Discoloration of fiber-reinforced composite resin disc for computer-aided design/computer-aided manufacturing after immersion in coffee and curry solutions.

The purpose of this study was to clarify the discoloration of fiber-reinforced composite resin (FRC) disc materials. The color differences (ΔEs) of three CAD/CAM disc materials, FRC with different fiber orientations, composite resin, and polyether-ether-ketones were evaluated after month-long immersion in water, coffee, and curry. The ΔEs of all materials after coffee and curry immersion increased with increasing immersion periods, while those after water immersion barely increased. FRC exhibited a smaller color difference and water sorption value than composite resin and a greater color difference and water sorption value than polyether-ether-ketones. The ΔEs after coffee immersion were significantly correlated with the water sorption value. The ΔE of FRC with fiber orientations perpendicular to the surface was greater than that of FRC with fiber orientations parallel to the surface, likely due to greater exposure of the matrix-fiber interface. This result suggested that the fiber orientations of FRC affected the discoloration.

Comparison of the accuracy of different handheld-type scanners in three-dimensional facial image recognition.

PURPOSE: Handheld-type scanners are widely used in clinical practice. This study examined the accuracy of handheld-type scanners using plaster statues to assess their performance in facial recognition. METHODS: Twelve 4-mm zirconia balls as measuring points were attached to the facial portions of three types of plaster statue. Six digital facial images of each plaster statue were obtained using one of the following five handheld-type scanners: Artec Eva, Artec Spider, Bellus 3D FaceApp, SNAP, and Vectra H1. Four-millimeter spherical objects were manually placed at the measurement points on the scanned data generated using computer-aided design software and coordinate positions were measured using a contact-type high-resolution three-dimensional measurement device. Consequently, the discrepancy between the distance measured using the contact-type device and that measured using the handheld-type scanner was calculated. The scanning time, processing time, and deviation of the distance between the measuring points were analyzed using two-way analysis of variance and t-test with Bonferroni correction. RESULTS: The scanning and processing times ranged from 15.2 to 42.2 s and 20.7 to 234.2 s, respectively. Overall, 97% of all measured distances by Spider were within ±1.00% deviation; 79%, Vectra; 73%, Eva; 70%, Bellus; and 42%, SNAP. CONCLUSIONS: The performance of handheld-type scanners using plaster statues varied among the different scanners. The scanning time of Eva and the processing time of Bellus were significantly shorter than those of other scanners. Furthermore, Spider exhibited the best accuracy, followed by Eva, Vectra, Bellus, and SNAP.

Effect of thickness on color appearance of multilayer CAD/CAM composite resin blocks.

The aim of this study was to evaluate the effect of thickness on the color appearance and translucency parameter (TP) of multilayer CAD/CAM composite resin blocks. Four brands of A3-shade multilayer CAD/CAM composite resin blocks were examined (Katana Avencia, CERASMART Multi, KZR-CAD HR Block 4 E-va, and Block HC Hard AN). Six specimens of five thicknesses were prepared for each brand, yielding 120 specimens in total. CIEL*a*b* values were determined using a spectrophotometer against black and white backgrounds, and the TP was calculated. The color differences (ΔE00) between layers (cervical/middle/incisal) and brands for each thickness against the black background were calculated using the CIEDE2000 system. As a result, on the black background, L* of the incisal layer was greater while a* and b* were smaller than those of the cervical layer for all brands. The ΔE00 values between the cervical and middle layers (1.23-3.27) were smaller than those between the cervical and incisal layers (3.98-5.67) and those between the middle and incisal layers (3.14-5.92). TP decreased with increasing block thickness. Some TP differences between layers were significant, but they were less than 2.75. In conclusion, the color appearance of CAD/CAM blocks was significantly influenced by both the thickness and layer. L*a*b* decreased with thickness, and a negative exponential relationship between TP and thickness was observed for all layers and brands.

Effect of fiberglass orientation on flexural properties of fiberglass-reinforced composite resin block for CAD/CAM.

