Effect of mouth rinses on the stainability of monolithic lithium disilicate glass-ceramics with different surface treatments: An in vitro study.

STATEMENT OF PROBLEM: Mouth rinses have been reported to cause tooth surface discoloration. However, information regarding their effect on the stainability of monolithic glass-ceramics with different surface treatments is lacking. PURPOSE: The purpose of this in vitro study was to assess the effect of mouth rinses on the color change of milled and pressed monolithic lithium disilicate glass-ceramics with different surface treatments. MATERIAL AND METHODS: Fifty-six Ø12×1.5-mm disk specimens were fabricated using 2 different processing techniques: milling and pressing. Each group was subdivided into 2 subgroups according to surface treatments: glazed and polished. Specimens were then immersed in 2 different types of mouth rinse (n=7): chlorhexidine (CHX) and Listerine (LST). Color parameters were assessed using a digital spectrophotometer. Color difference (ΔE00) was calculated and compared with perceptibility (ΔE00=0.8) and acceptability (ΔE00=1.8) thresholds. The data were analyzed using ANOVA and Tukey post hoc tests (α=.05). RESULTS: The color difference (ΔE00) was significantly affected by the type of processing technique, surface treatment, and mouth rinse (P<.001) and their interaction (P=.008). All ΔE00 values were below the selected clinical acceptability threshold (ΔE00=1.8). Milled groups (ΔE00=1.13) showed greater discoloration than pressed groups (ΔE00=0.86). Glazed specimens (ΔE00=0.70) were more resistant to discoloration than polished specimens (ΔE00=1.28) and immersion in CHX (ΔE00=1.09) led to more discoloration than immersion in LST (ΔE00=0.89). CONCLUSIONS: The color of milled and pressed monolithic lithium disilicate glass-ceramics with different surface treatments was affected by using CHX and LST mouth rinses. Glazed lithium disilicate glass-ceramics showed less staining compared with those that were polished. Specimens immersed in CHX showed more discoloration than those immersed in LST.

Effect of sintering time on microstructure and optical properties of yttria-partially stabilized monolithic zirconia.

OBJECTIVES: To evaluate the impact of speed sintering on the microstructure and optical properties of 3 and 5 mol% yttria-partially stabilized monolithic zirconias. METHODS: 120 plate-shaped zirconia specimens (10x10x 0.4 mm) were prepared from three commercial 5 mol% yttria-partially stabilized zirconia blocks (5Y-PSZs); Katana UTML (Kuraray Noritake), Cercon xtML (Dentsply Sirona), and Zolid FX white (Amann Girrbach), and two commercial 3 mol% yttria-partially stabilized zirconia blocks (3Y-PSZs); Lava Plus (3 M ESPE) and InCoris (Sirona, GmbH). Specimens were either conventional sintered (CS) using a 7-hour program or speed sintered (SS) using a quick 90-minute program. The microstructure was inspected with a scanning electron microscope (SEM), and phase fractions were detected using x-ray diffraction analysis (XRD). Translucency (TP00), and contrast ratio (CR) were obtained using a spectrophotometer (VITA Easyshade V). Color difference (ΔE00) between both sintering processes was calculated with the CIEDE2000 formula. ΔE00 up to 1.8 was set as the acceptability threshold. Data were analyzed using two-way ANOVA, Krusakll-Wallis, and Mann-Whitney U tests. (n = 12, α = .05). RESULTS: Grain size was significantly decreased after SS for all tested materials (P < .0001). The average grain sizes of 5Y-PSZs were significantly larger than those of 3Y-PSZs. The atomic structure, microstructure, and transparency of CS and SS were all affected by the amount of yttria, the size of the crystals, and tetragonality. SS significantly reduced TP00 (F = 7135.95, P < 0.0001) and increased CR (F = 453.21, P < 0.0001). The CS Katana presented the highest TP00 and lowest CR value. ΔE00 between the CS and SS groups were clinically acceptable except for Lava, which had values above the set threshold (1.89). SIGNIFICANCE: SS altered the grain size and internal structure of the tested materials, which was reflected in translucency.

Effect of pattern materials and fabrication techniques on the color of a pressed lithium disilicate ceramic: An in vitro study.

