Angular Deviation Research Articles

Clinical study of immediate implant placement in posterior maxillary region assisted by dynamic real-time navigation: A randomized controlled trial

ObjectiveTo evaluate the accuracy of the implant accuracy and clinical effect of navigation-assisted immediate implant placement (IIP) in the posterior maxillary tooth region. MethodsThis study included 60 patients with 96 implants undergoing IIP in the posterior maxillary region from January 2021 to December 2022, stratified into dynamic navigation and freehand implant groups. All clinical indicators, including initial stability, implant deviation (entry point deviation, end point deviation, depth deviation and angle deviation), marginal bone resorption and implant success rate, were systematically recorded. ResultsAll implants were successfully placed with an average torque of (24.38 ± 1.84)N.cm. The mean entry point deviation, apex point deviation and angular deviation in the navigation group were significantly smaller than that of the freehand group (P < 0.05). Marginal bone resorption was significantly less in the navigated group than in the freehand group (P < 0.05). All dental implants were considered an operational success and the mean follow-up time was (27.8 ± 8.4) months. ConclusionThe application of dynamic navigation-assisted immediate implant placement in the maxillary posterior region can achieve good implant accuracy and satisfactory clinical results.

Effect of wall thickness on shape accuracy of hollow zirconia artificial teeth fabricated by a 3D printer.

This study aimed to analyze how the wall thickness of 3D-printed hollow zirconia teeth affects shape accuracy. Datasets with measurement points were created for different artificial teeth resembling the mandibular right first molar (Geomagic Design X, 3D Systems). Reference distances were 9.8 mm for mesio-distal direction (M-D), 10.9 mm for bucco-lingual direction (B-L), 7.0 mm for MB-BB and DB-BB, and 4.5 mm for ML-LB and DL-LB. The outer geometry was identical for all artificial teeth with wall thicknesses of 0.30, 0.50, 0.75, and 1.00 mm. Twenty zirconia teeth were fabricated using a 3D printer (CeraFab 7500 Dental, Lithoz) for each group and sintered before support removal. After performing analog distance measurements using a micrometer screw, the digital distance measurements and angular deviations between measurement points on 3D scans were analyzed. Possible effects were investigated using nonparametric ANOVA, followed by Tukey's honest significant difference (HSD) test for multiple comparisons. The shape accuracy was acceptable for artificial teeth with wall thicknesses of ≥0.5 mm. The largest distance deviation was observed for a wall thickness of 0.3 mm. In particular, DB-BB showed a median deviation of >56.2 µm, which is significantly larger than that for other test groups, ranging from 7.4-9.5 µm (P < 0.05). In most cases, angular deviations were the largest for teeth with 0.3-mm wall thickness (11.6°) and remained below 5.0° for the other test groups. Acceptable accuracy was obtained for artificial teeth with wall thicknesses of at least 0.5 mm.

Comparative Evaluation of the Accuracy of Dynamic Navigation and Free Hand Methods During Zygomatic Implant Placement: A Randomized Controlled Trial.

To assess and compare the precision and predictability of zygomatic implants in atrophic maxilla using conventional and dynamic navigation methods. This study was a randomized controlled clinical trial conducted in patients requiring zygomatic implant placements in the atrophic maxilla. Forty zygomatic implants were placed in systemically healthy individuals. Zygomatic implant placement was done using the freehand technique in the control group, and the test group involved implant placement using a dynamic navigation system, and the entry, apex, and angular deviations were evaluated. The mean deviations at the site of entry (2D) in the navigation system (2.531.42) as compared with the freehand (4.151.29) were statistically significant. The variation in the freehand group was greater than the navigation method at the apex (3D) (P < .05). The navigation method had a higher accuracy in angular deviation than the freehand method (4.02 ± 1.80 and 12.67 ± 2.11). Also, the accuracy was checked on the right and left sides in both the conventional and dynamic groups. The dynamic navigation technology had better predictability in terms of accuracy and precision, and it is the need of the hour for clinicians to master this technology and thereby aid in better prognostic level of implant placements.

