Filtek Bulk Fill Research Articles

Bonding performance and mechanical properties of flowable bulk-fill and traditional composites in high c-factor cavity models

Objectives:The aim of this study is to evaluate bond strength (BS), shrinkage stress (SS), flexural strength (FS), and elastic modulus (E) of three flowable bulk fill in comparison with conventional composites.Materials and Methods:Three bulk fill (Filtek Bulk Fill Flow, Surefil SDR, X-tra Base) and three conventional composites (Filtek Z250 XT, Grandioso, Dentsply TPH3) were used. For BS, conical cavities (n = 10) were prepared in bovine dentine and restored with materials and were analyzed through push-out test in a universal testing machine (UTM). For FS/EM, 60 (n = 10) bar specimens (7 mm × 2 mm × 1 mm) were prepared and evaluated with a UTM. SS was measured in UTM coupled to an extensometer (n = 5). The data were statistically evaluated using one-way ANOVA/Tukey tests (P < 0.05).Results:Conventional composites showed higher E when compared to bulk-fill composites. Regarding FS, they showed similar results, except for (XBF) Xtra Bulk Fill that was inferior. SS and BS of bulk-fill composites were significantly lower and higher than conventional composites, respectively, except for XBF, which showed similar BS to conventional ones.Conclusions:Flowable bulk-fill composites, except XBF, showed higher BS, lower SS, similar FS, and lower E when compared to conventional ones.

Evaluation of marginal sealing quality of restorations with low shrinkage composite resins

BackgroundThis study compared the quality of marginal sealing in the gingival wall of class II preparations of two low-shirinkage resins of the bulk fill type with a conventional resin isolated or associated with a glass ionomer cement (GIC). Material and Methods40 human molars were divided into 4 groups and 80 occlusal-mesial and occlusal-distal restorations were performed with the following materials: SureFil SDR flow, Filtek Bulk Fill Posterior, Z250 resins and Riva Light Cure GIC. 40 restorations were evaluated in Scanning Electron Microscopy (SEM) with Elemental Microanalysis Spectrometry (EDS) initially and the remainder after a period of 6 months of aging in a 37 ± 5°C oven. An average of the silver penetration at each restoration was obtained in the two evaluations and the results were statistically analyzed in a descriptive and inferential way, through the paired t-Student and one-way ANOVA F-test. ResultsThere were no significant statistical differences between the materials with respect to silver nanoinfiltration, except for the Bulk Fill Posterior/3M ESPE resin compared to the GIC and conventional resin in the final evaluation. Conclusions The low shrinkage resins showed a similar behavior in relation to the marginal sealing quality observed in the GIC or composite resin with the incremental technique, also presenting the advantage of simplicity in the technique of confection of the restorations and reduction of the time of work. Key words:Resin composites, Bulk fill, dental restorations, marginal quality, adhesion.

Effect of Composite Resin and Restorative Technique on Polymerization Shrinkage Stress, Cuspal Strain and Fracture Load of Weakened Premolars.

