The Validity of Customized Orthodontic Bracket Set up

Introduction Treatment efficiency has become an increasingly important goal of orthodontic treatment, yet basic questions about the efficiency of bracket system remain. In contemporary preadjusted edgewise orthodontic appliance, the greatest challenge in the success of orthodontic therapy depends undoubtedly on the perfection in bracket design, prescription, and its positioning in addition to the orthodontist's skill and training. However, due to uneven and dissimilar tooth surface anatomy, the need for an accurate method of bracket positioning with pre-determined torque and angulation incorporated in the brackets according to the patients' need is of key importance.

Therefore, it is valuable to know, dose digital bracket setting offers better outcomes? Previously, indirect bracket positioning technique was done using plaster dental cast where kesling setting (teeth alignment) made using the clinical crown. However, recently digital technique was used to assess teeth setting and bracket positioning acknowledging root positioning using typodonts.

Null hypothesis:

There is no difference between the CAD/CAM brackets setting technique (Ormco© Insignia™ .022" twin brackets) and virtual (digital and manual) bracket setting technique regarding to treatment efficiency and root positioning.

Aim and Objectives: The aim of the present study is to compare the efficacy of the virtual digital / manual setup technique compared to indirect bonded CAD/CAM brackets (Insignia™ twin brackets) in terms of expression of bracket prescription and treatment outcome using American Board of Orthodontics (ABO) scoring.

Primary Objectives: The bracket positional accuracy between manual setup-model indirect bonding and digital-driven indirect bonding methods.

Secondary Objectives: Determine the incidence of bracket debonding rate. Methodology Study design: This study is a prospective randomized controlled trial, in which clinical evaluation of virtual setup (digital and manual) techniques versus CAD/CAM brackets (Ormco© Insignia™ .022" twin brackets) in terms of expression of bracket prescription and treatment outcome.

Sample size: All patients will be recruited from the multicenter with one operator. Prior to initiating recruitment, a convenient sample size will be recruited. Initially the effect size in the sense of Cohen's for the material effect will be determined based on a previous study to be about 0.69. It was determined that the current study would reach 0.80% power with a total sample size of 54 dental arches, given that the type I error is 0.05.

Methods: Patients fulfill the selection criteria are recruited at their case presentation appointment, and consent form will be obtained. All patients informed to take CBCT before and after orthodontic treatment. The 30 consecutive patients (10 in each group) will be divided randomly into the virtually digital (Maestro® 3D Ortho Studio software) setup, manual (Ray set® device) setup and the CAD/CAM digitally (insignia®) customized group.

In this study will be use orthodontic adhesive to customize twin brackets base (Discovery, Dentaurum, Ispringen, Germany) for both manual and digital (Maestro® 3D Ortho Studio software) groups and CAD/CAM brackets (Insignia™ twin brackets) for 3rd group. On the day of recruitment, a baseline (T0) three-dimensional (3D) intraoral scan (IOS) will be done for the CAD/CAM all groups.

Manual indirect bonding setups and digital setups will be processed, as will be described in the laboratory setting section, for all teeth apart of the second molars according to previous study and verified using an objective grading system (OGS) of American Board of Orthodontics (ABO), which is currently the gold standard for evaluating plaster casts of completed orthodontic cases. In the ABO-OGS, there are eight criteria, seven of which are occlusal (tooth alignment, vertical positioning of marginal ridges, overjet, occlusal relationship, buccolingual inclination of posterior teeth, occlusal contacts, and interproximal contacts) that assess on plaster models to evaluate a patient's final occlusion. The remaining last criteria is root angulation measured on CBCT. After setups approval, indirect bonding trays or jigs will be constructed and divided randomly to the patients. After completion of bonding, an intraoral scanner will be taken to compare the bracket positioning.

Each patient received the same treatment protocol i.e., wire gauges and visiting intervals, type of ligation and finishing procedure. At the time of bracket bonding the patients will undergo an intraoral scan for the 1st and 2nd group (T1). At the working phase a 0.019*0.25 stainless steel wire will be inserted for 8 weeks, and the patients will undergo an intraoral scan (T2) and sent for CBCT.

No stopping guidelines will be specified, since subjects were receiving the same treatment materials as they would receive as part of standard care of clinical treatment. Bracket types will not blind in this study, since clear visual difference exists between the two bonding techniques, however, after bonding the treatment will be double blind for person who work on the superimposing software and statistician.

After obtaining all intraoral scans, Best-fit superimpositions will be performed depending on palatal rugae, which have been shown to be stable landmarks for the upper arch while in the lower arch, second molars (which were not engaged with Arch-wires) are used as stable landmarks.

• ST GROUP: Manually bracket base customization:

In the first group of this study, the stone dental cast will undergo to step wise procedure in bracket positioning and fabricating an indirect bonding tray for labial orthodontics using the Ray set device®:

• ND GROUP: Software-driven indirect bonding Set-Up: The dental arch will undergo to a digital scanning procedure by intraoral scanner. After scanning, the digital models are sending to software-driven bracket placement.
• RD GROUP: Insignia TM system:

The Approver Guide provides a suggested process for reviewing your Insignia cases. Having a systematic approach should save time, improve consistency, and help you manage cases more efficiently.