Impact of Installation Deviations on the Dynamic Characteristics of the Shaft System for 1 Gigawatt Hydro-Generator Unit

The shaft system, transferring the kinetic energy of water flow into electrical energy, is the most critical component in hydropower plants. Installation deviations of the shaft system for a giant hydro-generator unit can have significant impacts on its dynamic characteristics and overall performance. In this investigation, a three-dimensional geometry of the shaft system of an operating hydro-generator unit prototype with a rated power of 1 GW is established. Then, the calculation model of the shaft system is generated accordingly with tetrahedral and hexahedral elements. By applying different boundary conditions, the finite-element method is used to analyze the influences of installation deviations, including shaft radial misalignment and angular misalignment, on the dynamic characteristics of the shaft system. The calculation results reveal that the installation deviations change the natural frequencies, critical speeds, and mode shapes of the shaft system to a certain degree. The natural frequencies of the backward precession motion with installation deviations are reduced by 23% and 38% for the rated speed and the maximum runaway speed. Furthermore, for the forward precession motion, they increased by 30% and 48%, respectively. The critical speeds for the shaft system with radial and angular deviations are 3.2% and 3% larger than the critical speed of the shaft system without any mounting deviations. The radial and angular installation deviations below the maximum permissible values will not result in the structural performance degradation of the 1 GW hydro-generator shaft system. The conclusion drawn in this research can be used as a valuable reference for installing other rotating machinery.

Depth distortion and angular deviation of a fully guided tooth-supported static surgical guide in a partially edentulous patient: A systematic review and meta-analysis.

This systematic review and meta-analysis aimed to evaluate the depth distortion and angular deviation of fully-guided tooth-supported static surgical guides (FTSG) in partially edentulous arches compared to partially guided surgical guides or freehand. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered in the Open Science Framework (OSF). The formulated population, intervention, comparison, and outcome (PICO) question was: "In partially edentulous arches, what are the depth distortion and angular deviation of FTSG compared to partially guided surgical guides or freehand?" The search strategy involved four main electronic databases, and an additional manual search was completed in November 2023 by following an established search strategy. Initial inclusion was based on titles and abstracts, followed by a detailed review of selected studies, and clinical studies that evaluated the angular deviations or depth distortion in FTSG in partial arches, compared to partially guided surgical guides or freehand, were included. In FTSG, two surgical approaches were compared: open flap and flapless techniques, and two digital methods were assessed for surgical guide design with fiducial markers or dental surfaces. A qualitative analysis for clinical studies was used to assess the risk of bias. The certainty of the evidence was assessed according to the grading of recommendations, assessment, development, and evaluations (GRADE) system. In addition, a single-arm meta-analysis of proportion was performed to evaluate the angular deviation of freehand and FTSG. Ten studies, published between 2018 and 2023, met the eligibility criteria. Among them, 10 studies reported angular deviations ranging from -0.32° to 4.96° for FTSG. Regarding FTSG surgical approaches, seven studies examined the open flap technique for FTSG, reporting mean angular deviations ranging from 2.03° to 4.23°, and four studies evaluated flapless FTSG, reporting angular deviations ranging from -0.32° to 3.38°. Six studies assessed the freehand surgical approach, reporting angular deviations ranging from 1.40° to 7.36°. The mean depth distortion ranged between 0.19mm to 2.05mm for open flap FTSG, and between 0.15mm to 0.45mm for flapless FTSG. For partially guided surgical guides, two studies reported angular deviations ranging from 0.59° to 3.44°. Seven studies were eligible for meta-analysis, focusing on the FTSG in open flap technique, with high heterogeneity (I2 (95%CI) = 92.3% (88.7%-96.4%)). In contrast, heterogeneity was low in studies comparing freehand versus FTSG in open flap techniques (I2 (95%CI) = 21.3% (0.0%-67.8%)), favoring the FTSG surgical approach. In partially edentulous arches, FTSG systems exhibited less angular deviation than freehand and partially guided surgical guides. Flapless surgical approaches were associated with reduced angular deviation and depth distortion, suggesting a potential preference for the FTSG method in these procedures.

