To enhance the natural white color of the teeth, the application of a bleaching agent is used. It is a common technique in cosmetic dentistry, representing one of the most demanded procedures in the dental office. 1 Dentistry professionals use several bleaching techniques, including bleaching strips, pens, specific gels, and laser tooth-whitening methods. Teeth whitening techniques commonly utilize carbamide peroxide-or hydrogen peroxidebased solutions. [2][3][4] Our objective was to assess the change in color following the action of various extrinsic substances (methylene blue-based oral antiseptic, black coffee, CocaCola, black tea, red wine, and blueberry jam) and the teeth's ability to return to their initial shade after bleaching.We carried out an in vitro study using 34 teeth of various shades identified with the VITA Shade Key (Panels A, D, G, and J). The teeth were immersed into the extrinsic substances for 24 hours (Panels B, E, H, and K). We can notice that every tooth became darker than its initial shade. The last step was to bleach the colored teeth using 14% hydrogen peroxide for 30 minutes. 5,6 After application of the whitening agent, the teeth gained a whiter shade, but they could not reach the initial one (Panels C, F, I, and L). The images show that the most spectacular changes occurred while using blueberry jam (Panels A, B, and C), Coca-Cola (Panels D, E, and F), red wine (Panels G, H, and I), and methylene blue-based oral antiseptic (Panels J, K, and L).We can conclude that Coca-Cola, blueberry jam, red wine, and black tea had the strongest effect. Most teeth had a satisfactory shade after the bleaching, but none of them returned to the initial aspect. The methylene blue-based oral antiseptic turned out to be the least aggressive agent, the final shade being coincident with the initial one (Panels J, K, and L). Aggressive bleaching can lead to deterioration of the tooth by dehydration and demineralization, even if it temporarily looks whiter for a certain period.

During certain dental treatments, there comes a point when the dentist, in order to counteract certain side effects, has to make a temporary prosthesis. An example would be the temporary prosthesis that is used during a long lasting endodontic treatment, when because of the advanced coronal destruction the occlusal stops are being lost. If this happens, the permanent prosthesis that follows is being compromised due to the extrusion of antagonist tooth.1-3For this purpose, our team imagined a reliable, innovative and experimental solution to create a removable metal crown with a screw (Panel A). The crown has many advantages: it restores the dental morphology of the compromised tooth, maintaining the occlusal stops (Panel B); the crown cannot be removed by the patient, only the dentist can do it with a tiny screwdriver; if the patient is satisfied with the esthetics of the crown, it can be permanently bonded at the end of the treatment.In order to manufacture the crown, we used metal alloy following a precise technique that required all of the dental technician's skills, but also those of the dentist who has to make a special preparation, similar to the on-lays (Panel C). It represents an exercise of mastery, the manufacturing of the thread being one of the most difficult steps of the process (Panel D). This is why we consider that the utility of the crown can also be didactic; dental technician students can practice their manual skills manufacturing it.Unfortunately, not every tooth can receive such a crown. The most indicated teeth are the molars and rarely the premolars, because the margins of the preparation need to have a specific thickness (2.5 mm) in order to avoid a fracture (Panel E), as the crown has an original way of attaching to the tooth (Panel F).In conclusion, this was a first enthusiastic attempt of making a temporary crown with a screw. Further in vitro and clinical studies have to be carried out in order to perfect this concept.