Biomechanically and Periodontally-Based Orthodontic Treatment of a Patient with Upper Canine Affected by External Cervical Resorption (ECR): A Case Report.

(1) Background: Orthodontic treatment may be a potential predisposing factor for ECR. The affected tooth goes to ankylosis, which could lead to a malocclusion. Although teeth severely affected by ECR (class IV Heithersay) are usually extracted, this case report aims to present the use of an ECR class IV upper canine, both as ankylosed to solve the malocclusion and the occlusal plane canting, as well as not ankylosed to correct its ridge defect with orthodontic extrusion. (2) Methods: A 14-year-old male, complaining of an ugly smile and a failed orthodontic attempt to recover an impacted canine, was referred to the orthodontic clinic. He was diagnosed with class II right subdivision, midline deviation, both upper and lower occlusal plane canting, and an upper left canine, previously impacted, showing ECR class IV. The treatment first included canting resolution with a cantilever and a spring, exploiting the anchorage offered by the ankylosed ECR canine. Then, a coronectomy, endodontic treatment, and orthodontic extrusion of that canine were performed to obtain the implant site development. (3) Results: Clinical and radiographic outcomes showed normocclusion and better bony conditions for safer implant placement in the aesthetic zone. (4) Conclusions: The high aesthetics and the periodontal and bony conditions obtained are probably not achievable by other therapeutic alternatives.

The six geometries revisited.

Forces and moments delivered by a straight wire connecting two orthodontic brackets are statically indeterminate and cannot be estimated using the classical equations of static equilibrium. To identify the mechanics of such two-bracket systems, Burstone and Koenig used the principles of linear beam theory to estimate the resulting force systems. In the original publication, however, it remains unclear how the force systems were calculated because no reference or computational details on the underlying principles have been provided. Using the moment carry-over principle and the relative angulation of the brackets, a formula was derived to calculate the relative moments of the two brackets. Because of the moment equilibrium, the vertical forces that exist as a forcecouple on the two brackets can also be calculated. The accuracy of the proposed approach can be validated using previously published empirical data.

Molar uprighting with mini screws: comparison among different systems and relative biomechanical analysis.

Starting from a segmented approach, the Authors propose 3 different methods of using mini screws during the process of molar uprighting. The first UPG is performed by placing a mini screw in the retromolar area and by applying an elastic chain loaded between the screw and the molar.The second UPG is made by placing a screw in the retro molar area and by using a small cantilever which is active during intrusion and uprighting.The third UPG is made by using a miniscrew placed a few millimeters mesial to the molar to control the vertical force produced by the uprighting with a long cantilever to the frontal teeth.To assist in the understanding of the different clinical indications, the biomechanical differences between these three systems are analyzed.

The Bracketless Fixed Orthodontics: nine years of clinical experimentation.

The Bracketless Fixed Orthodontics (BFO) is an innovative appliance made up of wires and resin. It comes from the observation of the instable position of frontal teeth still bonded to a fixed retainer and from a period of nine year of clinical experimentation on a way to preactivate a wire to obtain a wished dental movements without brackets. For this historical reasons the first experimental name was: Preactivated Retainers. It can be used to levelling teeth, as in case of relapse, or to remove the brackets before the end of the therapy. But it can be used also in more complicated clinical cases in patient that never have been treated with orthodontic therapy, alone or associated to other appliances. In this article are showed only some exemplificative clinical cases. The resolution of crowded teeth, the torque correction and the closing diastema. This appliance applied whether on the buccal aspect or on the lingual aspect of the teeth offers different advantages, as it guarantees a good control of the dental movement, also in the root movement, does not interfere in patients' phonetics and does not interfere in oral hygiene. Since don't exist neither precise references, like brackets, nor a codified therapeutic sequence the best results could be achieved accurately applying the principles of biomechanics described by Burstone and Melsen in their segmented approach.