STATEMENT OF PROBLEM: Pattern materials and their fabrication techniques have been reported to affect the marginal accuracy and internal fit of pressed lithium disilicate ceramic restorations. However, information regarding their effect on the color of such restorations is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the color of a pressed lithium disilicate glass-ceramic fabricated from wax or resin patterns by using conventional and milling techniques. MATERIAL AND METHODS: Fifty-six Ø14×1.5-mm disk pattern specimens were divided into 4 groups based on the pattern material and fabrication technique: conventional wax pattern group (CW), conventional resin pattern group (CR), milled wax pattern group (MW), and milled resin pattern group (MR). Lithium disilicate specimens were fabricated by using the lost wax technique. The CIELab values were measured with a spectrophotometer (VITA Easyshade Advance). The ΔE00 values were calculated and compared with perceptibility (ΔE00=0.8) and acceptability (ΔE00=1.8) thresholds to interpret the color differences. The 2-way ANOVA and Tukey post hoc tests were used to analyze data (α=.05). RESULTS: Two-way ANOVA revealed that ΔE00 was significantly affected by the pattern material (P<.001), fabrication technique (P=.034), and their interaction (P<.001). The ΔE00 of the CW group (0.76 ±0.04) was clinically imperceptible. No significant difference in the ΔE00 values was found between the reference and the MW (1.48 ±0.13) and MR (1.51 ±0.15) groups (P=.926), which were both clinically perceptible and acceptable. The highest ΔE00 was that of the CR group (2.06 ±0.22). CONCLUSIONS: The color of the pressed lithium disilicate ceramic was influenced by the wax and resin pattern materials fabricated by using conventional or computer-aided design and computer-aided manufacturing (CAD-CAM) techniques. Only the CW pattern group showed color differences below the clinically perceptible threshold (ΔE00=0.8). The CR pattern group showed the highest color differences, which were not clinically acceptable.

A device to facilitate separation of components of combined screw- and cement-retained implant-supported crowns.

This article describes a technique to separate parts of cemented implant-supported restorations with a screw hole. A device was designed by using a computer-aided design (CAD) program and was milled in a milling center. The restoration was heated to 400 °C and then subjected to controlled mechanical force with the help of the device to separate the cemented parts.

Fabrication of a CAD-CAM custom healing abutment guided by a conventional dental radiograph for delayed loaded dental implants: A dental technique.

This article describes a technique for fabricating a custom anatomic healing abutment for delayed loaded implants by using the computer-aided design and computer-aided manufacturing (CAD-CAM) technology from a polymethyl methacrylate (PMMA) blank. The dimensions of the custom healing abutment are measured from a conventional dental radiograph and diagnostic casts. The healing abutment is used in the second surgical stage to guide soft tissue healing. The resulting soft tissue contour guides the design of the mucosal part of the custom implant abutment.

Effect of additional pressing on the color and translucency of pressable ceramic materials: An in vitro study.

STATEMENT OF PROBLEM: Whether reusing the buttons of pressable ceramic materials affects their color or translucency is unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of additional pressing on the color and translucency of 3 different lithium disilicate ceramic brands. MATERIAL AND METHODS: Seventy-two disk-shaped ceramic specimens (Ø14×1.5 mm) were divided into 2 groups: pressed group and additionally pressed group, each containing 36 specimens. These groups were further divided into 3 subgroups: lithium disilicate (LDS), lithium disilicate with high-density micronization technology (LDS-HDM), and zirconia-reinforced lithium silicate (ZLS). Pressing was performed in the press group yielding 36 pressed specimens. Additional pressing was performed by using the buttons resulting from the press group, yielding 36 additionally pressed specimens. Color differences and translucency between pressed and additionally pressed groups were measured with a portable spectrophotometer (VITA Easyshade Compact). The translucency parameter (TP) was measured on black and white backgrounds. Color differences between the 2 groups were analyzed statistically by using the Kruskal-Wallis nonparametric test followed by the Dunn-Sidek method for individual comparison among means of all groups (α=.05). RESULTS: A statistically significant difference was found in color after additional pressing among the 3 tested materials (P=.005). After additional pressing, color difference (ΔE) values were found between the LDS group (3.78 ±1.11) and the ZLS group (3.03 ±1.44). These ΔE values were beyond the selected clinical perceptible threshold (ΔE=2.6). However, the LDS-HDM group had a ΔE value of 1.80 ±1.22, which is considered clinically not perceivable. Furthermore, LDS showed a statistically significant decrease in translucency after additional pressing (P=.002). However, after additional pressing, ZLS and LDS-HDM showed no statistically significant differences in translucency (P>.05). CONCLUSIONS: The colors of the 3 tested materials were affected by additional pressing. Only LDS-HDM showed color changes below the selected clinically perceptible threshold (ΔE=2.6). Furthermore, only LDS showed a significant decrease in translucency.

