Degree Of Conversion Values Research Articles

Does the Conditioning Mode and Duration of Universal Adhesives Affect the Bonding Effectiveness to Fluorotic Enamel?

To compare the adhesive-enamel microshear bond strength (µSBS), in situ degree of conversion (DC), and the enamel-etching pattern of universal adhesives when applied for a prolonged period in the self-etch vs the etch-and-rinse mode in fluorotic enamel. Ninety-six human molars (48 with a Thylstrup and Fejerskov index [TFI] score of 0 and 48 with TFI score of 4) were sectioned into four parts and divided into 24 experimental groups based on enamel surface (sound enamel or fluorotic enamel), adhesive (Clearfil Universal Bond, Futurabond U, iBond Universal, or Scotchbond Universal), and enamel treatment/application time (etch-and-rinse mode [ER] or self-etch mode with application times of 20 s [20SE] and 40 s [40SE]). The specimens were stored for 24 h and tested in shear at 1.0 mm/min (μSBS). Adhesive-enamel interfaces were evaluated for DC using micro-Raman spectroscopy. The enamel-etching pattern was evaluated using SEM. For each adhesive, data from µSBS and DC were analyzed separately using two-way ANOVA and Tukey's post-hoc test at α = 0.05. On sound enamel, 40SE usually resulted in statistically similar mean µSBS (p > 0.52) and statistically significantly improved mean DC values (p < 0.001) compared with the ER mode. Moreover, significantly improved mean µSBS and DC values were obtained compared with 20SE (p < 0.01). On fluorotic enamel, there was no statistically significant difference in µSBS between the experimental groups (p > 0.76). However, for each applied adhesive, 40SE resulted in improved mean DC values compared with 20SE or ER (p < 0.001). The deepest enamel-etching pattern was obtained in ER mode, followed by 40SE in sound and fluorotic enamel. Compared with ER mode, the prolonged application time of universal adhesives in SE mode in fluorotic enamel increased the DC, enhanced enamel-etching pattern and promoted similar results in terms of adhesive-enamel bond strength.

Physical and photoelastic properties of bulk-fill and conventional composites.

PurposeThis study evaluated the influence of thickness increment on degree of conversion (DC), Knoop microhardness (KHN), and polymerization-shrinkage stress (PSS) by photoelasticity of three dental composites.MethodsFor DC and KHN, 45 samples were prepared and divided into nine groups (n=5), according to composite (microhybrid [Filtek Z250 - Z250], bulk-fill flowable [SureFil SDR Flow - SDR], and nanohybrid composite [N’Durance - NDU]) and increment thickness (1, 1.5, and 3 mm). PSS was measured by photoelastic analysis. Composites were placed into a photo-elastic model cavity and light-cured. DC and KHN data were subjected to two-way ANOVA and Bonferroni post hoc test. PSS results were qualitatively evaluated through Kruskal–Wallis test.ResultsSDR showed the highest DC values. At top and bottom surfaces, the highest KHN was obtained by Z250. Z250 showed higher PSS than SDR in 1.5 mm increments. NDU showed higher PSS than SDR in 3 mm increments.ConclusionThe bulk-fill composite demonstrated better DC and similar KHN and PSS in deeper layers compared to conventional composites. Bulk-fill composites may perform as well as conventional nanohybrid and microhybrid composites.

