Harmonizing color measurements in dentistry using translucent tooth-colored materials.

BACKGROUND: Since color measurements are relative, the discrepancy among different instruments is alarmingly high. This multicenter study evaluated the effectiveness of instrument calibration and inter-instrument harmonization of different spectrophotometers with the same optical geometry using tooth-colored, translucent dental materials. METHODS: The coordinating center (CC) spectrophotometer was calibrated using the NPL Ceram Series II set. Two sets of 10 specimens, labeled 1 to 10 and I to X (10 mm in diameter and 1 mm thick), were tested at CC and three research sites (RS1, RS2, and RS3) using the same d/8° optical geometry spectrophotometers. Calibration factors were calculated for each material and site to obtain the average calibration factors for sets 1-10, set I-X, and the combination of both. The differences among the non-corrected and corrected reflection values were calculated using CIEDE2000 (DeltaE00) and CIELAB (DeltaEab) color difference formulas and were submitted to ANOVA and Tukey test (α = 0.05). RESULTS: A significant decrease of color differences between non-corrected as compared to corrected measurements was recorded for all CC-RS and RS-RS comparisons. The reduction of DeltaE00 values between non-corrected and corrected for CC-RS1, CC-RS2, and CC-RS3 were 83.1%, 77.2%, and 73.6%, respectively. The corresponding DeltaE00 values for RS1-RS2, RS1-RS3, and RS2-RS3 comparisons, indirectly compared in the experiment, were 84.2%, 82.8%, and 68.5%, respectively. There was a significant reduction of DeltaE00 and DeltaEab color difference for all combined RS pairs and each of three RS pairs, corrected with one of two specimen sets calibration factors separately. CONCLUSIONS: Calibration and harmonization of color measurements in dentistry using tooth-colored, translucent restorative materials significantly decreased measurement discrepancies between the coordinating center and research sites and among pairs of research sites.

Color stability of a resin nanoceramic after surface treatments, adhesive cementation, and thermal aging.

STATEMENT OF PROBLEM: Whether color changes in resin nanoceramic (RNC) restorations can occur because of material and adhesive interface degradation is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the color of RNCs submitted to surface treatments, cementation, and aging. MATERIAL AND METHODS: RNC specimens (N=120) were produced with a thickness of 0.5 mm. The No Treatment-High/Low Translucency (NT-HT/LT) groups did not receive treatments; the Airborne-particle Abrasion-High/Low Translucency (AA-HT/LT) groups were airborne-particle abraded, and the Airborne-particle Abrasion Silane-High/Low Translucency (AASIL-HT/LT) groups received airborne-particle abrasion and a silane agent. Single specimens (n=60) were measured on a spectrophotometer before and after aging (50 000 cycles). The other half was mounted on composite resin bases and measured. The cleaned specimens were cemented (C) on the bases and measured (T0 and T1). ΔE00, ΔL', ΔC', and ΔH' were obtained by using the CIEDE2000 formula and analyzed by using ANOVA and repeated-measures ANOVA. Multiple comparisons were made by using the Tukey HSD test (α=.05). RESULTS: For single specimens, the greatest ΔE00 values were observed in the AA-T1-LT resin (5.87). For mounted and cemented conditions, the greatest ΔE00 values were found in the AA-C-T1-LT resin (1.74), and the ΔE00 ranged from 0.75 (NT-OL) to 1.44 (AASIL-C-T1) for the HT resin (P<.001). The mounted and cemented specimens tended toward red and yellow, whereas lighter specimens were observed after cementation. CONCLUSIONS: Aging affected the color of the RNCs evaluated. The single specimens showed greater color differences than the cemented specimens, reinforcing the importance of the adhesive cement in the optical behavior of thin restorations.

Transmittance of visible and blue light through zirconia.

The aim of this study was to evaluate the transmittance of visible light (VL) (λ: 400-700 nm) and blue light (BL) (λ: 360-540 nm) through six CAD/CAM zirconia blanks (ZiB) in comparison to a lithium disilicate ceramic (LS2). Disks of the zirconia materials Bruxzir (BX), Cercon (CE), Lava Frame (LF), Lava Plus (LP), Prettau (PT), Zenostar (ZS) and LS2 (EM) were manufactured and the transmittance was measured in a spectrophotometer. ZS, followed by CE, PT, LP, LF, and BX showed the lowest transmittance of VL and BL. The highest transmittance was shown by EM. The transmittance of BL was lower than that of VL in all groups. EM ceramics showed higher transmittance than all zirconia materials and the thickness of zirconia materials influenced the transmittance values. Knowledge about VL and BL transmittance would help clinicians to individually tailor the selection of material to the specific indication and to make the right choice regarding the luting procedure and light curing duration.

