Flowable Resin Research Articles

Influence of different tooth preparation and bonding techniques on the fracture resistance of tooth fragment reattachment

Purpose comparing the influence of different tooth preparation and bonding techniques on the fracture resistance of tooth fragment reattachment. Materials and method Ninety bovine central incisors were selected. Fifteen teeth act as a control (Group A). Experimental specimens were sectioned at the mesial-incisal proximal edge 3 mm from the incisal edge in a labio-lingual direction at 25degree inclination apically. Experimental specimens were then divided into five groups according to the tooth reattachment techniques utilized; Group B: no tooth preparation + Cured bond + Flowable composite; Group C: no tooth preparation + Uncured bond + Flowable composite; Group D: Bevel + bond + Flowable composite; Group E: Over-contouring + bond + Nanohybrid composite; Group F: Over-contouring + bond + Flowable composite. Specimens were subjected to thermocycling between 5 °C and 55 °C for 500 cycles with 30 sec. dwell time. Fracture strength was evaluated using universal testing machine. Data was analyzed using One-way ANOVA. Results There was a statistically significant difference between Group A and all the experimental groups, p < .001. Group E showed the highest statistically significant fracture resistance mean value compared to other experimental groups, while the lowest mean value was found in Group B. Conclusion Though, none of the tested techniques resulted in fracture resistance similar to that of intact teeth, over-contouring technique with nanohybrid composite application showed better performances compared to the other techniques tested in the current study. Bonding plus flowable resin composite application with no additional tooth preparation and placement of a bevel are not suggested due to the low fracture strength achieved.

Comparative evaluation of Rheological characteristics of Giomers and other Nano-flowable resin composites in vitro

Objective The purpose of this research was to determine the viscoelastic properties of a group of commercially available nano-flowable resin composites; and to explore the relation between these properties and the materials’ composition (with/without fluoride), filler size description (nano-filled, nanohybrid and submicron-filled) and filler loading (by volume). Methods Rheological measurements were performed using a rheometer. A Dynamic frequency sweep test was conducted to evaluate the complex viscosity, storage and loss moduli, loss tangent, and complex shear modulus at an angular frequency (ω) of 0.1–100 rad/s. Comparative evaluations of the nano flowable resin composites on rheological properties was performed, and statistically analyzed using one-way ANOVA. Results The results indicated that all the tested materials exhibited shear-thinning flow behaviour. As the shear rate increased, the complex viscosity of the nano-flowable composites decreased. The nanohybrid filled flowable resin composites exhibited the highest complex viscosity, while the nano-filled flowable resin composites exhibited the lowest value. The submicron-filled materials exhibited the lowest complex shear moduli and loss tangent values. Conclusions: The findings from the current study provided comprehensive evaluation of the rheological properties of different nano-flowable composites. The observed differences in rheological properties among the tested materials were independent of their fluoride content or filler size. Furthermore, no relationship was found between the complex viscosity of the tested nano-flowable resin composites and their filler volume.

Creating Antibacterial Properties in Flowable Dental Composites by Incorporation of 3,4-dihydropyrimidin-2(1H)-ones

Objective: To investigate the antibacterial, mechanical, physical properties and water sorption of flowable dental composites containing 3,4-dihydropyrimidin-2(1H)-ones. Material and Methods: 3,4-dihydropyrimidin-2(1H)-ones was synthesized and the antibacterial activity of flowable dental composites containing 0-5 wt% 3,4-dihydropyrimidin-2(1H)-ones and also of their mechanical and physical properties on flowable dental composites were investigated. Flexural strength was measured by a three-point bending test. Compressive strength (CS), Water sorption (WS) and depth of cure (DOC) were investigated. The data were analyzed by One-way ANOVA test. The level of significance was determined as p<0.01. Results: The direct contact test demonstrates that by increasing the 3,4-dihydropyrimidin-2(1H)-ones content, the bacterial growth is significantly diminished (p<0.001). The average flexural strength results show that with increasing 3,4-dihydropyrimidin-2(1H)-ones until 3% in the composite, no significant difference was observed in flexural strength (p>0.001) and the mean of compressive strength results show no significant difference between 0-4% groups (p>0.001). The mean of water sorption and depth of cure results shows no significant difference between groups (p>0.001). Conclusion: Incorporation of 3,4-dihydropyrimidin-2(1H)-ones into flowable resin composites in 3% wt can reduce the activity of Streptococcus mutans.

