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.

Background The implementation of restorative procedures that guarantee success and optimize clinical time is the target of investigations in Restorative Dentistry. This study aimed to analyze the influence of sonic insertion of bulk-fill (BF) and conventional (C) resin composites on the microtensile bond-strength (µ-TBS) and cure depth (CD) of large and deep class I restorations. Material and Methods Fifty-six healthy human premolars were selected and occlusal cavities (4 x 4 x 3 mm; factor C = 5) were prepared. TC - Tetric N-Ceram (BF), SF - SonicFill (BF), and Z350 - Filtek Z350 XT (C) composite resins were used to restore the cavities, using sonic (S) and non-sonic (NS) insertion techniques. A group restored with conventional incremental insertion (I) using Z350 XT resin was performed serving as a control. Teeth were prepared for microtensile bond-strength test (µ-TBS). And also, restoration depths of 1 and 4 mm were measured with an automatic microhardness indenter (50 g -15 s) to determine the CD. Results were evaluated using ANOVA, Scheffe, and Games-Howel posthoc test (α = 0.05). Results Types of resins and insertion techniques present statistical differences for µ-TBS and CD ( p ≤ 0.001). The µ-TBS was higher respectively for the groups SF > TC > Z350; however, the sonic insertion for SF and Z350 (I) did not present significant differences in µ-TBS. Higher microhardness values were observed on the surface (1mm). At a depth of 4 mm Z350 (I)> SF(S)> SF(NS)> TC(S/NS)> Z350(S/NS) ( p < 0.001). Pearson’s Correlation of bond strength and base micro-hardness was significant ( p ≤ 0.001), strong, and positive (0.955). Conclusions The influence of sonic insertion is material dependent, influenced only the microhardness of the SonicFill resin and did not interfere with the bond strength and cure depth of other bulk fill and conventional resin composite. Key words: Composite resins, dentin, hardness tests, tensile strength, Bulk-fill resins, sonic insertion.

ObjectiveThe aim of this study was to evaluate in vitro bond strength of metal brackets bonded with: total etch, total etch with erbium: yttrium aluminum garnet laser (Er:YAG) and self-etching adhesive systems, submitted to thermal-mechanical cycling, simulating 1 year of orthodontic treatment.Materials and methodsFor the study, 80 bovine incisors were randomly divided into 3 experimental groups (n=16 each): XT- acid etching + Transbond XT, XT/Er:YAG- Transbond XT associated with Er:YAG laser irradiation (λ=2.94 μm, 60 mJ, 10 Hz) and SEP- Transbond Plus Self Etching Primer. Samples were submitted to thermal-mechanical cycling, simulating 1 year of orthodontic treatment. Afterward, the shear bond strength test was performed in a universal test machine at a speed of 0.5mm/min. Samples were evaluated under a stereomicroscope and by scanning electron microscopy for analysis of enamel surface and adhesive remnant index. Data were analyzed using Kruskal–Wallis and Mann–Whitney (with Bonferroni correction) statistical tests.ResultsStatistically significant difference was observed between the groups studied (p<0.05). Groups XT and SEP showed the highest bond strength values, without statistical difference between them, while group XT/Er:YAG showed reduction in bond strength values. Higher frequency of adhesive failures between enamel and adhesive system was verified for groups XT and XT/Er:YAG.ConclusionThe conventional (XT) and self-etching (SEP) adhesive systems showed mean bond strength values, similar between them, whereas the previous application of Er:YAG laser promoted the lowest bond strength values.

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Background To evaluate the influence of the association of the universal adhesive system to different energy densities of the Nd:YAG laser on the hydraulic conductance of dentin. Material and Methods Fifty bovine dentin discs were made. The samples were stratified into four groups (n = 10) according to the treatment performed; SBU- Adper Single Bond Universal (3M ESPE), SBU_60 - SBU associated with the Nd:YAG laser (60mJ, 10Hz, 0.6W - 47.77 J / cm²), SBU_80 - SBU associated with the Nd:YAG laser (80mJ, 10Hz, 0.8 W - 63.69 J / cm2) and C – dentin without treatment (smear layer). Hydraulic conductance measurements were taken 24 hours after the treatments (HC1) and after erosive challenge (HC2). Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX) helped to visualize the dentin after the different treatments. Scheffe and Games-Howell statistical tests were used to analyze hydraulic conductance (α = 0.05). Results The treated dentin (SBU, SBU_60, and SBU_80) reduced HC1 when compared to dentin with smear layer (C) ( p < 0.001). The erosive challenge has increased HC2 in SBU_60 and C ( p < 0.001), and did not promote a significant difference in SBU_80 and SBU. The SEM / EDX analyzes showed an irregular and semi-permeable barrier on the surfaces of the treated dentin. Conclusions The association of universal adhesive with Nd:YAG can be an effective alternative for the occlusion of dentinal tubules, whereas higher energy per pulse Nd:YAG (SBU_80) can increase the resistance to permeability when exposed to the erosive challenge. Key words: Dentin, permeability of dentin, Nd:YAG Laser, adhesives.