To compare shrinkage stress, cuspal strain and fracture load of weakened premolars restored with different conventional and bulk-fill composite resins and restorative techniques. Fifty premolars received a 4.0 x 3.5mm mesio-occlusal-distal (MOD) class II preparation. The lingual and buccal cups were internally weakened. Specimens were restored according to the following 5 groups: Filtek Z350 XT/10 increments; Filtek Z350 XT/8 increments (both 3M Oral Care); Filtek Bulk Fill Flowable Restorative + Filtek Z350 XT (both 3M Oral Care); SDR + Spectra Basic (Dentsply Sirona); and Tetric N-Ceram Bulk Fill (Ivoclar Vivadent). Cuspal strains were measured using strain gauges (n = 10). After restoration, specimens were submitted to thermal/mechanical cycles and fractured. Post-gel shrinkage of the composites was determined. Additionally, residual shrinkage strains and stresses were analyzed using three-dimensional finite element analysis (3D-FEA). The data were statistically analyzed using one-way ANOVA and Tukey's HSD (α = 0.05). One-way ANOVA revealed statistically significant differences among composite resins (p < 0.001) for the post-gel shrinkage. Filtek Z350 XT had the highest post-gel shrinkage and no difference was found between Spectra Basic and Tetric N-Ceram Bulk Fill (p = 0.110). The Filtek Z350 XT/10 increments, Filtek Z350 XT/8 increments and Filtek Bulk Fill Flowable Restorative/Filtek Z350 XT had statistically significantly higher cuspal deformation values when compared to the SDR/Spectra Basic and Tetric N-Ceram Bulk Fill techniques. 3D-FEA confirmed higher stress levels in the incrementally filled conventional restorations. Fracture loads were not statistically significantly different. The bulk-fill restoration techniques resulted in less cuspal strain and stress than the incremental technique with conventional composite resin. Fracture resistance was not affected by the restorative techniques.

Shortening of etching time of the dentin in primary teeth restorations: a randomized clinical trial.

The aim of this study was to investigate the influence of shortening of etching time for dentin on the restoration survival after selective carious tissue removal in primary molars. This two-arm randomized clinical trial included sixty-two subjects (5-8 year-old) and 100 primary molars presenting moderate dentin carious lesions on occlusal surface. The sample was randomly assigned into groups previously to adhesive application (Adper Single Bond 2; 3M ESPE): etching time recommended by manufacturer (15 s) or reduced (7 s). Resin composite (Filtek Bulk Fill Posterior Restorative; 3M ESPE) was inserted in a single increment for all restorations. Restorations were evaluated at 1, 6, 12, and 18 months using FDI criteria. Survival estimates for restorations' longevity were evaluated with Kaplan-Meier method. Multivariate Cox regression analysis with shared frailty was used to assess the factors associated with failures (p < 0.05). The etching time did not influence the restorations' survival (HR 0.35 95%CI 0.11-1.12; p = 0.06). Mean estimated time of survival was 17.6 months (95%CI, 17.2-17.9). The survival rates at the 18-month follow-up were 75.7% and 91.4% (AFR: 16.9% and 5.7%) when primary dentin was acid etched for 15 and 7 s, respectively (log-rank p = 0.06). In conclusion, the etching time for dentin did not influence the clinical behavior of adhesives restorations. However, there was a tendency for better clinical outcome when using etching time of 7 s.

Polymerization depths of conventional and bulk fill composites photoactivated by different methods

The aim of this study was to evaluate the depth of cure of conventional (Filtek Z350 and Esthet-X HD) and bulk fill resins composites (Filtek bulk fill flow and SDR) using different photoactivation methods. Samples were made using five discshaped matrices (1 mm high and 8 mm central diameter) with interposed polyester strips. The samples were photoactivated using different methods [continuous high-irradiance light (LCA), continuous low-irradiance light (LCB), and soft-start (SS)], maintaining 24 J/cm² radiant exposure. After 24h, Knoop microhardness test was performed at 5 depths (surface, 1 mm, 2 mm, 3 mm and 4 mm). The Knoop microhardness were analyzed by ANOVA two-way and Tukey’s test (5%). Conventional resins presented the highest results up to 2 mm depth, except for Esthet-X photoactived by LCB, which showed significant lower Knoop hardness from 2 mm depth. Bulk fill resins photoactivated with LCA and SS had the highest results in 4 mm depth. The LCA and SS photoactivation methods produce suitable photoactivation in conventional composites up to 2 mm and bulk fill up to 4 mm depth and the bulk fill composites present higher polymerization depth than conventional composites. Keywords: Dental curing lights; hardness test; photoactivation; polymerization; resin

Effects of Different Polishing Protocols and Curing Time on Surface Properties of a Bulk-fill Composite Resin.

