The International Journal of Prosthodontics, 03/2025

Purpose: To evaluate the 12- and 24-month clinical results of overlay and one-piece endodontic crown restorations applied with additively manufactured, 3D-printed, permanent ceramic-filled resin (PCR) according to the modified US Public Health Service (USPHS) criteria. Materials and Methods: A total of 33 indirect restorations (16 overlay, 17 endocrown; 4 premolar, 29 molar) produced using PCR (Formlabs) were applied in 30 patients by a single dentist. The restorations were evaluated according to the modified USPHS criteria at baseline (1 week), 12 months, and 24 months by two independent evaluators. For comparisons of the dependent criteria scores, related samples Cochran Q test was used, and in post-hoc paired comparisons, Bonferroni test was used. Fisher-Freeman-Halton test was applied in the comparisons of categoric variables according to the restoration type groups (α = .05). Results: No statistically significant difference was determined between the evaluation criteria scores at baseline, 12 months, and 24 months for marginal adaptation (P = .05), retention (P = 1), interproximal contact (P = .368), color match (P = 1), surface texture (P = 1), and patient satisfaction (P = 1). The only score criterion that showed a statistically significant difference between baseline and 24 months (P = .001) was marginal discoloration. This criterion’s score change was from 100% A score to 69.7% A score. Conclusions: In the 2-year follow-up of indirect single-tooth restorations produced with 3D-printed PCR, all restorations showed acceptable clinical performance (≥ 99.5% A + B score at 2 years).

Purpose: To produce CAD/CAM reference samples for shade communication milled from the restoration materials zirconia (ZrO₂) and zirconia-reinforced lithium silicate (ZLS) and evaluate the color difference with the corresponding conventional VITA Classical (VC) shade tab. Furthermore, to verify the color consistency of the materials. Materials and Methods: In total, 55 samples were milled out of ZrO₂ and ZLS in five different colors, and their color parameters were compared to the corresponding VC tabs both visually and digitally. For digital evaluation, images were taken of the samples and VC tabs and analyzed in Adobe Photoshop to extract L*a*b* values. Color difference (ΔE₀₀) was calculated using the CIEDE 2000 formula. Multilevel mixed-effects linear regression model was used to derive estimates of the mean ∆E₀₀. Results: Color difference was significantly higher than 1.8 in the case of all the ZrO2 samples and for the ZLS A3, B2, and C2 samples. Color difference was also found during the visual comparison. Comparing the same color samples, the ΔE₀₀ exceeded 0.8 in some cases but stayed under 1.8 in every case and showed no color difference visually. Conclusions: When comparing CAD/CAM samples and VC shade tabs, visible and measurable color differences (ΔE₀₀ > AT50:50%) were found in the case of all ZrO₂ samples and in three out of five evaluated shades of ZLS samples. The color consistency of the blocks was acceptable. Better shade communication and more reliable shade reproduction is achieved when reference photos are sent with a color sample made from the restoration material.

Purpose: To evaluate the preferences of dental practitioners regarding ceramic materials for tooth-supported crowns using an online survey and to assess the influence of age, gender, years of experience, and dental specialty on those preferences. Materials and Methods: An anonymous questionnaire targeting 796 dentists was delivered online through Google Surveys. It contained 17 dichotomous, closed questions with two sections. The first section dealt with general characteristics, including age, gender, years of experience, training in prosthodontics, and hours worked per week. The second section included questions regarding preferences of different materials for crowns and the use of digital workflows. Analyses were carried out with Stata 14 software (Stata). A significance level of P = .05 was adopted. Results: A total of 248 surveys were answered. Practitioners in Chile preferred lithium disilicate for the anterior region (55.2%) and also for the posterior area (40.7%), regardless of their age, gender, years since graduation, hours worked per week, or any training in prosthodontics. Chilean dentists over 50 years old considered zirconia almost four times more frequently than those under 30 years old for anterior crowns (51.85%). Overall, 59.68% of the dentists take digital impressions, and 37.10% have access to chairside CAD/CAM technology. In this group, 54.4% preferred feldspathic ceramics for anterior crowns and 23.9% for posterior crowns. Conclusions: While there is a wide range of dental ceramic materials, these results provide a snapshot of the current trends in Chile where lithium disilicate is the most preferred ceramic material for tooth supported crowns and metal-ceramics is the least preferred material.

