LED Curing Research Articles

Effect of Battery Level During Successive Charging Cycles on the Performance of Certified and Low-cost Uncertified Light-curing Units Available on E-commerce.

To evaluate the influence of battery level on power (mW), emission spectrum (mW/cm2/ nm), and light distribution on the active tip (mW/ cm2) of certified (FDA/ANVISA) and low-cost uncertified light-curing units (LCUs) purchased through e-commerce. Seven LCUs, three certified: VALO Grand (Ultradent); Radii Xpert (SDI); and LED.B (Woodpecker); and four uncertified: 1 Sec; BS 300; LED curing light; and VAFU (VRN, AZDENT), were used. The LCUs were evaluated by calculating the power (mW) after each sequential five exposure cycles of 20 seconds and the emission spectrum (mW/cm2/nm) in the initial and final cycles, using an integrating sphere during three battery charging cycles. Beam profiling was used to check the light distribution on the LCU tip after every 50 exposure cycles until the battery fully discharged. Data were analyzed by linear regression between power and the number of exposure times (R2). The certified LCUs VALO Grand (R2=0.005), LED.B (R2=0.02), and Radii Xpert (R2=0.09) and the uncertified LCU VAFU (R2=0.002) had no significant power reduction during the three battery charging cycles. The uncertified LCUs BS 300 (R2=0.87), 1 Sec (R2=0.60), and LED curing light (R2=0.83) showed significant power reduction, decreasing the emission spectrum (mW/cm2/nm) at the end of the battery charging cycle. The light distribution on the active tip across the level battery was modified significantly with successive exposure times. The certified LCUs (VALO Grand, Radii Xpert, and LED.B) and uncertified LCU (VAFU), maintained power, emission spectrum, and light distributions during the tested battery life cycles. Low-cost certified LCU LED.B exhibited inhomogeneous light concentrated at the center of the tip. Low-cost uncertified LCUs-BS 300, 1 Sec, and LED curing light-had significant power reductions during the battery cycles and increased inhomogeneous light distribution along the successive exposure times.

Impact of Battery Levels of a Cordless LED Curing Unit on Resin Cement under Varied Lithium Disilicate Thicknesses and Translucencies.

This study aimed to evaluate the impact of battery levels on the emission of a multi-peak cordless LED light-curing unit (LCU) and the effect on the degree of conversion (DC) and Knoop hardness (KH) of a light-cure resin luting agent activated through varying lithium disilicate (LiS2) ceramic thicknesses and translucencies. High and low translucency LiS2 discs (IPS e.max Press HT and LT, respectively; shade A1) with thickness of 0.5, 1.0, 1.5, and 2.0 mm were fabricated. Resin luting agent specimens (Variolink Esthetic LC) were prepared and cured using a Bluephase G2 LCU at different battery levels (100%, 50%, and 10%) through the LiS2 ceramics. The transmitted irradiance was evaluated using USB4000 MARC, while FTIR and a microhardness tester assessed DC and KH, respectively. After ensuring homoscedasticity, the data wee analyzed using analysis of variance and Tukey HSD test (α=0.05). The study found strong positive correlations between battery levels and irradiance, particularly with no ceramic interposition and through HT ceramics (R2=0.9471), although this correlation diminished with thicker HT (R2=0.7907) and LT ceramics (R2<0.2980). Both battery levels and ceramic thickness significantly influenced transmitted irradiance (p<0.0001), resulting in lower values with decreased battery levels and increased ceramic thicknesses (p<0.0001). LT ceramics showed lower transmittance than HT. DC was significantly affected by both battery levels and ceramic thicknesses, with generally lower DC values except for LT ceramics at a 10% battery level (p<0.0001). No significant differences in DC were observed between HT and LT translucencies (p=0.548). KH was higher in HT than LT ceramics at 100% and 50% battery levels, with thicker ceramics showing lower KH values at 10% battery level (p<0.0001). Conclusion: Reduced battery levels in cordless LED curing units significantly affect the irradiance, degree of conversion, and hardness of light-curable resin luting agents. Maintaining battery levels above 50% is recommended for optimal performance. Thicker and more opaque ceramics significantly impacted incident irradiance. However, preserving radiant energy could potentially mitigate these limitations.

Effects of light curing on silver diamine fluoride-treated carious lesions: A systematic review.