Full-mouth rehabilitation following treatment of temporomandibular disorders and teeth-related signs and symptoms.

The literature is replete with theories regarding temporomandibular disorders (TMD). However, there is a paucity of information concerning perceived malocclusion and other teeth-related signs and symptoms after full-mouth rehabilitation. This clinical study was designed to evaluate the perception of TMD patients concerning perceived malocclusion and other teeth-related signs and symptoms after full-mouth rehabilitation guided by the Mental Analog Scale (MAS). Among 38 patients referred for full-mouth rehabilitation, 20 were diagnosed as having TMD after reviewing a questionnaire, recording the major complaints and symptoms, in addition to performing comprehensive clinical examination. Nonsurgical therapy was performed, including fabricating an anterior programming device, a centric relation occlusal device and finally full-mouth rehabilitation by means of placing crowns on all upper and/or lower teeth. All full-mouth rehabilitation procedures were performed using a fully adjustable articulator and mandibular movements were recorded following pantographic tracings. After full-mouth rehabilitation, the patients were followed up at 1, 2, 4, 6, 9, and 12-month intervals, and the major signs and symptoms were recorded along with adjunctive teeth-related signs and symptoms. Fisher exact probability tests were applied to analyze the results (P<.05). Statistical comparisons of the MAS responses before and after treatment (at 1-month recall) showed significant improvement (P<.05) for all teeth-related signs and symptoms except for bruxism (P=.0699). Further improvement was noted at the 4-month recall period. However, these improvements were not statistically significant for all teeth-related signs and symptoms. No further change was noted after the 4-month recall period. There was a marked reduction in perceived malocclusion and adjunctive teeth-related signs and symptoms during function, only after performing occlusal equilibration of the final restorations.

Intrarater repeatability of shade selections with two shade guides.

STATEMENT OF PROBLEM: Color research has shown that shade guides do not always represent the color of natural teeth. Moreover, visual evaluation has been found to be unreliable and inconsistent. PURPOSE: This investigation evaluated the effects of 2 shade guides on the intrarater repeatability (reliability) of prosthodontists and general practitioners with regard to shade selection. MATERIAL AND METHODS: Ten prosthodontists and ten general practitioners (all men, 35-45 years old) with an average practice experience of 14 years participated in this study. Examiners were tested to eliminate color blindness. Each clinician used Vita Lumin Vacuum and Vitapan 3D-Master shade guides to determine the shades of the maxillary right canines of 20 patients following a standard protocol. The identification codes of the shade tabs were masked to prevent shade memory. All teeth were polished before each shade selection, and the selection process was standardized for controlled lighting and procedures. Shade selections were randomly repeated 1 month later by the same practitioners on the same group of patients in accordance with the same shade-selection protocol. Analysis of variance and t tests for individual comparisons among means were performed (P<.05). RESULTS: Significant interactions were found between the effects of shade guide system and specialty training on intrarater repeatability (P<.0001, analysis of variance). The intrarater repeatability of prosthodontists was significantly higher than that of general practitioners when the Vita Lumin Vacuum shade guide was used (P<.0001, t test). Use of the Vitapan 3D-Master shade guide significantly improved the intrarater repeatability of general practitioners compared with the Vita Lumin Vacuum shade guide (P<.0005). This improvement was not significant, however, among prosthodontists (P=.2861). CONCLUSION: Within the limitations of this study, the prosthodontists demonstrated superior intrarater repeatability in shade selection, especially when the Vita Lumin Vacuum shade guide was used. Use of the Vitapan 3D-Master shade guide notably improved intrarater repeatability among the general practitioners.