Prosthesis, Volume 6, Issue 4 (August 2024) – 20 articles

Purpose: This study evaluates and compares the effect of printing layer thickness (LT) and post-polymerization time (PPT) on the flexural strength and hardness of three 3D-printed resins after thermal aging. Methods: A bar shape (64 × 10 × 3.3 mm) and a disc shape (15 × 2 mm) were designed for flexural strength and hardness testing, respectively. ASIGA, NextDent, and FormLabs 3D-printed resins were used to print specimens with different LTs (25 µm, 50 µm, and 100 µm). Each thickness group was post-polymerized (PP) for different times (15, 30, 60, and 90 min). All printed specimens were thermally cycled (5000 cycles) and then tested, measuring the flexural strength and hardness using a universal testing machine and Vickers hardness tester, respectively. The data were analyzed using ANOVA and a post hoc Tukey’s test (α = 0.05). Results: A PPT of 90 min showed the highest flexural strength. In comparisons of the LTs, 25 µm and 50 µm significantly increased flexural strength compared with 100 µm, which showed the lowest value for each PPT. The hardness increased as the PPT increased for all materials. In our LT comparison, 25 µm and 50 µm significantly increased the hardness for NextDent and FormLabs resins, while only 25 µm showed high hardness compared with 50 µm and 100 µm for ASIGA. Conclusion: Both parameters (LT and PPT) impact flexural strength and hardness. Increased PPT with the minimum LT is recommended. Full article

Purpose: This in vitro study aimed to evaluate and compare the physical and antimicrobial properties of provisional resin modified with two different nanoparticles, namely, silicon dioxide (nano-SiO₂) and titanium dioxide (nano-TiO₂). Methods: A commonly used commercially available polymethyl methacrylate (PMMA) provisional resin (Unifast III; GC Corp) was modified with nano-SiO₂ and nano-TiO₂ at different concentrations (1% wt. and 2.5% wt. respectively), while one unmodified group was used as a control. Rectangular specimens (60 × 10 × 3.3 mm) for strength (MPa) and elastic modulus, and square specimens (10 × 10 × 3.4 mm) for surface roughness (Ra, µm), hardness (VHN), and Candida albicans adhesion (colony forming unit, CFU/mL) were prepared and grouped into five groups (n = 10) according to (nanoparticles) NPs type and concentration. After polymerization, the specimens were finished and polished and then subjected to thermal cycling (5000 cycles). Analysis of variance and post-hoc Tukey test were used for data analysis (α = 0.05). The scanning electron microscope (SEM) was used for fracture surface analysis and C. albicans count. Results: The addition of 1% nano-SiO₂ significantly increased the flexural strength, and 1% nano-SiO₂ contributed to the highest flexural strength value, while 2.5% nano-SiO₂ and nano-TiO₂ showed non-significant increases (p > 0.05). The elastic modulus increased significantly for both NPs. Among the NP-modified groups, the nano-SiO₂ groups showed an increased elastic modulus compared to the nano-TiO₂ groups. The hardness significantly increased with NPs addition with no significant differences between NPs-modified groups. Surface roughness increased with 2.5% nano-TiO₂ addition, while 1% nano-TiO₂ and nano-SiO₂ showed non-significant differences. Nano-SiO₂ and nano-TiO₂ significantly decreased C. albicans adhesion, and nano-TiO₂ groups were significantly superior in their antimicrobial effect compared with nano-SiO₂. Conclusions: Low nano-SiO₂ addition increased the flexural strength of provisional resin. The addition of NPs increased elastic modulus and hardness and decreased the C. albicans adhesion to provisional resin. Nano-SiO₂ did not alter the surface roughness, while 2.5% of nano-TiO₂ increased the surface roughness. Full article

