Do high translucency zirconia shades contribute to the degree of conversion of dual-cure resin cements?

OBJECTIVE: The opacity of the zirconia ceramic restoration may influence the degree of conversion (%DC) of dual-cured resin cements. The aim of this study was to evaluate the degree of conversion of resin luting agents photocured under different high translucency zirconia shades. The opacity of each ceramic shade was evaluated. METHOD AND MATERIALS: The opacity percentage of Lava Frame and three Lava Plus High Translucency Zirconia ceramic shades (W1, A2, and B4) was determined. A spectrophotometer MiniScan was used to measure the opacity percentage of each specimen (0.7 mm thick) and then the opacity was calculated. Specimens from three different resin cements (Panavia F2.0, RelyX Unicem 2 Automix Self-Adhesive, and PermaFlo DC) were prepared with 100-µm thickness. The specimens were photocured according to the manufacturers' instructions under a ceramic block (0.7 mm thick). Specimens photocured without the ceramic block were used as control. Fifteen groups (n = 3) were evaluated. Micro-ATR/FTIR (micro-attenuated total reflectance/Fourier-transformed infrared spectroscopy) spectrometry was used to evaluate the extent of polymerization of all specimens after 24 hours. The %DC was determined using experimentally polymerized versus maximally polymerized composite. RESULTS: The opacity percentages (mean ± SD) of W1, Lava Frame, A2, and B4 ceramics were 72.41% ± 0.04%, 74.24% ± 0.09%, 77.63% ± 0.11%, and 78.17% ± 0.12%, respectively. There was a statistically significant difference in %DC among the different cements investigated (P = .003) and a statistical difference in %DC was also found among the different ceramic shades studied (P = .030). For the Lava Frame and A2 ceramic blocks, the resin cements tested presented the lowest %DC except for the RelyX Unicem resin cement. CONCLUSIONS: The %DC of RelyX Unicem 2 cement under low zirconia opacities (W1 and Lava Frame) was greater compared to high zirconia opacities (A2 and B4). For the Panavia F2.0 cement, no effect on the %DC under different high translucency shades was observed. The highest %DC of PermaFlo cement was exhibited when the ceramic shade W1 was used. CLINICAL IMPLICATIONS: Dual-cured resin cements exhibited different degrees of conversion depending on the opacity of the zirconia restoration. However, different brands demonstrated higher or lower dependency of the light transmittance on their degree of conversion.

The influence of LED irradiance on the degree of conversion of resin luting agents under translucent zirconia.

This study aimed to evaluate the effect of different LED irradiance levels on the degree of conversion (DC) of dual-cured resin luting agents photocured through a high-translucency zirconia disc. Fifty-four disc specimens (approximately 0.1 × 6.0 × 6.0 mm) were prepared using 3 dual-cured resin luting agents (Panavia F 2.0, RelyX Unicem 2 Automix, and Calibra). Eighteen groups (n = 3) were evaluated. Test specimens were photocured through a 0.7 × 10.0-mm, high-translucency zirconia disc for 20 seconds using 1 of 3 different LED irradiances (mean output of 855, 1330, or 1750 mW/cm2 after 3 consecutive measurements with an LED radiometer). Specimens photocured directly, without a zirconia disc, were used as controls. Microattenuated total reflectance/Fourier-transform infrared spectroscopy was used to evaluate the extent of polymerization of all specimens prior to curing (baseline) and 24 hours after curing. Data were analyzed by 3-way analysis of variance and Tukey multiple comparisons test (α = 0.05). The RelyX Unicem 2 Automix and Panavia F 2.0 specimens showed no statistically significant difference in the mean DC after the use of different LED irradiance levels (P = 0.15 and P = 0.91, respectively) or when photocured with or without the use of a zirconia disc (P = 0.56 and P = 0.86, respectively). The Calibra specimens cured at the lowest irradiance level (855 mW/cm2) presented a significantly lower mean DC (P = 0.001). However, there was no statistically significant difference in the mean DC values when Calibra was photocured directly or through a zirconia disc (P = 0.33). The interpositioning of a high-translucency zirconia material did not reduce the DC of the tested resin luting agents compared to directly irradiated resin luting agents. The influence of different LED irradiance levels on the DC of dual-cured resin luting agents was material dependent.