REPAIR DURABILITY OF A WATER-AGED MICROFINE HYBRID RESTORATIVE RESIN COMPOSITE: A NANO-LEAKAGE STUDY

To evaluate the effect of two types of flowable composites and storage time on nano-leakage of repaired water aged resin composite. In total, 30 resin composite discs were prepared and stored in distilled water for 6 m. The discs were divided into 6 groups (n=5/group) according to the two experimental factors: Factor 1: Flowable composite, 3 groups (no-flowable, high-viscosity and low-viscosity flowable composites), and Factor 2; Storage time after repair, 2 groups (24 h and 6 m). Repair procedures were carried out using universal adhesive with and without the application of the flowable composite. After repair, half of the specimens were stored for 24 h and the other half were stored for 6 m in distilled water. After storage, each disc was sectioned into 2 halves and each half was prepared for silver nitrate staining to evaluate nano-leakage under SEM. Three photomicrographs were taken for each half-slab (30 photomicrographs/group) then analyzed using ImageJ software. Data were evaluated using Kruskal-Wallis/Mann-Whitney test (P=0.05). Flowable composite had no significant effect on nano-leakage (P=0.129), while storage time showed a statistically significant effect of nano-leakage (P˂0.0001). There was no statistically significant difference regarding the use of flowable resin composite either at 24 h and 6 m storage times (P˃0.05). There was a statistically significant difference between 24 h and 6 m storage periods for all experimental variables (P˂0.05). The two types of flowable composites were not able to prevent the uptake of silver nitrate at the composite/composite interface either after 24 h or 6 m.

Acompanhamento de três anos de restaurações do tipo bulk-fill flow em dentes posteriores: ensaio clínico controlado randomizado duplo-cego

Objective: This randomized clinical trial evaluated the behavior of restorations with flowable bulk-fill resin composite in posterior teeth three years after the restorative treatment. Methods: Seventeen patients (12 women, 5 men, age 23-59) were selected to have at least two failing amalgam or resin restorations replaced and/or to have a carious lesion restored. The cavities were randomly allocated to receive either the flowable bulk-fill composite Surefil SDR Flow occlusally covered with the conventional nano-hybrid composite Esthet-X HD (bulk and body technique) or filled exclusively with Esthet-X HD placed in 2 mm increments (incremental technique). A two-step etch-and-rinse adhesive was applied in all cavities. Thirty-four Class I or II restorations were performed in posterior teeth (n=17) during baseline. After 03 years, modified USPHS and FDI criteria were used to evaluate the restorations. Data were subjected to Mann-Whitney statistical analysis (p0.05). No restoration failures were observed over time. Conclusion: After 03 years of clinical service, all restorations using a flowable bulk-fill composite in posterior teeth showed an acceptable performance. Clinical Significance: The overall quality of posterior restorations made with the bulk and body technique was similar to that of restorations made with a nano-hybrid composite incrementally placed.