Photogrammetry (PG) appeared as an alternative for multiple implant impressions. Stereo-photogrammetry is a more sophisticated alternative to PG, which estimates the 3D coordinates of the points of an object, making the process quicker and more precise. A search in PubMed MEDLINE, PMC, and Google Scholar was conducted to find systematic reviews published in the last 10 years. The PICdental^® camera (IDITEC NORTH WEST, SL; Torrelodones, Spain) is a stereocamera that records implant positions in the mouth by means of photogrammetry with the objective of registering and obtaining a viable, reliable, and direct digital impression of the positions of the multiple implants. The use of photogrammetry via PiCdental^® camera as an alternative to digital impression for multiple implants is an easy and trustworthy technique that permits an adequate fit without prosthetic complications. Full article

After tooth loss, particularly in the posterior maxilla, the alveolar ridges undergo bone resorption. Therefore, ensuring the appropriate quantity and quality of alveolar bone is crucial for accurate implant positioning and achieving optimal esthetic and functional results. This study aimed to evaluate biomechanical parameters (insertion torque: IT, removal torque: RT, and implant stability quotient: ISQ) of distinct truncated cone implant designs (Sinus-plant and SLC) on polyurethane blocks simulating type D3 and D4 bone. SLC implants exhibited significantly higher IT, RT, and ISQ values compared to Sinus-plant implants, except in the 10 pounds per cubic foot (PCF) density block with a cortical layer for the IT (24.01 ± 0.91 vs. 23.89 ± 1.66 Ncm). The IT values for SLC implants ranged from 13.95 ± 0.19 Ncm in the lowest density block to 37.94 ± 0.45 Ncm in the highest density block, consistently providing significantly higher primary stability with an ISQ of approximately 70 in the highest density block. Despite lower ISQ in the lowest density block (48.60 ± 0.52 and 48.80 ± 0.42 in buccolingual and mesiodistal directions), it was deemed acceptable considering the inadequate bone densities in the maxillary region. These findings on SLC suggest potential clinical advantages, including reduced procedure duration and costs, improved stability, and the possibility of immediate implant placement following sinus augmentation, thereby streamlining the rehabilitation process. Full article

Robotic-assisted hip and knee arthroplasty represents significant advancements in orthopedic surgery. Artificial intelligence (AI)-driven chatbots, such as ChatGPT, could play a significant role in healthcare education. This study aims to evaluate the quality of responses provided by ChatGPT to the top 20 questions concerning robotic-assisted hip and knee arthroplasty. We have asked ChatGPT to select the top 20 questions on Google concerning robotic hip and knee arthroplasty and to provide a detailed answer to each of them. The accuracy and completeness of the information provided were examined by three orthopedic surgeons with scientific and clinical experience in hip- and knee-replacement surgery. The accuracy was assessed through a 5-point Likert scale (from 1—completely incorrect to 5—correct); the completeness through a 4-point Likert scale (from 0—comprehensiveness not assessable for completely incorrect answers to 3—exhaustive information) on two different occasions to ensure the consistency of the assessment. Our analysis reveals that ChatGPT provides a relatively high degree of accuracy; moreover, the explanations can be considered satisfying, especially for factual questions. The findings suggest that ChatGPT can serve as a valuable initial resource for general information on robotic hip and knee arthroplasty but the integration with human expertise remains essential. Full article

This study aims to assess the impact of occlusal loadings on peri-implant bone loss by measuring the cantilever of each implant and evaluating the occlusal pattern using PRESCALE^® and to examine the relationship between occlusal overload and peri-implant bone loss, including marginal bone loss (MBL) and biomechanical factors, in a sample of 41 patients with a total of 135 implants. In addition, this study examines the influence of occlusal overload among patient groups with no marginal bone loss, unilateral bone loss, and bilateral bone loss. The PRESCALE^® quantifies the occlusal area and load along the dental arch. The analysis of variance (ANOVA) was used for comparing quantitative variables between groups and the Pearson correlation coefficient (r) was applied to analyze linear relationships between quantitative variables. The results of occlusal distribution and pressure range were presented using the PRESCALE^®. It was found that the mesial cantilever was statistically significantly greater (p < 0.05) for the bilateral bone loss group. Additionally, MBL was significantly proportional to occlusal loading in the left anterior sector (r = 0.47; p < 0.01) and to follow-up time (r = 0.29; p < 0.01), though it was also proportional to implant diameter and length (r = 0.27 and r = 0.20). The presence of a wider cantilever and excess occlusal loading appears to be associated with increased bone loss. Full article

