Effect of simplified or multi-step polishing techniques on roughness and color stability of resin composites.

PURPOSE: To evaluate the impact of simplified or multi-step polishing techniques on the roughness, color, and susceptibility to staining of different resin composites. METHODS: Discs (Ø6 mm x 2 mm) were obtained from different resin composites [nanofilled (Z350XT), suprananofilled (Estelite Omega), and nanohybrid (Forma)]. The specimens (n= 15) were submitted to a simplified protocol using abrasive discs (Sof-Lex) and spiral discs (Diacomp Plus Twist), or a multi-step protocol using abrasive discs (Sof-Lex), abrasive points (Jiffy), silicon carbide brush and felt disc with diamond pastes (Diamond Polish). The specimens were evaluated initially for roughness (Ra) and color (CIEL*a*b*, CIEDE 2000), after completing the polishing protocol, and after exposure to a coffee solution (pH= 5.01). The data were analyzed according to the variables, using generalized linear models, and the Friedman, Nemenyi, Kruskal-Wallis, Dunn, and Mann-Whitney tests (α= 0.05). RESULTS: The nanohybrid resin composite showed an increase in Ra following use of both polishing methods (P= 0.038). Both techniques promoted an increase in L* values after polishing; however, the general color changes (ΔEab and ΔE00) were greater after the multi-step polishing (P< 0.05). After immersion in coffee, the multi-step polished groups of the nanohybrid and suprananofilled resin composite showed higher L* values than the simplified polishing groups (P= 0.023), and the nanofilled resin composite showed higher ΔEab and ΔE00 values than the other resin composites, regardless of the polishing technique (P< 0.05). CLINICAL SIGNIFICANCE: The choice of the resin composite had a greater effect on roughness, color stability and susceptibility to staining than the polishing technique. However, luminosity after coffee staining was higher with the multi-step polishing technique.

Spectrophotometric assessment of the color stability of composite resins polished with different techniques.

This study aimed to use spectrophotometry to assess the color stability of composite resins polished with different polishing techniques and scanning electron microscopy (SEM) to evaluate the surface micromorphology of the specimens. In this in vitro experimental study, a total of 96 disc-shaped specimens were fabricated from microfilled (Renamel Microfill, shade SB3) and nanohybrid (Estelite Sigma Quick, shade BW) composite resins in bright white shades (n = 48). Each group was randomized into 1 control and 2 experimental subgroups (n = 16): no polishing (control), polishing with aluminum oxide discs (experimental), or polishing with diamond-impregnated spiral wheels (experimental). In each subgroup, half of the specimens were immersed in a coffee solution and the other half in a tea solution for 48 hours after finishing (control) or polishing (experimental). Spectrophotometry was used to measure the color of the specimens at baseline, after finishing, after polishing (experimental groups only), and after immersion in tea and coffee. The surface micromorphology of a randomly selected specimen from each subgroup was assessed under SEM. The color change (ΔE*) of the specimens between measurements was calculated and analyzed using 1-way, 2-way, and 3-way analyses of variance (ANOVAs) and the Tukey test. Both tea and coffee caused significant color change in the composite resin specimens, with specimens immersed in coffee undergoing significantly greater color change than those immersed in tea (P < 0.001; 2-way ANOVA). The nanohybrid composite specimens polished with polishing discs had a significantly greater color change than nanohybrid specimens polished with spiral wheels (P = 0.041). The Tukey test revealed that there was no overall significant difference between the 2 polishing techniques (P = 0.505), but both of these subgroups exhibited a significantly lower color change than the control group (P < 0.001). In general, SEM did not reveal substantial differences between the 2 polishing techniques, but specimens polished by spiral wheels appeared to have a smoother surface. All polished specimens demonstrated clinically acceptable mean color change values (ΔE* < 3.5). The type of coloring agent had a greater effect on color stability than either the polishing technique or type of composite resin, with coffee causing a greater color change than tea.

Effects of in-office bleaching agents on polished and unpolished nanofilled resin composite.

