Silvia Logozzo

Accuracy of four intraoral scanners in oral implantology: a comparative in vitro study

BackgroundUntil now, only a few studies have compared the ability of different intraoral scanners (IOS) to capture high-quality impressions in patients with dental implants. Hence, the aim of this study was to compare the trueness and precision of four IOS in a partially edentulous model (PEM) with three implants and in a fully edentulous model (FEM) with six implants.MethodsTwo gypsum models were prepared with respectively three and six implant analogues, and polyether-ether-ketone cylinders screwed on. These models were scanned with a reference scanner (ScanRider®), and with four IOS (CS3600®, Trios3®, Omnicam®, TrueDefinition®); five scans were taken for each model, using each IOS. All IOS datasets were loaded into reverse-engineering software, where they were superimposed on the reference model, to evaluate trueness, and superimposed on each other within groups, to determine precision. A detailed statistical analysis was carried out.ResultsIn the PEM, CS3600® had the best trueness (45.8 ± 1.6μm), followed by Trios3® (50.2 ± 2.5μm), Omnicam® (58.8 ± 1.6μm) and TrueDefinition® (61.4 ± 3.0μm). Significant differences were found between CS3600® and Trios3®, CS3600® and Omnicam®, CS3600® and TrueDefinition®, Trios3® and Omnicam®, Trios3® and TrueDefinition®. In the FEM, CS3600® had the best trueness (60.6 ± 11.7μm), followed by Omnicam® (66.4 ± 3.9μm), Trios3® (67.2 ± 6.9μm) and TrueDefinition® (106.4 ± 23.1μm). Significant differences were found between CS3600® and TrueDefinition®, Trios3® and TrueDefinition®, Omnicam® and TrueDefinition®. For all scanners, the trueness values obtained in the PEM were significantly better than those obtained in the FEM. In the PEM, TrueDefinition® had the best precision (19.5 ± 3.1μm), followed by Trios3® (24.5 ± 3.7μm), CS3600® (24.8 ± 4.6μm) and Omnicam® (26.3 ± 1.5μm); no statistically significant differences were found among different IOS. In the FEM, Trios3® had the best precision (31.5 ± 9.8μm), followed by Omnicam® (57.2 ± 9.1μm), CS3600® (65.5 ± 16.7μm) and TrueDefinition® (75.3 ± 43.8μm); no statistically significant differences were found among different IOS. For CS3600®, For CS3600®, Omnicam® and TrueDefinition®, the values obtained in the PEM were significantly better than those obtained in the FEM; no significant differences were found for Trios3®.ConclusionsSignificant differences in trueness were found among different IOS; for each scanner, the trueness was higher in the PEM than in the FEM. Conversely, the IOS did not significantly differ in precision; for CS3600®, Omnicam® and TrueDefinition®, the precision was higher in the PEM than in the FEM. These findings may have important clinical implications.

Intraoral scanners in dentistry: a review of the current literature

BackgroundIntraoral scanners (IOS) are devices for capturing direct optical impressions in dentistry. The purpose of this narrative review on the use of IOS was to: (1) identify the advantages/disadvantages of using optical impressions compared to conventional impressions; (2) investigate if optical impressions are as accurate as conventional impressions; (3) evaluate the differences between the IOS currently available commercially; (4) determine the current clinical applications/limitations in the use of IOS.MethodsElectronic database searches were performed using specific keywords and MeSH terms. The searches were confined to full-text articles written in English and published in peer-reviewed journals between January 2007 and June 2017.ResultsOne hundred thirty-two studies were included in the present review; among them, 20 were previous literature reviews, 78 were in vivo clinical studies (6 randomized controlled/crossover trials, 31 controlled/comparative studies; 24 cohort studies/case series; 17 case reports) and 34 were in vitro comparative studies.ConclusionsOptical impressions reduce patient discomfort; IOS are time-efficient and simplify clinical procedures for the dentist, eliminating plaster models and allowing better communication with the dental technician and with patients; however, with IOS, it can be difficult to detect deep margin lines in prepared teeth and/or in case of bleeding, there is a learning curve, and there are purchasing and managing costs. The current IOS are sufficiently accurate for capturing impressions for fabricating a whole series of prosthetic restorations (inlays/onlays, copings and frameworks, single crowns and fixed partial dentures) on both natural teeth and implants; in addition, they can be used for smile design, and to fabricate posts and cores, removable partial prostheses and obturators. The literature to date does not support the use of IOS in long-span restorations with natural teeth or implants. Finally, IOS can be integrated in implant dentistry for guided surgery and in orthodontics for fabricating aligners and custom-made devices.