This study compares the clinical performances of two lithium disilicate (Initial LiSi press vs. Initial LiSi Block, GC Corp.) and a 3D printed resin (Temp Print, GC Corp.) partial crown using modified United States Public Health Service (USPHS) evaluation criteria and survival rates after one year of clinical service. Eighty-nine partial adhesive restorations on posterior teeth were realized using different materials: Group 1 used Initial LiSi press, Group 2 used Initial LiSi Block, and Group 3 used Temp Print. An analog workflow was used to realize the restoration of Group 1, while a fully digital workflow was used for Groups 2 and 3. The modified USPHS parameters, together with periodontal parameters, were collected at baseline and at the one-year recall. Contingency tables to assess for significant differences of success over time in each group were used. All modified USPHS parameters showed Alpha or Bravo; no Charlie was recorded. No statistically significant difference emerged between the three groups in any of the assessed variables (p > 0.05). All modified USPHS scores were compatible with the outcome of clinical success, no restoration was replaced or repaired, and the survival rate was 100% at the one-year recall. No difference was found between the traditional and digital workflows used to fabricate the restorations. Full article

Background: Dental implant rehabilitation has significantly advanced prosthodontics by providing a reliable, long-lasting solution for missing teeth. This systematic review compares the clinical, technical, and biological outcomes of cemented versus screw-retained single dental implant restorations based on randomized clinical trials (RCTs). Materials and Methods: This review included recent human and in vitro studies focusing on the keywords “cemented vs. screw-retained” and “dental implant”. Eight studies met the inclusion criteria, which investigated parameters, including implant survival rate, bleeding on probing (BOP), probing depth, plaque index, marginal bone loss (MBL), cytokine concentrations, mechanical complications, esthetic outcomes, patient satisfaction, treatment time, and technical failures. Results: The primary outcomes, BOP and MBL, did not statistically differ between cemented and screw-retained implants (p-values for MBL and BOP are 0.5813 and 0.8093, respectively). The reviewed studies, including RCTs, split-mouth studies, and clinical evaluations, demonstrated comparable clinical, technical, and biological outcomes between the two restoration methods. Conclusions: Screw-retained and cemented dental implant restorations exhibit similar clinical, technical, and biological outcomes. Screw-retained restorations offer advantages such as retrievability, ease of repair, and predictable passive fit, while cemented restorations provide superior esthetics. The risk of peri-implant complications due to residual cement in cemented restorations must be considered. Future research should explore long-term stability and the impact of different prosthetic protocols on peri-implant health. Full article

Background: Total knee arthroplasty (TKA) for poliomyelitis patients is controversial due to its higher complication rate compared with that of TKA for osteoarthritis. In this study we evaluated the results, at a minimum of 10 years, of a consecutive series of third-generation rotating hinge total knee arthroplasties (RHKs) in patients affected by poliomyelitis. Methods: We conducted a retrospective analysis of 14 patients (15 TKA) performed between January 2000 and October 2021 that underwent a third-generation rotating hinge arthroplasty (Nex Gen RHK Zimmer). The clinical results using the American Knee Society Score (AKSS) were evaluated at an average follow-up of 154 months (min 120–max 216 months). Result: Of the 15 cases, 2 were lost at follow-up and 1 was excluded by the final evaluation due to infection. Of the remaining 12 cases at the final follow-up, the average AKKS clinical score improved from 30.08 points preoperatively, to 78.83 points postoperatively, while the average AKKS function score improved from 29.17 points to 56.25 points. We report only one intraoperative complication consisting of a femoral fracture at the tip of the stem, and a case of patellar fracture occurred 3 months after the index procedure. The presence of radiolucent lines was sporadic, while radiosclerotic lines were commonly visible around the stem extension, predominantly at the tip. Conclusions: The third generation of rotating hinge knee replacement has proved to be effective in polio patients, improving clinical and functional scores, and no cases of mechanical failure occurred. Full article

