Flowable Resin Research Articles

Effect of fluoride-releasing restorative materials on bacteria-induced pH fall at the bacteria–material interface: An in vitro model study

ObjectivesInhibition of bacterial acid production by dental restorative materials is one of the strategies for secondary caries prevention. This study aimed to evaluate the effect of fluoride-releasing restorative materials on bacteria-induced pH fall at the bacteria–material interface. MethodsFour fluoride-releasing restorative materials, glass-ionomer cement (GIC), resin-modified glass-ionomer cement (RMGIC), resin composite (RC) and flowable resin composite (FRC) were used. Each specimen was immersed in potassium phosphate buffer at pH 7.0 for 10min and 4 weeks, and in potassium acetate buffer at pH 5.5 for 4 weeks. An experimental apparatus was made of polymethyl methacrylate and had a well with restorative materials or polymethyl methacrylate (control) at the bottom. The well was packed with cells of Streptococcus mutans, and the pH at the interface between cells and materials was monitored using a miniature pH electrode after the addition of 1% glucose for 90min, and the fluoride released into the well was quantified using a fluoride ion electrode. ResultsThe pH of GIC (4.98–5.18), RMGIC (4.77–4.99), RC (4.62–4.75) and FRC (4.54–4.84) at 90min were higher than that of control (4.31–4.49). The fluoride amounts released from GIC were the highest, followed by RMGIC, RC and FRC, irrespective of immersion conditions. Saliva coating on materials had no significant effect. ConclusionsThe fluoride-releasing restorative materials inhibited pH fall at the bacteria–material interface. The degree of inhibition of pH fall seemed to correspond to the amount of fluoride detected, suggesting that the inhibition was due to the fluoride released from these materials. Clinical significanceA little amount of fluoride actually released from the fluoride-releasing materials may have caries preventive potential for oral bacteria.

Measurement of the Internal Adaptation of Resin Composites Using Micro-CT and Its Correlation With Polymerization Shrinkage

In the present study, the internal adaptation of dentin-composite interfaces with various resin composite materials under conditions of thermomechanical loading was analyzed nondestructively using micro-computed tomography (micro-CT), and these results were compared with analyses of microgaps after sectioning. Additionally, the correlation of internal adaptation with polymerization shrinkage strain and stress was evaluated. Four nonflowable resins, Gradia Direct (GD), Filtek P90 (P9), Filtek Z350 (Z3), and Charisma (CH), and two flowable resins, SDR (SD) and Tetric N-Flow (TF) were used. First, the polymerization shrinkage strain and stress were measured. Then, Class I cavities were prepared in 48 premolars. They were divided randomly into six groups, and the cavities were filled with composites using XP bond. To evaluate the internal adaptation, tooth specimens were immersed in a 25% silver nitrate solution, and micro-CT analysis was performed before and after thermomechanical loading. The silver nitrate penetration (%SP) was measured. After buccolingual sectioning and rhodamine penetration of the specimen, the rhodamine penetration (%RP) was measured using a stereo-microscope. One-way analysis of variance was then used to compare the polymerization shrinkage strain, stress, %SP, and %RP among the groups at a 95% confidence level. A paired t-test was used to compare the %SP before and after thermomechanical loading. Pearson correlation analysis was used to compare the correlation between polymerization shrinkage strain/stress and %SP or %RP to a 95% confidence level. Evaluation of the polymerization shrinkage strain demonstrated that P9 < Z3 ≤ GD < CH ≤ SD < TF (p<0.05); similarly, evaluation of the polymerization shrinkage stress showed that P9 ≤ GD ≤ Z3 ≤ CH ≤ SD < TF (p<0.05). The %SP showed that P9 ≤ GD ≤ Z3 < CH ≤ SD < TF (p<0.05) before loading and that P9 ≤ GD ≤ Z3 ≤ CH ≤ SD < TF (p<0.05) after loading. There was a significant difference between the before-loading and after-loading measurements in all groups (p<0.05). Additionally, there was a positive correlation between the %SP and the %RP (r=0.810, p<0.001). Conclusively, the polymerization shrinkage stress and strain were found to be closely related to the internal adaptation of the resin composite restorations. The newly proposed model for the evaluation of internal adaptation using micro-CT and silver nitrate may provide a new measurement for evaluating the internal adaptation of restorations in a nondestructive way.