Evaluating the Failure of Resin-based Materials on the Proximal Cervical Dentin

Background: Resin-based materials are the popular restorative material in dentistry. The majority of these materials are light cured with a major disadvantage: marginal leakage. Objective: To evaluate the gap width of different resin-based materials at the cervical dentin when achieved mechanical force. Methods: Class II cavities were prepared on extracted premolar teeth with the gingival margin 1 mm below the Cementoenamel Junction (CEJ). In the first three experimental groups, three different lining materials (flowable resin composite, bulk-fill flowable resin composite, and resin-modified glass ionomer cement) were placed at the cervical dentin with a thickness of 1 mm. The rest of the cavities were restored with conventional resin composite. The other two groups were restored with conventional resin composite (control) or high viscosity bulk-fill resin composite, respectively. All groups were thermocycled and underwent vacuum pressure 2.6 KPa for 30 min in a Scanning Electron Microscope (SEM). Results: There was no gap formation at the cervical dentin on the external surface when restored with high-viscosity bulk fill resin composite. Almost all gaps occurred at the interface between restorative materials and the hybrid layer. The flowable bulk fill resin composite showed a significantly smaller gap width on both the external and internal surfaces compared to the other groups (p&lt; 0.05). The resin-modified glass ionomer cement showed the largest gaps in the cervical dentin (p &lt; 0.05). Conclusion: The different types of resin-based materials demonstrated a different failure of gap width under mechanical force. It clearly occurred at the restorative material-hybrid layer interface.

Comparative evaluation of microleakage of G-aenial Universal Flo, Smart Dentin Replacement and Tetric Evo Ceram bulk fill resin composite restorations in class v cavity preparation: an in-vitro study

Aim and Objective: Was to assess and compare the microleakage of G-aenial Universal Flo, Smart Dentin Replacement and Tetric Evo Ceram bulk fill resin composites in class V cavities along the occlusal and gingival margins using dye penetration test under stereomicroscope. Materials and Methods: Seventy five human extracted premolars were selected and randomly divided into 3 groups (n=25), as per the restorative materials for microleakage test. Group I: Tetric Evo Ceram (Bulk fill non flowable). Group II: G-aenial Universal Flo (Highly filled flowable resin composite). Group III: Smart Dentin Replacement (Bulk fill flowable resin composite). Class V (box) cavities were prepared both on the buccal and lingual surfaces of each of the 75 teeth, a total of 150 cavities, restored, immersed in 2% methylene blue dye for 24 hours and then sectioned bucco lingually into two halves. Dye penetration score was measured along occlusal and gingival wall using a Stereomicroscope at 40X magnification. Statistical analysis was done using Chi square test for microleakage assessment. P value was set at E‚0.05. Result: Intergroup comparison showed statistically no significant difference between the three groups both occlusal and gingival wall, whereas groupwise comparison showed statistically significant result between group I and Group II at gingival wall with P value 0.021. Conclusion: None of three resin composite materials were free from microleakage. All the three materials showed more microleakage at gingival wall compared to occlusal wall. Among all the tested groups G-aenial Universal Flo showed the least microleakage at the gingival wall. Keyword: Microleakage, Class V, Resin composites.

Development of a Bioactive Flowable Resin Composite Containing a Zinc-Doped Phosphate-Based Glass.

Flowable resins used for dental restoration are subject to biofilm formation. Zinc has antibacterial properties. Thus, we prepared a zinc-doped phosphate-based glass (Zn-PBG) to dope a flowable resin and evaluated the antibacterial activity of the composite against Streptococcus mutans (S. mutans) to extrapolate the preventative effect toward secondary caries. The composites were prepared having 0 (control), 1.9, 3.8, and 5.4 wt.% Zn-PBG. The flexural strength, elastic modulus, microhardness, depth of cure, ion release, inhibition zone size, and number of colony-forming units were evaluated and analyzed using ANOVA. The flexural strength of the control was significantly higher than those of Zn-PBG samples (p < 0.05). However, all samples meet the International Standard, ISO 4049. The microhardness was not significantly different for the control group and 1.9 and 3.8 wt.% groups, but the 5.4 wt.% Zn-PBG group had a significantly lower microhardness (p < 0.05). Further, the composite resins increasingly released P, Ca, Na, and Zn ions with an increase in Zn-PBG content (p < 0.05). The colony-forming unit count revealed a significant reduction in S. mutans viability (p < 0.05) with increase in Zn-PBG content. Therefore, the addition of Zn-PBG to flowable composite resins enhances antibacterial activity and could aid the prevention of secondary caries.

