Prosthesis, Volume 7, Issue 1 (February 2025) – 14 articles

Background/Objectives: A cam-driven hydraulic prosthetic ankle was designed to overcome the weaknesses of commercial prostheses and research prototypes, which largely fail to mimic the energy-recycling behaviour of an intact ankle, resulting in poor walking performance for lower-limb prosthesis users. Methods: This novel device exploits miniature hydraulics to capture the negative work performed during stance, prior to push-off, in a hydraulic accumulator, and return positive work during push-off for forward body propulsion. Two cams are used to replicate intact ankle torque profiles based on experimental data. The design process for the new prosthesis used a design programme, implemented in MATLAB, based on a simulation of the main components of the prosthetic ankle. Results: In this paper, we present the design programme and explain how it is used to determine the cam profiles required to replicate intact ankle torque, as well as to size the cam follower return springs. Moreover, a constraint-based preliminary design investigation is described, which was conducted to size other key components affecting the device’s size, performance, and energy efficiency. Finally, the feasible design alternatives are compared in terms of their energy losses to determine the best design with regard to minimising both energy losses and device size. Conclusions: Such a design approach not only documents the design of a particular novel prosthetic ankle, but can also provide a systematic framework for decomposing complex design challenges into a series of sub-problems, providing a more effective alternative to heuristic approaches in prosthetic design. Full article

Background/Objectives: International guidelines recommend the use of orthoses in subjects with cerebral palsy (CP), even though there is limited evidence of their effectiveness. Little is known about their effectiveness in children and adolescents with other types of neuromotor disability. Methods: The review protocol was recorded on the PROSPERO register (CRD42024509165) and conformed to the PRISMA guidelines. The inclusion criteria were any type of ankle–foot orthoses (AFOs); pediatric subjects with any non-acquired neuromotor disease; any type of outcome measure regarding gait performance; controlled studies; and those in the English language. Screening, selection, risk of bias assessment, and data extraction were performed by a group of independent researchers. Results: Fifty-seven reports were included, with most regarding CP; three involved subjects with Charcot–Marie–Tooth disease or Duchenne dystrophy. Nine were RCTs. A meta-analysis was performed for studies including subjects with CP. The meta-analysis demonstrated the effectiveness of AFOs in increasing stride length (MD −10.21 [−13.92, −6.51]), ankle dorsiflexion at IC (MD 9.66 [7.05, 12.27]), and peak ankle DF in stance (MD 5.72 [2.34, 9.09]) while reducing cadence (MD 0.13 [0.06, 0.17]) and the energy cost of walking (MD −0.02 [−0.03, −0.00]). The peak ankle power generated at push-off was significantly increased with flexible AFOs compared to rigid AFOs (MD 0.38 [0.30, 0.46]), but it decreased with both compared to walking barefoot or with shoes (MD −0.35 [−0.49, −0.22]). Evidence regarding DMD and CMT was limited but suggested opting for individualized flexible AFOs, which preserved peak ankle power generation. Conclusions: AFOs improve gait performance in CP. Flexible AFOs are preferable because they preserve the peak ankle power generated at push-off compared to rigid AFOs. Full article

Background/Objectives: “Hermes” is an ankle–foot orthosis (AFO) with negative stiffness designed to mechanically compensate the symptomatic increase in plantarflexion (PF) torque (i.e., ankle joint torque resistance to dorsiflexion, DF) in patients with spastic paresis. Methods: The effectiveness of “Hermes” was evaluated in twelve patients with chronic unilateral spastic paresis after stroke. Using a robotic ankle manipulator, stiffness at the ankle joint was assessed across three conditions: ankle without Hermes ($A$), ankle with Hermes applying no torque compensation ($A+H_{0\mathrm{\%}}$), and ankle with Hermes tuned to compensate 100% of the patients’ ankle joint stiffness ($A+H_{100\mathrm{\%}}$). Results: A significant reduction in PF torque was found with Hermes applying compensation ($A+H_{100\mathrm{\%}}$) compared to the conditions without Hermes ($A$) and with Hermes applying no compensation ($A+H_{0\mathrm{\%}}$). Furthermore, a significant reduction in positive dorsiflexion work was found with Hermes applying compensation ($A+H_{100\mathrm{\%}}$) compared to the condition with Hermes applying no compensation ($A+H_{0\mathrm{\%}}$). Hermes did not significantly contribute to additional PF torque or positive work when applying no compensation ($A+H_{0\mathrm{\%}}$). Conclusions: The reductions in PF torque achieved with Hermes are comparable to those seen with repeated ankle stretching programs and ankle robot training. Thus, Hermes is expected to assist voluntary dorsiflexion and improve walking in patients with spastic paresis. Full article

