Tetric N-Flow Research Articles

Polymerization Stress and Gap Formation of Self-adhesive, Bulk-fill and Flowable Composite Resins.

Bulk-fill materials show a similar or better performance than control flowable materials regarding interfacial integrity. However, some self-adhesive composites need improvements to achieve competitive performance. Objective: This laboratory study compared the polymerization stress and gap formation of self-adhesive, bulk-fill and control flowable composites. The degree of conversion (DC) and post-gel shrinkage were also assessed.Methods: Two self-adhesive (Vertise Flow and Fusio Liquid Dentin), two bulk-fill (Tetric N-Flow Bulk-Fill and Filtek Bulk-Fill Flowable Restorative), and two control flowable (Z350 XT Flowable Restorative and Tetric N-Flow) composites were evaluated. Polymerization stress (PS) was determined in a universal testing machine (n=5). Gap formation was evaluated by scanning electron microscopy in class I restorations (n=6). DC was measured by Fourier transform infrared spectroscopy (n=3). Post-gel volumetric shrinkage (VS) was measured using the strain gauge method (n=5). Data were submitted to one-way analysis of variance or a Kruskal-Wallis test (α=0.05).Results: Vertise Flow and Fusio Liquid Dentin presented the highest interfacial gap (27%±5% and 21%±6%, respectively), which was associated with their highest PS (4.1±0.8 MPa and 3.5±0.6 MPa, respectively) and DC (63%±2% and 60%±2%, respectively) in spite of the lowest VS (1.0%±0.2% and 1.0%±0.3%, respectively). Tetric N-Flow Bulk-Fill and Filtek Bulk-Fill Flowable Restorative presented similar PS (2.9± 0.3 MPa and 2.4±0.2 MPa, respectively) to both control materials. However, the Tetric N-Flow Bulk-Fill showed the lowest gap (7%±2%) and the highest DC (64.3%±0.4%), and the Filtek Bulk-fill presented a marginal gap (17.8%±3.4%) and a DC (54.5%±2.7%) similar to the control materials. The VS values of both bulk-fill materials were similar to those of Tetric N-Flow and lower than that of Z350 XT Flowable Restorative.Conclusions: Bulk-fill composites showed either similar or significantly lower interfacial gaps and PS than the control flowable composites. The self-adhesive composites showed a significantly higher gap percentage and PS than the control and bulk-fill materials.

Effect of luting materials, presence of tooth preparation, and functional loading on stress distribution on ceramic laminate veneers: A finite element analysis

Statement of problemHow the polymerization shrinkage, loading, and mechanical properties of luting materials affect the shrinkage and functional stresses in ceramic laminate veneers (CLVs) with and without tooth preparation is unclear. PurposeThe purpose of this finite element analysis (FEA) study was to evaluate the effect of the polymerization shrinkage, functional loading, and mechanical properties of different luting materials on the stresses in ultrathin 0.3-mm CLVs with and without tooth preparation. Material and methodsThree resin cements, RelyX Veneer (RV), Allcem Veneer APS (AV), Variolink Esthetic LC (VE), and 1 flowable composite resin, Tetric N-Flow (TF), were tested for post-gel shrinkage (Shr), Knoop hardness (KHN), elastic modulus (E), compressive strength (CS), and diametral tensile strength (DTS). IPS e.max CAD disks of 0.3-mm thickness were made for simulating the effects of light attenuation. Eight 2-dimensional finite element models (Marc-Mentat) of a maxillary central incisor were generated to evaluate the polymerization shrinkage stress of different materials for luting 0.3-mm CLVs with or without tooth preparation and the stress during functional loading by using a modified von Mises criterion (mvm). Collected data from Shr, KHN, and E were submitted to 2-way ANOVA and the Tukey HSD test (α=.05). ResultsLight attenuation by the 0.3-mm ceramic disk did not significantly affect the E values, but Shr was significantly lower in VE (26%) and TF (35%). TF had lower volumetric Shr (%) when interposing a ceramic disk (0.31%). Both tested tooth preparation options showed similar stress distributions from polymerization shrinkage or functional loading, with higher stress concentration on the incisal edge and also on the cervical surface. The model featuring tooth preparation and RV resin cement had the highest and VE the lowest stress levels. ConclusionsThe flowable composite resin had similar mechanical properties as the resin cements. The stress distribution from shrinkage and functional loading was similar for both techniques with or without tooth preparation.