BACKGROUND: This study investigates the effects of in-office bleaching agents on the color change and surface roughness of nanofilled resin composite finished by various polishing procedures. METHODS: The authors made 108 specimens from nanofilled resin composite, and the finishing and polishing procedures were performed with either Sof-Lex (3M ESPE) or OneGloss (Shofu). The specimens were then immersed in tea or coffee solution for 1 week, after which in-office bleaching agents were applied (n = 9). After polishing and bleaching, the surface roughness was measured with a surface profilometer. The specimen color parameters were measured with the Commission Internationale de l'Eclairage L∗a∗b∗ system in 3 stages, namely after polishing, after staining, and at the end of the bleaching procedure. The total color changes (ΔEab∗) were calculated, and ΔEab∗ not exceeding 2.7 was considered a clinically acceptable threshold. RESULTS: The highest initial roughness value was observed on surfaces polished with OneGloss. In all groups, the surface roughness increased significantly after bleaching. For the Sof-Lex group specimens stained in both tea and coffee solutions, bleaching agent Opalescence Boost (Ultradent) reduced the color change value to 2.7 or less after bleaching. CONCLUSIONS: In-office bleaching agents increased surface roughness in all groups, especially on unpolished surfaces. However, surface roughness was at an acceptable threshold for the multistep polished group, Sof-Lex, after bleaching. Nanofilled resin composite staining can be partially reduced by in-office bleaching agents but not completely removed. PRACTICAL IMPLICATIONS: To reduce the increase in surface roughness of composite restorations due to bleaching, polishing should be applied before and after bleaching.

Comparison of Surface Roughness and Color Stability of Different Denture Characterizing Composite Resins: The Effect of Different Surface Treatments.

PURPOSE: This study aimed to investigate the effect of surface treatment and type of composite resin material on the color stability and surface roughness of different denture characterizing composites. MATERIALS AND METHODS: Two nanohybrids [Gradia Plus Gum, (GP) and SR Nexco Paste Gingiva, (SR)] and one microhybrid gingiva-colored composite resin [Amaris Gingiva, (AG)] were investigated. A total of 120 disk-shaped samples were prepared, 40 of each material. Samples were divided into two groups (n = 20) for each material according to the surface treatment applied: conventional polishing (control) and coated with a sealant in addition to the surface polishing. All groups were thermocycled. The surface roughness (Ra) was measured using a profilometer after thermal cycling. The samples were then divided into 2 subgroups (n = 10) and stored for 7 days in distilled water or coffee solution. Color differences (ΔE00 ) were calculated with a spectrophotometer. Results were evaluated with Kruskal-Wallis and Mann-Whitney U statistical analysis. RESULTS: The type of denture characterizing composite material and surface treatment method revealed statistically significant differences for the ΔE00 (after immersion both in coffee and distilled water) and the Ra values of denture characterizing composite (p < 0.001 for both). All sealed groups showed significantly higher Ra than the all polished groups. Both in the polished groups and the sealant applied groups, the GP had the highest mean Ra values (0.29 ±0.05 µm and 0.47 ±0.09 µm, respectively). It was followed by SR (0.23 ±0.06 µm and 0.41 ±0.10 µm, respectively), and AG groups (0.20 ±0.06 µm and 0.39 ±0.09 µm, respectively). According to the mean ΔE00 results, all composite groups showed significantly higher ΔE00 values immersed in coffee solutions compared to distilled water. In coffee solutions, the highest ΔE00 was observed in the polished GP (1.90 ±0.40), and the lowest ΔE00 was observed in the polished SR (0.97 ±0.36). The sealed groups showed higher ΔE00 than the polished groups, except for GP. CONCLUSIONS: The surface roughness value of sealant applied groups were significantly higher than those of the polished groups. The surface sealant application significantly increased the staining of all composite groups compared to conventional polishing, except for GP.

Do composite resin polishing systems damage enamel?

Finishing and polishing of composite resin restorations may cause damage to the bordering enamel. Although many studies have investigated the effect of polish on restorative materials, few have quantified the effect on bordering enamel. The objective of this study was to compare enamel loss surrounding composite restorations after finishing and polishing sequences. The null hypothesis was that there would be no difference in enamel loss between different finishing and polishing sequences. Class V preparations on the buccal and lingual surfaces of 15 extracted human molars were restored with a composite resin and assigned to 1 of 2 finishing and polishing sequences, so that each tooth underwent both sequences (n = 15 per sequence). In sequence 1, a tungsten carbide finishing bur and aluminum oxide polishing discs were used; in sequence 2, a diamond finishing bur, aluminum oxide-impregnated finishing cup, and diamond-impregnated polishing cup were used. Tooth surfaces were scanned with an optical scanner after preparation, finishing, initial polishing, and final polishing. The finishing and polishing scans were aligned to the preparation scan using Cumulus software. The depth of enamel surface loss was calculated and statistically analyzed (α = 0.05; paired t test). Most enamel loss (mean [SD]) resulted from the finishing step with the tungsten carbide bur (51.8 [21.3] µm) or diamond bur (43.3 [12.6] µm). Each polishing step increased mean enamel loss by only a few microns. There was no statistically significant difference between the 2 finishing and polishing sequences. The majority of enamel damage during finishing and polishing of composite resin restorations resulted from the finishing burs. Little enamel was removed by either of the tested composite resin polishing systems.

