The goal of orthodontic treatment is to achieve an exemplary treatment outcome in a reasonable amount of time. Orthodontic treatment should be not only effective, but also efficient in terms of total treatment time and number of appointments. A critical component of achieving these goals is an optimal orthodontic bracket placed in the ideal position on each tooth.

Nearly 40 years ago, Andrews developed the first true straight-wire appliance. Andrews’ brackets had specific first-, second-, and third-order prescriptions for each tooth; this increased the consistency of the treatment results and improved the treatment efficiency because fewer bends were required in both aligning and finishing archwires. Many straight-wire bracket prescriptions are now available, all with a common goal of shortening the aligning and finishing stages of orthodontic treatment by minimizing the amount of wire bending.

A critical element in the success of any straight-wire appliance is that each bracket must be accurately positioned on every tooth in the arch; however, this is clinically difficult because of anatomic variations in tooth morphology and human error. Balut et al completed a study on direct bonding accuracy, analyzing brackets placed on dental casts mounted in mannequins, and found significant differences in both vertical positioning and angulation of the appliances. Interestingly, removing clinical obstacles such as patient management, isolation control, and visualization difficulties did not eliminate bonding errors by experienced clinicians.

To decrease direct bonding errors and doctor chairside time during bonding appointments, there has been much experimentation with laboratory-fabricated indirect bonding trays. Many materials have been used for the indirect delivery system, including polyvinyl siloxane, prosthodontics putties, silicone gels, and thermoplastic trays. The objective of laboratory-fabricated indirect bonding protocols is to easily and accurately place brackets extraorally on a handheld model and then precisely transfer the ideally placed brackets to the patient’s teeth. Indirect bonding techniques have shown good bond strength; however, the accuracy of the technique has had varying success in several investigations. Koo et al found minimal improvements in accuracy with laboratory-fabricated indirect bonding techniques compared with direct bonding; both failed to execute ideal bracket placement. In addition to inaccurate bracket placement and variations in tooth anatomy, Creekmore and Kunik cited variations in vertical and anteroposterior jaw relationships, tissue rebound, and inherent mechanical deficiencies of edgewise orthodontic appliances as other factors that must be addressed in the development of an actual “straight-wire” orthodontic appliance.

Computer-aided design and computer-aided manufacturing (CAD/CAM) have been a focus of dental research since the 1980s to minimize human error in dentistry. Traditionally, much of the dental utilization of CAD/CAM technology has focused on the milling of crowns and fixed partial dentures. Dental applications of CAD/CAM have expanded in recent years as the benefits of the technology have been realized in new applications. Current uses of CAD/CAM technology in orthodontics include aids for diagnosis and treatment planning, clear aligner therapies, custom labial and lingual systems, and titanium Herbst appliances. Customized brackets with patient-specific torque, machine-milled indirect bonding jigs, and robotically generated archwires are among recent CAD/CAM advances in achieving a true straight-wire appliance. The overarching goal of incorporating CAD/CAM technology into orthodontics can be best summed up as “improving reproducibility, efficiency, and quality of orthodontic treatment.”

The applications of CAD/CAM in orthodontics are undoubtedly growing; unfortunately, the clinical evidence to support the applications of the technology has not kept pace. Manufacturers of customized orthodontic appliances delivered with milled indirect bonding jigs claim that these appliances reduce total treatment time, improve treatment efficiency, and yield better overall treatment results. However, many of these claims are unsubstantiated by scientific evidence. Weber et al investigated a commercially available CAD/CAM orthodontic system comparing treatment effectiveness and efficiency of the customized appliances to traditional twin appliances. The study reported significantly lower American Board of Orthodontic (ABO) scores, fewer archwire appointments, and shorter overall treatment times in the CAD/CAM group. Although these findings are promising, the study did not distinguish whether the clinical benefits were due to indirect bonding in the CAD/CAM group or the actual customized brackets.

The aim of our study was to expand the existing CAD/CAM orthodontic appliance literature by comparing treatment effectiveness and efficiency of 3 systems: (1) direct bonded self-ligating brackets, (2) indirect bonded self-ligating brackets, and (3) indirect bonded CAD/CAM self-ligating brackets. The null hypothesis was there will be no difference in effectiveness or efficiency measures among the 3 treatment groups.

Statistical analysis

Statistical analysis was performed using SPSS software (version 22.0; IBM, Armonk, NY). The age distribution of the groups at the beginning of treatment is shown in Figure 1 . Age, ABO Discrepancy Index values, ABO Cast-Radiograph categorical values and overall scores, treatment duration (months), and number of treatment appointments did not pass normality testing; therefore, the Kruskal-Wallis test was used for statistical analysis. The Benjamini-Hochberg test was then applied to control for the false discovery rate. A multiple comparison test was used for the post hoc analysis.

Box plots comparing the ages of the 3 treatment groups. There was no statistical difference between the groups.