Improved method for drone sound event detection system aiming at the impact of background noise and angle deviation

Drones pose a hidden threat to public safety, and effective and accurate detection technology for the drone that exist in the environment is imminent, in which how to weaken the influence of target sound source localization deviation and strong background interference noise on the detection task is the key to improve the accuracy of drone sound event detection. In this paper, a method has been proposed to improve the accuracy of drone acoustic event detection, named as the linear shrinkage-subspace projection-power spectral density filter method (LSP). This method mainly including covariance matrix reconstruction, steering vector recalibration, and filter coefficient redesign method. Firstly, based on Minimum Variance Distortionless Response, the linear shrinkage method is used to suppress the interference and noise components in the signal plus interference covariance matrix, and the sample covariance matrix is reconstructed to eliminate background interference noise. Then, the correlation between the steering vector and the eigenvector is used to eliminate the angle correlation term, and the subspace projection method is combined to recalibrate the steering vector, so as to improve the ability of the beamforming method to resist the angle deviation and realize the correction of the target source positioning deviation. Next, a redesign method for wiener filter coefficients based on the estimated power spectral density is used to further weaken background interference noise. In order to verify the accuracy of the proposed method, a complete drone sound event detection system is constructed by combining the deep learning drone sound event detection classifier, and the evaluation is carried out according to different angular deviations and interference sound distances. In addition, a new evaluation criterion is proposed, named as the Machine-Human Extreme Hearing Distance Rate (MHDR), which analogizes the system's detection ability with the ear's auditory detection ability. The research results of this article indicate that the detection accuracy of the detection system shows satisfactory accuracy when the proposed method is applied to circular microphone array, that improved by 15.12 % compared to existing methods. The proposed method improves the detection accuracy of the drone acoustic event detection task under the influence of sound source position deviation and strong background speech interference, and provides a reference for the development of anti-drone technology.

Mutual visibility of luminous robots despite angular inaccuracy

We initiate the study of the Mutual Visibility problem using N opaque luminous point robots that have inaccurate movements. Each robot operates in Look-Compute-Move cycles and has a persistent light attached to it to have a weak form of communication between robots using a constant number of colors. The inaccuracy for a robot r is an angular deviation from its target point T to a point T′ such that the angle ∠TrT′<90∘. The problem becomes unsolvable if this angle is ≥90∘. From any initial configuration of the robots on the Euclidean plane, the problem aims to arrange the robots in a configuration such that any two robots are visible to each other. We assume that the robots agree on one coordinate axis. We present two collision-free algorithms, a 2 color algorithm (which is optimal in the number of colors used) for semi-synchronous setting and a 3 color algorithm for asynchronous setting, both of which run in O(N) epochs. We also study the problem in the presence of mobile faulty robots. A robot can exhibit both mobility failure and angular inaccuracies in its movement. We present a fault-tolerant algorithm that aims to bring the robots in a configuration where no three non-faulty robots are collinear, and no faulty robot lies between two non-faulty robots. This algorithm uses 10 colors and takes O(N) epochs under asynchronous settings.

Accuracy of navigation guided implant surgery for immediate loading complete arch restorations: Prospective clinical trial.