Comparison of Shear Bond Strength of Different Wire-Composite Combinations for Lingual Retention: An in Vitro Study

Context: As lingual bonded retainers are required for long-term retention in the oral cavity, the wire-composite combination of choice may be the determining factor for the success of lingual bonded retainers. Aim: We compared the shear bond strength of different wire-composite combinations used for lingual bonded retainers and identified the combination of choice for lingual retention in terms of the shear bond strength. Materials and Methods: A total of 108 extracted human maxillary premolars in pairs were divided into 6 groups of 9 samples each. Three different types of retainer wires (namely, Respond [Ormco Corp., Orange, CA, USA], Leone Ligature Wire [Leone S.p.a., Firenze, Italy], and SRW™ Stranded Retention Wire [Ortho Classic Inc., USA]) were bonded to the teeth with the composites (G-aenial™ Universal Flo and Tetric N-Flow). The shear bond strength was measured on debonding using universal testing machine INSTRON. Results: The maximum shear bond strength (58.28 N) was observed in group IV (Respond wire with Tetric N-Flow), whereas the minimum (25.28 N) was observed in group VI (SRW™ Stranded Retention Wire with Tetric N-Flow). A highly significant difference was observed when the shear bond strength of group IV was compared with all the other groups. Conclusions: The maximum shear bond strength was observed in the wire-composite combination of Respond dead-soft wire with Tetric N-Flow composite. Therefore, it could be the wire-composite combination of choice for bonded lingual retainer.

Evaluation of Marginal Adaptation of a Self-Adhering Flowable Composite Resin Liner: A Scanning Electron Microscopic Study.

Background:“Self-adhering composite resins,” are claimed to eliminate the need for a separate acid etching and bonding agent application step, thus simplifying the direct restorative procedure, both regarding the technique sensitivity and the duration of treatment.Aim:The aim of this study is to evaluate the marginal adaptation of self-adhering flowable composite (Dyad flow) in comparison to the conventional flowable composite (Tetric N-flow) under scanning electron microscope (SEM).Settings and Design:This in vitro study was conducted on 44 extracted human maxillary premolars.Materials and Methods:Box-only Class II cavities on the distal surface were prepared with the dimensions of 4 mm buccolingual width, 2 mm mesiodistal depth, and gingival margin at the cementoenamel junction. They were divided into two groups of 22 teeth each and were restored accordingly: Group I – Gingival floor lined with Tetric N-Flow and were restored with Tetric N-Ceram; Group II – Gingival floor lined with Dyad flow and were restored with Herculite Precis. After thermal cycling, the sectioned tooth-restoration interfaces were evaluated for the marginal adaptation under SEM at ×200 magnification.Statistical Analysis Used:The resultant data were statistically analyzed by applying Chi-square test, using the SPSS (version 16.0) software.Results and Conclusion:There was no statistically significant difference between the study groups regarding the marginal adaptation. The marginal adaptation of the self-adhering flowable composite when used as a liner in Class II restorations was comparable to that of the conventional flowable composite.

Comparative evaluation of bond strength of self-adhering flowable composites to the dentin prepared with different burs: An in vitro study.

