Clinical expression of programmed maxillary buccal expansion and buccolingual crown inclination with Invisalign EX30 and SmartTrack aligners and the effect of 1-week vs. 2-week aligner change regimes: A retrospective cohort study.

Objective: : This retrospective cohort study aimed to assess and compare the accuracy of 3 different Invisalign® treatment regimens in terms of variations of aligner change frequency and type of aligner material in achieving maxillary dental buccal expansion. Methods: : Altogether, 120 adult patients whose treatment involved maxillary dental expansion with Invisalign® were included. The patients were divided into 3 groups, with each group comprising 40 patients as follows: SmartTrack® 1-week changes (ST1), SmartTrack® 2-week changes (ST2), and EX30® 2-week changes (EX2). The groups were assessed by comparing actual changes achieved with those prescribed by ClinCheck®. The rates of clinically significant inaccuracies (CSI) observed for buccal expansion (≥ 0.5 mm) and buccolingual inclination (≥ 2°) during expansion were then determined. Results: : In terms of expansion, the ST1 group demonstrated the highest CSI rate at all tooth levels, whereas the ST2 group had the lowest rate of CSI and the lowest mean inaccuracy for each tooth level. In terms of buccolingual inclination, the ST1 group had the highest CSI rate across all tooth levels, whereas the EX2 group had the lowest CSI rate at all tooth levels except for the canine level where the ST2 group had the lowest CSI rate. A tendency toward overexpression of buccal crown inclination, and underexpression of buccal expansion was observed at all tooth levels. Conclusions: : Two-week aligner change regimens offer improved accuracy compared with 1-week aligner changes. SmartTrack® 2-week changes were the most accurate for buccal expansion, whereas EX30® 2-week changes were the most accurate for buccolingual inclination.

Comparison of labio-palatal incisor movement between two wear protocols: a retrospective cohort study.

OBJECTIVES: To investigate the accuracy of the Invisalign appliance in achieving predicted angular tooth movement of the maxillary central incisors, to locate the center of rotation in a labio-palatal direction, and to investigate any difference between 1-weekly and 2-weekly wear protocols. MATERIALS AND METHODS: This study involved a retrospective sample of two groups of 46 Class I adult subjects treated non-extraction with different protocols of 1-weekly and 2-weekly wear. The pretreatment, predicted outcome and achieved outcome digital models were superimposed and measured using metrology software. Angular and center-of-rotation measurements in the sagittal plane for the maxillary right central incisor were analyzed. RESULTS: There was a statistically significant difference between predicted and achieved angular measurements (P < .005) for labial tooth movements regardless of wear protocol. For palatal movements, no statistically significant difference was observed (P > .05). A small amount of overexpression was observed in some cases. Regarding crown and root control, uncontrolled tipping was the most predictable. No statistically significant difference was found between predicted and achieved center of rotation, but the confidence interval was wide. No statistically significant difference (P > .05) was found between the two wear protocols for the parameters measured. CONCLUSIONS: For maxillary central incisors, labial angular movements were not as accurate as palatal movements. Overcorrection could be recommended with careful clinical monitoring due to the possibility of overexpression. Control of root movements may be unpredictable, and further research is required to draw stronger conclusions. For the parameters measured in this clinical sample, there was no difference between the two wear protocols.

Clinical expression of programmed mandibular canine rotation using various attachment protocols and 1- vs 2-week wear protocols with Invisalign SmartTrack aligners: A retrospective cohort study.

INTRODUCTION: Rotation of rounded teeth, particularly canines, is reported as one of the most difficult and inaccurate tooth movements with aligners. This retrospective study aimed to assess the accuracy and reliability of prescribed mandibular canine rotation with Invisalign aligners and the influence of attachment type and wear schedule on accuracy. METHODS: A sample of 75 subjects with mandibular canines requiring rotation was collected from an existing database. The initial, predicted finish, and achieved finish, were measured using metrology software, and the differences between predicted and achieved mandibular canine rotations were calculated. The sample was divided into 3 groups: optimized rotation attachments using 1-week wear, optimized rotation attachments using 2-week wear, and conventional rectangular attachments using 2-week wear. RESULTS: Rotation was an underexpressed movement, with an overall median sample efficiency of 75.4%. For all groups, predicted rotation was not equivalent to achieved rotation at a ± 5° equivalence margin. This indicates that none of the Invisalign SmartTrack aligner attachment configurations display clinical accuracy in their predicted rotation. By attachment type, median efficiencies of 81.5%, 76.5%, and 63.1% were found for groups 1-week wear, 2-week wear, and 2-week wear, respectively. By wear schedule, there was no significant difference in efficiency for optimized rotation attachments. CONCLUSIONS: The clinical expression of canine rotation with SmartTrack aligners is less than the prescribed rotation for all attachment configurations. Vertical rectangular attachments were associated with the least accurate expression of prescribed movement. There was no difference in rotation efficiency between 1- or 2-week aligner wear.

Accuracy and reliability of tooth widths and Bolton ratios measured by ClinCheck Pro.

