Assessment of the color stability of two silicone elastomers for maxillofacial prostheses upon exposure to cold beverages.

PURPOSE: This study investigated the color stability of different commercially available silicone materials for facial prostheses upon exposure to everyday beverages. It was hypothesized that the beverages would not alter the color of the silicone under conditions simulating daily exposure. METHODS: Sixty specimens were fabricated using two materials - VST-50 and Silfy - and exposed to commercially available cold mineral water, tea, or coffee. Specimen color was evaluated on days 1 and 15. The color was measured with a spectrophotometer based on CIELab system and color differences were calculated as ΔE. Statistical analysis was performed using the Kruskal-Wallis test and Mann-Whitney U test. RESULTS: The mean ΔE values after 15 days of exposure to mineral water, cold green tea, and coffee were 1.016, 3.480, and 3.636 for VST-50 and 0.440, 0.798, and 1.425 for Silfy, respectively. Both materials showed significant differences in color, and VST-50 showed a greater color change than Silfy, especially for coffee. CONCLUSION: Pigmented silicone elastomers have low color stability, leading to an overall color change in silicone prostheses when exposed to pigmented beverages. Color changes in such prostheses can be mitigated by selecting materials with better color stability to extend their longevity.

Comparison of digital and visual tooth shade selection.

OBJECTIVE: In dental restorations, color determination is very important for achieving esthetic results. The aim of this study was to compare visual shade selection using digital methods and to assess the repeatability of the utilized intraoral scanners. MATERIALS AND METHODS: In 31 probands, tooth color was determined on teeth 11, 13, and 16. Shade selection was performed visually by a dentist and digitally using Trios 3 and Cerec Omnicam. Three measurements were performed to determine the repeatability of intraoral scanners. Fleiss' κ was used for statistical evaluation of the repeatability and Cohen's κ was used for comparison of methods. RESULTS: The visual method showed only slight agreement with Trios 3 (Cohen's κ: 0.198) and Cerec Omnicam (Cohen's κ: 0.115). Moderate agreement was found between Trios 3 and Cerec Omnicam (Cohen's κ: 0.452). In terms of repeatability, Trios 3 scored higher overall than Cerec Omnicam (Fleiss' κ: 0.612 vs. 0.474). CONCLUSION: Intraoral scanners can facilitate the workflow in clinical practice. They are a good supplement for color determination, but should additionally be confirmed by the visual method. Clinical significance: The use of digital instruments is increasingly being preferred over conventional treatments. Therefore, it is essential to continuously improve the accuracy of intraoral scanners for color selection in order to offer an alternative to visual methods.

The effect of repetitive firings on the color of an alumina ceramic system with varying ceramic shade and thickness.

OBJECTIVE: The color of all-ceramic restorations is one of the main criteria to achieve esthetical success. Many factors such as ceramic thickness, condensation techniques, firing temperature, and numbers can affect the final color of restoration. The purpose of this study was to investigate the color changes in alumina-based ceramic system according to ceramic shade and thickness during the multiple firings. MATERIALS AND METHODS: Sixty disc-shaped specimens with two different veneering porcelain shades (A1 or A3), and with three different ceramic thicknesses (0.5, 1, or 1.5 mm), were fabricated from an alumina-based ceramic system. Multiple firings (3, 5, 7, or 9 firings) were performed, and color changes (ΔE00 ) were determined using a spectrophotometer. Repeated-measures ANOVA were used to analyze the data. The Duncan test was used for multiple comparisons (α = .05). RESULTS: The L*a*b* values of the specimens were affected by the number of firings (3, 5, 7, or 9), veneering ceramic shades (A1 or A3) and veneering ceramic thicknesses (0.5, 1, or 1.5 mm). Significant interactions were present between the number of firings, veneering ceramic shade, and veneering ceramic thickness for L* (p < .001), a* (p < .001), and b* (p < .001) values. CONCLUSIONS: No statistically significant color change was observed between 3rd and 9th firings. CLINICAL SIGNIFICANCE: Veneering ceramic shade, veneering ceramic thickness, and number of firings should be carefully considered to obtain an acceptable color match of the definitive restorations.

Effects of fabrication and shading technique on the color and translucency of new-generation translucent zirconia after coffee thermocycling.

