Precision Orthodontics: Customized Versus Conventional Orthodontic Bracket Prescriptions - A Randomized Controlled Clinical Trial

Teeth and orthodontic treatment plans are very unique to the specific patient, yet standard orthodontic braces are currently "one-size fits all". In the early 20th century, orthodontics was practiced using non-programmed brackets. First, second and third order bends had to be incorporated into the wire in order to achieve ideal final tooth positions.

Andrews' Straight Wire Appliance (SWA) in the 1970s, however, revolutionized orthodontic care by presenting a standard set of brackets with pre-programmed prescriptions built into the appliance system [5-7]. According to Andrews, "it is far easier to control tooth movement with bracket placement than bending wires".

Andrews analyzed 120 patient cases which presented with what he described as an ideal occlusion. He documented common characteristics in regard to angulation, tip, and torque subjectively deemed to create an ideal occlusion. This allowed him to develop a bracket prescription to compensate for the disparity in the contour of the facial surfaces of teeth by increasing thickness of the bracket base. Furthermore, he introduced angulations within the bracket slot to achieve proper positioning of the roots [5, 8]. This "straight-wire appliance" (SWA) method became widely accepted in orthodontics, and numerous variations of pre-adjusted bracket systems have since been introduced. Pre-adjusted brackets, however, fail to address deviations from average tooth morphology and other treatment nuances. These are often tackled chairside by placing bends on arch wires [9-12] - bends that the SWA method was invented to prevent. Additionally, mechanical boundaries and imprecision of bracket placement can result in limitations to treatment. [13-15] All these inaccuracies may cumulate during the course of a treatment to increase treatment time, resulting in frustration and compromised results.

Technological advancements have allowed for some customization of brackets and wires in order to address limitations of conventional pre-adjusted bracket systems. Digital intra-oral scans are obtained at the onset of treatment to generate a digital study model of the dentition. Virtual models are analyzed to determine the ideal position of each tooth required for achieving stable occlusion. Those digital models also allow for bracket positioning set-up; indirect-bonding transfer jigs allow virtual positioning to be replicated intra-orally. The clinician creates a virtual design of the final occlusion and alignment using computer-assisted technology, with reverse-engineered brackets and archwires used to obtain the intended result. Bracket slots are customized to accommodate a straight wire that moves each tooth to the ideal final position as identified by the virtual setup. Virtual bracket positions are then transferred to the patient by means of indirect-bonding transfer jigs [16].

Several orthodontic systems implement some of these new technologies, [17] providing the orthodontist with a treatment package consisting of digital diagnostics, 3-dimensional (3D) digital planning, and computer-designed customized brackets and arch wires. One such system is the Insignia (ORMCO Corporation) system [18], which entered the market several years ago. Theoretically, individualized orthodontic treatment systems offer several advantages for both the patient and orthodontist, with commonly mentioned benefits including better treatment results, shorter treatment duration, and less chair time. [19] Manufacturers utilizing virtual treatment planning and customized, computer-aided fabrication of tooth supported orthodontic appliances claim to deliver superior quality and efficiency of care compared to conventional preadjusted bracket systems. To date, few studies have investigated the accuracy of these systems in achieving their virtually planned tooth positions.