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Abstract: Obstructive sleep apnea (OSA) affects more than 900 million people around the world (Benjafield et al., 2019). OSA occurs due to obstruction of the airway at different levels of the airway, including upper and lower pharyngeal constrictions due to narrow upper jaw and underdeveloped/backward positioned lower jaw. Treatment modalities of OSA include active oxygen infusion, oral appliances or surgical expansion of the upper arch and/or surgical advancement of the lower and upper jaws; however, these modalities have many challenges and complications (Benjafield et al., 2019; American Academy of Sleep Medicine, 2015; Schwengel et al., 2014; Yaggi et al., 2005). Previous research has shown that rapid maxillary expansion can improve the nasal airway, thereby improving OSA (Peppard et al., 2000; Cordasco et al., 2012; Mônego Moreira et al., 2017). Orthodontic appliances such as clear aligners can be used for slow maxillary expansion; however, the effect of this type of treatment on both the nasal airway volume and morphology has not been investigated. Therefore, the objective of this study was to investigate the effect of clear aligners on the nasal airway volume and morphology of pediatric patients undergoing maxillary expansion. In addition, a pilot study was conducted to investigate the effect of clear aligners on the volume of the nasal airway in adults. We conducted a retrospective study on 13 pediatric patients (ages 6-13 years old). These patients had treatment of their malocclusion using clear aligners and their treatment involved upper arch expansion as well as initial and after treatment CBCTs (Cone Beam Computed Tomography) as part of their routine orthodontic records. We set up a control group of 8 children (7-12 years) without clear aligner treatment but having two CBCTs. Based on the treatment and control groups, we investigated whether pediatric patients treated with clear aligners had a significant increase in upper arch expansion and nasal airway volume and morphology. Secondly, we conducted a retrospective pilot study to investigate the effect of upper arch expansion using clear aligners in the adult population. We studied 6 adults (31-52 years) who were treated with clear aligners for maxillary expansion. The results showed a significant increase in nasal airway volume as well as intermolar distance in the treatment group of pediatric patients, but not in the control group. No correlation was found between the changes in intermolar distance and nasal airway volume in the treatment group. In the adult population, the results suggest a trend of increased nasal airway volume after maxillary expansion with clear aligners, however, the results were not statistically significant. Further study with an increased sample size may confirm the suggested trends. This work provides a method to investigate changes in nasal airway volume and morphology and demonstrates the potential for slow maxillary expansion with clear aligners to improve nasal airway parameters. This suggests that such treatment may be a possible solution to improve outcomes for OSA patients.

Introduction: Composite attachments are a vital part of clear aligner therapy and crucial to accomplish the intended tooth movements throughout treatment. Due to the necessity and importance of attachments, accurate application is imperative. When attachments are bonded, placing them without excess composite flash going beyond the perimeter is nearly impossible. Recent research has studied certain attachment bonding protocols to investigate which bonding protocol produces the least amount of excess, but no research has been done to demonstrate clinical effects excess composite flash has on clear aligner treatment. Aim: To evaluate the effect attachment flash thickness and surface area has on the force delivered to a maxillary central incisors with a Zendura FLX clear aligner. Methods: The experiment was conducted in a lab setting using 3D printed models of the maxillary arch. Zendura FLX .030 mil clear aligners programmed for 0.25 mm of extrusion will be used on a maxillary central incisor. To evaluate the effect of flash thickness and surface area, a standard rectangular anterior extrusion attachment placed on the midfacial surface of the clinical crown was designed with no flash which served as the control. We tested three different surface areas (7mm2, 14mm2, 21mm2) at three different thicknesses (0.2 mm, 0.35 mm, 0.5 mm), making ten total designs. For each of the ten groups, five aligners were fabricated with margins 0.75 mm apical to the gingival zenith. Extrusive and lingual forces were measured using a force gauge. Means and standard deviations were calculated and presented by group. The one-way analysis of variance (ANOVA) was conducted to compare the means between the groups and Tukey’s method was used to adjust for multiple comparisons. P-values less than 0.05 were considered statistically significant. Results: The intended extrusive force decreases as flash surface area decreases and as flash thickness increases. The main finding to note when examining how the intended extrusive force was affected by flash was looking at the standard deviations for each group. The control group had the smallest standard deviation compared to all the groups with flash. When looking at the mean unintended lingual force, all groups including flash showed higher lingual force than the control group with seven out of the nine groups being statically significant. In general, as the thickness of the flash increases, the lingual force applied to the tooth by a clear aligner (CA) increases. Similarly, as the surface area of the flash increases, the lingual force applied to the tooth by a CA increases. Conclusions: This is the first study in which the effect of attachment flash on force applied by a clear aligner has been studied. In this benchtop study, a few conclusions can be made as to the effect attachment flash has on clear aligner therapy (CAT). CAs exert more lingual force when attachment flash is present compared to attachments without flash. As flash thickness increases and flash surface area increases the CAs exert more lingual force. As flash thickness increases and flash surface area decreases the intended extrusive force applied by CAs decreases. When flash is present, the intended extrusive force is less predictable compared to when no flash is present.