Effect of different polishing systems and staining solution on surface roughness and color stability of bulk fill resin composites.

PURPOSE: To evaluate the effect of polishing systems (discs or rubbers) on surface roughness (Ra) and color change (ΔE) of two bulk fill and one conventional resin composite after immersion in a dye solution. METHODS: 180 samples (10 mm x 2 mm) were separated into three groups: (1) Resin composite: Filtek One Bulk Fill (FO), Tetric N-Ceram Bulk Fill (TNC), Filtek Z350 XT (FXT) (n= 60); (2) polishing system: unpolished (control); aluminum oxide discs (Sof-Lex, AOD); cup-shaped abrasive rubber polishers (Astropol, CSA) (n= 20), and (3) immersion solutions: coffee or distilled water (n= 10). Immersion was under 5 mL of each solution for 3 hours daily, for 30 days. Measurement of Ra and ∆E was made considering two times: initial (after polishing) and final (after immersion), in addition to surface analysis by scanning electron microscopy at the end. Kruskal-Wallis, Mann-Whitney, and Dunn (α= 0.05) was used. RESULTS: For the unpolished samples after immersion in coffee, TNC (P= 0.007) showed lower ΔE than FXT and FO. For polished samples with CSA and immersed in coffee, TNC followed by FXT showed lower ΔE than in the absence of polishing. Polishing with AOD and immersed in coffee: FO had smaller ΔE than when not polished. For Ra, TNC and FO had lower values after using AOD, whereas for FXT lower Ra was noted with CSA. CLINICAL SIGNIFICANCE: The roughness and color stability of resin composites are mediated by the polished material, polishing system and dye solution. The best results were found for Tetric N-Ceram polished with aluminum oxide discs.

Effect of Additional Light Curing on Colour Stability of Composite Resins.

AIM: The objective of this study was to evaluate the effect of additional light curing on the colour stability of composite resins. MATERIALS AND METHODS: Four different composite resins-a nanofill, a nanohybrid, a microhybrid, and a bulk-fill composite resin-were tested. Eighty disc-shaped specimens were prepared from each material using either a quartz tungsten halogen or a light-emitting diode light source and were randomly divided into 2 groups according to the surface treatment: no polishing (nonpolished) or polishing with aluminum oxide discs (polished). Then additional light curing was applied to half of the specimens in each group. All specimens were immersed in coffee solution for 1 week. Colour was measured with a spectrophotometer at baseline and after 1 week of storage in coffee solution. RESULTS: Statistically significant differences in colour stability were observed in the restorative materials according to the composition of composite resin, the polishing protocol, and additional light curing, whilst there were no significant differences according to the light source. Additional light curing reduced discolouration in all groups tested. CONCLUSIONS: Additional light curing may be beneficial after finishing and polishing in order to maintain aesthetics and increase the resistance of composite resins to discolouration.

Discoloration of Resin Composites Induced by Coffee and Tomato Sauce and Subjected to Surface Polishing: An In Vitro Study.