Despite their emerging use, the in vivo behaviour of dual-mobility (DM) total hip replacements (THRs) is not well understood. Therefore, the purpose of this study was to assess the articulating surfaces of 20 early-retrieved DM polyethylene liners (mean length of implantation 20.0 ± 18.8 months) for damage to improve the current understanding of their in vivo functional mechanisms. The internal and external surfaces of each liner were visually and geometrically assessed, and the material composition of embedded debris particles were further characterized. Scratching and pitting were the most common modes of damage identified on either surface, and a high incidence of burnishing (50%) and embedded debris (65%) were observed on the internal and external surfaces, respectively. Embedded debris particles were commonly titanium- or iron-based, although other materials such as cobalt-chrome and tantalum were also identified. The geometric assessment demonstrated highly variable damage patterns across the liners, with the internal surfaces commonly presenting with crescent-shaped, circumferential, or circular regions of penetration whilst the external surfaces commonly presented with regions of deep pitting or gouging. This study demonstrates that DM-THRs primarily articulate at the head/liner junction, and that polyethylene liners are capable of rotating about the femoral neck axis, although the extent of this may be limited in some cases. Additionally, this study suggests that intra-prosthetic dislocation and edge loading may remain pertinent failure mechanisms of DM implants despite the advent of highly crosslinked polyethylene and design features, thus highlighting the need for enhanced monitoring of these devices. Full article

Dental rehabilitation with implants is a clinical reality in clinical practice. The Interproximal Contact Loss (ICL) between implant-supported prostheses adjacent to natural teeth is a relatively common occurrence. This systematic review and meta-analysis aims to evaluate the possible clinical effects of the periodontium regarding the ICL between teeth and implanted-supported prostheses. We also identified the main ICL assessment tools described in the literature. This study was registered on the PROSPERO (CRD42023446235), was based on the PICO strategy, and followed the PRISMA guidelines. An electronic search was carried out in the PubMed, B-on, Google Scholar, and Web of Science databases without setting a time limit for publications. Only systematic reviews and comparative clinical trials were included and analyzed. Nineteen publications were eligible for meta-analysis, with thirteen retrospective and six prospective clinical trials. A total of 2047 patients and 7319 prostheses in function were evaluated, and ICL was found in 51% with a confidence interval of 0.40 to 0.61. As ICL assessment tools, dental floss was used in 65%, matrices were used in 30%, and X-ray images were used in 5% of cases. The clinical follow-up ranged from 1 to 21 years, with 50% between 1 and 3 years, 25% between 3 and 10 years, and 25% between 10 and 21 years. ICL was found to occur more frequently in the mandible. No statistically significant difference existed between the anterior (55%) and posterior (47%) oral regions. On the mesial surface, ICL ranged from 13% to 81.4%, possibly due to the different follow-up periods and the diversity of methods used in the assessment. No differences were found for ICL between single or multiple implanted-supported prostheses. Food impaction was the most common effect of ICL and was more prevalent on the implant-supported prosthesis’s mesial surface in the mandible’s posterior region. There was evidence of peri-implant mucositis but without progression to peri-implantitis, and the form of retention or the number of elements was not relevant. Full article

Hip replacement surgery is increasingly being performed on older patients, raising the risk of periprosthetic proximal femur fractures (PPFFs). While the impact of surgery timing on mortality in proximal femoral fractures is established, its effect on PPFFs remains unclear. This study aims to examine the correlation between surgery timing and mortality in PPFF patients. In a historical cohort study, we analyzed data from 79 PPFF patients treated from 2012 to 2022. Patients were categorized by surgery timing (≤48 h, 32 patients vs. >48 h, 47 patients). Outcomes and mortality rates were compared. No significant difference in mortality was observed between patients undergoing early (<48 h) and delayed (>48 h) surgery at 30 days and 1 year. Factors such as age (p = 0.154), gender (p = 0.058), ASA score (p = 0.893), Vancouver classification (p = 0.577), and surgery type (implant revision p = 0.691, OR = 0.667) did not affect 30-day mortality. However, 1-year mortality was influenced by gender (male p = 0.045) and age (p = 0.004), but not by other variables (Vancouver classification p = 0.443, implant revision p = 0.196). These findings indicate no association between surgery timing and mortality in PPFF patients, suggesting that other factors may influence outcomes. Further research is needed to optimize PPFF management. Full article

