ABSTRACT

Objective

To evaluate the accuracy of three different digital bracket positioning systems, comparing vertical, mesiodistal and buccolingual accuracy.

Material and Methods

The same case was sent to Orapix, Insignia, and Orthocad systems and the brackets were bonded to the malocclusion models.Damon 3 MX brackets were used with all systems and the brackets were bonded to the models with the same bonding protocol and materials. The comparison of the position of each single bracket was made with digital photography, and ImageJ software was used to find the length in pixels and then convert it to hundredths of a mm for vertical, mesiodistal and buccolingual displacement, compared to the setup.

Results

Insignia System reported the average higher vertical displacement (0.28 mm), compared with the other two appliances (0.22-0.23 mm), and showed the lowest average displacement for the mesiodistal and buccolingual positioning (0.14 and 0.07 mm, respectively).However, these slight bracket positioning variations between these bonding systems were not statistically different (p>0.05).

Conclusion

The three systems analyzed were shown to be accurate in positioning the brackets, and none of them was statistically better.

Keywords:
Orthodontics; Orthodontic Brackets; Orthodontics, Corrective

Introduction

Modern technologies are increasingly widespread on the market that promise an increase in orthodontic treatments’ quality and efficiency [¹[1] Arreghini A, Lombardo L, Mollica F, Siciliani G. Torque expression capacity of 0.018 and 0.022 bracket slots by changing archwire material and cross section. Prog Orthod 2014;15(1):53. https://doi.org/10.1186/s40510-014-0053-x
https://doi.org/10.1186/s40510-014-0053-... ,²[2] Arreghini A, Trigila S, Lombardo L, Siciliani G. Objective assessment of compliance with intra- and extraoral removable appliances. Angle Orthod 2017;87(1):88-95. https://doi.org/10.2319/020616-104.1
https://doi.org/10.2319/020616-104.1... ].For example, today it is possible to create an interactive 3D treatment plan from digital models to virtual setup up to assisted positioning.

The literature showed some advantages for orthodontists [³[3] Bootvong K, Liu Z, McGrath C, Hägg U, Wong RW, Bendeus M, et al. Virtual model analysis as an alternative approach to plaster model analysis: reliability and validity. Eur J Orthod 2010;32(5):589-95. https://doi.org/10.1093/ejo/cjp159
https://doi.org/10.1093/ejo/cjp159... ]. There is the possibility in the software of carrying out a diagnostic setup, simulations of virtual extractions [⁴[4] Lombardo L, Stefanoni F, Mollica F, Laura A, Scuzzo G, Siciliani G. Three-dimensional finite-element analysis of a central lower incisor under labial and lingual loads. Prog Orthod 2012;13(2):154-63. https://doi.org/10.1016/j.pio.2011.10.005
https://doi.org/10.1016/j.pio.2011.10.00... ,⁵[5] Lombardo L, Scuzzo G, Arreghini A, Gorgun O, Ortan YO, Siciliani G. 3D FEM comparison of lingual and labial orthodontics in en masse retraction. Prog Orthod 2014;15(1):38. https://doi.org/10.1186/s40510-014-0038-9
https://doi.org/10.1186/s40510-014-0038-... ], indirect and direct computer-assisted bonding [⁶[6] Perrini F, Lombardo L, Arreghini A, Medori S, Siciliani G. Caries prevention during orthodontic treatment: In-vivo assessment of high-fluoride varnish to prevent white spot lesions. Am J Orthod Dentofacial Orthop 2016;149(2):238-43. https://doi.org/10.1016/j.ajodo.2015.07.039
https://doi.org/10.1016/j.ajodo.2015.07.... ]. There is the possibility to send images and files via e-mail; and the ability to instantly retrieve patient records from a database and view it on a screen instead of having to retrieve them from a physical archive.Economically, orthodontists need less space for the occupation of areas dedicated to the plaster models collection. Digital model cast can be stored indefinitely, and it could be useful for the resolution of the medico-legal problem [⁷[7] Asquith J, Gillgrass T, Mossey P. Three-dimensional imaging of orthodontic models: a pilot study. Eur J Orthod 2007;29(5):517-22. https://doi.org/10.1093/ejo/cjm044
https://doi.org/10.1093/ejo/cjm044... ].

