To compare the marginal gap and fracture resistance of implant-supported 3-dimensional (3D) printed definitive composite crowns with those fabricated by using 3 different millable materials. A prefabricated abutment was digitized by using a laboratory scanner (E4 Lab Scanner) and a complete-coverage maxillary first premolar crown was designed (Dental Designer). Forty crowns were fabricated either by 3D printing (Saremco Print Crowntec, SP) or milling (Brilliant Crios, BC; Vita Enamic, VE; Cerasmart 270, CS) (n = 10). Baseline marginal gap values were evaluated by measuring 60 predetermined points on an abutment (15 points for each side) with a stereomicroscope at ×40 magnification. Marginal gap values were reevaluated after adhesive cementation. Load-to-fracture test was performed by using a universal testing machine. Two-way analysis of variance (ANOVA) was used to evaluate the effect of material type and cementation on marginal gap values. While Tukey HSD tests were used to compare the materials' marginal gap values before and after cementation, the effect of cementation on marginal gap values within each material was analyzed by using paired samples t-tests. Fracture resistance data were analyzed by using 1-way ANOVA (α=0.05). Material type and cementation significantly affected marginal gap values (P < .001). Regardless of cementation, SP had the lowest marginal gap values (P < .001), while the differences among milled crowns were nonsignificant (P ≥ .14). Cementation significantly increased the marginal gap values (P < .001). Material type did not affect fracture resistance values (F = 1.589, P = .209). Implant-supported 3D-printed composite crowns showed higher marginal adaptation compared with the milled crowns before and after cementation. In addition, all crowns endured similar forces before fracture.

The information in the literature on the effect of printing layer thickness on interim 3D-printed crowns is limited. In the present study, the effect of layer thickness on the trueness and margin quality of 3D-printed composite resin crowns was investigated and compared with milled crowns. The crowns were printed in 3 different layer thicknesses (20, 50, and 100 μm) by using a hybrid resin based on acrylic esters with inorganic microfillers or milled from polymethylmethacrylate (PMMA) discs and digitized with an intraoral scanner (test scans). The compare tool of the 3D analysis software was used to superimpose the test scans and the computer-aided design file by using the manual alignment tool and to virtually separate the surfaces. Deviations at different surfaces on crowns were calculated by using root mean square (RMS). Margin quality of crowns was examined under a stereomicroscope and graded. The data were evaluated with one-way ANOVA and Tukey HSD tests. The layer thickness affected the trueness and margin quality of 3D-printed interim crowns. Milled crowns had higher trueness on intaglio and intaglio occlusal surfaces than 100 μm-layer thickness crowns. Milled crowns had the highest margin quality, while 20 μm and 100 μm layer thickness printed crowns had the lowest. The quality varied depending on the location of the margin.

Purpose: To evaluate the influence of implant scan body (ISB) design (height, diameter, geometry, material, and retention system) on the accuracy of digital implant scans.Material and Methods: A literature search was completed in five databases: PubMed/Medline, Scopus, Embase, World of Science, and Cochrane. A manual search was also conducted. Studies reporting the evaluation of ISB design on the accuracy of digital scans obtained by using IOSs were included. Two investigators evaluated the studies independently by applying the Joanna Briggs Institute critical appraisal. A third examiner was consulted to resolve any lack of consensus. Articles were classified based on the ISB features of height, geometry, material, and retention system.Results: Twenty articles were included. Among the reviewed studies, 11 investigations analyzed the influence of different ISB geometries, 1 study assessed the impact of ISB diameter, 4 studies investigated the effect of ISB splinting, 2 articles evaluated ISB height, and 2 studies focused on the effect of ISB material on scan accuracy. In addition, 8 studies involved ISBs fabricated with different materials (1‐ and 2‐piece polyetheretherketone and 1‐piece titanium ISBs), and all of the reviewed articles tested screw‐retained ISBs, except for 3 in vitro studies.Conclusions: The findings did not enable concrete conclusions regarding the optimal ISB design, whether there is a relationship between IOS technology and a specific ISB design, or the clinical condition that maximizes intraoral scanning accuracy. Research efforts are needed to identify the optimal ISB design and its possible relationship with the IOS selected for acquiring intraoral digital implant scans.