BACKGROUND The purpose of this study is to evaluate and compare color stability of 3 resin based restorative materials when immersed into staining media at 0, 3, 30, 45, 60, and 75 days, and to assess the efficacy of surface polishing in reducing possible discoloration. MATERIAL AND METHODS Ninety composite discs were prepared in a custom-made mold (5 mm diameter and 2 mm thick) from 3 different light cured composites (Filtek™ Z250, Harmonize™, and G-aenial). Color differences of all specimens were measured by a spectrophotometer according to the CIE L*a*b* system. After baseline color measurements, 30 discs from each composite group were randomly divided into 3 subgroups of 10 specimens each. Subgroups (n=10) were immersed for 75 days into different staining solutions: coffee, tomato sauce, and distilled water (control). Solutions were changed every week and color measurements were repeated every 15 days. At day 75, color measurements of the specimens were performed before and after surface polishing with aluminum oxide discs. The experimental data were statistically evaluated using repeated measures one-way ANOVA test followed by Tukey's multiple pairwise comparison with a significance level of 5%. RESULTS Of the 3 composites, G-aenial reported the highest color change deviation when immersed into coffee (ΔE=8.674), and tomato sauce (ΔE=7.737) at day 75, followed by Harmonize that also exhibited a significant difference for coffee (ΔE=4.7) and tomato sauce (ΔE=3.8) when compared to distilled water. While Filtek™ Z250 did not show any significant difference between the 3 storage solutions (P>0.05). Only G-aenial had significant color change (P<0.05) after polishing with aluminum oxide discs for all tested samples, whereas Filtek™ Z250 and Harmonize presented no significant difference after surface polishing (P>0.05). CONCLUSIONS Under the tested experimental conditions, Filtek™ Z250, among the 3 resin-based composites, exhibited the highest color stability when subjected to coffee and tomato sauce as well. Whereas, G-aenial presented the highest color deviation when immersed in both staining media. Surface polishing effectively reduced coffee and tomato sauce discolorations for G-aenial's specimens and had no significant effect regarding Filtek™ Z250 and Harmonize.

Efecto de Diferentes Técnicas de Acabado y Pulido Sobre la Rugosidad de un Composite de Nanoparticulas / Effect of Different Finishing and Polishing Techniques on the Roughness of a Nanoparticle Composite

El objetivo fue comparar la rugosidad de un composite nanoparticulado con diferentes técnicas de acabado y pulido. Se obtuvieron 20 discos en conformadores ad-hoc en los que se insertó un composite nanoparticulado en capas de 2mm. Se activó cada incremento durante 30s con una intensidad de 1450 mw/cm2. Todas las probetas se pulieron con la secuencia completa de discos Sof-lex a velocidad media y luego se asignaron a uno de 4 grupos (n=5) tratados de la siguiente manera: G1: sin tratamiento extra; G2: con cepillos Astrobrush y JC-SICRA-G; G3: con pasta de diamantes Diamond Gloss aplicada con fieltro; y pasta de óxido de aluminio Poligloss y fieltro; G4: igual que G3 + cepillos (igual que G2). Las superficies se evaluaron con un perfilómetro óptico tridimensional. Se registró la rugosidad promedio (Ra) en tres puntos de cada espécimen, se consideró la Ra a la media de los tres registros obtenidos. Los datos se analizaron mediante ANOVA de una vía y prueba de Tukey para comparaciones múltiples. Los resultados obtenidos fueron: G1: 132,20nm (26,16); G2: 77,20 nm (20,64); G3: 78,74 nm (10,04); G4: 66,47nm (31,08). Se encontró diferencia estadísticamente significativa entre los grupos (P=0.0017); de las comparaciones múltiples surge que G1 presentó una rugosidad media significativamente mayor que los restantes. G1>G2 (P<0.01), G1>G3 (P<0,05), G1>G4 (P<0,01). En conclusión, el uso de sistemas anexos de pulido permite lograr mayor lisura superficial. El uso de más de un sistema complementario no mejora el resultado (AU)

Effect of Tooth-Whitening Procedures on Stained Composite Resins.

In this laboratory study, a composite resin was stained to a visibly discernible level using both coffee and red wine over 14 days (change was considered clinically noticeable and significant when ΔEab*≥2.7). Color change was measured at one, three, seven, and 14 days of staining. Although the nature of color change was different for the two staining solutions, the overall degree of staining (ΔEab*) rendered by either coffee or wine at each time interval was not significantly different ( p≥0.05). Four whitening protocols were applied to stained composites. Treatment included applications of distilled water (control), Crest Pro-Health [HD] toothpaste, Crest Whitestrips, Opalescence PF bleach (15%), and application of a fine pumice polishing (Preppies). HD toothpaste and Whitestrips were applied daily for 21 days, Opalescence was applied daily for 10 days, and polishing was applied once. Each of the whitening products, applied in a manner simulating at-home or in-office treatment, was effective in producing color improvements (lightening) over controls ( p<0.05), but none of the four treatments produced lightening that was significantly different from the other treatments ( p≥0.05). A comparison of final composite color with that measured at baseline showed that Opalescence returned composite color to an acceptable level following exposure to both staining solutions (ΔEab*<2.7), Whitestrips returned color close to baseline for wine-stained composites, and HD paste and polishing permitted residual stain to remain (ΔEab*≥2.7).

