Saúl Castro

Rethink the malocclusion of class II subdivision

The treatment of the Class II subdivision presents a real challenge in orthodontics, and a lot of discussions are created around it with one important question: What is the best treatment option? We report one young female Patient with Class II subdivision malocclusion treated with an asymmetric extraction of the first permanent maxillary molar on the side of the distoclusion. In this case, we take advantage of the space created from the extraction site to correct the distoclusion and substitute the first molar with the second molar, and by preserving the third molar, we substitute the second maxillary permanent molar with this tooth. The results reveal a good vertical control, Class I molar and Class I canine was achieved accompanied by a correct alignment and leveling of the maxillary and mandibular arches. With this approach, we can respect the geometry of the arch without esthetic damage, functional problems at the level of the temporomandibular joint, keeping all the correct occlusal relationships and guides of dynamics associated with correct arch shape and clear harmony in the excursive movements. It is clinically justifiable to strive for an orthodontic result that respects the spherical functionality proposed by Slavicek.

Effect of activation and preactivation on the mechanical behavior and neutral position of stainless steel and beta-titanium T-loops

Objective To quantify, for each activation, the effect of preactivations of differing distribution and intensity on the neutral position of T-loops (7-mm height), specifically the horizontal force, moment to force (M/F) ratio, and load to deflection ratio. Methods A total 100 loops measuring 0.017 × 0.025 inches in cross-section were divided into two groups (n = 50 each) according to composition, either stainless steel or beta-titanium. The two groups were further divided into five subgroups, 10 loops each, corresponding to the five preactivations tested: preactivations with occlusal distribution (0°, 20°, and 40°), gingival distribution (20°), and occlusal-gingival distribution (40°). The loops were subjected to a total activation of 6-mm with 0.5-mm iterations. Statistical analysis was performed using comprised ANOVA and Bonferoni multiple comparison tests, with a significance level of 5%. Results The location and intensity of preactivation influenced the force intensity. For the M/F ratio, the highest value achieved without preactivation was lower than the height of the loop. Without preactivation, the M/F ratio increased with activation, while the opposite effect was observed with preactivation. The increase in the M/F ratio was greater when the preactivation distribution was partially or fully gingival. Conclusions Depending on the preactivation distribution, displacement of uprights is higher or lower than the activation, which is a factor to consider in clinical practice.