To assess navigation accuracy for complete-arch implant placement with immediate loading of digitally prefabricated provisional. Consecutive edentulous and terminal dentition patients requiring at least one complete-arch FDP were treated between December 2020 and January 2022. Accuracy was evaluated by superimposing pre-operative and post-operative cone beam computed tomography (CBCT), recording linear (mm) and angular (degrees) deviations. T-tests were performed to investigate the potential effect of the registration algorithm (fiducial-based vs. fiducial-free), type of references for the fiducial-free algorithm (teeth vs. bone screws), site characteristic (healed vs. post-extractive), implant angulation (axial vs. tilted), type of arch (maxilla vs. mandible) on the accuracy with p-value <0.05. Twenty-five patients, 36 complete-arches, and 161 implants were placed. The overall mean angular deviation was 2.19° (SD 1.26°). The global platform and apex mean deviations were 1.17 mm (SD 0.57 mm), and 1.30 mm (SD 0.62 mm). Meaningful global platform (p = 0.0009) and apical (p = 0.0109) deviations were experienced only between healed and post-extraction sites. None of the analyzed variables significantly influenced angular deviation. Minor single-axis deviations were reported for the type of jaw (y-axis at implant platform and apex), registration algorithm (y-axis platform and z-axis deviations), and type of references for the fiducial-free algorithm. No statistically significant differences were found in relation to implant angulation. Within the study limitations navigation was reliable for complete-arch implant placement with immediate loading digitally pre-fabricated FDP. AI-driven surface anatomy identification and calibration protocol made fiducial-free registration as accurate as fiducial-based, teeth and bone screws equal as references. Implant site characteristics were the only statistically significant variable with healed sites reporting higher accuracy compared to post-extractive. Live-tracked navigation surgery enhanced operator performance and accuracy regardless of implant angulation and type of jaw. A mean safety room of about 1 mm and 2° should be considered.

Evaluation of the accuracy of conventional and digital implant impression techniques in bilateral distal extension cases: a randomized clinical trial

BackgroundThis clinical study aims to evaluate the accuracy of the conventional implant impression techniques compared to the digital impression ones in bilateral distal extension cases.MethodsA total of 32 implants were placed in eight patients missing all mandibular posterior teeth except the first premolars. Each patient received a total of four implants, with two implants placed on each side, in order to provide support for three units of screw-retained zirconia restorations. Following osteointegration, the same patient underwent two implant-level impression techniques: Conventional open-tray impressions CII (splinted pick-up) and digital implant impressions DII with TRIOS 3 Shape intraoral scanner. The accuracy of impressions was evaluated utilizing a three-dimensional superimposition analysis of standard tessellation language (STL) files. Subsequently, the scan bodies were segmented using Gom inspect software to measure three-dimensional deviations in a color-coding map. Data were statistically analyzed using the Kruskal Wallis test and then a post-hoc test to determine the significance level (P < 0.05).ResultsThe study revealed that higher angular and positional deviations were shown toward distal scan bodies compared to mesial ones for both impression techniques. However, this difference was not statistically significant (P > 0.05).ConclusionSplinted open-tray conventional impression and intraoral scanning implant impression techniques have demonstrated comparable accuracy.Trial registrationClinical Trials.gov Registration ID NCT05912725. Registered 22/06/ 2023- Retrospectively registered, https://register.clinicaltrials.gov.

Fully automated determination of robotic pedicle screw accuracy and precision utilizing computer vision algorithms

Historically, pedicle screw accuracy measurements have relied on CT and expert visual assessment of the position of pedicle screws relative to preoperative plans. Proper pedicle screw placement is necessary to avoid complications, cost and morbidity of revision procedures. The aim of this study was to determine accuracy and precision of pedicle screw insertion via a novel computer vision algorithm using preoperative and postoperative computed tomography (CT) scans. Three cadaveric specimens were utilized. Screw placement planning on preoperative CT was performed according to standard clinical practice. Two experienced surgeons performed bilateral T2–L4 instrumentation using robotic-assisted navigation. Postoperative CT scans of the instrumented levels were obtained. Automated segmentation and computer vision techniques were employed to align each preoperative vertebra with its postoperative counterpart and then compare screw positions along all three axes. Registration accuracy was assessed by preoperatively embedding spherical markers (tantalum beads) to measure discrepancies in landmark alignment. Eighty-eight pedicle screws were placed in 3 cadavers’ spines. Automated registrations between pre- and postoperative CT achieved sub-voxel accuracy. For the screw tip and tail, the mean three-dimensional errors were 1.67 mm and 1.78 mm, respectively. Mean angular deviation of screw axes from plan was 1.58°. For screw mid-pedicular accuracy, mean absolute error in the medial–lateral and superior–inferior directions were 0.75 mm and 0.60 mm, respectively. This study introduces automated algorithms for determining accuracy and precision of planned pedicle screws. Our accuracy outcomes are comparable or superior to recent robotic-assisted in vivo and cadaver studies. This computerized workflow establishes a standardized protocol for assessing pedicle screw placement accuracy and precision and provides detailed 3D translational and angular accuracy and precision for baseline comparison.