STATEMENT OF PROBLEM: The color stability and translucency of preshaded and externally shaded monolithic and veneered new generation translucent zirconia are not well known. PURPOSE: The purpose of this in vitro study was to investigate the effect of fabrication (veneered or monolithic) and shading (preshaded or externally shaded) techniques on the color and relative translucency of translucent zirconia after coffee thermocycling. MATERIAL AND METHODS: Specimens of different thicknesses (0.5 mm for veneered and 1.5 mm for monolithic) were sectioned from preshaded and externally shaded translucent zirconia. Externally shaded specimens were colored by using the dipping technique. Externally shaded (Ext Mono) and preshaded (Pre Mono) monolithic zirconia specimens were sintered and glazed. Externally shaded (Ext Vene) and preshaded (Pre Vene) 0.5-mm-thick specimens were sintered, veneered with feldspathic porcelain (1 mm), and glazed. The color coordinates of specimens were measured with a spectroradiometer before and after 10 000 thermocycles in coffee solution. Color differences were calculated using CIEDE2000, and relative translucency parameter (RTP) values were calculated using the RTPCIEDE2000 formula. Analysis of variance (ANOVA) was used to analyze the CIEDE2000 color differences and RTP values (α=.05). RESULTS: Shading technique had a significant effect on the color difference values (P=.018). For the translucency data, the 3-way ANOVA revealed a significant interaction between the fabrication technique and shading technique (P=.002). Each pair of material subgroups within each combination of fabrication technique and shading technique was found to have a significantly different RTP, except between Ext Vene and Pre Vene (P=.115). CONCLUSIONS: Externally shaded translucent zirconia had a greater color change in coffee than the preshaded translucent zirconia, either in monolithic or veneered form. Fabrication technique significantly affected the RTP, and the monolithic zirconia was more translucent than the veneered zirconia.

Effect of shading technique and thickness on color stability and translucency of new generation translucent zirconia.

OBJECTIVE: To evaluate the effect of shading technique and thickness on the color stability and translucency of translucent zirconia after coffee thermocycling. METHODS: Specimens in different thicknesses (1; 1.5; 2 mm) (n = 4 for each thickness) were sectioned from translucent preshaded zirconia (Pre) and externally shaded zirconia (Ext). After sintering, specimens were glazed and subjected to 10,000 thermocycling in coffee solution. The color coordinates of specimens were measured with a spectroradiometer before and after coffee thermocyling. Color differences and relative translucency parameter (RTP) values were calculated with CIEDE2000 color difference and TPCIEDE2000 formulas. ANOVA was used to analyze the CIEDE2000 color difference and RTP values (α = 0.05). RESULTS: According to 2-way ANOVA, no significant effect of shading technique and thickness on the color difference values was found (P > .05). According to 3-way ANOVA, a significant interaction between the shading technique and thickness (P < .0001) was found for RTP. The RTP parameter decreased with the increase in the thickness. Ext specimens presented significantly higher RTP than Pre specimens (P < .0001), except for between Ext 1 mm and Pre 1 mm (P = .179). CONCLUSIONS: Neither shading technique nor tested thicknesses affected the color of translucent zirconia. Shading technique and thickness affected the RTP of translucent zirconia. The RTP was inversely affected with the thickness of the material. Externally shaded zirconia presented higher RTP than preshaded zirconia for specimens thicker than 1 mm. CLINICAL SIGNIFICANCE: Discoloration with coffee was insignificant for the tested translucent zirconia in tested thicknesses (1, 1.5, 2 mm). When a translucent restoration is intended, thinner externally shaded translucent zirconia restorations should be preferred instead of preshaded translucent zirconia.

Effect of surface treatments and coffee thermocycling on the color and translucency of CAD-CAM monolithic glass-ceramic.

