Effects of pre-heating on physical-mechanical-chemical properties of contemporary resin composites.

This research assessed the effects of pre-heating on the physical-mechanical-chemical properties of different resin composites. For this, resin composites were evaluated in 6 levels: Admira/ADM, Vitra/VIT, Filtek Supreme/FS, Filtek Supreme Flowable/FSF, Filtek One/FO, and Filtek Bulk Fill Flowable/FBF; temperature was evaluated in 4 levels using a composite heater: room temperature/22 ºC, 37 ºC, 54 ºC, and 68 ºC. Response variables were: degree of conversion/DC, flexural strength/FS and color stability/ΔE (immediately after light curing/LC, after 7 days of dark-dry-storage, and after 24 h and 3 days of artificial aging in water at 60 ºC). Data were subjected to 2-way ANOVA (DC and FR) and 3-way repeated measurements ANOVA (ΔE), all followed by Tukey's test (α = 5%). DC were similar (FBF, FS, and FSF) or increased (ADM, FO, and VIT) as the temperature increased. Results of FR were unchanged or increased for all composites except VIT and ADM. High-viscosity composites (VIT and FS) showed higher FR values than low-viscosity composite (FSF). For bulk-fill composites, FBF and FO showed similar results, but lower than high-viscosity composites. Results of color stability showed acceptable values up to 3 days aging except for ADM and FSF. ΔE was not influenced by pre-heating and, overall, ΔE: FS < VIT < FO < FSF < ADM < FBF. Only VIT and FS showed ΔE ≤ 3.3 (clinical threshold). Therefore, the effects of pre-heating depend on the material. The tested materials generally showed similar or enhanced properties after pre-heating (except ADM and VIT).

Effect of Pre-Heating on the Monomer Elution and Porosity of Conventional and Bulk-Fill Resin-Based Dental Composites.

The pre-heating of dental resin-based composites (RBCs) improves adaptability to cavity walls, reducing microleakages. However, the rapid cooling of the pre-heated RBC may change the polymerization kinetics, and thus the final network configuration of the RBC. It is well known that unreacted monomers remaining in the set RBC can leach into the oral cavity. However, it is still not clear how the pre-heating and cooling of RBCs alter monomer elution (ME). Thus, the purpose was to determine the ME from room-temperature and pre-heated RBCs, in addition to determining the closed porosity (CP) volume. Bulk-filled RBCs and layered conventional RBC samples were prepared. The pre-polymerization temperature was set at 24 °C and 55/65 °C. The ME from RBC samples was assessed with high-performance liquid chromatography using standard monomers. CP was measured with micro-computed tomography. ME decreased significantly from bulk fills and increased from layered samples as a result of pre-heating. Pre-heating was unfavorable in terms of CP in most RBCs. Based on the effect size analysis, ME and CP were greatly influenced by both material composition, pre-polymerization temperature, and their interaction. While the pre-heating of high-viscosity bulk-fill RBCs is advantageous from a clinical aspect regarding biocompatibility, it increases CP, which is undesirable from a mechanical point of view.

Evaluation of color stability and microhardness of contemporary bulk-fill composite resins with different polymerization properties.

OBJECTIVES: To determine the color stability and microhardness of three bulk-fill composites with different polymerization characteristics, after immersion in four different solutions. MATERIALS AND METHODS: Color measurements of three bulk fill (Viscalor (VIS), Tetric PowerFill (TPF), Fill Up! (FUP)) and a microhyrid composite resin (G-aenial posterior [GCP]) were performed after polymerization. The specimens were immersed in coffee, cola, red wine and distilled water. Discolorations were recorded after 24 h (T1), 10 days (T2) and 30 days (T3) of immersion. ΔE (CIEDE2000) values were calculated. Vickers microhardness (VHN) was measured from top and bottom surfaces at T0 and T3. Data was analyzed with Two-way ANOVA, One-way ANOVA and Tukey post hoc tests. RESULTS: The highest discoloration was seen in wine and the lowest in distilled water and cola. At T3, there was no difference in distilled water groups, while the statistically highest ΔE00 were obtained in TPF and GCP in coffee, cola and wine. VIS groups had the highest VHN values at T0 and T3 in all solutions. CONCLUSIONS: Samples immersed in coffee and wine showed discoloration beyond clinically acceptable limits. After 30 days, discoloration occurred in all materials immersed in all solutions. At T3, VIS microhardness generally decreased, while TPF did not. CLINICAL SIGNIFICANCE: After 30 days, all bulk-fill composites immersed in distilled water, coffee and wine showed clinically unacceptable ΔE00 .