Surface Roughness of Methacrylate- and Silorane-Based Composites After Finishing and Polishing Procedures.

OBJECTIVE: To compare the effect of surface finishing and polishing protocols on the surface roughness (Ra) of methacrylate-based and silorane-based resin composites. METHODS AND MATERIALS: Fifty specimens (5 mm x 2 mm) of each composite material were prepared using a split mold: Filtek™ Supreme Ultra (3M ESPE), Tetric EvoCeram® (Ivoclar Vivadent), Tetric Ceram™ HB (Ivoclar Vivadent), and Filtek™ LS Low Shrink (3M ESPE). Specimens were divided into five groups (n = 10) according to the following procedures: G1 - 15-µm fine diamond bur (FDB); G2 - 15-µm FDB followed by a 20-fluted tungsten carbide bur; G3 - 15-µm FDB followed by diamond-impregnated micropolishing points (D-FINE Double Diamond Polishing System, Clinician's Choice); G4 - 15-µm FDB followed by diamond-impregnated micropolishing points (Flame Point Pre-polisher and Shine, Brassseler USA); and G5 - 15-µm FDB followed by the application of a surface sealer (PermaSeal®, Ultradent Products, Inc.). Ra was measured in three different regions using a surface profilometer (Mitutoyo Surfest SJ-210, Mitutoyo America). RESULTS: Multiple comparisons were obtained using a one-way ANOVA with Tukey's B rank order test ( = 0.05). No significant differences in Ra were observed among the resin composites tested in the same condition. The use of a FDB generated the highest roughness values, while the use of a surface sealer resulted in the lowest roughness values for all resin composites tested (P < .05). No significant difference in Ra was observed between the use of a multi-fluted carbide bur and the rubber point D-FINE Double Diamond Polishing System for all resin composites tested.

Quality and Conservative Approach to Class I Resin Composite Restorations.

Advances in technology and adhesive dentistry have allowed practitioners to achieve long-term restorative results with minimal damage to tooth structures. The use of bonded restorations in restorative dentistry, including placement of resin composite restorations, has largely replaced the use of amalgam. The clinical case presented describes a technique utilizing minimal cavity preparation aimed at improving the quality and longevity of a Class I resin composite restoration. The procedure includes the use of an occlusal index to restore the tooth back to its original contour and anatomy. Other factors discussed are the use of MMP inhibitors, new advances in bonding agents, proper light-curing technique, and minimal finishing and polishing of the restoration.

Effect of surface treatments on the bond strength of self-etching adhesive agents to dentin.

The aim of this study was to investigate the influence of different surface treatments on the shear bond strength (SBS) of self-etching adhesive systems to dentin. Ninety freshly extracted noncarious human molars were sectioned mesiodistally and embedded in chemically cured resin with the buccal or lingual surfaces facing upward. Superficial dentin was exposed, and specimens were randomly assigned to 3 groups, according to the self-etching adhesive system utilized: Clearfil SE Bond (2-step), Scotchbond Universal (1-step), and Clearfil S³ Bond Plus (1-step). These groups were assigned to 5 subgroups (n = 12), according to the following treatments: G1, distilled water (control); G2, 35% phosphoric acid gel; G3, ultrasonic vibration; G4, sandblasting; G5, pumice slurry. For the 1-step self-etching adhesives, no significant differences in SBS values were observed between the different surface treatment groups and their control subgroup (P > 0.05). For the 2-step adhesive, mean values were significantly higher in the ultrasonic vibration and pumice-treated groups than in the control subgroup (P < 0.05). Overall, the use of vibration resulted in superior mean SBS values to dentin for all adhesives tested, although the values were not always significantly higher.