Aim:The aim of this study was to evaluate the shear bond strength (SBS) of self-adhering flowable composites on the dentinal surface prepared with carbide and diamond burs.Materials and Methods:A total of 64 extracted mandibular molars were mounted on acrylic resin blocks, and the coronal part of the dentin was exposed and polished. Then, they were divided into Group 1 and Group 2 for carbide and diamond bur preparation, respectively. Two teeth in each group were evaluated under scanning electron microscope, ×500, to view the surface changes following the bur preparation. The remaining teeth were subdivided into Groups A, B, and C to be restored with Constic, Dyad™-flow, and Tetric N Flow composites, respectively. Then, the specimens were stored in distilled water at 37°C for 24 h, and then subjected to universal testing machine to evaluate the SBS and viewed under light stereomicroscope to evaluate the type of failure.Statistical Analysis:SPSS version 22 (IBM Corp) for Windows was used for statistical analysis. The values were subjected to ANOVA followed by Bonferroni post hoc analysis. The values between the groups were analyzed using Student's unpaired t-test.Results:Statistically significant differences in the SBS values were seen between Groups A and C (P < 0.001) and Groups B and C (P < 0.001). Statistically significant differences were seen in SBS values of Dyad-flow (Group B) (P < 0.004) and Tetric N flow (P < 0.007) for surfaces prepared with carbide and diamond burs.Conclusion:It was concluded that the SBS of Tetric-N Flow was higher than that of the experimental groups of Constic and Dyad-flow. Dentinal surface preparation with carbide bur resulted in higher SBS for Tetric N Flow and Dyad-flow but not for Constic.

Evaluation of degree of conversion and the effect of thermal aging on the color stability of resin cements and flowable composite.

Purpose:The aim of this in vitro study was to evaluate the color stability and degree of conversion (DC) of dual-cure and light-cure cements and flowable composites after thermal aging.Materials and Methods:A total of 50 human incisors were prepared and divided into six groups (n = 10). Veneers were fabricated using IPS Empress Direct composite resin were bonded with three types of luting agents: Light-cured, conventional dual, and flowable composite according to the manufacturer's instructions. The groups were as follows: Filtek Z350XT Flow/Single Bond 2, RelyX ARC/Single Bond 2, RelyX Veneer/Single Bond 2, Tetric N-Flow/Tetric N-Bond, and Variolink II/Tetric N-Bond. Commission Internationale de l'Éclairage L*, a* and b* color coordinates were measured 24 h after cementation procedure with a color spectrophotometer and reevaluated after 10,000 thermal cycles. To evaluate the DC 50 specimens (n = 10) of each resin material were obtained and Fourier transform infrared spectroscopy was used to evaluate the absorption spectra. Statistical analysis was performed with one-way ANOVA and Tukey's test (α = 0.05).Results:No statistically significant differences in ΔE* occurred after aging. The greatest change in lightness occurred in the Variolink II resin cement. Changes in red–green hue were very small for the same cement and largest in the Tetric N-Flow flowable resin composite, while the greatest change in blue–yellow hue was a yellowing of the RelyX ARC luting cement. RelyX ARC exhibited the highest DC, and there were no statistically significant differences in DC among the other cements.Conclusions:Resin-based luting agent might affect the final of ceramic veneer restorations. The thermal aging affected the final color of the evaluated materials, and these were regarded as clinically unacceptable (ΔE >3.3).

Physico-mechanical and thermal characteristics of commercially available and newly developed dental flowable composites

In this study, we investigated the structural stability, thermal conductivity, thermal analysis, materials' homogeneity of newly developed flowable composites. 6 different dental flowable composite resins; Grandio Flow (GF), Charisma Flow (CF), Tetric N Flow (TNF), Clearfil Majesty Flow (CMF),3M Filtek Ultimate Flow (3MFU), Voco Amaris Flow (VFA) were used. Restorations were made in standard teflon molds and the materials were light-cured for 20s in a 6 mm × 2 mm teflon mould. After polymerization, samples were kept in distilled water at 37 °C/24 h .It was found that the composites have multiphase component such as metallic dopant and organic binder. The XRD investigation showed that there was a broad halo in the pattern which indicates the organic section in the composites. The FTIR results indicate the bond structure of the composites. The temperature dependence of the thermal conductivity of the composites were found below to 5 mW/K value depending on the type of the composites, which are low enough for dental application. The micro-hardness of the samples was analyzed and the result was compared.

