Effect of a new support design on the marginal and internal gap of additively manufactured interim crowns using direct light deposition technology.

PURPOSE: To investigate the design and location of supporting structures on the marginal and internal gap of interim restorations. MATERIALS AND METHODS: A mandibular right first molar resin tooth was prepared for a full coverage crown and scanned using a laboratory scanner (3Shape D900). The scanned data were converted into standard tessellation language (STL) format and an indirect prosthesis was designed using computer-aided design (CAD) software (exocad DentalCAD). The STL file was used to fabricate a total of 60 crowns with a 3D printer (EnvisionTEC Vida HD). The crowns were printed using E-Dent C&B MH resin and divided into 4 groups based on four different support structure designs, including supports on the occlusal (0° group), buccal and occlusal (45° group), buccal (90° group), and a new design consisting of horizontal bars placed on all surfaces and line angles (Bar) (n = 15). The silicone replica technique was used to determine the gap discrepancy. Fifty measurements were obtained for each specimen to examine the marginal and internal gaps by using a digital microscope (Olympus SZX16) at ×70 magnification. Additionally, the marginal discrepancy at different locations of the tested crowns, including buccal (B), lingual (L), mesial (M), and distal (D), as well as the maximum and minimum marginal gap intervals among groups, were analyzed. The collected data were analyzed using factorial ANOVA, followed by the Tukey HSD test for multiple comparisons (a = 0.05). RESULTS: There was a significant difference in marginal and internal gaps among the groups (p < 0.001). The buccal placement supports (90° group) had the least marginal and internal discrepancies (p < 0.001). The new design group showed the highest marginal and internal gap. The marginal discrepancy in different locations of the tested crowns (B, L, M, D) was found to be significantly different among the groups (p < 0.001). The mesial margin of the Bar group had the largest marginal gap, whereas the buccal margin of the 90° group had the lowest marginal gap. The new design had a significantly smaller difference between the maximum and minimum marginal gap intervals than other groups (p < 0.001). CONCLUSION: The location and design of the supporting structures affected the marginal and internal gaps of an interim crown. The buccal placement of supporting bars (90° printing orientation) showed the smallest mean internal and marginal discrepancies.

Exploring the impact of the extent of the partially edentulous area on the accuracy of two intraoral scanners.

STATEMENT OF PROBLEM: The accuracy of intraoral scans, particularly in edentulous areas, remains a concern despite the increasing use of digital technology, especially intraoral scanners. PURPOSE: The purpose of this in vitro study was to assess the impact of the extent of an edentulous area on the accuracy (trueness and precision) of intraoral scans from 2 intraoral scanners. MATERIAL AND METHODS: A KaVo dentoform with epoxy resin teeth was used to generate 9 groups with different numbers of teeth removed. A laboratory scanner served as the reference dataset, and 2 intraoral scanners (TRIOS 3 and Primescan AC) were evaluated. A single operator performed all scans following standardized protocols and calibration. Trueness and precision were assessed by using root mean square (RMS) values. Analysis of variance was used to compare trueness and precision values obtained from the 2 scanners and different partially edentulous conditions (α=.05). RESULTS: A significant difference was found in the trueness of intraoral scans of the 2 scanners and under different partially edentulous extensions. Primescan AC exhibited significantly lower trueness than TRIOS 3 (P<.001). For the individual edentulous conditions, Primescan had a significantly higher RMS mean than TRIOS 3 for G0, G3, G4, G6, G7, and G8 (P<.001) and a significantly lower RMS mean than TRIOS 3 for G1 and G4 (P<.001), while no significant difference in RMS mean was found between the 2 scanners for G2 (P=.999). For precision, no significant difference was found between the 2 scanners or different edentulous conditions [(F 8, 90)=1.82, P=.085]. CONCLUSIONS: The accuracy of intraoral scans was influenced by the length of edentulous areas and the scanner used. Primescan AC demonstrated lower trueness than TRIOS 3 for most partially edentulous conditions, while the scanners were similar in precision. These findings highlight the need for careful scanner selection in specific clinical situations, as scanning accuracy may vary depending on the scanner and edentulous condition.

