βTi T-type loops are a frictionless, efficient alternative for extraction space closure. Changes in the upper horizontal portion of T-type loops to improve their mechanical behavior have been proposed, but differences in their biomechanical characteristics have not been well described. This stu dy analyzed the biomechanical differences among three T-type loops with differential bends in their upper horizontal portion. Ninety loops (0.017"x0.025" βTi) were bent and randomly divided in 3 groups according to the form of their upper horizontal portion (T [straight], M [convex], and C-loops [concave]), to evaluate force characteristics up to 6 mm of activation. Stiffness, maximum horizontal loads, total loop moments, and moment-to-force ratios were obtained. Nonparametric statistical analyses were used to test differences among groups. M-loops demonstrated lower force than T-and C-loops, and higher total loop moment than T-loops. A significant increase in M-loop moment-to-force ratio compared with T-or C-loops was obtained. C-and T-loops did not demonstrate significant differences in moment-to-force ratio between them. The convex upper bend in M-loops produced an increased total loop moment compared with T-loops. M-loops demonstrated moment-to-force values slightly higher than translation values, while the other loops reported only controlled inclination values at 6 mm of activation. M-loops are ideal when a higher control of root movement is indicated since the beginning of dental retraction in segmented arch mechanics.

Understanding the cellular principles of odontogenesis requires an incremental and up-to-date understanding of the sequential molecular embryological processes leading to a complete normal dental formation. This topic review provides a state-of-the-art explanation of these dental morphogenetic processes and the subsequent crown development in normal deciduous and permanent teeth, based on an upgraded version of the “odontogenic homeobox code”. The description of these processes is shown from the differential epithelium-ectomesenchyme and epithelium-mesenchyme interaction stand-points, necessary to produce cell-cell and extracellular matrix-cell transformations. These cellular processes lead to the sequential stages of classic histological dental formation, which progressively correspond to the development of dental regions, identities, and forms, to obtain complete deciduous and permanent human dentitions.

The treatment of patients with cleft lip with/without cleft palate is still a challenge for its correct team management. The fact that not all clefts are alike, based on anatomical findings and ortho/surgical alternatives used in their correction, requires that clinicians -working in interdisciplinary or multidisciplinary teams- direct efforts not only to repair the facial and oral characteristics of the cleft, but also to work in the context of the patient’s craniofacial growth and development, tri-dimensionally affected by this type of craniofacial difference. The first part of this chapter is focused on the diagnostic approach for patients with unilateral cleft lip and palate (UCLP), using a modified version of the GOSLON yardstick (GOSLON+) that considers not only dental components but also 3D facial aspects of a complex malocclusion originated from this congenital malformation. Second, current treatment alternatives based on patient’s stages of dental development and cleft width, using either straight-wire or passive self-ligation appliances are presented, directed to avoid dental prosthetic replacements if possible. Finally, our treatment algorithms summarized in a step-by-step fashion the treatment of such differences with approaches that will focus on these two key aspects, essential for a successful, patient-based, interdisciplinary treatment protocol.