STATEMENT OF PROBLEM: The effects of surface treatments and coffee thermocycling on the color and relative translucency of a recently introduced computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic glass-ceramic are unknown. PURPOSE: The purpose of this in vitro study was to evaluate the effect of coffee thermocycling on the color and relative translucency parameter (RTP) of CAD-CAM monolithic glass-ceramics after different surface treatments. MATERIAL AND METHODS: Specimens (1.5-mm-thick) were sectioned from zirconia-reinforced lithium silicate glass-ceramic (ZLS) (n=18) and lithium disilicate glass-ceramic (LDS) blocks (n=18). Two different types of surface treatments (glazing or polishing) were applied to the specimens. The specimens were subjected to 5000 thermocycles in a coffee solution. The color coordinates of specimens were measured before and after coffee thermocycling by using a spectroradiometer, and color differences and relative translucency values were calculated by using CIEDE2000 color difference and RTP formulas. ANOVA was used to analyze the color difference and relative translucency values by using maximum likelihood estimation and the Satterthwaite degrees of freedom methods. Any significant interaction between surface subgroups was further analyzed by using the Tukey-Kramer adjustment (α=.05). RESULTS: Material type had a significant effect on color difference (P=.018). All color difference values of all materials were smaller than the clinical acceptability threshold (<1.8 units). For relative translucency, material (P<.001) and coffee thermocycling had a significant effect (P=.014), and an interaction was found between the surface treatments and materials (P<.001). The Tukey-Kramer test revealed significant differences between glazed and polished subgroups of LDS material, except for ZLS-glazed and ZLS-polished subgroups. CONCLUSIONS: Different surface treatments of CAD-CAM monolithic zirconia-reinforced lithium silicate and lithium disilicate glass-ceramics resulted in clinically acceptable color changes after coffee thermocycling. The color changes in all groups, except for LDS-polished, were not perceivable. Lithium disilicate was more translucent than zirconia-reinforced lithium silicate before and after coffee thermocycling. Coffee thermocycling decreased the translucency of both of the materials. Different surface treatments affected the translucency of only lithium disilicate for tested thickness.

Effect of thickness on optical properties of monolithic CAD-CAM ceramics.

OBJECTIVE: To compare the effect of material and thickness on the color stability and relative translucency parameters (RTP) for monolithic ceramics subjected to coffee thermocycling. METHODS: Four specimens each at thicknesses of 0.5, 0,7 and 1 mm were sectioned from monolithic ceramics [preshaded monolithic zirconia (MonZr), lithium disilicate (LDS) and zirconia reinforced lithium silicate (ZLS)]. The specimens were glazed and subjected to 5000 coffee thermocycling. The color coordinates of specimens were determined with a spectroradiometer and color differences and RTP values were calculated with CIEDE2000 color difference and TPCIEDE2000 formulas. ANOVA was used to analyze CIEDE2000 color difference and RTP values (α = .05). RESULTS: For the color difference data, the 2-way ANOVA revealed a significant interaction between material and different thickness (P = .002). Except for 0.5 mm thick ZLS material, all materials in all thicknesses studied presented color changes within the clinically acceptable limits after coffee thermocycling. For the RTP data, the 3-way ANOVA revealed a highly significant interaction between material and different thicknesses (P < .001). CONCLUSIONS: Material type and thickness can be expected to affect color change and relative translucency of the restorations made with preshaded MonZr, LDS and ZLS materials. Except for 0.5 mm thick ZLS material, color changes of all studied materials were within the clinically acceptable limits. Except ZLS material, color changes of other materials were not significantly affected by thickness. Staining in coffee was not found to affect translucency, and the materials' translucency parameters were ranked from high to low as LDS, ZLS and MonZr at each thickness studied.

Functionalized pink Al2O3:Mn pigments applied in prosthetic dentistry.

STATEMENT OF PROBLEM: The color of dental poly(methyl methacrylate) (PMMA) is conventionally rendered by organic and inorganic pigments, which are usually not bonded to the polymer network. Functionalized ceramic pigments can be used to color PMMA, allowing improved chemical interaction with the resin matrix. PURPOSE: The purpose of this in vitro study was to synthesize, functionalize, and characterize pink manganese-doped alumina ceramic pigments. The hypothesis tested was that functionalized ceramic pigments would render pink coloration to a translucent PMMA without jeopardizing its mechanical properties. MATERIAL AND METHODS: Pink alumina powders doped with 1 or 2 mol% of manganese (Al2O3:Mn) were prepared by means of a polymeric precursor method. Pigment (Pig.) particles were functionalized with a silica coating method followed by silanation before preparation of PMMA-based composite resins (5 wt% pigment). The color of composite resins (Pig.1% and Pig.2%) and PMMA controls (Pink and translucent [Trans]) was evaluated (CIELab color coordinates), and their mechanical properties were tested (3-point bending). RESULTS: The microstructure of the pigment particles showed approximately 55-nm nanocrystals of manganese-doped α-alumina clustered into irregular porous particles up to 60 µm. The composite resins and pink PMMA showed similar color parameters (CIE a* pink=20.1, Pig.1%=14.6, Pig.2%=16.0, Trans=0.19, P<.001; CIE b* Pink=17.0, Pig.1%=18.6, Pig.2%=19.0, Trans=2.52, P<.001). No statistical differences were observed in mechanical properties among groups (σf pink=98.4, Pig.1%=98.1, Pig.2%=98.8, trans=89.1, P=.136). CONCLUSIONS: The addition of the functionalized pink ceramic pigments to a translucent PMMA yielded similar coloration to that of the regular pink PMMA used in dentistry and did not jeopardize its mechanical properties.