[Comparison of the film thickness of composites of different degrees of viscosity]. / Tolshchina plenki kompozitov raznoi stepeni vyazkosti.

The measurement of the film thickness of the composite cement Variolink Esthetic («Ivoclar-Vivadent¼, Liechtenstein) and the microhybrid composite Enamel («Micerium¼, Italy) was carried out according to ISO 4049: 2009 standards with a load force of 5 kg. While reducing the load force to 5 kg, all materials showed an increase in the film thickness; the film thickness of the Variolink Esthetic composite cement was changed from 23 microns (at 15 kg) to 32 microns (at 5 kg), and the film thickness of the microhybrid composite film Enamel was changed from 39 microns (at 15 kg) to 102 microns (at 5 kg). After preheating, the film thickness was changed from 23 microns (at 15 kg) to 44 microns (at 5 kg).

[Study of the film thickness of dental composite resins after preheating]. / Izuchenie tolshchiny plenki kompozitov posle ikh nagrevaniia.

PURPOSE: To compare film thickness of adhesive resin cement and dental composite resins after they are preheated with hot air. MATERIAL AND METHODS: The film thickness was measured using adhesive resin cement Variolink esthetic (Ivoclar-Vivadent, Liechtenstein), micro-hybrid composite Enamel (Micerium, Germany) and nanofilled composite Estelite sigma quick (Tokuyama Dental, Japan) at different temperatures. RESULTS: The film thickness of the Variolink esthetic at room temperature was 23 µm, and the dental composites after preheating them with hot air and applying adhesive on both surfaces to be joined produced the following results: Estelite 62 µm and Enamel 25 µm. CONCLUSION: As a result of the study, it was found that the proposed method allows one to achieve a film thickness for high-viscosity composites comparable to the film thickness of composite cements.

Effects of pre-heating of broiler breeder's eggs on hatchability, chick quality, overall performance, and welfare traits in broilers.

This study aimed to investigate the effects of varying pre-heating practices (12-h: PH12; 8-h: PH8; 4-h: PH4 and 0-h or no pre-heating: PH0) of broiler breeder's eggs prior to incubation on hatching, chick quality, overall performance, and welfare traits in broilers. A total of 960 eggs obtained from Ross 308 breeders at 45 weeks were used for pre-heating manipulations and 480 chicks for broiler experiment. Apparent fertility was higher in PH0 (94.6%) and PH4 (94.5%) treatments than in PH8 (91.6%) and PH12 (90.6%); hatchability of fertile and set eggs was higher in PH4 and PH12. PH4, PH8, and PH12 treatments significantly accelerated the average hatching time compared to PH0. General chick quality was not affected by pre-heating treatments. However, chick length was significantly lower in PH0 chicks than PH12. Pre-heating manipulations did not change the overall broiler performance. Welfare characteristics were similar among treatments, while only hock burn was better in PH8 broilers. In conclusion, pre-heating of broiler breeder eggs for 4 to 12 h improved hatching success by lowering embryonic mortality and shortened the average hatching time compared to no pre-heating, and did not cause any significant alteration in chick quality, overall performance, and welfare characteristics.

Behavior of wheat flour dough at different pretreated temperatures through rheological characteristics and molecular interactions of proteins.

