Skeletal expansion using a miniscrew-assisted rapid palatal expansion in a 50-year-old patient.

This case report illustrates a nonsurgical treatment plan using a miniscrew-assisted rapid palatal expander (MARPE) in a 50-year-old patient with maxillary transverse deficiency. The MARPE appliance consisted of a conventional Hyrax expander anchored to 4 orthodontic miniscrews. The exact locations of the miniscrews were determined with virtual planning software. Cone-beam computed tomography (CBCT) scans were superimposed on the maxillary digital model, and 3-dimensional-printed surgical guides were used to accurately position the mini-implants. A slow expansion protocol was used, and the appliance was held in place during the entire treatment (almost 20 months). Pretreatment, postexpansion, and posttreatment CBCT scans show the parallel expansion obtained without dental torque compensation or bite opening. The posttreatment scan showed that a long period is required to complete the midpalatal suture mineralization. MARPE has proven effective in correcting transverse discrepancies, even in adults. However, posttreatment CBCT imaging showed incomplete ossification of the midpalatal suture, demonstrating that the retention period should be extended in some adult patients.

Cephalometric Floating Norms for the ß Angle and MMBP-Wits.

The importance of an accurate measurement of sagittal jaw relationship, that is, skeletal class, is critical to orthodontic treatment planning. The ANB angle, ß angle, and MMBP-Wits are among indices of sagittal jaw relationship. All of these indices are subjected to geometrical distortion, especially from facial divergence, making the use of floating (individualized) norms necessary. This study thus provides floating norms for the ANB angle and for the first time for the ß angle and MMBP-Wits. Lateral head films were obtained from 119 subjects (74 females and 45 males; mean age, 11.2 ± 1.5 years; range, 8.2-14.0 years) with well-balanced and pleasant profile and a near-ideal occlusion. Multiple regression models were employed to quantify the association of the ANB angle, ß angle, and MMBP-Wits each with other four angular cephalometric parameters including SNA, SN/PP, SN/MP, and NSBa angles. The ß angle and MMBP-Wits were associated with the SNA and SN/MP angles; the ANB angle was associated with all the four other cephalometric variables. Floating norms for the ß angle and MMBP-Wits (but not ANB angle) have been cross-tabulated according to the SNA angle (from 74° to 90°) and SN/MP angle (from 24° to 44°). While the ANB angle is subjected to significantly more geometrical distortion as compared to the ß angle and MMBP-Wits, floating norms may be used to individualize the reference values for both the ß angle and MMBP-Wits.

Effects of deflection and archwire dimension on the mechanical performance of two self-ligating orthodontic systems.

OBJECTIVES: To analyze the effects of archwire deflection and dimension on the mechanical performance of two self-ligating systems, as passive and active ligation designs. MATERIALS AND METHODS: An experimental model was used that was designed to resemble the full dental arch and to allow vertical displacement of a canine element. Two self-ligating systems were investigated: 1) a passive system; and 2) an active system, both in combination with three thermoactive NiTi archwires, with round sections of 0.014-in, 0.016-in and 0.018-in. The full loading-unloading cycles consisted of either 3mm or 6mm maximum deflection, performed at 37 °C. During unloading, the deactivation forces and energy were recorded. The ratio between the deactivation and activation energies was used as representative of the mechanical efficiencies of the systems. RESULTS: The deactivation force increased in combination with larger archwires and greater deflection. The deactivation energy increased in combination with larger archwires only for the 3-mm deflection cycle, while for the 6-mm deflection cycle, the deactivation energy was not influenced by the archwire dimension, and was not greater than that of the 3-mm deflection cycle. The mechanical efficiency decreased in combination with greater deflection and larger archwires, with a maximum decrease of about 12%. Only minor comparative differences were seen between the systems. CONCLUSIONS: The deflection degree and archwire dimension have large effects on the mechanical performance of self-ligating systems.