Search Results (1,278)

The nanoscale surface topography and microhardness of additive and subtractive dental polymers were evaluated following exposure to environmental challenges. The study examined two 3D-printed resins (Saremco and Voco) and two milled CAD/CAM blocks (Vita Enamic and Tetric). Specimens were allocated to control or experimental groups and subjected to hydrothermal ageing (thermocycling), in vitro mechanical wear, or a combined protocol involving wear followed by thermal ageing. Surface microtopography was analysed both quantitatively and qualitatively using atomic force microscopy (AFM), while structural stability was assessed through surface microhardness testing. Statistical significance was determined using matrix comparisons (p < 0.05). Milled monolithic blocks demonstrated a dense, uniform baseline topography, whereas 3D-printed resins exhibited structural heterogeneity attributed to their layer-by-layer photocuring process. Saremco maintained polymer network stability under thermal stress (p = 0.1878), while Voco was highly susceptible to hydrothermal swelling and early matrix plasticization (p = 0.0084). The combined protocol of wear and thermal ageing resulted in advanced structural breakdown in all groups (p < 0.001). Industrial subtractive blocks exhibited greater resistance to oral environmental stresses. The ceramic framework of Vita Enamic limited polymer domain collapse, whereas Tetric experienced accelerated inter-layer delamination and embrittlement. The combined protocol of wear followed by thermal ageing resulted in significant and uniform degradation of surface microhardness and topographic roughness in all tested groups. Nevertheless, the additively manufactured resins demonstrated substantial structural integrity and exhibited low volumetric wear rates. Full article

Purpose: This study describes the manufacturing procedure for complete dentures using a milling cutting method with an individual correction of the prosthetic plane. Methods: Complete dentures were fabricated digitally using a hybrid protocol with individual assessment of the prosthetic plane. Results: Subjective and objective studies of evaluation of dentures were used. The sampling of functional impressions with the use of silicone masses of decreasing tension on dentures was used by a patient after the functional formation of their edges with Function type masses. The recording of occlusion on the pre-prepared prosthetic impressions using a silicone recorder was performed. Scanning of dentures and their occlusive relations by means of a laboratory scanner was performed in order to obtain virtual working models. A 3D face photograph of the dentures was taken using the Face Hunter device. Face Hunter offered an individualised adjustment of the prosthetic plane and a unique incorporation of the restoration in a given subject. New restorations in a computer programme were designed. A milling cutting of try-in test dentures was performed in order to make a control in the oral cavity. Control of the test dentures took place at the dentist’s office. The performance of new prosthetic restorations using a milling cutting method in the PMMA target material was evaluated in this study. Conclusions: The Face Hunter device offers an individualised incorporation of dentures in patients’ faces, which considerably improves the aesthetic aspect of the complete dentures. Full article

This in vitro study evaluated the effects of four surface treatments (no treatment, hydrofluoric acid [HF] etching, aluminum oxide [AlO] air abrasion, and tribochemical silica coating [TSC]) and two bonding agents (dedicated silane vs. silane-containing universal adhesive) on the microshear bond strength of four CAD/CAM glass-ceramic materials, including two zirconia-reinforced lithium silicate ceramics and two conventional glass-ceramics. Four CAD/CAM materials (Celtra Duo, IPS e.max CAD, IPS Empress CAD, and Vita Suprinity) were subjected to four surface treatments (no treatment, HF, AlO air abrasion, and TSC) and further divided according to bonding agent application: dedicated silane (Clearfil Ceramic Primer Plus) or silane-containing universal adhesive (Single Bond Universal). Microshear bond strength testing was performed after 24 h of water storage (n = 10). Failure modes were classified under stereomicroscopy, and surface topography was evaluated by SEM. Data were analyzed using three-way ANOVA and Tukey’s HSD test (α = 0.05). All three main factors and their interactions significantly affected bond strength values (p < 0.05; R² = 0.863). HF etching with silane produced the highest values for most materials. However, IPS Empress CAD treated with TSC and silane yielded the highest overall bond strength (25.2 MPa). Dedicated silane consistently outperformed the universal adhesive across all combinations. ZLS ceramics showed intermediate values with distinct etching patterns compared with conventional glass-ceramics. Optimal bonding protocols for CAD/CAM glass-ceramics are material-dependent. Dedicated silane application is recommended over silane-containing universal adhesives for maximum bond strength. Full article