Repairing ditched amalgam restorations is less time and tooth structure-consuming than replacement

To evaluate the dental structure loss associated with procedures of replacement or maintenance for ditched amalgam restorations in primary molars and the time required to perform each treatment. Ditched amalgam restorations (n=40) were submitted to four different strategies: polishing group-polishing and finishing of restorations; amalgam group-replacement of ditched amalgam restorations with new amalgam restorations; resin group-replacement of amalgam restorations with resin composite restorations; flowable resin group-filling the ditch with a flowable resin composite. The teeth were analysed with a stereomicroscope and the areas pre- and post-treatment were determined by image analysis software to evaluate structural loss. The time required to perform each treatment was recorded in seconds. Student's t test was used to compare areas pre- and post-treatments. ANOVA and Student-Newman-Keuls tests (p<0.05) were used to compare differences among groups and the time to perform each procedure. Dental structure loss was observed in resin and amalgam groups. Replacing the restorations with amalgam took more time, while polishing and applying flowable resin composite consumed less than half of the time compared with amalgam and resin groups. Maintenance of ditched amalgam restorations by polishing and sealing preserves dental structure and involves less time compared with that for replacement of restorations.

Bond strength of dentin submitted to bleaching and restored with different materials

The use of adhesive composite resin with fluoride and with greater fluidity can be favorable to the restoration of the palatal/lingual face of teeth submitted to internal bleaching. Objective:This study evaluated the bond strength of adhesive systems and composite resins to bleached dentin. Material and methods: Forty maxillary canines were sectioned to obtain 40 blocks (5 x 5 mm) of intracoronary dentin. The fragments were included and bleached with 37% carbamide peroxide. After 7 days, the specimens were divided into two groups according to the adhesive system: with (Optibond Solo Plus) and without (Single Bond) fluoride and subdivided into 2 subgroups (n = 10) according to the composite resin: microhybrid (Z250) and flowable (Z350). The restoration was carried out through a bipartite matrix. After 24 hours, the specimens were subjected to shear bond strength test. The data (MPa) were analyzed by ANOVA and Tukey test (α = 0.05). Results: The best results (p &lt; 0.05) were obtained for fluoridated adhesive (7.44 ± 2.35) compared with that without fluoride (5.36 ± 2.01); flowable resin (7.76 ± 2.23) performed better than microhybrid resin (5.03 ± 1.72). When the two variables were associated, the highest results were obtained for the specimens restored with fluoridated adhesive and flowable resin(9.04 ± 1.92). Lower results were observed for non-fluoridated adhesive + microhybrid resin – control (4.24 ± 1.59), without statistically significant differences when compared with the fluoridated adhesive + microhybrid resin (5.83 ± 1.52). Conclusion: The combination with fluoridated adhesive and flowable resin increases the shear bond strength of bleached dentin.

Evaluation of bond strength between glass fiber and resin composite using different protocols for dental splinting

Abstract Context: Many different polymeric materials to chair-side application on pre-impregnated glass fibers (PGF) are available and different protocols are used in clinical procedure. Aims: This study evaluated protocols used for dental splinting on adhesion between PGF and resin. Settings and Design: 42 pair of nano composite resin blocks with (6 × 6 × 8) mm 3 were assigned into seven groups (n=6) and bonded according to the protocol: Gar) adhesive, resin; Ggr) glass fiber, resin; Ggar) glass fiber, adhesive, resin; Gfgar) flowable resin, glass fiber, adhesive, resin; Ggafr) glass fiber, adhesive, flowable resin, resin; Ggfar) glass fiber, flowable resin, adhesive, resin; Gfgr) flowable resin, glass fiber, resin. Materials and Methods: Micro sticks obtained from each group were submitted to the micro tensile bond strength test. Statistical Analysis: The data were statistically evaluated using ANOVA and Tukey`s test (5%). Results: The protocol had a significant effect on the bond strength results (P=0.00). Gar and Ggar resulted in the highest bond strength with no statistical difference. Conclusions: The use of adhesive agent showed to be efficient to promote initial adhesion between fiber and nano composite resin.

