Forces and moments delivered by the PET-G aligner to a maxillary central incisor for palatal tipping and intrusion

Objective:To evaluate the effect of material thickness and width of the gingival edge on the forces and moments delivered by aligners prepared from Duran foil (PET-G) to a maxillary incisor during tipping and intrusion.Materials and Methods:Aligners prepared from PET-G of three material thicknesses (0.5, 0.625, and 0.75 mm) and three widths of gingival edges (0–1, 3–4, and 6–7 mm) were investigated during incisor palatal tipping and intrusion of 0.5 mm each. Forces and moments were measured with a six-component measuring device. The influence of aligner thickness and aligner extend on the force and moment development were tested for statistical significance (P < .05).Results:The F_x and F_z forces produced during palatal tipping and intrusion by the 0.75-mm aligner material was significantly higher than those produced by the 0.5-mm-thick material (P = .005 and P = .047, respectively). There was no statistical difference between aligner thickness of 0.5 and 0.625 mm and between 0.625 and 0.75 mm. The same behavior was observed for the palatal moment (M_y). The F_x and F_z forces produced during palatal tipping and intrusion by the aligner with an extension of 0–1 mm edge was significantly lower than that of the aligner with a larger extension (3–4 mm edge: P = .003; 6–7 mm: P = .001). However, there was no statistical difference between aligners with a 3–4-mm and a 6-mm edge. The same behavior was observed for the palatal moment (M_y).Conclusions:The forces and moments exerted by the PET-G aligner on teeth vary, depending on the material thickness, width of the aligner edge, and direction of tooth movement.     

Treatment management between orthodontists and general practitioners performing clear aligner therapy

Objective:To investigate differences in case selection, treatment management, and aligner treatment expertise between orthodontists and general practitioners.Materials and Methods:A parallel pair of original surveys with three sections (case selection, treatment management, and demographics) was sent to orthodontists (N = 1000) and general dentists (N = 1000) who were providers of aligner treatment.Results:Orthodontists had treated significantly more patients with aligners, had treated more patients with aligners in the previous 12 months, and had received more aligner training than general dentists (P < .0001). In general, case confidence increased with increasing experience for both orthodontists and general dentists. After adjusting for experience, there was a significant difference in aligner case confidence between orthodontists and general dentists for several malocclusions. General dentists were more confident than orthodontists in treating deep bite, severe crowding, and Class II malocclusions with aligners (P ≤ .0001). Significant differences were also found for all treatment management techniques except interproximal reduction.Conclusion:There was a significant difference in case selection, treatment management, and aligner expertise between orthodontists and general dentists, although the differences in case selection were small. Overall, it was shown that orthodontists and general dentists elected to treat a variety of moderate to severe malocclusions with aligners but with different utilization of recommended auxiliaries, perhaps demonstrating a difference in treatment goals.     

Effects of variable attachment shapes and aligner material on aligner retention

Objective:To evaluate the retention of four types of aligners on a dental arch with various attachments.Materials and Methods:For this study, three casts were manufactured, two of which contained attachments (ellipsoid and beveled), and one without any attachments to serve as a control. Four types of aligners were thermoformed: Clear-Aligner (CA)-soft, CA-medium, and CA-hard, with various thicknesses, and Essix ACE. Measurements of vertical displacement force during aligner removal were performed with the Gabo Qualimeter Eplexor. Means and standard deviations were next compared between different aligner thicknesses and attachment shapes.Results:CA-soft, CA-medium, and CA-hard did not present a significant increase in retention, except when used in the presence of attachments. Additionally, CA-medium and CA-hard required significantly more force for removal. Essix ACE demonstrated a significant decrease in retention when used with ellipsoid attachments. The force value for Essix ACE removal from the cast with beveled attachments was comparable to that of CA-medium. Forces for aligner removal from the model without attachments showed a linear trend. Essix ACE did not show a continuous increase in retention for each model. Overall, ellipsoid attachments did not present a significant change in retention. In contrast, beveled attachments improved retention.Conclusions:Ellipsoid attachments had no significant influence on the force required for aligner removal and hence on aligner retention. Essix ACE showed significantly less retention than CA-hard on the models with attachments. Furthermore, beveled attachments were observed to increase retention significantly, compared with ellipsoid attachments and when using no attachments.     