This paper proposes a structured methodology for constructing a digital twin (DT) of a planned flexible manufacturing system (FMS) for gear wheel production, integrating value stream mapping (VSM), discrete-event simulation (DES), production scheduling, and CAD/CAM modeling into a hierarchical, iterative design framework. The methodology was validated on an industrial case study involving a Polish manufacturer of gear transmissions undergoing modernization from conventional machining to a fully automated system incorporating CNC machining centers, industrial robots, automated guided vehicles (AGVs), and an automated storage and retrieval system (ASRS). Production scheduling was performed using eight algorithms including a random-search method and an ant colony optimization (ACO) algorithm, applied to a representative of 1072 parts across 10 gear wheel types. Simulation models of both conventional and automated systems were developed in FlexSim 2024. The best random instance achieved a makespan of 72,317 s in the automated model, compared to 75,634 s for the list rule—a 4.4% improvement that corresponds to approximately 55 min of production time per batch. AGV fleet sizing experiments identified four vehicles as the optimal configuration, beyond which marginal gains fall below 2%. The proposed digital twin framework enables virtual commissioning, continuous production planning, and what-if analysis prior to and during physical system implementation. Full article

Background and Objectives: Periodontal health represents a condition characterized by homeostasis between the teeth and the surrounding supporting tissues and implies the absence of inflammation, confirmed by the lack of bleeding, epithelial attachment loss, mobility, or periodontal pocket formation. Fixed prosthetic restorations may compromise periodontal health already during the fabrication phase, given that decisions made during their planning and placement affect long-term clinical outcomes. The aim of this manuscript was to provide insight into the interaction between periodontal tissues and fixed prosthetic restorations. Materials and Methods: A narrative literature review was conducted using a structured search of the PubMed/MEDLINE, Scopus, and Google Scholar databases to identify studies addressing periodontal health in relation to fixed dental prostheses. The impacts of tooth preparation, gingival retraction methods, supracrestal tissue attachment, periodontal phenotype, crown emergence profile, and marginal fit of various biomaterials were analyzed. Results: According to the literature data, subgingival margin placement and violation of the supracrestal tissue attachment (biological width) induce chronic inflammation, loss of epithelial attachment, and alveolar bone resorption. Gingival retraction agents, used in chemomechanical retraction procedures, particularly ferric sulfate-based agents, may lead to a transient but significant spike in inflammatory markers and dysbiosis of the subgingival microbiome. Contemporary approaches, such as the biologically oriented preparation technique and the use of CAD/CAM (Computer-Aided Design and Computer-Aided Manufacturing) technology, may improve the precision of marginal fit. Zirconia restorations exhibit significantly better biocompatibility and reduced microbial adhesion compared to metal–ceramic restorations. Conclusions: Biological response of the periodontium to fixed prosthetic restorations depends on the complex interaction between the material, position of the marginal line, and oral hygiene control. Regardless of the material used or the fabrication technique employed, adequate plaque control and regular maintenance remain key factors in preserving periodontal health. Full article

CAD/CAM reinforced resin composites are increasingly used in restorative dentistry because of their favorable mechanical and esthetic properties. This in vitro study evaluated the effect of acidic exposure on surface properties and Streptococcus mutans biofilm formation on three CAD/CAM resin composites: a short-fiber-reinforced composite (SFRC), a woven glass fiber-reinforced composite (TRINIA; TR), and a resin nanoceramic-reinforced composite (Lava Ultimate; LU). Twenty-four specimens from each material were prepared and assessed for surface roughness and wettability using an optical profilometer and contact angle goniometer before and after 24 h of storage in neutral (pH 7) or acidic (pH 4) buffer solutions (n = 12 per group). Surface morphology was further examined using scanning electron microscopy (SEM). Biofilm formation was quantified using S. mutans colony-forming unit (CFU) counts, followed by confocal laser scanning microscopy (CLSM) for biofilm architecture and viability. At baseline, TR exhibited the highest roughness values (0.744 to 0.785 µm, p < 0.001), whereas no significant differences in contact angle were observed among materials. Acidic exposure significantly increased surface roughness and reduced contact angle values in all examined materials (p < 0.001). Compared to storage in neutral conditions, bacterial adhesion was significantly reduced in TR and LU stored in acid (p < 0.001), but SFRC showed no significant change (p = 0.079). Among specimens exposed to acidic conditions, TR exhibited the highest bacterial adhesion (3.24 log₁₀ CFU/mm²) relative to SFRC and LU (p < 0.001). CLSM analysis demonstrated denser biofilm accumulation on TR and LU compared with SFRC. These findings demonstrate that acidic exposure significantly affects the surface properties and bacterial adhesion behavior of CAD/CAM resin composites in a material-dependent manner. SFRC showed no statistically significant difference in S. mutans CFU/mm² between neutral and acidic storage conditions despite measurable surface changes, highlighting its potential suitability for clinical applications associated with acidic oral environments. Full article