Exploring Polymer-Based Additive Manufacturing for Cost-Effective Stamping Devices: A Feasibility Study with Finite Element Analysis.

This research investigates the feasibility of manufacturing stamping devices using Material Extrusion (MEX) Additive Manufacturing (AM) technology, traditionally fabricated from metal, to reduce production costs and time. This study examines polymer-based devices subjected to Finite Element Analysis (FEA) to evaluate their performance in stamping metal sheets of varying thicknesses. The findings reveal that ABS polymer devices, while demonstrating potential, operate near the material's limit under compression forces, particularly for sheet thicknesses up to 1 mm. Specifically, differences of 0.7 mm were observed at the connection radii of 0.25 mm sheets and 1.4 mm for 0.5 mm sheets, with angular deviations of 1.5 degrees for 0.25 mm sheets and 4 degrees for 0.5 mm sheets. Additionally, devices made of Nylon were deemed suitable for reduced-thickness sheets (0.25 mm), performing better than those made of ABS. These results suggest that while ABS devices exhibit significant deviations (up to 45 degrees for 1 mm sheets), the method shows promise for small batch production and prototyping. Further optimisation through material enhancements and mechanical improvements is recommended to minimise deformations and enhance precision.

Training outcomes of novice clinicians in the use of dynamic computer assisted implant surgery: A prospective comparative study

Background/PurposeThe increasing importance of computer assisted implant surgery (CAIS) in the practice of implant dentistry calls for adequate education and training of clinicians. However, limited evidence exists to support optimal educational strategies and best practices. This study aimed to investigate the effectiveness of distributed training with dynamic CAIS (d-CAIS) on the precision of freehand implant placement by inexperienced operators. Materials and methodsSix senior undergraduate dental students underwent simulation training in freehand implant surgery (5 implants) followed by distributed training in d-CAIS (6 implants). A final assessment of freehand implant placement (5 implants) was conducted thereafter. Outcomes were compared to a benchmark set by an experienced surgeon who repeated the same simulation exercises. Total surgical time and implant placement precision were recorded. ResultsThe average precision of implant placement improved significantly after the d-CAIS training for novice operators. 3D platform deviation (1.63 ± 0.85 vs 0.92 ± 0.23; P < 0.001), 3D apical deviation (1.93 ± 0.88 vs 1.21 ± 0.19; P < 0.001), and angular deviation (5.27 ± 2.30 vs 2.74 ± 1.37; P < 0.001). The students achieved platform deviation comparable to this of the expert, but lagged in angle, apex precision, and total surgical time. ConclusionShort-term, distributed simulation training with d-CAIS can significantly enhance the precision of freehand implant placement by novice operators. However, novice operators still lagged at certain aspects of precision and surgical time when compared with the performance of an experienced surgeon in the same setup.