Three-dimensional analysis of tooth movements is also possible in multidisciplinary cases [⁸[8] Lopez MA, Andreasi Bassi M, Confalone L, Gaudio RM, Lombardo L, Lauritano D. The influence of conical plus octagonal internal connection on implant survival and success rate: a retrospective study of 66 fixtures. J Biol Regul Homeost Agents 2016;30(2 Suppl 1):49-54.–¹⁰[10] Lopez MA, Andreasi Bassi M, Confalone L, Gaudio RM, Lombardo L, Lauritano D. Clinical outcome of 215 transmucosal implants with a conical connection: a retrospective study after 5-year follow-up. J Biol Regul Homeost Agents 2016;30(2 Suppl 1):55-60.]. It has been verified that the data obtained in the evaluation of dental movements through the superimposition of virtual models are superimposable to those obtained from the cephalometric examination. Furthermore, considering the palatine wrinkles [¹¹[11] Lombardo L, Gracco A, Zampini F, Stefanoni F, Mollica F. Optimal palatal configuration for miniscrew applications. Angle Orthod 2010;80(1):145-52. https://doi.org/10.2319/122908-662.1
https://doi.org/10.2319/122908-662.1... ,¹²[12] Gracco A, Luca L, Cozzani M, Siciliani G. Assessment of palatal bone thickness in adults with cone beam computerised tomography. Aust Orthod J 2007;23(2):109-13.], as a stable area for the upper arch, it is possible to visualize the dental movements in three dimensions, instead of two-dimensionally, as happens for the superimposition of two cephalometrics.

By digital technologies, the orthodontist can count on virtual setups to make malocclusion treatment more predictable, also considering the force released by the lips [¹³[13] Di Fazio D, Lombardo L, Gracco A, D'Amico P, Siciliani G. Lip pressure at rest and during function in 2 groups of patients with different occlusions. Am J Orthod Dentofacial Orthop 2011;139(1):e1-6. https://doi.org/10.1016/j.ajodo.2010.02.030
https://doi.org/10.1016/j.ajodo.2010.02.... ]. In addition, the setup allows to evaluate the need for extractions, overcorrections, or interproximal reduction and facilitates communication with the patient by showing the risk [¹⁴[14] Lombardo L, Carinci F, Martini M, Gemmati D, Nardone M, Siciliani G. Quantitive evaluation of dentin sialoprotein (DSP) using microbeads - a potential early marker of root resorption. Oral Implantol 2016;9(3):132-42. https://doi.org/10.11138/orl/2016.9.3.132
https://doi.org/10.11138/orl/2016.9.3.13... ,¹⁵[15] Lombardo L, Toni G, Stefanoni F, Mollica F, Guarneri MP, Siciliani G. The effect of temperature on the mechanical behavior of nickel-titanium orthodontic initial archwires. Angle Orthod 2013;83(2):298-305. https://doi.org/10.2319/040612-287.1
https://doi.org/10.2319/040612-287.1... ]and the benefit of the treatment a priori.However, to date, there is no clarity in the literature on the actual accuracy of the transfer methods adopted by the various systems for the transition from indirect bonding to the patient’s arches.As prescribed by the different manufacturers, Insignia and Orthocad used single jigs united in groups (3 per arches) while Orapix used transfer trays in Memosil.

Recently, computer-aided design and computer-aided manufacturing (CAD/CAM) systems have been developed for indirect bonding. These processes involve designing a digital model in a CAD/CAM program to produce a transfer jig. The CAD/CAM transfer jig improves the bonding of the bracket to the target tooth [¹⁶[16] Mayhew MJ. Computer-aided bracket placement for indirect bonding. J Clin Orthod 2005;39(11):653-60.–¹⁸[18] Garino F, Garino GB. Computer-aided interactive indirect bonding. Prog Orthod 2005;6(2):214-23.].