Rheological properties and chemical interactions of doughs prepared at different temperatures were evaluated. The results showed that the rigidity of pretreated doughs was enhanced, and the processing performance of doughs was weakened. Preheating resulted in the polymerization of gluten through the conversion of sulfhydryl groups to disulfide bonds. The noncovalent interaction of dough played a dominant role and further led to the production of glutenin macropolymers (55.77 mg/g). CLSM images verified that preheating promoted the formation of the coarse and scattered gluten network, while preheating at 80 °C led to a higher gluten area percentage (40.27 %) and lower lacunarity (6.74 × 10-2) structure. The migration of water promoted changes in hydrogen bond and hydrophobic interaction in doughs, which directly affect the processability of doughs. The study provides information for predicting the rheological behavior of dough in actual production and makes it possible to modify gluten by preheating treatment without complicating existing operations.

Effect of pre-heating methods and devices on the mechanical properties, post-gel shrinkage, and shrinkage stress of bulk-fill materials.

This study evaluated the effect of using two different pre-heating methods on the three resin-based composite (RBCs). Three paste viscosity bulk-fill RBCs (VisCalor Bulk [VC]; VOCO; x-tra fil Caps [XF], VOCO; Filtek One Bulk Fill [FO], 3 M) were pre-heated using either a VisCalor Dispenser (VOCO) to 65 °C, or the Caps Warmer (VOCO) to 37 °C, 54 °C, or 68 °C. The temperature inside the capsules and cavity was monitored before and after insertion into the matrix. Within 30 s of inserting the RBC, they were light-activated using a VALO (Ultradent) curing light for 20 s. The post-gel shrinkage (Shr - %), Flexural Strength (FS - MPa), Elastic Modulus (E - MPa), degree of conversion (DC - %), Knoop Hardness (KH - N/mm2), diametral tensile strength (DTS - MPa), and compressive strength (CS - MPa) of the RBCs were measured (10 specimens per group). The shrinkage stress was calculated using three-dimensional finite element analysis. Data were analyzed using one-way, two-way ANOVA and Tukey's test (α = 0.05). The temperature fell rapidly after the RBC was inserted into the cavity. Pre-heating the RBCs did not affect the mechanical properties. FO had the lowest E, DC, and KH values, VC had intermediate values, and XF achieved the highest values. The DTS and CS values were not affected by the various pre-heating methods, the temperature, or RBC. Pre-heating methods at 37 °C produced higher shrinkage for all RBCs. VC pre-heated to 65 °C produced the lowest stress when measured at 10 min after light activation.

Composite Pre-heating: A Novel Approach in Restorative Dentistry.

Resin composite pre-heating is a novel approach that might improve handling and marginal adaptation of the unset material paste in clinical application. The goal of this review article is to compile all laboratory experiments on resin composite preheating and see how it impacts the mechanical properties of the material. Results have shown that preheating composite resins improves the degree of conversion, stiffness, marginal adaptability, and microhardness. While flexural strength is unbothered, polymerization shrinkage is hindered, and the microleakage results are unknown.

A Comparison of Microtensile Bond Strength, Film Thickness, and Microhardness of Photo-Polymerized Luting Composites.

The aim of this study was to evaluate the effect of CAD/CAM composite thickness on micro-tensile bond strength (µTBS), microhardness (HV), and film thickness (FT) of different luting composites. Composite blocks (6.8 mm × 6.8 mm) were divided into 12 groups according to: CAD/CAM thickness and luting composite. For each group, 21 rods (1 mm × 1 mm) were tested in tension at crosshead speed of 1 mm/min. Fracture modes were categorized as adhesive, mixed, and cohesive. Microhardness (n = 5/group) was assessed using microhardness tester. Film thickness (12-rods/group) was evaluated using a stereomicroscope (×40). Data were analyzed using the two-way ANOVA/Tukey's HSD test (p = 0.05). Parameters "thickness", "cement", and "thickness x cement" showed significant difference on µTBS and HV (p < 0.05). At 2 mm, heated x-tra fil composite showed the highest µTBS (45.0 ± 8.5 MPa), while at 4 mm thickness, Grandio Flow revealed the lowest µTBS (33.3 ± 6.3 MPa). Adhesive, mixed, and cohesive failures were reported. The HV of all composites decreased when photo-polymerized through 4 mm thickness (p < 0.05). Regardless of CAD/CAM thickness, photo-polymerized composites can be successfully used for luting CAD/CAM composite.