This systematic review aims to evaluate the potential benefits and underlying mechanisms of combining SDF with light curing, based on available studies. A systematic search of publications was conducted with the keywords "silver diamine fluoride" or "silver fluoride" and "dental light curing," "LED curing," "dental laser," and "dental polymerization" in 4 databases: PubMed, EBSCO, Scopus, and Google Scholar to identify English-language articles published up to March 2023. Duplicate publications were deleted. Two reviewers screened the titles and abstracts and excluded irrelevant publications. The full text of the remaining publications was retrieved. Studies investigating the effect of light-curing on SDF-treated carious lesions were included. The 175 publications initially found included 5 laboratory studies investigating the effects of light curing on 38% SDF-treated dentine carious lesions, but no clinical study was found. Four of these studies were conducted on extracted primary teeth, and one was on extracted permanent teeth. SDF with light curing increased microhardness (n = 3, p < .05) showed a higher mineral density (n = 1, p < .041) and had more silver ion precipitation in infected dentine (n = 1, p < .016) compared to SDF without light curing. Moreover, no significant differences in the antibacterial activity were observed between SDF with light curing and SDF alone (n = 1, p > .05). Drawing from the limited number of laboratory studies, incorporating light curing subsequent to the SDF application yields potential favorable outcomes that include augmented microhardness, elevated mineral density, and heightened silver ion precipitation within infected dentine. Future clinical research is required to confirm or refute the benefit of light curing on SDF-treated carious lesions.

Influence of Layer Thickness and Shade on the Transmission of Light through Contemporary Resin Composites.

Material-dependent parameters have an important impact on the efficiency of light polymerization. The present in vitro study aimed to investigate the influence of the increment thickness and shade of nano- and nanohybrid resin composites on the transmission of curing light. Three contemporary resin composites were evaluated: Tetric EvoCeram® (TEC); Venus Diamond® (VD); and Filtek Supreme XTE® (FS XTE). Light transmission (LT) was recorded in accordance with the sample thickness (0.5 to 2.7 mm) and the shade. Polymerized samples were irradiated for 10 s each using the high-power LED curing light Celalux 2 (1900 mW/cm2). LT was simultaneously recorded using the MARC Patient Simulator (MARC-PS). LT was strongly influenced by the composite layer thickness. For 0.5 mm-thick samples, a mean power density of 735 mW/cm2 was recorded at the bottom side. For the 2.7 mm samples, a mean power density of 107 mW/cm2 was measured. Only LT was markedly reduced in the case of darker shades. From A1 to A4, LT decreased by 39.3% for FS XTE and 50.8% for TEC. Dentin shades of FS XTE and TEC (A2, A4) showed the lowest LT. The thickness and shade of resin composite increments strongly influences the transmission of curing light. More precise information about these parameters should be included in the manufacture manual.

Effect of duration and infection control barriers of light curing unit on hardness of Bulk Fill composite resin.

This study aimed to investigate the impact of the duration of light curing unit (LCU) usage and the use of infection control barriers on the hardness of Bulk Fill composite resin after curing. The hypotheses were that extended usage of the LCU would not reduces its output power and resin hardness, and that the presence of polyethylene film barriers exacerbates the reduction in resin hardness. Based on the absence or presence of polyethylene film (PE) and the number of layers used, a 3M LED curing light (EliparTM DeepCure-S; 3M ESPE, St Paul, MN, USA) was divided into three groups: PE0, PE1, and PE3. The curing light was used 30 times daily for 20 s per exposure, at frequencies of 0, 6, and 12 months. Maximum output power tests were conducted for each group of curing lights. Custom-made plastic modules were used to stack Bulk Fill composite resin (Filtek Bulk Fill Posterior Restorative; 3M ESPE) to a thickness of 4 mm. Each group of curing lights was used to cure the modules in a direct contact manner for 20 s. Vickers hardness measurements were taken at the top and bottom surfaces of the resin specimens using a digital microhardness tester. A one-way or two-way ANOVA analyzed the power of LCUs, Vickers hardness of Bulk Fill composite resin, and hardness decrease percentage across groups. Pairwise comparisons used the Tukey test (α = 0.05). As the duration of usage increased, both the power of the curing light and the hardness of the resin significantly decreased. Significant differences were observed in power and resin hardness among the PE0, PE1, and PE3 groups. When the duration of usage was 6 months or less, only multi-layered PE films led to a significant increase in the percentage decrease of hardness of cured resin from top to bottom. However, at 12 months, both single-layer and multi-layered PE films resulted in a significant increase in the percentage decrease of hardness of cured resin from top to bottom. The output power of the light curing unit decreases with prolonged usage, thereby failing to meet the curing requirements of Bulk Fill composite resin. The use of single-layer PE as an infection control barrier is recommended.