Effects of mechanical properties of thermoplastic materials on the initial force of thermoplastic appliances

Objective:To measure the forces delivered by thermoplastic appliances made from three materials and investigate effects of mechanical properties, material thickness, and amount of activation on orthodontic forces.Materials and Methods:Three thermoplastic materials, Duran (Scheu Dental), Erkodur (Erkodent Erich Kopp GmbH), and Hardcast (Scheu Dental), with two different thicknesses were selected. Values of elastic modulus and hardness were obtained from nanoindentation measurements at 28°C. A custom-fabricated system with a force sensor was employed to obtain measurements of in vitro force delivered by the thermoplastic appliances for 0.5-mm and 1.0-mm activation for bodily tooth movement. Experimental results were subjected to several statistical analyses.Results:Hardcast had significantly lower elastic modulus and hardness than Duran and Erkodur, whose properties were not significantly different. Appliances fabricated from thicker material (0.75 mm or 0.8 mm) always produced significantly greater force than those fabricated from thinner material (0.4 mm or 0.5 mm). Appliances with 1.0-mm activation produced significantly lower force than those with 0.5-mm activation, except for 0.4-mm thick Hardcast appliances. A strong correlation was found between mechanical properties of the thermoplastic materials and force produced by the appliances.Conclusions:Orthodontic forces delivered by thermoplastic appliances depend on the material, thickness, and amount of activation. Mechanical properties of the polymers obtained by nanoindentation testing are predictive of force delivery by these appliances.     

Effect of clear aligner wear protocol on the efficacy of tooth movement:: A randomized clinical trial

ObjectivesTo compare the efficacy of orthodontic tooth movement with three aligner wear protocols: 7 day, 10 day, and 14 day.Materials and MethodsEighty patients were randomly allocated into three groups: group A (7-day changes), group B (10-day changes), and group C (14-day changes). The posttreatment scans were compared with the final virtual treatment simulations through digital superimposition. The differences between predicted and actual achieved treatment outcomes were computed in six angular and six linear dimensions. Differences >0.5 mm for linear measurements and >2° for angular measurements were considered clinically relevant.ResultsWithin groups, and irrespective of wear protocol, all linear discrepancies in both jaws were deemed clinically insignificant (<0.5 mm) while nearly all angular discrepancies were considered clinically significant (>2.0°). When the three groups were compared, group C (14-day changes) showed significantly greater accuracy in the posterior segment for maxillary intrusion, distal-crown tip and buccal-crown torque, and mandibular intrusion and extrusion. The mean treatment duration in the 7-day aligner change group was nearly half that of the 14-day aligner change group (5 months vs 9 months).ConclusionsFourteen-day changes were statistically significantly more accurate in some posterior movements. However, this difference in accuracy did not exceed the threshold for clinical significance (>0.5 mm/>2.0°). Achieving a clinically similar accuracy between the 7-day protocol and 14-day protocol in half the treatment time suggests a 7-day protocol as an acceptable treatment protocol. Clinicians may consider slowing down to a 14-day protocol if challenging posterior movements are desired.     

Effect of clear aligner therapy on the buccolingual inclination of mandibular canines and the intercanine distance

Objective:To compare the changes in buccolinugal inclination of mandibular canines and intercanine distance in patients treated with clear aligners to those treated with preadjusted edgewise appliances.Materials and Methods:The buccolingual inclination of mandibular canines and the intercanine distance were measured on pre- and posttreatment cone-beam computed tomograms of 30 patients who had been treated with clear aligners and 30 patients who had been treated with fixed preadjusted edgewise appliances. Differences between the aligner and fixed appliance groups and between pre- and posttreatment measurements were tested for statistical significance.Results:In both groups, most of the mandibular canines had positive buccolingual inclinations (ie, their crowns were positioned lateral to their roots) both before and after treatment. While there was no difference between the groups pretreatment, the posttreatment buccolingual inclination was significantly greater in the aligner group. In the fixed appliance group, the canines became more upright with treatment, while the buccolingual inclination did not change significantly in the clear aligner group. The intercanine distance did not differ between the groups either before or after treatment. However, it increased significantly over the course of treatment in the aligner group, whereas it did not change significantly in the fixed appliance group.Conclusions:Orthodontic treatment with clear aligners tends to increase the mandibular intercanine distance with little change in inclination in contrast to treatment with fixed appliances, which leaves the intercanine distance unchanged but leads to more upright mandibular canines.     