A fiberglass-reinforced composite resin (FRP) block using a plain woven fiberglass sheet for CAD/CAM has been introduced in dental practice. The aim of the present study was to evaluate the effects of the fiberglass sheet orientation on the flexural properties of an FRP block. The flexural properties of five types of fiberglass sheet-assigned specimens were examined using a three-point bending test. A one-way analysis of variance revealed that the orientation of fiberglass sheet significantly influenced the flexural strength, 0.2% yield strength, and flexural modulus. The values of the flexural properties of the FRP were the largest when the fiberglass sheets were perpendicular to the applied force, and the smallest when the fiberglass was parallel to the same. The flexural properties of the FRP block were anisotropic and they were significantly influenced by the orientation of fiberglass sheet.

Effects of number of metal restorations and mandibular position during computed tomography imaging on accuracy of maxillofacial models.

PURPOSE: Computed tomography (CT) imaging for three-dimensional (3D) printed models may improve the quality of surgical preoperative plans. Although metal objects can cause artifacts in CT images, integration of CT and digital dental arch imaging may solve this problem. The present study aimed to evaluate effects of the number of metal restorations and mandibular position during CT imaging on accuracy of reproduced models. METHODS: Stereolithography datasets from three sets of dental models having different numbers of metal restorations were obtained using a laboratory digitizing device (control) and CT equipment (nonintegrated data). CT scanning was performed under two conditions: intercuspal position (closed) and separated using paraffin wax (open). Nonintegrated data after metal artifact removal were separated into maxillary and mandibular dentition groups. The occlusal part of the control dentition and nonintegrated data were superimposed and integrated (integrated data). The root mean square (RMS) between the control and stereolithography data was calculated and analyzed with three-way analysis of variance and t-test with Bonferroni correction. RESULTS: Increasing numbers of metal restorations resulted in increase in metal artifacts and RMS values. Moreover, the RMS of the closed dataset was significantly greater than that of the open dataset because of the creation of artificial occlusal surfaces. The RMSs of the integrated datasets were significantly smaller than those of the nonintegrated datasets, except for the open model without metal restorations. CONCLUSIONS: Accuracies of reproduced maxillary and mandibular models decreased with increasing numbers of metal restorations and in the closed mandibular position during CT scanning.

Discoloration of various CAD/CAM blocks after immersion in coffee.

OBJECTIVES: This study evaluated color differences (ΔEs) and translucency parameter changes (ΔTPs) of various computer-aided design/computer-aided manufacturing (CAD/CAM) blocks after immersion in coffee. MATERIALS AND METHODS: Eight CAD/CAM blocks and four restorative composite resins were evaluated. The CIE L*a*b* values of 2.0 mm thick disk-shaped specimens were measured using the spectrophotometer on white and black backgrounds (n = 6). The ΔEs and ΔTPs of one day, one week, and one month immersion in coffee or water were calculated. The values of each material were analyzed by two-way ANOVA and Tukey's multiple comparisons (α = 0.05). The ΔEs after prophylaxis paste polishing of 1 month coffee immersion specimens, water sorption and solubility were also evaluated. RESULTS: After one month in coffee, ΔEs of CAD/CAM composite resin blocks and restorative composites ranged from 1.6 to 3.7 and from 2.1 to 7.9, respectively, and ΔTPs decreased. The ANOVA of ΔEs and ΔTPs revealed significant differences in two main factors, immersion periods and media, and their interaction except for ΔEs of TEL (Telio CAD, Ivoclar Vivadent). The ΔEs significantly decreased after prophylaxis polishing except GRA (Gradia Block, GC). There was no significant correlation between ΔEs and water sorption or solubility in water. CONCLUSIONS: The ΔEs of CAD/CAM blocks after immersion in coffee varied among products and were comparable to those of restorative composite resins. The discoloration of CAD/CAM composite resin blocks could be effectively removed with prophylaxis paste polishing, while that of some restorative composites could not be removed.

