Polymerization Shrinkage of Bulk Fill Composites and its Correlation with Bond Strength.

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.

Polymerization shrinkage of bulk fill composites and its correlation with bond strength

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.

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.

Shear bond strength of different surface treatments in bulk fill, microhybrid, and nanoparticle repair resins.

OBJECTIVES: The purpose of this study was to evaluate the influence of surface treatment and different types of composite resin on the microshear bond strength of repairs. MATERIALS AND METHODS: Seventy-two specimens (n=72) were prepared using a nanoparticle resin and stored in artificial saliva at 37 ± 1°C for 24 h. After this period, the specimens (n=24) were restored with microhybrid resin P60 (3M ESPE), nanoparticle resin Filtek Z350 (3M ESPE), and Bulk Fill Surefil SDR Flow (Dentsply) composite resins. Previously, the surfaces of the samples were treated, forming the following subgroups (n=12): (A) conditioned with 37% phosphoric acid for 30 s, and (B) abrasioned with a diamond tip for 3 s and conditioned with 37% phosphoric acid. In all groups, before insertion of the composite resin, the adhesive system Adper Single Bond 2 was actively applied and photopolymerized for 20 s. RESULTS: The microshear test was executed to assess bond strength. Kruskal-Wallis (p<0.05) and Mann-Whitney statistical tests showed significant statistical difference considering that the bulk-fill resin turned out to have a lower bond strength than the conventional nanoparticle and microhybrid composites. With regard to the technique, the roughening with diamond bur followed by the application of phosphoric acid exhibited values higher than the exclusive use of acid. CONCLUSION: The microshear bond strength of the composite resin repairs varies in accordance with the type of composite resin utilized, and roughening the surface increased the bond strength of these materials.

Is there correlation between polymerization shrinkage, gap formation, and void in bulk fill composites? A µCT study

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.

Efeito de agentes dessensibilizantes na resistência de união de um sistema adesivo autocondicionante / Effect of desensitizing agents on shear bond strength of a self-etching adhesive

Uma adesão satisfatória pode ser dificultada na presença de agentes dessensibilizantes, como nas cavidades do tipo Classe V. Este estudo teve como objetivo investigar a influência de dois agentes dessensibilizantes na resistência de união de um sistema adesivo autocondicionante quando aplicados previamente ao sistema adesivo. Foram utilizadas 30 coroas de incisivos bovinos, sendo incluídos em buchas de redução de PVC pré-fabricadas, com auxílio de resina acrílica. A superfície vestibular foi preparada, deixando a dentina exposta e os 30 conjuntos foram divididos em três grupos: G1 (adesivo + resina), G2 (oxagel + adesivo + resina) e G3 (G.H.F + adesivo + resina). Então, cilindros de resina composta (4 mm de diâmetro e 4 mm de altura) foram confeccionados. Decorridas 24 horas, os espécimes foram submetidos ao ensaio de cisalhamento e velocidade do atuador de 0,5 mm/min. Os dados foram submetidos ao teste de análise de variância de um fator (Anova - one way), complementados pelo teste de Tukey. Houve diferença estatística significante entre os tratamentos (G2 - 2,49 < G1 - 11,01 = G3 - 10,1). Assim, conclui-se que a resistência de união do sistema adesivo autocondicionante na dentina pré-tratada com agentes dessensibilizantes é prejudicada pelo uso do produto à base de oxalato.

A satisfactory bonding may be hampered in the presence of desensitizers agents, such as class V cavities. The aim of this study was to compare the effect of two different desensitizers on shear bond strength of a self-etch adhesive system. Thirty crowns of bovine incisors were mounted in pre-fabricated acrylic PVC using acrylic resin. The vestibular surface was prepared exposing the dentin and the crowns were divided into three groups: G1 (adhesive + resin), G2 (oxagel + adhesive + resin), and G3 (GHF + adhesive + resin). Resin composite cylinders (4 mm in diameter and 4 mm in height) were then placed. After 24 hours, shear bond strengths were measured using a circular knife-edge and crosshead speeds of 0.5 mm/minute. One-way ANOVA and Tukey’s tests were used to compare the different conditions for bonding system. There was a statistically significant difference between treatments (G2 – 2.49 < G1 – 11.01 = G3 – 10.1). It was concluded that the shear bond strength of the self-etch adhesive system on dentin pre-treated with desensitizing agents is decreased by the use of the product based on oxalate