Marginal and internal discrepancies associated with carbon digital light synthesis additively manufactured interim crowns.

STATEMENT OF PROBLEM: The carbon digital light synthesis (DLS) or continuous liquid interface production (CLIP) technology is an innovative additive manufacturing technology using oxygen-inhibited photopolymerization to create a continuous liquid interface of unpolymerized resin between the growing component and the exposure window. This interface eliminates the need for an incremental layer-by-layer approach, allowing for continuous creation and increased printing speed. However, the internal and marginal discrepancies associated with this new technology remain unclear. PURPOSE: The purpose of this in vitro study was to evaluate the marginal and internal discrepancies by using the silicone replica technique of interim crowns fabricated by 3 different manufacturing technologies: direct light processing (DLP), DLS, and milling. MATERIAL AND METHODS: A mandibular first molar was prepared, and a crown was designed with a computer-aided design (CAD) software program. The standard tessellation language (STL) file was used to create 30 crowns from the DLP, DLS, milling technologies (n=10). The gap discrepancy was determined using the silicone replica approach, with 50 measurements made with a ×70 microscope for each specimen for the marginal and internal gaps. The data were analyzed using 1-way ANOVA, followed by the Tukey HSD post hoc test (α=.05). RESULTS: The DLS group had the least marginal discrepancy compared with the DLP and milling groups (P<.001). The DLP group showed the highest internal discrepancy followed by the DLS and milling groups (P=.038). No significant difference was found between DLS and milling in terms of internal discrepancy (P>.05). CONCLUSIONS: The manufacturing technique had a significant effect on both internal and marginal discrepancies. The DLS technology showed the smallest marginal discrepancies.

Shear bond strength of porcelain to milled and stereolithography additively manufactured zirconia with and without surface treatment: An in vitro study.

STATEMENT OF PROBLEM: Delamination of veneering ceramic is one of the most common challenges relating to veneered zirconia restorations. Additive manufacturing (AM) is a fast-expanding technology that has gained widespread acceptance in dentistry and is increasingly being used to produce dental restorations. However, information about bonding of porcelain to AM zirconia is lacking. PURPOSE: The purpose of this in vitro study was to investigate the shear bond strength (SBS) of porcelain to milled and additively manufactured zirconia, and the effect of surface treatment on bond strength. MATERIAL AND METHODS: A Ø12×5-mm disk was designed virtually to fabricate all specimens, which were divided into 2 groups according to the manufacturing technique: additively manufactured or milled zirconia. The effect of airborne-particle abrasion and a zirconia liner before porcelain application was investigated in both groups. Veneering porcelain was fired into an alumina ring mold on the zirconia surface. SBS was measured by using a universal testing machine at a crosshead speed of 1 mm/min before and after aging (n=10). SBS data were analyzed with 3-way ANOVA (α=.05) RESULTS: A significant difference was found between milled and AM zirconia. The SBS of porcelain to milled zirconia was significantly higher (1.38 MPa) than to AM zirconia (0.68 MPa) (P<.001). The surface treatment of zirconia had no significant effect on porcelain SBS in either group (P=.254), whereas thermocycling significantly reduced the SBS of porcelain to zirconia in both milled and AM groups (P=.001). CONCLUSIONS: Porcelain bonding to milled zirconia was better than to AM zirconia. Pretreating the zirconia substrate before porcelain application did not improve the porcelain bond.

Computer-aided design and additively manufactured resin-bonded framework to retain an existing ceramic crown as the interim restoration after extraction: A dental technique.

A novel way to use the patient's existing ceramic crown from a nonrestorable maxillary anterior tooth as part of the interim restoration after extraction is described. The crown was fixed intraorally with a digitally designed and 3D-printed resin-bonded fixed dental prosthesis framework in its pre-extraction position. The procedure maintained esthetics, optimized soft-tissue management, and provided a fixed prosthesis before implant placement in the esthetic zone.

Surface Roughness and Bond Strength of Resin Composite to Additively Manufactured Zirconia with Different Porosities.