Accurate bracket positioning has a great influence on the result of orthodontic treatment [¹⁹[19] Czolgosz I, Cattaneo PM, Cornelis MA. Computer-aided indirect bonding versus traditional direct bonding of orthodontic brackets: bonding time, immediate bonding failures, and cost-minimization. A randomized controlled trial. Eur J Orthod 2021;43(2):144-51. https://doi.org/10.1093/ejo/cjaa045
https://doi.org/10.1093/ejo/cjaa045... ,²⁰[20] Pottier T, Brient A, Turpin YL, Chauvel B, Meuric V, Sorel O, et al. Accuracy evaluation of bracket repositioning by indirect bonding: hard acrylic CAD/CAM versus soft one-layer silicone trays, an in vitro study. Clin Oral Investig 2020;24(11):3889-97. https://doi.org/10.1007/s00784-020-03256-x
https://doi.org/10.1007/s00784-020-03256... ]. In literature, the articles analyzed the differences between the different methods: direct, traditional indirect and computer-aided indirect bonding.The accuracy is indicative of the repeatability of the positioning of the brackets in the same position on the tooth surface [¹⁹[19] Czolgosz I, Cattaneo PM, Cornelis MA. Computer-aided indirect bonding versus traditional direct bonding of orthodontic brackets: bonding time, immediate bonding failures, and cost-minimization. A randomized controlled trial. Eur J Orthod 2021;43(2):144-51. https://doi.org/10.1093/ejo/cjaa045
https://doi.org/10.1093/ejo/cjaa045... ,²⁰[20] Pottier T, Brient A, Turpin YL, Chauvel B, Meuric V, Sorel O, et al. Accuracy evaluation of bracket repositioning by indirect bonding: hard acrylic CAD/CAM versus soft one-layer silicone trays, an in vitro study. Clin Oral Investig 2020;24(11):3889-97. https://doi.org/10.1007/s00784-020-03256-x
https://doi.org/10.1007/s00784-020-03256... ].

The purpose of this study was to evaluate the accuracy of different digital bracket positioning systems, comparing vertical, mesiodistal, and buccolingual accuracy of bracket positioning.

Material and Methods

Study Design and Sample

This is a comparative study. The test patient was an adult 30.4 years old, showed a permanent dentition, brachyfacial skeletal pattern, molar and canine Class I malocclusion, and the anterior teeth were slightly crowded.

Data Collection

For the test patient, impressions were taken with the “double impression technique” in polyvinyl siloxane and sent to the Orapix (Orapix Co., Ltd, Seoul, Korea), Insignia (Ormco Corporation, Glendora, CA, USA) and Orthocad (Cadent Inc., Carlstadt, NJ, USA) systems.The bonding requirement was standard for all digital systems so as not to have great differences in positioning between one system and another (Figures 1 to 3).

In any case, the analysis focused on the differences in the positioning of the brackets present between a given system and the application of that system in reality.

The same brackets (Damon 3 MX, Ormco Corporation, Glendora, CA, USA) were used with all systems and were bonded to the models with the same bonding protocol and materials. The transfer bonding trays were similar between the different techniques: Insignia and Orthocad used single jigs united in groups (3 per arches) while Orapix used transfer trays in memosil (Memosil 2, Kulzer GmbH, Hanau, Germany).

The comparison of the position of each single bracket is made with digital photography, which must always be performed in the same position for each view.The model was photographed in occlusal, front, right and left lateral views and in each photo, it will have a millimeter film overlaid to allow to calibrate of the measurements. For this purpose, we used a digital reflex camera with a 105 mm macro lens suitable for intraoral photos. The machine was placed on a stand at the height of 50 cm and fixed with the lens perpendicular to the ground.The settings used were mode A, F32, exposure 1/60 s, distance 0.6 m, Flash yes, ISO 800.A graph paper was placed on the work base on which the references for the feet of the stand are drawn on the sides to be locked in a reproducible position (Figure 4).

Furthermore, two reference axes are traced on the paper: one transverse and one longitudinal in the center of the first.For the occlusal photo, the model is positioned with the median line superimposed on the longitudinal axis of the paper and a line passing through the mesiobuccal cusps of the sixths is superimposed on the transverse line on the paper.For the superior frontal photo, the disto-vestibular cusps are located 2.5 cm from the transverse reference line, and the median line is superimposed on the longitudinal axis of the paper.For the lower front photo, the disto-vestibular cusps are located 1 cm from the transverse reference line and again, the median line is superimposed on the longitudinal axis of the paper.