Objective: To compare the color stability, translucency, and biaxial flexural strength (BFS) of differently glazed advanced lithium disilicate (ALDS) with those of lithium disilicate (LDS) and zirconia‐reinforced lithium silicate (ZLS) after coffee thermocycling.Materials and methods: Forty disk‐shaped specimens were prepared from three lithium silicate based materials (CEREC Tessera, ALDS; IPS e.max CAD, LDS; Vita Suprinity, ZLS). ALDS specimens were divided into two subgroups according to glazing procedures (reduced glaze duration, ALDS‐S and normal glaze duration, ALDS‐N), while LDS and ZLS specimens were crystallized and glazed. Color coordinate measurements were performed before and after coffee thermocycling. Color differences (ΔE₀₀) and relative translucency parameters (RTP) were calculated. Specimens were then subjected to BFS test. Statistical analysis was performed by using 1‐ (ΔE₀₀ and BFS) and 2‐way (RTP) ANOVA tests (α = 0.05).Results: ΔE₀₀ values of tested materials were similar (df = 3, F = 0.150, p = 0.929). Two‐way ANOVA showed the significant effect of material type, coffee thermocycling, and the interaction between these parameters on RTP values (p < 0.001). Both before and after thermocycling, LDS had the highest (p ≤ 0.001) and ZLS had the lowest (p < 0.001) RTP values, while ALDS‐N had higher RTP than ALDS‐S (p ≤ 0.001). Among tested materials, only LDS had similar RTP values before and after thermocycling (p = 0.865) as the other materials had lower RTP values after thermocycling (p < 0.001). ALDS‐N had higher BFS values than ALDS‐S (p = 0.005), while LDS had similar values to ALDS specimens (p ≥ 0.201). ZLS had the highest BFS (p ≤ 0.007).Conclusions: ALDS had comparable values to those of other materials. However, reduced glazing duration resulted in decreased translucency and BFS of ALDS.Clinical significance: ALDS may be an appropriate restorative material for those patients with increased coffee consumption considering its color stability and ability to maintain translucency, particularly when glazed by using a conventional porcelain furnace.

Purpose: To evaluate how different polishing techniques and coffee thermal cycling affect the surface roughness and stainability of additively and subtractively manufactured resins used for definitive prostheses.Materials and Methods: Two additively manufactured composite resins (Crowntec, CT and VarseoSmile Crown Plus, VS) and a subtractively manufactured resin nanoceramic (Cerasmart, CS) were used to fabricate 90 rectangular‐shaped specimens (14 × 12 × 1 mm) (n = 30). After baseline surface roughness (R_a) measurements, specimens were divided into three groups based on the polishing technique; conventional polishing with a 2‐stage polishing kit (CP) and surface sealant application (Optiglaze, OG or Vita Akzent LC, VA) (n = 10). After polishing, specimens were subjected to 10,000 cycles of coffee thermal cycling. R_a and color coordinate measurements were performed after polishing and after coffee thermal cycling. Color difference (ΔE₀₀) was calculated. Scanning electron microscope images were taken at each time interval. Kruskal–Wallis or 1‐way analysis of variance (ANOVA) were used to evaluate R_a of materials within each polishing‐time interval pair and different polishing techniques within each material‐time interval pair, while Friedman or repeated measures ANOVA were used to evaluate R_a at different time intervals within each material‐polishing pair. ΔE₀₀ was assessed with 2‐way ANOVA (α = 0.05).Results: Other than VA‐after polishing (p = 0.055), tested materials had significantly different R_a within each polishing‐time interval pair (p ≤ 0.038). When R_a differences among different polishing techniques within each material‐time interval pair were considered, CS had differences after coffee thermal cycling, CT had differences before polishing and after coffee thermal cycling, and VS had differences within each time interval (p ≤ 0.038). When R_a differences among different time intervals within each material‐polishing pair were considered, significant differences were observed among all pairs (p ≤ 0.016), except for CS‐VA (p = 0.695) and VS‐VA (p = 0.300). ΔE₀₀ values were affected by material and polishing technique interaction (p = 0.007).Conclusions: R_a of CS was similar to or lower than the R_a of other materials, regardless of the time interval or polishing technique. CP mostly led to lower R_a than other polishing techniques, whereas VA resulted in a high R_a regardless of the material‐time interval pair. Polishing reduced the R_a, while coffee thermal cycling was found to have a small effect. Among tested material‐polishing pairs, only CS‐VA had moderately unacceptable color change when previously reported threshold values were considered.

To evaluate a nonmetrology-grade and a metrology-grade 3D analysis software when measuring the deviations of computer-aided-design/ computer-aided-manufacturing (CAD-CAM) fabricated crowns from the virtual design file. A right first molar on a mandibular dentate model was prepared and scanned with an intraoral scanner, i500 (Medit). A complete coverage crown was designed in standard tessellation language (STL) format and 20 resin crowns were fabricated with CAD-CAM. The crowns were then digitized using the same intraoral scanner (test-scans). Root mean square (RMS) method was used to evaluate the deviations between the test-scans and the design file of the crowns on 3 surfaces (overall, external, and internal) using a metrology-grade, Geomagic Control X (3D Systems) and a nonmetrology-grade, Medit Link (Medit) software. The data were analyzed with Welch two-sample t-tests to compare two software for the non-inferiority of the nonmetrology-grade software with a 50 µm threshold and the potential superiority of the metrology-grade software (α = 0.05). The Welch two-sample t-tests for the non-inferiority analysis showed that the differences between the nonmetrology-grade and the metrology-grade software were below the threshold of 50 µm for each surface tested (p <0.001). The differences between the two-tested software were nonsignificant for each surface analyzed when superiority was considered (p ≥.194). The nonmetrology-grade software performed similar to the metrology-grade software when analyzing the deviations of CAD-CAM crowns. Therefore, the nonmetrology-grade 3D analysis software may be considered for the deviation measurements of similar restorations. The trueness of crowns after fabrication may affect their fit, and 3D analysis of trueness prior to the delivery appointment with the tested nonmetrology-grade software after fabrication may facilitate potential clinical adjustments and delivery of the crowns.