Purpose: To compare the influence of 0-, 45-, and 90-degree build directions on the fracture load and surface roughness of additively manufactured three-unit fixed provisional restorations and to compare the additively manufactured provisionals to provisionals fabricated using conventional methods. Materials and Methods: Mandibular typodont right second molars and premolars were prepared for a missing mandibular first molar to receive a three-unit fixed partial denture. For six groups of 10 samples each, three-unit provisionals were fabricated using additive manufacturing at 0, 45, and 90 degrees; heat polymerized PMMA; autopolymerizing resin; and bis-acryl composites resins—and tested for fracture load and surface roughness. One-way ANOVA and Tukey tests were used to analyze the data. Results: For fracture load, the lowest mean value was for autopolymerizing bis-acryl resin (464.9 N), and the highest value was for additive manufacturing at 0 degrees (596 N). Surface roughness values were lowest for heat-polymerized PMMA (0.132 µm), and the highest value was for autopolymerizing PMMA (0.836 µm). Significant differences were found between the three build directions for fracture load and surface roughness (P = .001); in all pairwise comparisons except between 0 and 90 degrees (P = .502) for fracture load; and between all three build directions for surface roughness (P = .01). Compared to other provisional materials, a significant difference (P = .001) was observed between all groups. Conclusions: Build direction affected the mechanical properties of additively manufactured three-unit provisionals, with provisionals printed at 0 degrees showing the highest fracture load and lowest surface roughness. Compared to other provisional materials, additively manufactured three-unit provisionals printed at 0 degrees also showed the highest fracture load, with surface roughness similar to heat-polymerized provisionals.

Purpose: To compare the fracture load of two framework materials—zirconia and a new fiber reinforced composite (FRC Trilor)—for full-arch, implant-supported rehabilitations using various cross-sections. Materials and Methods: A cobalt-chromium metal model simulating the All-on 4 concept and including two anterior straight and two posterior 45-degree, multiunit digital implant analogs was manufactured. Four straight multiunit abutments were screwed onto the implant analogs. The metallic model was scanned, and 18 frameworks were fabricated, with 9 made of zirconia and 9 made of FRC Trilor. The frameworks were then divided into six groups (n = 3). Group division was based on the material type (zirconia or FRC Trilor) and framework cross-section: 3.5 × 6 mm², 5.5 × 6 mm², or 7.5 × 6 mm². All specimens underwent thermocycling in two baths, were cemented to the abutments of the metal model, and were subjected to a load-to-failure bending test at three different points using a universal testing machine (crosshead speed: 1 mm/minute) until complete fracture occurred. Descriptive statistics were used to present quantitative variables as means ± SDs. To compare two means, Student t test or Mann-Whitney test was used, and ANOVA test was used for three means. Results: The FRC Trilor group with a 7.5 × 6 mm² cross-section exhibited the highest load-to- failure values (ranging from 1,020 N to 2,994 N), while the zirconia group with a 3.5 × 6 mm² cross-section recorded the lowest values (ranging from 212 N to 1,287 N). The material type and framework cross-section significantly affected the mean load-to-fracture values (P < .05). Regardless of the framework cross-section, the FRC Trilor group exhibited higher fracture loads than the zirconia group. In both materials, fracture load values increased with larger framework cross-sectional areas, with the highest values observed at the interimplant midpoint. Conclusions: FRC Trilor demonstrated a fracture load that makes it a suitable alternative to zirconia for All-on-4 implant prosthetic frameworks. 