To determine the effects of different polishing protocols and curing times on the surface roughness (SR), surface gloss (SG) and surface hardness (SH) of a bulk-fill composite resin (BCR). A total of 30 block-shaped specimens (40 mm long × 10 mm wide × 2 mm thick) were made from Filtek Bulk-Fill composite resin and divided into two groups (n = 15) according to curing time (10 and 40 seconds). Each group was subdivided into five groups (n = 3) according to the polishing protocol: laboratory polishing with different silicon paper grits (G1:1200) → (G2:2400) → (G3:4000). Chairside polishing was performed using a series of Sof-Lex spiral (G4) and Jiffy Polisher (G5) points. The SR was measured by a surface profilometer. A Vickers indenter was used to test the SH, and a glossmeter was used to determine the SG at 60 degrees. The SR, SG and SH were quantified before and after polishing. A scanning electron microscopy (SEM) evaluation was then performed. The curing time did not affect the surface properties of the BCR (P > 0.05). Significant differences in SR (ranging from 0.1 to 2 μm) and SG (ranging from 20 to 90 GU [gloss unit]) were found according to the type of polishing protocol (P < 0.05). The SH values following different polishing protocols were significantly higher (ranging from 82 to 95 VH [Vickers hardness]) than the polishing values obtained before the polishing protocols (P < 0.05). The tested chairside polishing protocols presented lower SG and higher SR values than the laboratory polishing protocols.

Curing Depth and Degree of Conversion of Five Bulk-Fill Composite Resins Compared to a Conventional Composite

Background: Limited curing depth and its effect on the degree of conversion are among the challenges of working with light-cure composite resins. The use of bulk-fill composites is one strategy to overcome these limitations. Methods: Ever X Posterior (EXP), Filtek Bulk-Fill Posterior (FBP), Sonic Fill 2 (SF2), Tetric N-Ceram Bulk-Fill (TNB), and X-tra Fil (XF) bulk-fill and Filtek Z250 conventional composite were evaluated in this in vitro experimental study. Six samples for the assessment of microhardness and three samples for the evaluation of DC were fabricated of each composite. After light curing and polishing, the samples were incubated at 37°C for 24 hours. Microhardness was measured by a Vickers hardness tester three times and the mean value was calculated. DC of the top and bottom surfaces was determined using Fourier-Transform Infrared Spectroscopy (FTIR). Data were analyzed using one-way ANOVA and Tukey’s test. Results: Microhardness and DC were significantly different among the groups (P&lt;0.001). XF and Z250 equally showed the highest bottom-to-top surface microhardness ratio (0.97 ± 0.01) and significantly higher DC in the top (P&lt;0.001) and bottom (P&lt;0.005) surfaces compared to other groups. TNB showed the lowest microhardness ratio (0.88 ± 0.04) and DC (68.66 ± 1.52 and 61.00 ± 2.00); the difference in DC of the bottom surface was statistically significant (P&lt;0.003). Conclusion: It appears that bulk-fill composites evaluated in this study are adequately polymerized at 4 mm depth. Their DC was optimal and within the range of conventional composites.

Which materials would account for a better mechanical behavior for direct endocrown restorations?

PurposeTo investigate the mechanical performance and fracture behavior of endocrown restorations prepared using different composite materials and following a direct technique. Methods: Sound molars were cut at 2 mm above the cementoenamel junction, endodontically treated, and allocated according to the type of restoration (n = 7): without post (endocrowns) or with post (post-retained restorations). Endocrowns were fabricated with conventional composite (Filtek Z350); bulk fill composite (Filtek Bulk Fill); conventional composite modeled using resin adhesives (SBMP: Scotchbond Multipurpose Adhesive; or SBU: Scotchbond Universal Adhesive); and lithium disilicate ceramic (E.max; Positive control). The post-retained restorations were fabricated with glass-fiber post combined with conventional or bulk fill composites. All restorations were bonded following an etch-and-rise adhesive approach or self-adhesive resin cement. The teeth were submitted to fatigue (Byocycle) and compression (EMIC DL500) testing at a crosshead speed of 1 mm/min. Data were analyzed with ANOVA and Tukey (p < 0.05) and Weibull analysis was carried out in order to evaluate the reliability of restorations. Results: The bulk-fill-based endocrown showed a stronger performance than the control. The presence of SBMP or the use of bulk-fill composite resulted in the occurrence of less aggressive fractures than the other restorative systems. Endocrowns bonded directly to the tooth seemed to produce similar fracture strength properties as compared to endocrowns bonded using self-adhesive resin cementation. The bulk-fill-based endocrown showed the greatest reliability of study. Conclusion: Resin-based restorative materials seem to be interesting alternative options to fabricate large dental restorations in lieu of the more traditionally used glass ceramics or root canal post systems.