Degree of Conversion of Three Light-Cured Orthodontic Adhesives

Introduction: The aim of this in-vitro study was to analyze the polymerization ability of 3 light-cured orthodontic adhesives by determining the degree of conversion (DC). Materials and Methods: Fourier transform infrared spectroscopy (FTIR) was used to evaluate the DC after polymerization immediately, 1 day, 7 days, and 30 days. The adhesives investigated were Transbond XT (3M Unitek, USA), Grengloo (Ormco Corp., USA), and Green Glue (Hangzhou Biomaterials, China). Twelve stainless steel brackets (n=4) were used and the adhesives were cured with Bluephase G2 (Ivoclar Vivadent, Liechtenstein). The data were analyzed by Kruskal-Wallis test for comparing materials and Friedman test for comparing the time periods. Results: The DC values were significantly different among the materials and among the time periods. The highest DC in each period was obtained for Grengloo and the lowest DC was observed for Transbond XT. Thus, there were significant differences between the DC values of Grengloo and Transbond XT in each period. Among the time periods, DC% at T1 (Immediately) and T3 of the material were significantly different. The DC values of all adhesives increased extremely from immediately following curing to 1 day and then slightly increased from 1 day to 7 days. Conclusions: Grengloo showed the highest levels of DC at all tested periods. The percentage values of DC largely increased from immediately following curing to 1 day. This concluded that monomers in orthodontic adhesives kept converting even after completion of photoactivation.

Polymerization kinetics of experimental bioactive composites containing bioactive glass

ObjectivesTo investigate the polymerization kinetics and the degree of conversion (DC) of experimental resin composites with varying amount of bioactive glass 45S5 (BG). MethodsExperimental resin composites based on a photo-curable Bis-GMA/TEGDMA resin system were prepared. The composite series contained 0, 5, 10, 20, and 40 wt% of BG and reinforcing fillers up to the total filler amount of 70 wt%. Composite specimens were light cured with 1219 mW/cm2 for 20 or 40 s and their DC was monitored during 5 min at the data collection rate of 2 s−1 using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). ResultsThe 5-min DC values for experimental composites were in the range of 42.4–55.9% and 47.3–57.9% for curing times of 20 and 40 s, respectively. The differences in the 5-min DC between curing times of 20 s or 40 s became more pronounced in materials with higher BG amount. Within both curing times, a decreasing trend of the 5-min DC values was observed with the increasing percentage of BG fillers. The maximum polymerization rate also decreased consistently with the increasing BG amount. ConclusionsUnsilanized BG fillers showed a dose-dependent inhibitory effect on polymerization rate and the DC. Extending the curing time from 20 to 40 s showed a limited potential to improve the DC of composites with higher BG amount. SignificanceThe observed inhibitory effect of BG fillers on the polymerization of resin composites may have a negative influence on mechanical properties and biocompatibility.

Polymerization Efficiency of a Dual-Cured Resin Cement through Zirconia with Three Different Cusp Inclinations

Assessing the polymerization efficiency of a dual-cured resin cement through zirconia with three different cusp inclinations is the aim of this study. Seventy-two resin cement (Multilink Speed) specimens were light-cured through the zirconia with three different cusp inclinations (30°, 20°, and 0°) for 20 s or 40 s (n=12). For each group, the Vickers hardness (VH) measurement was performed on half of the specimens, whereas the degree of conversion (DC) was tested for the other half with a Fourier transform infrared spectrometer. The recorded data were analyzed with a two-way ANOVA. Varied VH (32.3 ± 3.2–40.3 ± 4.8) and DC (50.5% ± 3.0%–59.6% ± 2.4%) values were obtained from different groups. The cusp inclinations significantly affect the VH (p=0.001) and DC (p&lt;0.001) of the resin cement, and the curing time exhibited a significant effect on the DC (p=0.014) of resin cement but not on the VH (p=0.167). In conclusion, the cusp inclination of zirconia significantly affects the polymerization efficiency of dual-cured resin cement.

The degree of conversion and class II cavity microleakage of different bulk fill composites placed with different restorative techniques

