Influence of implant abutment material on the color of different ceramic crown systems

In Vitro Effect of Anodization of Titanium Abutments on Color Parameters and Color Difference of Lithium Disilicate All-Ceramic Crowns

OBJECTIVE

This study assessed the effect of the anodization of titanium abutments on the color parameters and color difference of lithium disilicate (LDS) all-ceramic crowns.

MATERIALS AND METHODS

In this study, 19 straight abutments were divided into two groups: anodized (n = 9) and non-anodized control (n = 9), with one hybrid zirconia abutment as a reference. Anodization was achieved by applying 63 V energy using seven 9 V flat batteries in series, with an electrolyte solution comprising 1 g trisodium phosphate in 250 mL distilled water for 5 s, resulting in a gold-yellow color. Abutments were then scanned, and full-contour monolithic IPS e.max maxillary central incisor crowns were fabricated with 2 mm thickness and glazed. Reflectance was measured using a spectroradiometer, and color coordinates (L*, a*, b*, h*, and C*) were calculated using CS-10W software. Color differences of the crowns in both groups were quantified using the CIEDE2000 (ΔE00) color difference formula and analyzed by t-test (α = 0.05) compared to the standard sample.

RESULTS

The L*, a*, b*, and c* parameters in anodized abutments were significantly higher than those in non-anodized abutments, while the h* parameter in anodized abutments was significantly lower than that in non-anodized abutments (p < 0.001 for all). There was a significant difference in ΔE00 of the two groups (p = 0.043).

CONCLUSION

Anodization of titanium abutments improved the color parameters of LDS all-ceramic crowns and significantly decreased their ΔE compared with non-anodized abutments.

The impact of various substrates, ceramic shades, and brands on the ultimate color and masking capacity of highly translucent monolithic zirconia: an in vitro study

This study aimed to examine the impact of substrates, ceramic shades, and brands on the color and masking ability of highly translucent monolithic zirconia (HTMZ) using CIELab and CIEΔE2000 metrics. A total of 156 1-mm thick HTMZ disks in shades A1, A2, and A3 were produced using Dental Direkt and Kerox zirconia brands. Four 3-mm thick substrates (nickel-chromium alloy, non-precious gold alloy (NPG), zirconia shade A2, and resin composite shade A2) were prepared. HTMZ disks were overlaid on these substrates, and color measurements were taken with a spectrophotometer. Color differences (ΔE) were analyzed using CIELab and CIEΔE2000 formulas. The influence of brand, shade, substrate, and their interactions on ΔE values was assessed with a General Linear Model (GLM) and LSD pairwise comparison test. Spearman's correlation test examined the relationship between CIELab and CIEΔE2000 values. Results indicated that ΔEab was significantly influenced by substrate type and shade, while ΔE2000 was also affected by the ceramic brand. Mean color differences across ceramic-substrate groups were within clinically acceptable and perceptible ranges (clinically perceptible: ∆Eab ≥ 1.3 and ∆E2000 ≥ 0.8; clinically acceptable: 0.8 < ∆E2000 ≤ 1.8 and 1.3 < ∆Eab ≤ 2.7), except for NPG, which had ΔE values exceeding the perceptible range (ΔE2000: 1.1 ± 0.11 to 1.8 ± 0.31; ΔEab: 1.61 ± 0.15 to 2.16 ± 0.36). A significant correlation (r = 0.974, P < 0.001) was found between ΔEab and ΔE2000. Various ceramic brands and shades led to notable ΔE variations, yet average color differences within all ceramic-substrate groups remained clinically acceptable. Both ΔEab and ΔE2000 were reliable methods with a strong correlation for measuring color differences.

Effect of cement type, luting protocol, and ceramic abutment material on the shade of cemented titanium-based lithium disilicate crowns and surrounding peri-implant soft tissue: a spectrophotometric analysis

PURPOSE

The objective of the study was to analyze the impact of cement, bonding pretreatment, and ceramic abutment material on the overall color results of CAD-CAM ceramic crowns bonded to titanium-based hybrid abutments.

MATERIALS AND METHODS

For single implant restoration of a maxillary lateral incisor a total of 51 CAD-CAM-fabricated monolithic lithium disilicate crowns were fabricated and subsequently bonded onto 24 lithium disilicate Ti-base abutments, 24 zirconia Ti-base abutments and 3 resin abutment replicas as a control group. The 48 copings were cemented with three definitive and one provisional cement on both grit-blasted and non-blasted Ti-bases. The color of each restoration and surrounding artificial gingiva was measured spectrophotometrically at predefined measuring points and the CIELAB (ΔEab) color scale values were recorded.