Antimicrobial photodynamic therapy against Lactobacillus casei using curcumin, nano-curcumin, or erythrosine and a dental LED curing device.

This study aimed to investigate the photodynamic effects of curcumin, nanomicelle curcumin, and erythrosine onLactobacillus casei (L. casei). Various concentrations of curcumin (1.5g/L, 3g/L), nano-curcumin (3g/L), and erythrosine (100µM/L, 250µM/L) were tested either alone or combined with light irradiation (PDT effect) against L. casei in planktonic and biofilm cultures. The light was emitted from a light-emitting diode (LED) with a central wavelength of 450 nm. A 0.12% chlorhexidine digluconate (CHX) solution served as the positive control, and a solution containing neither photosensitizer nor light was the negative control group. The number of viable microorganisms was determined using serial dilution. There was a significant difference in the viability of L. casei in both planktonic and biofilm forms (P < 0.05). In the planktonic culture, the antibacterial effects of CHX and PDT groups with curcumin 3 g/L and erythrosine 250 µM/L were significantly greater than the other groups (P < 0.05). For L. casei biofilms, the greatest toxic effects were observed in CHX and PDT groups with curcumin 3g/L, erythrosine 250 µmol/L, erythrosine 100 µmol/L, and nanomicelle curcumin 3g/L, with a significant difference to other groups (P < 0.05). The antibacterial effects of all photosensitizers (except erythrosine 250 µmol/L at planktonic culture) enhanced significantly when combined with light irradiation (P < 0.05). PDT with curcumin 3g/L or erythrosine 250µmol/L produced comparable results to CHX against L. caseiat both planktonic and biofilm cultures. Alternatively, PDT with erythrosine 100µmol/L or nanomicelle curcumin 3g/L could be suggested to kill L. casei biofilms.

A comparison of the shear bond strength of metal orthodontic brackets that have been treated with various light-emitting diode intensities and curing times: In-vitro research

The study aims to test the effects of LED light at three different power settings (500mW/cm2, 1000mW/cm2&amp; 1500m W/cm2) and three different exposure times (5sec, 10sec &amp; 20sec) adhesive composites for use with stainless steel orthodontic brackets, and their shear bond strengths. Current In-vitro work used 120 teeth, mostly premolars, separated into 10 equal groups of 12. After the crowns of the teeth were exposed by mounting them vertically into self-heal acrylics, the buccal-enamel exterior was prepared for bonding (PEA) 0.022”x 0.028” stainless steel premolar bracket using a thin layer of light cure adhesive primer and paste (Transbond-XT-3M Unitek Monrovia, Calif). Brackets in Group 1 comprising the Control group treated by usual halogen light source for forty sec, in remaining 9 groups (Experimental group) three commercially available LED curing light units i.e., Woodpecker, Guilin, Guangxi, China; Stealth Soft Equinox, Denmark, Holland; Radii plus, SDI, Australia, having three different light intensity 500mW/cm2, 1000mW/cm2, 1500mW/cm2 respectively were used to bond the brackets at three contact time (5/10/20 sec). The universal testing equipment was used to determine the shear bond strength of each specimen. The uppermost average SBS was found in the group cured with LED of intensity 1500 mW/cm2 for 20 sec (20.08 + 4.82 MPa) which was statistically significant compared the to control group (12.72 + 2.42 MPa). The lowest mean SBS values were obtained for groups cured with LED of intensity 500 mW/cm2 even at different curing times of 5, 10 and 20 sec i.e., 5.46 + 1.99 MPa, 8.77 + 2.38 Mpa and 11.24 + 2.59 MPa, respectively. Increasing the intensity of the LED light curing unit provides a clinically acceptable SBS even after reducing the curing times, thereby reducing the chairside time for bonding of orthodontic brackets.The study aims to test the effects of LED light at three different power settings (500mW/cm2, 1000mW/cm2&amp; 1500m W/cm2) and three different exposure times (5sec, 10sec &amp; 20sec) adhesive composites for use with stainless steel orthodontic brackets, and their shear bond strengths. Current In-vitro work used 120 teeth, mostly premolars, separated into 10 equal groups of 12. After the crowns of the teeth were exposed by mounting them vertically into self-heal acrylics, the buccal-enamel exterior was prepared for bonding (PEA) 0.022”x 0.028” stainless steel premolar bracket using a thin layer of light cure adhesive primer and paste (Transbond-XT-3M Unitek Monrovia, Calif). Brackets in Group 1 comprising the Control group treated by usual halogen light source for forty sec, in remaining 9 groups (Experimental group) three commercially available LED curing light units i.e., Woodpecker, Guilin, Guangxi, China; Stealth Soft Equinox, Denmark, Holland; Radii plus, SDI, Australia, having three different light intensity 500mW/cm2, 1000mW/cm2, 1500mW/cm2 respectively were used to bond the brackets at three contact time (5/10/20 sec). The universal testing equipment was used to determine the shear bond strength of each specimen. The uppermost average SBS was found in the group cured with LED of intensity 1500 mW/cm2 for 20 sec (20.08 + 4.82 MPa) which was statistically significant compared the to control group (12.72 + 2.42 MPa). The lowest mean SBS values were obtained for groups cured with LED of intensity 500 mW/cm2 even at different curing times of 5, 10 and 20 sec i.e., 5.46 + 1.99 MPa, 8.77 + 2.38 Mpa and 11.24 + 2.59 MPa, respectively. Increasing the intensity of the LED light curing unit provides a clinically acceptable SBS even after reducing the curing times, thereby reducing the chairside time for bonding of orthodontic brackets.