Class II resin composite restorations\u2014tunnel vs. box-only in vitro and in vivo

PurposeIn a combined in vitro/in vivo approach, tunnel vs. box-only resin composite restorations should be evaluated using thermomechanical loading (TML) in vitro and a restrospective clinical trial in vivo.Materials and methodsFor the in vitro part, box-only and tunnel cavities were prepared in 32 extracted human third molars under simulated intraoral conditions in a phantom head. Specimens were randomly assigned to four groups (n = 8; 16 box-only/16 tunnel) and received bonded resin composite restorations with Amelogen Plus (box A/tunnel A) or lining with Ultraseal and Amelogen plus (box B/tunnel B) both bonded using PQ1 (all Ultradent). Specimens were subjected to a standardized aging protocol, 1-year water storage (WS) followed by TML (100,000 × 50 N; 2500 × + 5/+ 55 °C). Initially and after aging, marginal qualities were evaluated using replicas at × 200 magnification (SEM). For the corresponding in vivo observational study, 229 patients received 673 proximal resin composite restorations. From 371 tunnel restorations, 205 cavities were filled without flowable lining (tunnel A), and 166 tunnels were restored using UltraSeal as lining (tunnel B). A total of 302 teeth received conventional box-only fillings. Restorations were examined according to modified USPHS criteria during routine recalls up to 5 years of clinical service.ResultsIn vitro, all initial results showed 100% gap-free margins when a flowable lining was used. Tunnels without lining exhibited some proximal shortcomings already before TML and even more pronounced after TML (p < 0.05). After TML, percentages of gap-free margins dropped to 87–90% in enamel with lining and 70–79% without lining (p < 0.05). In vivo, annual failure rates for box-only were 2.2%, for tunnel A 6.1%, and for tunnel B 1.8%, respectively (p < 0.05). Tunnels had significantly more sufficient proximal contact points than box-only restorations (p < 0.05). Flowable lining was highly beneficial for clinical outcome of tunnel-restorations (p < 0.05).ConclusionsWith a flowable lining, tunnel restorations proved to be a good alternative to box-only resin composite restorations.Clinical relevanceClass II tunnel restorations showed to be a viable alternative for box-only restorations, however, only when flowable resin composite was used as adaptation promotor for areas being difficult to access.

Reflectance and transmittance of flowable dental resin composite predicted by the two-flux model: on the importance of analyzing the effective measurement geometry

Flowable direct resin composite materials used in the dental domain are among materials that scatter light rather weakly, giving to millimeter-thick samples a certain translucent aspect. In order to predict the spectral reflectance and the color of such samples, the two-flux theory, i.e., Kubelka-Munk model (with Saunderson correction), remains the standard approach used in the dental domain, in spite of its known limitations when scattering is too weak. The present study, however, shows that a careful analysis of the light signal effectively measured on weakly scattering samples with instruments based, as usually recommended, on the d:8° measurement geometry, and a subsequent reevaluation of the parameters used in the Saunderson correction formulas with respect to the effective measurement geometry, can considerably improve the prediction accuracy of the model in both reflectance and transmittance modes, as confirmed by experiments carried out with samples of dental flowable resin composite material of different thicknesses. This broadens the applicability domain of the model, and might satisfy users preferring the simplicity of the two-flux model and the affordable equipment it needs to more relevant but more complex light scattering theories.

Long-term evaluation of warm-air treatment effect on adaptation of silane-containing universal adhesives to lithium disilicate ceramic.

The effect of warm air-blowing on the sealing ability of two one-bottle and one two-bottle silane-containing universal adhesives (UAs) applied to lithium disilicate ceramics (LDS) was evaluated. Tapered cavities prefabricated in LDS blocks (IPS e.max CAD) were treated by the adhesives, air-blown either with normal air (23±1°C) or warm air (60±5°C), and filled with a flowable resin composite. Interfacial gap formation was observed using swept-source optical coherence tomography immediately after filling, after 24 h, 5,000 and 10,000 thermal cycles, and an additional 1-year water storage. Specimens bonded using normal air-blown one-bottle UAs exhibited a significantly higher gap formation than the two-bottle UA (p<0.001), and detached within 24 h. Warm air-blowing significantly decreased the gap formation of one-bottle UAs (p<0.001), but the specimens dislocated within 24 h or during thermocycling. The two-bottle UA withstood all aging procedures and warm air-blowing significantly decreased its 1-year gap formation compared to normal air-blowing (p=0.002).

