Search Results (33)

The purpose of this study was to use the finite element analysis method to determine the influence of framework material on stresses in different parts of a model of an All-on-4 prosthesis supported by bendable monoblock implants. A three-dimensional solid model of an edentulous mandible was reconstructed from computed tomography data and segmented using 3DSlicer. Four bendable monoblock implants were positioned in accordance with the All-on-4 configuration. Screw-retained prostheses were modeled with the framework considered fabricated using one of five materials. These were cobalt–chromium (Co-Cr) alloy, titanium (Ti) alloy, polyetheretherketone (PEEK), polyetherketoneketone (PEKK), and a glass fiber-reinforced polymer composite (FRC) material. Four types of clinically relevant loads (300 N) were applied statically, namely, unilateral oblique, unilateral vertical, bilateral oblique, and bilateral vertical. Maximum and minimum principal stresses were determined in the cortical bone, and maximum von Mises stress was determined in each of the other parts of the model. Across most loading conditions, PEEK and PEKK showed higher stress values in the cortical bone and in the implants. In the screws, PEEK and PEKK also showed higher stress values, except in the anterior implant screws under bilateral loading conditions. In the framework, the highest stresses were obtained when a metal was the material of fabrication. Across all loading conditions, with FRC, the stress transfer was balanced. Thus, the prevent results suggest that FRC may be a suitable alternative to metallic materials for fabricating the framework of an All-on-4 prosthesis supported by bendable monoblock implants. Full article

Full-arch implant-supported rehabilitations are widely recognized as an effective treatment option for edentulous patients. Nevertheless, clinical decision-making regarding patient selection, surgical planning, prosthetic material choice, and long-term maintenance protocols remains heterogeneous and requires structured evidence-based guidance. A modified Delphi consensus process was conducted involving 29 experts during the Italian Consensus Conference. A systematic literature review covering the period 2015–2024 was performed, and the certainty of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework. Consensus was predefined as ≥90% agreement. Seven evidence-based consensus statements were developed addressing: (1) periodontal risk assessment using validated tools; (2) guided bone regeneration outcomes with technique-specific indications; (3) comparative survival of four versus six implants in mandibular full-arch rehabilitations; (4) equivalence of tilted and axial implant configurations; (5) prosthetic material selection, with monolithic zirconia showing high survival; (6) risk-stratified supportive maintenance protocols associated with a reduction in peri-implantitis incidence; and (7) systemic risk stratification, including absolute and relative contraindications, medication-related osteonecrosis of the jaw (MRONJ) risk management, and perioperative antibiotic prophylaxis. Full article

The accuracy of digital impressions in fully edentulous cases is limited by the lack of anatomical reference structures, potentially affecting passive fit. The effects of scanner type, impression level, and scan body splinting on accuracy remain insufficiently elucidated. This in vitro study aimed to evaluate the effects of different intraoral scanners, scanning levels, and scan body splinting methods on digital impression accuracy. A fully edentulous mandibular model with four implants (All-on-4) was fabricated, and scan bodies were connected at either the implant or multi-unit abutment level. Five splinting methods (nonsplinted, floss, orthodontic elastomeric, chain attachments, and single attachments) were applied, creating 10 experimental groups. Each group was scanned using three intraoral scanners: iTero Lumina (Align Technology, Tempe, AZ, USA), TRIOS 3 (3Shape A/S, Copenhagen, Denmark), and Medit i700 (Medit Corp, Seoul, Republic of Korea), with four repeated scans per scanner (120 scans total). Trueness and precision were assessed based on linear and angular deviations using Geomagic Control X (3D Systems, Rock Hill, SC, USA). Scanner type and scanning level significantly affected accuracy (p < 0.05), with TRIOS 3 showing higher deviations, while multi-unit abutments reduced deviations. Splinting methods showed no significant effect on accuracy, and precision did not differ among groups. Scanner type and scanning level significantly influenced digital impression accuracy; however, splinting methods yielded no significant effect. Precision remained comparable among groups. Full article