IN VITRO EVALUATION OF WEAR RESISTANCE OF DIFFERENT FISSURE SEALANTS AFTER AGING PROCEDURES

Objective: The purpose of this study is to evaluate the ability of unfilled resin based sealant (Clinpro), glass ionomer fissure sealants (Fuji Triage) and nanofilled resin based fissure sealant (Tetric N-Flow) to resist surface degradation using chewing simulator combined with thermocycling. Methodology: A total of 30 disk shaped specimens were prepared, 10 disks for each material. Surface roughness (Ra) and weight loss were quantitatively measured after 2-body wear testing by using a chewing simulator ‎integrated with thermocycling. Data were statistically analyzed using one-way ANOVA and Bonferroni’s post-hoc test (P ≤ 0.05)Result: Both unfilled resin based sealant (RS) and glass ionomer fissure sealant (GI) showed statistically significant higher (Ra) than nanofilled resin based fissure sealant (NS) before aging procedure. After chewing simulator and thermocycling; there was no statistically significant difference between the (Ra) of three fissure sealant materials. As regard to weight loss (GI) showed the highest mean weight loss followed by (RS) while (NS) showed the lowest mean weight loss. Conclusion: nanofilled resin based fissure sealant showed good resistance to surface degradation compared to other sealants.

MICROLEAKAGE OF CLASS II RESTORATION WITH COMPOSITE INLAY: AN IN VITRO STUDY

Background: Overcoming the obstacles of Class II restoration, especially the microleakage, is a polemic issue. The present study was performed to evaluate the microleakage of Class II restorations using three different techniques. Aims: The aim of this in vitro study was to evaluate the microleakage of Class II restorations using three different techniques. Materials and methods: The study was carried out in the laboratory with paired comparision between groups. Thirty Class II cavities were prepared on extracted non-carious human permanent molars, randomly divided into 3 groups, which were then restored with 3 different methods. Group 1: indirect composite inlay (Tetric N-Ceram) cemented with resin-modified glass ionomer cement (Fuji Plus); Group 2 indirect composite inlay (Tetric N-Ceram) cemented flowable composite (Tetric N-flow); Group 3: direct composite restoration using Tetric N-Ceram. Before immersed to 2% methylene blue solution for 12 hours, all restorations were subjected to thermal cycling (100 cycles 50C – 55 0C). The extent of dye penetration along the gingival wall was assessed using a grade scale from 0 to 3 under 40 times magnification using digital camera Nikon D7000. Results: All types of restorations showed some rate of microleakage. In comparing the three techniques, group 1 demonstrated the significantly higher rate of leakage compared to the others (p&lt;0.05), whereas group 2 and 3 showed no significant difference. Conclusion: Different luting materials have different influences on the microleakage degree along gingival wall of Class II restoration. Key word: composite inlay, class II restoration, microleakage

Bisphenol-A Release and Genotoxicity Differences of Three Branded Adhesives Materials

Objectives: The objective of the study are to determine BPA release and genotoxicity differences between three adhesives, and to determine the relationship between BPA release and genotoxicity. Methods: Three branded adhesives materials were polimerized in mold and immersed in pH 7 and 4 artificial saliva from 24 to 720 hours. The artificial saliva was tested with spectrofotometry test to see BPA release at 24, 240, 480, and 720 hours, then freeze dried to get solid extract. Combination of the extract and lymphocite culture (male and female) then tested with in vitro cytokinesis-block micronucleus (MN) assay to see genotoxicity level of three adhesives at 24, 240, 480, and 720 hours as well. Results: The highest BPA release occured at 720 hours by Tetric N-Flow: 0,013μg/L; Filtek Z350XT: 0,11μg/L; Flowtain LV: 0,036μg/L respectively. There was a statistically significant difference between BPA release with time (F = 505,98; p=0,00) and brands (F = 147,65; p = 0,00). Time and BPA release interaction also showed a statistically significant difference (F=13,35; p=0,00). Genotoxicity can be seen at 720 hours on Flowtain LV sample (MN frequency: male: 0,044; female: 0,053). Conclusions: The number of BPA release of all brand was increasing from 24 to 720 hours and did not influenced by brands. Genotoxicity can be seen from one of the adhesive brand at 720 hours.There was correlation between BPA leaching and micronucleus frequency. DOI: 10.14693/jdi.v22i3.402

