ACCURATE ORTHODONTIC BRACKETS POSITIONING WITH OR WITHOUT DENTAL MAGNIFYING LOUPES

Interventions

This was a two-arm parallel, singe-centre randomised study where the patients that have been treatment planned were randomised into two groups according to the block pattern:

Group NL: Bonding of the orthodontic brackets without dental loupe Group L: Bonding of the orthodontic brackets with dental loupe After extraction procedure was performed according to treatment plan. Within a week, the patient's teeth were dried before taking an intraoral scan with an intraoral scanner 3Shape TRIOS, Copenhagen, Denmark. After scanning the upper and lower arches, the teeth images were stored in STL file. STL file is a format commonly used for 3D printing and computer-aided design (CAD).

The STL file of each patient upper and lower arches were exported and printed into model by the 3D printer by digital dental laboratory to allow extraoral bracket positioning. The extraoral bracket positioning on the twenty 3D printed models were the gold standard for the eighteen patients respectively.

Once the gold standard for individual patient was generated, the bond up session was scheduled within a week time, a new set of brackets were placed by MJHS on the patient's maxillary and mandibular right to left premolars. Bonding of the brackets was performed according to the manufacturer's instructions. Dental loupes Zumax DFK Angled Loupe with a magnification of x3.0 and focus depth of 42cm was used. For the patients bond up by direct eye vision or using dental loupes, the brackets were positioned in the centre of mesial-distal dimension and aligned with the long axis of the crown. No over-correction of the bracket positioning was done to correct specific malocclusions, rotation, or tipping problems. After 40s light-curing of the composite according to manufacturer instructions. The bracket bonding was performed by MJHS in all patients to avoid inter-operator errors.

After bracket bonding, the postoperative dentitions was dried, and scanned with intraoral scanner for T2 by MJHS. Independent assistant (MM) coded the patients scanned STL files which were preoperative (3D images of T1 as gold standard) and postoperative 3D images as a pair without the knowledge of the principal investigator. The software identified 4 identical points on the same teeth from each pair of files and align for superimposition. The different bracket position was shown on the computer's screen in different colours. The differences in mesio-distal (MD) and occlusal-gingival (OG) dimensions, as well as mesio-distal angulation (MDang) dimensions were measured at magnification x10 of superimposition.

To measure the difference in bracket placement between the 2 methods employed the comparison between file preoperative and file postoperative, positive and negative signs were used for distances (distal: +; mesial: -; gingival: +; occlusal: -) and angulation (distal: +; mesial: -). Measurements included all the teeth in the inclusion criteria (Mohammadi \& Moslemzadeh, 2011; Panayi et al., 2020).

After the last 0.018" NiTi archwire for full expression of alignment archwire, the patients' teeth again scanned to assess the alignment of the teeth, T3. A crowding score based on the mesio-distal width for the maxillary and mandibular teeth will be measured in millimeters at T3 compared to T2 in relation to the line of arch that reflects the majority of teeth (Kirschen et al., 2000). The alignment of the patients' teeth with be categorized using Little's Irregularity Index into five categories based on a numerical score: 0 indicates perfect alignment, 1-3 is minimal irregularity, 4-6 is moderate irregularity, 7-9 is severe irregularity, and 10 or more is very severe irregularity. This index quantifies the degree of anterior crowding by measuring the sum of linear displacements (mm) of anatomical contact points of six anterior teeth. Any bracket that dislodged from the teeth was bonded back and kept in record. Bracket off was bonded according to the intervention the patient received. The leveling and alignment phase was considered accomplished when 0.019x0.025-inch stainless steel (SS) wire could be inserted without applying an exaggerated force (Al-Ibrahim et al., 2023). The dropout criteria was defined BPE score more than 2.