Pre-Heating Effect on Monomer Elution and Degree of Conversion of Contemporary and Thermoviscous Bulk-Fill Resin-Based Dental Composites.

Detection of unreacted monomers from pre-heated resin-based dental composites (RBC) is not a well-investigated topic so far. The objectives were to determine the temperature changes during the application and polymerization, the degree of conversion (DC) and unreacted monomer elution of room temperature (RT), and pre-heated thermoviscous [VisCalor Bulk(VCB)] and high-viscosity full-body contemporary [Filtek One Bulk(FOB)] bulk-fill RBCs. The RBCs' temperatures during the sample preparation were recorded with a K-type thermocouple. The DC at the top and bottom was measured with micro-Raman spectroscopy and the amounts of eluted BisGMA, UDMA, DDMA, and TEGDMA were assessed with High-Performance Liquid Chromatography. The temperatures of the pre-heated RBCs decreased rapidly during the manipulation phase. The temperature rise during photopolymerization reflects the bottom DCs. The differences in DC% between the top and the bottom were significant. RT VCB had a lower DC% compared to FOB. Pre-heating did not influence the DC, except on the bottom surface of FOB where a significant decrease was measured. Pre-heating significantly decreased the elution of BisGMA, UDMA, DDMA in the case of FOB, meanwhile, it had no effect on monomer release from VCB, except TEGDMA, which elution was decreased. In comparison, RBC composition had a stronger influence on DC and monomer elution, than pre-cure temperature.

Micro-computed tomographic evaluation of the effects of pre-heating and sonic delivery on the internal void formation of bulk-fill composites.

The aim of this study was to compare the effects of conventional, sonic or pre-heating insertion techniques on internal void formation of bulk-fill composites with micro-computed tomography. Standardized cylindrical cavities were prepared in 160 human third molars. Four groups received different paste-like bulk-fill composites: SonicFill 2 (SF2); VisCalor Bulk (VCB); Filtek One Bulk-fill restorative (FBF); Tetric EvoCeram Bulk Fill (TEB); and a conventional posterior composite, Clearfil Majesty Posterior (CMP). A hybrid CAD/CAM block was selected as a control (n=10). Composite restorations were built according to each resin composite type and insertion technique (n=10). Micro-CT was used to assess internal void rates. Data was analyzed with two-way ANOVA and Tukey's multiple comparisons test (α=0.05). CAD/CAM blocks were free of voids. For each composite, the highest void rates were observed for the sonic delivery method (p<0.05) except for SF2. SF2 was not affected by insertion techniques (p>0.05). Other composites showed the lowest void rates with pre-heating technique.

Laser Powder Bed Fusion (LPBF) of In718 and the Impact of Pre-Heating at 500 and 1000 °C: Operando Study.

The morphology of a melt pool has a critical role in laser powder bed fusion (LPBF). Nevertheless, directly characterizing the melt pool during LPBF is incredibly hard. Here, we present the melt pool flow of the entire melt pool in 3D using mesoscopic simulation models. The physical processes occurring within the melt pool are pinpointed. The flow patterns throughout the same are exposed and measured. Moreover, the impact of pre-heating at 500 and 1000 °C has been described. The study findings offer insights into LPBF. The findings presented here are critical for comprehending the LPBF and directing the establishment of improved metrics for process parameters optimization.

Does Preheating Resin Cements Affect Fracture Resistance of Lithium Disilicate and Zirconia Restorations?