In an occlusal vision, the measurement of the mesiodistal position of the bracket is calculated as the distance between the line passing through the center of the tooth, found as equidistance from the contact points, and the line parallel to this passing through the center of the surface of the base of the bracket (Figure 5).

The measurement of the vertical position of the bracket is calculated as the distance between the incisal edge / occlusal edge of the tooth and the upper base of the bracket in front view (Figure 6). The upper base was taken as a reference in both arches because it was not covered by the door of the bracket.The buccolingual measurement is carried out in occlusal view: distance from the center of the buccal surface of the tooth to the surface of the bracket base measured for each tooth (Figure 7).ImageJ software was used to find the length in pixels and then convert it to hundredths of a mm.One thousand one hundred twenty-eight measures relating to three variables were totally analyzed, measuring over two times on 28 teeth. The measurements were made after the transfer of the brackets

Statistical Analysis

The model used allowed us to evaluate how the mask and time affect the level of the measured variable;therefore, the difference in positioning before and after the transfer of the brackets is statistically significant.The analysis of variance (ANOVA), F-Test, and Tukey test were also used. A second operator evaluated the measurement error (replicability). Performing a second systematic detection was necessary to evaluate the reproducibility error with the Dahlberg method, which turned out to be 0.02.Statistical analyzes were performed with SAS 9.2 Software (SAS Institute Inc., North Carolina, USA).

Ethical Clearance

The study design was reviewed and approved by the Ethics Committee of Postgraduated School of Orthodontics of Ferrara University (approval number 7/2015).

Results

The vertical, mesiodistal and buccolingual displacements with statistical data were shown in Tables 1 to 3.Insignia System reported the average higher vertical displacement (0.28 mm), compared with the other two appliances (0.22-0.23 mm), and showed the lowest average displacement for the mesiodistal and buccolingual positioning (0.14 and 0.07 mm, respectively).However, these slight bracket positioning mesiodistal and buccolingual variations between these bonding systems were not statistically different.The average displacements between setups and model bonded were statistically significant (p<0.05) only for the vertical measurements.

Discussion

Despite the clinical importance of accurate bracket placement, only a few studies have investigated the extent of errors committed in indirect bonding, not investigating digital systems. Balut et al. [²¹[21] Balut N, Klapper L, Sandrik J, Bowman D. Variations in bracket placement in the preadjusted orthodontic appliance. Am J Orthod Dentofacial Orthop 1992;102(1):62-7. https://doi.org/10.1016/0889-5406(92)70015-3
https://doi.org/10.1016/0889-5406(92)700... ] evaluated the precision of direct bonding and reported an average vertical error of 0.34 mm. It was described that it was easier for the orthodontist to correctly position the brackets on the lower incisors than on the other teeth. However, the major vertical errors were committed in the positioning of the bracket on the second upper premolar. On the other hand, the major axial errors were committed at the level of the upper incisors and the upper and lower canines. There were no statistically significant differences between the different operators. Consequently, they demonstrated the existence of an intrinsic "human" difficulty in correctly positioning the brackets directly.

Koo et al. [²²[22] Koo BC, Chung CH, Vanarsdall RL. Comparison of the accuracy of bracket placement between direct and indirect bonding techniques. Am J Orthod Dentofacial Orthop 1999;116(3):346-51. https://doi.org/10.1016/s0889-5406(99)70248-9
https://doi.org/10.1016/s0889-5406(99)70... ] compared the precision of indirect and direct bonding and showed that there was no statistically significant difference between the two groups, reporting a mean vertical error of 0.35 mm and a mean horizontal error of 0.19 mm compared to a third group that presented the ideal positioning of the brackets.

This study aimed to evaluate the effective accuracy of 3 digital assisted positioning systems for the brackets on the same patient. The displacements between planned and obtained brackets positions agreed with what is present in international scientific literature.