The increasing densification of cell-free massive multiple-input multiple-output (MIMO) networks makes access point switch on/off (ASO) a key mechanism for improving energy efficiency in future wireless systems. While reinforcement learning (RL) has been explored for ASO, differences in modeling assumptions and evaluation scope leave open questions regarding robustness and scalability. In this work, ASO is investigated from an explicit energy-efficiency perspective using a RL framework based on Proximal Policy Optimization (PPO). The policy learns state-dependent AP activation under partial observability using compact per-access point (AP) large-scale fading statistics and power parameters, without requiring instantaneous small-scale channel state information or combinatorial search, enabling practical online implementation. A comprehensive evaluation is conducted under a unified and reproducible simulation framework across three cell-free deployment scenarios of increasing size that preserve AP density while incorporating realistic channel and power consumption models. Performance is assessed through both average and distribution-based metrics. Numerical results show that the PPO-based policy consistently outperforms random activation and the all-on baseline, achieving energy-efficiency improvements of up to 66% and nearly 50%, respectively, while activating a comparable number of APs. Moreover, the learned policy maintains robust performance as the network scales, reducing the likelihood of highly energy-inefficient operating regimes. Full article

Full-arch zirconia prostheses for mandibular All-on-4 rehabilitations are provided as screw-retained monolithic zirconia (Zr-Mono) or as a zirconia suprastructure luted to a CAD/CAM titanium bar (Zr-TiBar). Because zirconia is a brittle and flaw-sensitive ceramic, design assessment should incorporate stress-field-weighted fracture risk. This in silico study compared zirconia tensile stress, deformation, and Weibull-based reliability between Zr-Mono and Zr-TiBar designs in a standardized edentulous mandibular All-on-4 model (posterior implants tilted 30°) using linear static finite element analysis. Accordingly, 300 N posterior unilateral loads were applied at the first molar (axial; 45° oblique). Outcomes were maximum principal tensile stress in zirconia (S1max), total prosthesis deformation, and Weibull-predicted fracture probability (Pf) derived from the tensile S1 field. Under axial loading, S1max was essentially identical between designs (~277 MPa). Under oblique loading, S1max was modestly lower for Zr-TiBar (~227 MPa) than for Zr-Mono (~234 MPa), and deformation was slightly lower for Zr-TiBar (<0.07 mm in all cases). Pf remained very low for both designs (10⁻⁶–10⁻⁷ range) and differed only slightly between them. Under the modeled single 300 N posterior load case, the titanium-bar support reduced deformation and modestly reduced oblique-load peak tensile stress but did not materially reduce the predicted zirconia Pf compared with monolithic zirconia. Full article

Background/Objectives: The All-on-4 technique is a minimally invasive approach for full-arch oral rehabilitation. In cases of anterior bone resorption, the classic All-on-4 configuration may be limited by insufficient bone for axial implant insertion. An effective alternative is the “M” configuration, where all four implants are inserted at approximately 30°. This report presents a clinical case of full-arch rehabilitation using personalized surgical guides with internal cooling, designed to optimize irrigation and prevent thermal bone damage. Methods: A 57-year-old female patient underwent digital planning and flapless guided implant surgery. At the maxilla, four DENTIS SQ implants were inserted in an “M”-shaped configuration (4 × 10 mm anterior, 4 × 14 mm posterior). Before insertion, implant beds were prepared using surgical templates with internal irrigation channels. At the mandible, four posterior implants (4 × 8 mm) were placed using dentally supported guides with internal cooling. The surgical guides were designed using Implastation and Blue Sky Plan, 3D-printed in biocompatible resin and sterilized before use. We performed the osteotomies under controlled irrigation with continuous saline flow through the integrated cooling channels. Results: The guides ensured accurate implant positioning. We did not observe intraoperative complications, and all implants achieved primary stability above 35 N·cm. Postoperative healing was uneventful, with minimal edema and no mucosal dehiscence. These indirect clinical indicators suggest that the guide also ensured effective cooling. Radiographic follow-up confirmed correct 3D positioning and intimate bone-implant contact. Conclusions: This case study shows that personalized surgical guides with integrated coolant channels may provide a safe and precise solution for flapless All-on-4 “M” rehabilitations, reducing thermal risks and enhancing surgical accuracy. Full article