The study presents an application of virtual prototyping and numerical analysis in engineering practice for an in-stream hydropower system. The performed analyses aimed to compare different design configurations of the crossflow turbine. All simulations use virtual prototypes and computational fluid dynamics to review design performance in detail under various environmental conditions. Specifics of mixed fluid flows are outlined. The major focus is on virtual prototype testing, aiming to demonstrate its ability to deliver fast results for complex, expensive structures. This work is a good example of the practical application of numerical analysis and virtual prototyping and demonstrates a specific, complex field, such as computational fluid dynamics. Full article

Background: In the field of minimally invasive restorative dentistry, ultrathin (<0.5 mm thickness) ceramic occlusal veneers are increasing being used as alternatives to full-coverage crowns, particularly for mild occlusal wear and not deep caries. However, only limited research attention has been given to how marked reduction in the thickness of a veneer restoration affects its mechanical performance. The purpose of the present in vitro study was to compare the performance of restorations that comprised a 0.3 mm thick zirconia veneer to the case when a lithium disilicate veneer was used, under quasi-static compressive loading. Methods: Forty extracted human molars, without caries, cracks or fractures and with intact coronal structure, were randomly assigned to two groups: lithium disilicate occlusal veneers (n = 20) and zirconia occlusal veneers (n = 20). The teeth were embedded in acrylic resin up to the cementoenamel junction. Digital scans were used to record the original anatomy and guide restoration design. Standardized occlusal preparations were performed using a 0.3 mm reduction protocol and verified with silicone guides to support a biomimetic, tooth-preserving approach. After preparation, the teeth were rescanned, and restorations were designed and fabricated using CAD/CAM technology. Lithium disilicate restorations were milled from Ivoclar Porcelain System [IPS], esthetic maximized [e.max] computer-aided design [CAD] blocks, whereas zirconia restorations were milled from Prettau 3 zirconia discs. Restorations were adhesively cemented with dual-cure resin cement following material-specific surface treatment protocols. Fracture resistance was tested using a universal testing machine under compressive loading until failure. Results: The fracture loads with lithium disilicate and zirconia occlusal veneers were 481.45 ± 68.23 N and 720.93 ± 95.44 N, respectively. Fracture was catastrophic in lithium disilicate occlusal veneers whereas it was not so when zirconia veneer was used. Conclusion: Quasi-static compressive fracture load when a lithium disilicate veneer was used was significantly lower than when a zirconia veneer was used. Full article

The ongoing development of subtractive options for indirect restorations places clinicians in a position that requires adaptation, understanding and choosing of the most suitable option for the long-term survival of the restoration. Mechanical parameters represent important indicators of long-term success. Consequently, this research aimed to assess the impact of water sorption on the mechanical properties of two direct resin composites, Gradia Direct Anterior A2 and Filtek Z550 A2 and three CAD/CAM subtractively manufactured dental resin composites, Vita Enamic, Brilliant and Cerasmart. A total of one hundred specimens (50 control, 50 underwent this protocol: dehydration, immersion in distilled water for 30 days and then re-desiccation), standardized to the dimensions of 14 mm × 4 mm × 1.2 mm were subjected to three-point bending test (based on ISO 4049:2019 and ISO 6872:2015), in order to find out the flexural strength and the elastic modulus of the material at the breaking point. Then, the fractured sample surfaces were fractographical analyzed. Using the two-parameter Weibull approach, the Weibull modulus (m) and the characteristic strength (σ₀) were evaluated. In this investigation, the elastic modulus varied from 5.8 (Gradia Control) to 20.31 (Vita Degraded) GPa, with the upper limit close to the values of natural dentin (17.7–29.8 GPa). The values of flexural strength ranged from 174.47 (Brilliant Control) to 79.2 (Gradia Control), subtractively processed materials demonstrating higher flexural strength and elastic modulus values than the direct resin composites, which is related to their high inorganic filler content. All material groups, except for Gradia Control, had a flexural strength more than the 80 MPa minimum value needed to sustain masticatory force. The dehydration and hydration cycles did not have a statistically significant influence on the mechanical properties of the material. The fractographic analysis revealed fracture patterns and features associated with the microstructure, with the PICN category material being particularly notable. Weibull analysis revealed that the direct resin composite materials exhibited higher reliability, lower data scatter and CAD-CAM materials showed greater characteristic strength, with a notably high performance of the nano-hybrid direct resin composite. Full article

