Cure width potential for MOD resin composite molar restorations

Most manufacturers do not provide details about the photoinitiators contained in dental adhesives. Therefore, it is difficult to choose an optimal combination of dental adhesive and light-curing unit. The purpose of this study was therefore to investigate the spectral emission characteristics of several commercially available light-curing units and the spectral transmittance characteristics of contemporary dental adhesives. Spectral distributions of emitted lights were determined on a UV-vis-NIR spectrometer for three quartz-tungsten-halogen (QTH) light-curing units (Jetlite 3000, J. Morita; New Light VL-2, GC; D-Lux 2000, Dentrade) and three light-emitting diode (LED) light-curing units (Curenos, Shofu; G-Light Prima, GC; Bluephase, Ivoclar Vivadent). Spectral distributions of light transmittance in contemporary dental adhesives (Scotchbond Multi-Purpose, 3M ESPE; Adper Single Bond, 3M ESPE; One-Step, Bisco; AQ Bond Plus, Sun Medical; OptiBond All-in-One, Kerr; Clearfil S3 Bond, Kuraray Medical; G-Bond, GC; Tokuyama Bond Force, Tokuyama Dental; GBA 300 experimental, GC) were also determined. Each of the three QTH light-curing units had a wide emission range of 380-510 nm. A narrower emission range was observed in the LED light-curing units than in the QTH light-curing units. It was found that 2 LED light-curing units had dual peak wavelengths in both the blue and violet regions of the visible spectrum. There were some variations in light transmittance, and therefore the results suggested that some dental adhesives contain alternative photoinitiators besides camphorquinone. The selection of suitable light-curing units on the basis of the light absorption of dental adhesives and resin composites in dental clinics is of upmost importance.

This study investigated the influence of battery charge levels on the stability of light-emitting diode (LED) curing-light intensity by measuring the intensity from fully charged through fully discharged batteries. The microhardness of resin composites polymerized by the light-curing units at various battery charge levels was measured. The light intensities of seven fully charged battery LED light-curing units-1) LY-A180, 2) Bluephase, 3) Woodpecker, 4) Demi Plus, 5) Saab II, 6) Elipar S10, and 7) MiniLED-were measured with a radiometer (Kerr) after every 10 uses (20 seconds per use) until the battery was discharged. Ten 2-mm-thick cylindrical specimens of A3 shade nanofilled resin composite (PREMISE, Kerr) were prepared per LED light-curing unit group. Each specimen was irradiated by the fully charged light-curing unit for 20 seconds. The LED light-curing units were then used until the battery charge fell to 50%. Specimens were prepared again as described above. This was repeated again when the light-curing units' battery charge fell to 25% and when the light intensity had decreased to 400 mW/cm2. The top/bottom surface Knoop hardness ratios of the specimens were determined. The microhardness data were analyzed by one-way analysis of variance with Tukey test at a significance level of 0.05. The Pearson correlation coefficient was used to determine significant correlations between surface hardness and light intensity. We found that the light intensities of the Bluephase, Demi Plus, and Elipar S10 units were stable. The intensity of the MiniLED unit decreased slightly; however, it remained above 400 mW/cm2. In contrast, the intensities of the LY-A180, Woodpecker, and Saab II units decreased below 400 mW/cm2. There was also a significant decrease in the surface microhardnesses of the resin composite specimens treated with MiniLED, LY-A180, Woodpecker, and Saab II. In conclusion, the light intensity of several LED light-curing units decreased as the battery was discharged, with a coincident reduction in the units' ability to polymerize resin composite. Therefore, the intensity of an LED light-curing unit should be evaluated during the life of its battery charge to ensure that sufficient light intensity is being generated.

To investigate the influence of the consistency of resin composite and insertion techniques on the homogeneity of the Class I restorations. Standardized Class I cavities were prepared in polymethyl methyacrylate (PMMA) blocks and restored with three resin composites (Prodigy, Tetric EvoCeram and Tetric Ceram HB) using either a packing or an injection technique by six operators. Then the restorations were sectioned longitudinally and inspected for the presence of porosities and voids with microscope. The consistence of the three resins was tested using an area method. There is little porosity in original resin. After insertion, large numbers of porosities were observed in restorations, with Tetric EvoCeram presented much more porosities (1137.1 +/- 365.0 for packing and 566.1 +/- 206.4 for injection) than Prodigy (241.0 +/- 116.1, 195.8 +/- 28.7) and Tetric Ceram HB (193.1 +/- 35.8, 156.3 +/- 33.0). Tetric Ceram HB showed the highest consistency, followed by Tetric EvoCeram and Prodigy. No linear correlation was found between the consistency of the composite and the porosity of their restorations. For Tetric EvoCeram, the restorations inserted with packing showed significant more porosity than that with injection. Contrastively, the restorations of Prodigy or Tetric Ceram HB presented no apparent difference for the two filling techniques. The porosity in restoration was primarily created during the insertion. There was no linear correlation between the consistency of the composite and the porosity of their restorations. The porosity of composite resin is material-brand dependent. The influence of filling techniques on the porosity of restoration is depending on the composite used.