Comparison of conventional and plant-extract disinfectant solutions on the hardness and color stability of a maxillofacial elastomer after artificial aging.

STATEMENT OF PROBLEM: Silicone elastomers undergo physical and chemical degradation with disinfecting solutions. Phytotherapy may be a suitable solution for disinfection. However, its effect on the properties of the silicone material is unknown. PURPOSE: The purpose of this in vitro study was to evaluate the effect of disinfection with conventional and plant-extract solutions and of artificial aging on the hardness and color stability of a facial silicone associated with pigments and an opacifier. MATERIAL AND METHODS: Four hundred specimens of silicone (MDX4-4210) were fabricated (5×6 mm). Two pigment shades and 1 dry opacifier were combined in the tested material, and 4 groups (n=10) were obtained: colorless (GI), colorless with opacifier (GII), medium pigment with opacifier (GIII), and black pigment with opacifier (GIV). Specimens were subjected to disinfection (30 days) using saline solution, water, and neutral soap (digital friction, 30 seconds), chlorhexidine 4%, Hydrastis canadensis, and Cymbopogon nardus extracts (immersion, 10 minutes). Shore A hardness (ASTM D2240) and color analyses were performed before and after disinfection. Specimens were then exposed to 1008 hours of artificial aging (ASTM 53) and subjected to final hardness and color readings. The results were analyzed with ANOVA and the Tukey significant difference test (α=.05). RESULTS: The opacifier increased the hardness (GII). For GII, the H. canadensis solution and the friction with water and soap promoted significantly reduced hardness; the friction also promoted a reduction in this property for GIV. The GIII was not affected after disinfection. A significant difference was found between the ΔE values of the specimens disinfected with H. canadensis, C. nardus, and chlorhexidine, and specimens subjected to saline solution and neutral soap. CONCLUSION: The hardness of MDX4-4210 after the experimental procedure was considered clinically acceptable for facial prostheses. All groups showed clinically unacceptable color alterations regardless of the disinfecting solution.

Colour stability of maxillofacial silicone elastomers: a review of the literature.

Colour degradation is a serious limitation of maxillofacial silicone elastomers and most silicone facial prostheses have to be remade within 1 year due to colour deterioration. A comprehensive review of the literature was completed using MEDLINE and PubMed Library databases. This was supplemented with a manual search of selected journals and textbooks. English language articles published in peer-reviewed journals from 1966 to January 2012 in which colour stability of silicone elastomers was evaluated using standard research protocols were included. In all, 127 articles were identified and 23 met the inclusion criteria. Current literature reveals that average colour stability of maxillofacial silicone prostheses is 6-12 months, and inherent unstable nature of silicones is responsible for the color degradation. Opacifiers, oil pigments and inorganic colourants may have a protective effect on colour stability of prostheses. Organic colourants, ultraviolet (UV) light, cleansing solutions, dust and aging can adversely affect colour stability of silicone prostheses. A direct comparison between studies has not been possible, because of the differences in experimental set-up such as materials tested, colourants used, or method of aging. There appears to be a need for a standardised test protocol for colour stability of maxillofacial materials. Colour degradation limits the useful lifespan of maxillofacial silicones. Improvements in colour stability is possible with the use of certain nano opacifiers, UV absorbers, photoprotective agents, and use of inorganic pigments and metal oxides.

Color stability of different composite resin materials.

STATEMENT OF PROBLEM: Data are needed to better predict the color stability of current composite resin materials. PURPOSE: The purpose of this study was to evaluate the impact of different storage solutions on the color stability of different composite resin materials. MATERIAL AND METHODS: Different restorative and adhesive composite resin specimens (dual-polymerizing self-adhesive resin cement, autopolymerizing resin-based composite resin, dual-polymerizing resin-based composite resin, nanohybrid composite resin, and microhybrid composite resin) were fabricated and stored in red wine, black tea, chlorhexidine, sodium fluoride, tea tree oil, or distilled water for 4 weeks at 37°C. Color parameters were measured with a colorimeter before and after storage. Total color differences and specific coordinate differences were expressed as ΔE, ΔL, Δa, and Δb. A 2-way and 1-way analysis of variance (ANOVA) with Bonferroni adjustment for multiple comparisons were applied for statistical calculations (α=.05). RESULTS: Red wine caused the most severe discoloration (ΔE >10), followed by black tea with perceptible (ΔE >2.6) to clinically unacceptable discoloration (ΔE >5.5). Colored mouth rinses discolored the materials to a lesser extent with clinically acceptable values. Dual-polymerizing resin adhesives showed a higher amount of discoloration. CONCLUSIONS: Current restorative and adhesive composite resin materials discolor over time under the influence of different storage solutions. The composition related to the polymerizing mode seemed to be a causative factor.