ObjectivesThe current study aimed to investigate the degree of conversion and microleakage of bulk fill composites placed using different restorative techniques. Materials and methodsFour types of resin composites were used: Incrementally-placed Filtek Z350 XT (INC), Filtek Bulk Fill Posterior Restorative (B), Filtek Bulk Fill Flowable (F), 3M ESPE, United States, and SonicFill (SON), Kerr, United States. For the degree of conversion (DC) test, five cylindrical samples were prepared for each group (5 mm diameter and 5 mm depth) (n = 5). Five groups, representing different material-technique combinations, were investigated: Group (INC) in which the incremental technique was used for packing Z350 composite (control), Group (B) in which Filtek Bulk Fill Posterior Restorative was placed as a one 5 mm deep increment, Group (FB-1C) in which Filtek Bulk Fill Flowable was used to fill 2 mm in the base of the mold followed by 3 mm Filtek Bulk Fill Posterior Restorative on top of it then both materials were cured simultaneously, Group (FB-2C) in which 2 mm of Filtek Bulk Fill Flowable was placed at the base of the mold and cured then the rest of the mold was filled with Filtek Bulk Fill Posterior Restorative followed by a final cure, and finally Group (SON) in which SonicFill composite was placed as a one 5 mm increment. The DC of both top and bottom surfaces of each sample was measured using Fourier-transform infrared spectroscopy-Attenuated Total Reflectance (FTIR-ATR). Forty-five extracted human premolars were used for the microleakage assessment. One or two class II slot cavities, with standardized dimensions, were prepared in each tooth. Each of the five investigated groups was represented by 11 cavities (n = 11). The cavities were filled using the same composite material-technique combinations used for the DC test. The restored teeth were thermocycled then immersed in 2% methylene blue solution for 24 h at 37 °C. Dye penetration was assessed by examining longitudinal mesio-distal sections through the restored teeth using a stereomicroscope at 25× magnification. The microleakage was scored using predetermined scoring criteria. The results were statistically analyzed. ResultsThe (INC) group showed significantly higher DC for the top surface than all bulk fill groups. No significant difference was found between the (INC), (FB-1C) and (FB-2C) groups regarding the DC of the bottom surface and the three groups had the highest DC while the (SON) group had the lowest DC values. Comparing the top and bottom surfaces of each single group, only the (FB-1C) and (FB-2C) groups showed a significant difference. No significant difference was found between the microleakage scores of the five investigated groups. ConclusionsConventional incrementally-placed composite has a higher DC compared to all bulk fill types regardless of the technique used for the bulk fill composite. The sonic-activated composite exhibits lower DC of the bottom composite surface than all other bulk fill composites. Regarding the microleakage, bulk fill composites, used with any of their possible techniques, do not perform any inferior compared to incremental composites.

Influence of light energy density, composite type, composite thickness, and postcuring phase on degree of conversion of bulk-fill composites

Context:Achieving a high degree of conversion (DC) is one of the major concerns during photopolymerization of bulk-fill composites.Aims:To evaluate the effect of light energy densities (11.2 J/cm2 and 20 J/cm2) on the DC and variation of DC in the 24-h postcuring of four bulk-fill composites: SDR, Venus Bulk Fill, MI FIL, and Tetric N-Ceram Bulk Fill at simulated clinically relevant filling depths.Settings and Design:This was an in vitro comparative study.Subjects and Methods:A total of twenty samples were prepared using a teflon mold. VALO curing light was used with two light intensity modes of 1000 mW/cm2 for curing time of 20 s and 1400 mW/cm2 for curing time of 8 s. The energy density was calculated as follows: energy density (J/cm2) is the light intensity (mW/cm2) applied during a certain time (s) divided by 1000. The DC was measured at two time intervals: immediately postcure and after 24-h storage in artificial saliva using an Fourier-transform infrared spectroscopy equipped with attenuated total reflectance accessory.Statistical Analysis Used:ANOVA and Bonferroni test at P < 0.05.Results:High energy density (20 J/cm2) leads to higher DC. Thickness, type of composites, and postcuring phase strongly influence the DC. DC values of the top surface for all the bulk-fill materials investigated were found significantly greater (P < 0.005) than those of their bottom surface. Among composites, SDR showed highest DC. DC strongly increased after 24-h postcure by 32% on top surface and 76% on bottom surface.Conclusions:Energy density more than 20 J/cm2, derived by increasing curing time and low power density, helps obtain a high DC of bulk-fill composites for adequate clinical performance.

