A patient with mandibular deviation and 3 mandibular incisors treated with asymmetrically bent improved superelastic nickel-titanium alloy wires

Correction of bilateral heavily impacted second molar with improved super-elastic nickel-titanium alloy wires

Impaction and an abnormal eruption of a second molar occur because of a lack of retromolar space, premature eruption of the mandibular third molar, and ankyloses. The prognosis must be carefully considered when extracting a damaged permanent tooth. In addition to extraction for orthodontics, this enables the establishment of an effective force system to align the impacted tooth. A 21-year-old woman exhibited maxillary anterior crowding, deviation of the maxillary midline, and deeply impacted mandibular second molars bilaterally. The molar relationship was Class II. The cephalometric analysis demonstrated a skeletal Class I relationship (ANB angle, 1.4°); maxillary and mandibular incisors were lingually inclined. Cone-beam computed tomography images indicated that root resorption, caries, and periodontitis were absent in all mandibular molar. Mandibular second premolars were extracted to relieve crowding and achieve Class I molar relationships. The second molars moved mesially on both sides, and there were no signs of ankylosis. We used improved super-elastic nickel-titanium alloy wire (ISW) to upright the mesioangular second molars. We heat-treated the anterior portion of the ISW, including the first molar area, to increase wire stiffness; the posterior portion of the ISW, including the impacted second molar area, remained untreated to ensure that its super-elasticity was preserved. We alleviated crowding, corrected the maxillary midline, and created ideal occlusion with Class I relationship. This case shows that the alignment of a deeply impacted tooth with a heat-treated ISW, combined with voluntary adjustment of wire stiffness, can be a simple and useful treatment option for adult patients.

Comparison of cold-hardening bending and direct electric resistance heat treatment on the mechanical properties and transformation temperature of NiTi archwire: An in vitro study

OBJECTIVES

The aim of this investigation was (1) to compare the effects of cold-hardening bending and direct electric resistance heat treatment (DERHT) methods; and (2) to compare the effects of offsets and angulations on the mechanical properties and thermal analysis of NiTi alloy archwire.

METHODS

Nickel-titanium (NiTi) archwires (Ormco, Glendora, CA), 0.016×0.022-inch, were bent by cold-hardening bending and DERHT methods into 1-mm, 2-mm, or 3-mm offset for a 3-point bending test, and at angles of 30°, 45°, or 60° to the horizontal plane for testing the change in transformation temperature (A_f) measured by differential scanning calorimetry (DSC). The data were analysed using ANOVA followed by the Scheffe post-hoc test.

RESULTS

The 3-point bending test results of the cold-hardening bending and DERHT methods were not significantly different between the 1-mm, 2-mm and 3-mm offset groups (95% CI: -0.05 to 0.97; P=0.082, 95% CI: -0.65 to 0.74; P=0.983 and 95% CI: -0.61 to 0.98; P=0.813, respectively). Increasing the offset resulted in a significantly decreased force in the 3-point bending test (P<0.001). The A_f temperatures of the cold-hardening bending and DERHT methods were not significantly different for the 30°, 45°, and 60° bending angulations (95% CI: -1.93 to 1.39; P=0.876, 95% CI: -1.2 to 0.87; P=0.878, 95% CI: -2.24 to 1.18; P=0.636, respectively). A_f temperatures were not influenced by different bending angulations.

CONCLUSIONS

NiTi archwire shape can be modified by using both cold-hardening and DERHT bending methods, because the mechanical properties and A_f temperature are not affected. However, the bending distance has an effect on the mechanical properties.

Effectiveness of low binding frictional materials: Evaluation of the binding frictional resistance of improved superelastic nickel-titanium alloy wires with different bracket combinations

Introduction:

This study aimed to evaluate the binding frictional resistance of improved superelastic nickel- titanium alloy wires (ISW) with different bracket combinations and to verify the effectiveness of low binding frictional materials by applying them in orthodontic treatment.

Materials and Methods:

Straight stainless steel wire (SSW; 0.016 × 0.022-inch) and straight ISW (0.016 × 0.022- inch) were set to each displaced bracket, and the tensile resistance load was measured. The maximum tensile resistance load was statistically compared using the Tukey test. For exemplification, we treated a typical extraction case of Angle Class I crowding malocclusion with lip protrusion using lower binding frictional materials, which were selected based on tensile test results.

Results:

The SSW and metal bracket combination had the largest maximum tensile resistance load, and the ISW and metal slot-equipped plastic bracket combination had the smallest load (P < 0.01). In a patient treated using lower binding frictional materials, the active treatment period was 9 months. Satisfactory patient results were obtained without using reinforced anchorage.

Conclusions:

Binding frictional resistance varies, depending on the archwire and bracket combination. In a multibracket appliance, selecting materials with as low a binding frictional resistance as possible may make a more effective treatment.

Hypodontia of mandibular incisors: considerations on the orthodontic treatment

Hypodontia is the most prevalent craniofacial malformation in mankind. It may present a wide variety of manifestations and, depending on the number and location of missing teeth, it may affect the esthetics, mastication, speech and occlusal balance. This paper discusses the therapeutic approaches to solve this condition, describing a case report with hypodontia of one mandibular lateral incisor, which treatment option included space closure at the region of hypodontia associated with composite resin restorations in the mandibular central incisors. The three-year follow-up after treatment revealed occlusal stability, adequate intercuspation in Class I relationship and excellent micro and macroesthetics.