Influence of Bulk-Fill Composites, Polimerization Modes, and Remaining Dentin Thickness on Intrapulpal Temperature Rise

Objectives The aim of this study was to compare the effects of different bulk-fill resin composites, polimerization modes, and the thickness of remaining dentin on the increase of intrapulpal temperature. Methods Human-extracted upper premolar teeth (n = 10) were used to design a single-tooth model with remaining dentin thicknesses of 1 mm and 0.5 mm. Estelite Bulk-fill Flow (Tokuyama, Japan), Surefil SDR™ Flow (Dentsply Caulk, Brazil), Filtek Bulk-Fill Posterior (3M, USA), and SonicFill™ 2 Bulk-fill (Kerr, USA) composites were applied according to the manufacturer's instructions. The standard and high modes of a light emitted diode (LED) light curing unit (LCU) (VALO™ Utradent, USA), were used for polymerization. In order to mimic the in vivo conditions of pulpal circulation, digital flowmetry (SK-600II, SK Medical, China) was used. Intrapulpal temperature rise was measured using K type thermocoupling (CEM DT 610B, Robosem Engineering, China). Data were analyzed using three-way variance analysis (ANOVA) and the independent t-test. Results No significant statistical differences in intrapulpal temperature rise between low viscosity bulk-fill composites (SDR and Estelite) were found. The lowest intrapulpal temperature rise was found in groups which used the Filtek Bulk-fill composite. Decreases in the remaining dentin thickness increased the intrapulpal temperature rise. Significance This study demonstrated that remaining dentin thickness, filler ratio of bulk-fill composites, and power and application time of the LED-LCU may affect intrapulpal temperature rise.

Impact of additional polishing method on physical, micromorphological, and microtopographical properties of conventional composites and bulk fill.

The objective of this study was to evaluate the surface roughness (SR), contact angle (CA), depth distribution of the charge particles (DDCP), mapping of chemical elements, 3D microtopography (3DM), and the micromorphology of the composites (MOR) of conventional and bulk fill after additional polishing. The specimens were prepared from Filtek Bulk Fill (FBF), Tetric N-Ceram Bulk Fill (TNCBF), Opus Bulk Fill (OBF), X-tra Fil (XTFL), Filtek Z250 XT (XT), Grandioso (GRA), Tetric N-Ceram (TNC), Vittra APS (VT), according to three additional techniques (n = 10): without finishing and polishing, finishing and polishing with abrasive rubbers (Astropol), finishing and polishing with Astropol plus additional polishing with silicon carbide brush. The SR and CA were measured using a profilometer and adapted goniometer, respectively; 3DM used atomic force microscopy (AFM); the micromorphology and DDCP by scanning electron microscopy (SEM) and the MOR by means of X-ray dispersive energy spectroscopy (EDS). The SR and CA were analyzed by ANOVA-two factors and Tukey test (p < .05); the others data were analyzed descriptively. The DDCP of all the resins had an organic matrix rich surface layer and a particulate rich subsurface layer of smaller dimensions. Additional polishing: reduced SR of FBF, VT, TNCBF, and XTFL resins; increased the CA value of the XTFL and decreased of XT. In the analyzes for 3DM, smoother and more uniform surfaces were observed in all a resins. The elements: carbon (predominant), oxygen, silicon, zirconia, and aluminum were present in all composite resins. Therefore, additional polishing improved the surface properties of the resins studied.