Improvement of the Molar Tube Bond Durability with Preheated Orthodontic Adhesive

This study aimed to evaluate the effect of preheated orthodontic adhesives and thermal cycling on the bond strength of molar tubes. One hundred sixty molar tubes were bonded to acid-etched bovine incisors using a conventional orthodontic adhesive (Transbond XT), two microhybrid (Wave and Permaflo), and a nanofilled (Filtek Z350) flowable composite resins, at room temperature or preheated at 60°C. Transbond XT primer and Single Bond 2 adhesive system were used in association with Transbond XT and the flowable composites, respectively. The specimens were stored in water (37°C) for 24 h, and half of the sample was subjected to thermal cycling for 6000 cycles. Ashear bond strength (SBS) test was performed, followed by the appraisal of the adhesive Remnant Index (ARI). Three-way analysis of variance (ANOVA) and the Tukey test were performed at a significance level of 95% (P < .05). Samples bonded with preheated adhesives showed higher SBS regardless of the aging method. Only samples bonded with preheated conventional orthodontic adhesive maintained their bond strength after thermal cycling for 6000 cycles. Preheating orthodontic adhesives improved the bond strength of molar tubes, but only the preheated conventional orthodontic adhesive was capable of maintaining bond strength after thermal cycling.

A model of the viscoelastic behavior of flowable resin composites prior to setting

ObjectiveThe aim of this study is to develop fractional derivative models for the assessment of viscoelastic properties related to handling characteristics of dental resin composites belonging to two classes: flowable (Revolution Formula 2 and Filtek Ultimate) and posterior “bulk-fill” flowable base (Smart Dentin Replace). MethodsRheological measurements on all materials tested in this study were performed using dynamic oscillatory rheometer at temperature of 23°C. A parallel plates module with a diameter of 20mm was used to measure the properties of the resin composites tested. We developed two models to describe the obtained data: the generalized Newton model and the generalized Zener model (the so-called three parameter model). Both models contain fractional derivatives of Riemann–Liouville type. By determining the parameters of the model we were able to fit experimental data with high accuracy. ResultsOur results show that flowable “bulk-fill” resin-composite material (SDR) has distinct properties as compared to other two flowable resin composite materials (Revolution Formula 2 and Filtek Ultimate). Thus, previously found SDR properties as “bulk-fill” flowable base results in the fact that it is described by generalized Zener model (i.e., it has properties of solid like viscoelastic material). SignificanceOur model may be used to predict behavior of tested composites in different flow conditions. The SDR has initially small almost constant complex viscosity showing that it has good self-leveling property.

Nondestructive assessment of current one-step self-etch dental adhesives using optical coherence tomography

ABSTRACT. This study aimed to nondestructively evaluate sealing performance of eight one-step self-etch adhesives (1-SEAs) using optical coherence tomography (OCT). The two-step self-etch adhesive (2-SEA) served as the control. Round tapered class-I cavities (D=4 mm, H=2 mm) were prepared in bovine incisors, treated with each adhesive (n=5), and restored with a flowable resin composite. Cross-sections were obtained from each restoration using swept-source OCT with 1310-nm laser. The average percentage of the sealed interface (SI%) for each adhesive was calculated using image analysis software, considering increased signal intensity at the interface as gap. Samples were then sectioned and observed under confocal laser scanning microscope (CLSM). Significantly different SI% values were found among different adhesives (analysis of variance, Bonferroni, p<0.05). There was also a significant correlation in SI% between OCT and CLSM (p<0.0001, r=0.96). Additionally, microscopic analysis revealed that the gaps in 1-SEAs occurred not only at dentine-adhesive interfaces but also frequently at adhesive-composite interfaces. Some recent 1-SEAs could achieve reliable short-term sealing comparable to 2-SEA. OCT is a unique tool to nondestructively evaluate the sealing performance of the restoratives through the cavity, provided that cavity walls have a certain minimum inclination with respect to the beam.

