Transfer accuracy of vinyl polysiloxane trays for indirect bonding

Abstract

Objective: To elicit the magnitude, directional bias, and frequency of bracket positioning errors caused by the transfer of brackets from a dental cast to the patient's dentition in a clinical setting. Materials and Methods: A total of 136 brackets were evaluated. The brackets were placed on dental casts and scanned using cone beam computed tomography (CBCT) to capture 3-D positioning data. The brackets were then transferred to the patient's dentition with an indirect bonding method using vinyl polysiloxane (VPS) trays and later scanned using CBCT to capture the final bracket positioning on the teeth. Virtual models were constructed from the two sets of scan data and digitally superimposed utilizing best-fit, surface-based registration. Individual bracket positioning differences were quantified using customized software. One-tailed t tests were used to determine whether bracket positioning was within limits of 0.5 mm in the mesiodistal, buccolingual, and vertical dimensions, and 2u for torque, tip, and rotation. Results: Individual bracket positioning differences were not statistically significant, indicating, in general, final bracket positions within the selected limits. Transfer accuracy was lowest for torque (80.15%) and highest for mesiodistal and buccolingual bracket placement (both 98.53%). There was a modest directional bias toward the buccal and gingival. Conclusion: Indirect bonding using VPS trays transfers the planned bracket position from the dental cast to the patient's dentition with generally high positional accuracy. (Angle Orthod. 2016;86:468-474.)

Accurate bracket placement using a computer-aided design and computer-aided manufacturing–guided bonding device: An in vivo study

“…In recent years, a variety of devices or transfer trays have been developed to accurately transfer the ideal bracket placement to patients' dentitions. 2,4,[6][7][8][9]12,13,[15][16][17] However, the effectiveness of such devices might be questioned without proper procedures for precise control and prediction of possible complications. Based on the 3D assessment, we found that the protocol in this study allowed accurate transfer of bracket placement.…”

“…With the advance of digital technology, 3D assessment using the scanned model has been proposed to be more accurate than 2D assessment using digital photography. 5,[13][14][15]18 In this study, a semiautomated 3D measurement in Geomagic Studio 2013 was used to measure the position and orientation deviations for 205 brackets. Because the local coordinate system had been prelocated on the bracket, there was no need to identify the corresponding reference points on the teeth from different patients repeatedly.…”

“…2,4,[6][7][8]19,20 However, errors may occur because of fabrication errors, contaminants or involvement of soft tissue, varied thickness of the bonding materials, limited access to hold the transfer tray in the posterior region, or varying finger pressure on the tray. 13,16 This technique requires a significant learning curve and much experiences to assess whether the transfer tray is accurately fabricated and fits the dentitions well before Mean, Mean value of error N; SD, standard deviation. *n is number of brackets used for analysis; y Positive values indicate a postoperative position more mesial, buccal, gingival, or with more lingual crown torque, more distal angulation, or a lingual surface rotated more mesially than in the simulative position.…”

“…use, as well as to control the transfer tray in complete seating and the bracket in the predetermined position during the bonding in vivo. 13,16,21,22 With the advance of digital technology in indirect bonding techniques, it is possible to fabricate the transfer tray efficiently and accurately with rapid prototyping, to optimize bracket position on software, as well as to facilitate communications among doctors, technicians, and patients. [9][10][11][12]14 There are 2 major types of transfer trays fabricated using digital techniques.…”

“…However, the elastic property of most transfer trays makes it difficult to differentiate among incomplete seating, complete seating, and over seating of the transfer tray for each single tooth when individualized finger pressure is applied. 13 Moreover, because the brackets are partially or completely covered by the transfer tray, there is a lack of visibility, making it difficult to tell whether the bracket is in the predetermined position, as well as limiting access to adjust the bracket position or remove the excess adhesive immediately. [9][10][11] Thus, transferring the bracket position to the patient's dentition with accuracy is challenging for orthodontists with limited experience, especially on dentitions with various malocclusion and intraoral complications.…”