Transfer accuracy of 3D-printed trays for indirect bonding of orthodontic brackets:

ABSTRACT Objectives To evaluate the transfer accuracy of 3D-printed indirect bonding trays constructed using a fully digital workflow in vivo. Materials and Methods Twenty-three consecutive patients had their incisors, canines, and premolars bonded using fully digitally designed and 3D-printed transfer trays. Intraoral scans were taken to capture final bracket positioning on teeth after bonding. Digital models of postbonding scans were superimposed on those of corresponding virtual bracket setups, and bracket positioning differences were quantified. A total of 363 brackets were evaluated. One-tailed t-tests were used to determine whether bracket positioning differences were within the limit of 0.5 mm in mesiodistal, buccolingual, and occlusogingival dimensions, and within 2° for torque, tip, and rotation. Results Mean bracket positioning differences were 0.10 mm, 0.10 mm, and 0.18 mm for mesiodistal, buccolingual, and occlusogingival measurements, respectively, with frequencies of bracket positioning within the 0.5-mm limit ranging from 96.4% to 100%. Mean differences were significantly within the acceptable limit for all linear dimensions. Mean differences were 2.55°, 2.01°, and 2.47° for torque, tip, and rotation, respectively, with frequencies within the 2°-limit ranging from 46.0% to 57.0%. Mean differences for all angular dimensions were outside the acceptable limit; however, this may have been due to limitations of scan data. Conclusions Indirect bonding using 3D-printed trays transfers planned bracket position from the digital setup to the patient's dentition with a high positional accuracy in mesiodistal, buccolingual, and occlusogingival dimensions. Questions remain regarding the transfer accuracy for torque, tip, and rotation.

Three-Dimensional Digital Superimposition of Orthodontic Bracket Position by Using a Computer-Aided Transfer Jig System: An Accuracy Analysis

Accurate bracket placement is essential for successful orthodontic treatment. An indirect bracket bonding system (IDBS) has been developed to ensure proper bracket positioning with three-dimensional computer-aided transfer jigs. The purpose of this study was to investigate the accuracy of bracket positioning by a one-body transfer jig according to the tooth type and presence/absence of a resin base. In total, 506 teeth from 20 orthodontic patients were included in this study. After initial dental models were scanned, virtual setup and bracket positioning procedures were performed with 3D software. Transfer jigs and RP models were fabricated with a 3D printer, and brackets were bonded to the RP model with or without resin base fabrication. The best-fit method of 3D digital superimposition was used to evaluate the lineal and angular accuracy of the actual bracket position compared to a virtual bracket position. Although all the measurements showed significant differences in position, they were clinically acceptable. Regarding the tooth types, premolars and molars showed higher accuracy than anterior teeth. The presence or absence of a resin base did not consistently affect the accuracy. In conclusion, the proper application of IDBS should be performed considering the errors, and resin base fabrication might not be essential in ensuring high-accuracy IDBS.

Prototype of Augmented Reality Technology for Orthodontic Bracket Positioning: An In Vivo Study

To improve the accuracy of bracket placement in vivo, a protocol and device were introduced, which consisted of operative procedures for accurate control, a computer-aided design, and an augmented reality–assisted bracket navigation system. The present study evaluated the accuracy of this protocol. Methods: Thirty-one incisor teeth were tested from four participators. The teeth were bonded by novice and expert orthodontists. Compared with the control group by Boone gauge and the experiment group by augmented reality-assisted bracket navigation system, our study used for brackets measurement. To evaluate the accuracy, deviations of positions for bracket placement were measured. Results: The augmented reality-assisted bracket navigation system and control group were used in the same 31 cases. The priority of bonding brackets between control group or experiment group was decided by tossing coins, and then the teeth were debonded and the other technique was used. The medium vertical (incisogingival) position deviation in the control and AR groups by the novice orthodontist was 0.90 ± 0.06 mm and 0.51 ± 0.24 mm, respectively (p < 0.05), and by the expert orthodontist was 0.40 ± 0.29 mm and 0.29 ± 0.08 mm, respectively (p < 0.05). No significant changes in the horizontal position deviation were noted regardless of the orthodontist experience or use of the augmented reality–assisted bracket navigation system. Conclusion: The augmented reality–assisted bracket navigation system increased the accuracy rate by the expert orthodontist in the incisogingival direction and helped the novice orthodontist guide the bracket position within an acceptable clinical error of approximately 0.5 mm.

Organization of safe execution of works with the use of trapping nets

The organization of ensuring safe execution of building and assembly works when erecting and reconstructing buildings (structures) of various purposes based on the application of trapping nets to prevent industrial injuries in case of human or items falling from height is presented. Structural layout of a safety (catching) device with pivotally mounted brackets and a freely hanging net was considered. Appearing dynamic loads in case of items falling on trapping nets depending on impact acceleration were theoretically identified. It was found out that a trapping net with pivotally positioned brackets additionally reduces deceleration loads in relation to devices with rigidly fixed brackets and their use is more effective for cases of men falling with insignificant forward velocity. Bench and shop tests of trapping devices were carried out with the purpose of checking compliance of selected theoretical models, selection of developed options of designs and schematic diagrams, differentiation of reaction of capron and lavsan net materials from action of impulse loads. Test key results confirming matching of experimental data with presented theoretical models were showed. It was established that dynamic overloads depend both on a bracket position angle as well as on a place of an item falling into net, the value of pitch of deflection of net cloth made of lavsan and capron materials is almost similar and characteristics of values of their displacement under dynamic loads from a falling item are identical.