Scanning final Bonded Bracket positions: The final bonded bracket positions will be scanned with the intraoral scanner for the 1st and 2nd groups. This scan acquired the exact locations of the brackets bonded to the patient's teeth. This acquired image of the final bracket position will be superimposed with the initial virtual model in order to compare the bonding accuracy of the evaluated methods.

Superimposition of the digitized models: The STL files of the brackets placed using the Maestro® 3D Ortho Studio software will be exported along with the STL files of the scans of the brackets bonded intraorally.

The superimposition process consisted of defining, manually, three points for each model to superimpose (tripod), along with a precise automatic system that allowed the alignment and superimposition of the selected three points of reference. Lastly, the software will identify differences in bracket placement between the two different indirect bonding systems.

Methods of measurement before and after indirect bonding transfer:

The Geomagic control X software was used to measure the mesio-distal translation difference (in mm), the bucco-lingual translation difference (mm) and the occluso-gingival translation difference (mm) between the virtually planned brackets (STL files from the Maestro® 3D Ortho Studio software) and the brackets bonded intraorally (STL files from the intraoral scans). Each virtually planned bracket will be aligned with the origin of the three-dimensional coordinate system at the center-point of an imaginary rectangle constructed on the profile of the bracket's four wings and with the z-axis passing through the long axis of the bracket and the x-axis passing through the center of the bracket's slot.

The same method is used for the intraorally scanned brackets, where center-point Zero will be maintained as the point of reference. On the two superimposed brackets, the mesio-distal translation difference is measured by calculating the distance between the z-axis of the virtually planned bracket with a point passing perpendicular to the z-axis of the bracket scanned intraorally. In the same way, the occluso-gingival translation difference will be measured by calculating the distance between the x-axis of the virtually planned bracket with a point passing perpendicular to the x-axis of the bracket scanned intraorally.

To measure the bucco-lingual difference, the virtually planned bracket will be aligned with center-point Zero of an imaginary rectangle constructed on the profile of the two bracket wings, with the y-axis perpendicular to the long axis of the bracket, and the x-axis passing through the center-point of the rectangle, parallel to the slot base. On the basis of the two superimposed brackets, the bucco-lingual difference is measured by calculating the difference between the x-axis of the virtually planned bracket and an orthogonal point passing through the x-axis of the bracket scanned intraorally.

Evaluation of mesiodistal tip and labiolingual torque outcomes of manually and virtual-driven orthodontic appliances:

• A pre-treatment digital model (pre-model) =pre-treatment IOS for clinical crown with pre-treatment CBCT scan and a post-treatment digital model (post-model) = post-treatment IOS for clinical crown with post treatment CBCT scan of a patient will be retrieved from the database.

The virtual model resulting from the pre-CBCT/pre-model superimposition represents the "expected root position" (ERP) setup; it is defined as a prediction of the three-dimensional position of the roots after the orthodontic treatment

• The virtual model resulting from superimposing and combining the post-CBCT, and the post-model represents the "true root position" (TRP) setup, as the post-CBCT depicts the three-dimensional position of the roots.
• Each tooth isolated from the pre-treatment digital model (pre-model) is individually exported using the STL file format, in order to be superimposed independently onto the post-treatment digital model (post-model) by using software ''best fit alignment'' to overlay the teeth. Color code representing differences between the setup models.
• In order to assess the accuracy of the iterative closest point superimposition, color maps are generated to visualize the distribution and the extent of the changes occurred between ERP and TRP.
• The ERP and TRP STL files are then imported into software to calculate angular distances between ERP and TRP. Reference landmarks in linear measurements will be identified on the root apexes of incisors and canines; the buccal root is evaluated for premolars, the palatal root for maxillary molars, and the distal root for lower molars. The center of the angle between the root apexes of the ERP and the TRP will be identified on the crown of the post-model; it is located on the mesial incisal edge of incisors, on the tip of the vestibular cusp of canines and premolars, on the tip of the mesial cusp of maxillary molars, and on the tip of the distal cusp of mandibular molars.

Statistical Analysis:

Descriptive statistics will be presented, and data distribution will be assessed. Accordingly parametric and nonparametric statistics will be used. A P-value of <0.05 will be set to define the statistical level. Intra-observer error will calculate using an Intra-class Correlation Coefficient (ICC).

Inclusion criteria

• Class 1 malocclusion.
• Non-extraction treatment plan.
• Initial Little Index between 5-10 mm.
• Presence of all permanent teeth.

Exclusion criteria

• Any systemic diseases such as diabetes, hypertension.
• Sound or clicking in temporomandibular joint or craniofacial syndromes.
• Periodontal disease or pockets greater than 4mm.
• Incisor mandibular plane angle (IMPA) ≥ 100 degrees; or any anterior tooth completely blocked from the arch form