Background/Objectives: Implant-supported rehabilitations using the All-on-4 concept represent a viable treatment option for completely edentulous patients. The guided surgery software allows for the performance of a flapless computer-guided surgery with similar results to those achieved through a flap surgery. This study aimed to evaluate the long-term outcomes of complete edentulous implant-supported rehabilitations using an All-on-4 arrangement, following a computer-guided protocol. Methods: A total of 111 patients (68 females, 43 males) with an average age of 60.9 years ± 9.67 years were treated. The primary outcome measures were implant and prosthetic survival. Secondary outcome measures were marginal bone loss (MBL) and the incidence of mechanical and biological complications. Results: Thirty-nine patients were lost to follow-up. Thirty-seven implants and five prostheses failed, rendering a 92.5% implant cumulative survival rate and a 96.2% prosthetic survival rate at 12 years. The average MBL per implant was 1.19 ± 1.16 mm, with 1.26 ± 1.33 mm for axial implants and 1.12 ± 0.95 mm for tilted implants at 10 years. The incidence rate of mechanical complications at the patient level was 90.1% for provisional prostheses and 55.9% for definitive prostheses. The rate of biological complications was 14.3% at the implant level. Conclusions: Full-arch rehabilitations following an All-on-4 implant arrangement and assisted by a computer-guided protocol may be a viable alternative for patients with edentulism/hopeless teeth in the long term. Full article

Background/Objectives: Edentulism represents a major public health challenge, causing disorders of social, psychological and biological origin. Full-arch implant-supported restorations represent a viable alternative to mitigate this problem. This study aimed to evaluate immediate implant-supported restorations for the rehabilitation of the edentulous maxilla using four implants and distal implant tilting between 15 and 20 years. Methods: A total of 740 patients were included (women: 440; men: 300; average age: 55.3 years) rehabilitated with 740 prostheses, supported by 2960 dental implants. The primary outcome measure was prosthetic/implant cumulative survival and success (CSurR;CSucR). Secondary outcome measures included marginal bone loss (MBL), and the incidence of complications was evaluated as a secondary outcome measure. The outcomes were evaluated at 15 and 20 years. Results: In total, 287 patients (38.8%) with 1148 implants (38.8%) were lost to follow-up. A total of 170 implants (5.7%) in 101 patients (13.6%) failed, resulting in an implant CSurR and CSucR of 90.7% and 84.6%, respectively, after up to 20 years of follow-up. The prosthetic success rate was 98.1%. The average MBL was 1.07 mm ± 1.38 mm and 1.46 mm ± 1.56 mm at 15- and 20-years, respectively. Mechanical complication incidence was 78.5%, occurring in 581 patients (provisional prostheses: n = 448, 60.5%; definitive prostheses: n = 374, 50.5%). Biological complications occurred in 449 implants (15.2%) in 260 patients (35.1%). Biological complications and smoking habits were major risk indicators. Conclusions: Considering the study limitations, it can be concluded that the current rehabilitation concept is a viable treatment option in the long term, with mechanical and biological maintenance being necessary throughout the patients’ lives. Full article

Background/Objectives: Fully digital workflows used in implant dentistry have been evolving to improve rehabilitation times and patient satisfaction. More studies are necessary for full scientific validation. The aim of this study was to evaluate the 6-month outcome of implant-supported fixed prostheses for full edentulism rehabilitation using OnX Tough 2 resin (SprintRay) and the Pro 2 (SprintRay) 3D printer following the All-on-4 concept. Methods: This study included 16 patients (10 female, 6 male) with 20 implant-supported fixed full-arch prostheses following the All-on-4 concept (10 rehabilitations for each stackable guide and photogrammetry protocols). Primary The primary outcome measure was implant and prosthetic survival. The secondary outcome measures included manufacturing issues, prosthetic passive fit, marginal bone loss (MBL), mechanical and biological complications, modified plaque and bleeding indexes, pocket depths, patient subjective evaluation, and the Oral Health Impact Profile. Results: No patients were lost to follow-up. Two prostheses failed and 2 two implants were lost, resulting in a cumulative survival rate of 90% and 97.5% at 6 months for prostheses and implants, respectively. The mean MBL was 0.31 mm ± 0.52 mm at 4 months. The mechanical complications rate was 50% at patient level. One patient (6.3%) experienced one biological complication. The grades regarding “comfort of prostheses in the mouth” and “overall chewing feeling” were 9.35 ± 1.29 and 8.79 ± 1.67 out of 10, respectively. The mean total sum of the OHIP-14 was 1.61 out of 56. Conclusions: Implant-supported full-arch rehabilitations with fixed prostheses following the All-on-4 concept, through a fully digital workflow protocol, are a viable option in the short term. Full article