RESULTS

The color outcome of ceramic crowns bonded to hybrid abutments and soft tissues was affected differently by cements of different brands. Grit-blasting of Ti-bases prior to cementing CAD-CAM copings affected the color results of all-ceramic crowns. There was a significant difference (P = .038) for the median ΔE value between blasted and non-blasted reconstructions at the cervical aspect of the crown. Full-ceramic crowns on zirconia Ti-base abutments exhibited significantly lower ΔE values below the threshold of visibility (ΔE 1.8). In all subcategories tested, the use of a highly opaque temporary cement demonstrated the lowest median ΔE for both the crown and the artificial gingiva.

CONCLUSION

Various cements, core ceramic materials and airborne particle abrasion prior to bonding can adversely affect the color of Ti-base supported ceramic crowns and peri-implant soft tissue. However, zirconia CAD-CAM copings and an opaque cement can effectively mask this darkening.

Development of patient-specific finite element model for study of composite dental implants

Traumatic dental injuries can occur due to various reasons such as accidents, sports injuries, fights, falls, and others. These injuries can affect the teeth, gums, and surrounding tissues, and can range from minor chips and cracks to severe fractures, dislocations, and avulsions (when the tooth is completely knocked out of the socket). The most common way to address this is by replacing affected teeth with dental implants. The purpose of this research is to evaluate the use of composite materials in dental implants and compare them with the traditionally used materials using a patient specific cone beam computed tomography (CBCT) based finite element model (FEM). To conduct this research, two different implant groups i.e., traditional implant and composite implant were designed using Titanium grade 4, zirconium oxide-reinforced lithium silicate (ZLS), and Zirconia (ZrO2). Six dental implants were designed namely Ti implant, ZLS implant, ZrO2implant, Ti-ZrO2composite, Ti-ZLS composite, and ZLS-ZrO2composite using 3D modelling software. Detailed full-scale 3D models of patient specific dental implant were developed and traumatic loading conditions were applied to the enamel of central incisor teeth or crown of dental implant, and maxilla was constrained in all directions. It was found that the use of composite materials for dental implants can reduce the stresses over the surface of abutment and implant as compared to traditional implants. The detailed models developed as a part of this study can advance the research on dental implants, and with further experimental validation allow the use of composite materials for fabrication of more stable dental implants.

Color and translucency of milled polymethyl methacrylate crowns on non-tooth-colored interim abutments with different surface treatments

STATEMENT OF PROBLEM

The interim rehabilitation of implants has become a necessity, particularly for those placed in the esthetic regions. However, the optical properties of computer-aided design and computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA) crowns on interim abutments with different surface treatments are unclear.

PURPOSE

The purpose of this in vitro study was to investigate the color and translucency of CAD-CAM PMMA crowns when different surface treatments were used on titanium interim abutments.

MATERIAL AND METHODS

A maxillary dentate stone cast with a narrow-diameter implant analog at the left lateral incisor site was used. Three titanium interim abutments (blue) were divided into 3 groups according to the surface treatment they received: control (steam cleaning), opaqued (120-μm Al2O3 airborne-particle abrasion and opaque application), and airborne-particle abraded (120-μm Al2O3). Thirty PMMA crowns (A2 shade) were milled (n=10). The color coordinates of the crown-interim abutment pairs and a shade tab (A2) were measured by using a colorimeter. The color differences (ΔE00) between the crowns and the shade tab and the relative translucency parameter (RTP) values of the crowns were calculated by using the CIEDE2000 formula. One-way ANOVA was used to analyze the ΔE00 and RTP values with subsequent Tukey honestly significant difference tests (α=.05).

RESULTS

The abutment surface treatment significantly affected the ΔE00 of interim crowns from the shade tab (P<.001), but no significant effect was found on RTP (P=.26). The control group had the highest ΔE00 from the shade tab (P≤.011). No significant difference (P=.14) was found between the opaqued and the ΔE00 of the airborne-particle abraded groups from the shade tab.