Staining resistance of preheated flowable composites to drinking pigmented beverages

ObjectiveThis study aimed to evaluate the influence of the preheating of flowable composite resins on the color stability when exposed to drinking pigmented beverages. MethodsWave (SDI) and Tetric N-Flow (Ivoclar Vivadent) were used. One hundred and twenty specimens (n=10) were photoactivated at different temperatures (25°C and 68°C). After curing, the specimens were immersed in distilled water for 24h (T0) and then subjected to cola drink, grape juice, and distilled water (control) for 7 days (T1). The color of the specimens was measured using a guide spectrophotometer Easy Shade (Vita Zahnfabrik) at T0 and T1 by means of the parameters of CIE-L*a*b*, and the overall color change after T1 (ΔE) was calculated. The data were analyzed by 3-way ANOVA and Tukey test (P<.05). ResultsPreheated materials showed statistically significant lower color change after immersion in cola drink and grape juice (P<.01). Grape juice produced statistically the greatest color change for both materials tested regardless of the temperature (P<.01). ConclusionThe preheating improved staining resistance of both flowable composites tested. Grape juice showed the highest stainability.

Degree of conversion of a flowable composite light-activated through ceramics of different shades and thicknesses

The cementation of thin ceramic veneers employing fluid light-activated resin-based materials is a common procedure in the dental practice. Aim: To evaluate the influence of ceramic thickness and shade on the degree of conversion (DC) of a flowable light-activated material. Methods: flowable resin composite (Tetric N-Flow - shade A1) was light-activated through ceramic discs of two shades (IPS Classic - A1 and A3) in three thicknesses (0.5, 0.7 and 1.0 mm). For control, the resin composite was light-activated without ceramic interposition. DC was evaluated by FTIR (n=5). Data were analyzed by one-way ANOVA and Dunnett's T3 test (α=0.05). Results: Statistically significant differences between groups were observed (p<0.001). Control group (without the interposition of ceramic) showed the highest mean for DC (71.9± 1.7). Considering the interposed ceramic disc groups, the highest DC values were obtained when 0.5 and 0.7 mm A1 ceramics were used (64.6±1.2 and 64.4 5.0, respectively) and the lowest DC values were obtained for 0.7 and 1 mm A3 ceramics (61.74±0.9 and 62.0±1.9, respectively). Conclusions: No flowable resin composite group with interposing ceramics reached a DC similar to the control group.

Strengthening of Porcelain Provided by Resin Cements and Flowable Composites.

This study evaluated the effect of mechanical properties of resin-based luting agents on the strength of resin-coated porcelain. The luting agents tested were two flowable resin composites (Filtek Z350 Flow and Tetric-N Flow), a light-cured resin cement (Variolink Veneer [VV]), and a dual-cured resin cement (Variolink II) in either light-cured (base paste) or dual-cured (base + catalyst pastes [VD]) mode. Flexural strength (σf) and modulus of elasticity (Ef) of the luting agents were measured in three-point bending mode (n=5). Porcelain discs (Vita VM7) were tested either untreated (control) or acid etched, silanized, and coated with the luting agents. Biaxial flexural strength (σbf) of the porcelain discs was tested using a ball-on-ring setup (n=30). The σbf of the resin-coated specimens was calculated at z-axial positions for multilayer specimens in the ball-on-ring test: position z = 0 (ceramic surface at the bonded interface) and position z = -t2 (luting agent surface above ring). The σf and Ef data were subjected to analysis of variance and the Student-Newman-Keuls test (α=0.05). A Weibull analysis was performed for σbf data. Weibull modulus (m) and characteristic strength (σ0) were calculated. Linear regression analyses investigated the relationship between mechanical properties of the luting agents and the strengthening of porcelain. VD had higher and VV had lower mechanical strength than the other materials. At z = 0, all resin-coated groups had higher σbf than the control group. No significant differences between the luting agents were observed for σbf and σ0. At z = -t2, VD had the highest σbf and σ0, whereas VV had the poorest results. No significant differences in m were observed across groups. A linear increase in flexural strength of the porcelain was associated with increased σf and Ef of the luting agents at position z = -t2. In conclusion, resin coating and use of luting agents with better physical properties generally improved the mechanical performance of porcelain.

