Objective: Natural tooth is composed of different structures with different optical properties. The aim of this observational study is to investigate the difference between the dentin color and the tooth color in CIE LAB* color coordinates and Delta E at incisal, middle and cervical thirds of maxillary anterior teeth . Methods: Sound natural extracted maxillary anterior teeth were used. Horizontal and vertical grooves were cut into enamel to be used as a reference for the measurement locations. Teeth were mounted on a dentoform with a bite registration material (Regisil, DENTSPLY). An image of the tooth was captured with an image-based spectrophotometer (Spectroshade Micro, MHT Optic Research). The thickness of enamel for each tooth was determined with a radiograph. Enamel was grinded to expose the facial dentin with a diamond bur. Then an image of the facial dentin was captured. The color of the tooth and the dentin was compared based on the CIE LAB color space at nine locations in the incisal, middle and cervical thirds. Color difference between the whole tooth color measurement and the corresponding dentin color measurement was calculated for each tooth. Results: 89 maxillary extracted anterior teeth were included in the study. Based on the paired-samples t-test, the data provided evidence that there was a significant difference between the color of dentin and the color of tooth (p<0.05 in each instance), except for the color parameter L* measured at the incisal third (p=0.9251). For parameters L* and b*, the results indicated that the mean color of dentin was greater than the mean color of tooth, while it was lower for parameter a*. Conclusion: The results of this study suggest that the dentin is higher in value than the tooth. In addition, the dentin color was higher in b* but lower in a* than the tooth color. The difference between the color of the tooth and the dentin was the least in the cervical third.

No description available.

P.ORTEGA-VERDUGO1 S.GUZMAN-AMSTRONG1 D. COBB1, D.V.DAWSON1, J.KOLKER1, M.HERNANDEZ1, J.WARREN 1University of Iowa, Iowa City, USA. NA

Objective: The aim of this pilot study is the evaluation and measurement of color stability from baseline until stabilization of color associated with bleaching and the dehydration and rehydration process of the teeth. Method: Six extracted intact human third molars were randomly selected, cleaned, and stored in artificial saliva at 370C. A custom positioning jig was fabricated for each tooth for reproducible color measurement. A baseline shade was recorded according to the Commission Internationale de l'Eclairage L*a*b* (CIE-L*a*b*) using a Minolta Chromameter CR-(200). Color measurement for all testing was taking at baseline, 15 min, 30 min, 2h, 12h and every 2 h thereafter until color stabilization occurred. Phase 1(dehydration-rehydration w/o bleaching): For dehydration, all teeth lightened and color stability occurred at 6 h. Rehydration of teeth to the baseline of color was achieved after 14 hours. Phase 2 (Effect of bleaching): An in-office bleach material (Zoom 25% HP) was applied to each tooth according to the Kwon technique (polyethylene wrap placed to cover the gel) for one hour. All comparisons were made to a Delta value of 2.6 (perceivable difference). Result: Phase 1: A mean äL*=-13.05(±15.62) was observed for tooth dehydration with no perceivable changes in chroma äa* and äb*. Phase 2: In-office bleaching produced dehydration and chroma changes when measured immediately after bleaching with a mean of äL*=-12.45(±2.4), äa*=0.31(±0.53), and äb*= 3.67(±1.76). After rehydration of bleached teeth, luminosity values (äL*) returned to normal and only chromaticity changes (äb#8727;) were observed with a mean of 4.77(%B11.91). Conclusion: Within the limits of this study, in-office bleaching produced dehydration and chroma changes, represented by äL* and äb*. Upon rehydration, the color changes were not as discernible. Further study will be conducted to determine the validity of these findings.