CONCLUSIONS

The surface treatments of interim abutments affected the color of CAD-CAM PMMA crowns, which differed from that of the shade tab. The color of crowns on opaqued or airborne-particle abraded interim abutments was closer to the color of the shade tab. Abutment surface treatments did not affect the translucency of crown-interim abutment pairs.

Effect of cross-polarization filters on the trueness of colors obtained with a single-lens reflex camera, macro lens, and a ring flash

OBJECTIVE

To investigate the effect of cross-polarization filters on the colors of shade tabs obtained with a digital single-lens reflex (DSLR) camera, macrolens, and a ring flash.

MATERIALS AND METHODS

Digital images of four shade tables (1M1, 3L2.5, 3R2.5, and 5M3) from the VITA Toothguide 3D-Master shade guide were taken using a DSLR camera, 100 mm macrolens, and ring flash with two different cross-polarizing filters (Polar_eyes and Filtropolar), and without (Nonpolarizer; n = 7). The CIE L*a*b* color coordinates of digital images were calculated and remeasured with a spectroradiometer (SR). The color differences (ΔE00 ) between the SR and digital images were calculated and analyzed with the two-way analysis of variance (ANOVA) and Tukey HSD test (α = 0.05).

RESULTS

ΔE00 values of all test groups were higher than the clinically acceptable threshold (∆E00  > 1.80). While the ∆E00 values of Filtropolar (6.19 ± 0.44) and Polar_eyes (7.82 ± 0.23) groups were significantly higher than the Nonpolarizer (4.69 ± 0.32) for the 1M1 shade tab, ∆E00 value of Polar_eyes (6.23 ± 0.34) was significantly lower than Nonpolarizer (10.71 ± 0.48) group for 5M3 shade tab (p < 0.05).

CONCLUSION

The color-matching results of tested digital photography techniques with and without cross-polarization were unacceptable, compared to a spectroradiometer. While digital photography with Polar_eyes cross-polarizing filter has closer results to the reference device for the low-in-value shade table (5M3), for the high-in-value shade table (1M1), improved results were obtained without a cross-polarizing filter.

CLINICAL SIGNIFICANCE

The cross-polarization filters are increasingly used in dentistry for tooth color communication with digital photography techniques. However, the digital photography techniques with-without cross-polarization filterers should be improved to obtain clinically acceptable color-matching results.

Effect of abutment types and resin cements on the esthetics of implant-supported restorations

PURPOSE

The aim of the study was to evaluate the optical properties of new generation (3Y-TZP) monolithic zirconia (MZ) with different abutment types and resin cement shades.

MATERIALS AND METHODS

A1/LT MZ specimens were prepared (10 × 12 × 1 mm, N = 30) and divided into 3 groups according to cement shades as transparent (Tr), yellow (Y) and opaque (O). Abutment specimens were obtained from 4 different materials including zirconia (Group Z), hybrid (Group H), titanium (Group T) and anodized yellow titanium (Group AT). MZ and abutment specimens were then cemented. L^*, a^*, and b^* parameters were obtained from MZ, MZ + abutment, and MZ + abutment + cement. ΔE₀₀₁^* (between MZ and MZ + abutment), ΔE₀₀₂^* (between MZ and MZ + abutment + cement) and ΔE₀₀₃^* (between MZ + abutment and MZ + abutment + cement) values were calculated. Statistical analyses included 2-way ANOVA, Bonferroni, and Paired Sample t-Tests (P < .05).

RESULTS

Abutment types and resin cements had significant effect on L^*, a^*, b^*, ΔE₀₀₁^*, ΔE₀₀₂^*, and ΔE₀₀₃^* values (P < .001). Without cementation, whereas zirconia abutment resulted in the least discoloration (ΔE₀₀₁^* = 0.68), titanium abutment caused the most discoloration (ΔE₀₀₁^* = 4.99). The least ΔE₀₀₂^* = 0.68 value was seen using zirconia abutment after cementation with yellow shaded cement. Opaque shaded cement caused the most color change (ΔE₀₀₃^* = 5.24). Cement application increased the L^* values in all groups.

CONCLUSION

The least color change with/without cement was observed in crown configurations created with zirconia abutments. Zirconia and hybrid abutments produced significantly lower ΔE₀₀₂^* and ΔE₀₀₃^* values in combination with yellow shaded cement. The usage of opaque shaded cement in titanium/anodized titanium groups may enable the clinically unacceptable ΔE₀₀^* value to reach the acceptable level.