The influence of storage and indenter load on the Knoop hardness of dental composites polymerized with LED and halogen technologies

The use of resin composites (RC) for complex restorations, including those involving cusp coverage, has increased dramatically in recent years. However, reports in the literature regarding the performance of posterior multisurface RC and amalgam (AM) restorations show conflicting results. This systematic review and meta-analysis aims to assess the clinical performance of complex (involving two or more surfaces) direct posterior resin composite and amalgam restorations in permanent teeth. Inclusion criteria were for prospective randomized controlled trials (RCTs) of multisurface direct RC and AM restorations of permanent posterior teeth with a follow-up period of three years or more. The trials needed to include a minimum of 20 restored teeth for each evaluated material. Retrospective studies, studies lacking survival rates or clearly reported reasons for failure, and those with unclear randomization methods were excluded. Five bibliographic databases (Medline-OVID, Embase, Cochrane Library, Web of Science, and LILACS [Latin American and Caribbean Health Sciences Literature Database]) and manual searches were screened. The Cochrane Risk of Bias Tool was used to assess the included studies. Random-effects meta-analyses were conducted using the Freeman-Tukey double arcsine transformation and the DerSimonian-Laird random-effects model to evaluate restorative failures and compare the survival of AM and RC restorations. From the 6303 identified studies, 198 underwent meticulous examination, and 15 RCTs met the inclusion criteria. Only two studies compared AM and RC restorations. Although the combined data from these studies showed a trend toward higher failure rates in multisurface RC restorations, the difference was not statistically significant (p=0.06). The most common reasons for the failure of RC restorations were secondary caries, restoration fracture, and tooth fracture. For AM, the most common reasons for failure were secondary caries and tooth fracture. The quality of the evidence was low. The scarcity of studies comparing RC and AM in complex restorations has resulted in insufficient evidence to substantiate superior performance by either material.

Objective:The aim of the study is to evaluate temperature change in fiber-reinforced composite (FRC) resin photopolymerized with a light-emitting diode (LED) light-curing unit (LCU).Materials and Methods:Forty dentine disks (1 mm thick and 8 mm diameter) were prepared from human molars. The FRC specimens (2 mm thickness and 8 mm diameter) consisted of polyethylene fiber (Construct (CT)) products or glass fiber (ever Stick (ES)) and one hybrid composite bonded to the dentin disks and polymerized with an LED LCU. Control groups were prepared using the hybrid composite. Temperature rise in dentine samples under the FRC bonded disks was measured using a K-type thermocouple, and data were recorded. Temperature change data were subjected to analysis of variance (ANOVA) and Duncan's test.Results:The results show that addition of fiber (one or two layers) did not change temperature rise values at any of the exposure times (P > 0.05). The CT fiber/two layer/40 s group exhibited the greatest temperature rise (5.49 ± 0.62) and the ES/one layer/10 s group the lowest rise (1.75 ± 0.32). A significant difference was observed in temperature rise measured during 10 and 20 s exposures (P < 0.05).Conclusion:Maximal temperature rise determined in all groups was not critical for pulpal health, although clinicians need to note temperature rises during polymerization.

The aim of the present study was to evaluate the effect of four different sandwich techniques on gingival microleakage of Class II direct composite resin restorations. Fifty sound human premolars were selected and randomly divided into five groups (n=10). Class II box only cavities were prepared in one of the proximal surfaces of each tooth with a gingival margin located approximately 0.5 mm below the cemento-enamel junction. Group A (control) was restored incrementally with composite resin (Tetric Ceram). Groups B, C, D, and E were restored with the sandwich technique using a compomer (Compoglass F), flowable composite resin (Tetric Flow), self-cure composite resin (Degufill SC), or resin modified glass ionomer (Fuji II LC), respectively. After thermal-load cycling, the specimens were immersed in 0.5% basic fuschin for 24 hours. Dye penetration (10(-1) mm) was detected using a sectioning technique. Data were analyzed with repeated measurements and Duncan test at α=0.05. The least amount of microleakage was detected in the incremental group (1.28 ± 0.98). The sandwich technique using resin modified glass ionomer (7.99 ± 9.57) or compomer (4.36 ± 1.78) resulted in significantly more leakage than did the sandwich technique using flowable (1.50 ± 1.97) or self-cure composite (2.26 ± 1.52). According to the results of this study, none of the four sandwich technique composite resin restorations used in this study could reduce gingival microleakage to a greater degree than the incremental technique.