Purpose: Improvements in CAD/CAM have changed the methods of fabricating laminate veneers. The objective of this study was to evaluate the marginal and internal fit of ceramic veneers manufactured with different CAD/CAM techniques. Materials and Methods: A metal die was made by copying and scanning a prepared plastic maxillary right central incisor to design a laminate veneer. In total, 100 laminate veneers were made with four different CAD/CAM techniques (n = 25), including milled lithium disilicate (MLD), heat-pressed lithium disilicate (PLD) with 3D-printed wax patterns, milled zirconia (MZ), and 3D-printed zirconia (PZ). The virtual marginal and internal fit of fabricated veneers was evaluated with digital crown-fitting software. The actual marginal and internal fit was measured with the silicone replica method under a digital microscope. The measured data were analyzed using one-way ANOVA and Tukey tests. Results: There were significant differences in marginal and internal fit (P < .001) among manufacturing techniques. Both the virtual and actual marginal and internal gaps were higher in the PLD and PZ groups compared to the MLD and MZ groups. Conclusions: All four CAD/CAM techniques for manufacturing veneers—MLD, PLD with 3D printed wax patterns, MZ, and PZ—have clinically acceptable marginal and internal fit. MZ and MLD veneers demonstrated superior marginal and internal fit compared to PZ and PLD veneers with 3D-printed wax patterns.

Purpose: To compare the stress distribution between the all-on-4 and all-on-6 treatment concepts with various prosthetic-framework materials through finite element analysis. Materials and Methods: A 3D finite-element model of an edentulous maxilla was simulated using computerized topographic data of a patient. Four implants were placed according to the all-on-4 concept. In addition to the all-on-4 concept, two more axial implants were placed in the anterior region to create the all-on-6 concept. Four framework materials were investigated: cobalt-chromium (CoCr), zirconia (Zr), titanium (Ti), and polyetheretherketone (PEEK). Simultaneously, a 100-N load was applied to the anterior region, a 150-N oblique load was applied to the premolars, and a 200-N oblique load was applied to the molars. Principal stresses in bone and von Mises stresses in the implants and frameworks were calculated and compared. Results: The all-on-6 concept showed lower von Mises stress values on the implants and frameworks and lower principal stress values on the bone than the all-on-4 concept. PEEK exhibited the highest stress values on bone and implants, while CoCr showed the lowest stress values. Conclusions: Stress distribution was influenced by the framework materials. The use of a framework material with the appropriate physical properties for the correct indication might be particularly important in determining the success of the implant-supported prostheses.

Some of the critical clinical challenges encountered in the treatment of adult patients with deep overbite and worn dentition include correction of deep overbite, establishment of an appropriate occlusal vertical dimension (OVD), and maintenance of long-term occlusal stability. Although Angle Class II, division 2–associated deep anterior overbite is common in orthodontic treatment, simple prosthodontic treatment with great improvement of deep anterior overbite and worn dentition is infrequently reported. A 51-year-old man with Class II, division 2 malocclusion presented with a hypodivergent facial pattern, reduced lower facial height, and protuberant lips. Intraoral examination revealed unevenly worn dentition and an Angle Class II, division 2–associated deep and traumatic anterior overbite. Based on the challenges of the presentation, it was imperative to design a protocol to ensure a predictable and favorable prognosis. According to the current protocols, prosthetic treatment of occlusal rehabilitation was applied. Following the 3-month evaluation period using interim prostheses, full-mouth ceramic restorations were completed. Significant posttreatment functional and esthetic improvements were achieved with resultant stable interincisal contacts either immediately after treatment or during the 2-year follow-up period. Full-mouth rehabilitation offers brilliant prospects for improved function, enhanced esthetics, and improved health of the entire stomatognathic system of an Angle Class II, division 2 patient associated with deep overbite and worn dentition.