Introduction: Orthodontic and orthopedic expansion is necessary to create space to resolve crowding due to arch deficiency or tooth size discrepancy. The Invisalign First clear aligner appliance as a modality for early interceptive orthodontic treatment has become incorporated into orthodontic practices in very recent years. The present study aims to investigate the magnitude of expansion of the Invisalign First clear aligner appliance compared to a Schwartz removable expander in patients with mixed dentition. Additionally, the study aims to compare the efficacy and predictability of Invisalign First clear aligners in this population. Materials & Methods: In this retrospective study, a sample was collected from a single orthodontist practitioner. The sample consisted of 34 patients, 16 patients treated with Invisalign First clear aligners only (Group1) and 19 patients treated with a Schwartz removable appliance and Invisalign First clear aligners (Group 2). Intraoral scans of four timepoints, initial (T1), post-expansion for Group 2 only (T1Exp), first refinement (T2), and final (T3), and planned Clincheck goal (P) model from Clincheck software were imported to Align Technology’s digital measure program (Quantify©). Arch widths and molar inclinations were measured at each timepoint and the changes between timepoints were calculated. Predictability of arch expansion was calculated as T13 (change between initial and final) divided by the Planned dimension multiplied by one hundred. A two sample t-test was used to assess differences in the changes in arch widths and predictability of expansion between two groups. Results: There were statistically significant differences found in the magnitude of expansion and predictability of arch expansion between two groups. Group 2 showed a greater amount of expansion and predictability. Group 1 showed about 50-60% of the planned expansion at the end of treatment. In regards to magnitude of expansion when comparing the two groups, the efficacy predictability of transverse dimensional changes were significantly greater in the Group 2 compared to Group 1, 83% vs 56% (p = 0.001), respectively. The changes in inclination were similar in both groups, with no statistically significant differences.Conclusions: There is a significantly greater amount of expansion and greater predictability with the Schwartz removable appliance compared to the Invisalign First clear aligner appliance in the mixed dentition. The predictability of Invisalign First was 56% and indicates a significant overcorrection of arch expansion is required at the virtual treatment planning stage in Clincheck in order to obtain the arch expansion that was planned

Introduction: Surgically Facilitated Orthodontic Therapy (SFOT) has been utilized for years to overcome the limitations encountered with traditional orthodontic treatment of dentoalveolar and alveoloskeletal malocclusions. The procedure, which consists of full flap corticotomies and bone grafting, has many proposed benefits including increased speed and range of tooth movement. The purpose of this study is to evaluate arch expansion in patients treated with SFOT and clear aligners. Materials and Methods: A retrospective cohort study design was used to evaluate 51 consecutive adult patients that were treatment planned for significant arch expansion with corticotomies, bone grafting, and clear aligners. 17 of the 51 patients refused the surgical procedure and served as controls. Eight transverse arch width measurements were obtained at three different time points (Initial, ClinCheck, Refinement). Five calculations were performed to determine the magnitude, predictability, and efficiency of arch expansion. Results: The difference in treatment time between the two groups was statistically significant at 5.2 months (P < .0001). On average, corticotomies reduced the length of treatment by 46% and increased the rate of expansion 2.4x. Patients that received SFOT achieved a greater magnitude (+28%) of expansion at a significantly higher rate (P< 0.002) than controls for all eight interarch measurements. The SFOT group displayed higher predictability (% goal achieved) and a smaller difference between predicted and achieved tooth movements for all measures obtained. The mean age for the entire sample was 42.81 (+12.51 years). Conclusion: Arch expansion with corticotomy-assisted clear aligner therapy is significantly more effective, efficient, and predictable than with clear aligners alone. The predictability of expansion with aligners appears to have a higher range than initially thought, even in patients that do not receive corticotomies.

The newly emerging Clarity™ Clear Aligner System from 3M has set out to address one of the biggest pitfalls of thermoplastic aligners: accuracy of orthodontic movements. The 3M Clarity™ Clear Aligner System is unique among clear aligners because it employs a proprietary, sophisticated machine-learning algorithm to design orthodontic movement schematics. The core of the Clarity™ Aligner System is artificial intelligence, meaning that a prospective analysis of preliminary data is essential for the development and improvement of the accuracy of the algorithm. This study investigates movement and accuracy of the Clarity™ Aligner System, from a preliminary data subset from ongoing prospective, randomized clinical trials. Movement from the first trial subset is examined in terms of the following movement factors: secondary premolar-secondary premolar (5+5 in the Palmer system) arch expansion or crowding resolved, absolute rotation, absolute mesial-distal tipping, and absolute torque for both the crown and root. These movements are further examined according to specific tooth types. Both actual observational orthodontic movements and theoretical movements are designed by the Clarity™ System. The accuracy of actual movement in terms of theoretical movements is calculated; however, it is impossible to calculate the significance of these accuracies due to a complete lack of benchmark movement values for the clear aligner market. There are no benchmark values to compare to, so orthodontic movements will be critically examined for performance, and casually compared to alternative aligner systems. Identifying potential weaknesses in the Clarity™ Aligner System is imperative for maximizing its effectiveness.