A New Material For Detecting Submerged Implants: An Animal Experiment

Objective: There are difficulties in determining the location of submerged implants when cover screws and healing screws are to be replaced. Because of this, a new implant cover screw has been designed. The purpose of this study was to investigate the properties of a novel implant cover screws in rabbits.&#x0D; Methods: 10 New Zealand White rabbits were randomly divided into two groups. Diastema regions behind the incisor teeth were used for the placement of cover screws. In the control group, the screws (n=20) that received no processing were placed whereas, in the experimental group, the screws (n=20) that top surfaces were coated with europium and dysprosium doped strontium aluminate were placed to the diastema regions. Animals were sacrificed after 6 weeks. Dental LED curing light was applied to the oral mucosa regions in which screws were placed in the experimental group just after sacrification and the visibility of the screws was evaluated. To determine the biocompatibility of the coated screws, oral mucosas which contacted with the screws, livers and kidneys were removed and examined histopathologically.&#x0D; Results: After light application, only the screws in the upper jaws of the experimental group became visible (n=10). Histopathological examinations performed on the kidneys, livers and oral mucosa tissues which contacted with the screws. There were no significant differences between the experimental and control groups regarding these tissues.&#x0D; Conclusion: According to the results of this study, it can be concluded that the titanium implant cover screws coated with europium and dysprosium doped strontium aluminate were biocompatible for rabbits.

Effect of Two Different Ultrafast Curing Exposure Durations on the Surface Hardness of Bulk Fill Composite - An In-Vitro Study.

The aim of the present study is to assess the microhardness of resin-based composites (RBCs) cured with ultrafast curing mode at two different exposure durations. This is an experimental in-vitro study. Forty-five cylindrical composite specimens were prepared to a dimension of 5 mm height and 4 mm diameter. Curing was done using three different exposure modes and duration with dual mode LED curing light as follows: Group I: Ultrafast curing mode for 1 second at 2300 mW/cm2 (n = 15); Group II: Ultrafast curing mode for 3 second at 2300 mW/cm2 (n = 15) and Group III: Standard exposure mode for 20 second at 1000 mW/cm2 (n = 15). Vicker's microhardness measurement was done on both the curing and non-curing sides of the specimen using a motorised diamond-faced micro-indenter (Wilson Wolpwert, Germany) using a load of 50 gram and a dwell time of 30 second. Kruskal Wallis ANOVA was used to test for difference between the three groups followed by Mann-Whitney U test for post-hoc analysis. The microhardness values of the composite cured with a conventional curing unit were significantly higher than the ultrafast cured specimens. Low-intensity conventional curing lights were found to perform better than the high-intensity ultrafast curing units.