Color stability of adhesive resin cements after immersion in coffee.

OBJECTIVES: Marginal discoloration of luting cement may affect the appearance of esthetic restorations. This study evaluated the color stability of current adhesive resin cements after immersion in coffee. MATERIALS AND METHODS: Four dual-cured resin cements (Clearfil SA cement Automix Universal, Maxcem Elite Clear, Maxcem Elite Yellow, and RelyX Unicem2 Automix A2) and two chemical-cured resin cements (Super-Bond C&B Clear and Super-Bond C&B Esthetic) were examined. The CIE L*a*b* of 2.0-mm-thick disc-shaped specimens was measured using a spectrophotometer on a white background (n = 6). The color differences (∆E) after 1-day and 1-week immersion in 37 °C water or coffee were analyzed by two-way ANOVA by selecting immersion solution and product as main factors, followed by Tukey's HSD test (α = 0.05). Water sorption and solubility were also evaluated. RESULTS: The two-way ANOVA of the ∆Es suggested that the two main factors and their interaction were significant. The ∆Es after coffee immersion were significantly greater than those after water immersion, except for Super-Bond C&B Esthetic. The ∆Es after water immersion were not significantly different among the products; those of Maxcem Elite Clear and Maxcem Elite Yellow after coffee immersion were significantly greater than the others. The water sorption and solubility significantly correlated with the ∆Es. CONCLUSIONS: The ∆Es of the adhesive resin cements examined after 1-week coffee immersion were significantly different among the products. The product showing greater water sorption and solubility displayed greater color change. CLINICAL RELEVANCE: Adhesive resin cements should be carefully selected when the marginal appearance of the ceramic restoration is important.

Mechanical properties of composite resin blocks for CAD/CAM.

This study compared commercial composite resin blocks with one ceramic block for use in computer-aided design/computer aided manufacturing (CAD/CAM). Four composite resins, one composite ceramic, and one feldspar-ceramic block were investigated. Flexural strength (FS), flexural modulus (FM), and Vickers hardness (VH) were determined under three conditions: dry storage; immersion in water at 37°C for 7 days; and immersion in water at 37°C for 7 days followed by 10,000 thermocycles. After dry storage, FS ranged from 127 to 242 MPa, FM from 9.6 to 51.5 GPa, and VH from 64 to 455. Two-way ANOVA was performed for FS, FM and VH followed by Tukey's multiple comparison (α<0.05). Results demonstrated that the materials degraded after water immersion and thermocycling, but their properties were within the acceptable range for fabrication of single restorations according to the ISO standard for ceramics (ISO 6872:2008).

Effect of immersion time of restorative glass ionomer cements and immersion duration in calcium chloride solution on surface hardness.

OBJECTIVES: The objective of this study was to evaluate the effect of immersion time of restorative glass ionomer cements (GICs) and immersion duration in calcium chloride (CaCl2) solution on the surface hardness. METHODS: Two high-viscosity GICs, Fuji IX GP and GlasIonomer FX-II, were selected. Forty-eight specimens were randomly divided into two groups. Sixty minutes after being mixed, half of them were immersed in a 42.7wt% CaCl2 solution for 10, 30, or 60min (Group 1); the remaining specimens were immersed after an additional 1-week of storage (Group 2). The surface hardness of the specimens was measured and analyzed with two-way ANOVA and the Tukey HSD test (α=0.05). The surface compositions were examined using energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. RESULTS: The surface hardness of Group 1 significantly increased as the immersion duration in CaCl2 increased; that of Group 2 significantly increased only after 60-minute CaCl2 immersion. After CaCl2 immersion, the amounts of Ca increased as the immersion duration increased. The surface hardness after CaCl2 immersion significantly correlated with the amount of Ca in Group 1, but not in Group 2. The binding energy of the Ca2p peak was similar to that of calcium polyalkenoate. These findings indicated that the Ca ions from the CaCl2 solution created chemical bonds with the carboxylic acid groups in the cement matrix. SIGNIFICANCE: Immersion of GICs in CaCl2 solution at the early stage of setting was considered to enhance the formation of the polyacid salt matrix; as a result, the surface hardness increased.

