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Background: Comparative studies of interim veneer restorations crafted using subtractive computer-aided manufacturing (s-CAM) milling technology and traditional direct hand-made approaches are needed. Purpose: This comparative in vitro study evaluated the fracture resistance of two types of provisional veneer restorations for maxillary central incisors: milled (s-CAM) and traditional direct hand-made bis-acryl veneers. Materials and methods: Fifty maxillary right central incisor veneers (25 specimens per group) were fabricated and divided according to the fabrication method: (1) s-CAM milled (Structure CAD, VOCO Dental); and (2) hand-made (Protemp Plus, 3M). The restorations were cemented onto 3D-printed resin dies using temporary cement and subjected to 1000 cycles of thermal cycling between 5° and 55 °C. These restorations subsequently were subjected to compressive loading until fracture occurred. Images of the fractured samples were captured using a scanning electron microscope (SEM). Statistical analysis was performed using the one-way ANOVA test and the Mann-Whitney U test. Results: Significant differences (p < 0.001) in the fracture resistance were observed between the two groups. s-CAM milled interim veneers displayed higher fracture resistance values (439.60 ± 26 N) compared to the traditional method (149.15 ± 10 N). Conclusion: The manufacturing method significantly influences the fracture resistance of interim veneer restorations. s-CAM interim laminate veneer restorations for maxillary central incisors exhibit a fracture resistance superior to that of the traditional method using bis-acryl.Clinical relevanceClinicians should consider CAD/CAM milled veneers for scenarios demanding long-term interim restoration and the withstanding of high occlusal forces.
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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.
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AIM: This in vitro study aimed to compare the light-transmission properties of two chairside CAD/CAM lithium disilicate (LD) ceramics (a novel fully crystallized and a traditional pre-crystallized) across varying thicknesses. MATERIALS AND METHODS: One hundred flat specimens were obtained from precrystallized (e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein) and fully crystallized (LiSi GC Block; GC, Tokyo, Japan) LD at five different thicknesses (0.5, 0.75, 1.0, 1.50 and 2.0 mm). All specimens were polished with a polishing system for lithium disilicate restorations following recommendations from the manufacturer. Light transmission was evaluated with a radiometer. The statistical analysis between e.max CAD and LiSi GC Block was performed using a Mann-Whitney test for each thickness at a significance level of 0.05 (p < 0.05), followed by a Kruskal-Wallis test to compare the light transmission between the thicknesses of e.max CAD and LiSi GC Block. RESULTS: Light transmittance was significantly affected by ceramic thickness. The 0.5 mm thick specimens exhibited the highest transmittance values compared to all other groups, while a light transmittance of 0.00 was observed in the 2.0 mm thick specimens for both e.max CAD and LiSi GC Block. In the comparison between e.max CAD and LiSi GC Block according to thickness, there was a statistically significant difference exclusively between groups with a thickness of 1.50 mm (p = 0.002). CONCLUSIONS: Light transmission for pre- and fully crystallized CAD/CAM lithium disilicate ceramics only showed a statistical difference at the thickness of 1.50 mm (p = 0.002). E.max CAD demonstrated acceptable light transmission up to a thickness of 1.5 mm. CLINICAL SIGNIFICANCE: A thickness of 2 mm for chairside CAD/CAM lithium disilicate ceramics, whether pre-crystallized or fully crystallized, necessitates the use of dual-cure resin luting cement due to reduced light transmission.
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PURPOSE: To evaluate the fracture load of chairside computer-aided design and computer-aided manufacturing (CAD-CAM) veneers fabricated with two conventional pre-crystallized and two fully crystallized lithium disilicate ceramic materials. MATERIALS AND METHODS: Seventy-five chairside CAD-CAM veneers (15 specimens/group) for maxillary right central incisors were fabricated with different lithium disilicate brands: (1) IPS e.max CAD; (2) Amber Mill; (3) Cerec Tessera; (4) n!ce Straumann; and (5) GC Initial LiSi Block. Restorations were cemented with resin luting cement (Variolink Esthetic, Ivoclar) to 3D-printed resin dies. Bonded restorations received 5000 thermal cycles and then were loaded until fracture. Statistical analysis included One-Way ANOVA. RESULTS: Conventional pre-crystallized e.max CAD displayed the highest fracture load value (640 N), followed by fully-crystallized n!ce Straumann (547 N), pre-crystallized Cerec Tessera (503 N), pre-crystallized Amber Mill (476 N), respectively; fully-crystallized GC Initial LiSi Block (431 N) displayed the lowest values. When comparing the fracture load of recent lithium disilicate ceramic material to the e.max group, which acted as the control, significant differences were noted. The LiSi Block GC group, in particular, had considerably higher mean difference values (208.867, p < 0.001, 95% CI [89.63, 328.10]), as did the Amber Mill group (164.200, p = 0.002, 95% CI [44.96, 283.44]) and CEREC Tessera group (137.533, p = 0.016, 95% CI [18.30, 256.77]). The e.max and n!ce Straumann groups had no statistically significant differences in mean scores (92.933, p = 0.198, 95% CI [-26.30, 212.17]). These findings imply that the clinical performance of recent lithium disilicate veneers varies when compared to the e.max CAD group. CONCLUSIONS: The fracture load of chairside CAD-CAM lithium disilicate veneers for maxillary central incisors varies according to the type of ceramic brands. Conventional pre-crystallized e.max CAD displayed higher fracture load than the recent pre- and fully-crystallized lithium disilicate materials, emphasizing the significance of choosing the right product based on the desired clinical outcome.
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BACKGROUND: We compared the repeatability of the shade determination of resin composite restorations and acrylic teeth in light and darker shades at baseline and after an aging process through two digital tooth color-matching methods: using a Trios 3Shape intraoral scanner and using a Vita Easyshade Compact spectrophotometer. MATERIAL AND METHODS: Forty upper central incisor acrylic teeth in the shade A1 (n = 10) and A3 (n = 10) were randomly assigned to be restored with Filtek Bulk Fill in the shade A1 (n = 10) or A3 (n = 10). Subsequently, 20 Class V cavities were prepared in a standardized manner (mesio-distal = 3.0 mm, cervical-occlusal = 2.0 mm, depth = 1.5 mm). Cavities were restored using an universal adhesive system and resin composite in two increments and were light-cured. The shade difference between the resin composite Class V restorations in acrylic teeth of the A1 and A3 shades was evaluated at baseline and after aging. Aging was simulated using ultraviolet light for 120 h. An Easyshade device and an intraoral scanner were used under D65 illumination. Measurements were taken five times, on top of the restoration and on the acrylic teeth, in a randomized manner. RESULTS: Data analysis was on the calculation of the arithmetic mean for the percentage of repeatability conducted by the Trios scanner and the Easyshade device. There was no statistically significant comparison between the shade measurement devices (p > 0.05). At baseline, the repeatability for both the Trios intraoral scanner and the Vita Easyshade Compact device for artificial teeth in the shades A1 and A3 was 100%. After aging, the trueness recorded by the intraoral scanner and the Easyshade device for artificial teeth in the shade A1 was 80%. For Class V restoration with shade A1, the intraoral scanner recorded 80% trueness and the Easyshade device recorded 60% trueness at baseline. For shade A3, the intraoral scanner recorded 60% trueness and the Easyshade device recorded 60% trueness. CONCLUSIONS: The intraoral scanner and Easyshade device are reliable for baseline shade selection, but their accuracy decreases after aging, particularly for darker shades.