Comparison of the accuracy and reliability of bracket positioning during direct bonding in fixed orthodontic cases, with and without the use of magnification loupes: A split-mouth randomised controlled trial

B**ackground:**Accurate and consistent bonding of orthodontic brackets is incumbent on the clear visualisation of the tooth morphology and its relationship with the adjacent teeth. Using magnification loupes is a potentially beneficial manoeuvre that is gaining increased clinical adoption in dental procedures. However, its usefulness in improving the outcome of direct orthodontic bonding has not been investigated adequately. The present investigation is designed to objectively determine whether the use of dental loupes confers any measurable advantage in the accuracy and reliability of bracket placement compared to direct vision.

Participants: 23 individuals planned for fixed appliance treatment in the Orthodontic clinic of the Department of Dentistry, JIPMER, Puducherry.

**Procedure:**At baseline (T0), a full-arch intraoral digital scan will be obtained to plan the ideal bracket positions. The patient will be scheduled for the first bonding (T1 ) within 7 days of the T0 scan. The SNOSE covers will be opened to reveal the side and order allocation for the participant. All the teeth planned for bonding ( first molar to first molar in both arches) will be cleaned and polished with non-fluoridated prophylaxis paste. The surface will be rinsed with an air-water syringe for 10 seconds and dried with oil-free compressed air. The bonding process will start on the left or right maxillary quadrant, depending on the bonding order ( with or without loops) revealed by the random sequence. This will be followed by the mandibular arch on the same side, and then by the maxillary and mandibular quadrants of the other side in the same sequence. Within each quadrant, the bonding will start from the central incisor and finish with the first molar, followed immediately by the intraoral scan of the quadrant. To avoid enamel damage from subsequent debonding, all the brackets at T1 will be bonded without etching and without curing the light-cured orthodontic adhesive. At T2 ( minimum of 4 weeks after T1), the actual bonding of orthodontic brackets and the third intraoral scans will be performed. The procedure will be the same as in T1, except that the bonding process will now involve etching and curing the adhesive as in standard bonding protocol.

 Primary outcomes:

1.  Bracket Position Accuracy: the difference between bracket positions in T2 and T0, estimated using linear (differences in the x and y axes in mm) and angular ( differences in slot angulation in degrees) variables.

2.  Reliability of Bracket Positioning: the difference between bracket positions in T2 and T1, estimated using linear (differences in the x and y axes in mm) and angular ( differences in slot angulation in degrees) variables.

Secondary outcome:

3.   Time taken for bracket positioning – estimated as the time elapsed in seconds from the start of bracket positioning in the central incisor till the completion of bonding in each quadrant.

Outcome assessment will be done by the same investigator, blinded to the study groups.

Statistical analysis: The bracket positioning errors will be summarised with mean ± SD or median and IQR. Intergroup comparisons will be done using the Paired T test / Wilcoxon signed rank test. Subgroup analysis for all the outcome variables will be done based on the side of bonding (Right vs Left), Arch (Upper vs Lower) and teeth class (Anterior vs Posterior). Reliability will be calculated using the Intraclass Correlation Coefficient (ICC) and Bland-Altman plots. The reliability of the assessment method will be estimated using ICC.

**Clinical Implications:**The results of the study will help make recommendations for the routine use of magnification loupes during direct bonding of orthodontic brackets.