Amirali Zandinejad

Bio: Amirali Zandinejad is an academic researcher from Texas A&M University. The author has contributed to research in topics: Materials science & Medicine. The author has an hindex of 15, co-authored 56 publications receiving 871 citations. Previous affiliations of Amirali Zandinejad include Tehran University of Medical Sciences & University of Louisville.

Intraoral digital scans-Part 1: Influence of ambient scanning light conditions on the accuracy (trueness and precision) of different intraoral scanners.

Abstract: Statement of problem Digital scans have increasingly become an alternative to conventional impressions. Although previous studies have analyzed the accuracy of the available intraoral scanners (IOSs), the effect of the light scanning conditions on the accuracy of those IOS systems remains unclear. Purpose The purpose of this in vitro study was to measure the impact of lighting conditions on the accuracy (trueness and precision) of different IOSs. Material and methods A typodont was digitized by using an extraoral scanner (L2i; Imetric) to obtain a reference standard tessellation language (STL) file. Three IOSs were evaluated—iTero Element, CEREC Omnicam, and TRIOS 3—with 4 lighting conditions—chair light 10 000 lux, room light 1003 lux, natural light 500 lux, and no light 0 lux. Ten digital scans per group were recorded. The STL file was used as a reference to measure the discrepancy between the digitized typodont and digital scans by using the MeshLab software program. The Kruskal-Wallis, 1-way ANOVA, and pairwise comparison were used to analyze the data. Results Significant differences for trueness and precision mean values were observed across different IOSs tested with the same lighting conditions and across different lighting conditions for a given IOS. In all groups, precision mean values were higher than their trueness values, indicating low relative precision. Conclusions Ambient lighting conditions influenced the accuracy (trueness and precision) of the IOSs tested. The recommended lighting conditions depend on the IOS selected. For iTero Element, chair and room light conditions resulted in better accuracy mean values. For CEREC Omnicam, zero light resulted in better accuracy, and for TRIOS 3, room light resulted in better accuracy.

Comparison of the marginal fit of lithium disilicate crowns fabricated with CAD/CAM technology by using conventional impressions and two intraoral digital scanners.

Abstract: Statement of problem Conventional impression materials and techniques have been used successfully to fabricate fixed restorations. Recently, digital pathways have been developed, but insufficient data are available regarding their marginal accuracy. Purpose The purpose of this in vitro study was to compare the marginal gap discrepancy of lithium disilicate single crowns fabricated with computer-aided design and computer-aided manufacturing (CAD/CAM) technology by using both conventional and 2 digital impression techniques. Material and methods One typodont maxillary right central incisor was prepared for a ceramic crown. Ten impressions were made by using each method: conventional with polyvinyl siloxane impression material, Lava COS (3M ESPE), and iTero (Cadent) intraoral scanning devices. Lithium disilicate (e.max CAD) crowns were fabricated with CAD/CAM technology, and the marginal gap was measured for each specimen at 4 points under magnification with a stereomicroscope. The mean measurement for each location and overall mean gap size by group were calculated. Statistically significant differences among the impression techniques were tested with F and t tests (α=.05). Results The average (±SD) gap for the conventional impression group was 112.3 (±35.3) μm. The digital impression groups had similar average gap sizes; the Lava group was 89.8 (±25.4) μm, and the iTero group was 89.6 (±30.1) μm. No statistically significant difference was found in the effects among impression techniques ( P =.185) Conclusions Within the limitations of this study, digital and conventional impressions were found to produce crowns with similar marginal accuracy.

A review on chemical composition, mechanical properties, and manufacturing work flow of additively manufactured current polymers for interim dental restorations.

Abstract: Objectives Additive manufacturing (AM) technologies can be used to fabricate 3D-printed interim dental restorations. The aim of this review is to report the manufacturing workflow, its chemical composition, and the mechanical properties that may support their clinical application. Overview These new 3D-printing provisional materials are typically composed of monomers based on acrylic esters or filled hybrid material. The most commonly used AM methods to manufacture dental provisional restorations are stereolithography (SLA) and material jetting (MJ) technologies. To the knowledge of the authors, there is no published article that analyzes the chemical composition of these new 3D-printing materials. Because of protocol disparities, technology selected, and parameters of the printers and material used, it is notably difficult to compare mechanical properties results obtained in different studies. Conclusions Although there is a growing demand for these high-tech restorations, additional information regarding the chemical composition and mechanical properties of these new provisional printed materials is required. Clinical significance Additive manufacturing technologies are a current option to fabricate provisional dental restorations; however, there is very limited information regarding its chemical composition and mechanical properties that may support their clinical application.

Process Development of Porcelain Ceramic Material with Binder Jetting Process for Dental Applications

Abstract: Custom ceramic structures possess significant potentials in many applications such as dentistry and aerospace where extreme environments are present. Specifically, highly customized geometries with adequate performance are needed for various dental prostheses applications. This paper demonstrates the development of process and post-process parameters for a dental porcelain ceramic material using binder jetting additive manufacturing (AM). Various process parameters such as binder amount, drying power level, drying time and powder spread speed were studied experimentally for their effect on geometrical and mechanical characteristics of green parts. In addition, the effects of sintering and printing parameters on the qualities of the densified ceramic structures were also investigated experimentally. The results provide insights into the process–property relationships for the binder jetting AM process, and some of the challenges of the process that need to be further characterized for the successful adoption of the binder jetting technology in high quality ceramic fabrications are discussed.

3D printing in dentistry.

Abstract: 3D printing has been hailed as a disruptive technology which will change manufacturing. Used in aerospace, defence, art and design, 3D printing is becoming a subject of great interest in surgery. The technology has a particular resonance with dentistry, and with advances in 3D imaging and modelling technologies such as cone beam computed tomography and intraoral scanning, and with the relatively long history of the use of CAD CAM technologies in dentistry, it will become of increasing importance. Uses of 3D printing include the production of drill guides for dental implants, the production of physical models for prosthodontics, orthodontics and surgery, the manufacture of dental, craniomaxillofacial and orthopaedic implants, and the fabrication of copings and frameworks for implant and dental restorations. This paper reviews the types of 3D printing technologies available and their various applications in dentistry and in maxillofacial surgery.

Intraoral scanners in dentistry: a review of the current literature

Abstract: Intraoral 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. Electronic 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. One 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. Optical 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.

Binder jetting: A review of process, materials, and methods

Abstract: Binder Jet printing is an additive manufacturing technique that dispenses liquid binding agent on powder to form a two-dimensional pattern on a layer. The layers are stacked to build a physical article. Binder Jetting (BJ) can be adapted to almost any powder with high production rates and the BJ process utilizes a broad range of technologies including printing tehniques, powder deposition, dynamic binder/powder interaction, and post-processing methods. A wide variety of materials including polymers, metals, and ceramics have been processed successfully with Binder Jet. However, developing printing and post-processing methods that maximize part performance is a remaining challenge. This article presents a broad review of technologies and approaches that have been applied in Binder Jet printing and points towards opportunities for future advancement.