INTRODUCTION: This study aimed to assess the accuracy and reliability of tooth widths and Bolton ratios measured in ClinCheck Pro. METHODS: Five sets of typodonts were scanned using an iTero scanner, and the digital models were electronically transmitted to Align Technology for treatment planning. The typodont teeth were then segmented and measured using 3-dimensional optical profilometry (3D OP) and a calibrated digital caliper. Tooth widths estimated by ClinCheck Pro were compared with those measurements obtained using 3D OP and digital calipers. To determine the reliability of ClinCheck Pro measured tooth widths and Bolton ratios, the records of 30 consecutive patients treated with the Invisalign appliance without interproximal reduction were obtained. Values at the initial ClinCheck Pro treatment plan were compared with those from additional aligner scans. Accuracy, the agreement between methods, and reliability were investigated using the Bland Altman method. RESULTS: A systematic under measurement was observed in the tooth widths measured by ClinCheck Pro (mean, 0.36 mm) compared with those obtained using 3D OP and digital caliper (individually segmented teeth). Although the overall reliability of ClinCheck Pro measured tooth widths was good (intraclass correlation coefficient, 0.96), the reliability of Bolton ratios was only moderate with wide confidence intervals. CONCLUSIONS: ClinCheck Pro systematically underestimates tooth widths compared with 3D OP and digital caliper (individually segmented teeth). In addition, clinicians need to be cautious while relying solely on ClinCheck's Bolton ratios estimation for the treatment plan. These findings may be due to "shape assumptions" in the interproximal areas and could have clinical implications.

Clinical expression of programmed rotation and uprighting of bilateral winged maxillary central incisors with the Invisalign appliance: A retrospective study.

INTRODUCTION: Winged maxillary central incisors (WMCI), defined as mesiopalatal rotation of the crowns of maxillary central incisors, is a common dental trait that affects smile esthetics. This retrospective study aimed to determine the efficacy of rotation and uprighting tooth movements of bilateral WMCI with Invisalign (Align Technology, Santa Clara, Calif). METHODS: Initial, predicted, and achieved stereolithography files of 30 adult patients, consecutively treated with the Invisalign SmartTrack appliance, were superimposed using Geomagic Control X 64 (3D Systems, Rock Hill, SC). The pairs of incisors were assessed for rotation using the interlabial angle (ILA), and individual incisors were measured for rotation and tip. RESULTS: Programmed rotation and uprighting of WMCI are mostly undercorrected with the Invisalign appliance. The mean shortfall in ILA was 10.5° (standard deviation [SD], 10.66; 95% confidence interval [CI], 5.89-14.19; P <0.001) for a mean predicted change of 35.27°. For individual incisors, a mean shortfall of 5.38° (SD, 5.88; 95% CI, 3.58-6.76; P <0.001) was found for a mean 18.75° predicted change in rotation. A mean predicted change in tip of 7.06° showed a mean shortfall of was 2.16° (SD, 3.86°; 95% CI, 1.03-3.01; P <0.001). A moderate and statistically significant correlation between shortfalls in rotation and tip was observed (r = 0.44). Linear regression analysis was used to formulate an equation as a clinical tool to determine the likely achieved outcome on the basis of the predicted change. CONCLUSIONS: Predicted changes in rotation, ILA, and tip were both under and overexpressed. In particular, tip was dependent on the magnitude of planned change. The random inconsistencies in the clinical expression of rotation and tipping warrant careful monitoring and/or remedial actions such as overcorrections aligners.

Predictability of overbite control with the Invisalign appliance.

INTRODUCTION: Control of overbite is considered essential in achieving ideal orthodontic outcomes. Questions have been raised regarding the accuracy of ClinCheck software (Align Technology, Santa Clara, Calif) in predicting posttreatment outcomes with Invisalign, with the paucity of well-researched literature available on this topic. This research aimed to investigate and determine the accuracy of Invisalign (Align Technology) in correcting a deep overbite by comparing the outcomes predicted by ClinCheck with achieved posttreatment outcomes. METHODS: A retrospective study was conducted using pretreatment and posttreatment intraoral scans and predicted outcome (ClinCheck) stereolithography files of 42 adult patients consecutively treated with Invisalign from January 2014 and completed before July 2018, selected from the files of 1 experienced orthodontist. Patients included in the study were treated without extractions and with a minimum of 14 dual arch Invisalign aligners using a 2-weekly aligner change protocol. The pretreatment, posttreatment, and predicted outcome stereolithography files for each patient were imported into Geomagic Control X (3D Systems, Rock Hill, SC) software to measure overbite. RESULTS: The deeper the patient's initial overbite and the greater the amount of programmed reduction in overbite according to ClinCheck, the greater the discrepancy in overbite expression posttreatment. ClinCheck over-predicted overbite reduction in 95.3% of patients in which, on average, only 39.2% of the prescribed overbite reduction was expressed. CONCLUSIONS: Overbite reduction may result in suboptimal outcomes when using the Invisalign appliance unless remedial measures are employed. The deeper the initial overbite, the more challenging it is to achieve the prescribed posttreatment overbite.

The effect of changing crosshead speed on the shear bond strength of orthodontic bonding adhesive.

OBJECTIVE: To examine the influence of different crosshead speeds on the in vitro shear bond strength and adhesive remnant index scores for the same orthodontic adhesive. MATERIALS AND METHODS: One hundred human molars were randomly allocated to four groups. Brackets (.022 inch Victory series, 3M, Monrovia, CA, USA) were bonded with Ortho Solo primer (Ormco, Glendora, CA, USA) and Enlight (Ormco, Glendora, CA, USA) adhesive paste to their buccal surfaces. The brackets were debonded with a universal testing machine (Instron, Canton, MA, USA) with each group subjected to a different crosshead speed of 0.5 mm/min, 1.0 mm/min, 2.0 mm/min and 5.0 mm/minute. Shear bond strength (SBS) was measured and enamel surfaces were examined to determine the adhesive remnant index (ARI) score. RESULTS: No significant differences were found between the mean SBS or ARI score for any of the groups. CONCLUSIONS: Studies using different crosshead speeds when testing identical adhesives may be used to compare the SBS of other orthodontic adhesives, provided the testing protocols are similar.