Effect of the Bis-Dimethylamino Benzydrol Coinitiator on the Mechanical and Biological Properties of a Composite.

To examine the effect of the alternative coinitiator 4,4'bis dimethylamino benzydrol (BZN) in degree of conversion (DC), mechanical and biological properties of experimental composites. The coinitiator BZN was used in three concentrations (0.2, 0.5 and 1.2%), and the coinitiator DMAEMA was used as control at the same concentrations as above. The molar concentration of camphorquinone (CQ) and coinitiators was kept constant (1:1). The composites were manipulated and submitted to microhardness test (VHN), flexural and compressive strength (in MPa), elastic modulus (GPa), DC (FT-IR) and in vitro cytotoxicity (against 3T3 fibroblastic cells) of the experimental resins. Data were subjected to two-way ANOVA and Tukey post-test (α=0.05). The experimental composite resin with BZN showed higher DC values compared to control DMAEMA groups. For the mechanical properties, microhardness values were higher in BZN groups; flexural strength and elastic modulus were similar between all the groups. Compressive strength for groups BZN0.5 and DMAEMA0.5 were not statistically different, being the lowest values attributed to group BZN0.2. The experimental resins with BZN and DMAEMA were considered nontoxic against 3T3 fibroblasts. The inclusion of the coinitiator BZN in experimental composites was considered nontoxic against 3T3 fibroblast cells, without compromising DC and mechanical properties.

The use of micro-Raman spectroscopy for the analysis of caries-affected dentin adhesive interfaces

The purpose of this work was to study the adhesive interface created, with an universal adhesive system (Futurabond M+), between two types of dentin substrates and a restorative material. To fulfill this purpose, we evaluated both the degree of conversion (DC) of the adhesive system and the degree of demineralization (DD) of the dentin, using μ-Raman Spectroscopy, and the morphology of the adhesive interface under Scanning Electron Microscopy (SEM). Two types of dentin were used – sound, from a healthy tooth, and affected, collected from the deepest layer of a carious lesion, without bacteria, partially demineralized however physiologically remineralizable. The universal adhesive system was applied using two available modes - etch-and-rinse (ER) and self-etch (SE). Analyses were performed after 24 h and 6 months of the restorative procedure.Significant differences were found between adhesive modes in the DD of sound substrate specimens after 6 months aging and in the DD of affected substrate specimens, after 24 h and 6 months aging. Average DD values were, overall, higher with the ER mode.Average DC values ​were substantially high (DC ≥ 78%) overall, independently of the experimental group analised. DC values were on average lower ​​closer to the dentin substrate and higher closer to the adhesive layer. The morphology of the interface was consistent with the results obtained by the μ-Raman Spectroscopy technique.

Effectiveness of high irradiance for short-time exposures on polymerization of composite under metal brackets.

To evaluate the effect of different curing modes available in a dental light-curing unit on degree of conversion (DC) of a composite photoactivated under a metal orthodontic bracket. The average irradiance and total energy delivered by three curing modes (standard, high, and extra power) of a multiwave LED unit (Valo Cordless, Ultradent Products, South Jordan, Utah) were measured using the longest time available for each mode (20, 4, and 3 seconds, respectively). Brackets (n = 3/group) were bonded to molar epoxy resin replicas using each curing mode. Mesiodistal sections, 0.5 mm thick, were assessed using an infrared spectrometer microscope. Spectra of composite beneath the brackets were sequentially collected using the mapping tool in near-infrared (NIR)-transmittance mode. Composite conversion was mapped between the mesial and distal edges of the bracket base using 400-μm steps for a total of 10 measurements per specimen. Data from irradiance and total energy were analyzed by one-way ANOVA, while data of DC were analyzed with two-way repeated measures ANOVA (α = 0.05). The highest DC values were observed for standard power (mean 56%, P < .05), while no difference was observed between high (50%) and extra power (49%) modes. Regarding the site of measurement, higher DC was observed close to the bracket edges (52%, P < .05). The use of high irradiance for a short time slightly reduced the DC. The small magnitude of reduction suggests that use of a high irradiance protocol is a clinically valid approach when bonding metal brackets.