Hodge et al. [²³[23] Hodge TM, Dhopatkar AA, Rock WP, Spary DJ. A randomized clinical trial comparing the accuracy of direct versus indirect bracket placement. J Orthod 2004;31(2):132-7. https://doi.org/10.1179/146531204225020427
https://doi.org/10.1179/1465312042250204... ] performed a randomized clinical study on bracket placement: no statistically significant differences between the two groups reported a mean vertical error of 0.27 mm and a horizontal of 0.11 mm; the errors were greater in the upper arch than in the mandibular.Armstrong et al. [²⁴[24] Armstrong D, Shen G, Petocz P, Darendeliler MA. A comparison of accuracy in bracket positioning between two techniques - localizing the centre of the clinical crown and measuring the distance from the incisal edge. Eur J Orthod 2007;29(5):430-6. https://doi.org/10.1093/ejo/cjm037
https://doi.org/10.1093/ejo/cjm037... ] investigated the differences in accuracy between two vertical bracket placement methods.The first method consisted of visually identifying the center of the clinical crown (FA Point), while the second measured the distance from the occlusal margin using an altimeter. This second method proved more accurate and reproducible, especially for the anterior sector.There are several bonding methods described in literature [²⁰[20] Pottier T, Brient A, Turpin YL, Chauvel B, Meuric V, Sorel O, et al. Accuracy evaluation of bracket repositioning by indirect bonding: hard acrylic CAD/CAM versus soft one-layer silicone trays, an in vitro study. Clin Oral Investig 2020;24(11):3889-97. https://doi.org/10.1007/s00784-020-03256-x
https://doi.org/10.1007/s00784-020-03256... –²⁵[25] Silverman E, Cohen M. A report on a major improvement in the indirect bonding technique. J Clin Orthod 1975;9(5):270-6.].

Error in the printing of the transfer jig for a bracket would not be excluded after the setup by the 3D digital program. In addition, the jig could not cover the undercut of a bracket, and the elasticity of the jig would be less than that of silicone to make a free gap between the transfer jig and the bracket. These properties of the jig material could influence the accuracy of the bracket position.

Thanks to new digital technologies, today, the orthodontist can count on virtual set-ups that promise to make the treatment of malocclusion more predictable [²⁶[26] Thomas RG. Indirect bonding: simplicity in action. J Clin Orthod 1979;13(2):93-106.]. The set-up allows to evaluate the need for extractions, overcorrections or interproximal reduction and facilitates communication with the patient by showing the result of the treatment a priori [²⁷[27] McLaughlin RP, Bennett JC. Bracket placement with the preadjusted appliance. J Clin Orthod 1995;29(5):302-11.].However, to date, there is no clarity in the literature on the actual accuracy of the transfer methods adopted by the various systems for the transition from indirect bonding to the patient's arches.

The purpose of this study was to evaluate the effective accuracy of three digital assisted positioning systems for the brackets on the same patient to remove the inter-individual anatomical variability [²⁸[28] Kalange JT. Indirect bonding: a comprehensive review of the advantages. World J Orthod 2004;5(4):301-7.].The results show no perfect correspondence between the positioning of the brackets in the setup and the transfer on the teeth.However, the differences are small. They may partly depend on the operator, and it is not possible to prefer one of these systems over another regarding the accuracy of the positioning of the brackets.

The use of more advanced software for this analysis could help clarify the slightly incorrect positioning, even if the quality of the final result of the orthodontic case certainly depends more on the setup than on these three transfer systems, all very accurate [²⁹[29] Klocke A, Tadic D, Vaziri F, Kahl-Nieke B. Custom base preaging in indirect bonding. Angle Orthod 2004; 74(1):106-11.–³³[33] Kim J, Chun YS, Kim M. Accuracy of bracket positions with a CAD/CAM indirect bonding system in posterior teeth with different cusp heights. Am J Orthod Dentofacial Orthop 2018; 153(2):298-307. https://doi.org/10.1016/j.ajodo.2017.06.017
https://doi.org/10.1016/j.ajodo.2017.06.... ]. The results showed similar displacements of bracket positioning between different teeth; in fact, the accuracy of transfer trays systems should not be affected by the tooth anatomy.

Conclusion

Insignia, Orthocad, and Orapix systems are accurate in the bracket positioning methods. The differences in bracket positioning were minimal concerning the planned bracket positions and are statistically significant only for vertical displacements. The vertical displacement measures showed the highest errors in bracket positioning.

References

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