Effect of Fluoride Gel on Microhardness of Flowable Composites: An In Vitro Study

Objective: Adequate knowledge about restorative materials particularly flowable composite resins with favorable physical properties like optimal microhardness and resistance to environmental factors is a big concern for many dentists. Flowable composites have several applications for fissure sealant therapy and preventive resin restorations (PRR); which are common treatments in pediatric dentistry. Acidulated Phosphor Fluoride (APF) topical gels can cause surface degradation and weight loss in composite resins and decrease their wear resistance. This study aimed to assess the effect of APF gel on the microhardness of flowable composites.Methods: This experimental in vitro study was conducted on 60 specimens measuring 2mm in thickness and 6mm in diameter fabricated of Tetric N-Flow (Ivoclar-Vivadent), PermaFlo (Ultradent) and Denfil (Vericom) flowable composites (n=20 for each group). Specimens were stored in artificial saliva at room temperature for one week. The 20 specimens in each group were randomly divided into 2 subgroups of test and control (n=10). Microhardness was measured using Vickers microhardness tester. In the control groups, 3 indentations were made on each disc on the periphery of a circle with at least 1mm distance from one another and from the specimen margin. The mean microhardness value was then calculated. The mean of all measurements was calculated as well. Test specimens were subjected to (Sultan) 1.23% APF gel for 4min and then rinsed and air- dried. Their microhardness was measured again as described above. Two-way ANOVA was used to compare the effect of APF gel and type of composite on the microhardness of different flowable composites.Results: Based on the results, the microhardness of Denfil, PermaFlo and Tetric N-Flow was 16.5 (1.32), 37.36 (2.13) and 20.39 (0.52) before and 16.46 (2.20), 35.04 (2.43) and 19.13 (2.20) after theapplication of APF gel, respectively. The difference between the before and after values for each composite was significant (p=0.193) while the difference between different composites was statistically significant in this regard (p<0.001).Conclusion: Exposure of Denfil, PermaFlo and Tetric N-Flow flowable composites to APF gel for 4min had no effect on their microhardness.

Intraorifice sealing ability of different materials in endodontically treated teeth: An in vitro study.

Background:Microbial contamination of the pulp space is one of the major factors associated with endodontic failure. Thus, in addition to a three dimentional apical filling a coronal seal for root canal fillings has been recommended.Aim:The present study was conducted to evaluate and compare the intra-orifice sealing ability of three experimental materials after obturation of the root canal system.Materials and Methods:Fourty single rooted mandibular premolars were decoronated, cleaned, shaped and obturated. Gutta-percha was removed to the depth of 3.5 mm from the orifice with a heated plugger. Ten specimens each were sealed with Light Cure Glass Ionomer Cement (LCGIC), Flowable Composite (Tetric N-Flow), and Light Cure Glass Ionomer Cement with Flowable Composite in Sandwich Technique along with a positive control respectively and roots submerged in Rhodamine-B dye in vacuum for one week. Specimens were longitudinally sectioned and leakage measured using a 10X stereomicroscope and graded for depth of leakage.Results:According to the results of the present study LC GIC + Tetric N Flow demonstrated significantly better seal (P < 0.01) than LC GIC. However there was no statistically significant difference in leakage (P > 0.01) between Tetric N-Flow and LCGIC+Tetric N-Flow groups.Conclusion:In the current study LCGIC+Tetric N-Flow was found to be superior over other experimental materials as intra-orifice barriers.

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.