Depth-dependence of Degree of Conversion and Microhardness for Dual-cure and Light-cure Composites.

New dual-cure bulk-fill composites show promise for uniform degree of conversion and microhardness throughout the entire depth of direct restorations.

Clinical Evaluation of Noncarious Cervical Lesions of Different Extensions Restored With Bulk-fill or Conventional Resin Composite: Preliminary Results of a Randomized Clinical Trial.

This randomized clinical trial evaluated the influence of the occlusogingival distance (OGD) of noncarious cervical lesions (NCCLs) on the clinical performance of a regular bulk-fill resin composite and a regular nanofilled resin composite. A total of 140 restorations were randomly placed in 77 participants by one operator. NCCLs were divided into four groups (n=35) according to OGD (1.5 mm±10% or 3 mm±10%) and resin composites (Filtek Bulk Fill Posterior [B] or Filtek Z350 XT [C]) used: 1.5 mm-B, 1.5 mm-C, 3 mm-B, and 3 mm-C. A two-step self-etch adhesive (Clearfil SE Bond) was applied following manufacturer instructions in all restorative procedures. Restorations were polished 1 week after placement. Clinical evaluation was performed at baseline (7 days), 6 months, and 1 year by two calibrated examiners, according to the modified US Public Health Service criteria evaluating fractures/retention, marginal staining, marginal adaptation, recurrence of caries, anatomic form, postoperative sensitivity, and surface texture. The Kruskal-Wallis test was used for intergroup comparison in each follow-up; the Friedman analysis of variance, followed by the least significant difference test (multiple comparisons) was used for intragroup comparison between baseline and follow-up times (α=0.05). Two restorations were lost at 12 months (1 for 1.5 mm-B and 1 for 3 mm-B). The retention rates at 12 months were 100% for 1.5 mm-C, 97% for 1.5 mm-B, 100% for 3 mm-C; and 97% for 3 mm-B, with no statistical difference among the groups (p=0.570). At 12 months, a statistically significant difference was found among the follow-up times for the same group (1.5 mm-B, 1.5 mm-C, and 3 mm-B) regarding the marginal staining criterion; moreover, the 3 mm-C group showed a significant difference from 6 months. No significant difference was found for the other parameters. Both resin composites showed acceptable clinical performance, and the OGD of NCCLs did not influence the clinical performance of resin composite restorations after 12 months.

Effect of pH Cycling Followed by Simulated Toothbrushing on the Surface Roughness and Bacterial Adhesion of Bulk-fill Composite Resins.

The aim was to evaluate, in vitro, quantitatively and qualitatively, the effect of pH cycling and simulated toothbrushing on surface roughness (Ra) and bacterial adhesion (Cn) of bulk-fill composite resins. Thirty specimens of each composite resin, 5 mm wide and 4 mm high, were obtained: group 1 (control): Filtek Z250 (Z250); group 2: Filtek Bulk-Fill (FTK); group 3: Tetric N-Ceram Bulk-Fill (TTC); and group 4: Aura Bulk-Fill (AUR). After 24 hours, the specimens were polished and then alternated with demineralization/remineralization solutions for 15 cycles of 24 hours each at 37°C. Then the specimens were submitted to simulated toothbrushing. The Ra and Cn measurements were quantitatively analyzed in three stages: after polishing (Ra0 and Cn0), after pH cycling (Ra1 and Cn1), and after simulated toothbrushing (Ra2 and Cn2). The Ra values were submitted to two-way analysis of variance, followed by the Tukey test (α=0.05). The Kruskal-Wallis test, followed by multiple comparisons, was applied for Cn analysis. Surface topography and bacterial adhesion were observed by scanning electron microscopy (SEM). Z250, FTK, and TTC showed no significant change in Ra regardless of the treatment performed; AUR obtained increased Ra at Ra2 (p<0.05). FTK differed from the others at Cn0 and Cn1 (p<0.05). At Cn2, there was no difference among the composite resins. SEM images showed the exposure of fillers and microcavities at Ra1 and Ra2. There was greater bacterial adhesion at Cn1 for Z250 and FTK. It was concluded that the pH cycling caused surface degradation of all composite resins, which was potentiated by simulated toothbrushing. However, only AUR presented an increased Ra. Bacterial adhesion occurred on all composite resins after pH cycling; however, after simulated toothbrushing, adhesion of dispersed bacteria was similar for all the composite resin groups.