双膜透明矫治器移动兔下颌中切牙的效果评价

目的:应用双膜透明矫治器对兔下颌中切牙进行正畸移动,评价双膜透明矫治器移动牙的效果。方法:选用6只新西兰大白兔,实验组为双膜透明矫治器加力组（3只）,设计戴用3步矫治器,每一步牙移动0.33 mm,先戴用薄膜透明矫治器2 d,再戴用厚膜透明矫治器2 d;对照组为常规厚度膜片透明矫治器加力组（3只）,设计戴用3步矫治器,每一步牙移动0.20 mm,每步矫治器戴4 d。在每组兔分别戴用第1、2和3步矫治器后制取模型,测量牙移动数据。采用SPSS 19.0软件包对数据进行统计学分析。结果:2组牙移动表达的精确度从牙冠切端向龈端逐渐降低,实验组的精确度随矫治时间增加呈下降趋势,而对照组的精确度随矫治时间增加无明显变化。实验组牙冠切端、中端和龈端牙移动速率均显著大于对照组（P<0.001）。结论:兔下颌中切牙在透明矫治器的作用下产生倾斜移动。采用双膜透明矫治器矫治,牙移动速率加快,但牙移动表达的精确度降低。     

Forces and moments generated by aligner‐type appliances for orthodontic tooth movement: A systematic review and meta‐analysis

The aim of this review was to systematically appraise the evidence on aligner mechanics and forces and moments generated across difference types of aligners. In vitro‐ laboratory studies for model simulated tooth movement with aligners. Database searches within Medline via Pubmed, Cochrane Central Register of Controlled Trials (CENTRAL), LILACS via BIREME Virtual Health Library. Unpublished literature was also searched in Open Grey, ClinicalTrials.gov ( www.clinicaltrials.gov ), the National Research Register ( www.controlled-trials.com ) and Center for Open Science (Open Science Framework), using the terms “aligner” AND “orthodontic”. Risk of bias assessment was based on the Cochrane Risk of Bias tool. Random effects meta‐analyses were conducted. A total of 447 studies were identified through electronic search and after careful consideration of pre‐ defined eligibility criteria, 13 deemed eligible for inclusion, while 2 were included in the quantitative synthesis. When palatal tipping of the upper central incisor through PET‐G aligners was considered, aligner thickness of 0.5, 0.625 or 0.75 mm was not associated with a significantly different moment to force (M/F) ratio, given a common gingival edge width of 3‐4 mm. Aligner thickness does not appear to possess a significant role in forces and moments generated by clear aligners under specific settings, while the most commonly examined tooth movements are tipping and rotation. The findings of this review may be applicable to certain conditions in laboratory settings.     

Stress relaxation properties of four orthodontic aligner materials: A 24-hour in vitro study

Objective:To investigate the stress release properties of four thermoplastic materials used to make orthodontic aligners when subjected to 24 consecutive hours of deflection.Materials and Methods:Four types of aligner materials (two single and two double layered) were selected. After initial yield strength testing to characterize the materials, each sample was subjected to a constant load for 24 hours in a moist, temperature-regulated environment, and the stress release over time was measured. The test was performed three times on each type of material.Results:All polymers analyzed released a significant amount of stress during the 24-hour period. Stress release was greater during the first 8 hours, reaching a plateau that generally remained constant. The single-layer materials, F22 Aligner polyurethane (Sweden & Martina, Due Carrare, Padova, Italy) and Duran polyethylene terephthalate glycol-modified (SCHEU, Iserlohn, Germany), exhibited the greatest values for both absolute stress and stress decay speed. The double-layer materials, Erkoloc-Pro (Erkodent, Pfalzgrafenweiler, Germany) and Durasoft (SCHEU), exhibited very constant stress release, but at absolute values up to four times lower than the single-layer samples tested.Conclusions:Orthodontic aligner performance is strongly influenced by the material of their construction. Stress release, which may exceed 50% of the initial stress value in the early hours of wear, may cause significant changes in the behavior of the polymers at 24 hours from the application of orthodontic loads, which may influence programmed tooth movement.     