An evaluation of three fissure sealants microleakage with presence or absence of bonding agent through time intervals (In vitro study)

Pit and fissure sealant have been considered an outstanding adjunct to oral health care in the decrease of occlusal caries onset and low progression. The aims of this in vitro study were to evaluate the marginal microleakage of three different types of fissure sealants (SDI, Tg and tetric N-flow) by time interval, one day and 45 days, in the presence or absence of bonding agent among maxillary and mandibular teeth. Materials and methods: Seventy two sound human maxillary and mandibular first premolar teeth were collected which were free from obvious carious lesions. The teeth were randomly divided into two main equal groups, group (1) and group (2), each group consists of (36) teeth involving equal numbers of maxillary and mandibular teeth. The first group incubated for one day, the second incubated for (45) days. Each group divided into two subgroup; one of them treated with bonding agent while the other without. Then each subgroup was treated with three different materials which were; Tg sealant (without fluoride) group (A), SDI sealant (containing fluoride) group (B) and Tetric N- flow (flowable composite) group (C). Each one consist of six teeth involving three maxillary and three mandibular. Then dye penetration tested by using methylene blue dye, then the teeth cleaned and sectioned by sectioning device and tested under microscope. Results, the results had shown that, group (C+) in both incubation periods have no microleakage (score 0), but there was an opposite effect when using bonding agent with sealant materials not containing filler particles that showed a significant increase in the microleakage rate as shown in groups (A+ and B+). The opposite effect was seen also when used sealant materials containing filler particles but without bonding agent that seen in group (C) during both incubation periods that showed significant increasing in microleakage rate. While the effect of fluoride was very clear in decreasing significantly the microleakage rate after (45) days of incubation in both groups that treated with and without bonding agent (groups B and B+). Concerning the anatomical variation, there were no significant changes in most groups regarding the microleakage rate. Conclusions: Results had shown that the microleakage can be prevented by using of flowable composite containing nanofillers that treated with bonding agent after etching of enamel with 35% phosphoric acid gel.

Direct and indirect bonding of wire retainers to bovine enamel using three resin systems: shear bond strength comparisons

Objective: We compared the shear bond strength (SBS) of lingual retainers bonded to bovine enamel with three different resins using direct and indirect methods. Methods: Both ends of pre-fabricated twisted ligature wires were bonded to bovine enamel surfaces using Light-Core, Tetric N-Flow, or Transbond XT. Phosphoric acid-etched enamel surfaces were primed with One-Step prior to bonding with Light-Core or Tetric N-Flow. Transbond XT primer was used prior to bonding with Transbond XT. After 24 hours in water at 37 o C, we performed SBS tests on the samples. We also assigned adhesive remnant index (ARI) scores after debonding and predicted the clinical performance of materials and bonding techniques from Weibull analyses. Results: Direct bonding produced significantly higher SBS values than indirect bonding for all materials. The SBS for Light-Core was significantly higher than that for Tetric N-Flow, and there was no significant difference between the direct bonding SBS of Transbond XT and that of Light-Core. Weibull analysis indicated Light-Core performed better than other indirectly bonded resins. Conclusions: When the SBS of a wire retainer is of primary concern, direct bonding methods are superior to indirect bonding methods. Light-Core may perform better than Transbond XT or Tetric N-Flow when bonded indirectly.

Effect of an intermediate bonding resin and flowable resin on the compatibility of two-step total etching adhesives with a self-curing composite resin

This study compared the effect of an activator, intermediate bonding resin and low-viscosity flowable resin on the microtensile bond strength of a self-curing composite resin used with two-step total etching adhesives. Twenty extracted permanent molars were used. The teeth were assigned randomly to nine groups (n=10) according to the adhesive system and application of additional methods (activator, intermediate adhesive, flowable resin). The bonding agents and additional applications of each group were applied to the dentin surfaces. Self-curing composite resin buildups were made for each tooth to form a core, 5mm in height. The restored teeth were then stored in distilled water at room temperature for 24h before sectioning. The microtensile bond strength of all specimens was examined. The data was analyzed statistically by one-way ANOVA and a Scheffe’ s test. The application of an intermediate bonding resin (Optibond FL adhesive) and low-viscosity flowable resin (Tetric N-flow) produced higher bond strength than that with the activator in all groups. Regardless of the method selected, Optibond solo plus produced the lowest μ TBS to dentin. The failure modes of the tested dentin bonding agents were mostly adhesive failure but there were some cases showed cohesive failure in the resin. [J Kor Acad Cons Dent 34(5):397-405, 2009]