Comparison of precision of implant placement between two different guided systems for static computer-assisted implant surgery: A simulation-based experimental study

Background/purposeMany designs of static computer-assisted implant surgery (sCAIS) are available for clinician to achieve proper implant position. However, there were not any studies that approached the design alone to evaluate whether sleeve-in-sleeve or sleeve-on-drill design provided most accuracy implant position. The purpose of this study was to investigate the precision of implant placement with sleeve-in-sleeve and sleeve-on-drill static computer assisted implant surgery (sCAIS) designs. Materials and methodsThirty-two models were fabricated simulating a patient with bilateral missing first premolar. Eight models (sixteen implants) were assigned in each group: Group A, B and C represented sleeve-in-sleeve design with 2, 4 and 6 mm sleeve height respectively. Group D represented integrated sleeve-on-drill design with 4 mm sleeve height. 3D deviation at implant platform, apex and angular deviation were measured. Data were analyzed using one way ANOVA (P < 0.05). ResultsThe overall deviation at platform ranged from 0.40 ± 0.14 mm (group A) to 0.73 ± 1.54 mm (group C), at apex from 0.46 ± 0.16 mm (group A) to 1.07 ± 0.37 mm (group C) and the angular deviation ranged from 0.86 ± 0.89° (group A) to 3.40 ± 1.29° (group C). Group A and B showed significantly less deviation than groups C and D (P < 0.05). There was no statistically significant difference in all parameters measured between group A and B, as well as between group C and D (P > 0.05). ConclusionSleeve-in-sleeve sCAIS demonstrated higher precision than sleeve-on-drill sCAIS.

Accuracy of immediate anterior implantation using static and robotic computer-assisted implant surgery: A retrospective study

ObjectivesTo investigate the accuracy of immediate anterior implantation using static computer-assisted implant surgery (s-CAIS) and robotic computer-assisted implant surgery (r-CAIS). Materials and methodsOne hundred and six implants were immediately inserted in the anterior zone of 69 patients using a freehand technique, s-CAIS or r-CAIS. Postoperative cone-beam computed tomography scans were matched with preoperative plans to evaluate the deviations between the planned and placed implant positions. ResultsThe global coronal deviations in the freehand, s-CAIS, and r-CAIS groups were 1.29 ± 0.52 mm, 1.01 ± 0.41 mm, and 0.62 ± 0.28 mm, respectively. Significant differences were observed in the r-CAIS group compared to both the s-CAIS group and the freehand group (p < 0.05). However, no significant differences were found between the s-CAIS group and the freehand group (p > 0.05). The global apical deviations in the freehand, s-CAIS and r-CAIS groups were 1.78 ± 0.59 mm, 1.24 ± 0.52 mm and 0.65 ± 0.27 mm, respectively, while the angular deviations in the freehand, s-CAIS and r-CAIS groups were 6.46 ± 2.21°, 2.94 ± 1.71° and 1.46 ± 0.57°, respectively. Significant differences were observed in both the global apical deviations and angular deviations among the three groups (p < 0.05). ConclusionsThe accuracy of immediate anterior implantation with r-CAIS was better than that with s-CAIS. This difference is attributed to better control of the coronal, vertical and axial errors during r-CAIS. Clinical significanceThis study provides significant evidence to support the use of r-CAIS as a potential alternative in immediate anterior implantation.

Effects of Muscular Fatigue on Position Sense in Two Phases of the Menstrual Cycle.

It is generally accepted that local muscular fatigue can negatively affect position sense. Interestingly, it has been proposed that in women, position sense and neuromuscular coordination may be affected by fluctuations of estrogen and progesterone levels. The aim of this study was to examine the possible effect of localized muscle fatigue on knee joint position sense at two phases of the menses: follicular and luteal. Twenty physically active females aged 19-30 years, with normal menses, volunteered for this study. An isokinetic dynamometer was used to evaluate proprioception and perform the fatigue protocol of the knee extensors and flexors. Knee proprioception at rest and after fatigue at three knee target angles (30°, 45°, 60°) was measured. A three-way ANOVA analysis with repeated measures was performed. The results showed that the main effect of fatigue was significant, but no main effect of the menstrual cycle phase was found. Additionally, a main effect was found for the target angle (more flexed target knee joint angles were associated with larger angular error deviations). In conclusion, localized muscle fatigue can significantly reduce the accuracy of active knee joint repositioning in both the luteal and the follicular menstrual phases in young, physically active healthy women.

