PurposeThe goal of rapid mechanical prototyping is to be able to quickly fabricate complex‐shaped, 3D parts directly from computer‐aided design models. The key idea of this novel technology is based upon decomposition of 3D computer models data into thin cross‐sectional layers, followed by physically forming the layers and stacking them up; “layer by layer technique.” This new method of modeling has raised many attentions in dentistry especially in the field of surgery and implantology. The purpose of this review study is to represent the historical development and various methods currently used for building dental appliances. It is also aimed to show the many benefits which can be achieved by using this new technology in various branches of dentistry.Design/methodology/approachThe major existing resources, including unpublished data on the internet, were considered.FindingsAlthough, creating 3D objects in a layered fashion is an idea almost as old as human civilization but, this technology has only recently been employed to build 3D complex models in dentistry. It seems that in near future many other methods will develop which could change traditional dental practices. It is advisable to include more unit hours in dental curriculums to acquaint dental students with the many benefits of this novel technology.Originality/valueIt is hard to believe that the routine dental techniques were affected by revolutionary concepts originally theorized by engineering methods. It is a reality that in future, most of the restorative disciplines will be fully revised and the computer methods be evolved to an extent where dentistry can be performed by computer‐assisted methods with optimum safety, simplicity, and reliability.

Dental students in programs around the world typically pass preclinical courses before entering the clinic and working on actual patients. Since ixed prosthodontics is a preclinical course that requires a great deal of effort, students may experience a substantial amount of stress that may affect their self-conidence and/or clinical performance. In this study, an instructional video CD (VCD) and study guide depicting the step-by-step procedures involved in a metal-ceramic tooth preparation and provisional crown fabrication was prepared. Students at the Faculty of Dentistry, Tehran University of Medical Sciences, Tehran, Iran, were divided randomly into two groups. Group A students trained as usual with live patients, and Group B students were given a copy of the VCD and study guide following a lecture. The students in Group B were encouraged to read the study guide and watch the VCD after live demonstrations. Then, both groups practiced individually on mannequins. At the end of the course, the students completed a sixteen-item questionnaire about their stress level, self-conidence, and knowledge base. The results showed that the students exposed to the extra media performed signiicantly better on some practical phases, e.g., laboratory procedures. A moderate, insigniicant correlation was detected between exposure to media and decreasing the students' stress and self-esteem. We concluded that supplementary teaching aids such as a VCD and study guide may improve the clinical performance of dental students to some extent, but the live demonstration is still preferred by students.Dr. Nikzad is Associate Professor,

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Background The accurate transfer of preoperatively determined implant positions to the patient mouth is very beneficial to the dental practitioner as well as patients. The objective of this paper was to review the gradual development of computer-assisted implant surgery.

Increase in firing cycles decreased MTBS. Most of the failures (90-95%) in all three groups were cohesive in the veneering porcelain and did not change as the number of firing cycles increased.

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The poor bonding strength of zirconia to different dental substrates is one of the challenging issues in restorative dentistry. Hydroxyapatite is an excellent biocompatible material with fine bonding properties. In this study, it was hypothesized that hydroxyapatite coating on zirconia would improve its bond strength. Forty-five zirconia blocks were prepared and randomly divided into three groups: hydroxyapatite coating, sandblasting, and no preparation (control). The blocks were bonded to cement and the micro-shear bond strength was measured following load application. The bond strength values were analyzed with the Kruskal-Wallis test in 3 groups and paired comparisons were made using the Mann-Whitney U test. The failure patterns of the specimens were studied by a stereomicroscope and a scanning electron microscope and then analyzed by the chi-square test (significance level = 0.05). Deposition of hydroxyapatite on the zirconia surface significantly improved its bond strength to the resin cement in comparison with the control specimens (p < 0.0001). Also, the bond strength was similar to the sandblasted group (p = 0.34). The sandblasted and control group only showed adhesive failure, but the hydroxyapatite coated group had mixed failures, indicating the better quality of bonding (p < 0.0001). As a final point, hydroxyapatite coating on the zirconia surface improved the bond strength quality and values.

Background/purpose: Discoloration of resin-based restorations is considered a common obstacle in restorative dentistry. Several studies assessed the color stability of direct resin composites; however, little is known regarding indirect/laboratory composite resins (ICRs). The purpose of this study was to investigate the color stability of two ICRs (Gradia, Gradia, GC Dental Products) and (SR-Adoro, SR Adoro, Ivoclar Vivadent) compared to a feldspathic porcelain (Ceramco II, DENTSPLY Ceramco) following immersion in different beverages or subjected to accelerated aging. Materials and methods: Using a machine-made metal mold, 20 disc samples (10 mm in diameter and 2 mm thick) were fabricated from each proposed material. Discs were randomly divided into four groups. The baseline measurements of CIELAB metric parameters were performed on all specimens with a spectrophotometer. Three groups then underwent an immersion process in different media (coffee, tea, and cola) for 2 weeks. The last group was subjected to UV aging for 300 hours. The color coordinates and their corresponding color changes (DE) were measured. Results: The greatest color changes were seen in the coffee solution (DE Z 13.34 for SR-Adoro and DE Z 16.