The influence of delayed light curing on the degree of conversion and polymerization contraction stress in dual-cured resin luting agents

The aim of the study was to assess the effect of delayed photo-initiation on the polymerization contraction stress (PCS) and degree of conversion (DC) of a dual-cure resin-luting agent. Thirty-five disk (6 mm × 1 mm) samples (n = 10 each group) of dual cure resin luting agent for PCS assessment were fabricated and polymerized using two illuminated quartz rods. Based on the delay in photo-initiation, 30 disks were divided among six groups [group A-0 min (min) delay, group B-2 min, group C-4 min, group D-6 min, group E-8 min and group F-10 min]. A non-photoinitiated group (group G – chemical cure – n = 5) was included as control. The PCS for all specimens was assessed using a Tensometer. For DC evaluation thirty-five specimens were divided into seven groups with delays in photo-initiation (group H-0 min, group I-2 min, group J-4 min, group K-6 min, group L-8 min and group M-10 min, group N-chemical cure). DC was assessed using attenuated total reflectance spectroscopic technique. Statistical comparison among groups was performed using analysis of variance (α = 0.05). The maximum and minimum PCS and DC values with delayed photo-initiation was observed in group-C (3.34 MPa) & group-F (2.44 MPa); and group-M (0.78 MPa) and group-H (0.55 MPa) respectively. Chemically cured samples showed the least PCS (group-G, 1.94) and DC (group-N, 0.53) values in their respective categories. PCS significantly decreased with delayed photo-initiation. A significant increase in DC was noticed when photo-initiation was delayed in the dual cure resin luting agent.

Resin-dentin bond stability and physical characterization of a two-step self-etching adhesive system associated with TiF4

ObjectivesTo evaluate the bond strength to superficial (SD) and deep (DD) dentin after the use of 2.5% (T2.5%) or 4% (T4%) titanium tetrafluoride (TiF4) in aqueous solution as a dentin pretreatment, or when incorporated into the primer (T2.5%P and T4%P) of an adhesive system (Clearfil SE Bond/CL). Degree of conversion (DC), particle size (PS), polydispersity index (PI) and zeta potential (ZP) of the solutions were evaluated. MethodsFifty molars were sectioned longitudinally to obtain two slices of each tooth, which were demarcated into SD and DD. Treatments were applied (n=10): CL; T2.5%; T4%; T2.5%P; T4%P. After 24h or 180days storage, microshear bond strength tests were performed. The DC values of T2.5%P and T4%P were evaluated by FTIR. PS, PI and ZP were measured using dynamic light scattering. ResultsAnalysis of mixed models showed significant effect of concentration of TiF4 * solution * storage time (p=0.0075). There were higher bond strength values in SD than in DD (p=0.0105) for all treatments in both times. The failure mode showed adhesive failures in the majority of groups, irrespective of depth and time (p=0.3746). The bond strength values were not affected by treatments. Lower average particle size was observed for T2.5%P and T4%P at baseline. T2.5% and T4% showed a trend towards agglomeration. SignificanceHigher bond strength values were achieved at SD for all treatments and times. The failure modes observed were adhesive. TiF4 incorporation did not affect DC. T2.5%P and T4%P presented excellent stability over time.