Fracture Resistance and Marginal Adaptation of Capped and Uncapped Bulk-fill Resin-based Materials.

This study tested the fracture resistance of capped and uncapped bulk-fill composite restorations and compared them to a conventional composite. Also, the effect of different radiant exposure was investigated. Flowable and high-viscosity bulk-fill composites (SureFil SDR, Filtek Bulk-Fill Posterior, and Tetric N-Ceram Bulk-Fill) and a nanohybrid resin composite (Filtek Z350 XT) were used. Standardized class II cavities were prepared on extracted premolars, and different restoration protocols were used. In protocol 1 (control), restoration was applied using a layering technique; in protocol 2, restoration was applied in bulk with a capping layer; in protocol 3, restoration was applied in bulk without a capping layer; and in protocol 4, restoration was applied in bulk without a capping layer, and the light curing time was extended. After thermocycling, the restorations were examined for marginal gaps and then subjected to the fracture resistance test using a universal testing machine. Statistical analysis was carried out using two-way analysis of variance (ANOVA) followed by one-way ANOVA at a significance level of α = 0.05. A statistically significant difference in the fracture resistance of the tested materials and protocols was detected. Filtek Bulk-Fill Posterior achieved the highest fracture resistance values regardless of the protocol used, and its results were comparable to those of Filtek Z350. SDR and Tetric N-Ceram Bulk-Fill achieved their highest strengths when a capping layer was added. Tetric N-Ceram Bulk-Fill showed improvement in fracture resistance with extended light curing, while SDR and Tetric N-Ceram Bulk-Fill achieved similar results with the addition of a capping layer. The uncapped bulk-fill group showed more gap-free margins than the capped group. The new high-viscosity bulk-fill composite restorations seem to have adequate fracture resistance. However, the results are material dependent, and some materials perform better with a capping layer and extended light curing.

Effects of Finishing and Polishing Methods on the Surface Roughness and Surface Free Energy of Bulk-fill Resin Composites.

The purpose of this study was to determine the influence of finishing and polishing methods on surface properties of bulk-fill resin composites through surface roughness (Ra) and surface free energy (SFE) measurements, and scanning electron microscopy (SEM) observations. Three bulk-fill resin composites, Tetric EvoCeram Bulk Fill (TB), Filtek Bulk Fill (FB), and Filtek Bulk Fill Flowable Restorative (FF), and two conventional resin composites, Clearfil AP-X (AP) and Estelite ∑ Quick (EQ) were used. Seventy cured specimens of each resin composite were prepared and divided into seven groups of 10 specimens. Ra, SFE measurements, and SEM observations were conducted after finishing and polishing procedures. Three groups of specimens were finished with a fine grit diamond bur (FDB), and three with a tungsten carbide bur (CBB). After finishing, one group from each type of finishing was polished with aluminum oxide flexible disks (SSD) and one group from each type of finishing was polished with diamond particles embedded in a silicone point (CMP). A baseline group of samples that were neither finished nor polished after removing the translucent strips from the surface was examined. Although the baseline group showed significantly lower Ra values than the other groups, most resin composites showed lower Ra values with CBB+SSD than with the other finishing and polishing groups. Among the tested resin composites, EQ showed significantly lower Ra values than the other resin composites, regardless of the finishing and polishing methods. On the other hand, AP showed significantly higher Ra values than the other resin composites in all finishing and polishing groups, apart from FB with FDB. For the finished specimens, most resin composites showed higher SFE values with CBB than with FDB. For the polished specimens, all the tested resin composites with CMP showed lower γS values than those with SSD, regardless of the finishing method. The baseline groups of TB and FB showed significantly lower SFE values than the other finished and polished groups. In the SEM observations, all the examined resin composites showed rougher surfaces after finishing with FDB than with CBB. However, when comparing the different polishing methods (CMP and SSD), surface smoothness appeared to be material dependent.