Evaluation of structural coloration of experimental flowable resin composites.

To examine the effect of filler contentTo examine the effect of filler content on structural coloration of experimental flowable resin composites. Experimental composites containing spherical fillers and different filler contents (30, 40, 50, 60 and 70 wt%), a structural colored resin composite (Omnichroma), and a nanohybrid flowable resin composite (Gracefil LoFlo) were used. The optical characteristics of the specimens were measured on standard black and white backgrounds using a spectrophotometer under CIE D65 illuminant and the L*a*b* values were determined. The color matching abilities to artificial teeth were evaluated using the ΔE*ab and ΔE00 color difference formulas. One-way analysis of variance and Tukey's post hoc test were used. The spectral reflectance of experimental composites showed different trends in different backgrounds, plate thickness, and filler contents. In particular, higher spectral reflectance was observed on the white background at wavelengths ranging from 450 to 700 nm in both 1.5 and 3.0 mm plates when compared to the black background. The percent reflectivity tended to decrease with a decrease of the filler contents. The color matching abilities of the experimental composites improved with the increase in the filler contents. Structural coloration of the flowable resin composites were affected by the filler contents. Clinical Significance: Higher filler contents might be needed to achieve the optimal color properties of structural colored flowable resin composites, thereby improving the restoration esthetics.

Profundidade de cura das resinas bulk fill variando a fonte de luz

Analisar a profundidade de cura das resinas do tipo Bulk Fill (Fluida e Pasta) alterando a fonte de luz. 10 tipos de resinas foram analizadas: (P) Pasta: FiltekTM One Bulk Fill (F1), Tetric N-Ceram Bulk Fill (T1); Aura Bulk Fill (A1); OPUS Bulk Fill (O1) e (F) Fluida: FiltekTM Bulk Fill Flow (F2); Tetric N-Flow Bulk Fill (T2); SDR® Plus Bulk Fill Flowable (S2); OPUS Bulk Fill Flow (O2). Foram confeccionados três discos para cada grupo seguindo ISO 4049/2000, através de molde (4x10mm), que foi totalmente preenchido com resina e fotoativado num tempo de 20s, sendo variado a fonte de luz entre Gnatus (G) e Kavo (K). Imediatamente depois as amostras foram removidas e a parte não polimerizada foi retirada com espátula de plástico. A mensuração foi realizada com um micrômetro de precisão ± 0,1mm. Os dados foram analisados usando ANOVA One-Way e ANOVA Two-Way e teste-t com significância de 0,05. Os grupos T1-K, S1-K, F1-K, F1-G, F2-G e T1-G mostraram resultados de profundidade de polimerização compatíveis com recomendações de fabricante. As fontes de luz G e K não apresentaram diferença (p = 0,068), mas entre os grupos (O2-G) (O2-K) (p = 0,004) houve diferença. Não foram encontradas diferenças entre as resinas (P-K p = 0,059), mas houve: grupo (F-K p =&lt; 0,050), entre resinas-K (p =&lt; 0,050), entre grupos (P-G) (F-G) e resinas-G (p =&lt; 0,050). Resinas fluidas (S2 e T2) apresentaram resultados de profundidade de cura superior a outras. A composição do material, assim como o comprimento de onda, pode ter influenciado nos resultados.