Effect of monomer type on the C[dbnd]C degree of conversion, water sorption and solubility, and color stability of model dental composites

ObjectiveThis study has investigated the influence of BisGMA, BisEMA, BisEMA 30, and two UDMA-based monomers (UDMA and Fit 852), with TEGDMA as co-monomer, on the degree of conversion, water sorption, water solubility, and optical properties of experimental dental composites. MethodsMaterials were formulated at 70/30 molar rations using BisGMA, BisEMA, BisEMA 30, UDMA or FIT 852, as base monomers, combined with TEGDMA. 60wt% of silanated-glass particles was added. Degree of conversion (DC) and polymerization kinetics were monitored using Fourier-transformed infrared spectroscopy in the near-IR range. Water sorption (Wsp) and solubility (Wsl) were assessed using mass variation after 60days water storage. Color was evaluated using a digital spectrophotometer, applying the CIELab parameters 24h after dry storage and 60days after water immersion to calculate ΔE values. All data were analyzed using ANOVA and Tukey’s test (pre-set alpha=0.05). ResultsThe BisGMA-based co-monomer mixture presented the lowest DC (62±1%), whereas BisEMA 30 had the highest DC value (95±2%). The highest Wsp was observed for BisEMA 30 (12.2±0.8%), and the lowest for BisEMA (0.4±0.1%). BisEMA has shown the lowest Wsl (0.03±0.01%) and BisEMA 30 the highest one (0.97±0.1%). The ΔE values showed that BisEMA 30 (7.3 color units) and Fit 852 (3.8 color units) altered the color stability providing ΔE>3.3, which is considered clinically unacceptable. ConclusionsThe chemical composition and structure of the base monomer influenced the degree of conversion, water sorption, water solubility, and color stability. Considering the overall results, it is possible to state that the base monomer BisEMA mixed with the co-monomer TEGDMA presented the best performance in terms of all the parameters tested. SignificanceThe resin matrix composition might influence physical property degradation processes and color stability of dental resin composites. Formulations based on BisEMA seem most promising for materials’ development.

Influence of Curing Mode on the Surface Energy and Sorption/Solubility of Dental Self-Adhesive Resin Cements.

This study investigated the influence of curing mode (dual- or self-cure) on the surface energy and sorption/solubility of four self-adhesive resin cements (SARCs) and one conventional resin cement. The degree of conversion (DC) and surface energy parameters including degree of hydrophilicity (DH) were determined using Fourier transform infrared spectroscopy and contact angle measurements, respectively (n = 5). Sorption and solubility were assessed by mass gain or loss after storage in distilled water or lactic acid for 60 days (n = 5). A linear regression model was used to correlate between the results (%DC vs. DH and %DC/DH vs. sorption/solubility). For all materials, the dual-curing consistently produced significantly higher %DC values than the self-curing (p < 0.05). Significant negative linear regressions were established between the %DC and DH in both curing modes (p < 0.05). Overall, the SARCs showed higher sorption/solubility values, in particular when immersed in lactic acid, than the conventional resin cement. Linear regression revealed that %DC and DH were negatively and positively correlated with the sorption/solubility values, respectively. Dual-curing of SARCs seems to lower the sorption and/or solubility in comparison with self-curing by increased %DC and occasionally decreased hydrophilicity.

Influence of Photoinitiator System on Physical-Chemical Properties of Experimental Self-Adhesive Composites.

The aim of this study was to determine the influence of photoinitiator systems on physical-chemical properties of flowable composites. Conventional (CFC), composed by bisphenol-glycidyl dimethacrylate (BisGMA)+triethyleneglycol dimethacrylate (TEGDMA), and self-adhesive (SAFC), composed by BisGMA+TEDGMA+bis{2-(methacryloyloxy) ethyl} phosphate (2MP), flowable composites were developed. Five photoinitiator systems were tested: camphorquinone (CQ), ethyl-4-dimethylaminobenzoate (EDMAB), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), phenylbis (2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), CQ+EDMAB+TPO and CQ+EDMAB+BAPO. A two-peak LED was used; degree of conversion (DC) and the maximum polymerization rate (RPmax) were determined by near infrared spectroscopy. For the yellowing degree a spectrophotometer was used. Water sorption (Wsp) was obtained after 30 days of water storage (n=5). Data were submitted to two-way analysis of variance and Tukey's test (a=0.05). BAPO presented the highest DC and RPmax values for both series. SAFCs presented lower DC and RPmax for CQ+EDMAB-based materials. Greater yellowing was observed for SAFCs compared with CFCs, except for BAPO. Greater Wsp was observed for SAFCs compared with CFCs. The photoinitiator did not influence Wsp for CFCs, but TPO and BAPO presented the highest Wsp in SAFCs. The photoinitiator system affected differently the physical-chemical properties of CFCs and SAFCs.