The Effect of UV Treatment on Surface Contact Angle, Fibroblast Cytotoxicity, and Proliferation with Two Types of Zirconia-Based Ceramics

UV photofunctionalization of Zirconia-based materials for abutment fabrication is a promising approach that might influence the formation of a sound peri-implant seal, thus promoting long-term soft and hard tissue implant integration. This study aimed to evaluate the effect of UV treatment of test specimens made by two different ZnO₂-based ceramic materials on the hydrophilicity, cell cytotoxicity, and proliferation of human gingival fibroblasts (HGFs). Two Zirconia-based materials, high-translucent and ultra-translucent multi-layered Zirconia (Katana, Kuraray Noritake, Japan), were used to prepare a total of 40 specimens distributed in two equally sized groups based on the material (n = 20). The same surface finishing protocol was applied for all specimens, as suggested by the manufacturer. Half the specimens from each group were treated with UV-C light for 48 h. Water contact angle (WCA), fibroblast cytotoxicity, and proliferation were investigated. The WCA values for the high-translucent Zirconia ranged from 69.9° ± 6.4° to 73.7° ± 13.9° for the treated/non-treated specimens and from 79.5° ± 12.8° to 83.4° ± 11.4° for the ultra-translucent multi-layered Zirconia, respectively. However, the difference was insignificant (F(16) = 3.50, p = 0.292). No significant difference was observed for the fibroblast cytotoxicity test. The results for proliferation revealed a significant difference, which was material-dependent (F(8) = 9.58, p = 0.005). We found that UV surface photofunctionalization of ZrO₂-based materials alters the human gingival fibroblast cell viability, which might produce favourable results for cell proliferation.

Cemented versus screw-retained zirconia-based single implant restorations: 5-year results of a randomized controlled clinical trial

Objectives

To compare cemented and screw‐retained one‐piece zirconia‐based restorations in terms of clinical, radiographic, and technical outcomes 5 years after insertion.

Materials and methods

Thirty‐four patients with single‐tooth implants were randomly restored with either a cemented lithium disilicate crown on a one‐piece customized zirconia abutment (CEM, 17 patients) or a screw‐retained crown based on a directly veneered one‐piece customized zirconia abutment (SCREW, 16 patients). All patients were recalled for a baseline examination (7–10 days after crown insertion) and then annually up to 5 years. The following outcomes were assessed: marginal bone level (changes), technical, and clinical (bleeding on probing, plaque control record, probing depth, and keratinized tissue) parameters. The Mann–Whitney U‐test was used to assess differences between the two groups.

Results

At 5 years, 26 patients (13 in each group) were re‐examined. The survival rates on the implant and restorative levels were 100% and 82.4% (equally for both groups), respectively. At 5 years, the median marginal bone level was located at −0.15 mm (IQR: −0.89 mm; 0.27 mm) (CEM) and −0.26 mm (IQR: −0.38 mm; 0.01 mm) (SCREW) below the implant shoulder (intergroup p = .9598). The median changes between baseline and the 5‐year follow‐up amounted to −0.23 mm (CEM; intragroup p = .0002) and −0.15 mm (SCREW; intragroup p = .1465) (intergroup p = .1690). The overall technical complication rate at 5 years was 15.4% (CEM) and 15.4% (SCREW) (intergroup p = 1.00). Clinical parameters remained stable over time (baseline to 5 years).

Conclusions

At 5 years, screw‐retained and cemented restorations rendered largely the same clinical, technical, and radiographic outcomes. Technical complications were frequent in both groups.

Influence of zirconia/glass veneer thickness and implant abutment material on the final shade of implant restorations

Aim

The aim of this study was to investigate the combined effect of ceramic material, ceramic thickness, and implant abutment background to the final color of restorations.

Settings and Design

This was a comparative in vitro study.

Materials and Methods

Three different types of monolithic and porcelain-veneered zirconia disc-shaped specimens (Prettau Anterior, VITA YZ ST, and VITA YZ HT) were prepared in A3 shade with two different thicknesses (1 mm and 1.5 mm) (n = 10). Each zirconia material was made of 4-mm thickness as a control specimen of each monolithic zirconia type, and 4-mm thick veneering ceramic (VITA VM9 Base Dentine) was made as a control for veneered zirconia groups. Three simulated implant abutments were fabricated from titanium, white-shaded and yellow-shaded zirconia. The zirconia specimens were placed on different abutment backgrounds, and the color difference (ΔE) between experimental and control specimens was measured.