Repair of temporary fixed dental prostheses using a flowable resin composite: Effect of material, bonding, and aging

ObjectivesAssessment of the effect of aging and bonding on the reparability of different temporary crown and bridge materials using a flowable resin composite. MethodsThe materials used included two bis-acryl and two polymethylmethacrylate materials. The materials were aged either dry, in distilled water, or in a 75% ethanol/water solution. Each group was divided into three subgroups (n = 6) according to the bonding method: application of a universal adhesive, application of a universal primer followed by a universal adhesive, or no bonding. Materials were repaired with a light-cure flowable resin composite; then, they were subjected to thermocycling and tested by shear bond strength. The data were analysed using three-way ANOVA, one-way ANOVA, and Tukey post hoc tests (α = 0.05). ResultsThe shear bond strength was significantly higher for bis-acryl compared to polymethylmethacrylate materials (p < 0.001). In terms of aging conditions, shear bond strength was in the order of 75% ethanol/water solution < dry < water. The application of bonding agents significantly increased the shear bond strength of polymethylmethacrylate-based materials (p < 0.001). The difference between water and dry storage was insignificant (p = 0.558); however, storage in a 75% ethanol/water solution showed significantly lower values compared to both dry and water storage in most of experimental groups (p < 0.001). Polymethylmethacrylate-based materials mainly demonstrated adhesive failure, while bis-acryl materials predominantly showed cohesive failure. ConclusionThe bond strength of a light-cure flowable resin composite is significantly higher with bis-acryl compared to that with polymethylmethacrylate-based substrates. Aging in water does not have a significant effect; however, the 75% ethanol/water solution tends to negatively affect repairability. The application of different bonding agents positively affects the repair strength, especially for polymethylmethacrylate-based substrates.

Influences of Successive Exposure to Bleaching and Fluoride Preparations on the Surface Hardness and Roughness of the Aged Resin Composite Restoratives.

Background and Objectives: Surfaces of composite restorations are adversely affected upon bleaching and topical fluoride application. Such a procedure is normally carried out in the presence of restorations already serving in a different oral environment, although previous in vitro studies only considered the freshly-prepared composite specimens for assessment. The current study accordingly aimed to evaluate both the surface hardness and roughness of aged composite restoratives following their successive exposure to bleaching and topical fluoride preparations. Materials and Methods: Disc specimens were prepared from micro-hybrid, nano-filled, flowable and bulk-fill resin composites (groups 1–4, n = 60 each). All specimens were subjected to artificial aging before their intermittent exposure to surface treatment with: none (control), bleach or topical fluoride (subgroups 1–3, n = 20). All surface treatments were interrupted with two periods of 5000 thermal cycles. Specimens’ surfaces were then tested for both surface hardness (Vickers hardness number (VHN), n = 10) and roughness (Ra, n = 10). The collected VHNs and Ras were statistically analyzed using two-way ANOVA and Tukey’s comparisons at α = 0.05 to confirm the significance of differences between subgroups. Results: None of the tested composites showed differences in surface hardness and roughness between the bleached and the non-treated specimens (p > 0.05), but the bleached flowable composite specimens only were rougher than their control (p < 0.000126). In comparison to the control, fluoride treatment not only reduced the surface hardness of both micro-hybrid (p = 0.000129) and flowable (p = 0.0029) composites, but also increased the surface roughness of all tested composites (p < 0.05). Conclusion: Aged composite restoratives provide minimal surface alterations on successive bleaching and fluoride applications. Flowable resin composite is the most affected by such procedures. Although bleaching seems safe for other types of composites, the successive fluoride application could deteriorate the aged surfaces of the tested resin composites.

Simulated Cuspal Deflection and Flexural Properties of Bulk-Fill and Conventional Flowable Resin Composites.