舌向整体移位设计量对隐形矫治力影响的研究

目的 利用传感器芯片对不同移位设计量的隐形矫治器所产生的矫治力进行测量,探讨移位设计量对隐形矫治力及其衰减的影响,为临床正畸矫治设计提供参考.方法 选用厚度1.0mm的热压膜材料（Erkodent,德国）压制右上中切牙舌向移位设计量分别为0.2、0.3、0.4、0.5和0.6mm的隐形矫治器,利用隐形矫治微型测力系统测量矫治器产生的矫治力并观察其在2周内的衰减情况.结果 移位设计量为0.2、0.3、0.4、0.5、0.6mm的矫治器所产生的矫治力的平均值分别为8.047、9.250、10.189、11.821、12.247N.在矫治器戴入的最初8h矫治力衰减迅速,之后衰减缓慢直至第4天起矫治力维持在较为平稳的水平.结论 随矫治器移位设计量的增加,隐形矫治器产生的矫治力也相应增加.推荐上中切牙舌向整体移动的移位量设计不应超过0.5mm.患者在佩戴每副矫治器的最初4天应尽量全天佩戴.     

Cephalometric comparison of adult anterior open bite treatment using clear aligners and fixed appliances

Objectives:To compare fixed appliances and clear aligner therapy in correcting anterior open bite and in controlling the vertical dimension in adult patients with hyperdivergent skeletal patterns.Materials and Methods:In this retrospective study, two treatment groups of adult (≥18 years old) hyperdivergent patients (mandibular plane angles of ≥38°) with anterior open bites were included: 17 fixed appliance patients and 36 clear aligner patients. Thirteen cephalometric measurements representing the vertical dimension were reported for each group. A two-sample t-test was used to assess differences in changes in mandibular plane angle and overbite between the two treatment groups.Results:There were no statistical differences found in the magnitude of overbite correction and the changes in any of the cephalometric measurements for vertical control. The clear aligner group showed a slightly greater amount of lower incisor extrusion (P = .009). The main mechanism of open bite correction was similar between the two treatment groups and was accomplished through retroclination of the upper and lower incisors while maintaining the vertical position of the upper and lower molars.Conclusions:Cephalometric comparison of anterior open bite correction and changes in the mandibular plane angle associated with use of clear aligners and fixed appliances did not demonstrate statistically significant differences in adult hyperdivergent patients.     

A randomized clinical trial comparing mandibular incisor proclination produced by fixed labial appliances and clear aligners

Objective:To compare the mandibular incisor proclination produced by fixed labial appliances and third generation clear aligners.Materials and Methods:Patients underwent a course of orthodontic treatment using either fixed labial appliances or clear aligners (Invisalign). Mandibular incisor proclination was measured by comparing pretreatment and near-end treatment lateral cephalograms. Eligibility criteria included adult patients with mild mandibular incisor crowding (<4 mm) and Class I skeletal bases (ANB, 1–4°). The main outcome was the cephalometric change in mandibular incisor inclination to the mandibular plane at the end of treatment. Eligible patients picking a sealed opaque envelope, which indicated their group allocation, was used to achieve randomization. Data was analyzed using a Welch two-sample t-test.Results:Forty-four patients (mean age, 26.4 ± 7.7 years) were randomized in a 1:1 ratio to either the fixed labial appliance or the clear aligner group. Baseline characteristics were similar for both groups: Fixed appliance mean crowding was 2.1 ± 1.3 mm vs clear aligner mean crowding, 2.5 ± 1.3 mm; pretreatment mean mandibular incisor inclination for the fixed appliance group was 90.8 ± 5.4° vs 91.6 ± 6.4° for the clear aligner group. Fixed appliances produced 5.3 ± 4.3° of mandibular incisor proclination. Clear aligners proclined the mandibular incisors by 3.4 ± 3.2°. The difference between the two groups was not statistically significant (P > .05).Conclusion:There was no difference in the amount of mandibular incisor proclination produced by clear aligners and fixed labial appliances in mild crowding cases.     