Statistical Analysis Used

The three-way ANOVA and the Scheffé test were used for data analysis (α = 0.05).

Results

The mean ΔE values between two thicknesses were significantly different in every background for all zirconia materials. The ΔE values of zirconia specimens on yellow zirconia were lower than those of other abutments. The clinically acceptable ΔE value (ΔE <3) was found in some monolithic zirconia specimens on white-shaded and yellow-shaded abutments, while the ΔE value is approximately 3 or less in all 1.5-mm thick porcelain-veneered zirconia groups.

Conclusions

Different zirconia materials on implant abutments affected the final color of restorations. To achieve satisfactory color, the minimum thickness of zirconia restorations should be at least 1.5 mm on yellow zirconia abutment.

Fatigue fracture resistance of titanium and chairside CAD-CAM zirconia implant abutments supporting zirconia crowns: An in vitro comparative and finite element analysis study

STATEMENT OF PROBLEM

Zirconia abutments with a titanium base are promising candidates to substitute for titanium abutments based on clinical studies reporting good short-term survival rates. However, information on the long-term performance of zirconia abutments supporting ceramic crowns is scarce.

PURPOSE

This in vitro comparative and finite element analysis study compared the fatigue life performance of ceramic computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic restorations and zirconia abutments fabricated with a chairside workflow connected to a titanium interface versus titanium abutments.

MATERIAL AND METHODS

Twenty-two internal connection implants were divided into 2 groups, one with a zirconia abutment and monolithic ceramic zirconia crown (ZZ) and the other with a titanium abutment and zirconia crown (TiZ). They were subjected to a fatigue test to determine the fatigue limit and fatigue performance of each group as per International Organization for Standardization (ISO) 14801. Microstructural analysis of the fracture surfaces was conducted by using a scanning electron microscope (SEM). Simulations of the in vitro study were also conducted by means of finite element analysis (FEA) to assess the stress distribution over the different parts of the restoration.

RESULTS

The fatigue limit was 250 N for the TiZ group and 325 N for the ZZ group. In both groups, the screw was the part most susceptible to fatigue and was where the failure initiated. In the zirconia abutment models, the stress on the screw was reduced.

CONCLUSIONS

Chairside CAD-CAM zirconia abutments with a titanium base supporting zirconia crowns had higher fatigue fracture resistance compared with that of titanium abutments.

Optical effect of resin cement, abutment material, and ceramic thickness on the final shade of CAD-CAM ceramic restorations

STATEMENT OF PROBLEM

High-translucency ceramics can be influenced by the underlying structure, altering the restoration shade. How this affects color matching is unclear.

PURPOSE

The purpose of this in vitro study was to investigate the optical effects of cement shade, ceramic type, ceramic thickness, and abutment material on the final color of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic restorations.

MATERIAL AND METHODS

Two shades of resin cement (yellow, translucent), 3 types of background (titanium, white zirconia, yellow zirconia), and 3 types of high-translucent ceramic (each type shade A1 and A3) were used in this study. For the experimental groups, a total of 72 ceramic specimens were produced across 4 groups based on ceramic thickness (1.0 mm, 1.5 mm, and 2.0 mm). For the control groups, each ceramic type and shade was prepared at a thickness of 4 mm. A total of 8 resin cement specimens were produced in 4 groups based on shade by using a plastic mold (12×12×0.2 mm). To demonstrate the effect of implant abutment materials, 3 types of background were fabricated with a thickness of 2 mm. For the experimental groups, 3 specimens (ceramic, cement, and background) were sequentially placed with glycerin in the center of each background specimen. Color measurements of the experimental groups were made with a spectrophotometer and recorded in the Commission Internationale de l'Eclairage Lab coordinate system. The color differences (ΔE) between experimental and control groups were then calculated. The Kruskal-Wallis test (α=.05) was used to analyze the multiple comparisons of ceramic thickness, ceramic type, and abutment material. The Mann-Whitney U test (α=.05) was used to analyze cement shade.

RESULTS

Significant differences were found for different ceramic thicknesses, ceramics types, and abutment materials (P≤.001). A clinically acceptable shade (ΔE≤3) was found in 1.5- and 2.0-mm ceramics with the titanium and 2.0-mm ceramics with the yellow zirconia background. However, the color between the experimental group and the control group was similar when using the 2 cement shades (P>.05).