The effect of immediate and delayed polishing on the color stability of a composite resin.

Polishing techniques are known to enhance the longevity and appearance of composite resin restorations. However, the influence of the timing of polishing on the final results of a restoration is not well documented. The aim of this study was to determine the effect of immediate and delayed polishing on the color stability of a composite resin. Sixty composite resin specimens were fabricated and randomly divided into 2 groups according to immersion solutions: group 1, deionized water (control); and group 2, coffee (as staining solution). The groups were further divided according to polishing time periods (immediate, 1 day, 7 days, 14 days, and 21 days). The polishing was performed by 1 calibrated operator using a sequence of aluminum oxide discs with different granulations. Color measurements were assessed at baseline and after a 48-hour immersion in the assigned medium by a reflection spectrophotometer, according to CIE L*a*b* parameters. The data were submitted to an analysis of variance (ANOVA) and the post hoc Tukey test at a significance level of 0.05. The ANOVA showed that the immersion solutions had a statistically significant difference (α = 0.05) on color stability. The composite resin color stability was not influenced by the timing of polishing, and all subgroups showed clinically unacceptable discoloration after exposure to coffee. Thus, with regard to color stability, the timing of final polishing may be established according to the preferences of the clinician.

In vitro biofilm formation on resin-based composites after different finishing and polishing procedures.

OBJECTIVES: To evaluate the influence of surface treatments of different resin-based composites (RBCs) on S. mutans biofilm formation. METHODS: 4 RBCs (microhybrid, nanohybrid, nanofilled, bulk-filled) and 6 finishing-polishing (F/P) procedures (open-air light-curing, light-curing against Mylar strip, aluminum oxide discs, one-step rubber point, diamond bur, multi-blade carbide bur) were evaluated. Surface roughness (SR) (n=5/group), gloss (n=5/group), scanning electron microscopy morphological analysis (SEM), energy-dispersive X-ray spectrometry (EDS) (n=3/group), and S. mutans biofilm formation (n=16/group) were assessed. EDS analysis was repeated after the biofilm assay. A morphological evaluation of S. mutans biofilm was also performed using confocal laser-scanning microscopy (CLSM) (n=2/group). The data were analyzed using Wilcoxon (SR, gloss) and two-way ANOVA with Tukey as post-hoc tests (EDS, biofilm formation). RESULTS: F/P procedures as well as RBCs significantly influenced SR and gloss. While F/P procedures did not significantly influence S. mutans biofilm formation, a significant influence of RBCs on the same parameter was found. Different RBCs showed different surface elemental composition. Both F/P procedures and S. mutans biofilm formation significantly modified this parameter. CONCLUSIONS: The tested F/P procedures significantly influenced RBCs surface properties but did not significantly affect S. mutans biofilm formation. The significant influence of the different RBCs tested on S. mutans biofilm formation suggests that material characteristics and composition play a greater role than SR. CLINICAL SIGNIFICANCE: F/P procedures of RBCs may unexpectedly play a minor role compared to that of the restoration material itself in bacterial colonization.

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.

Implant surface roughness alterations induced by different prophylactic procedures: an in vitro study.

AIM: To evaluate surface roughness alterations at the smooth neck of dental implants after the use of eight different prophylactic procedures. MATERIALS AND METHODS: 50 tissue level implants (Institut Straumann AG, Basel, Switzerland) were used for the present investigation. The smooth collar of each implant was divided into two segments, each treated with one of eight cleaning procedures: use of a rubber cup (RCZ) or a brush (BZ) combined with an abrasive paste containing zirconium or a paste derived from perlite (RCP, BP); use of 2 composite resin burs reinforced by zirconium glass fibers (F1, F2); and use of an air-polishing system with glycine powder and two power settings (AP1, AP2). The qualitative alterations were recorded by means of a laser profilometer and the mean roughness (Ra ) and mean roughness profile depth (Rz ) were reported. Twenty untreated surfaces were used as controls. RESULTS: The implant collars treated with RCZ (Ra  = 0.33 µm, Rz  = 2.43 µm) or BZ (Ra  = 0.30 µm, Rz  = 3.70 µm) yielded the highest roughness values, followed by the surfaces treated with RCP (Ra  = 0.28 µm, Rz  = 2.02 µm), with BP (Ra  = 0.25 µm, Rz  = 2.16 µm) and by the use of F1 (Ra  = 0.27 µm, Rz  = 2.22 µm) and F2 (Ra  = 0.27 µm, Rz  = 2.04 µm). The lowest roughness values were observed in the AP1 (Ra  = 0.23 µm, Rz  = 1.60 µm) and AP2 (Ra  = 0.16 µm, Rz  = 1.06 µm) group, respectively. Implant collars treated with AP2 yielded statistically significantly lower (P = 0.01) Rz values compared with untreated surfaces. CONCLUSION: All tested procedures did not increase implant surface roughness significantly. Treatment with an air-powder abrasive system at high-pressure setting resulted in a smoothening of the implant collar surface.