This paper assesses the impact of preheating of adhesive cement on the fracture resistance of lithium disilicate and zirconia restorations. Methods: A total of 80 human maxillary premolar teeth were assigned into 8 groups (n = 10) according to material type (either lithium disilicate or zirconia) and type of resin cement (either LinkForce or Panavia SA) with preheating temperature at 54 °C or at room temperature (25 °C). Teeth were prepared and restored with either lithium disilicate or zirconia restorations. After cementation, specimens were thermal cycled (10,000 cycles, 5 °C/55 °C), then load cycled for 240,000 cycles (50 N). Each specimen was statically loaded until fracture and the load (N) at fracture was recorded, then the failure mode was detected. Statistical analysis of data was performed (p ≤ 0.05). Results: There was no significant difference (p = 0.978) in fracture mean values between LinkForce and Panavia SA. Statistically significant difference (p = 0.001) was revealed between fracture resistance of lithium disilicate restorations cemented with LinkForce at 25 °C and at 54 °C; however there was no significant difference (p = 0.92) between the fracture resistance of lithium disilicate restorations cemented with Panavia SA used at 25 °C and at 54 °C. Regarding the interaction between ceramic material, cement type, and cement preheating, there was no significant effect (p > 0.05) in fracture resistance. The cement type does not influence the fracture resistance of ceramic restorations. Preheating of resin cement has negatively influenced the fracture resistance of all tested groups, except for lithium disilicate cemented using LinkForce cement.

Viscosity and stickiness of dental resin composites at elevated temperatures.

OBJECTIVE: To investigate the influence of pre-heating different classes of dental resin composites on viscosity and stickiness at five different temperatures. METHODS: Six flowable, five conventional packable, and one thermo-viscous bulk-fill resin composites were heated up to 54°C in a plate-plate rheometer to determine their complex viscosity. Normal force measurements were carried out for the six packable materials to determine the unplugging force and unplugging work (stickiness) over the same temperature range. Data were analyzed using Kolmogorov-Smirnoff test, one-way ANOVA and Tukey Post Hoc test with α=0.05 as level of significance. RESULTS: At 23°C packable composites showed viscosity between 6.75 and 19.14kPas, while flowable composites presented significantly lower viscosities between 1.31 and 2.20kPas. Pre-heating led to a drop of 30-82% in the viscosity of packable materials. The thermo-viscous material dropped to the level of flowables at 45 and 54°C thus behaving as a packable composite at room temperature with flowable-like viscosity at higher temperatures. No statistically significant differences for viscosity were observed among flowable composites at any temperature. The unplugging force decreased for packable composites, while their unplugging work generally increased at elevated temperature. At 23°C unplugging force was measured between 7.50 and 19.18N, while pre-heating up to 54°C led to values between 2.9 and 6.2N. Regarding unplugging work at 23°C the calculated values were between 3.0 and 8.9×10-3J and at 54°C between 8.8 and 13.0×10-3J. SIGNIFICANCE: Pre-heating significantly reduced viscosity of highly viscous resin composites, while no influence was shown for flowable composites. In general stickiness, measured as unplugging work, increased at elevated temperatures. The thermo-viscous material showed low viscosity comparable to flowable composites at 45 and 54°C, yet its stickiness did not increase significantly compared to the values at 23°C.

Spatio-temporal temperature fields generated coronally with bulk-fill resin composites: A thermography study.