Impact of laboratory treatment with coloring and fluorescent liquids on the optical properties of zirconia before and after accelerated aging.

STATEMENT OF PROBLEM: Laboratory procedures, such as dipping in coloring and fluorescent liquids, can be used to improve the optical properties of zirconia. However, information is lacking on the effect of these liquids. PURPOSE: The purpose of this in vitro study was to evaluate the color differences and degree of fluorescence of zirconia (3Y-TZP) treated with coloring and fluorescent liquids before and after an accelerated aging protocol. MATERIAL AND METHODS: Forty disk-shaped specimens of 3Y-TZP were fabricated by milling and separated according to the laboratory treatment performed: white zirconia (control group); zirconia treated with coloring liquid (A2 group); zirconia treated with fluorescent liquid (fluorescent group); and zirconia treated with both liquids (A2 fluorescent group). The L*a*b* coordinates before aging (T0) were obtained with a spectrophotometer, and the degree of fluorescence was measured. The disks were subjected to accelerated aging for 1 hour (T1) and 5 hours (T2). Measurements were made before and after each time interval. Color differences (ΔE00) were calculated using the CIEDE2000 formula and analyzed by 2-way ANOVA. Lightness (ΔL'), chroma (ΔC'), and hue differences (ΔH') were analyzed by multivariate ANOVA. Degrees of fluorescence were obtained as percentages and were analyzed by 2-way ANOVA. Multiple comparisons were performed by the Tukey HSD test (α=.05). RESULTS: Color differences were observed when 3Y-TZP disks were treated with coloring (7.91 ΔE00), with fluorescent liquid (5.81 ΔE00), and with both liquids (5.52 ΔE00). Accelerated aging resulted in color differences in the T2 A2 group (6.74 ΔE00) and at both times evaluated in the fluorescent group (T1=8.59 ΔE00 and T2=8.47 ΔE00) (P<.001). In the A2 fluorescent group, the degree of fluorescence was not influenced significantly (P>.05). The use of fluorescent liquid influenced the degree of fluorescence in the fluorescent group (T0=20%). CONCLUSIONS: Significant differences in color, lightness, chroma, and hue were achieved in all tested groups before and after aging. The degree of fluorescence was statistically different only in the fluorescent group and was not influenced by accelerated aging.

Combining Esthetic Layering and Lithium Disilicate Sintering Technique on Zirconia Frameworks: A Veneering Option to Prevent Ceramic Chipping.

Major and minor chipping of veneering porcelain are two of the most frequent complications in all-ceramic restorations with zirconia frameworks. In cases of major chipping, replacement of the affected restoration may be necessary. High-strength lithium disilicate ceramic offers new options to serve as veneering material in a sintering technique or as repair material for chipping in combination with the adhesive technique. The purpose of three case presentations here was to describe the use of lithium disilicate ceramic on zirconia frameworks for reliable and esthetic veneering in the posterior region and to repair extended chipping in conventional veneering materials.

Oral features and computerized rehabilitation of a young patient with CHARGE syndrome using minimally invasive long-term interim CAD-CAM restorations.

Patients with CHARGE syndrome (where CHARGE stands for coloboma of the iris or retina, heart defects or cardiac malformations, atresia/stenosis of the choanae, retardation of growth and development, genital anomalies, and ear abnormalities) present several orofacial anomalies. Their treatment depends on the specific type of manifestation. To perform the complex oral rehabilitation and achieve a conservative, esthetic, and functional exploration of the definitive treatment goal, computer-aided design and computer-aided manufacturing (CAD-CAM) polymers can be used as long-term interim restorations. This article reports the treatment of a young patient with CHARGE syndrome combined with oral alterations. CAD-CAM polymers offer an intermediate treatment with satisfying esthetics and function at low biological cost until bone growth is completed. This period facilitates additional planning for the definitive restoration.

Laboratory and clinical considerations on prosthetic zirconia infrastructures for implants.