Structural and Chemical Analysis of the Zirconia-Veneering Ceramic Interface.

The interfacial interaction of veneering ceramic with zirconia is still not fully understood. This study aimed to characterize morphologically and chemically the zirconia-veneering ceramic interface. Three zirconia-veneering conditions were investigated: 1) zirconia-veneering ceramic fired on sandblasted zirconia, 2) zirconia-veneering ceramic on as-sintered zirconia, and 3) alumina-veneering ceramic (lower coefficient of thermal expansion [CTE]) on as-sintered zirconia. Polished cross-sectioned ceramic-veneered zirconia specimens were examined using field emission gun scanning electron microscopy (Feg-SEM). In addition, argon-ion thinned zirconia-veneering ceramic interface cross sections were examined using scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectrometry (EDS) at high resolution. Finally, the zirconia-veneering ceramic interface was quantitatively analyzed for tetragonal-to-monoclinic phase transformation and residual stress using micro-Raman spectroscopy (µRaman). Feg-SEM revealed tight interfaces for all 3 veneering conditions. High-resolution transmission electron microscopy (HRTEM) disclosed an approximately 1.0-µm transformed zone at sandblasted zirconia, in which distinct zirconia grains were no longer observable. Straight grain boundaries and angular grain corners were detected up to the interface of zirconia- and alumina-veneering ceramic with as-sintered zirconia. EDS mapping disclosed within the zirconia-veneering ceramic a few nanometers thick calcium/aluminum-rich layer, touching the as-sintered zirconia base, with an equally thick silicon-rich/aluminum-poor layer on top. µRaman revealed t-ZrO2-to-m-ZrO2 phase transformation and residual compressive stress at the sandblasted zirconia surface. The difference in CTE between zirconia- and the alumina-veneering ceramic resulted in residual tensile stress within the zirconia immediately adjacent to its interface with the veneering ceramic. The rather minor chemical elemental shifts recorded in the veneering ceramic did not suffice to draw definitive conclusions regarding potential chemical interaction of the veneering ceramic with zirconia. Sandblasting damaged the zirconia surface and induced phase transformation that also resulted in residual compressive stress. Difference in CTE of zirconia versus that of the veneering ceramic resulted in an unfavorable residual tensile stress at the zirconia-veneering ceramic interface.

Color stability and surface roughness of polished anterior restorative materials.

The purpose of this study was to investigate the effects of different finishing-polishing techniques on the color stability and surface roughness of various anterior restorative materials after staining. A composite, a compomer, and a resin-modified glass ionomer were used to prepare 120 specimens. Specimens were divided into subgroups: polishing discs, liquid polishing material, aluminium oxidebonded discs, and control. The specimens were stained in a coffee solution. Color parameters (L*a*b*) and surface roughness before and after staining were measured. The color was affected by the material type (p<0.05) and finishing-polishing systems (p<0.05). The composite showed the highest color stability; however, the color differences of all groups were visible even to the nonskilled operator. The Ra values did not significantly change after staining for any of the restorative groups (p>0.05). The finishing-polishing systems had an effect on color after storing in staining solution.

Influence of surface sealant agents on the surface roughness and color stability of artificial teeth.