Finite element analysis is commonly used to evaluate implant biomechanics, yet limited data exist on arch form and trabecular-surfaced implants. This study aimed to investigate the biomechanical impact of a designed trabecular surface compared with a standard implant surface in full-arch, four-implant-supported restorations, using two mandibular arch forms and four placement configurations. Finite element analyses were conducted under a 250-N oblique load applied at 30° to the posterior segment. The prosthesis was modeled as a titanium–acrylic hybrid structure. Stress distribution was evaluated in cortical and cancellous bones, implants, and prosthetic frameworks. Implants with a trabecular surface demonstrated lower stress concentrations in both bone and implant structures. The von Mises stress at the neck of the posterior implant decreased from 383.3 MPa (standard implant, hyperbolic arch, configuration 1) to 194.9 MPa (trabecular-surfaced implant, U-shaped arch, configuration 4). Similarly, the average maximum principal tensile stress in cortical bone reduced from 44.32 to 40.99 MPa with the trabecular design. Among placement strategies, Configuration 3 (all implants tilted distally) yielded the highest bone stress, whereas Configurations 2 and 4 provided more favorable load distribution. Stress concentrations were also higher in hyperbolic arches, whereas U-shaped arches exhibited a more uniform distribution. These findings emphasized the biomechanical advantage of the designed trabecular surface in reducing stress across bone and implant components, indicating that trabecular titanium may represent a more reliable and cost-effective alternative for clinical applications, potentially enhancing long-term stability. Independently, the arch form and placement strategy also significantly influenced load distribution. Despite assumptions such as isotropic, homogeneous, and linearly elastic material properties, and the use of a single oblique loading condition, this study offers valuable biomechanical insights such as the stress-reducing effect of the trabecular surface, the influence of three-dimensional arch anatomy on stress concentration sites, and the necessity of selecting implant configurations according to arch forms, which may inform future full-arch implant rehabilitations. Full article

Convolutional neural networks (CNNs) can efficiently extract image features and perform corresponding classification. Typically, the CNN architecture uses the softmax layer to map the extracted features to classification probabilities, and the cost function used for training is the cross-entropy loss. In this paper, we evaluate the influence of a number of representative composite cross-entropy loss functions on the learned feature space at the fully connected layer, when a target classification is introduced into a multi-class classification task. In addition, the accuracy and robustness of CNN models trained with different composite cross-entropy loss functions are investigated. Improved robustness is achieved by changing the loss between the input and the target classification. Preliminary experiments were conducted using ResNet-50 on the Cholec80 dataset for surgical tool recognition. Furthermore, the model trained with the proposed composite cross-entropy loss incorporating another target all-one classification demonstrates a 31% peak improvement in adversarial robustness. Adversarial training with target adversarial samples yields 80% robustness against PGD attack. This investigation shows that the careful choice of the loss function can improve the robustness of CNN models. Full article

This study evaluates the biomechanical effects of different implant configurations in various mandibular arch types using finite element analysis (FEA). Stress distribution and deformation patterns were analyzed under different loading conditions in square, U-shaped, and V-shaped arches. The results indicate that increasing the number of implants generally reduces cortical bone stress, particularly in U and V arches, while implant-level stress tends to increase. Under molar loading, cortical bone stress in the square arch decreased by 16.9% (from 90.61 MPa to 75.27 MPa) with the All-on-5 system, while implant stress in the V arch dropped by 46.26% (from 142.35 MPa to 76.5 MPa). Additionally, the cantilever effect in All-on-4 configurations resulted in higher stress on the prosthesis and implants, particularly in V arches. While the All-on-5 system provided better load distribution, the study highlights the importance of optimizing implant positioning based on mandibular anatomy. Despite limitations such as the use of static forces and standardized arch types, these findings offer valuable insights into the biomechanical performance of full-arch implant rehabilitations, supporting future clinical applications and research. Full article

