With a reengineered parallelogram slot shape for the bracket and redesign of the cross-sectional geometry of the traditional rectangular wire, the Damon Ultima System demonstrates more predictable first-order control earlier in treatment.
By Thomas Barron, DMD, MS, and Michael J. Mayhew, DDS, MS, MS
The Passive Self-Ligating (PSL) appliance delivers a lower biomechanical load1,2 by reducing the frictional resistance and binding at the bracket slot/archwire interface.3,4,5,6,7,8 This has been shown to optimize the load-deflection characteristics of super-elastic, low-force, nickel-titanium wires compared with other methods of ligation.9 Though ligation passivity is important for lower-force application, it has presented challenges for three-dimensional control of the dentition compared with traditionally ligated appliances. Here, we present evidence from a multi-site clinical evaluation on the efficacy of rotational control achieved with a new PSL bracket and wire system that features novel changes to the cross-sectional geometries of the bracket slot and archwire.
The concept of programming tooth guidance into the bracket rather than into the wire came to fruition in the early 1970s with Andrews’s Straight Wire Appliance (SWA).10,11,12 In order to achieve level slot lineup in which the Facial Axis points of the teeth, and base and slot points of the brackets are coincident on the same horizontal plane, the original SWA required placing the prescribed torque in the base of the bracket.
The passive sliding door of subsequent PSL bracket technology presented a unique set of design challenges for programing tooth movement. Since the door assembly is structurally supported in the body of the bracket tie wing, it was necessary to change the inclination of the bracket stem to create the variable high- and low-torque couple brackets available in the Damon System (Ormco Corp). This change in stem inclination presents challenges for level slot alignment and tooth position when placing variable torque brackets on adjacent teeth using the bracket pads as visual cues for placement (Figure 1). In addition, changes in the stem inclination resulted in changes to the inclination of the bracket face, reducing the clearance between the tie wing and pad. This decreased tie wing space created difficulty for placement of auxiliary elastomeric and steel ligation.
To address these issues, the Damon Ultima bracket used in this clinical evaluation includes a re-engineered parallelogram slot shape in the high- and low-couple brackets that provides, for the first time in the evolution of PSL technology, a level slot alignment without changing the orientation of the bracket stem and face (Figure 2). In addition to uniform slot alignment, ample tie wing space is achieved for auxiliary ligation.
Ormco’s Damon Ultima System also includes a novel redesign of the cross-sectional geometry of the traditional rectangular wire. The labio-lingual surfaces of the Copper NiTi (CN) Damon Ultima archwire have been rounded, increasing the 0.025” dimension to 0.0275” at the height of its radius (Figure 3), which provides simultaneous points of contact with the base of the slot and the fourth wall or door of the bracket along the radius of the rounded side of the wire (Figure 4A). This interaction between the bracket and wire restricts the mesial-distal freedom of rotation of the bracket and tooth beginning at the 0.014” x 0.0275” wire stage of treatment (Figure 4B).
For this clinical evaluation, 133 patients were treated with the Damon Ultima System appliance at eight clinical sites comprised of orthodontic specialists employing PSL treatment in their private practices. A minimum of 10 and up to 50 consecutive cases that fit the clinical evaluation criteria were treated at each site with proper consent. The inclusion criteria required patients in permanent dentition from first molar to first molar who did not require orthognathic surgery or TAD-assisted tooth movement. Initial orthodontic diagnostic records including digital intraoral scans and CBCT imaging were taken.
Patients were seen at 4-week assessment intervals. Full photographic records and digital intra-oral scans with wires in place were obtained at each appointment along with clinician reporting forms. A second full set of photographs and intraoral scans with wires in place were obtained after each wire change. Full photographic records, intraoral scans and CBCT imaging were taken at the completion of treatment. After initial leveling, aligning, and arch development with small-diameter, low-modulus of elasticity, round CN wires, Damon Ultima 0.014” x 0.0275” round-sided, rectangular CN archwires were engaged. Although the Damon Ultima bracket and archwire combination is engineered to provide rotational control with <1º of freedom of rotation, rotational correction assessments were made by each clinician at the conclusion of the 0.014” x 0.0275” CN wire phase using a visual analog scale in which a < 2° rotation angle was determined to be the threshold for an acceptable rotation angle (Figure 5.)
First-order rotations present in initial malocclusions were determined to be completely corrected after the 0.014” x 0.0275” round-sided, rectangular CN Damon Ultima archwire phase in 98.9% of the recorded cases. Occlusal photographs and digital scans of pretreatment malocclusions were compared with those at the completion of the 0.014” x 0.0275” wire phase for each patient. Figure 6 through 12 below show clinical examples of the rotation corrections observed in the patients examined in this clinical evaluation. In each clinical example, Figure A shows T1, photographed at the initial bonding appointment with placement of the initial wire. Figure B shows T2, photographed at the conclusion of the 0.014” x 0.0275” Ultima wire.
Simultaneously engaging the base of the slot and the bracket door along the radius of the rounded sides of the 0.014” x 0.0275” CN Damon Ultima archwires reduces the first-order freedom of rotation leading to effective correction of rotated teeth. Predictably achieving first-order control earlier in the treatment course, with minimal wire or bracket position adjustments, increases clinical efficiency, and has the potential to reduce treatment time in patients treated with this PSL fixed appliance. It has been said that the biomechanical advantages of reduced frictional resistance and binding at the bracket slot/wire interface with the PSL appliance will be particularly beneficial once the present three-dimensional control issues have been satisfactorily resolved.13 The results of this clinical evaluation suggest that, with respect to rotational control, the Damon Ultima bracket and archwire system have greatly enhanced control in the first-order dimension beginning with the 0.014” x 0.0275” wire stage of treatment. The positive effect of the round-sided, rectangular Damon Ultima archwires and the parallelogram slot of the Damon Ultima brackets on third-order torque control was also assessed in this multi-site clinical evaluation and will be presented in a future report. OP
Thomas Barron, DMD, MS, earned his doctoral degree in dental medicine at Tufts University School of Dental Medicine and received his post-doctoral degree in orthodontics, and MS in oral biology from the University of Maryland, Baltimore College of Dental Surgery. He has been treating patients exclusively with low-friction/low-force PSL in his private practice for 14 years. He is an original member of the Damon Champion Group and Key Opinion Leader and member of the Ormco Speakers Bureau. He is co-author of the Damon PSL University Teaching Modules and is a member of the Dean’s Faculty and part-time Assistant Clinical Professor in the Department of Orthodontics at the University of Maryland.
Michael J. Mayhew, DDS, MS, MS, received his dental education and dual-specialty degrees in pediatric dentistry and orthodontics from the University of North Carolina. Board certified in both specialties, he operates two dual-specialty practices in Boone and North Wilkesboro, NC. Mayhew lectures on the Damon System, CAD/CAM digital orthodontics, indirect bonding, and CBCT utilization. He is on the Sports Medicine Team at Appalachian State University, is an adjunct clinical professor at the UNC School of Dentistry, and serves as director of the North/South Carolina Damon Study Club. He was inducted into the American College of Dentists in 2010 and the International College of Dentists in 2013.
Disclosure: Barron and Mayhew are paid consultants for Ormco. The opinions expressed are those of Barron and Mayhew. Ormco is a medical device manufacturer and does not dispense medical advice. Clinicians should use their own professional judgment in treating their patients. (Patient results may vary)
- Badawi, H. personal communication November 2012
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