Objective: To compare the translucency of six different porcelains indicated for veneers, with various shades and opacities. Methods: 13mm diameter and 0.7mm thickness discs were fabricated for the following porcelains (A1 shade; n=5): Empress Esthetic (EE), e.maxPress (EP), InLine (IL) (Ivoclar Vivadent); VITA PM9 (VPM), Vitablocks MarkII (VMII) (Vita Zahnfabrik); Kavo Everest G-Blank (KEG) (KaVo Dental GmbH) and Lava Zirconia (LZ) (3M ESPE). IL and LZ respectively served as positive and negative controls. Groups with different shades (BL2, BL4, A1, B1), as well as high (HT) and low translucencies (LT), were fabricated for e.maxPress. The luminous reflectance (Y) and color coordinates (CIE L*a*b*) were measured with a colorimeter (CIE illuminant D65, 2-degree observer function) with the specimens placed on black and white backgrounds. Contrast ratios (CR = YB/YW) and translucency parameters (TP= [(LB* - LW*)2 + (aB* - aW*)2 + (bB* - bW*)2 ]1/2) were calculated. One-way ANOVA and post-hoc Tukey's HSD tests were used to analyze the data (α = 0.05). Results: Statistically significant differences in CR and TP were found among porcelains (P < .0001). The CR means in order of decreasing translucency were: VPM (0.15) > VMII (0.24), IL (0.25), KEG (0.26) > EP HTB1 (0.32), EE (0.34) > EP HTA1 (0.37), EP HTBL4 (0.37) > EP HTBL2 (0.43), EP LTA1 (0.47) > LZ (0.73). The TP means in order of decreasing translucency were: VPM (40.34) > VMII (33.66), KEG (33.52), IL (32.44) > EP HTB1 (27.96), EE (27.64) > EP HTA1 (26.59), EP HTBL4 (26.14) > EP HTBL2 (22.70), EP LTA1 (21.35) > LZ (10.43). Translucency of conventional feldspathic porcelain was comparable to that of machinable feldspathic porcelain. Pressable feldspathic porcelain presented the greatest translucency. Shade and thickness influenced lithium disilicate porcelain translucency. Conclusion: Various ceramics systems designed for porcelain veneers present various degrees of translucency.

Objectives: the hypothesis of this study was that different abutment substrates would not affect epithelial cell attachment and differentiation. Methods: 15 discs for each of 5 different materials (4 types of titanium and 1 type of zirconium) were flooded with a media containing human adenoid epithelial cells (hTERT). Cells were allowed to attach on the discs for 2 hours. The media was then collected, and remaining suspended cells counted, to determine number of attached cells. Surfaces were then flooded with fresh media, collected 24 hours later. Levels of 6 different pro-inflammatory cytokines contained in the media were measured for each disc, using a Luminex 100 IS system. Then, part of the discs was used for SEM observation of cell morphology. Another part of the discs was used for immuno-fluorescent microscopy, to observe the organization of the actin cytoskeleton, using phalloidin conjugated to a fluorophore to label the actin. The remaining discs were used to analyse alpha6-beta4 Integrin expression, using gel electrophoresis after isolation of mRNA and reverse PCR. Results: Number of attached cells was not statistically different for the 5 types of material. For the 5 materials, levels of cytokines IL-6, 8, 12 and TNF-alpha were similar and IL-1 and 10 were not produced in amounts large enough to be detected. Again, alpha6-beta4 Integrin expression was similar for the different surfaces. Actin Cytoskeleton organization was alike for the titanium surfaces, but cells seemed to be less spread on zirconium. SEM showed comparable cell morphology for the titanium surfaces, whereas no cell could be observed on zirconium. Conclusions: quantitatively, cell attachment and expression of alpha6-beta4 Integrin, IL-6, 8, 12 and TNF-alpha does not seem to be affected by the different surfaces. Nevertheless, attachment might be of lesser quality for zirconium.

OBJECTIVE: To evaluate the effects of different times and temperatures of coffee exposures on the color stability of three types of dental composites (DC). METHODS: Three types of DC were used to fabricate standardized discs (n=288; n=96/DC): microfill (Durafill VS), microhybrid (Z100TM), and nanofill (Estelite OMEGA) of shade A2. Each disc was 2mm in thickness and 9mm in diameter. After being light cured with a Quarts tungsten halogen (QTH) unit at the energy level recommended for each DC, discs were polished using sand paper under water irrigation. All samples were initially stored in an incubator in distilled water for 24-hours at 37 65ºC and each DC group was further divided into 6 subgroups (n=16/per group): 65ºC coffee, 37ºC coffee, 4ºC coffee, 65ºC distilled water, 37ºC distilled water, 4ºC distilled water (control group with water media). Baseline color was measured by spectrophotometer (Easy VITA shade compact) with color changes (ΔE*) recorded after 1-day, 3.5-days, and 7-days. The statistical analysis revealed no interactions between DC, temperature, and time of incubation and the main effects were examined using one-way ANOVA followed by the post-hoc Tukey’s HSD test or a Bonferroni adjustment (alpha=0.05). RESULTS: Mean (ΔE*) observed with coffee exposures for the microfill DC (11.58±6.37) was statistically significant higher than for the nanofill DC (10.64±6.77; p<0.001), and mean (ΔE*) for the nanofill DC was significantly higher than for the microhybrid DC (9.26±5.83; p<0.001). For all DC, mean (ΔE*) observed with coffee exposure at 65ºC (18.33±4.32) was significantly higher than at 37°C (7.03±2.05; p<0.001), and mean (ΔE*) at 37ºC was significantly higher than at 4ºC (6.11±2.67; p<0.001). Mean (ΔE*) after coffee exposure for 1 day (8.64±5.35) was significantly lower than for 3.5-days (11.07±6.50; p<0.001) and 7-days (11.76±6.84; p<0.001); while no difference was observed between 3.5-days and 7-days of incubation (p=0.0769). CONCLUSION: The findings of this study indicated that exposure time, temperature, and composite type affect the color stability of DC, with higher temperature affecting the color stability more than lower temperatures. Also, color stability was affected more by increasing the exposure time.