CONCLUSIONS

An increase in ceramic thickness could minimize alteration of the final shade. High-translucency ceramics, together with a resin cement, were able to successfully mask titanium with a ceramic thickness of at least 1.5 mm. However, only a ceramic with a thickness of 2.0 mm was able to mask the yellow zirconia background.

Influence of electronic nicotine delivery systems (ENDS) in comparison to conventional cigarette on color stability of dental restorative materials

Objective:

The use of Electronic Nicotine Delivery Systems (ENDS) is increasing rapidly. However, its discoloring effect on dental restorations is not known. This study aimed to evaluate the effect of ENDS aerosol when compared to conventional cigarette smoke (CS) on the color stability of dental ceramic (DC) and resin composite (RC).

Methods:

This research project was conducted from November 2018 to May 2019. In this study 30 discs each for DC and RC materials were fabricated to be equally divided into groups of exposure to CS, ENDS aerosol and storage in distilled water (No smoke; NS) respectively (n=10). Specimens were exposed for a total of 7 days, with a rate of 10 cycles per day, each cycle represented 10 puffs. The color change was assessed using the CIELAB color space, by calculating ΔE. Data was analysed using ANOVA and multiple comparisons test.

Results:

Ceramic specimens in CS (2.422 ± 0.771) and ENDS (2.396 ± 0.396) groups showed comparable ΔE (color change) (p=0.992). Similarly, composite specimens in CS (42.871 ± 2.442) and ENDS (46.866 ± 3.64) groups showed comparable ΔE (p>0.05). NS specimens in both composite and ceramic samples showed lower ΔE than CS and ENDS specimens respectively.

Conclusions:

Aerosol from Electronic nicotine delivery systems (ENDS) showed similar discoloration levels as cigarette smoking (CS). The level of discoloration for ceramic samples for both ENDS and CS was below clinically perceptible levels (Mean ΔE < 2.5). Discoloration of composite resin due to CS and ENDS was visually perceptible (Mean ΔE > 4.0).

Cement opacity and color as influencing factors on the final shade of metal-free ceramic restorations

OBJECTIVE

To investigate the influence of opacity and color of luting cements on the final shade of metal-free restorations.

MATERIALS AND METHODS

Five resin cement colors in combination with four different thicknesses of CAD/CAM ceramic materials were tested, and a composite substrate was used as dentin color reference (n = 3). Specimen color was measured with a spectrophotometer equipped with an integrating sphere before and after cementation (CIELAB). Cement and ceramic color and opacity (TP) were assessed by measuring the tested ceramic thickness as a 1-mm thick disk for each of the cement shades. The differences in color were evaluated (ΔE₀₀ ). Data were statistically analyzed by a Two-Way ANOVA followed by the Tukey Test for post-hoc comparison (P < .05) and multiple comparison Pearson's test (P < .05); the acceptability and perceptibility threshold were evaluated.

RESULTS

Statistically significant influence was found for factors ceramic thickness and cement shade (P < .001). Perceptible and unacceptable color changes were induced on the final restoration by resin cements (ranging from ΔE₀₀  = 0.69 ± 0.54 to ΔE₀₀  = 5.53 ± 0.46), the correlation between factors became strong (r²  > 0.6) in case of mismatch between color and translucency of cement and ceramic. Only the clear shade in combination with the thickest ceramic, resulted in an imperceptible color change (ΔE₀₀  = 0.69 ± 0.54).

CONCLUSIONS

The final shade of ceramic restorations can be influenced by resin cements; the magnitude of influence is related to the cement optical properties.

CLINICAL SIGNIFICANCE

In order to influence the final shade of a ceramic restoration, a cement more opaque than the restorative material should be used. Conversely, in the case of a fitting shade of the restoration, a cement more translucent than the restoration should be used to avoid undesired changes.