Zirconia is a ceramic material that is used for constructing prosthetic infrastructures and implant abutments using CAD/CAM techniques. Although good initial mechanical properties are obtained with zirconia that is partially stabilized by yttrium, it may age in a moist environment, compromising such properties and, consequently, the longevity of the restorative work. To optimize the longevity of this material, it is essential that the clinician and laboratory technician understand its mechanical properties and limitations and take specific precautions needed to maintain its mechanical properties and ensure long-term performance especially in implant prosthetics. This article presents a clinical case where these precautions were taken, emphasizing the key surface treatments advocated for zirconia.

Influence of different maintenance times of torque application on the removal torque values to loosen the prosthetic abutment screws of external hexagon implants.

PURPOSE: To analyze the torque application on prosthetic abutment screws using different maintenance times, to determine an influence on the removal torque values. MATERIALS AND METHODS: A total of 40 external hexagon implants, 40 titanium screws, and 40 customized abutments were used. In group 1, the screws received a torque of 30 N·cm by instant torque application; in groups 2, 3, and 4, torque of 30 N·cm was applied and maintained for 10, 20, and 30 seconds, respectively. Removal torque was performed 10 minutes after torque application. Data were statistically analyzed using 1-way ANOVA and Tukey HSD test (α = 0.05). RESULTS: The mean and standard deviation (±SD) of removal torque values found were 11.61 ± 1.43 N·cm for group 1; 18.64 ± 1.71 N·cm for group 2; 21.62 ± 0.97 N·cm for group 3; and 21.48 ± 1.55 N·cm for group 4. Groups 3 and 4 exhibited statistically higher values than group 2, which demonstrated significantly higher values than group 1 (P < 0.05). CONCLUSIONS: A torque of 30 N·cm applied for 20 seconds seemed to be the best option when considering the removal torque values of external hexagon implants.

Cirugía guiada en implantología / Guided surgery in implantology practice

En la implantología han sido realizadas cirugías con el auxilio de tomografías computarizadas asociadas a tecnología CAD/CAM. Las imágenes digitales obtenidas permiten que los profesionales realicen una planeación quirúrgica virtual en software específicos, obteniendo como resultado una guía prototipada que permite la realización de una cirugía con un menor tiempo clínico, sin colgajos y suturas, y con un excelente resultado postoperatorio. El objetivo de este artículo es presentar la secuencia de un caso clínico donde los implantes fueron posicionados por cirugía guiada.

In the field of implantology, surgical procedures have been performed with the assistance of computerized tomographies associated to the CAD/CAM technology. Digital images thus obtained, allow professionals to perform virtual surgical planning in specific software. This results in a prototyped guide which enables surgical procedures to be achieved in lesser clinical time, without flaps or sutures, yielding excellent post-operative results. The aim of the present article was to present the sequence of a clinical case in which implants were placed using guided surgery.

Strain gauge analysis of the effect of porcelain firing simulation on the prosthetic misfit of implant-supported frameworks.

OBJECTIVES: This study investigated the effect of porcelain firing on the misfit of implant-supported frameworks and analyzed the influence of preheat treatment on the dimensional alterations. MATERIALS AND METHODS: Four external-hex cylindrical implants were placed in polyurethane block. Ten frameworks of screw-retained implant-supported prostheses were cast in Pd-Ag using 2 procedures: (1) control group (CG, n = 5): cast in segments and laser welded; and test group (TG, n = 5): cast in segments, preheated, and laser welded. All samples were subjected to firing to simulate porcelain veneering firing. Strain gauges were bonded around the implants, and microstrain values (µÎµ = 10⁻6ε) were recorded after welding (M1), oxidation cycle (M2), and glaze firing (M3). Data were statistically analyzed (2-way analysis of variance, Bonferroni, α = 0.05). RESULTS: The microstrain value in the CG at M3 (475.2 µÎµ) was significantly different from the values observed at M1 (355.6 µÎµ) and M2 (413.9 µÎµ). The values at M2 and M3 in the CG were not statistically different. Microstrain values recorded at different moments (M1: 361.6 µÎµ/M2: 335.3 µÎµ/M3: 307.2 µÎµ) did not show significant difference. CONCLUSIONS: The framework misfit deteriorates during firing cycles of porcelain veneering. Metal distortion after porcelain veneering could be controlled by preheat treatment.