Effects of delivering the same radiant exposures at 730, 1450, and 2920 mW/cm2 to two resin-based composites.

Objective:To evaluate the effects of curing two resin-based composites (RBC) with the same radiant exposures at 730, 1450, and 2920 mW/cm2.Materials and Methods:Two types of RBC, Filtek Supreme Ultra and Tetric-EvoCeram-Bulk Fill, were light-cured to deliver the same radiant exposures for 5, 10, or 20 s by means of a modified Valo light emitted diode light-curing unit with the light tip placed directly over each specimen. The RBC was expressed into metal rings that were 2.0 and 4.0 mm in thickness, directly on an attenuated total reflectance Fourier transform infrared plate heated to 33°C, and the degree of conversion (DC) of the RBC was recorded. The specimens were then removed and the Knoop microhardness (KHN) was tested at both the bottom and the top of each specimen. The KHN was tested again after 24 h and 7 days of storage in the dark at 37°C and 100% humidity. The DC and KHN results were analyzed with Fisher's protected least significant difference at α = 0.05.Results:The DC values for the specimens cured at the three different irradiance levels were similar. However, at different depths, there were differences in the DC values. In general, there were no clear differences among the samples cured in the three different groups, and the KHN was always greater 24 h and 7 days later (P < 0.05).Conclusions:Despite the curing time, and as long as the samples were cured with the same radiant exposures, there were no significant effects on the DC and KHN of both RBCs.

Evaluation of hardness and degree of conversion of different bulk-fill materials cured with Quartz Tungsten Halogen and light emitting diode devices

Aims: The aim of this study is to evaluate the hardness and degree of conversion (DC) of different bulk-fill materials when cured with the Quartz Tungsten Halogen (QTH) and Light emitting diode (LED) devices using same energy density. Settings and Design: This was in vitro study. Materials and Methods: Three different bulk-fill materials, i.e., Filtek™ [3M ESPE], Tetric® N-Ceram [Ivoclar Vivadent], and SDR (Smart Dentin Replacement) by Dentsply Caulk, were used for making 180 samples (60 samples each) in Teflon mold. Out of these 60 samples, samples of three heights were prepared, i.e., 2 mm, 4 mm, and 6 mm (20 each). All the sample molds were filled in single increment and were exposed to the QTH and LED using the same energy density. Then, these samples were tested for microhardness using the Vickers hardness (VH) testing machine (Mitutoyo, Japan) and DC using Fourier Transform Infrared Spectroscope (Cary 630 FTIR Agilent Technologies, Germany). Statistical Analysis Used: The statistical analysis was performed on the collected data. The Kolmogorov–Smirnov and Shapiro–Wilk tests showed that the data are normally distributed. Since all the variables were continuous and statistically independent, independent t-test was applied to compare mean values of VH and DC of inter groups. Results: The statistical analysis of readings revealed that there was no significant difference in the mean values of microhardness and % DC for both groups cured by QTH and LED. Conclusions: It can be concluded that irrespective of the type of the light cure unit if the energy density applied is same then almost similar performance can be expected from the devices.

Adhesives Doped with Bioactive Niobophosphate Micro-Filler: Degree of Conversion and Microtensile Bond Strength.