Background/Objectives: Digital workflows for implant-supported full-arch restorations remain challenging. This study evaluated the accuracy and precision of digital impressions using reverse scan body (RSB) prototypes and intraoral scanners (IOSs) for rehabilitating fully edentulous patients following the All-on-4 protocol. Secondary objectives included comparing accuracy between expert clinicians and beginners, as well as desktop scanners and various RSB designs. Methods: An in vitro study was conducted using a fully edentulous mandible model with four Osstem TSIII implants. A final-year dental student and an expert clinician captured digital impressions using IOSs and desktop scanners. Four groups were analyzed: (A) original scan bodies with the IOS, (B) short RSBs with the IOS, (C) RSBs with desktop scanners (short sandblasted, long sandblasted, long coated), and (D) a control group using original scan bodies with a desktop scanner. Root mean square (RMS) values measured dimensional differences, with statistical analysis performed using the Wilcoxon signed-rank test and one-way ANOVA (α = 0.05). Results: A total of 42 scans were analyzed. No significant difference was found between expert and student for original scan bodies using the IOS (p = 0.220), while RSB prototypes showed significant differences (p = 0.008). No significant accuracy differences were noted between original scan bodies and RSBs with the IOS, but IOSs outperformed desktop scanners. Among RSBs scanned with desktop scanners, no significant differences were observed between designs. Conclusions: RSB prototypes are a viable alternative to original scan bodies for fully digital workflows in All-on-4 rehabilitations, with IOSs offering superior accuracy. However, proper training is crucial for optimizing RSB accuracy. Variations in height and coating did not impact overall accuracy. Full article

The geometry of implants plays a crucial role in the success of All-on-Four treatments for the lower jaw. This study builds upon prior research by evaluating the biomechanical performance of implant-supported prostheses in full-arch fixed dental restorations, specifically focusing on different implant lengths and connection types in cases of mild atrophic resorption of the mandible. Four groups were analyzed using finite element analysis (FEA): We utilized 13 or 18 mm posterior 17-degree tilting implants, each paired with two kinds of abutment connections. The external hexagon connection (EHC) group utilized 4 mm diameter implants, while the internal hexagon connection (IHC) group employed 4.3 mm diameter implants. A vertical force was applied to the cantilever region located at the distal side of the posterior implant. The maximum stress regions were observed in prosthetic screws and multi-unit abutments (MUAs) across all groups, with the lowest von Mises stress values noted in the bone. Stress peaks for implant screws and fixtures in the 13 mm group were 19.98% and 11.42% lower, respectively, compared to the IHC group. Similarly, in the 18 mm group, stress peaks were reduced by 33.16% and 39.70% for the EHC group compared to the IHC group. The stress levels on all components remained below the ultimate strength of the titanium alloy. For the same implant lengths, the stress in the prosthetic screw, MUAs, implant screw, and implant fixture positions was lower in the EHC group. When implant length was increased, a decrease in stress levels was observed in the implant screw and fixture of the EHC group and only in the implant screw of the IHC group. However, an increase in stress was noted in the prosthetic screw and MUAs for both groups. Full article

Background/Objectives: The insertion of dental implants using dynamic 3D navigated surgery while applying immediate function protocols for full-arch rehabilitations warrants further research. This study aimed to evaluate the outcomes of All-on-4^® rehabilitations using 3D Dynamic navigated surgery (X-Guide™). Methods: This study included 10 patients (women: 7; men: 3; average age: 59.9 years) rehabilitated with full-arch prostheses through the All-on-4^® concept, with 48 dental implants inserted using navigated surgery. The primary outcome evaluation was prosthetic/implant cumulative survival (CS), estimated using life tables. Secondary outcome evaluations were marginal bone resorption (MBR), biological complications, and mechanical complications. The evaluation parameters were measured between 1 and 3 years. Results: No patients were lost to follow-up. Two implants (4.2%) were lost in one patient (10%) with smoking habits, resulting in an implant CS rate of 95.8%. The average MBR was 0.51 mm ± 0.62 mm at the 1-year follow-up. The incidence rate of mechanical complications was 40% (n = 4 patients), all occurring in provisional prosthesis. No biological complications were registered. The patients maintained their prostheses in function throughout the follow-up of the study. Conclusions: Within the limitations of this study and based on the results, it can be concluded that the insertion of dental implants assisted by dynamic navigation for full-arch rehabilitation through the All-on-4^® concept may be a valid treatment alternative in the short-term follow-up. However, more studies are necessary to validate this treatment modality. Full article