Evaluation of the resection plane three-dimensional positional accuracy using a resection guide directional guidance slot; a randomized clinical trial

AimThe study was performed to compare the mandibular resection guide with a directional guidance slot with the conventional guide regarding three-dimensional positional accuracy.Materials and methodsTwenty-six patients with lateral segmental mandibular defects were selected, and randomly allocated into two groups. All defects were managed with preoperative virtual surgical planning. Resection in the test group was conducted using a resection guide with a directional guidance slot, while a conventional resection guide design was utilized in the control group. The linear and angular deviation of the osteotomy planes was analyzed for both groups, along with the accuracy of the insertion of the reconstruction bone block in the resected defect. Data were documented, absolute deviation was calculated, statistical analysis was performed and significance was set at the 5% level.ResultsThe cases conducted with a directional guidance templet reported a statistically significant difference when compared to the conventional edge-cutting guide regarding the linear and angular spatial osteotomy plane position (P < 0.001). The defect span analysis reported excellent levels of agreement in both groups (ICC = 1.00, ICC = 0.995), however, the difference between the groups was statistically significant (P < 0.001).ConclusionThe study demonstrated the enhanced positional accuracy of the resection plane and reconstruction block placement when a directional slot is incorporated in the computer-generated resection guide.

Accuracy of immediately placed implants using surgical guides from different 3-dimensional printers: An in vitro study.

The aim of this study was to evaluate the accuracy of 3-dimensional (3D)-printed surgical guides for fully guided immediate implants from different manufacturers. Eighteen 3D printed fully guided surgical guides (split into 3 groups [n = 6] according to their manufacturer: Company, Desktop, or Lab), were used to place 72 implants (n = 24) in identical maxillary models. After placement, the mean global, angular, mesiodistal, buccopalatal, and vertical deviation at the platform and apex of the placed implants, relative to their preoperatively planned positions, was calculated. Significant differences in global apex deviation, angular deviation, mesiodistal apex deviation, and vertical platform and apex deviation were found between the Lab and Desktop groups (p ≤ 0.007). Significant differences in mesiodistal platform and apex deviation and buccopalatal apex deviation were also found between the Company and Desktop groups (p ≤ 0.005). Finally, significant differences in buccopalatal apex deviation, and vertical platform and apex deviation were found between the Company and Lab groups (p ≤ 0.003). Mean differences between guide groups across all parameters never exceeded 0.5 mm or 1°. The choice of 3D printer has a significant effect on the accuracy of fully guided immediate implants. However, the clinical relevance of these differences may be considered limited.

A Study of the Effect of the Difference in Energy Stored in Two Prosthetic Feet Made of Carbon Fiber Amputated Below the Knee on the Efficiency of Walking

ESAR feet are prosthetic feet with carbon fiber parts that store mechanical energy while standing and release it during propulsion. It is believed to reduce the metabolic energy needed for walking, and to promote the economy of walking. However, there is little scientific evidence to support this claim. This study aimed to compare the energy storage properties of two prosthetic feet made of carbon fiber using the P-Walk, G-Walk, and Podium devices developed for gait analysis, which is a systematic examination of human movement, enabling phasing, estimation of musculoskeletal performance, and determination of kinematic and motor parameters. The amount of energy was calculated for each of the feet using the load deflection test, and the results showed that the new artificial foot with an energy of 6.186 joules showed a great improvement in the results of the tests compared to the old artificial foot with an energy of 3.403 joules. The Podium device tests showed a significant improvement in walking patterns and pressure distribution after using a new foot. The pressure distribution became almost equal on both sides, and the angular deviation of COP decreased from -7 to 1.3 degrees. Ground reaction force vector tilt results also improved, with a body angle of 0 degrees and inclination varying slightly depending on the tibiofemoral angle for males. P-Walk results reveal left-sided static test pressure distribution, exposing amputees to osteoarthritis risk and revealing lack of confidence in prosthetic foot. After use the new prosthetic foot, amputees press more on right foot, indicating balance restoration. The G-Walk device shows the effectiveness of both healthy left and prosthetic foot when walking on an amputated right leg when use the new prosthetic foot. The amputated side's performance is similar to a healthy limb, with minimal difference and within normal limits. Walking cadence and speed values are within normal ranges, while stride length and step length are outside normal ranges for both sides. Obliquity results show a small difference in pelvic angles due to weak pelvic muscles, but these are close to standard values for prosthetic foot use. The amputee's opinions about the evaluation of the new prosthetic foot were good when using the T-score by 61.0 with a rate of 86.4%. It was a significant improvement compared to the old foot with an evaluation of 53.6 by 63.9%.