Color variation between matched and fabricated shades of different ceramics.

PURPOSE: The aim of this study was to evaluate and compare the total color difference (ΔE) between natural teeth and fabricated crowns from three ceramic systems with different thicknesses. MATERIALS AND METHODS: The color of ninety maxillary central incisors was measured from the middle third of the labial surface with a Vita Easyshade spectrophotometer. All-ceramic crown preparations with different thicknesses (0.8, 1.2, 1.5 mm) were done on selected teeth (n = 30). Prepared teeth were randomly divided into three equal groups to fabricate ceramic crowns from three ceramic systems, Duceram LFC (DLFC), In-Ceram SPINELL (ICS), and IPS Empress (IPSE). Colors of cemented crowns were measured and compared with their corresponding measurements before preparations. Data were statistically analyzed using two-way ANOVA at 5% significance level. RESULTS: A significant difference of ΔE was detected between natural teeth and different thicknesses of crowns constructed from the all-ceramic materials investigated. Comparing the three materials at 0.8 mm thickness revealed that the lowest ΔE was recorded for DLFC, which was significantly different from the other ceramic systems while IPSE showed the highest ΔE. At higher thicknesses there was no difference between natural tooth shade and crowns constructed from different ceramic materials. CONCLUSIONS: Reinforcement of ceramics by alumina for In-Ceram and leucite for Empress decreases color production. Level of acceptance between the different ceramic materials and thicknesses varied. DLFC showed the highest color matching at all thicknesses followed by ICS and IPSE in descending order. In general, increasing the thickness of fabricated crowns enhances color match.

Effect of alloy recasting on the color of opaque porcelain applied on different dental alloy systems.

STATEMENT OF PROBLEM: The effect of different proportions of recast dental alloys on the color of overlying opaque porcelain (OP) is unknown. PURPOSE: The purpose of this study was to compare the color of OP applied on 2 different proportions (50% and 100%) of recast alloys with the color of commercially available shade tabs of OP. MATERIAL AND METHODS: Six different metal alloy systems (2 base: Metalloy CC, Cr-Co [B-MCC]; Heraenium NA, Ni-Cr [B-HNA]; 3 noble: Cerapall 2, Pd-Au [N-CP2]; Triumph, Pd-Ag [N-T]; V-Deltaloy, Au-Pd [N-VD]; and 1 high-noble: V-Gnathos Plus, Au-Pt [HN-GP]) were selected for the fabrication of disk-shaped specimens (10 mm in diameter, 1 mm in thickness). Each alloy was divided into 2 subgroups: 50% new alloy with 50% recast alloy (n=3) and 100% recast alloy (n=3). OP (B1) was applied (0.1 mm) to all specimens. The color coordinates (L*, a*, b*) of each specimen and the corresponding commercially available OP shade tab (control) were measured with a spectroradiometer, and color differences between specimens and control group were calculated. Data were statistically analyzed (2-way ANOVA, Ryan-Einot-Gabriel-Welsch multiple range test, α=.05). RESULTS: For each alloy, ΔL*(L(control)(-)L(recastalloy)) values for the 2 subgroups were not statistically different from each other. The Δa* and Δb* of different proportions of N-CP2, B-HNA, N-VD, and HN-GP were not statistically different within the alloys. However, the a* values of 100% recast N-T and B-MCC were significantly closer to the a* values of the control group, and the b* values of 50% recast B-MCC were significantly closer to the b* values of the control group (P<.05). Delta E(control-recast) alloy values for different proportions of alloys were not statistically different. However, color differences did not meet the criterion of clinical acceptability (ΔE=3.46). CONCLUSIONS: According to the results of this study, the different proportions (50% and 100%) of recast alloys used have similar effects on the color of OP. Differences between the final color of OP on the recast alloys used and the color of OP shade guide tabs did not meet the criterion of clinical acceptability considered in this study.