Color Stability Assessment of Three Different Resin Composites After Polymerization with Two Different Light-Curing Units

Purpose: Despite improvements in resin composite structures, color stability remains a challenge, and esthetic problems are the most common factors in renewing restorations. This study aimed to evaluate the effects of two light-curing units on the color stability of three different resin composite materials during a six-month period.&#x0D; Materials &amp; Methods: Three different resin composites (Filtek Z550, Filtek Ultimate Flowable, Filtek Bulk Fill Restorative) with an A2 color shade were prepared for each combination of resin composite-curing unit (5x2mm) for a total of 30 specimens. Specimens were cured with either QTH Hilux Ultraplus (700mW/cm2) for 40 seconds or Radii Plus LED Curing Light (1400mW/cm2) for 20 seconds. For standardization of the amount of transmitted energy to the composite, all specimens received 28J/cm2. Color parameters were measured with a colorimeter (Minolta CR-321, Konica Minolta Sensing Pte Ltd, Singapore) after polymerization and at 24 hours, first week, first month, third month, and sixth month. Color changes(∆E) were calculated for the different storage periods. One-factor repeated three-way analysis of variance (ANOVA) was used to examine the changes in ΔE measurements over time for different fillers and devices.&#x0D; Results: Significant differences between composites and periods were observed in the color stability with polymerization either QTH or LED. Independently of the composites, there was no significant difference at the end of six months between QTH and LED units with a fixed energy density. The Filtek Z550 material showed the smallest and the Filtek Ultimate Flowable material showed the highest ∆E values at the end of the six months among the materials used.&#x0D; Conclusion: Clinically acceptable color changes were observed for all the materials at the end of six months.

Effect of additional polymerization process on color change in composite resins hold in different solutions

Aims: In this study, it was aimed to compare the amount of coloration of composite resins with different filler content by keeping them in various coloring solutions after standard and additional polymerization processes. Methods: Three types of composite resins with different contents were used in our study: Filtek?? Z250 (3M ESPE), G-aenial Anterior (GC) and Neo Spectra?? ST HV (Dentsply Sirona). A total of 240 composite resin samples were prepared, 10 (n:10) for each group, using molds with a depth of 2 mm and a diameter of 8 mm. The polymerization of the samples was carried out for 20 seconds using a LED curing device (Woodpecker Led-G, China). After finishing and polishing was done with Super-Snap (Shofu, JAPAN) finishing discs, additional polymerization was performed on half of the samples. Then, all samples were kept in distilled water for 24 hours at 37°C in an oven (Microtest MST 55, Ostim Ankara). The first color measurement of the samples extracted from distilled water was made with a spectrophotometer device [VITA Easyshade V (Vita Zahnfabrik, Bad Sackingen, Germany)]. After the first measurement, the samples placed in 100-mesh plastic containers were placed on bags of tea (Lipton, Rize, Turkey), filtered coffee (Nescafe Classic, Nestle, Turkey), mouthwash containing chlorhexidine (Kloroben mouthwash, Drogsan, Ankara, Turkey) and red wine (Buzbağ). Classic, Öküzgözü-Boğazkere, 2021 Elazığ, Turkey) was added. One week later, the samples were removed from the vacuum furnace, washed in distilled water, and the second measurements were made. Results: A statistically significant difference was found between the coloration values caused by the solution groups (p&lt;0.05). It was observed that the solution causing the most color change was wine, followed by coffee and tea, respectively. Although there was no statistically significant difference between the coloration values caused by the composite groups (p&gt;0.05), it was determined that the composite resin material with the lowest color change was the microhybrid-based Filtek?? Z250. Although there was no statistically significant difference between the coloration values caused by standard and additional polymerization (p&gt;0.05), it was determined that the additional polymerization process affected the color change amount of the materials positively. Conclusion: According to the findings of this study; Among the coloring solutions used, it was observed that the solution causing the most coloration in composite resins was red wine, followed by coffee, tea and mouthwash containing chlorhexidine, respectively. However, it was concluded that the addition polymerization process reduces the coloration of the composite resins.

Release of Monomers from Dental Composite Materials into Saliva and the Possibility of Reducing the Toxic Risk for the Patient.