Wear Distribution Detection of Knee Joint Prostheses by Means of 3D Optical Scanners

The objective of this study was to examine total knee polyethylene inserts from in vitro simulation to evaluate and display—using a 3D optical scanner—wear patterns and wear rates of inserts exposed to wear by means of simulators. Various sets of tibial inserts have been reconstructed by using optical scanners. With this in mind, the wear behavior of fixed and mobile bearing polyethylene knee configurations was investigated using a knee wear joint simulator. After the completion of the wear test, the polyethylene menisci were analyzed by an innovative 3D optical scanners in order to evaluate the 3D wear distribution on the prosthesis surface. This study implemented a new procedure for evaluating polyethylene bearings of joint prostheses obtained after in vitro wear tests and the proposed new approach allowed quantification of the contact zone on the geometry of total knee prostheses. The results of the present study showed that mobile TKPs (total knee prosthesis) have lower wear resistance with respect to fixed TKPs.

A Parametric Study on Friction Instabilities in Mechanical Face Seals

ABSTRACT The present article aims to analyze and evaluate how dynamic parameter design influences the behavior of mechanical face seals and improves their performance by detecting undesirable phenomena like stick–slip and ringing. Those phenomena occur in situations of boundary lubrication. A new lumped parameter model is proposed to study mechanical face seals used in automotive cooling water pumps in order to examine how dynamic parameters such as mass, moment of inertia, and stiffness are involved in stick–slip phenomena. The aim of this work is to provide a practical design tool to predict stick–slip conditions and to choose the optimal mechanical specifications. Numerical simulations demonstrate how the critical service conditions vary with design parameters and permit tabulation of the results.

Study of Wear of Planetary Concrete Mixer Blades Using a 3D Optical Scanner

Performance optimization of a concrete mixer is fundamental in many industrial technologies. Wear is one of the main phenomena to be forecast and tested during the design and service of mechanical components. In all the concrete mixers types, blades suffer the wear more than other components.Two different blade shapes have been tested in order to evaluate the wear rates and which of them has the best performance in terms of wear resistance. One of the two shapes has been designed in order to minimize wear rates and to allow longer durability, on the basis of a theoretical approach.To guarantee the consistence of the comparison, the two different blades have been tested in a dedicated planetary concrete mixer, with the same operating conditions (time-period, same mixture and mixer).The purpose of this paper is to show optical non-contact measurements of worn blades operating in a planetary concrete mixer in order to evaluate wear rates and to validate the efficiency of the new blade design.Copyright

A New Automated 2 DOFs 3D Desktop Optical Scanner

The goal of this research work was to create a completely automated desktop 3D optical measuring system for parts having freeform and complex surfaces, with high and certifiable resolution, precision and accuracy to be suitable for metrology. The proposed device is based on the principle of structured light active triangulation. The hardware system consists of an optical system, with a 2 degrees of freedom (DOFs) motorized tilt-rotational table and a framework providing fixtures for a proper location of the target specimen. The software module is able to synchronize the optical and mechanical systems after optical and mechanical calibrations. The mesh representing the measured object is registered automatically by stitching together all the single 3D data sets acquired at each movement of the positioning system. The quality of the result is evaluated by checking the difference between a certified reference model and the measured data.

New Challenges in Tribology: Wear Assessment Using 3D Optical Scanners

Wear is a significant mechanical and clinical problem. To acquire further knowledge on the tribological phenomena that involve freeform mechanical components or medical prostheses, wear tests are performed on biomedical and industrial materials in order to solve or reduce failures or malfunctions due to material loss. Scientific and technological advances in the field of optical scanning allow the application of innovative devices for wear measurements, leading to improvements that were unimaginable until a few years ago. It is therefore important to develop techniques, based on new instrumentations, for more accurate and reproducible measurements of wear. The aim of this work is to discuss the use of innovative 3D optical scanners and an experimental procedure to detect and evaluate wear, comparing this technique with other wear evaluation methods for industrial components and biomedical devices.

Stick-Slip Simulation and Detection in Mechanical Face Seals

The present paper proposes a new model and method to detect the occurrence of dynamic instabilities and stick-slip in mechanical face seals used in automotive cooling water pumps, in order to improve their performance. A new tribo-dynamic model is presented and used to examine how many and what design parameters influence stick-slip. Mass, moment of inertia, stiffness, damping ratio, friction relationship, viscosity, roughness and wear, compressive strength of different coupling materials, geometrical specifications and temperature are some of the analyzed parameters. Therefore, this work provides a full overview of the influence of design parameters on the stick-slip phenomenon.Copyright

A Robotic 3D Vision System for Automatic Cranial Prostheses Inspection

The goal of this research work was to create a prototype of a robotic 3D vision system for cranial prostheses automatic inspection. The proposed device is able to automatically scan the entire prosthesis under study by means of an automatic tilt-rotational mechanism and the embedded software allows to generate an automatic inspection report by comparing the specimen with a reference digital sample. The output of the procedure gives information about the geometrical conformity of the new fabricated prosthesis and automatically accept or discard the product. The presented prototype is the first one in literature to have such an automated quality control and rejection procedure in 3D vision and it is also the first robotic vision system applied to cranial prosthesis manufacturing.