Some bulk-fill flowable resin composites produce less cuspal deflection than a conventional incrementally filled flowable resin composites. Objective: This study investigated simulated cuspal deflection and flexural properties of bulk-fill and conventional flowable resin composites.Methods and Materials: Five bulk-fill and six conventional flowable resin composites were evaluated. Aluminium blocks with a mesio-occlusal-distal cavity were prepared and randomly divided into groups for each of the different measurement techniques and were further subdivided according to the type of flowable resin composite. The simulated cuspal deflection caused by the polymerization of resin composite within an aluminium block was measured using a highly accurate submicron digimatic micrometer or a confocal laser scanning microscope (CLSM). In addition, the flexural properties of tested resin composites were measured to investigate the relation between cuspal deflection and flexural properties, and the resin composites were observed using scanning electron microscopy.Results: Simulated cuspal deflection of some bulk-fill flowable resin composites was found to be significantly lower than or similar to those for conventional counterparts, regardless of the measurement method. There were statistically significant differences in flexural properties depending on the material, regardless of the type of flowable resin composite. Pearson correlation analysis did not reveal a statistically significant relationship between flexural properties and cuspal deflection.Conclusion: These results indicate that some bulk-fill flowable resin composites exhibit lower cuspal deflection with the bulk-filling technique than is shown by conventional flowable resin composites using the incremental filling technique. Simulated cuspal deflection can be measured using either a micrometer or CLSM, but this experiment failed to show a significant relationship between cuspal deflection and flexural properties of flowable resin composites.

Viscosity and thermal kinetics of 10 preheated restorative resin composites and effect of ultrasound energy on film thickness

ObjectiveThis study investigated viscosity and thermal kinetics of 10 selected preheated restorative resin composites and the effect of ultrasound energy on film thickness. MethodsA range of different resin composites was tested: Charisma Diamond, IPS Empress Direct, Enamel Plus HRi, Essentia, Estelite Omega, Filtek Z100, Filtek Z350 XT, Gradia, TPH Spectrum and VisCalor. A flowable resin composite (Opallis Flow) and two resin cements (RelyX Veneer, Variolink Esthetic LC) also were tested. Viscosity (Pa s) was measured at 37 °C and 69 °C (preheating temperature) using a rheometer. Film thickness (μm) was measured before and after application of ultrasound energy. Temperature loss within resin composite following preheating (°C/s) was monitored. Data were statistically analyzed (α = 0.05). ResultsViscosity at 69 °C was lower than at 37 °C for all materials except the flowable resin composite. Preheating reduced viscosity between 47% and 92% for the restorative resin composites, which were generally more viscous than the flowable materials. Film thickness varied largely among materials. All preheated resin composites had films thicker than 50 μm without ultrasound energy. Application of ultrasound reduced film thickness between 21% and 49%. Linear and nonlinear regressions did not identify any relationship between filler loading, viscosity, and/or film thickness. All materials showed quick temperature reduction following preheating, showing maximum temperature loss rates after approximately 10 s. SignificanceDistinct restorative resin composites react differently to preheating, affecting viscosity and film thickness. The overall performance of the preheating technique depends on proper material selection and use of ultrasound energy for reducing film thickness.

Microleakage Assessment of Resin Infiltration Combined Restoration in Artificial Decalcified-Cavitated Lesion

This study was performed to evaluate the restoration combined with resin infiltration (RI) of early cavitated smooth surface caries lesion in terms of microleakage. Flowable resin and resin-modified glass ionomer cement (RMGIC) were compared.Sound 20 extracted 3rd molars were divided into 2 groups randomly. Artificial decalcified lesion was induced. Cavities were prepared on the mesial and distal surfaces, and randomly set as experimental and control group. RI was applied to the experimental group before cavity restoration. The control group was restored without RI. In group I and II, flowable resin and RMGIC was used for restoration respectively. After thermocycling and silver nitrate immersion, microleakage was assessed by μ-CT.Depth of microleakage was lower in experimental group than control group only in group II (p = 0.05). Microleakage depth was lower in group II than group I in both experimental and control groups (p = 0.05).RI pretreatment before restoration of early cavitated caries lesions might reduce the microleakage and help long-term maintenance of restoration. In this study, RMGIC was less polymerization shrinkage. Restoration with RMGIC after RI pretreatment reduced the microleakage of the restoration compared to the flowable resin.