Degree of conversion of bulk-fill compared to conventional resin-composites at two time intervals

ObjectiveThe purpose of this study was to assess the degree of conversion (DC) over time, using FTIR spectroscopy for bulk-fill flowable resin composite materials compared to conventional flowable and regular resin composite materials. MethodsEight resin composites were investigated including flowable bulk-fill materials SureFil SDR (SDR), Venus bulk-fill (VBF), x-tra base (XB), and Filtek Bulk Fill (FBF). Conventional flowable and regular composite materials included: Venus Diamond flow (VDF), Grandioso flow (GRF), Venus Diamond (VD), and Grandioso (GR). Degree of conversion (DC) was assessed by Fourier transform infrared spectroscopy using attenuated total reflectance technique. DC was measured for samples immediately post-cure (n=3), and after 24h storage period at 37°C (n=3). Results were analysed using one-way analysis of variance (ANOVA), Bonferroni post hoc test, and independent-samples t-test at α=0.05 significance level. ResultsImmediately post-cure, the mean DC values of the different materials were in the following order: GRF>VDF>SDR>VBF>XB>GR>FBF<VD and ranged from 34.7 to 77.1%. 24h post-cure, DC values were in the following order: GRF>VBF>VD>SDR>VDF>GR>XB<FBF and ranged from 50.9 to 93.1%. GRF showed significantly higher DC values than all other materials at both time intervals while XB and FBF showed significantly lower values at 24h post-cure. SignificanceThe 24h post-cure DC values of the bulk-fill composites SDR and VBF are generally comparable to those of conventional composites studied; however, the 24h post-cure DC values of XB and FBF were lower compared to the other materials.

Bond Strength to Unground Enamel and Sealing Ability in Pits and Fissures of a New Self-Adhering Flowable Resin Composite

To evaluate the applicability as a sealant of a new self-adhering flowable resin composite (Vertise Flow, Kerr, VF) by assessing shear bond strength (SBS) to unground enamel and microleakage (microLKG) in sealed pits and fissures. Marketed sealants to be used in combination with phosphoric acid (Guardian Seal, Kerr, GS) or with a self-etch adhesive (Adper Prompt-L-Pop/Clinpro Sealant, 3M ESPE, CS) were compared to VF. For SBS testing on unground enamel 10 molars per group were used. For microLKG assessment, pits and fissures sealing was performed in 12 molars per group. The sealed teeth were immersed in a 50% weight silver nitrate solution for 24 hours and the extent of interfacial leakage was measured. Between-group differences in SBS were assessed using One-Way Analysis of Variance (ANOVA), followed by Tukey test (p < 0.05). microLKG data were analyzed with Kruskall-Wallis ANOVA (p > 0.05). SBS of VF was statistically similar to that measured by CS and higher than that of GS. Interfacial leakage was similar in the three groups. The finding of satisfactory bond strength and sealing ability of VF when compared to the marketed sealants encourages the use of VF in pit and fissure sealing.

3D assessment of void and gap formation in flowable resin composites using optical coherence tomography.