Effect of Finishing Procedures on the Surface Roughness of Resin-modified Glass-Ionomer Materials.

This study examined the influence of finishing procedures on the surface roughness of different formulations of resin-modified glass ionomers (RMGIs) available in capsules compared with standard resin composites (RCs). Disc samples of three RMGIs and two RCs were fabricated using a metal mold (5 mm x 1.5 mm). Samples were randomly divided into seven groups (N = 10) and subjected to finishing and polishing procedures using a combination of carbide or diamond burs, followed by either rubber points or aluminum-oxide discs. Three different regions of each sample were analyzed using a contact profilometer to determine the average roughness (Ra). The main surface roughness was calculated using a two-way analysis of variance (ANOVA) and the Bonferroni correction for multiple comparisons. A dual-stage combination of a fine carbide bur followed by the use of the finest two grits of aluminum-oxide discs was found to produce the smoothest finished and polished surface. the smoothest surfaces were found to be on the two RCs and one of the RMGIs.

Effect of artificial aging on the surface roughness and microhardness of resin-based materials.

This study sought to verify the effects of aging on the surface roughness (Ra) and microhardness (Knoop hardness number [KHN]) of resin-based restorative materials protected with a surface sealer. Disc specimens of 2 resin-modified glass ionomers (RMGIs) and 1 composite resin (CR) were fabricated in a metal mold. Specimens of each material were divided into 1 group that was covered with surface sealer and 1 group that was not. Both groups of each material were then subdivided according to whether they were stored (aged) in cola or distilled water. Surface roughness and KHN values were obtained from each specimen before and after storage. After aging of the specimens, significantly higher Ra values were observed in the 2 RMGIs when they were not covered with a surface sealer, while the CR was not affected. The KHN values varied by materials and storage conditions (with and without a surface sealer). All the groups with a surface sealer exhibited increased Ra values after aging.

Current all-ceramic systems in dentistry: a review.

This article describes the ceramic systems and processing techniques available today in dentistry. It aims to help clinicians understand the advantages and disadvantages of a myriad of ceramic materials and technique options. The microstructural components, materials' properties, indications, and names of products are discussed to help clarify their use. Key topics will include ceramics, particle-filled glasses, polycrystalline ceramics, CAD/CAM, and adhesive cementation.

Clinical evaluation of silorane-based and dimethacrylate-based resin composites: 1-year follow-up.

This study sought to evaluate the 1-year clinical performance of silorane-based and dimethacrylate-based Class II resin composite restorations using 2 bonding strategies. Eighty-two restorations were placed in 32 patients (median age 37 years) by a single operator. Only Class II restorations were included. Each patient received 1-2 pairs of resin composite restorations with both restoration materials. Between-group comparisons were made using an adjusted chi-square test and an adjusted McNemar's chi-square test to analyze the intrasystem data (α = 0.05). Both systems demonstrated acceptable clinical performance after 1 year.

Effect of preheating on microhardness and viscosity of 4 resin composites.

OBJECTIVE: This study was undertaken to determine the effect of temperature on the microhardness and viscosity of 4 resin composite materials. METHODS: To investigate microhardness, samples of each of the 4 composite materials, prepared by standard insertion of resin into prefabricated moulds, were divided into 2 groups (n = 10 per group). On the first group, the resin composite materials were inserted into the moulds at room temperature and cured. On the second group, the resin composite materials were pre-heated in a heating device, inserted into the moulds and immediately cured. Microhardness after curing (both immediately and after 24 hours of storage) was determined (using a 300 g load applied for 10 seconds) and averaged for 5 randomly selected points on the top and bottom surfaces of each sample. To investigate viscosity, 0.5 g samples of room temperature or preheated resin composite (n = 15 per group) were placed under a 454 g load for 45 seconds before light-curing (40 seconds). After curing, each sample was photographed and the surface area calculated. Data were analyzed by t tests or one-way analysis of variance and Tukey's test. RESULTS: Preheating the resin composites increased the microhardness and decreased the viscosity of the samples. Filtek Supreme Ultra resin composite had the highest mean microhardness, and Vit-l-escence resin composite had the lowest viscosity. CONCLUSIONS: The effects of preheating resin composites may allow easier placement of restorations and greater monomer conversion.