STATEMENT OF PROBLEM: Although various surface sealant agents are available and recommended for chairside polishing procedures, their effect on the surface roughness and color stability of denture teeth is not clear. PURPOSE: The purpose of this in vitro study was to evaluate the effect of sealant agents on the surface roughness and color stability of various denture tooth materials. MATERIAL AND METHODS: Eighty disk-shaped specimens were prepared for each type of denture tooth material (SR Vivodent, PMMA; Vitapan, reinforced-PMMA; SR Phonares II, composite resin). The specimens were assigned to 4 groups according to the surface treatment used (n=20): surface sealant agents (Palaseal; Heraeus Kulzer GmbH, Optiglaze; GC Corp Biscover; Bisco Inc) and a conventional laboratory polishing technique (control group). A thermal cycling procedure was applied for half of the specimens (n=10). The surface roughness (Ra) values of thermocycled and nonthermocycled specimens were measured with a profilometer. The CIELab color parameters of both thermocycled and nonthermocycled specimens were measured with a spectrophotometer at baseline and after 7-day storage in a coffee solution. The color differences were calculated from the CIEDE2000 (ΔE00) formula. Data were statistically analyzed with 3-way ANOVA and the Tukey HSD test (α=.05). RESULTS: The type of tooth material, surface treatment technique, and their interactions were significant for Ra values, and each variable and their interactions were also significant for ΔE00 values (P<.05). Thermal cycling had a significant effect only on ΔE00 values (P<.05). CONCLUSIONS: Palaseal and Optiglaze sealant agents provided smoother and more color-stable denture tooth surfaces than the conventional polishing technique. The use of the Biscover agent with SR Vivodent and Phonares II teeth increased the Ra values. The color of conventionally polished SR Vivodent and Phonares II teeth changed more with thermal cycling.

Effect of airborne-particle abrasion of presintered zirconia on surface roughness and bacterial adhesion.

STATEMENT OF PROBLEM: Factors associated with implant periodontal disease of zirconia restorations such as surface roughness remain largely unknown. PURPOSE: The purpose of this study was to investigate how airborne-particle abrasion before sintering affects roughness and bacterial adhesion on the surface of zirconia. MATERIAL AND METHODS: Thirty presintered zirconia specimens were divided into 6 groups of 5 after being polished with silicon carbide paper (1200 grit). A different surface treatment was applied to each group (no treatment [group Ct] and 120-µm alumina abrasion for 5, 8, 10, 12, and 15 seconds [A5s, A8s, A10s, A12s, and A15s]), and the specimens were then densely sintered. The mean centric linear roughness (Ra) was measured, and the 3D measurement of surface roughness (3D roughness) was determined. The number of colony forming units (CFUs) of Streptococcus mutans adhering to the surface was also examined. One-way ANOVA was used for data analysis (α=.05). RESULTS: Airborne-particle abrasion before sintering significantly increased surface roughness. Group A8s, A10s, A12s, and A15s showed statistically significant higher CFU/mL than did group A5s (P<.05). No difference was found in CFU/mL between group Ct and A5s (P=.230). CONCLUSIONS: Airborne-particle abrasion before sintering is a useful method of increasing the surface roughness of zirconia. Ra < 0.58 µm is necessary to inhibit the adherence of S. mutans to zirconia.

Effect of liquid polishing materials on the stainability of bis-acryl interim restorative material in vitro.

STATEMENT OF PROBLEM: The discoloration of interim restorations may negatively affect a patient's perception of treatment. PURPOSE: The purpose of this study was to investigate the effect of liquid polishing materials on the color stability of bis-acryl interim restorative material. MATERIAL AND METHODS: One hundred twenty specimens (10×2 mm) of a bis-acryl interim restorative material were divided into 3 groups. Group CO (control) was not subjected to any liquid polishing material. Groups GC and BC were polished with 2 liquid polishing materials. The specimens were then divided into 4 subgroups (n=10) and stored for 24 hours at 37°C in different staining solutions: coffee, coffee with sugar, cola, and distilled water. The color of the specimens was measured at baseline and after immersion with a spectrophotometer by using the CIE L*a*b* system, and color changes (ΔE) were calculated. The means of color change for each specimen were analyzed by 2-way and 1-way ANOVA tests. Post hoc comparisons were made with the Tukey HSD and Tamhane T2 tests. RESULTS: The application of liquid polishing materials significantly decreased the staining of autopolymerized bis-acryl interim restorative material (P<.01). Coffee with sugar resulted in higher ΔE values than coffee without sugar or cola. CONCLUSIONS: The use of liquid polishing materials significantly decreased staining when compared with bis-acryl specimens without liquid polish. The presence of sugar in coffee increased color change compared with coffee without sugar for all groups evaluated.