Changes in chroma of two indirect composite materials polymerized with different polymerization systems.

This study evaluated chroma change in two composite materials (Sinfony and Pearleste) polymerized with two different systems. Disk specimens were prepared using a metal halide unit (Hyper LII) and an exposure time of 60 to 180 s. The proprietary polymerization systems (Visio and Pearlcure systems) were used as the reference polymerization modes. After storage at 37°C for 24 h, CIE 1976 L*a*b* values were measured by using a dental chroma meter (ShadeEye NCC) with a gray background. The specimens were then immersed in water or tea. Color change from baseline to 4 weeks was evaluated by measuring ΔL*, Δa*, and Δb*, after which ΔE*(ab) values were calculated. The brightness of Sinfony specimens was reduced by tea immersion. The color of both materials shifted to yellow after tea immersion, although color change in Sinfony specimens was greater than that in Pearleste specimens. For both materials, color change was less after polymerization with the metal halide unit. In conclusion, Sinfony polymerized with the Hyper LII unit, and Pearleste polymerized with either system, were stable against discoloration due to tea immersion.

Retrievable metal ceramic implant-supported fixed prostheses with milled titanium frameworks and all-ceramic crowns: retrospective clinical study with up to 10 years of follow-up.

PURPOSE: The purpose of this study was to report on the outcome of metal ceramic implant-supported fixed prostheses with milled titanium frameworks and all-ceramic crowns. MATERIALS AND METHODS: The clinical study included 108 patients (67 women, 41 men), mean age of 58.6 years (range: 34-82), followed between 9 months and 10 years (post occlusal loading). The mean follow-up time for all patients in the study was 5 years. A total of 125 prostheses were fabricated. The data were divided into 2 groups. Development group (DG): 52 patients with 66 prostheses (28 maxillary, 38 mandibular) fabricated with individual Procera crowns (Alumina copings, Nobel Biocare AB) and Allceram ceramics (Ducera Dental GmbH) cemented onto a CAD/CAM fabricated Ti framework (Nobel Biocare AB) with pink ceramic (Duceram, Ducera Dental GmbH) that replicated the missing gingival tissues. Routine group (RG): 56 patients with 59 prostheses (49 maxillary, 10 mandibular) fabricated with individual Procera crowns (Zirconia copings and Nobel Rondo Zirconia Ceramic; Nobel Biocare AB) cemented onto a CAD/CAM fabricated Ti framework (Nobel Biocare AB) with pink acrylic resin (PallaXpress Ultra, Heraeus Kulzer GmbH) that replicated the missing gingival tissues. Primary outcome measures were prosthetic survival and mechanical complications. Secondary outcome measures were biological complications testing the retrievability characteristic of the prosthesis. Survival estimates were calculated on the patient level with the Kaplan-Meier product limit estimator (95% confidence intervals [CI]). Data were analyzed with descriptive and inferential analyses. RESULTS: The cumulative survival rates for the implant-supported fixed prostheses were 92.4% for the DG at 10 years and 100% for the RG at 5 years (overall 96%) (Kaplan-Meier). Mechanical complications occurred in 44 patients (DG: 29 patients, 36 prostheses; RG: 15 patients, 16 prostheses); the large majority were crown fractures, occurring in 48 patients (DG: 33 patients, 36 prostheses; RG: 15 patients, 16 prostheses). In the DG, univariate analysis of logistic regression disclosed the presence of a metal ceramic implant-supported fixed prosthesis opposing dentition as a risk factor for crown fracture (OR = 1.97). Biological complications occurred in 33 patients (DG: 18 patients; RG: 15 patients), the majority being peri-implant pathologies in 19 patients (DG: 9 patients, RG: 10 patients). All situations were resolved except one in the DG that led to fixture and prosthesis loss. CONCLUSIONS: The results of this study indicated that, within the limitations of this study, the CAD/CAM protocol is acceptable for definitive prosthetic rehabilitation. This protocol provided these patients with a good prognosis on a middle- to long-term basis (5 years).

The influence of metal substrates and porcelains on the shade of metal-ceramic complex: a spectrophotometric study.