Background/Objectives: Integrated design and simulation solutions enable the manufacturing of advanced personalized orthotics that improve patients gait characteristics and balance. The success of such a rehabilitation approach is highly dependent on compliance, i.e., users wearing the orthosis consistently. Specifically, for most young children, functionality is secondary to appearance and peer perception. However, the starting point of the traditional design approach is to address functionality and then try to make the appearance more palatable to the wearer. As a result, compliance is a common issue, resulting in slow and uneven rehabilitation progress. Methods: This work proposes a method that inverts this traditional approach and devises an attractive light design that can be adapted to ensure structural soundness. Results/Conclusions: The broader framework is called the user-centered design process. The main advantage is in the flexibility of the added manufacturing approach, allowing for a personalized design that is attractive to the user, promoting higher compliance. Full article

Objectives: To evaluate the clinical performance of BioHPP^® (Biocompatible High-Performance Polymer) superstructures in full-arch implant-prosthetic rehabilitations following the Toronto-Branemark protocol, focusing on biomechanical and biological outcomes. Methods: A 70-year-old edentulous male patient underwent full-arch implant-prosthetic rehabilitation using BioHPP^® superstructures fabricated through a CAD-CAM workflow. Radiological and clinical evaluations were conducted to plan implant placement and assess outcomes after one-year of follow-up. The primary endpoints included prosthetic stability, peri-implant bone resorption, and patient-reported satisfaction. Results: The BioHPP^® superstructure demonstrated effective stress distribution, leading to minimal peri-implant bone resorption and improved implant stability. Clinical evaluations showed excellent prosthetic fit and functionality, with no complications during the observation period. Radiological analyses confirmed the absence of prosthetic misfits, while patient-reported outcomes indicated high levels of comfort and aesthetic satisfaction. Conclusions: BioHPP^® superstructures offer a promising alternative to traditional materials for full-arch implant-prosthetic rehabilitations, providing significant biomechanical and aesthetic advantages. These findings suggest that BioHPP^® may enhance clinical outcomes, though further research with larger cohorts and longer follow-up periods is required to validate its long-term reliability. Full article

Background/Objectives: Primary stability is an important factor for dental implant success, and a high insertion torque (IT) is recommended in cases where an immediate load is required or desired. At the same time, some authors have claimed that it can interfere with bone-to-implant healing. This study aimed to compare the survival rates of implants inserted with different torques in full-arch cases, with or without immediate load, with up to 2-year follow-up. Methods: This study included subjects who required full-arch rehabilitation with implants. All cases were planned for the placement of four implants on each arch and were divided into groups according to the IT and had implant stability quotient (ISQ) measurements taken periodically for up to 2 years. Results: No implant was lost during this period, and no significant differences in peri-implant bone loss were observed. The paired t-test was performed to determine the association between ISQ and IT. Conclusions: The results suggest that initial torques higher than 75 Ncm may not be harmful to the stability of implants placed for full-arch rehabilitation, at least during the study period. Further clinical studies with longer follow-up periods are necessary to confirm these results. Full article

Background/Objectives: This study investigates stress distribution in cancellous bone during pilot drilling for dental implants using the Cowper–Symonds model. Understanding the biomechanical effects of drilling parameters on bone health is essential for optimizing implant stability and longevity. Methods: A finite element analysis (FEA) approach was employed to simulate the pilot drilling process in cancellous bone. A three-dimensional jawbone model was developed from CT scan data, processed using 3D Slicer, and refined with CAD tools. The drilling simulation incorporated a rigid pilot drill and flexible cancellous bone, utilizing explicit dynamic methods. Stress distribution was evaluated for drilling depths ranging from 6 mm to 16 mm, with mesh density and strain rate effects considered to ensure accuracy. Results: The results showed an increase in stress levels with drilling depth, with maximum stress recorded at 16 mm. Initial contact stress was 17.3 MPa, rising to 228.9 MPa at deeper penetration due to increased interaction between the drill and bone. Stress distribution patterns emphasized the critical role of drilling depth and design parameters in mitigating bone damage. Conclusions: This study highlights the importance of optimized drilling protocols and pilot drill design to reduce stress and preserve bone integrity. The findings provide valuable insights into improving implant procedures and demonstrate the utility of FEA as a robust tool for evaluating biomechanical impacts during implant placement. Future research should incorporate cortical bone and thermal effects for a comprehensive analysis. Full article

