraídos que foram aleatoriamente divididos em 4 grupos experimentais (n=12). CG (controle): sem tratamento; FN: aplicação de flúor neutro por 4 min; FFA: aplicação de flúor fosfato acidulado (FFA) a 1,23% por 4 min; e VFS: aplicação de verniz de fluoreto de sódio a 5% por 6 h. Após o tratamento dos grupos, foi realizada a profilaxia do esmalte e os bráquetes foram fixados utilizando o compósito Transbond XT (3M), seguindo as especificações do fabricante. A resistência adesiva foi verificada através do teste de cisalhamento, realizado na Máquina de Ensaio Universal DL-2000 24 h após a fixação dos bráquetes. As superfícies dos dentes foram analisadas para verificação do índice de adesivo remanescente (IAR). Por meio dos testes estatísticos ANOVA e Tukey (α=5%), observou-se diferença estatisticamente significante entre os grupos estudados (p<0,0001), sendo que GC e FN, apresentaram valores superiores de resistência adesiva quando comparados aos grupos FFA e VFS, porém GC-NF e FFA-VFS não apresentaram diferenças estatisticas entre si (p>0,05). A análise dos escores do IAR revelou que grande parte das falhas ocorreram na interface esmalte-resina. Conclui-se que o tratamento do esmalte com FFA 1,23% e VFS a 5%, previamente à fixação de bráquetes ortodônticos, reduziu os valores de resistência adesiva ao cisalhamento

The aim of this in vitro study was to evaluate the shear bond strength of brackets after pre-treatment with different fluoride solutions. This study used 48 freshly extracted sound bovine incisors that were randomly assigned to 4 experimental groups (n=12). CG: (control) without treatment; NF: 4 min application of neutral fluoride; APF: application of 1.23% acidulated phosphate fluoride (APF) for 4 min; and SFV: application of 5% sodium fluoride varnish for 6 h. For each group, after surface treatment, prophylaxis of enamel and bracket bonding with Transbond XT composite resin (3M) were performed following the manufacturer's specifications. The shear bond strength was performed with a universal testing machine 24 h after fixing the brackets. The tooth surfaces were analyzed to verify the adhesive remnant index (ARI). Data were analyzed statistically by ANOVA and Tukey's test (α=0.05). There was statistically significant difference among the groups (p<0.0001). CG and NF groups presented significantly higher bond strength than APF and SFV. There was no significant difference between CG and NF or between APF and SFV (p>0.05). The analysis of ARI scores revealed that most failures occurred at the enamel-resin interface. It may be concluded that the pre-treatment of enamel with 1.23% APF and 5% SFV prior to fixing orthodontic brackets reduces shear bond strength values.