The main objectives of the present prospective clinical study were to evaluate the survival and success rates of implant-supported zirconia single crowns fabricated with a full digital workflow for the rehabilitation of mono- and bilateral agenesis of maxillary lateral incisors after 2 years of clinical function; biological and technical parameters affecting the prosthetic restorations were recorded, as well as the patient-satisfaction score. Twenty-two patients showing mono- or bilateral agenesis of the maxillary lateral incisors were included in this study, and a total of 30 narrow-diameter implants were inserted. Thirty screw-retained monolithic cubic zirconia single crowns with internal connections were fabricated. Objective outcome evaluations were performed by means of the Functional Implant Prosthodontic Score, whereas the patient-satisfaction score was evaluated using Visual Analog Scales. Descriptive statistics were performed and the Kaplan–Meier analysis was run to analyze time-to-event data. After 2 years of clinical function, the overall FIPS found in the present study was 9.2, whereas the average patient-satisfaction score was 8.7. The Kaplan–Meier analysis at the 2-year follow-up reported a cumulative survival rate of 100% and a cumulative success rate of 93.3%. The implant-prosthetic rehabilitation with a full digital workflow proved to be an effective and reliable procedure for the functional and aesthetic treatment of the agenesis of maxillary lateral incisors in the short-term. Clinical investigations with wider sample populations and longer observational follow-ups could be useful to validate, in the long-term, the clinical outcomes of the present prospective clinical study. Full article

Background: Advanced manufacturing techniques, such as three-dimensional (3D) printing, use digital models from computer-aided design to produce 3D objects. They are frequently employed in different areas of dentistry, such as orthodontics, oral implantology, and prosthodontics. Purpose: The aim of this review was to provide a comprehensive overview of 3D-printing technology for denture bases and explore the influence of incorporating different fillers into 3D-printed denture base resins on their physical, mechanical, and biological characteristics. Methods: Relevant studies were identified by searching papers published between 2010 and 2023 in several online databases, such as Scopus, PubMed, Cochrane library, and Google Scholar. The main inclusion criteria used during the search was identifying the papers which added nanoparticles in the resin as an agent to bring different functional characteristics within the 3D-printed denture base resin. Furthermore, even though the search criteria were set for finding papers from the past 10 years, development in this field has accelerated in the past 4–5 years. Findings: Various fillers have exhibited promising results in terms of their ability to improve the functional properties of the 3D-printed denture base resins. However, such improvements come at a higher cost with careful resin preparation when considering the filler particles, the fabrication complexities and the extensive post-processing that is required. Conclusions: The use of 3D-printing approaches and fillers to fabricate dentures is associated with significant benefits in terms of imparting functional properties, consistency in fabrication and opportunities for innovation. However, further research is required to acquire a better understanding of the holistic, long-term performance of various filler materials, concentrations, their clinical relevance and particularly the potential health risks from the fillers. Full article

