Abstract
The present study aimed to investigate the impact of hardness from 3D printed transfer trays and dental crowding on bracket bonding accuracy. Lower models (no crowding group: Little’s Irregularity Index (LII) < 3, crowding group: LII > 7, n = 10 per group) were selected at random, digitized, 3D printed, and utilized for semiautomated virtual positioning of brackets and tubes. Hard and soft transfer trays were fabricated with polyjet printing and digital light processing, respectively. Brackets and tubes were transferred to the 3D printed models and altogether digitized using intraoral scanning (IOS) and microcomputed tomography (micro-CT) for assessment of linear and angular deviations. Mean intra- and interrater reliability amounted to 0.67 ± 0.34/0.79 ± 0.16 for IOS, and 0.92 ± 0.05/0.92 ± 0.5 for the micro-CT measurements. Minor linear discrepancies were observed (median: 0.11 mm, Q1–Q3: −0.06–0.28 mm). Deviations in torque (median: 2.49°, Q1–Q3: 1.27–4.03°) were greater than angular ones (median: 1.81°, Q1–Q3: 1.05°–2.90°), higher for hard (median: 2.49°, Q1–Q3: 1.32–3.91°) compared to soft (median: 1.77°, Q1–Q3: 0.94–3.01°) trays (p < 0.001), and torque errors were more pronounced at crowded front teeth (p < 0.05). In conclusion, the clinician should carefully consider the potential impact of hardness and crowding on bracket transfer accuracy, specifically in torque and angular orientation.
Highlights
For orthodontic treatment of malocclusions, the insertion of fixed multibracket appliances is a common and reliable treatment option
In the classical indirect bonding technique, brackets are positioned on plaster models and transfer templates are fabricated in the laboratory [12,13], which are frequently made of single- or double-layer silicones, vacuum-formed sheets of various thicknesses or a combination of both [14,15,16,17,18]
Different procedures for digitizing study models, e.g., an intraoral on scanning accuracy and could affect outcomes achieved with this techscanners, 3D-model scanners or cone beam computed tomography (CBCT), were described nology
Summary
For orthodontic treatment of malocclusions, the insertion of fixed multibracket appliances is a common and reliable treatment option. Since the introduction of the straight-wire technique, ideal positioning of bracket has become of eminent importance [1,2,3,4,5]. Positioned brackets can lead to undesirable tooth movement and extended treatment time. Instead of chairside positioning (direct bonding), ideal bracket positions can be planned prior to treatment (indirect bonding). This approach was first described by Silverman and Cohen in 1972 [6] and has the advantage of unrestricted vision, reduced chair time, and increased patient comfort [7].
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