Objective: This study aims to evaluate the influence of pontic length and design on the fracture resistance of zirconia fixed dental prostheses (FDPs). By assessing different span lengths under controlled mechanical loading conditions, the research seeks to provide insights into optimizing the structural integrity of zirconia dental bridges. Materials and Methods: A total of 20 zirconia bridges were fabricated and tested in vitro. Ten bridges were designed to replace a single missing molar (tooth 46), with a pontic span of 11 mm, while the remaining ten were crafted for two missing teeth (35 and 36), featuring a longer pontic span of 17 mm. The zirconia frameworks were milled using the Wieland Zenotec^® Select Hybrid system and cemented onto metal abutments with Voco Meron Plus QM resin-reinforced glass ionomer cement. The specimens were subjected to occlusal loading using a ZwickRoell ProLine Z005 testing machine at a crosshead speed of 1 mm/min until fracture occurred. Results: The mechanical testing revealed a significant correlation between pontic length and fracture resistance. The mean fracture resistance for three-unit bridges (single pontic) was 3703 N, whereas four-unit bridges (double pontic) exhibited a significantly lower resistance of 1713 N. These findings indicate that increased span length reduces the fracture resistance of zirconia restorations due to higher stress accumulation and reduced rigidity. Conclusions: This study underscores the importance of pontic length and design in determining the fracture resistance of zirconia restorations. Shorter spans exhibit greater structural stability, reinforcing the need for careful treatment planning when designing multi-unit zirconia bridges. By optimizing bridge parameters, clinicians can improve clinical outcomes and extend the longevity of zirconia prostheses in restorative dentistry.

Objective: This in vitro study aimed to evaluate the influence of cervical margin design—tangential versus chamfer—on the fracture resistance of monolithic crowns fabricated from lithium disilicate and zirconia ceramics. Materials and Methods: Forty extracted human molars were randomly assigned to two preparation types: chamfer and tangential. Each group was restored with CAD/CAM-fabricated crowns made from either zirconia (IPS e.max^® ZirCAD Prime) or lithium disilicate (IPS e.max^® CAD), resulting in four subgroups (n = 10). Standardized adhesive cementation protocols were applied. After 24 h storage in distilled water, the specimens underwent static load-to-failure testing using a ZwickRoell ProLine Z005 universal testing machine. Results: Zirconia crowns with chamfer margins exhibited the highest mean fracture resistance (2658 N), while lithium disilicate crowns with tangential margins showed the lowest (1862 N). Chamfer preparation significantly increased the fracture resistance of lithium disilicate crowns (p < 0.01), whereas margin design had no significant effect on zirconia. All restorations exceeded physiological masticatory forces, confirming their clinical viability. Conclusions: Cervical margin design significantly affected the fracture performance of lithium disilicate crowns but not zirconia. Chamfer preparations are recommended when using lithium disilicate to optimize mechanical strength. These findings underscore the importance of preparation geometry in guiding material selection for CAD/CAM ceramic restorations.

Aim: This in vitro study aimed to evaluate the adhesive performance of zirconia and lithium disilicate Maryland cantilever restorations on prepared and non-prepared anterior abutment teeth. While conventional clinical protocols involve abutment tooth preparation, no-preparation (no-prep) restorations have emerged as a viable, minimally invasive alternative. This study compared the adhesion fracture resistance (N) of zirconia restorations on non-prepared enamel surfaces with those on prepared surfaces exposing the dentin. Additionally, the zirconia restorations were compared with lithium disilicate Maryland cantilever restorations, a more common yet costly alternative. Materials and Methods: Forty extracted anterior teeth were allocated into four groups based on preparation type (prepared vs. non-prepared) and material (zirconia vs. lithium disilicate). Each group received cantilevered single-unit FPDs fabricated via CAD/CAM and adhesively cemented using Variolink^® Esthetic DC. Standardized loading was applied using a universal testing machine, and the fracture resistance was recorded. Results: The fracture resistance ranged from 190 to 447 N in the zirconia groups and from 219 to 412 N in the lithium disilicate groups. When comparing all the zirconia versus all the lithium disilicate ceramic restorations, regardless of tooth preparation, no statistically significant difference was found (p = 0.752). However, the non-prepared restorations exhibited significantly higher fracture resistance than their prepared counterparts (p = 0.004 for zirconia; p = 0.012 for lithium disilicate ceramic). All the failures were attributed to tooth fracture, except one zirconia restoration, with no debonding observed. Conclusions: Both zirconia and lithium disilicate Maryland cantilever restorations demonstrated reliable adhesive performance when bonded using appropriate surface conditioning and adhesive protocols. Interestingly, the non-prepared designs exhibited higher fracture resistance than the prepared abutments, highlighting their potential advantage in minimally invasive restorative dentistry. Zirconia Maryland bridges, in particular, represent a cost-effective and mechanically resilient option for anterior single-tooth replacement.