PURPOSE: To investigate the bond strength of resin cement to additively manufactured (AM) zirconia with different porosities when compared to milled zirconia. MATERIALS AND METHODS: A 12 × 5 mm disk virtual design file was used to fabricate a total of 48 disks divided into 4 groups: 3 groups were AM with different porosities including 0%-porosity (AMZ0 group), 20%-porosity (AMZ20 group), and 40%-porosity (AMZ40 group), and 1 milled zirconia (control or CNCZ group). The dimensions of all specimens were measured using a digital caliper. A 3D- confocal laser scanner was used to analyze surface morphology and measure the surface roughness (Sa), followed by SEM analysis. Tensile bond strength of composite resin cement to specimens was measured before and after aging procedures using a universal testing machine (n = 10). Failure modes were evaluated under a light microscope. Volumetric change data was analyzed using one-way ANOVA, and two-way ANOVA was used to compare bond strength values (α = 0.05). RESULTS: There was a significant difference in volumetric changes among the groups. The CNCZ group showed the least changes in diameter 0.027 ± 0.029 mm and thickness 0.030 ± 0.012 mm and AM zirconia with 40% porosity showed the most volumetric changes in diameter 5.237 ± 0.023 mm. ANOVA test indicated an overall significant difference in surface roughness across all groups (F = 242.6, p < 0.001). The CNCZ group showed the highest mean Sa of 1.649 ± 0.240 µm, followed by AMZ40 group with Sa of 0.830 ± 0.063 µm, AMZ20 group with Sa of 0.780 ± 0.070 µm, and the AMZ0 group with Sa of 0.612 ± 0.063 µm. Two-way ANOVA showed significant difference in bond strength between the CNCZ group 12.109 ± 3.223 MPa and the AMZ0 group 8.629 ± 0.914 MPa, with significant pretest failures in specimens with porosities. Thermal cycling methods reduced the bond strength non-significantly in CNCZ group with no effect in the AMZ0 group. CONCLUSION: Milled zirconia had a higher surface roughness and bond strength to composite resin cement than AM zirconia, and porosities in AM zirconia decreased the bond strength with significant pretest failures.

Effect of Air-Particle Abrasion Protocol and Primer on The Topography and Bond Strength of a High-Translucent Zirconia Ceramic.

PURPOSE: To evaluate effect of air-particle abrasion protocol and primer on surface topography and bond strength of resin cement to high-translucent zirconia ceramics. MATERIALS AND METHODS: Two hundred disk-shaped high-translucent zirconia specimens of 5Y-PSZ were prepared. The specimens were assigned to 5 groups in terms of particle type and air-particle abrasion pressure: (1) control, (2) alumina with 0.2 MPa-air pressure [AB-0.2], (3) alumina with 0.4 MPa-air pressure [AB-0.4], (4) glass beads with 0.2 MPa-air pressure [GB-0.2], and (5) glass beads with 0.4 MPa-air pressure [GB-0.4]. Two different primers 1% MDP (Experimental) and MDP-silane primer (Clearfil Ceramic Primer Plus) was also tested. Stainless steel rods were bonded to the 5Y-PSZ specimens with PANAVIA V5. For each group, the tensile bond strength (TBS) was measured after 24-hour water storage (n = 10) and after 5000 thermal-cycling (n = 10) at crosshead speed of 2 mm/min. The data were statistically analyzed using Weibull analysis. Surface roughness (Sa) was measured using a 3D-Laser Scanning Confocal Microscope (n = 5) and analyzed by t-test with Bonferroni correction. Surface topography using scanning electron microscopy (SEM) and surface elemental analysis using energy dispersion spectroscopy (EDX), and cross-section SEM at the interface with composite cement were also investigated. RESULTS: In MDP-silane groups, the highest TBS was observed in AB-0.4 after 24 hours and GB-0.4 after thermal-cycling (p < 0.05). In MDP groups, AB groups resulted in the significantly higher TBS than GB groups (p < 0.05). AB-0.4 group showed the highest Sa value compared to all groups (p < 0.005), meanwhile GB groups did not show different Sa compared to control (p > 0.005). CONCLUSION: Air-abrasion with different particle and blasting pressure can improve bonding to zirconia with proper primer selection. Particularly, glass beads abrasion followed by MDP-silane primer and alumina abrasion followed by MDP primer alone provided stable bond strength of resin cement to high-translucent zirconia after aging. High-translucent zirconia abraded with glass beads achieves a desirable bonding performance without creating surface microcracks which may hinder zirconia's mechanical properties.