BACKGROUND: The final esthetic outcome of a metal-ceramic restoration is influenced by several factors including the type of the underlying metal as well as the brand of the ceramic. SETTINGS AND DESIGN: An in vitro study. AIMS: The purpose of the in vitro study was to investigate the influence of four types of metal-ceramic alloys and two porcelain systems on the color co-ordinates of the metal-ceramic complex. It also aimed at establishing a color index which correlated the color of the metal-ceramic combination to the yellow-blue axis. MATERIALS AND METHODS: Twenty-four disc-shaped metal specimens of 12 mm × 1 mm were cast from base metal alloys, nickel-chromium (Ni-Cr) (Wiron 99), cobalt-chromium (Co-Cr) (Wirobond C), a palladium (Pd)-rich noble metal alloy (Spartan Plus), and a high noble gold (Au) alloy (Pontostar). These discs were covered with two commercially available feldspathic porcelains (Vita Omega and Shofu Vintage) of A3 shade to a total thickness of 1.2 mm. Each group had six specimens, of which three were coated with Vita Omega and the remaining with Shofu Vintage. Opaque and dentin layers were applied to a standardized thickness of 0.2 mm ± 0.05 mm and 1 mm ± 0.05 mm, respectively onto the metal surface after air abrasion with 50 µm alumina particles. The reflectance spectra were measured with a spectrophotometer and data were recorded in L*, a* and b* coordinates in the CIE Lab Color Order System. STATISTICAL ANALYSIS: Analysis of variance (ANOVA) and path analysis were the statistical tools employed to analyze the data. A critical difference (CD) value was calculated for each color co-ordinate to make comparisons between each metal-ceramic combination. A color index for each metal-ceramic complex was also calculated from the color co-ordinates obtained. RESULTS: ANOVA revealed that significant differences existed between the metal-porcelain combination at 0.01 ( P < 0.01) level. The L* value was significantly higher for Au and Co-Cr alloys with Vita Omega porcelain. The a* value was highest for Ni-Cr alloy when combined with Shofu Vintage ceramic. The b* value of Au alloy with Vita Omega porcelain was significantly higher than any other metal-ceramic combination. The color co-ordinates of Pd alloy with both porcelain systems did not show any significant differences. Gold alloy with Vita Omega showed the highest color index value. CONCLUSION: The variations in metal-ceramic alloy and porcelain can influence the shade of a metal-ceramic restoration. Color index value was the highest for gold alloy.

Effects of air-polishing powders on color stability of composite resins

OBJECTIVES: The purpose of this study was to investigate the effect of different air-polishing powders on the color stability of different types of composite resin restorative materials. MATERIAL AND METHODS: Thirty cylindrical specimens (15×2 mm) were prepared for each of 7 composite resin restorative materials. All specimens were polished with a series of aluminum oxide polishing discs (Sof-Lex). The prepared specimens of each composite resin were randomly divided into 3 groups of 10 specimens each, for control (Group-C) and two air-powder applications (Group-CP: Cavitron Prophy-Jet; Group-PS: Sirona ProSmile prophylaxis powder). A standard air-polishing unit (ProSmile Handly) was used. All specimens were air-powdered for 10 s at 4-bar pressure. The distance of the spray nosel from the specimens was approximately 10 mm and angulation of the nosel was 90°. Specimens were stored in 100 mL of coffee (Nescafe Classic) for 24 h at 37°C. Color measurement of all specimens was recorded before and after exposure to staining agent with a colorimeter (Minolta CR-300). Color differences (∆E*) between the 2 color measurements (baseline and after 24 h storage) were calculated. The data were analyzed with a 2-way ANOVA test, and mean values were compared by the Tukey HSD test (p<0.05). RESULTS: According to the 2-way ANOVA results, composite resin restorative materials, air-polishing powders, and their interaction were statistically significant (p<0.05) For Aelite Aesthetic Enemal, Filtek Z250, Grandio, CeramX Mono, and Quixfil composite resin restorative materials, no significant difference was observed between Group-PS and Group-CP (p>.05) and these groups demonstrated the highest ∆E* values. For Filtek Silorane and IntenS, the highest ∆E* values were observed in Group-PS. The lowest ∆E* values for all composite resin groups were observed in Group-C. When comparing the 7 composite resin restorative materials, Aelite Aesthetic Enemal demonstrated significantly less ∆E* values than the other composite resins tested. The highest ∆E* values were observed in Quixfil. CONCLUSION: Except for Quixfil, all control groups of composite resins that were polished Sof-Lex exhibited clinically acceptable ∆E values (<3.7). Air-polishing applications increased the color change for all composite resin restorative materials tested. Composite restorations may require re-polishing after air-polishing.

The effect of repeated firings on the color of feldspathic ceramics.