OBJECTIVE: This study aimed to investigate the effects of (i) a high-irradiance (3s) light-curing protocol versus (ii) two standard-irradiance (10s) protocols on 2D temperature maps during intra-dental photo-irradiation within a molar cavity restored with either Ultra-Rapid Photo-Polymerized Bulk Fill (URPBF) composites or a pre-heated thermo-viscous bulk-fill composite, compared to a standard bulk-fill resin-based-composite (RBC). The specific objectives included visual assessment of the temperature maps and quantitative assessment of several temperature/time plots at four different locations. METHODS: A caries-free lower first molar cavity served as a natural tooth mold. Resin composites were placed without intermediary adhesive. Two URPBF composites (PFill; PFlow) and one pre-heated thermo-viscous bulk-fill composite (Viscalor: VC) were compared to a contemporary bulk-fill composite (One Bulk Fill: OBF). Two LED-LCU devices were used: Bluephase PowerCure (PC) and Elipar S10 (S10), with three light-irradiation protocols (PC-3s, PC-10s and S10-10s). 2D temperature maps over the entire coronal area were recorded for 120 s during and after irradiation using a thermal imaging camera. Changes at four different levels were selected from the data sets: (0, 2 and 4 mm from the cavity top and at 1 mm below the dentin cavity floor). The maximum temperature attained (Tmax), the mean temperature rise (ΔT), the time (s) to reach maximum temperature and the integrated areas (°C s) under the temperature/time (T/t) plots were identified. Data were analysed via three-way ANOVA, One-way ANOVA, independent t-tests and Tukey post-hoc tests (p < 0.05). RESULTS: All RBCs showed qualitatively similar temperature-time profiles. PFlow reached Tmax in the shortest time. PC-3s (3000 mW/cm2) generated comparable ΔT to S10-10s, except with PFill, where ΔT was greater. Despite the same irradiance (1200 mW/cm2), Elipar S10 led to higher Tmax and ΔT compared to PC-10s. The highest Tmax and ΔT were observed at the 2 mm level, and the lowest were at 1 mm depth into the underlying dentin. SIGNIFICANCE: Coronal 2D temperature maps showed rises largely confined within the bulk-fill RBC materials, with maxima at 2 mm rather than 4 mm depth indicating some extent of thermal insulation for the underlying dentin and pulp. RBCs polymerized via different irradiation protocols showed similar temperature changes. With the PC-3s protocol - also with pre-heated VC - minimal temperature rises at 1 mm within dentin suggest their clinical safety when sufficient remaining dentin thickness is present.

Effect of different composite modulation protocols on the conversion and polymerization stress profile of bulk-filled resin restorations.

OBJECTIVE: The aim of this in vitro study was to test the effect of different composite modulation protocols (pre-heating, light-curing time and oligomer addition) for bulk filling techniques on resin polymerization stress, intra-pulpal temperature change and degree of conversion. METHODS: Class I cavities (4mm depth×5mm diameter) were prepared in 48 extracted third molars and divided in 6 groups. Restorations were completed with a single increment, according to the following groups: (1) Filtek Z250XT (room temperature - activated for 20s); (2) Filtek Z250XT (at room temperature - activated for 40s); (3) Filtek Z250XT (pre-heated at 68°C - activated for 20s); (4) Filtek Z250XT (pre-heated at 68°C - activated for 40s); (5) Filtek BulkFill (at room temperature - activated for 20s); (6) Filtek Z250XT (modified by the addition of a thio-urethane oligomer at room temperature - activated for 40s). Acoustic emission test was used as a real-time polymerization stress (PS) assessment. The intra-pulpal temperature change was recorded with a thermocouple and bottom/top degree of conversion (DC) measured by Raman spectroscopy. Data were analyzed with one-way ANOVA/Tukey's test (α=5%). RESULTS: Pre-heating the resin composite did not influence the intra-pulpal temperature (p=0.077). The thio-urethane-containing composite exhibited significantly less PS, due to a lower number of acoustic events. Groups with pre-heated composites did not result in significantly different PS. Filtek BulkFill and the thio-urethane experimental composite presented significantly higher DC. SIGNIFICANCE: Resin composite pre-heating was not able to reduce polymerization stress in direct restorations. However, thio-urethane addition to a resin composite could reduce the polymerization stress while improving the DC.

Pre-heating time and exposure duration: Effects on post-irradiation properties of a thermo-viscous resin-composite.