A Two-year Clinical Comparison of Three Different Restorative Materials in Class II Cavities.

The aim of this clinical study was to evaluate the clinical performance of Class II restorations of a high-viscosity glass ionomer material, of a bulk-fill composite resin, and of a microhybrid composite resin. One hundred nine Class II restorations were performed in 54 patients using three different restorative materials: Charisma Smart Composite (CSC; a conventional composite resin), Filtek Bulk Fill Posterior Restorative (FBF; a high-viscosity bulk-fill composite), and Equia Forte Fil (EF; a high-viscosity glass ionomer). Single Bond Universal adhesive (3M ESPE, Neuss, Germany) was used for both conventional and bulk-fill composite resin restorations. The restorations were evaluated using modified US Public Health Service criteria in terms of retention, color match, marginal discoloration, anatomic form, contact point, marginal adaptation, secondary caries, postoperative sensitivity, and surface texture. The data were analyzed using the chi-square, Fisher, and McNemar tests. Eighty-four restorations were evaluated at two-year recalls. There were clinically acceptable changes in composite resin restorations (FBF and CSC). In addition, no statistically significant difference was observed between the clinical performances of these materials in terms of all criteria (p>0.05). However, there was a statistically significant difference between the EF group and the FBF and CSC groups in all parameters except for marginal discoloration, secondary caries, and postoperative sensitivity (p<0.05). The tested bulk-fill and conventional composite resins showed acceptable clinical performance in Class II cavities. However, if EF is to be used for Class II restoration, its use should be carefully considered.

The effects of intrinsic and extrinsic acids on nanofilled and bulk fill resin composites: Roughness, surface hardness, and scanning electron microscopy analysis.

The objective of this study was to examine the effects of extrinsic or intrinsic acids on nanofilled and bulk fill resin materials in vitro. A total of 90 disks were prepared using dental restorative material (Filtek Z350XT, GrandioSO, Filtek Bulk Fill, X-tra fil). Thirty disks of each material were sub-divided into three groups (n = 10) that were immersed for 7 days in deionized water (DW), 5% citric acid (CA-pH 2.1), or 0.1% hydrochloric acid (HCl-pH = 1.2). Surface hardness and roughness (stylus profilometer by Ra parameter) analysis were performed before and after immersion. Morphological changes were evaluated by scanning electron microscopy. The data were analyzed by two-way ANOVA and Tukey's test (α = 0.05). All tested materials did not show significant differences in the effects of the DW, CA, or HCl solutions on surface roughness (p = .368). Likewise, the hardness loss was not affected by the solutions tested (p = .646), but there was a difference in the resin type (p = .002). Filtek Bulk Fill resin hardness was less affected, while Filtek Z350XT and GrandioSO presented the most hardness loss after 7 days of solution immersion. In terms of this experimental study, the results demonstrate the effectiveness of the mechanical properties (roughness and hardness surface) of nanofilled and bulk fill resin materials to resist erosion from extrinsic and intrinsic acids, therefore being potential candidates for dental applications.

Influence of Modulated Photo-Activation on Shrinkage Stress and Degree of Conversion of Bulk-Fill Composites.