To investigate the effect of composite type and cavity size on gap and void formation using optical coherence tomography (OCT). Class I cavities of two depths (2 mm or 4 mm; 4 mm diameter) were prepared, treated with Tri-S Bond (Kuraray Medical), and bulk filled with either Surefil SDR Flow (SF; Dentsply) or Clearfil Majesty LV (MJ; Kuraray Medical) to form four groups. After 24 h, the specimens were 3D scanned using swept-source OCT (Santec) with 1310 nm laser at a 20 kHz sweep rate. In OCT tomograms, the bonding interface and the bulk of the restorations were evaluated. The percentage values of sealed interfaces (SP) and void volume (VP) for all groups were calculated and statistically analyzed using two- and one-way ANOVA and Tukey's post-hoc test. Selected specimens were cross sectioned and observed using a scanning electron microscope (SEM) and a confocal laser scanning microscope to confirm OCT findings. The following values were obtained for SP and VP, respectively: SF-2mm: 92% and 0.08%; SF-4mm: 66% and 0.13%; MJ-2mm: 86% and 1.79%; MJ-4mm: 33% and 1.96%. Both composites showed a significant increase in gap formation at 4-mm cavity depth (p < 0.001). While SF showed a rather homogeneous bulk compared to MJ, cavity depth did not significantly affect the void volume fraction (p = 0.08). The flowable composite with SDR (stress-decreasing resin) technology performed better than the conventional composite; however, bulk filling a 4-mm-deep cavity will compromise the sealing of the bonding interface regardless of the type of composite. OCT is a unique method of characterizing materials and their behaviors nondestructively and precisely.

Antibacterial, physical and mechanical properties of flowable resin composites containing zinc oxide nanoparticles

ObjectivesThe aim of this study is evaluating the antibacterial activity of resin composites containing ZnO nanoparticles against Streptococcus mutans and examining their physical and mechanical properties. MethodsThe properties of flowable resin composites containing 0–5wt.% nano-ZnO are investigated using different tests:A.Antibacterial activity (including agar diffusion test on the cured resins, direct contact test using bacteria in a liquid medium, evaluating the effect of aging while the samples are adjacent to a liquid medium, and scanning electron microscopy (SEM)).B.Mechanical behavior (including flexural and compressive strength and modulus).C.Curing aspects (including depth of cure and degree of conversion).D.Adhesion properties (including micro-shear bond strength). ResultsAlthough the agar diffusion test reveals no significant difference between the groups, the direct contact test demonstrates that by increasing the nanoparticle content, the bacterial growth is significantly diminished (p<0.05). In the aging test, however, the antibacterial properties reduce significantly (p<0.05). The flexural strength and compressive modulus remains unchanged by incorporation of nanoparticles (p>0.05) while the compressive strength and flexural modulus significantly increase (p<0.05). The ZnO containing resins show significantly lower depth of cure (p<0.05), and higher bond strength (p<0.05). There is no significant difference between the degrees of conversion, measured by FTIR technique, of the groups (p>0.05). SignificanceProduction of a dental resin composite with antibacterial activity without significant sacrificing effect on the mechanical properties is desirable in dental material science.

The Management of Defective Resin Composite Restorations: Current Trends in Dental School Teaching in Japan

The aim of this article is to investigate the contemporary teaching of the management of defective direct resin composite restorations in dental schools in Japan. A questionnaire relating to the teaching of the management of defective resin composite restorations was developed and e-mailed to 29 dental schools in Japan in 2010. Completed responses were received from 19 of the 29 invited schools (response rate = 66%). Eighteen schools (95%) report that they included the teaching of repair of direct defective resin composite restorations in their dental school programs. Thirteen schools reported that they included both clinical and didactic instruction on the repair of direct resin composite restorations. Fourteen schools did not teach any mechanical roughening of the exposed resin composite restoration surface before undertaking a repair. The most commonly reported treatment was acid etching with phosphoric acid (12 schools). The most commonly taught material for completing repairs was a flowable resin composite (16 schools). The teaching of repair of defective resin composite restorations is well established within many Japanese dental schools, to a greater extent than in some other regions of the world. The impact of this teaching on subsequent clinical practices in Japan should be investigated. Furthermore, it is concluded that there is a need for much stronger leadership in operative and conservative dentistry, ideally at the global level, to resolve differences in key aspects of operative procedures such as repairs.

Effect of two different types of fibers on the fracture resistance of endodontically treated molars restored with composite resin.