OBJECTIVE: To evaluate the effects of pre-heating time and exposure duration on the degree of conversion (DC), maximum rate of polymerization (RPmax), polymerization shrinkage strain (PS) and surface micro-hardness (VHN) of Viscalor. METHODS: Viscalor syringes were pre-heated using a Caps Warmer (VOCO, Germany) in T3 mode (at 68°C) for 30s (T3-30s) and 3min (T3-3min) and then the composite paste was extruded into appropriately sized molds. Light irradiation was applied at zero distance from the upper surface with a LED-LCU of mean irradiance 1200mW/cm2 for either 20 or 40s. The real-time polymerization kinetics and DC at 5min and 24h post-irradiation (DC5min and DC24h) were measured using ATR-FTIR (n=3). PS was obtained with the bonded-disk technique (n=3). Top and bottom Vickers micro-hardness (VHNtop and VHNbottom) were measured at 5min post-irradiation and after 24h dry storage (n=5). Data were analysed using one-way ANOVA, two-way ANOVA, independent t-test and Tukey post hoc tests (p<0.05). RESULTS: Polymerization kinetic curves of Viscalor from 0 to 15min were similar for different pre-heating times and exposure durations. Pre-heated Viscalor (T3-30s and T3-3min) with 40s exposure had greater VHNtop and VHNbottom than for Viscalor (no heat) (p<0.05). Exposure duration did not significantly affect DC, RPmax and PS (p>0.05). After 24h storage, DC and VHN increased. Pre-heating did not increase the DC24h, relative to no pre-heating (p>0.05). Two-way ANOVA showed that there was no significant interaction between pre-heating time and exposure duration (p>0.05). SIGNIFICANCE: Increasing irradiation time from 20 to 40s did not affect DC, RPmax or PS, but increased VHNtop. Composite pre-heating had no adverse effect through any premature polymerization. For Viscalor, 3min pre-heating and 20s irradiation were sufficient to provide adequate hardness, without increasing PS or compromising polymerization kinetics.

Testing spore amyloidity in Agaricales under light microscope: the case study of Tricholoma.

Although species of the genus Tricholoma are currently considered to produce inamyloid spores, a novel standardized method to test sporal amyloidity (which involves heating the sample in Melzer's reagent) showed evidence that in the tested species of this genus, which belong in all 10 sections currently recognized from Europe, the spores are amyloid. In two species, T. josserandii and T. terreum, the spores are also partly dextrinoid. This result provides strong indication that a positive reaction of the spores in Melzer's reagent could be a character shared by all genera in Tricholomataceae s. str.

Effect of exposure time and pre-heating on the conversion degree of conventional, bulk-fill, fiber reinforced and polyacid-modified resin composites.

OBJECTIVE: To determine the degree of conversion (DC) of different type of resin-based composites (RBC) in eight-millimeter-deep clinically relevant molds, and investigate the influence of exposure time and pre-heating on DC. METHODS: Two-millimeter-thick samples of conventional sculptable [FiltekZ250 (FZ)], flowable [Filtek Ultimate Flow (FUF)] and polyacid-modified [Twinky Star Flow (TS)] RBCs, and four-millimeter-thick samples of flowable bulk-fill [Filtek Bulk Fill Flow (FBF), Surefil SDR (SDR)] and sculptable fibre-reinforced [EverX Posterior (EX)] RBCs were prepared in an eight-millimeter-deep mold. The RBCs temperature was pre-set to 25, 35 and 55°C. The RBCs were photopolymerized with the recommended and its double exposure time. The DC at the top and bottom was measured with micro-Raman spectroscopy. Data were analyzed with ANOVA and Scheffe post-hoc test (p<0.05). RESULTS: The differences in DC% between the top/bottom and the recommended/extended exposure time were significant for the materials, except SDR (64.5/63.0% and 67.4/63.0%). FUF (69.0% and 53.4%) and TS (64.9% and 60.9%) in 2mm provided higher DC% at the top and bottom with the recommended curing time, compared to the other materials, except SDR. Pre-heating had negative effect on DC at the bottom in flowable RBCs (FUF: 48.9%, FBF: 36.7%, SDR: 43%, TS: 54.7%). Pre-heating to 55 °C significantly increased the DC% in fibre-reinforced RBC (75.0% at the top, 64.7% at the bottom). SIGNIFICANCE: Increased exposure time improves the DC for each material. Among bulk-fills, only SDR performed similarly, compared to the two-millimeter-thick flowable RBCs. Pre-heating of low-viscosity RBCs decreased the DC% at the bottom. Pre-heating of fibre-reinforced RBC to 55°C increased the DC% at a higher rate than the extended curing time.