This study aimed to evaluate the polymerization properties of bulk-fill materials (low and high-viscosity) by using high-intensity continuous light and intermittent photo-activation in terms of polymerization shrinkage stress and degree of conversion (DC). The following Bulk-fill and Conventional nanofilled resin composites were evaluated: Filtek Z350XT Flow (3M/ESPE), SureFil SDR Flow (Dentsply), Filtek Bulk Fill Flow (3M/ESPE), Filtek Z350XT (3M/ESPE) and Filtek Bulk Fill Posterior (3M/ESPE). A LED device (DB 685, Dabi Atlante) was used for both protocols: continuous uniform and intermittent photo-activation (light-on and light-off cycles) with identical radiant exposure (14 J/cm2). The polymerization shrinkage stress (n=6) was evaluated by inserting a single increment of 12 mm3 between two stainless steel plates (6×2 mm) adapted to a Universal Testing Machine (UTM), at different times. Measurements were recorded after photo-activation. The degree of conversion was evaluated by Fourier transformed infrared spectroscope (FTIR) with an attenuated total reflectance (ATR) accessory (n=5). Data were analyzed by three-way ANOVA and Tukey's HSD (α=0.05) tests. Bulk Fill Posterior presented higher shrinkage stress values when photo-activated with the intermittent technique (p<0.05). The intermittent photo-activation increased the degree of conversion for the low-viscosity bulk-fills (p<0.05). Therefore, the use of modulated photo-activation (intermittent) must be indicated with caution since its use can influence the shrinkage stress and degree of conversion of composites, which varies according to the resin formulations.

Validation of a method of quantifying 3D leakage in dental restorations

Statement of problemA reliable and validated protocol for nondestructive analysis of the entire restorative interface that could be applicable in studies assessing the adaptation of direct and indirect restorations is lacking. PurposeThe purpose of this in vitro study was to validate a 3D protocol for microleakage assessment in class II mesio-occluso-distal (MOD) cavities restored with composite resin. Material and methodsSixteen human third molars received standardized class II MOD preparations with cervical margins located 1 mm apical to the cemento-enamel junction. The specimens were restored with Filtek Bulk Fill Posterior (FBP) or Filtek Bulk Fill Flowable (FBF) and submitted to 10 000 thermocycles (5 °C and 55 °C with a 30-second dwell time at each temperature and 5-second transfer time). The specimens were scanned with microcomputed tomography (μCT) before and after immersion in 50% ammoniacal silver nitrate solution for 12 hours. Scanned data were processed, and the 3D amount of infiltrated silver nitrate was analyzed through the entire adhesive interface. In addition, the linear distance of silver nitrate infiltration was assessed using 3 axial images obtained from each specimen proximal box (2D analysis). Data were tested for homogeneity by using the Shapiro-Wilk test and evaluated by using 1-way ANOVA, followed by the post hoc Tukey HSD test (α=.05). ResultsFBP showed significantly lower leakage than FBF for both 2D and 3D analyses. A low correlation was observed between the assessment methods. ConclusionsThree-dimensional analysis of microleakage using μCT is a predictable and more reliable method for nondestructive and comprehensive analysis of the entire specimen.

Effect of thermocycling on the amount of monomer released from bulk fill composite resins.

The goal of this study was to examine the effect of thermal cycling on the amount of monomer released from bulk fill composites. Five bulk fill composite resins were used in the study. Extraction solutions were obtained at the end of the time/thermal cycle periods: 0-1 day/0-1,500, 1-3 days/1,500-4,500 and 3-7 days/4,500-10,000. The monomers in the extractions samples taken at each time point were measured on an HPLC instrument. The obtained data were analyzed by repeated measures of variance analysis and tukey multiple comparison tests (p<0.05). The thermocycling increased the amount of monomer released from all composites at 0-1 day (p<0.05). At 0-1 and 1-3 days, Venus Bulk Fill and Filtek Bulk Fill composite resins were more affected. Polymer networks with high molecular weight monomers such as Bis-GMA and UDMA can be less affected by thermal changes compared to polymers with low molecular weight monomers.