Colour stability and surface properties of high-translucency restorative materials for digital dentistry after simulated oral rinsing

High-translucency restorative materials are commonly used in the restoration of anterior teeth where aesthetics is a critical factor. In this in vitro study, the impact of mouthwash on the colour stability and surface characteristics of high-translucency computer-aided design and computer-aided manufacturing (CAD-CAM) dental restorative materials was evaluated. Two-hundred specimens were fabricated from five high-translucency CAD-CAM materials: a resin nano ceramic; a polymer-infiltrated ceramic network; a feldspathic ceramic; a lithium disilicate glass ceramic; and high-translucency zirconia. Each group of ceramic specimens was then divided into four subgroups: conventional mouthwash (LISTERINE); whitening mouthwash (LISTERINE Healthy White); chlorhexidine gluconate; and distilled water. Oral rinsing was simulated at 100 rpm for 180 h, representing 15 yr of clinical simulation. The specimens were then evaluated for colour, translucency, gloss, roughness, and surface morphology. Two-way ANOVA and linear mixed models were used for intergroup comparisons (α = 0.05). The polymer-infiltrated ceramic network and feldspathic ceramic became brighter, more opaque, less glossy, and rougher after rinsing with the whitening mouthwash. The long-term use of specific mouthwashes can cause deterioration of the optical and surface properties of high-translucency CAD-CAM dental restorations.

Optical and Surface Properties of Monolithic Zirconia after Simulated Toothbrushing

This in vitro study investigated the impact of various dentifrices on the shade, translucency, gloss, and surface characteristics of polishing- or glazing-finished monolithic zirconia surfaces after simulated toothbrushing. Eighty square-shaped monolithic zirconia specimens were divided into two major groups based on the finishing methods—polished (P) and glazed (G). Next, specimens from the two major groups were categorized into four subgroups: stored in distilled water (DW, control); brushed with a fluoride-free conventional dentifrice (C); brushed with a fluoride dentifrice (F); and brushed with a whitening dentifrice (W). Overall, eight groups were created—PDW, PC, PF, PW, GDW, GC, GF, and GW (n = 10 each). Shade, translucency, surface gloss, surface roughness, crystalline phase, and superficial topography data were obtained. Repeated-measures ANOVA and two-way ANOVA were used for intergroup comparison (all α = 0.05). The color differences (ΔE₀₀) between pre- and posttreatment were 0.3158 (PDW), 0.7164 (PC), 0.7498 (PF), 0.8106 (PW), 0.1953 (GDW), 0.301 (GC), 0.3051 (GF), and 0.4846 (GW). A statistically significant difference was observed among the ΔE₀₀, surface gloss, and surface roughness of monolithic zirconia. Thus, brushing with several dentifrices markedly affects the optical properties and surface characteristics of monolithic zirconia finished with polishing or glazing methods.

Influence of implant abutment material and ceramic thickness on optical properties

STATEMENT OF PROBLEM

Anterior shade matching is an essential factor influencing the esthetics of a ceramic restoration. Dentists face a challenge when the color of an implant abutment creates an unsatisfactory match with the ceramic restoration or neighboring teeth.

PURPOSE

The purpose of this in vitro study was to evaluate the influence of abutment material and ceramic thickness on the final color of different ceramic systems.

MATERIAL AND METHODS

Four experimental and control ceramic specimens in shade A3 were cut from IPS e.max CAD, IPS Empress CAD, and VITA Suprinity PC blocks. These specimens had thicknesses of 1.0 mm, 1.5 mm, 2.0 mm, and 2.5 mm, respectively, for the experimental groups, and 4 mm for the controls. Background abutment specimens were fabricated to yield 3 different shades: white zirconia, yellow zirconia, and titanium at a 3-mm thickness. All 3 ceramic specimens in each thickness were placed in succession on different abutment backgrounds with glycerin optical fluid in between, and the color was measured. A digital spectrophotometer was used to record the specimen color value in the Commission Internationale De L'éclairage (CIELab) color coordinates system and to calculate the color difference (ΔE) between the control and experimental groups. The Kruskal-Wallis test was used to analyze the effect of ceramic thickness on different abutments, and the pair-wise test was used to evaluate within the group (α=.05).

RESULTS

The color differences between the test groups and the control decreased with increasing ceramic thickness for every background material. In every case, significant differences were found between 1.0- and 2.5-mm ceramic thicknesses. Only certain 2.5-mm e.max CAD, VITA Suprinity PC, and Empress CAD specimens on yellow-shade zirconia or VITA Suprinity PC on titanium were identified as clinically acceptable (ΔE<3).

CONCLUSIONS

Increasing ceramic restoration thickness over the abutment background decreased the color mismatch. Increasing the thickness of ceramic on a yellow-shaded zirconia abutment rather than on titanium or white zirconia yielded a more esthetic color for the whole restoration.