Influence of ceramic shades on surface hardness of different resin cements.

OBJETIVES: The aim of this study was to evaluate the effect of different ceramic spacer shades on the Knoop hardness (KH) of dual-cure resin cements (RelyX ARC RLX, 3M ESPE; Variolink II VLK, Ivoclar Vivadent) cured for 20 seconds with an LED light-curing unit. MATERIALS: Eight groups (n equals 15) were tested as follows: RelyX Control (light-cured without ceramic spacer); RelyX-2M2 ceramic spacer; RelyX-5M3 ceramic spacer; RelyX self-cured. Similar conditions were used with Variolink II cement. A microhardness tester was used to measure the KH values. Specimens were subjected to five 50 g/15 s indentations following curing at 0, 1, 2, 3, 4, 6, 24, 168, and 336 hours in order to determine the point at which the cements reach the maximum KH values. RESULTS: Control groups exhibited significantly higher KH values than the other groups (P less than 0.001) at 0 h following light curing. The KH values for RelyX-2M2 were not significantly different than the control group (P greater than 0.05) after 336 hours. All groups tested with 5M3 spacers had KH values that were not significantly different from the groups with self-cure mode, P greater than 0.05. The KH values for RelyX self-cure cement were significantly higher than Variolink II self-cure, P equals 0.003. RelyX-2M2 had KH values that were not significantly different from that of Variolink-2M2, P greater than 0.05. CONCLUSIONS: Ceramic spacer shades have tremendous effect on the KH values of RelyX and Variolink II. Darker ceramic shades (5M3 spacers) interfere with the absorption of light by the cements tested. In addition, the chemical portion in the self-cured mode is not sufficient to achieve optimum microhardness.

Comparison of mechanical properties of five commercial dental core build-up materials.

OBJECTIVE: This study aimed to evaluate and compare the mechanical properties of five commercial core materials using fracture toughness (FT), Knoop hardness number (KHN), diametral tensile strength (DTS), and dynamic elastic moduli (DEM). METHODS: Composite material specimens were produced (Rock Core, CosmeCore, ParaCore, MultiCore Flow, and Filtek Supreme Plus). The FT test (n = 15) was performed using notchless triangular prism (NTP) specimens. FT was determined using an Instron testing machine. KHN (n = 3) was evaluated using three indentations applied on each specimen. DTS test (n = 15) was measured using an Instron testing machine. The density. of the specimens (n = 3) was determined by water displacement method. Dynamic Young's, shear moduli, and Poisson's ratio (n = 3) were measured by an ultrasonic method. Statistical analysis was conducted using ANOVA and a Tukey B rank order test (P = 0.05). RESULTS: Rock Core presented the lowest FT values. Filtek Supreme Plus and CosmeCore exhibited significantly higher KHN values than the rest of the materials. CosmeCore had the highest DTS value, which was statistically significant only compared to Rock Core. For DEM, Filtek Supreme Plus exhibited significantly higher Young's and shear moduli than the rest of the materials (P < 0.05). CONCLUSIONS: Results demonstrated significant differences in the FT, KHN, and DTS values of the core build-up materials tested. According to the elastic behavior of the core composite materials, Rock Core had the lowest Young's values.

Effect of ceramic shade on the degree of conversion of a dual-cure resin cement analyzed by FTIR.