Development of New Method to Reposition Orthodontic Brackets Without Debonding by Using an Ultrasonic Device: An In Vitro Study

Objective: The purpose of this study was to develop a new method to change a bracket position without debonding the metal bracket that was bonded with a polymethyl methacrylate (PMMA) orthodontic adhesive resin by using an ultrasonic device. Materials and Methods: An originally designed scaler tip was developed for a piezoelectric ultrasonic scaler. The adhesive turned to melting state by thermal heat that was generated by ultrasonic frictional heat. When the adhesive was in melting state, the bracket was rotated approximately 20° and held in this position until the adhesive hardened again by air cooling. Shear bond strengths were measured on each sample in the control and the repositioning groups. To evaluate the thermal effects of the increased temperature on the enamel surface and pulpal cavity, extracted human lower premolars were monitored during the repositioning time. Results: The time required for the repositioning procedures was approximately 7 s. The temperature of the enamel surface increased by 53°C and the pulpal wall increased by 0.5°C during the repositioning procedures. The bonding strength showed no significant difference between the control and repositioning groups. Conclusion: This method for bracket repositioning without debonding using an ultrasonic device proved to be a new method for bracket repositioning.

Accuracy of Three Bracket Transfer Media for Indirect Bonding Techniques (IDB) Fabricated by Three-Dimensional Printing

To evaluate and compare the accuracy of bracket placement in three bracket transfer media techniques for indirect bonding. A total of 300 brackets were bonded on dental casts by indirect bonding techniques using three different bracket transfer media. The bracket positions were simulated by digital software. In the first two methods, digital models were designed with two types of markers, one with fully mocked up bracket (container method), and another with only marked bracket margins (marker method), then the models were printed out by a three-dimensional (3D) printer using pink resin and bracket transfer trays were vacuum formed on these models with polyvinylsiloxane. In the third methods, digital software was used to design full arch transfer trays, and printed by a stereolithographic 3D printer using elastic resin. With the transfer trays, the brackets were bonded onto dental stone casts, and a 3D model scanner was used to capture the final bracket positions on the casts. Superimpositions between the planned and actual bracket positions were done. Nonparametric statistical analyses were used to determine whether there were significant differences between planned and actual bracket positions and between the three methods. All significant differences in bracket position were less than 0.31 mm and most (95%) were less than 0.08 mm. Significant differences between all three methods were found. Indirect bonding methods using digital software combined with 3D printing show good accuracy with clinically insignificant positional discrepancies of less than 0.5mm.

The Influence of Smile Arc by Bracket Position Modification: A Prospective Clinical Study

Objective: The purpose of this study was to assess the effects of McLaughlin, Bennett, and Trevisi Bracket Positioning in patients with ideal smile arc and to assess the efficacy of McLaughlin, Bennett, and Trevisi by modifying anterior bracket position among patients with flat smile arc in pretreatment and postalignment phases. Methodology: A total of 30 subjects divided into 2 groups (group A: 15 subjects with ideal smile arc, and group B: 15 subjects with flat smile arc) were made to participate in this study. A flat smile arc was converted to an ideal smile arc in group B subjects by bracket position modification, and an ideal smile arc was maintained in group A subjects. While paired student t test was performed to find the level of significance in tip and torque values, Mann–Whitney test was used to find the mean difference in intercanine width and visual analogue scale. Results: Wilcoxon signed ranks test was used to determine the statistically significant changes observed in torque in relation to all the maxillary anteriors. The results showed that tip values in maxillary lateral incisors and torque values in maxillary canines of group B were statistically significant. Conclusion: A good amount of intrusion was seen in maxillary canines, which helped in the correction of the smile arc.

The effect of tooth morphology and vertical bracket positioning on resultant stress in periodontal ligament- a three dimensional finite element study

Introduction. The purpose of this study is to evaluate the effect of change in vertical placement of bracket and effect of tooth morphology on stress developed on periodontal ligament with the help of three dimensional finite element modeling. Methods. A three-dimensional model of the maxillary bone, maxillary right central incisor, lateral incisor and canine was designed based on the average dimensions of the anatomy and morphology given by Wheeler’s and standard edgewise bracket with Slot of 0.022″ X 0.028″ inch was designed using the finite element method. Brackets were placed on each tooth, on the mentioned labial surface at variable distances from the cusp tip, and a full size archwire was virtually engaged into the bracket, then optimum orthodontic load of 2N is applied and PDL stress were calculated. Results. The lowest stress values were measured as bracket position changes from crest of teeth to the apical direction. By displacing the bracket gingivally from 1.5 to 6 mm, a 16.2% decrease in stress level for central incisor, for lateral incisor the stress level decrease by 25.8% and for canine the stress level decrease by 21.6% thus our study confirms that variation in vertical bracket position results in change in resultant stress in PDL. Conclusion.It can be concluded that the variation in the vertical position of the bracket on different tooth can have an important effect on the stresses developed in the PDL.