Background: With the growing demand for sustainable dental practices, chitosan has evolved as an eco-friendly disinfectant for polyether impressions. Objectives: The present study investigated the disinfectant efficacy of chitosan on the dimensional accuracy of polyether (PE) impression material. Methods: A total of 63 polyether impressions (Impregum^TM, Penta^TM, 3M ESPE, Boca Raton, FL, USA) were prepared from the master 3D-printed model, each consisting of a single unit abutment facing two units’ abutments. Three groups of these subjects were used, while each group comprised 21 impressions, respectively. Group 1 is used as a control group and is not subjected to chemical disinfection. Group 2 is spraying group, in which the PE impressions were sprayed with 0.5% chitosan with a high molecular weight. Group 3 is the immersion group, in which the impression was immersed for 15 min in 0.5% chitosan with a high molecular weight. The data collected were analyzed using SPSS 28.0 and the difference in dimensional accuracy between the groups was measured using a one-way ANOVA. Results: Both the intra-and inter-abutment measurements (MD and OG) showed no statistically significant differences in the dimensional changes between the control and the study groups, while the cross-arch distance showed a statistically significant difference in the dimensional change between control and immersion group, p = 0.000. Conclusions: While chitosan disinfection induced slight dimensional changes in polyether impressions, these alterations remained within clinically acceptable limits. The spray application method appeared to be preferable to immersion, as it resulted in less pronounced dimensional changes. Full article

Background: Computer-aided design/computer-aided manufacturing (CAD-CAM) technology is becoming a more significant means of providing prosthodontic treatment due to its impact on clinical performance and patient outcomes. It has been integrated into dental education to allow students to experience digital work-flows. Despite these advancements, many dental students still lack sufficient knowledge of CAD-CAM technologies. Methods: A cross-sectional survey was conducted at the College of Dentistry, Imam Abdulrahman Bin Faisal University. Based on previous studies, a validated questionnaire was distributed to undergraduate dental students and interns. The questionnaire assessed their knowledge and attitudes toward CAD-CAM technology in prosthetic dentistry. Statistical analysis software utilized in the study was the Statistical Package for Social Sciences (SPSS). Results: The responses were analyzed using descriptive statistics, and a chi-square test was used to study the association between knowledge and practice and the study year level. A total of 170 students participated in the study, with a mean age of 22.2 (±2.5) years. The proportion of female participants was 65.9% and the proportion of males was 34.1%. Knowledge varied across academic levels, with fourth- and fifth-year students demonstrating greater theoretical knowledge, while sixth-year students and interns showed more practical experience. Only 3 of the 18 knowledge-related questions received a correct response rate above 70%. Most participants (86%) reported acquiring knowledge from undergraduate courses, and 88% expressed interest in further training. Conclusions: CAD-CAM technology was most commonly practiced for fixed prostheses, and intraoral scanning was the most frequently used digital work-flow. The study highlights the need to improve CAD-CAM education. While lower-level students displayed solid theoretical knowledge, advanced students benefitted from more practical exposure. Increasing hands-on experience and access to digital equipment is essential for preparing students to meet the demands of modern digitalized dentistry. Full article

This study aims to analyze the precision and amount of dental tissue removed during overlay preparation by experienced and less experienced operators, with and without magnification systems. Methods: Sixty-four first upper molar Frasaco Typodonts were divided into four groups: experienced operators with magnification (Group 3, EXP+LOU), experienced operators without magnification (Group 1, EXP), dental students with magnification (Group 4, STU+LOU), and dental students without magnification (Group 2, STU). Preparations including an occlusal reduction of 1.5 mm and an interproximal box of 1 mm width. The prepared teeth were scanned and analyzed using reverse engineering software (Geomagic Control X, Oqton, San Francisco, CA, USA) to evaluate preparation accuracy, dental substance removal, and comparison to a control unprepared tooth. Results: The analysis showed that the average reduction was 32.19%. Group 4 (STU+LOU) showed significantly improved accuracy with magnification compared to Group 2 (STU). Group 3 (EXP+LOU) achieved the best result with an average reduction of 23.96%, while Group 2 (STU) had the worst result with 41.28%. Conclusions: Conservative indirect restorations, such as overlays, effectively preserve dental tissue. Operator experience and magnification systems are crucial for preparation accuracy. Magnification improves precision for less experienced operators, reducing tooth volume loss by 9.1%, and enhances cavity design accuracy, ensuring a better restoration fit and minimizing the marginal gap. Full article

Background: Chronic lumbopelvic pain is often linked to sacroiliac joint dysfunction, where the joint’s complex structure and biomechanics complicate diagnosis and treatment. Variability in load distribution and ligament stabilization within the pelvic ring further contributes to challenges in managing this condition. This study aims to develop a finite element model of the “lumbar spine–sacrum–pelvis” system to analyze the effects of lumbar lordosis, pelvic tilt, and asymmetrical articular gaps on stress and strain in the sacroiliac joint. Methods: A three-dimensional model was constructed using CT and MRI data, including key stabilizing ligaments. Sacral slope angles of 30°, 60°, and 85° were used to simulate varying lordosis, while pelvic tilt was introduced through a 6° lateral rotation. Results: The analysis revealed that sacral slope, ligament integrity, and joint symmetry significantly influence stress distribution. Hyperlordosis led to critical stress levels in interosseous and iliolumbar ligaments, exceeding failure thresholds. Asymmetrical gaps and pelvic tilt further altered the sacral rotation axis, increasing stress on sacroiliac joint ligaments. Conclusions: These findings highlight the importance of maintaining sacroiliac joint symmetry and lumbar–pelvic alignment to minimize stress on stabilizing ligaments, suggesting that treatment should focus on restoring alignment and joint symmetry. Full article