Background and Objectives: The objective of this study was (1) to measure the amount of monomers released into the saliva depending on the time elapsed after the hardening of the composite and on the type of monomer used; and (2) with the prolongation of the light-curing procedure, to publish information on whether it would be possible to influence the level of leached monomers. Materials and Methods: HPLC technique was used to monitor the levels of the unpolymerized monomers Bis-GMA, Bis/EMA, TEGDMA, and UDMA from the four commonly used composite materials, released into the saliva of a volunteer with intact dentition. The levels were monitored in 3 time periods during 24 h after composite hardening. From every composite material, 4 samples were formed and cured with an LED lamp for 10 s, 20 s, 40 s, and 60 s. After the light curing, the same polishing procedure was used and the samples were leached in blank saliva samples. Results: We observed that every monitored composite material eluted monomers into the saliva after its application. The amount of monomers depended on the time elapsed after the curing of the composite and on the type of composite used. A 40 s LED curing procedure can reduce the amount of leached monomers in comparison with the standard 20 s procedure, especially for monomers of higher molecular weight. Conclusions: Our study confirmed the hypothesis that the release of monomers gradually decreases with increasing time after the hardening of the composite filling.

Transmission of radiant light energy through the sides of fiber posts.

Resin cements are light polymerized, but the light may not reach all areas of root canals. The purpose of this study was to determine the best predictor of transmitted light radiant exposure (TLRE) from posts' sides. Fiber posts were placed in a custom-made apparatus and advanced by 1-mm increments. The LED curing probe tip was activated for 40 s on the coronal end of the post. The TLRE was measured with an LED radiometer detector positioned on the side of the post exposed by an opening in the apparatus. Hierarchical multiple linear regression analysis was performed. Post system explained an additional 23.62% of the variation in TRLE. Adding actual post diameter explained an additional 62.64% of the variation in TRLE. While adding post length explained an additional 0.67%. Changing post system from FiberKleer to Postec Plus will decrease the mean value of TRLE by 4.90 units on average. Also, a one-unit increase of actual post diameter and length will decrease the value of TRLE by 44.96 and 0.44 units respectively. The TLRE ranged from 46 to 290 mJ/cm2 , which was between 0.73% and 6.63% of the original emanating light. The changes in post system, posts' diameter and length can be used to predict the unit changes in TLRE on the side of a translucent fiber post. Emanating radiant exposure from the side of the post was lower than 6.63% of the exposure entering the post. Fiber post diameter and length and post system can influence light radiant exposure transmitted from posts' sides, transmitting minimal radiant exposure, which can be increased by increasing curing duration.

Detection of Leachable Components from Conventional and Dental Bulk-Fill Resin Composites (High and Low Viscosity) Using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) Method.

The aim of this study was to investigate leachable components (monomers) in high and low viscosity dental bulk-fill resin composites and conventional resin composite materials after polymerization. Six bulk-fill and six conventional dental resin composite materials were used in this study. The samples of each material (three sets of triplicates) were cured for 20 s with irradiance of 1200 mW/cm2 with a LED curing unit and immersed in a 75% ethanol solution at 37 °C. The eluates from each triplicate set were analyzed after 24 h, 7 days or 28 days using liquid chromatography coupled with triple quadrupole tandem mass spectrometry (LC-MS/MS). Detectable amounts of 2-Hydroxyethyl methacrylate (HEMA) were found in both Gradia materials and the amount observed across different time points was statistically different (p ˂ 0.05), with the amount in solution increasing for Gradia and decreasing for Gradia Direct flo. Bisphenol A diglycidildimethacrylate (BIS GMA) was found in Filtek and Tetric materials. Triethylene glycol dimethacrylate (TEGDMA) was detected in all materials. On the other hand, there were no statistically significant differences in the amounts of TEGDMA detected across different time points in either of the tested materials. Monomers HEMA, TEGDMA, 4-dimethylaminobenzoic acid ethyl ester (DMA BEE) and BIS GMA in bulk-fill and conventional composites (high and low viscosity) can be eluted after polymerization. The good selection of composite material and proper handling, the following of the manufacturer's instructions for polymerization and the use of finishing and polishing procedures may reduce the elution of the unpolymerized monomers> responsible for the possible allergic and genotoxic potential of dental resin composites.

Comparison of shear bond strength of bonded stainless steel brackets using three different light curing systems: An in vitro study.

To evaluate and compare the shear bond strength of stainless-steel brackets using three different light curing units. Using three LED curing units (3M ESPE Elipar, Ivoclar bluephase, and Woodpecker I LED light cure), 120 precoated metal brackets (Gemini series, 3M Unitek) were cured. The shear bond strength was recorded using a universal testing machine. The shear strength of the bracket in different light-curing systems was examined with ANOVA test. The mean shear strength of group A, group B, and group C were 16.03 ± 14.30 MPA, 16.86 ± 11.89 MPA, and 20.51 ± 19.40, respectively. The result of the analysis shows that there is a major difference in shear bond strength of these three different light-curing systems with F value = 3.94 and P value 0.04. We used three LED light-curing units with different intensities and manufacturing companies. The result showed that woodpecker I LED light had significantly highest mean SBS than the other two (Elipar LED curing light and 3M ESPE, Ivoclar bluephase).