To compare the in vitro fracture resistance of endodontically treated molars with mesio-occluso-distal (MOD) cavities restored with two different types of fibers. Sixty extracted human mandibular first molars were selected for the study and randomly assigned to six groups (n = 10). Group 1 served as the control. In groups 2 through 6, endodontic access and standard MOD cavities were prepared. Following root canal treatment, group 2 was left unrestored. In group 3, the teeth were restored with composite resin (Venus, Heraeus Kulzer). In group 4, flowable composite resin (Venus, Heraeus Kulzer) was used before restoring the teeth with composite resin. In group 5, leno-woven ultrahigh molecular weight polyethylene ribbon fiber (Ribbond) was inserted in the flowable resin in a buccal to lingual direction, and the teeth were then restored with composite resin. In group 6, translucent glass fiber (Vectris, Ivoclar) was adapted over the flowable resin in the bucco-lingual direction and restored with composite resin. The specimens were stored in 100% humidity at 37°C for 1 day. Compressive loading of the teeth was performed using a universal testing machine at a crosshead speed of 0.5 mm/min. The mean load necessary to fracture the samples was recorded in Newtons (N). Data were subjected to analysis of variance (ANOVA) and Duncan's post-hoc test, where significance was set at p < 0.001. The highest and the lowest mean fracture strengths were found in sound teeth (1598.8 N) and unrestored teeth (393.7 N), respectively. The mean load necessary to fracture the samples was 958.6 N in the polyethylene ribbon group (group 5), 913.2 N in the glass-fiber group (group 6), 699.7 N in teeth restored with flowable resin and composite (group 4), and 729.3 N in group 3 with composite resin alone. Statistical analysis showed significantly higher fracture resistance of both the fiber groups compared to composite resin alone (p < 0.001). Both polyethylene ribbon and glass fiber under MOD composite restorations significantly increased fracture strength with no statistical difference between the two groups. Therefore, both polyethylene- and glassfiber- reinforced composites can be used for access cavity restorations in teeth with weakened cusps.

Effect of adhesive application on the shear bond strength of flowable composite resins and APC plus to orthodontic molar tubes

Objectives: To evaluate the effect of adhesive application on the shear bond strength (SBS) of orthodontic tubes to acid-etched human enamel when using different flowable composite resins and the APC Plus system (APC). Study design: One hundred metal tubes were bonded to human third molars, which were randomly divided into five groups: Tetric EvoFlow (TF); Wave mv Flow (W); Transbond Supreme LV (S); Transbond XT (XT); and APC. For each experimental group, half of the specimens were bonded in combination with Transbond XT adhesive. After 72 h, an SBS test was performed using a universal testing machine. Two-way analysis of variance (ANOVA) was run for multiple comparison tests and for comparing the mean SBS among the 10 subgroups to evaluate the effect of both the composite and the adhesive factors. Then, a Student-Newman-Keuls test was used for pairwise comparisons using the highest mean SBS group as reference. Adhesive Remnant Index scores were determined for the teeth after failure and compared by χ 2-test. Two representative molar surfaces from the 10 subgroups were assessed under scanning electron microscope. Results: The application of adhesive did not have a significant effect, but there was a marked tendency toward the influence of the factor composite on SBS. The mean SBS of tubes bonded with XT with adhesive was significantly higher than that of those bonded with APC with adhesive, TF with and without adhesive, and S with adhesive. Conclusion: Flowable composites and the APC system without intermediate bonding resin could be conveniently applied for orthodontic tube bonding.