Background: Prostheses are becoming more advanced and biomimetic with time, providing additional capabilities to their users. However, prosthetic sensation lags far behind its natural limb counterpart, limiting the use of sensory feedback in prosthetic motion planning and execution. Without actionable sensation, prostheses may never meet the functional requirements to match biological performance. Methods: We propose an approach for upper limb prosthetic grasp security feedback, delivered to the wearer through direct nerve stimulation proportional to the likelihood of objects slipping from grasp. This proportional feedback is based on a linear regression of the sensors embedded in a prosthetic hand to predict slip before it occurs. Four participants with transhumeral amputation performed pulling tasks with their prosthetic hand grasping an object at predetermined grip forces, attempting to pull the object with as much force as possible without slip. These trials were performed with two different prediction notification paradigms. Results: At lower grasp forces, where slip was more likely, a strong, single impulse notification of impending slip reduced the incidence of object slip by a median of 32%, but the maximum achieved pull forces did not change. At higher grasp forces, where slip was less likely, the maximum achieved pull forces increased by a median of 19% across participants when provided with a stimulation strength inversely proportional to the grasp security, but slip incidence was unchanged. Conclusions: These results suggest that this approach may be effective in recreating a lost sense of grip stability in the missing limb that can be incorporated into motor planning and ultimately prevent unanticipated object slips. Full article

(1) Background: The use of tumor megaprostheses faces challenges, but the published series are typically small and offer limited solutions. Our aim was to compile a large series; describe patient profiles and surgical techniques; analyze prosthetic survival identifying factors affecting survival; and provide a basis for future subanalyses. (2) Methods: This is a retrospective observational multicenter study that included patients with a tumor megaprosthesis in any anatomical location. Demographic, etiologic, and surgical variables were analyzed. Data on complications and survival were also collected. (3) Results: Our series includes a total of 816 prostheses (585 primary, 181 revision, and 50 second revision). The patients’ mean age was 44.2 ± 20.8 years. Primary surgeries were performed on the femur (n = 404; 69.1%), tibia (n = 79; 13.5%), humerus (n = 74; 12.6%), pelvis (n = 20; 3.4%), and scapula (n = 4; 0.7%). Survival following primary surgery was 73.3% at 10 years. No statistically significant differences were found with respect to survival from primary surgery between males and females (p = 0.194), between the different etiologies (p = 0.540), or between the lower and the upper limb (p = 0.618). In contrast, statistically significant survival differences were found when the type of fixation was analyzed (p < 0.001). (4) Conclusions: This study analyzed one of the largest series of patients treated with tumor megaprostheses, demonstrating their acceptable survival and validating them as a treatment option for bone tumors. Full article

Objectives: Among modern metal-free materials, zirconia, a high-performance ceramic material that can only be manufactured through CAM procedures, has certainly exponentially gained popularity thanks to its mechanical strength, biocompatibility, esthetic, and versatility. However, one of the main debates that has been raised in relation to zirconia is its usage as an adhesive material. The present case report describes the clinical outcome of a multidisciplinary case finalized with adhesive minimally invasive zirconia veneers for the treatment of discolored teeth after a 24-month follow-up. Methods: A 19-year-old female patient with discolored upper frontal teeth (first premolar to first premolar) negatively affecting her self-esteem and social life was visited by a prosthodontic specialist. The treatment plan included orthodontic treatment, soft and hard tissue management through surgical procedures, and, lastly, minimally invasive adhesive zirconia veneers. The zirconia veneers bonding was performed under a rubber dam by conditioning the dental substrate by sandblasting the enamel with 40-micron aluminum oxide, etching with orthophosphoric acid 37%, and using a proper adhesive system. Monolithic zirconia restorations were sandblasted with 70-micron aluminum oxide at 0.2 MPa, then cleaned with a specific cleaner, and treated with a primer. Results: At the last follow-up (24 months), neither biological nor mechanical complications were observed. The patient anecdotally reported being very satisfied with the functional and esthetic results obtained. Therefore, the case was considered successful. Conclusions: Within the limitations of the present case report, the reported case on the use of minimally invasive resin-bonded zirconia veneers for the treatment of discolored teeth showed excellent outcomes after a 24-month follow-up. The use of zirconia as an adhesive material seems to be emerging. However, more clinical studies are required to validate the procedure. Full article