The effect of light curing time and intensity on the bond strength and fracture resistance of orthodontic adhesive.

This study aimed to measure the shear bond strength and compressive strength of orthodontic adhesives at different curing times and intensities. Ninety extracted human premolars were used. Orthodontic brackets were bonded on the buccal surface of the teeth with orthodontic adhesive light-cured using VRN-VAFU LED curing light at different curing times (1, 3 and 5 seconds) and intensities (1000, 1600 and 2300 mW/cm2 ). A universal testing machine was used to measure the shear bond strength. The ratio of the adhesive remnant and compressive strength of the orthodontic adhesive, at each curing time at the different intensities, were also evaluated. The results were statistically analyzed using one-way analysis of variance followed by Tukey's test. The lowest bond strength values (6.4, 9.9 and 12.6 MPa) were recorded with 1000 mW/ cm2 intensity (at all curing times) in comparison with the other intensities (P<0.05). Increasing the curing time significantly increased the bond strength of the orthodontic brackets (P<0.05), except when the curing time was increased from 3 sec to 5 sec at 1600 mW/cm2 intensity. The highest compressive strength values (130.3, 147.1 and 174 MPa) were recorded at 2300 mW/ cm2 intensity (at all curing times) compared to the other intensities (P<0.05). The highest values of the ratio of the adhesive remnants were recorded at 1000 mW/cm2 intensity (at all curing times) compared to the other intensities (P<0.05). Although, increasing the curing time and\or the curing intensity has a positive effect on the bond strength and compressive strength of the orthodontic adhesive, it might be possible to suggest reducing the curing time of orthodontic adhesive to 1 sec at curing intensity of 2300 mW/cm2.

Shear bond strength of composite to demineralized enamel conditioned with resin infiltration

Aim: The aim of this in vitro study was to evaluate the influence of resin infiltration on bond-strength of composite resin to demineralized enamel. Methodology: Thirty bovine incisors were used in this study. Buccal enamel surfaces of bovine incisors were wet polished and then were divided into three groups: sound enamel; demineralized enamel; demineralized enamel infiltrated with a low-viscosity resin (ICON, DMG, Hamburg, Germany). After acid-etching with 37% phosphoric acid for 20 seconds, a two-step, total-etch adhesive (Single Bond 2, 3M ESPE, St. Paul, MN, USA) was applied using a microbrush for 20 seconds, followed by gentle air-drying for 5 seconds. The adhesive was light-cured for 10 seconds. Following the adhesive application, flowable composite resin (Filtek Supreme Flowable, 3M ESPE, St. Paul, MN, USA) was gently placed into a microtubule and was photopolymerized using an LED curing unit (Elipar Deep Cure; 3M ESPE, St. Paul, MN, USA). The microshear bond strength (µSBS) tests were performed using a microshear testing machine at a cross-head speed of 0.5 mm/min. One-way ANOVA and Bonferroni tests were used to analyze the data (5%). Results: Significant differences were found according to the ANOVA (p &lt; 0.05). Pair-wise comparison results of µSBS (mean ± SD) were: sound enamel (25.16 ± 2.3); demineralized enamel (17.93 ± 2.1); demineralized enamel infiltrated with a low-viscosity resin (28.51 ± 3.76). Conclusion: Resin infiltration applied to demineralized enamel before composite application increased the bond strength. No difference was found in the bond strength values obtained for sound enamel and resin infiltrated enamel. How to cite this article: Durukan SM, Gümüştaş B, Şişmanoğlu S. Shear bond strength of composite to demineralized enamel conditioned with resin infiltration. Int Dent Res 2022;12(Suppl.1):114-19. https://doi.org/10.5577/intdentres.441 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Noninvasive Adaptation Appraisal of Antimicrobial Nano-Filled Composite