Background and Objectives: Provisional restorations are essential in fixed prosthodontics, ensuring esthetics, function, and biological protection during treatment. Recent advances in CAD/CAM technologies have enabled the fabrication of provisional materials with enhanced color stability and fracture resistance compared to conventional chairside polymeric materials. This study aimed to compare the color stability and fracture strength of provisional crowns fabricated using CAD/CAM and a conventional direct chairside technique. Materials and Methods: A total of 40 provisional crowns (four materials, n = 10 each group) were fabricated for a mandibular molar 3.6 using two workflows: CAD/CAM-milled poly(methyl methacrylate) (PMMA), high-impact polymer composite (HIPC; Bredent), and Ambarino composite (Creamet), and directly fabricated 3M™ Protemp™ (Scutan technique), respectively. Color stability was evaluated after seven-day immersion in coffee and red wine at 37 °C using a spectrophotometer (CIE L*a*b* system). Fracture resistance (F_max) was measured under axial load in a universal testing machine. Data were analyzed by one-way ANOVA and Tukey’s HSD (α = 0.05). Results: Significant differences were observed among materials (F(3,36) = 212.6, p < 0.001). HIPC showed the highest mean fracture resistance (2068.9 ± 104.0 N), followed by PMMA (1215.8 ± 61.4 N) and 3M™ Protemp™ (1183.4 ± 86.4 N), while Ambarino exhibited the lowest (555.4 ± 25.4 N). Regarding color stability, Ambarino demonstrated the smallest ΔE* (1.1 ± 0.2), followed by PMMA (2.0 ± 0.3), HIPC (2.8 ± 0.3), and Protemp™ (4.9 ± 0.4). Only Protemp™ exceeded the clinical perceptibility threshold (ΔE* > 3.3). Conclusions: Both manufacturing methods and material compositions significantly influence the optical and mechanical properties of provisional restorations. CAD/CAM-milled HIPC and PMMA provided superior fracture strength and clinically acceptable color stability, suggesting their suitability for long-term or high-load temporary crowns compared with chairside-fabricated composites, particularly in posterior regions.

Background/Objectives: Accurate full-arch implant impressions are essential for predictable digital prosthodontics, yet the performance of different intraoral scanners (IOSs) remains variable. This in vitro study compared the trueness and precision of three widely used IOSs-Sirona Primescan, 3Shape TRIOS Core, and Medit i700-in a standardized full-arch implant model. Methods: A maxillary model with six multi-unit implants was digitized using a high-accuracy laboratory scanner to obtain the reference dataset. Each IOS was used to perform ten scans, exported as unmodified STL files. Accuracy was evaluated in Geomagic Control X through a two-step alignment and a peri-implant region-of-interest deviation analysis. Trueness (mean absolute surface deviation, µm) and precision (SD) were compared using one-way ANOVA with Tukey’s test (α = 0.05). Results: Primescan and TRIOS Core showed comparable trueness (202.76 ± 13.89 µm and 204.21 ± 2.61 µm, respectively), while Medit i700 demonstrated significantly higher deviations (221.05 ± 6.28 µm) (p < 0.05). TRIOS Core exhibited the highest reproducibility across repeated scans. Conclusions: The three scanners demonstrated measurable accuracy differences under standardized conditions. Primescan and TRIOS Core performed similarly in trueness, with TRIOS Core achieving superior precision. Medit i700 showed higher deviation values but remained consistent in its performance. These findings highlight measurable differences in accuracy and reproducibility among intraoral scanners under standardized laboratory conditions and may assist clinicians in selecting appropriate devices for full-arch digital implant workflows; however, clinical validation is required to confirm their performance in vivo.

Objectives: The aim of this study was to present and describe a digital workflow integrating Digital Smile Design (DSD) with computer-aided design/computer-aided manufacturing (CAD/CAM) and additive manufacturing technologies for the fabrication of dental preparation guides, focusing on workflow feasibility, design reproducibility, and clinical handling. Materials and Methods: A digital workflow was implemented using intraoral scanning and Exocad DentalCAD 3.1 Elefsina software to design dental preparation guides based on digitally planned restorations. Preparation margins, insertion paths, and minimal material thickness were defined virtually. The guides were fabricated using both subtractive (PMMA milling) and additive (stereolithographic-based 3D printing) manufacturing techniques. Post-processing included chemical cleaning, support removal, additional light curing, and manual finishing. The evaluation was qualitative and descriptive, based on visual inspection, workflow performance, and guide adaptation to printed models. Results: The proposed digital workflow was associated with consistent fabrication of preparation guides and predictable transfer of the virtual design to the manufactured guides. Digital planning facilitated clear visualization of preparation margins and insertion axes, supporting controlled and minimally invasive tooth preparation. The workflow demonstrated good reproducibility and efficient communication between clinician and dental technician. No quantitative measurements or statistical analyses were performed. Conclusions: Within the limitations of this qualitative feasibility study, the integration of DSD with CAD/CAM and 3D printing technologies represents a viable digital approach for designing and fabricating dental preparation guides. The workflow shows potential for improving predictability and communication in restorative dentistry.