Fluoride release and mechanical properties after 1-year water storage of recent restorative glass ionomer cements.

OBJECTIVES: The objective of this study was to evaluate the relationships between fluoride release and mechanical properties after 1-year water storage of five recent restorative glass ionomer cements (GICs). MATERIALS AND METHODS: Five GICs, FujiIX GP EXTRA (FEX), FujiIX GP (FIX), GlasIonomer FX-II (GFX), Ketac Molar Easymix (KME), and Riva Self Cure (RSC), were examined. Cumulative fluoride release, compressive strength, and surface hardness were measured up to 1-year storage (n = 5), and analyzed with one-way or two-way ANOVA and Tukey HSD test (α = 0.05). Elemental compositions before and after 1-year storage were also examined (n = 3). RESULTS: The amounts of fluoride release were significantly different among the products. The highest amount of fluoride release occurred during the first day. Then, the amount of fluoride release rapidly decreased and still continued until 1-year storage. Compressive strengths indicated that two main factors were significant (GFX < FEX = RSC < FIX < KME; 1 day < 1 week = 1 month = 3 months = 6 months = 1 year), but surface hardness showed a slightly different tendency (GFX = RSC < FEX = FIX = KME; 1 year < 1 day < 1 week = 1 month = 3 months = 6 months). Significant correlation was found between decrease of silicon and decrease rate of the surface hardness. CONCLUSIONS: Fluoride releases were detected up to 1-year storage, but the mechanical properties slightly decreased due to decrease of Si after 1-year storage. Elution of Si instead of fluoride release was considered more critical to deteriorate the mechanical properties of GICs. CLINICAL RELEVANCE: Fluoride released for 1-year water storage will contribute to secondary caries prevention. The amount of fluoride release did not affect these mechanical properties. These results indicate the usefulness of these GICs.

Effect of calcium chloride solution immersion on surface hardness of restorative glass ionomer cements.

The objective of this study was to evaluate the effect of the concentration of calcium chloride (CaCl2) solution on the surface hardness of restorative glass ionomer cements (GICs). Two high-viscosity GICs, Fuji IX GP and GlasIonomer FX-II, were immersed in several concentrations of CaCl2 solution for 1 day and 1 week. The immersed specimen surfaces were evaluated using microhardness testing, grazing incidence X-ray diffraction, and energy-dispersive X-ray spectroscopy. Immersion in a higher concentration of CaCl2 solution produced a greater increase in the surface hardness. No crystalline substance was observed on the immersed surface. Calcium ions were selectively absorbed in the matrix of the GIC surface after immersion. They reacted with the non-reacted carboxylic acid groups remaining in the cement matrix. These reactions were considered to cause an increase in the surface hardness of the GICs.

Effects of the space for wash materials on sulcus depth reproduction with addition-curing silicone using two-step putty-wash technique.

Aim of this study was to investigate effects of space thickness and consistency of wash materials on sulcus depth reproduction with silicone impressions, low (L), medium (M), and very high consistency (VH), using two-step putty-wash technique. Impressions were taken from truncated cones with 50-, 100-, or 200-µm-wide sulci, using the combinations L+VH or M+VH and different space thickness for wash materials: 2 mm (ST2), 1 mm (ST1), and approximately 25 µm (ST0.025). Sulcus depth reproduction tended to increase with increasing sulcus width. Sulcus reproduction of ST0.025 was deeper than those of the other groups. At 100- and 200-µm sulcus widths, sulcus reproductions of ST1 and ST2 with L+HV were deeper than with M+HV. Regardless of consistency, the thin spacer produced deep reproduction. Adequate 0.5 mm sulcus reproductions were obtained with 100 and 200 µm wide sulci and 1- and 2-mm spacer widths, combined with low consistency impression material.