Objective: To determine the relationship between mineral density and microtensile bond strength of caries-affected dentin (CAD). Methods: Sixty-three extracted human molars with carious lesions and nine extracted sound human molars are collected and flattened to expose the dentin. Caries is removed using Caries Detector (Kuraray Medical, Tokyo, Japan) leaving a firm light pink stained dentin and then bonded with RBC (Z100, shade T, 3M ESPE, Germany) using an etch-and-rinse 3-step adhesive system (Optibond FL,Kerr, Orange, CA, USA). The bonded teeth are stored overnight at 37ºC before vertically sectioned with diamond saw blades (IsoMet 1000, Buehler Ltd., Lake Bluff, IL, USA). The sticks are then trimmed into dumbbell-shaped specimens with a cross-sectional area of 0.5 mm2 and a gauge length of 1 mm. Tensile testing is performed at a crosshead speed of 1 mm/min (Zwick Materials Testing Machine Z2.5/TN1S, Zwick, Ulm, Germany). X-ray microtomography was used to examine the fractured specimens (Micro-CAT II, Siemens Preclinical Solutions, Knoxville, TN) at maximum resolution of 27 microns. The mean mineral densities at the resin-dentin interface of the bonded specimens are calculated using a custom BMD (bone mineral density) analyzer software (Iowa City, IA, USA). Mineral density (image intensity) will be plotted against uTBS (MPa) to determine correlation between these two properties based on Spearman rank correlation test at 0.05 level of statistical significance. Results:There was a statistically significant relationship between µTBS and image intensity (p< 0.0001). However, the correlation coefficient was weak (0.31). Significant effect of the failure mode on the image intensity and the µTBS were observed (p < 0.0001). No significant difference in the mean image intensity was found between the 2 levels (p = 0.6519) and 3 levels of dye staining (p = 0.2531). Intra- and inter-examiner reliability was near perfect (0.99; 0.98) for mineral density measurements. Conclusion: Within the limits imposed in the experimental design, we concluded that the degree of mineralzation of CAD has an influence on its failure mode and µTBS. Positive increasing relationship was also found between CAD's failure mode and its µTBS. Additionally, no significant relationship was found between levels of dye staining and the degree of mineralization.

No description available.

Objective: To assess the effect of finishing and polishing direction on the marginal adaptation of resin-based composite restorations. Methods: Forty human molars were collected and sectioned along their mesio-distal axis. Buccal and lingual enamel surfaces were flattened and a triangular preparation (0.87mm deep and 3mm wide) representing two 30° bevels was achieved. Specimens (n=20/per group) were randomly assigned in groups and restored with two resin-based composite materials: a nanofilled (Filtek Supreme Ultra)(FSU) and a microhybrid (Point4)(PT4) and two finishing/polishing techniques: a series of Sof-Lex discs (SL) and a sequence of diamond bur/dark-orange SL/rubber polishers (HiLuster). On each specimen, both margins were finished and polished with the same technique, one from the resin-based composite to the tooth structure (C-T) and the other from the tooth structure to the resin-based composite (T-C). Replicas were made for FeSEM observation (200X) and quantitative margin analysis was performed based on four defined marginal quality criteria. Comparisons were made between polishing directions (paired-samples t-test, Wilcoxon signed-rank test), between resin-based composites and between polishing techniques (two-sample t-test and Wilcoxon rank sum test) Results: Significant differences were found between polishing directions (p<0.05). Data showed more continuous margins, less marginal irregularities and less gaps with the polishing direction C-T than T-C except for one group (FSU/SL) with marginally significant difference in gaps (p=0.0537). Differences between the two resin-based composites and the two polishing techniques seemed to be dependent on certain combinations of resin-based composite, polishing technique and polishing direction. Conclusion: Within the limitations of this in vitro study, polishing from resin-based composite to tooth structure (C-T) leads to better marginal adaptation than polishing from tooth structure to resin-based composite (T-C).