Light-emitting diode (LED) polymerisation of dental composites: flexural properties and polymerisation potential

Ability of four dental radiometers to measure the light output from nine curing lights

Two-body abrasion of commercial and experimental restorative and coating resins and an amalgam

Interaction of LED light with coinitiator-containing composite resins: Effect of dual peaks

Second generation LEDs for the polymerization of oral biomaterials

The aim of this study was to investigate the influence of light curing method, composite shade, and depth of cure on composite microhardness. Forty-eight specimens with 4 mm of depth were prepared with a hybrid composite (Filtek Z-100, 3M ESPE); 24 with shade A1 and the remaining with shade C2. For each shade, two light curing units (LCUs) were used: a quartz-tungsten-halogen (QTH) LCU (Optilight Plus - Gnatus) and a light emitting diode (LED) LCU (LEC 470 II - MM Optics). The LED LCU was tested using two exposure times (LED 40 seconds and LED 60 seconds). After 24-hour storage, three indentations were made at mm depth intervals using a Knoop indenter. Data were submitted to three-way analysis of variance (ANOVA) and Tukey's test (p<0.05). The three factors tested (light curing method, shade, and depth) had a significant influence on the composite microhardness (p<0.05). All groups presented similar hardness values in the first mm, except for composite shade C2 cured with LED for 40 seconds. The hardness decreased with depth, especially for shade C2 for 40 seconds. Increasing light-curing time with LED produced hardness values similar to the QTH. The light curing method including variations of time, the depth of cure, and the composite shade influence the composite microhardness. Clinicians should avoid thicker increments when working with composite restorations. Extended light-curing time might be indicated depending on the composite shade and on the light-curing device.

Resin composites are the most commonly used restorative materials and are constantly evolving due to their shortcomings which can affect the restoration results in polymerization shrinkage, leading to the formation of microleakage. Although incremental techniques have been found, this technique has drawbacks regarding the time required and the possibility of contamination. The invention of bulk fill resin composite can solve this problem. Manufacturers of One-Bulkfill (3M ESPE) claim that this material has less polymerization shrinkage than conventional resin composites, which is expected to have less chance of microleakage. This study aims to determine the difference in microleakage between one-bulkfill resin composites and conventional resin composites. 20 extracted premolars without caries and anomalies were utilized as research samples. These teeth were then prepared to form a class 1 cavity, then divided into two groups, namely; (1) One-Bulkfill (3M ESPE) and (2) Z350 XT (3M ESPE). These two samples were immersed in 1% Methylene Blue solution and observed using a Camera with a Macro Lens. Data were analyzed using an independent sample t-test. The results demonstrated a significant difference in microleakage between the two groups (p = 0.014, p0.05). The mean value of microleakage in One-Bukfill composite resin restorations was 0.022, while Z350 XT composite resin restorations had 0.038. It can be concluded that the One-Bulkfill composite resin restoration had a smaller microleakage value than the conventional composite resin restoration (Z350 XT).

IntroductionColored compomers are a group of restorative materials that were introduced in 2002 to repair primary teeth, and they provide attractive color and ease of use in pediatric dentistry. The aim of this study was to evaluate the effect of QTH and LED light-curing units on the surface hardness of different colors of Twinky Star compomers.MethodsIn this experimental study, a composite resin (Z250, 3M, and USA), an ionosit compomer (DMG, Germany) with A3 shade and 8 different Twinky Star colored compomer (Voco, Germany) samples were used. In all, 100 samples were prepared with 10 samples in each group, i.e., 10 Z250 composite resin, 10 ionosit compomers, and 10 Twinky Star compomer samples of each color. The samples were prepared in a 4×4-mm Teflon mold. Half of the samples were light-cured with QTH and the other half with LED units. Then, the surface microhardness was measured by Vickers hardness test. The data were analyzed with IBM-SPSS version 22, using the t-test and ANOVA.ResultsTwo-way ANOVA showed that the mean surface hardness of the compomer samples cured with the QTH unit was significantly higher than that cured with the LED unit (p < 0.001). In each curing unit, surface hardness of some materials exhibited significant differences with the highest hardness being observed in the Z250 composite resin (650.35 ± 56.320) and the lowest hardness being detected in the ionosit compomers (461.10 ± 96.170). One-way ANOVA also showed that, among the different colors of the Twinky Star compomer, the lowest hardness with both units (QTH and LED) was observed in the gold color (214.32 ± 22.026 and 175.116 ± 15.918, respectively).ConclusionThe colored compomer and the type of light-curing unit affected the microhardnesses of the surfaces. Different colors of Twinky Star compomers exhibited different surface microhardnesses.