The aim of this study was to determine the extent to which repeated firings would change the color of feldspathic ceramics. Specimens were fabricated from five commercially available feldspathic ceramics using a circular stainless steel matrix 11 mm in diameter and 1.0 mm thick (n = 10, shade = A3). Repeated firings were performed and color analysis was completed with a colorimeter using the CIELA B color coordinates. Two-way ANOVA was used to analyze the data, followed by Tukey's post-hoc test (a = 0.05). Three factors were used as determinants: a, a measure of the chroma along the red-green axis; b, a measure of the chroma along the yellow-blue axis; and L, a measure of the lightness-darkness of the specimen on a scale from 0 (black) to 100 (white). The results indicated that a and b values increased and L values decreased after repeated firings, resulting in reddish, yellowish, and darker specimens, respectively (P = 0.001). As the number of firings increased, significant color alterations occurred in the color parameters of the specimens. These alterations resulted in color changes (delta E) that could be considered unacceptable in clinical practice.

Effects of air-polishing powders on color stability of composite resins.

OBJECTIVES: The purpose of this study was to investigate the effect of different air-polishing powders on the color stability of different types of composite resin restorative materials. MATERIAL AND METHODS: Thirty cylindrical specimens (15×2 mm) were prepared for each of 7 composite resin restorative materials. All specimens were polished with a series of aluminum oxide polishing discs (Sof-Lex). The prepared specimens of each composite resin were randomly divided into 3 groups of 10 specimens each, for control (Group-C) and two air-powder applications (Group-CP: Cavitron Prophy-Jet; Group-PS: Sirona ProSmile prophylaxis powder). A standard air-polishing unit (ProSmile Handly) was used. All specimens were air-powdered for 10 s at 4-bar pressure. The distance of the spray nosel from the specimens was approximately 10 mm and angulation of the nosel was 90°. Specimens were stored in 100 mL of coffee (Nescafe Classic) for 24 h at 37°C. Color measurement of all specimens was recorded before and after exposure to staining agent with a colorimeter (Minolta CR-300). Color differences (∆E*) between the 2 color measurements (baseline and after 24 h storage) were calculated. The data were analyzed with a 2-way ANOVA test, and mean values were compared by the Tukey HSD test (p<0.05). RESULTS: According to the 2-way ANOVA results, composite resin restorative materials, air-polishing powders, and their interaction were statistically significant (p<0.05) For Aelite Aesthetic Enemal, Filtek Z250, Grandio, CeramX Mono, and Quixfil composite resin restorative materials, no significant difference was observed between Group-PS and Group-CP (p>.05) and these groups demonstrated the highest ∆E* values. For Filtek Silorane and IntenS, the highest ∆E* values were observed in Group-PS. The lowest ∆E* values for all composite resin groups were observed in Group-C. When comparing the 7 composite resin restorative materials, Aelite Aesthetic Enemal demonstrated significantly less ∆E* values than the other composite resins tested. The highest ∆E* values were observed in Quixfil. CONCLUSION: Except for Quixfil, all control groups of composite resins that were polished Sof-Lex exhibited clinically acceptable ∆E values (<3.7). Air-polishing applications increased the color change for all composite resin restorative materials tested. Composite restorations may require re-polishing after air-polishing.

[Clinical assessment of acceptability of shade mismatch of infiltrated alumina ceramic crowns].

PURPOSE: To measure and evaluate the acceptability of shade mismatch of infiltrated alumina ceramic crowns directly in clinic. METHODS: Ten cases with restoration of hot casting alumina ceramic crown were collected in clinic. L*, a*, b*, C, H, ΔE values of hot casting alumina ceramic crowns and corresponding natural teeth in natural light were surveyed and calculated, then analyzed with CIE1976L*a*b* color system, digital photography and Photoshop CS2. All statistical analyses and calculations were completed in paired t test with SAS6.12 software package. RESULTS: In cervical 1/3 region, significant statistical difference in lightness, a*, hue angle parameter value between alumina all-ceramic crown and natural tooth (P<0.01) was found; in middle 1/3 region, significant difference in a*, b*, saturation parameter value (P<0.01) existed; in incisory 1/3 region, the parameters had no significant difference (P>0.05). To parameter ΔE, there was significant difference in every region, but it was in the acceptable range. CONCLUSIONS: The acceptability of shade mismatch is about 6 ΔE units, we can analyse the color difference between the restoration and natural teeth directly in clinic through symmetry of central incisor.