The aim of this research was to assess the effect of incorporating zein-coated magnesium oxide (zMgO) nanofillers to resin-based composite on the internal adaptation of the restorations using cross-polarisation optical coherence tomography (CP-OCT). Thirty noncarious human molar teeth were used. Class V cavities (3×5 mm) were prepared on the buccal and lingual surfaces of each tooth. Clearfil SE Bond 2 was applied to all the cavities and then the teeth were divided into 3 groups (n=10) as follows: group 1-restored with N-Flow composite; group 2 and group 3-restored with N-Flow composite mixed with different zMgO nanoparticle concentrations (0.3% and 0.5% by weight, respectively) and then light cured using an LED curing device. Specimens were examined for interfacial adaptation examination under CP-OCT. Characterisation of the dental composite incorporating zMgO was done by Fourier-transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). Results were analysed with Kruskall-Wallis test followed by Mann-Whitney U test, at a significance level of P < .05. XRD spectra exhibited the sharp peaks of zMgO in the composite enhanced with zMgO nanoparticles. FESEM analysis showed a uniform distribution of the zMgO nanoparticles in the composite and FTIR illustrated no change in the spectra. The gap percentage along the cavity floor was significantly lower in groups 2 and 3 in comparison to group 1 (P < .05). Also there was a significant difference in gap percentages between groups 2 and 3 (P < .05), with group 3 showing the lowest gap percentage. The incorporation of 0.3% and 0.5% zMgO nanoparticles in flowable composite assists in improving the internal adaptation of the composite to the tooth surface.

Fast Curing with High-power Curing Lights Affects Depth of Cure and Post-gel Shrinkage and Increases Temperature in Bulk-fill Composites.

High-power LED curing lights and bulk-fill resin composites are intended to reduce chair time. This study investigated depth of cure, post-gel shrinkage (responsible for shrinkage stress), and heat generation in bulk-fill composites when cured according to minimum curing times recommended by manufacturers of curing lights and composites. A regular LED curing light (Demi Ultra, 1350 mW/cm2, Kerr Dental) and two LED curing lights with high-power modes (VALO Grand, 3117 mW/cm2 Xtra Power, Ultradent; and Bluephase PowerCure, 2435 mW/cm2 Turbo and 3344 mW/cm2 3sCure, Ivoclar Vivadent) were tested on three bulk-fill composites (Filtek One Bulk Fill, 3M Oral Care Solutions; Tetric EvoCeram Bulk Fill, Ivoclar Vivadent; Tetric Powerfill, Ivoclar Vivadent). Using minimum times recommended by manufacturers (3, 5, 6, 10, or 20 seconds), depth of cure was determined by Vickers hardness of specimens cured in a slot (n=10). Post-gel polymerization shrinkage was measured using a strain gauge (n=10) and temperature with a thermocouple (n=5). Results were analyzed using two- and one-way analysis of variance (ANOVA) followed by pairwise comparisons or Student-Newman-Keuls post hoc tests (α=0.05). Curing lights and curing protocols significantly affected depth of cure, post-gel shrinkage, and temperature rise (p<0.001). Cure decreased with depth whereby best overall curing performance was achieved by the 20 second exposure at lowest irradiance (Demi Ultra). Fast curing (3-5 seconds) at high irradiance resulted in lesser depth-of-cure performance, except for the BluePhase-Tetric PowerFill combination. Post-gel shrinkage was higher in all composites when cured at high irradiance (p<0.001), while heat generated also tended to be higher. Although the high-power LED curing lights advertise time savings, not all manufacturer recommended minimum curing times cured bulk-fill materials to the same extent. Moreover, these time savings came at a cost of higher post-gel shrinkage and generated more heat in the bulk-fill composites than the lower irradiance curing protocol.

Effect of radiant emittance of an LED curing light on the cuspal deflection of a simulated tooth cavity in bulk-fill composite restoration: A novel simulation method.

In this study, a novel method for simulating human teeth was developed, with which the effect of radiant emittance of an LED curing light on the cuspal deflection was investigated. A mesio-occluso-distal (MOD) cavity was replicated using a heat-pressed ceramic and lost wax technique, and the cuspal compliance and cuspal deflection of the replicated ceramic teeth and extracted human teeth were evaluated. The replicated ceramic teeth were restored using a nano bulk-fill composite and photopolymerized using three different protocols. Data were analyzed with t-test and one-way ANOVA (α=0.05). The cuspal compliance and cuspal deflection of the replicated ceramic teeth and extracted human teeth were similar. Cuspal deflections did not differ significantly among the tested photopolymerization protocols. Thus, the replicated ceramic teeth were an effective simulation of human teeth. During bulk-fill composite restoration of the MOD cavity, cuspal deflection was not affected by changing the radiant emittance of the LED light.