Bond Strength of composite repairs using flowable or conventional resins or the association of both

Objectives: The aim of this in vitro study was to evaluate the effects of flowable resin as an intermediate agent on composite repairs on bond strength. Methods: Thirty truncated cones of Grandio SO (VOCO) were prepared and thermo-cycled for 5000 cycles for artificial aging. Specimen’s surface were sandblasted with aluminum oxide, cleaned with air/water spray and conditioned with phosphoric acid for 15s. After that, one coat of Admira Bond Adhesive (VOCO) was applied and light cured for 20s. Specimens were divided into 3 groups according to the repair material used (n= 10): Conventional Resin – Grandio SO (R), A thin layer of Flowable resin – Grandio SO Heavy Flow + conventional Resin (FR) and Flowable resin (F). Over the original specimens, a sectional cone-shape teflon matrix was hold in position , and the cones were built, according the groups described above. Another thirty specimens were built, 10 of each group, simulating a restoration without repair. Specimens were submitted to tensile stress in a universal testing machine. Data were recorded in MPa and evaluated with ANOVA, Tukey´ s and non-paired “t’’ tests. Results: ANOVA showed significant differences between groups which were performed repair (p&lt; 0.00). The results of Tukey´ s test for these groups were: R (19.89 5.31)ab, F+R (14.49 5.59)a, F (20.91 3.99)b. The groups followed by the same letter did not show statistical differences. Non-paired “t” test showed that groups R and F repairs were similar of the correspondent groups which simulated a restoration without repair. Conclusions: The repair with conventional or flowable composite produced bond strength values similar to cohesive strength of the same materials. The use of a thin layer of flowable resin as an intermediate agent in composite repair decreased the bond strength when compared the same method for restoration.

Study of the radio-opacity of base and liner dental materials using a digital radiography system

This study investigated the radio-opacity of commercially available glass ionomer cements (GICs), flowable resin composites (FRCs) and calcium hydroxide cements (CHCs) and compared this with the radio-opacity of enamel, dentine and aluminium stepwedge. 16 GICs, 8 FRCs and 4 CHCs were analysed. Three sets of three samples were prepared: 1 mm, 2 mm and 3 mm thickness for GIC and FRC and 1 mm thickness for CHC. Specimens of enamel and dentine with the same thicknesses were obtained. As a control, an aluminium stepwedge was used. Radiographs were taken with a digital Kodak RVG 5000 (0.32 s, 30 cm). The images were analysed using the Image Tool(®) program (v. 2.00; The University of Texas Health Science Center, San Antonio, TV) to obtain the mean grey values. Analysis of variance was used to investigate the significance of differences among the groups. For pairwise comparisons, the Tukey test was applied (p < 0.05). The GICs Ionomaster (Wilcos, Petrópolis, Brazil), Maxxion (FGM, Joinville, Brazil), Bioglass R (Biodinâmica, Ibiporã, Brazil), Bioglass F (Biodinâmica), Vidrion R (SS White, Rio de Janerio, Brazil) and Vidrion F (SS White), presented radio-opacity lower than that of dentine. All FRCs and CHCs studied showed radio-opacity higher than that of dentine. Vitro Fil (DFL, Rio de Janeiro, Brazil), Magic Glass (Vigodent, Rio de Janeiro, Brazil), Vitrebond (3M, Sumaré SP, Brazil), Riva Self Cure (SDI, Victoria, Australia), Riva Light Cure (SDI), Fill Magic (Vigodent), Opallis (FGM, Joinville, Brazil), Surefil SDR (Dentsply, Milford, DE), Tetric N (Ivoclar Vivadent, Schaan, Lichtenstein), Tetric (Ivoclar Vivadent), Hydro C (Dentsply, Petrópolis, Brazil), Hydcal (Technew, Madalena, Portugal) and Liner (Vigodent) showed radio-opacity similar to or greater than that of enamel for all thicknesses. The increased thickness of the materials studied increases their radio-opacity. Some commercially available GICs used as a base and liner for restorations have a very low radio-opacity (Ionomaster, Maxxion, Bioglass R, Bioglass F, Vidrion R and Vidrion F).