The effects of different silicatization and silanization protocols on the bond durability of resin cements to new high-translucent zirconia.

OBJECTIVE: The aim of this study was to assess the influence of different silicatization protocols with various silane treatment methods on the bond performance to high-translucent zirconia. MATERIALS AND METHODS: High-translucent zirconia specimens were assigned to five groups according to mechanical surface pretreatment: as-sintered (Con), 0.2 MPa alumina sandblasting (AB2), tribochemical silica coating (TSC), 0.2 and 0.4 MPa glass bead air abrasion (GB2) and (GB4). Each group was subjected to 4 different cementation protocols: Panavia SA Universal (SAU), Panavia SA plus (SAP), silane + SAP (S-SAP), and Universal adhesive + SAP (U-SAP). Tensile bond strength (TBS) was measured after 24 h and 10,000 thermocycling (TC). Surface topography, surface energy, and elemental composition of the abraded zirconia surface analyses were completed. TBS data was analyzed using the Weibull analysis method. Surface roughness and surface energy were compared by one-way ANOVA analysis of variance (α = 0.05). RESULTS: After 24 h, higher TBS was achieved with all cementation protocols in AB2 and TSC, also, in GB2 with all protocols except U-SAP, and in GB4 with SAU and S-SAP. After aging, GB4/S-SAP, GB2/S-SAP, AB2/U-SAP, and TSC/S-SAP showed the highest bond strength. GB groups showed the lowest surface roughness and highest surface energy. CONCLUSION: Glass bead abrasion achieved the durable bond strength to high-translucent zirconia using a separate silane coupling agent while altered surface chemistry, surface energy, and roughness without effect on morphology. CLINICAL RELEVANCE: Glass bead air abrasion is an alternative to alumina sandblasting and tribochemical silica coating and improves bond strength to high translucent zirconia.

Additive Manufacturing of Zirconia Ceramic and Its Application in Clinical Dentistry: A Review.

Additive manufacturing (AM) has many advantages and became a valid manufacturing technique for polymers and metals in dentistry. However, its application for dental ceramics is still in process. Among dental ceramics, zirconia is becoming popular and widely used in dentistry mainly due to its outstanding properties. Although subtractive technology or milling is the state of art for manufacturing zirconia restorations but still has shortcomings. Utilizing AM in fabricating ceramics restorations is a new topic for many researchers and companies across the globe and a good understanding of AM of zirconia is essential for dental professional. Therefore, the aim of this narrative review is to illustrate different AM technologies available for processing zirconia and discus their advantages and future potential. A comprehensive literature review was completed to summarize different AM technologies that are available to fabricate zirconia and their clinical application is reported. The results show a promising outcome for utilizing AM of zirconia in restorative, implant and regenerative dentistry. However further improvements and validation is necessary to approve its clinical application.

The effect of carboxyl-based monomers on resin bonding to highly translucent zirconia ceramics.

The purpose of this study was to evaluate the bonding performance of carboxyl-based monomers in the priming agents to highly translucent zirconia. Highly translucent zirconia disk-shaped specimens of yttria-partially stabilized zirconia (Y-PSZ) (Katana HT zirconia) after sandblasting, were assigned to 5 groups according to the chemical pretreatment: no-treatment (Con), PZ Primer (PZP), PZ primer liquid A+MMA (PZA, as MDP primer), Super-Bond liquid (SBL, as 4-META primer) and experimental 5% 4-MET primer (MET). After priming, stainless steel rods were bonded to the zirconia specimens with TBB-initiated resin. The tensile bond strength test was performed after storage for 24 h, 30, and 150 days in 37°C water. The Weibull moduli decreased in all groups except PZA after 150 days. Superior bond strength observed in PZA and MET groups after aging. Application of carboxyl-based monomers were found to be effective in adhesion to highly translucent zirconia ceramics.