This study examines the influence of the dynamic pressure control parameter in the nozzle during melt deposition onto the build platform (k-Factor), also known as Linear Advance or Pressure Advance in different firmware implementations, on the quality of parts produced using the Fused Deposition Modeling (FDM) technology. The investigation was conducted based on printed test specimens made from Ingeo Biopolymer 4043D, with k-Factor values varied in the range of 0.01 to 0.20 under comparable process conditions. Dimensional measurements were performed along the X and Y axes, and visual analysis was carried out to identify defects in the specimens. The results from statistical analysis and visual inspection reveal a clear correlation between the k-Factor value and part quality. An optimal balance between dimensional and geometric stability was achieved at k-Factor = 0.04, identifying it as a suitable value for the material and process conditions used. Full article

This study extended a previously established intraoral scanning (IOS) and optical coherence tomography (OCT) dual-modality monitoring workflow for computer-aided design/computer-aided manufacturing (CAD/CAM) restorations to three additional crown material classes alongside a resin composite (RECO) reference. Four material classes were investigated ($n=8$ each): RECO, polymer-infiltrated ceramic network (PICN), lithium disilicate ceramic (LDSC), and zirconia-reinforced lithium silicate ceramic (ZLSC). Monolithic crowns were adhesively luted to standardized human molar abutment teeth and aged by cyclic loading (50500$\mathrm{N}$, 2$\mathrm{Hz}$, 37 2${}^{\circ }\mathrm{C}$, up to 1250000 cycles) in a mouth-motion simulator. IOS and handheld OCT were performed at baseline and after every 250000 cycles under phantom-head conditions; correspondence was assessed using Spearman’s rank correlation coefficient (exploratory, uncorrected for multiple comparisons). OCT consistently showed higher defect extents than IOS across all material classes and timepoints. While no significant IOS-OCT associations were found for RECO and the PICN, OCT detected full-thickness vertical subsurface damage propagation from the earliest timepoint in LDSC and ZLSC, with IOS-derived surface wear remaining markedly lower. Surface-based monitoring alone did not reliably reflect subsurface damage propagation, a dissociation most pronounced in the vertical dimension and silicate-based materials. Intraoral OCT may provide complementary, non-invasive subsurface information to support individualized recall scheduling and minimally invasive repair decisions. Full article

Background/Objectives: Single-retainer Maryland adhesive restorations provide a minimally invasive fixed option for replacing missing anterior teeth in young patients. When congenital absence of a maxillary lateral incisor is associated with a contralateral conoid lateral incisor, the clinical problem extends beyond tooth replacement to bilateral symmetry management. This case report describes a digital-restorative workflow combining a single-retainer lithium disilicate Maryland adhesive restoration with a pontic-derived stamp technique for contralateral symmetry correction. Methods: A medically healthy 13-year-old patient presented with congenital absence of the maxillary left lateral incisor (FDI 22; Universal 10) after orthodontic treatment and had been wearing a removable appliance to replace the single missing tooth. The contralateral maxillary right lateral incisor (FDI 12; Universal 7) presented with conoid morphology, further compromising anterior symmetry. Clinical assessment confirmed ideal mesiodistal space at FDI 22, a vital and unrestored FDI 21 with intact enamel and healthy periodontal support, and the absence of abnormal overjet, overbite, or excursive contact pattern. Based on the findings, a single-retainer Maryland adhesive restoration was fabricated from lithium disilicate (IPS e.max CAD) and bonded to the maxillary left central incisor (FDI 21; Universal 9) using an enamel-only preparation and adhesive cementation protocol. The fixed restoration was combined with a pontic-derived stamp workflow to guide direct composite reshaping of the contralateral conoid lateral incisor. Results: At 1-year follow-up, no debonding, sensitivity, marginal discoloration, or soft-tissue inflammation was observed. The contralateral composite reshaping remained clinically stable, and the patient and guardian reported improved comfort and esthetic satisfaction compared with the previous removable appliance. Conclusions: This case suggests the short-term clinical feasibility of combining a single-retainer lithium disilicate Maryland adhesive restoration with a pontic-derived stamp workflow to achieve minimally invasive tooth replacement and contralateral symmetry correction. Longer follow-up and broader case series are required to confirm the long-term predictability and reproducibility of this approach. Full article