Retentive strength of different intracanal posts in restorations of anterior primary teeth: anin vitrostudy

ObjectivesTo determine the retentive strength and failure mode of undercut composite post, glass fiber post and polyethylene fiber post luted with flowable composite resin and resin-cement.Materials and MethodsCoronal parts of 120 primary canine teeth were sectioned and specimens were treated endodontically. The teeth were randomly divided into 6 groups (n = 20). Prepared root canals received intracanal retainers with a short composite post, undercut composite post, glass fiber post luted with flowable resin or resin-cement, and polyethylene fiber post luted with flowable resin or resin-cement. After crown reconstruction, samples were tested for retentive strength and failure mode. Statistical analysis was done with one-way ANOVA and Tukey tests (p < 0.05).ResultsThere were statistically significant differences between groups (p = 0.001). Mean bond strength in the undercut group was significantly greater than in the short composite post (p = 0.030), and the glass fiber post (p = 0.001) and the polyethylene fiber post group luted with resin-cement (p = 0.008). However, the differences between the undercut group and the groups with flowable composite as the luting agent were not significant (p = 0.068, p = 0.557). Adhesive failure was more frequent in the fiber post groups.ConclusionsAlthough the composite post with undercutting showed the greatest resistance to dislodgement, fiber posts cemented with flowable composite resin provided acceptable results in terms of retentive strength and fracture mode.

Effect of water storage and additional polymerization on the color parameters of flowable resin composites.

Tooth colored dental restorative materials should maintain their chromatic properties throughout their service period. The aim of this study was to examine the possible color changes of flowable resin composite filling materials following water storage. The effect of additional light curing on color stability of restorative materials was also investigated. Six brands of light-cured flowable resin composites of the same shade (A3) were prepared from two groups generated by curing for 20 or 60 seconds. The initial color parameters of the flowable composite samples were measured with a dental colorimeter according to the CIELAB color scale, and the samples were stored in distilled water at 37°C. Following 2 weeks' water storage, the measurements were repeated. The color differences (ΔE*(ab)) were calculated according to the CIELAB formula. Statistical differences between the measurements were analyzed by ANOVA and Duncan's tests. No initial color variation between the samples cured for 20 seconds and 60 seconds was perceptible (ΔE*(ab)<3.3). However, after 2 weeks' water storage, a noticeable color change, ΔE*(ab)>3.3, was detected in Eco-flow, Filtek Supreme and Grandio samples in both polymerization groups. Flowable resin composites may exhibit a significant color change as a result of water storage. Sixty seconds exposure period does not influence the final color. Clinicians should be aware of color shifts in flowable resins.

Marginal sealing ability of silorane and methacrylate resin composites in class II cavities: A scanning electron microscopic study

Aim and Objectives:To comparatively evaluate the microleakage and microgap formation along the gingival margin in class II cavities restored with silorane resin composite and methacrylate resin composite with and without flowable resin liner.Materials and Methods:Sixty human mandibular premolars were distributed into three groups, each group containing 20 teeth (n = 20). Mesial (subgroup A) and distal (subgroup B) box cavities were prepared with gingival margin above and below cemento enamel junction (CEJ), respectively, in each tooth and restored as follows — Group I — Silorane resin composite with self-etch primer and bond (Filtek P90, 3M ESPE MN, USA). Group II — Methacrylate resin composite (Filtek P60, 3M ESPE MN, USA) and self-etch adhesive (Adper Easy one, 3M ESPE MN, USA). Group III — Methacrylate resin composite with self-etch adhesive and a flowable resin liner (Filtek Z350 XT, 3M ESPE MN, USA). The teeth were thermocycled and immersed in 50% silver nitrate solution before sectioning. The specimens were observed under scanning electron microscope for dye penetration and microgap formation. The data was subjected to statistical analysis using Kruskal-Wallis test and Mann-Whitney U test using SPSS version 18.Results:Subgroup A in all the three groups showed significantly less microleakage and microgap formation compared to subgroup B with P < 0.05.Intergroup comparison of subgroup A did not show statistically significant difference, whereas subgroup B showed statistically significant difference for microleakage between group I and group II (P = 0.003), group III and group II (P = 0.002).Conclusion:Silorane resin composite and methacrylate resin with liner showed significantly less microleakage in class II cavities along the gingival margin placed below CEJ compared to methacrylate resin without liner. All the study groups showed less microleakage and microgap formation along the gingival margin placed above CEJ.