Clear aligner orthodontic therapy of rotated mandibular round-shaped teeth: A finite element study

Objective:To evaluate, using the finite element method, the orthodontic rotational movement of a lower second premolar obtained with clear aligners, analyzing different staging and attachment configurations.Materials and Methods:A CAD model including a complete lower dental arch (with element 4.5 mesially rotated 30°) and the corresponding periodontal ligaments, attachments, and aligner was designed and imported to finite element software. Starting from the CAD model, six projects were created to simulate the following therapeutic combinations for correcting element 4.5 position: (1) without attachments, (2) single attachment placed on the buccal surface of element 4.5, (3) three attachments placed on the buccal surfaces of teeth 4.4 to 4.6. For each project, both 1.2° and 3° of aligner activation were considered.Results:All the analyzed configurations revealed a clockwise rotation movement of element 4.5 on the horizontal plane. Models with attachments showed a greater tooth displacement pattern than models without attachments. Simulations with attachments and 3° of aligner activation exhibited the best performance concerning tooth movement but registered high stresses in the periodontal ligaments, far from the ideal stress levels able to produce tooth rotational movement.Conclusions:The model with a single attachment and 1.2° of aligner activation was the most efficient, followed by the three attachment model with the same degree of activation. Aligner activation should not exceed 1.2° to achieve better control of movement and reasonable stress in periodontal structures.     

Outcome assessment of orthodontic clear aligner vs fixed appliance treatment in a teenage population with mild malocclusions

ObjectiveTo assess the efficacy and efficiency of treatment in adolescents presenting with mild malocclusions, comparing outcomes using clear aligners to fixed appliances.Materials and MethodsPatients identified retrospectively and consecutively from one private practice had been treated with either clear aligners (Invisalign, Align Technology, Santa Clara, Calif) or fixed appliances (0.022 Damon, Ormco, Orange, Calif; n = 26/group). Assessments of occlusion were made using the American Board of Orthodontics Discrepancy Index (DI) for initial records and Cast-Radiograph Evaluation (CRE) for final records. Number of appointments, number of emergency visits, and overall treatment time were determined from chart reviews. Data were analyzed using Pearson''s correlation, Wilcoxon rank tests, unpaired t-tests, and Chi-square tests, with significance set to P ≤ .05.ResultsPretreatment, the aligner and fixed groups showed no significant difference in overall severity (DI: 11.9 ± 5.3 vs 11.6 ± 4.8) or in any individual DI category. Posttreatment scores showed finishes for the aligner group had fewer discrepancies from ideal relative to the fixed appliance group (CRE: 30.1 ± 8.3 vs 37.0 ± 9.3; P < .01). Patients treated with aligners had fewer appointments (13.7 ± 4.4 vs 19.3 ± 3.6; P < .0001), fewer emergency visits (0.8 ± 1.0 vs 3.6 ± 2.5; P < .0001), and shorter overall treatment time (16.9 ± 5.7 vs 23.4 ± 4.4 months; P < .0001).ConclusionsOutcomes for treatment of mild malocclusions in adolescents showed equivalent effectiveness of clear aligners compared to fixed appliances, with significantly improved results for clear aligner treatment in terms of tooth alignment, occlusal relations, and overjet. Assessment of the number of appointments, number of emergency visits, and overall treatment time showed better outcomes for treatment with clear aligners.     

不同双膜透明矫治器戴用时间对正畸牙移动效果影响的实验研究

目的 探讨不同双膜透明矫治器戴用时间对正畸牙移动效果的影响。方法 选取9只新西兰大白兔,随机分为实验1组、实验2组和对照组,每组3只。对两个实验组动物采用薄膜（0.625 mm）和厚膜（0.750 mm）两种厚度膜片透明矫治器进行矫治,均设计为每一步矫治使左右下中切牙各远中移动0.33 mm,总矫治时长为12 d;其中实验1组（缩短薄膜矫治器戴用时间）的每步矫治时长为3 d（薄膜矫治器1 d、厚膜矫治器2 d）,共进行4步矫治;实验2组的每步矫治时长为4 d（薄膜矫治器2 d、厚膜矫治器2 d）,共进行3步矫治。对照组配戴厚膜矫治器,但不进行牙移动。测量矫治前及每步矫治结束后实验动物临床冠切点、中点、龈点的牙移动相关指标。对实验组每一步矫治前后及两个实验组之间的牙移动量、牙移动速率及牙移动表达精确度进行比较分析。结果 （1）戴用双膜透明矫治器可有效完成牙移动,与矫治前比较,牙移动量具有统计学意义（P < 0.05）;（2）同一位点实验1组牙移动速率均高于实验2组（P < 0.05）;（3）实验1组缩短薄膜佩戴时间,与实验2组的单步矫治牙移动量差异无统计学意义（P > 0.05）;（4）在进行同一步骤矫治时,实验1组龈点牙移动表达精确度稍低于实验2组,在切点和中点两组的牙移动表达精确度无差异;（5）实验1组和实验2组的牙移动方式均为倾斜移动,且两组的倾斜程度差异无统计学意义（P > 0.05）。结论 （1）缩短薄膜戴用时间可有效提高牙移动速率,且牙移动量无明显差异,但龈点牙移动量表达精确度可能稍有降低;（2）临床可适当缩短薄膜戴用时间,以提高正畸牙移动速率,并可缩短疗程、优化患者感受,尤其适用于需要倾斜移动的病例。     