The effect on the performance of a dynamic navigation system of superimposing a standard tessellation language (STL) file obtained with an intraoral scan on a cone beam computer tomograph (CBCT). An experimental in vitro study

ObjectivesTo compare the accuracy and operative time of implant placement using a dynamic computer assisted implant surgery (dCAIS) system based on a cone beam computer tomography (CBCT) image, with and without superimposing a standard tessellation language (STL) file of an intraoral scan of the patient. MethodsTen identical resin models simulating an upper maxilla with posterior edentulism were assigned to two groups. In the CBCT+STL group, a CBCT file and an intraoral STL file were superimposed and used for registration; in the CBCT group, registration was performed using CBCT images. Six implants were placed in each model using the Navident® dynamic navigation system. Anatomy registration was performed by tracing fiducial points on the CBCT or STL image, depending on the group. Preoperative and postoperative CBCT images were overlaid to assess implant placement accuracy. ResultsSixty implants were analyzed (30 implants in each group). 3D platform deviation was significantly lower (mean difference (MD): 0.17 mm; 95 % confidence interval (CI): 0.01 to 0.23; P = 0.039) in the CBCT+STL group (mean: 0.71 mm; standard deviation (SD): 0.29) than in the CBCT group (mean: 0.88 mm; SD: 0.39). The remaining accuracy outcome variables (angular deviation MD: -0.01; platform lateral deviation MD: 0.08 mm; apex global MD: 0.01 mm; apex depth MD: 0.33 mm) and surgery time (MD: 3.383 min.) were similar in both groups (p > 0.05). ConclusionsThe introduction of an intraoral scan (STL) seems to reduce deviations slightly in dental implant placement with dCAIS systems. However, the clinical repercussion of this improvement is questionable. Clinical significanceSuperimposing an intraoral scan on the CBCT image does not seem to increase the accuracy of dCAIS systems but can be useful when radiographic artifacts are present.

Propagation of elastic waves in fibrous composite with general anisotropy from two families of obliquely inclined fibers

AbstractAn isotropic elastic solid reinforced with two families of aligned fibres behaves anisotropic to any deformation. For arbitrary orientation of fibres in either family, one set of fibres may be inclined obliquely to the aligned fibres in other family. A plane that contains the two families of aligned fibres becomes the plane of symmetry for composite material to exhibit monoclinic anisotropy. For this fibrous anisotropy, a fourth‐order elastic tensor is derived to define the constitutive relations between stress tensor and strain tensor. Components of this elastic tensor involve two Lame's moduli, eight fibroelastic coefficients and the angular deviation between two obliquely inclined fibre‐families. The velocities of bulk waves are calculated for propagation along general direction in this anisotropic composite. Propagation of surface wave is considered along the stress‐free plane boundary of anisotropic elastic half‐space. In a coordinate system with coordinate planes deviating from the plane boundary of the medium and/or plane of anisotropic symmetry, the fibrous composite is treated as triclinic for mathematical convenience. Mathematical model is derived to calculate the phase velocity of the surface wave, which varies with direction on the plane boundary. Horizontal energy flux at the boundary is calculated to determine the group velocity and ray direction of the surface wave. Effects of fibre‐orientations are analysed, numerically, on the wave velocities and ray direction of surface wave.