RESUMEN
To assess the fracture resistance of computer-aided design and computer-aided manufacturing (CAD/CAM) ultratranslucent multilayered zirconia (5Y-YZP) veneers with varying facial thickness. Sixty translucent zirconia veneers were designed and milled using a chairside CAD/CAM system for maxillary central incisors. The butt joint incisal veneer tooth preparations consisted of 1.00 mm incisal reduction, 0.40 mm chamfer margin, and three different facial reductions; 0.50, 0.75, and 1 mm, respectively. The ceramic veneers were cemented to printed resin dies and subjected to thermal cycling. Subsequently, the restorations were loaded with compressive loading force, and fracture occurrences were recorded. Scanning electron microscope (SEM) images of the fractured specimens were captured. The fracture resistance varied among the veneers with different facial thicknesses. Ultratranslucent zirconia veneers with a facial thickness of 1.00 mm exhibited the highest fracture resistance values (742.15 N), followed by those with 0.75 mm facial thickness (673 N). Minimally invasive veneers with 0.50 mm thickness displayed similar fracture resistance as thicker veneers with 0.75 mm. However, veneers with 1.00 mm thickness displayed the highest values. SEM fracture patterns for 0.50 and 0.75 mm display similar and fewer crack lines than 1.00 mm veneers. RESEARCH HIGHLIGHTS: Minimally invasive zirconia veneers exhibit similar fracture resistance to thicker veneers.
RESUMEN
STATEMENT OF PROBLEM: Minimally invasive treatments have gained popularity in recent years. However, research comparing the fracture resistance of lithium disilicate partial coverage veneer restorations with that of ceramic crowns is lacking. PURPOSE: The purpose of this in vitro study was to evaluate and compare the fracture resistance of lithium disilicate restorations fabricated for preparations of various designs. The designs included veneer preparations with finish lines in the upper, middle, and lower third of the facial surface and ceramic crown preparations with margins in the lower third of the facial surface. All restorations were designed and fabricated using a chairside digital workflow. MATERIAL AND METHODS: Four maxillary right central incisor typodont teeth were prepared for partial coverage veneer preparation with the margin in the upper middle third of the facial surface (PU1/3); partial coverage veneer preparation with margin in lower middle third of the facial surface (PL1/3); complete coverage veneer preparation (CV) with margin in the cervical region; and ceramic crown (CC) preparation. Each preparation was scanned, and 15 casts were 3D printed from each scan. A total of 60 lithium disilicate restorations were fabricated (n=15 per group) using a chairside computer-aided design and computer-aided manufacturing (CAD-CAM) system (Primescan and MCXL). The different restorations were cemented to the 3D printed testing dies with a photopolymerizable resin cement. The specimens were artificially aged with 10 000 thermal cycles between 5 and 55 °C with a dwell time of 30 seconds and were loaded to failure using a universal testing machine. The maximum load to fracture was analyzed using a 1-way ANOVA and post hoc Tukey honestly significant difference (HSD) test (α=.05). Additionally, the fracture patterns of the specimens were evaluated with a stereomicroscope for descriptive purposes. RESULTS: The mean fracture resistance of the chairside CAD-CAM lithium disilicate veneers and ceramic crowns was statistically different depending on the design of the restoration (P<.05). Group CC demonstrated the highest fracture resistance values (1440.66 N), followed by CV (929.8 N) and PU1/3 (756.13 N). The lowest value was for PL1/3 (532.4 N). CONCLUSIONS: The fracture resistance measured for the maxillary central incisor partial coverage veneers with margins in the middle third of the facial surface appear capable of resisting average occlusal forces. However, these veneers demonstrated lower fracture resistance values when compared with complete coverage veneers. Further, lithium disilicate crowns demonstrated higher fracture resistance than veneers, irrespective of their design.
RESUMEN
Purpose: Our in vitro comparative study aimed to investigate the impact of thickness and tooth shade background on the translucency of highly translucent zirconia veneers. Materials and Methods: A total of 75 5Y-TZP zirconia veneers of shade A1 were fabricated with thicknesses of 0.50 mm (n = 25), 0.75 mm (n = 25), and 1.0 mm (n = 25). The translucencies were measured on composite resin teeth with shades A1, A2, A3, A3.5, and A4 using a digital color imaging spectrophotometer. Data were analyzed using ANOVA and post hoc Tukey's test (p < 0.05). Results: The translucency values were optimal for the veneers placed over the substrate teeth with shades A1 and A2, regardless of the veneer thickness. Additionally, veneers with a thickness of 0.50 mm exhibited significantly higher translucency than those with thicknesses of 0.75 mm and 1.0 mm. Conclusions: Our study demonstrated that the translucency of the highly translucent zirconia veneers was influenced by both veneer thickness and tooth shade background. The optimal veneer thickness for achieving the highest translucency was 0.50 for the veneers with A1 and A2 shades placed over the substrate teeth. Clinical Relevance: The optimal thickness for achieving the highest translucency of the highly translucent zirconia laminate veneers was 0.50 mm for the veneers with A1 and A2 shades placed over the substrate teeth. Clinicians and dental technicians could consider this when selecting materials for aesthetic restorations.
RESUMEN
This in vitro study aimed to evaluate the final shade of translucent zirconia laminate veneers with varying thicknesses over teeth with different shades. Seventy-five chairside computer-aided design/computer-aided manufacturing (CAD/CAM) shade A1 third-generation zirconia dental veneers, with thicknesses of 0.50 mm, 0.75 mm, and 1.00 mm, were placed on resin composite teeth with shades ranging from A1 to A4. The laminate veneers were divided into groups based on thickness and background shade. All restorations were evaluated with a color imaging spectrophotometer, to map the veneer surface from A1 to D4. Regardless of the thickness or background shade, all dental veneers showed color alteration from the original shade. Veneers with 0.5 mm thickness tended to display the B1 shade, while veneers with 0.75 mm and 1.0 mm thickness primarily exhibited the B2 shade. The thickness of the laminate veneer and background shade significantly modified the original shade of the zirconia veneer. One-way analysis of variance was performed and a Kruskal-Wallis test was used to determine the significance between the three veneer thicknesses groups. The results indicated that the thinner restorations showed higher values with the color imaging spectrophotometer, suggesting that thinner veneers may result in more consistent color matching. This study underscores the importance of carefully considering thickness and background shade when selecting zirconia laminate veneers, to ensure optimal color matching and overall aesthetic outcomes.