Showing papers by "Amirali Zandinejad published in 2019"

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.

Fracture Resistance of Additively Manufactured Zirconia Crowns when Cemented to Implant Supported Zirconia Abutments: An in vitro Study.

Abstract: Purpose To compare the fracture resistance of implant-supported milled zirconia, milled lithium disilicate, and additively manufactured zirconia crowns. Materials and methods Maxillary cast with a dental implant replacing right second bicuspid was obtained. Custom abutments and full-contour crowns for milled zirconia, milled lithium disilicate, and additively manufactured zirconia crowns (n = 10/group) were digitally designed and fabricated. The crowns were cemented to implant-supported zirconia abutments and mounted onto polyurethane blocks. Fracture resistance was determined by vertical force application using a universal testing machine at a crosshead speed of 2 mm/minute. Kruskal-Wallis test was used to analyze data and failure mode was determined for all the groups. Results Milled zirconia crowns demonstrated the highest median fracture resistance (1292 ± 189 N), followed by milled lithium disilicate (1289 ± 142 N) and additively manufactured zirconia (1243.5 ± 265.5 N) crowns. Statistical analysis showed no significant differences in fracture resistance between the groups (p = 0.4). All specimens fractured at the implant-abutment interface. Conclusion Additively manufactured zirconia crowns demonstrated similar fracture resistance to milled ceramic crowns, when cemented to implant supported zirconia abutments. The results of this in vitro study signify the promising potential of additive manufacturing for the fabrication of all ceramic zirconia crowns.

Workflow description of additively manufactured clear silicone indexes for injected provisional restorations: A novel technique.

Abstract: Objective The present article describes the digital workflow protocol for additive manufacturing (AM) of a clear silicone index to be used for an injected provisional restoration fabrication. Clinical considerations The incorporation of CAD software and AM technologies have allowed the integration of a new way to fabricate conventional diagnostic wax-ups and silicone indexes for preparing diagnostic mock ups, direct composite restorations, or provisional restorations. Although the conventional concept remains, the protocol differs. Conclusions This workflow provides a more efficient and accurate procedure with the reduction of time and cost compared to conventional technique. Clinical significance The digital workflow protocol described for AM of a clear silicone index to be used for an injected provisional restoration fabrication is time and cost efficient compared to conventional procedures.

Perception of occlusal plane that is nonparallel to interpupillary and commissural lines but with the maxillary dental midline ideally positioned.

Abstract: Statement of problem How disparities in parallelism between the occlusal plane and the interpupillary (IP) or commissural facial front lines are perceived is unclear. Purpose The purpose of this observational study was to examine the perceptions of laypersons, dental students, and dentists regarding disparities of the anterior occlusal plane (AOP) and posterior occlusal plane (POP) with respect to the IP and commissural line (CL) with the maxillary dental midline ideally positioned. Material and methods A model of a symmetric female face was digitally created with the IP and CL parallel and the facial midline coincident with the maxillary dental midline. Two groups of images were created, one with the POP modified in 1-degree increments, in which both the maxillary dental midline and the position of the maxillary central incisors were not manipulated, and the other with the POP modified in the same increments but with the position of both maxillary central incisors lengthened to follow the inclination of the occlusal plane. Participants (N=312) were asked to rate the images on a 1-to-6 scale. The Kruskal-Wallis medians test and ordinal logistic regression were used to analyze the ratings. Results Group median ratings for different occupations gradually decreased with increased inclination of the occlusal plane. Significant differences were found for inclinations from 2 to 5 degrees. Significant odd ratios were found for age and sex. Conclusions Dental professionals detected smaller POP disparities. The dentist and dental student groups gave lower ratings in proportion to the amount of POP inclination. Laypersons gave lower ratings only after 3 degrees of POP inclination but still graded all the images as esthetically pleasant. Older people and men tended to give higher ratings to the same image.

Silicone Additive Manufactured Indices Performed from a Virtual Diagnostic Waxing for Direct Composite Diastema Closure Combined with Resin Infiltration Technique on White Spot Lesions: A Case Report.

Abstract: The present article describes the resin infiltration technique to address white spots lesions presented on anterior and premolar teeth of a young patient after orthodontic treatment and the digital workflow for planning a diastema closure on the maxillary anterior teeth using facial photographs, an intraoral scanner, a facially driven diagnostic waxing using a dental computer-aided design (CAD) software, and 3-piece additive manufactured (AM) clear silicone indices. The virtual design of the silicone indices was completed using an open-source CAD software and included a flexible clear buccal piece, flexible clear lingual piece, and rigid clear custom tray. The unique 3-piece index design allows a horizontal path of insertion, controlled uniform thickness of the indices, flexible and rigid material properties combination, accurate translation of the diagnostic waxing into the patient´s mouth, and digital storage of the designs.