Background: Complete dentures should withstand occlusal forces and wear. However, over time, dentures can suffer fatigue and develop cracks, chipping, and fractures. Conventional methods for the fabrication of complete dentures involve injection molding, thermal curing, and the use of microwaves with polymethyl methacrylate (PMMA)-based materials. These methods have served well for many years. More recently, the incorporation of computer-aided design and computer-aided manufacturing (CAD/CAM) to fabricate complete dentures has been shown to enhance the dentures’ mechanical properties, including resistance to wear and impact strength. This study aims to investigate the mechanical properties and fracture types of CAD/CAM denture base materials (both milled and printed) as compared to a novel proprietary method that embeds a 3D-printed framework within PMMA-milled blocks. The null hypothesis is that incorporating a 3D-printed framework does not affect the mechanical properties of milled PMMA blocks. Methods: Three groups of bars were fabricated using CAD/CAM methods: printed (P), milled (M), and milled with a 3D-printed metallic framework reinforcement (M + F). A three-point bending test evaluated deformation, followed by an impact fracture test for fracture toughness. A descriptive fractographic analysis assessed the fracture characteristics. A statistical analysis using a paired t-test compared the differences between the groups. Results: The P group showed more elastic deformation than the M and M + F groups (p < 0.05). The M + F group achieved a higher fracture toughness as compared to the M and P groups (p < 0.05). Conclusions: Within the limitations of this experimental study, the null hypothesis can be rejected. Milled samples with an embedded 3D-printed titanium framework possess higher resistance to impact than milled samples without frameworks, and printed samples and milled samples with embedded 3d-printed titanium frameworks present increased flexural strength and lower elastic deformation as compared to milled samples without frameworks and printed samples. Full article

Registries have significant roles in assessing the comparative performance of devices. Ideally, early identification of outliers should use a time-to-event outcome while reducing the confounding effects of other components in the device and patient characteristics. Machine learning (ML), which contains self-learning algorithms, is one approach to consider many variables simultaneously to reduce the impact of confounding. The principal objective of this study was to investigate the effectiveness of using either random survival forest (RSF) or regularised/unregularised Cox regression to account for patient and associated device confounding factors in comparison with current standard techniques. This study evaluated RSF and regularised/unregularised Cox regression using data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) to detect outlier devices among 213 individual primary total hip components performed in 163,356 primary procedures from 1 January 2015 to the end of 2019. Device components and patient characteristics were the inputs, and time to first revision surgery was the primary outcome treated as a censored case for death. The effectiveness of the ML approaches was assessed based on the ability to detect the outliers identified by the AOANJRR standard approach. In the study cohort, the standardised AOANJRR approach identified three acetabular components and seven femoral stems as outliers. The ML approaches identified some but not all the outliers detected by the AOANJRR. Both the methods identified three of the same femoral stems, and the RSF identified the other five components, including two of the same acetabular cups and three of the same femoral stems. In addition, both the RSF and Cox techniques detected a number of additional device components that were not previously identified by the standard approach. The results showed that ML may be able to offer a supplementary approach to enhance the early identification of outlier devices. Random survival forest was a more comparable technique to the AOANJRR standard than the Cox regression, but further studies are required to better understand the potential of ML to improve the early identification of outliers. Full article

The ankle joint is pivotal in prosthetic feet, especially in Energy-Storing-and-Releasing feet, favoured by individuals with moderate to high mobility (K3/K4) due to their energy efficiency and simple construction. ESR feet, mainly designed for sagittal-plane motion, often exhibit high stiffness in other planes, leading to difficulties in adapting to varied ground conditions, potentially causing discomfort or pain. This study aims to present a systematic methodology for modifying the ankle joint’s stiffness properties across its three motion planes, tailored to individual user preferences, and to decouple the sagittal-plane behaviour from the frontal and transverse ones. To integrate the multi-axial ankle inside the MyFlex-η, the designing of experiments using finite element analysis was conducted to explore the impact of geometric parameters on the joint’s properties with respect to design constraints and to reach the defined stiffness targets on the three ankle’s motion planes. A prototype of the multi-axial ankle joint was then manufactured and tested under FEA-derived load conditions to validate the final configuration chosen. Composite elastic elements and complementary parts of the MyFlex-η, incorporating the multi-axial ankle joint, were developed, and the prosthesis was biomechanically tested according to lower limb prosthesis ISO standards and guidelines from literature and the American Orthotic and Prosthetic Association (AOPA). Experimental tests showed strong alignment with numerical predictions. Moreover, implementing the multi-axial ankle significantly increased frontal-plane compliance by 414% with respect to the same prosthesis with only one degree of freedom on the sagittal plane without affecting the main plane of locomotion performance. Full article