To evaluate the effect of incorporating niobium phosphate bioactive glass (NbG) into commercial etch-and-rinse adhesive systems, with and without silane, on their degree of conversion (DC) (%) and microtensile bond strength (μTBS). The NbG micro-filler was added to two etch-and-rinse adhesive systems: One Step (OS) and Prime & Bond (PB) at 40% concentration. The following groups were formed: control without glass addition OS; addition of unsilanized NbG (OSNbG); addition of silanized NbG (OSNbGS); control without glass PB; addition of unsilanized NbG (PBNbG); addition of silanized NbG (PBNbGS). The DC was determined using total Fourier spectroscopy reflection (FTIR/ATR). For μTBS testing, 48 human third molars (n=8) were restored and sliced to obtain specimens (0.8 mm2) and they were tested at two different time intervals: immediately and after 6 months. The fracture mode was evaluated with a stereoscopic loupe (40×) and by scanning electron microscopy (SEM). The data were subjected to ANOVA and Tukey tests (a=0.05). NbG addition did not compromise the adhesive system DC values (p>0.05). Furthermore, the NbG added to the adhesive systems did not affect μTBS values (p>0.05). Fracture occurred predominantly at the dentin-adhesive interface. NbG bioactive glass did not affect the DC or microtensile bond strength results.

Effect of polyvinyl siloxane impression material on the polymerization of composite resin

Statement of problemPolyvinyl siloxane impression material has been widely used as a lingual matrix for rebuilding missing tooth structure with composite resin. The composite resin is light polymerized in contact with the polyvinyl siloxane impression material. However, polyvinyl siloxane impression material has been shown to interact with other dental materials. PurposeThe purpose of this study was to assess the effect of polyvinyl siloxane impression materials on the polymerization of composite resins by assessing the Vickers microhardness and degree of conversion of polyvinyl siloxane. Material and methodsThe composite resins were light polymerized in contact with 3 polyvinyl siloxane impression materials (Flexitime Easy Putty; President Light Body; Xantopren L Blue) (n=8) and in contact with a matrix strip as the control group (n=8). Vickers microhardness and degree of conversion on contact surfaces were measured to evaluate the polymerization of composite resins. The depth of the effect was assessed by Vickers microhardness on section surfaces and observed with scanning electron microscopy. The results were analyzed by 1-way analysis of variance and the post hoc Tukey honest significant differences test (α=.05). ResultsThe Vickers microhardness and degree of conversion values on the contact surfaces of the experiment groups were significantly lower than those of the control group (P<.05); the Vickers microhardness values on the section surfaces indicated that there was no significant difference at the same depth of different groups (P>.05). The scanning electron microscope observation showed that an approximately 10-μm deep unpolymerized layer was found in the experimental group. ConclusionsPolyvinyl siloxane impression materials have an inhibitory effect on the polymerization of the composite resins, but just limited to within approximately 10 μm from the surface in contact with the impression material.

Effect of self and dual-curing on degree of conversion and crosslink density of dual-cure core build-up materials

PurposeDual-cure core build-up resins have been developed to take advantages of both self and light-cured resin. The aim of present study was to determine the polymerization characteristics of self and dual-cured modes of dual-cure core build-up composites evaluating degree of conversion (DC) and crosslink density by measurement of glass-transition temperature (Tg) and hardness decrease in ethanol. MethodsClearfil Dc Core Automix (CLF) and Grandio Core Dc (GR) core build-up resins were selected. Twelve specimens for both composites were polymerized using quartz-halogen-tungsten light curing unit (QTH) and 12 specimens polymerized chemically. DC was determined by ATR-FTIR spectroscopy. TG/DTA analysis was performed to determine Tg. Microhardness value of specimens was determined by Vickers-tester before and after specimens stored in absolute ethanol for 24h. ResultsOne-way ANOVA showed no different DC values between dual and self-cured mode of GR and dual-cured CLF composites had higher DC than self-cured mode. Tg and percentage of softening in ethanol values of GR and CLF revealed significant difference between self and dual-cured mode. ConclusionsIn comparison of GR and CLF, DC showed no statistical difference in both curing modes. However, dual and self-cured GR has statistically higher Tg values and lower percentage of softening in ethanol than CLF. Polymerization characteristics of dual-cure core build-up composites have superiority in dual-cured mode than self-cured.