OBJECTIVES: The aim of this research was to evaluate the degree of monomer conversion of different resin cement shades when photocured under different feldspathic ceramic shades. The photocuring time was also evaluated as well as the translucency of each ceramic shade. METHODS: Three VITA VM7 ceramic shades (Base Dentin 0M1, Base Dentin 2M2 and Base Dentin 5M3) were used to determine the translucency percentage. A spectrophotometer MiniScan was used to measure the opacity percentage of each specimen (2-mm-thick) and then the translucency was calculated. To measure the degree of conversion (DC), the resin cement (Variolink II; A3 Yellow and transparent) specimens (thickness: 100 µm) were photocured under a ceramic block (2-mm-thick) for 20 or 40s. Specimens photocured without the ceramic block were used as control. Sixteen groups (n=3) were evaluated. Micro-ATR/FTIR spectrometry was used to evaluate the extent of polymerization of all specimens after 24h. The %DC was calculated of experimentally polymerized versus maximally polymerized composite. RESULTS: The translucency percentages of 0M1, 2M2 and 5M3 ceramics were 12.41 (1.02)%, 5.75 (1.91)% and 1.07 (0.03)%, respectively. The %DC of both resin cement shades cured under ceramic 5M3 was significantly lower than the other groups (p<0.05). The %DC of 0M1 groups exhibited no significant difference from 2M2 groups (p>0.05), with the exception of the transparent cement photocured for 40s. CONCLUSION: Photocuring under 2mm ceramic showed that the increase in chroma saturation significantly decreased Variolink II resin cement %DC (100-µm-thick).

In vitro shear bond strength of resin-based luting cements to dentin.

The aim of this study was to determine how resin cement, self-adhesive resin cement, and resin-modified glass ionomer cement affected shear bond strength to dentin. Sixty composite resin disks (3 mm in diameter x 3 mm in length) were prepared and divided into four groups (n = 15): Group 1, composite disk bonded to dentin with composite resin and a bonding agent; Group 2, composite disk bonded to dentin with a self-adhesive resin cement; Group 3, composite disk bonded to dentin with a different self-adhesive resin cement; and Group 4, composite disk bonded to dentin with a resin-modified glass ionomer cement. The composite resin was loaded into a syringe (internal diameter 3 mm), photocured in an oven, and cut into 3 mm slices with a low-speed saw. The samples were bonded to dentin per the manufacturer's instructions. All specimens were stored in distilled water (at 37 degrees C) for 24 hours. The shear bond strength test was conducted using a universal testing machine at a crosshead speed of 0.5 mm/min until failure. Conventional resin cement and a bonding agent exhibited significantly higher shear bond strength values than all other materials tested.

Diametral tensile strength of four composite resin core materials with and without centered fiber dowels.

This study evaluated the diametral tensile strength of composite resin core materials with and without fiber dowels. Eight groups were established (n = 20), four with composite resins and four with fiber dowels. Samples were tested using a universal testing machine and evaluated using scanning electron microscopy. One-way ANOVA and a Tukey B-rank order test (P = 0.05) indicated that the tensile values of two of the four composite resins decreased significantly when their matching fiber dowels were introduced.

Tissue engineering scaffolds for the regeneration of craniofacial bone.

Current strategies for skeletal regeneration involve the use of autogenous and allogenic bone grafts that may not always be available or safe to use. One alternative is to develop materials for use as scaffolds for the tissue engineering of bone. We created architecturally nanofibrous scaffolds using the electrospinning technique. These calcium phosphate- based materials are porous, have a large surface-area-to-volume ratio and can be used to deliver drugs, biologics or cells for tissue engineering applications. Bone-matrix proteins were also conjugated to the surface of a polymer network of polycaprolactone and poly(2-hydroxyethyl methacrylate) to create a material with enhanced cellular responses. This biomimetic strategy resulted in favourable cell-surface interactions that will likely enhance bone-matrix synthesis and regeneration. These collective advancements enable the development of innovative scaffolds for applications in tissue engineering and bone regeneration.