The effect of different light curing units on Vickers microhardness and degree of conversion of flowable resin composites.

This study aimed to assess the influence of different light curing units (LCUs) on the polymerization of various flowable resin composites. Three LCUs (Optilux 501, Elipar™ DeepCure-L LED and Bluephase®20i) and eight flowable resin composites: MI FIL Flow, Estelite Flow Quick, Estelite Universal Flow (medium), Estelite Universal Flow (super low), Beautifil Flow Plus, Clearfil Majesty ES Flow, Filtek Supreme Ultra flowable and TetricEvo Flow were tested. For Vickers microhardness (VHN) test and degree of conversion (DC), specimens were prepared and polymerized for 20 s. VHN test was performed at top surfaces (3 indentations) and DC for each specimen was measured using Fourier transform infrared (FT-IR) spectroscopy after 24 h dry storage in dark at 37˚C. The data were analyzed with 2-way ANOVA and t-test with Bonferroni correction. DC and hardness values showed a relationship between materials and LCUs. The curing efficacy of LCU type may depend on the material composition.

Comparison between Shear Bond Strength of Er:YAG and Er,Cr:YSGG Lasers-Assisted Dentinal Adhesion of Self-Adhering Resin Composite: An Ex Vivo Study.

(1) Background: Bonding composite to tooth structure is still evolving with a substitute for phosphoric acid being the main challenge. Lately, a self-adhering composite (SAC) was developed, promising to simplify bonding to tooth structure. Unfortunately, retention especially to dentin, was not as good as the gold standard three steps bonding system. During the last 2 decades, lasers were used to enhance shear bond strength of composite to tooth structure. However, the literature provided limited information regarding laser efficiency in the immediate, as well as the long term, adhesion success of SACs to dentin. The purpose of our study was to define the optimal irradiation conditions to improve the adhesion of self-adhering flowable resin composite to dentin exposed to Er:YAG and Er,Cr:YSGG laser irradiation. (2) Methods: Seventy-two freshly extracted human third molars, prepared to have flat dentinal surfaces, were randomly divided into three groups (n = 24) including a control group (Group 1) in which dentin was left without laser irradiation. The other two groups (Group 2 and 3) received standardized irradiation at a speed of 1 mm/second with Er:YAG (60 mJ; SSP mode = 50 μs; 10 Hz; fluency of 9.4 J/cm2; beam diameter: 0.9 mm; air 6 mL/min; and water 4 mL/min), and Er,Cr:YSGG: 1.5 W; fluency of 17.8 J/cm2; turbo handpiece with MX5 short insert; 20 Hz under air/water spray (65% air, 55% water). Self-adhering flowable resin was applied to dentin in all groups. Half of the specimens were stored in water for 24 h while the other half underwent 3000 thermal cycles. Later, all specimens received a shear bond strength test. Fracture observation was done first under a stereomicroscope then by using a scanning electron microscope. (3) Results: The mean values of shear bond strength for both laser-treated dentin groups (Er:YAG laser: 13.10 ± 1.291, and Er,Cr:YSGG: 14.04 ± 5.233) were higher than in the control group 1 (8.355 ± 2.297) before thermocycling. After thermocycling, shear bond strength decreased in all groups as follows: 10.03 ± 1.503, 10.53 ± 2.631, and 02.75 ± 1.583 for Er:YAG, Er,Cr:YSGG, and nonirradiated dentin, respectively. Shear bond strength values showed a significant difference between the control group (Group 1) and both lasers groups (Group 2 and 3). Statistical analysis of stereomicroscope observation revealed no significant difference between laser irradiation and failure mode (p < 0.136). SEM observation of the dentin surface in both laser-irradiated groups showed opened tubules, absence of smear layer as well as an increase of resin infiltration into dentinal tubules. (4) Conclusion: Er:YAG and Er,Cr:YSGG lasers enhance self-adhering flowable resin shear bond strength values and improve its longevity by eliminating the smear layer, opening dentinal tubules and increasing resin infiltration into the microstructure.