This study examined changes in facial geometry while playing wind instruments. Nine musicians (six men and three women, mean age 52 years) participated in part one of the study, and three musicians (three women, mean age 41 years) participated in part two. In part one, the high and low notes of each instrument were selected as test sounds. Facial geometry data were recorded using a 3D scanner. In part two, facial geometry data were recorded using a 4D scanner while a melody was played. Data were superimposed and analyzed using 3D analysis software. Numerical values and color maps of deviations were obtained. The results of part one revealed that the median 3D deviation was 1.1 mm (range 0.42 to 1.45 mm), indicating that facial geometry while playing high and low notes varied. The results of part two showed that the stable part was the frontal region and dorsal part of the nose. The approach used in this study has potential applications for evaluating facial geometry during musical instrument performances.

Purpose: To evaluate the influence of different Co-Cr framework manufacturing techniques on the bond strength between metal and two types of veneering ceramics with and without a metal primer. Materials and Methods: A total of 72 metal specimens were fabricated using the same Co-Cr alloy (Keramit NP, Nobil Metal) with three different techniques: ingots for casting (Keramit NP); disks for CAD/CAM milling (sinergia diskKeramit NP); and powder for selective laser melting (SLM, Keramit NP-S). Each of the 24-specimen groups was divided into two subgroups, according to the application, or lack thereof, of Nobil Metal Bonding (NMB). Two. different veneering ceramic systems were used: Ceramco iC (Dentsply Sirona) and Noritake Super Porcelain EX-3 (Noritake). The bond strength of the metal-ceramic system was evaluated using the three-point bending test and the modality of failure with SEM analysis. Three-way ANOVA with interactions was used to evaluate the influence of the metal production process, the presence or absence of the bonding agent, and the type of veneering ceramic on ceramic-metal adhesion. Results: All specimens exceeded the minimum bond strength of 25 MPa required by ISO Standard 9693-1:2012. The highest values of adhesion were registered for specimens manufactured with casted metal/Noritake veneering ceramic (40.59 ± 7.30 MPa). The lowest values were registered for specimens manufactured with CAD/CAM metal/NMB/ Ceramco iC veneering ceramic (29.47 ± 3.38 MPa). Conclusions: The fabrication method and= the type of veneering ceramic had a significant influence on the mean bond strength. The application of the NMB did not show an influence on bond strength.

Purpose: To evaluate the effect of a staining solution on the color stability of resins for complete dentures produced with conventional and digital technologies. Materials and Methods: A total of 60 resin specimens were prepared and divided into six groups of 10 specimens each: Probase Hot (PH; Ivoclar), IvoBase CAD (IBC; Ivoclar), Ivotion Dent (ID; Ivoclar), Ivotion Dent Multi (IDM; Ivoclar), Dima Print Denture Base (DPDB; Kulzer), and Dima Print Denture Teeth (DPDT; Kulzer). One surface of each specimen was polished following the manufacturer’s instructions. The CIELab color differences were evaluated before and after 28 days of immersion in a coffee solution and measured as ∆E using two dental spectrophotometers. One specimen for each group was selected for scanning electron microscopy (SEM) analysis at baseline and at 28 days. Results: Data analysis was performed with Kruskal-Wallis test and post-hoc Dunn test for comparison. Regarding specimens analyzed with VITA Easyshade, IDM white zone (polished and unpolished) scored higher (∆E = 0.87 and ∆E = 1.15, respectively). All milled samples (IBC, ID, IDM pink zone), scored significantly higher compared to PH and DPDT. Regarding SpectroShade, IDM pink zone performed better for both polished and unpolished specimens (∆E = 1.57 and ∆E = 2.07, respectively). ID demonstrated a statistically higher color stability compared to PH and DPDT. Regarding SEM analysis, any difference in surface morphology was observed between baseline and 28-day immersion analyses. Conclusions: Color stability was significantly higher in resin specimens obtained with digital technologies compared to conventional resin specimens afterimmersion in a staining solution.