This report describes a 72-year-old patient for whom a maxillofacial prosthesis was created to treat trismus and jaw deviation after mandibulectomy for osteoradionecrosis following radiotherapy for cancer. The patient’s chief complaints were an ill-fitting denture, discomfort, and difficulty with mastication. Clinical examination revealed a right-sided lateral mandibular defect, trismus, and right-sided deviation of mandibular occlusion. The diagnosis was discomfort associated with ill-fitting dentures. A resin-based denture was created using the piezography technique. Although the patient was satisfied wearing the new resin-based prosthesis, it was thin because of the limited denture space and developed a fracture. Thereafter, a metal-based denture was fabricated. Digital impressions were obtained with an intraoral scanner. A prosthesis with a metal framework as an internal support was recreated using CAD/CAM technology. This case report demonstrates the feasibility of a digital workflow for prosthesis refabrication in a patient with complex mandibular defects. Full article

The long-term success of zirconia restorations depends on the durability of the resin–zirconia bond. This study evaluated the microshear bond strength (μSBS) of an MDP-containing universal adhesive, Scotchbond Universal Plus Adhesive, compared with its predecessor, Scotchbond Universal Adhesive, when bonded to three generations of CAD/CAM-fabricated zirconia ceramics. Sixty zirconia specimens were fabricated from 3Y-TZP (IPS e.max ZirCAD), 4Y-PSZ (IPS e.max ZirCAD MT), and gradient zirconia (IPS e.max ZirCAD Prime; 3Y-TZP/5Y-PSZ). Following polishing, sintering, and airborne-particle abrasion with 50 μm Al₂O₃ particles, specimens received either Scotchbond Universal Plus Adhesive or Scotchbond Universal Adhesive. Resin cement cylinders were bonded with a dual-cure resin cement and subjected to thermal cycling (20,000 cycles; 5–55 °C) prior to μSBS testing. Data were analyzed using one-way ANOVA, independent-samples t-tests, and Fisher’s exact test (α = 0.05). Significant differences in μSBS were observed among zirconia generations for both adhesive systems (p < 0.05). The highest bond strengths were recorded for 4Y-PSZ bonded with Scotchbond Universal Adhesive (15.36 ± 3.00 MPa) and Scotchbond Universal Plus Adhesive (14.67 ± 4.52 MPa), whereas the lowest values were obtained for 3Y-TZP (8.91 ± 3.53 MPa and 9.20 ± 3.52 MPa, respectively). No significant differences were detected between the two adhesive systems within any zirconia generation (p > 0.05). Failure mode analysis revealed predominantly adhesive and mixed failures, with no significant differences in the distribution of failure modes among groups (p > 0.05). In conclusion, zirconia generation significantly influenced bond strength, whereas Scotchbond Universal Plus Adhesive demonstrated bonding performance comparable to that of Scotchbond Universal Adhesive after thermocycling. Among the tested substrates, 4Y-PSZ exhibited the most favorable bonding performance. Full article

This article introduces a modified reverse scan technique for abutment teeth that incorporates laboratory scanners into a fully digital workflow to enhance accuracy and reduces the impact of stitching and merging errors associated with long-span intraoral scans when fabricating extensive tooth-supported prostheses. This cost-effective, time-saving, and versatile procedure uses a 3D-printed interim tooth-supported prosthesis that is sectioned, bonded intraorally, and scanned with a laboratory scanner to improve the virtual definitive cast. The modification is performed using free software. Full article