Comparison of alveolar bone thickness and height after slow expansion using quad-helix or clear aligners

ObjectiveThe study was conducted to investigate the thickness and height of the alveolar bone of individual teeth after slow maxillary expansion (SME) with quad helix or clear aligner appliances and hypothesized that there is no difference in buccal alveolar bone thickness or heights in patients treated by either quad helix or clear aligners.Material and MethodsThis is a retrospective study; the records of 22 patients treated between December 2019 to April 2020 by dental arch expansion using either clear aligners or quad helix appliances were retrieved and studied. The results obtained through cone beam computed tomography (CBCTs) before and immediately after maxillary expansion (2 + 1 mm per side) were analyzed (11 in the Quad Helix group and 11 in the clear aligner). The data collected was analyzed using linear and angular measurements obtained through On-demand 3D App software. Furthermore, Statistical Package for Social Sciences (SPSS) version 25.0 was used to present the findings by mean and standard deviations, and Scheffe’s test was applied for comparing forces.ResultsThe results showed that the mean age of patients in the clear aligner group and Quad Helix was 16.27 ± 0.56 years and 15.5 ± 1.53 years, respectively. There was no difference in buccal alveolar bone thickness or heights in patients treated by either quad helix or clear aligners. This is due to the findings that suggest that there was a decrease in bone height and bone width when treated with a quad helix as compared to clear alignment.ConclusionIt can be concluded that the quad helix SME treatment affects alveolar bone integrity; therefore, clear aligners might be better for treating patients than the quad helix.     

Initial force systems during bodily tooth movement with plastic aligners and composite attachments: A three-dimensional finite element analysis

Objective:To describe, using a three-dimensional finite element (FE) model, the initial force system generated during bodily movement of upper canines with plastic aligners with and without composite attachments.Materials and Methods:A CAD model of an upper right canine, its alveolar bone and periodontal ligament, thermoformed plastic aligner, and two light-cured composite attachments were constructed. A FE model was used to analyze the effects of imposing a distal movement condition of 0.15 mm on the aligner (simulating the mechanics used to produce a distal bodily movement) with and without composite attachments.Results:In terms of tension and compression stress distribution, without composite attachments a compression area in the cervical third of the distal root surface and a tension area in the apical third of the mesial surface were observed. With composite attachments, uniform compression areas in the distal root surface and uniform tension area in the mesial root surface were observed. Compression areas in the active surfaces of the composite attachments were also observed. In terms of movement patterns, an uncontrolled distal inclination, with rotation axis between the middle and cervical root thirds, was observed without composite attachment. Distal bodily movement (translation) was observed with composite attachment.Conclusions:In a three-dimensional FE analysis of a plastic aligner system biomechanically supplementary composite attachments generate the force system required to produce bodily tooth movement; the absence of biomechanically supplementary composite attachments favors the undesired inclination of the tooth during the translation movements.     

Differences in finished case quality between Invisalign and traditional fixed appliances:: A randomized controlled trial

ObjectivesTo compare the treatment and posttreatment effects of Invisalign aligners that incorporated SmartForce features and attachments to traditional fixed appliances.Materials and MethodsThis randomized controlled trial included 66 patients, 32 aligners, and 34 fixed-appliance patients. The median ages of the aligner and braces patients were 26.7 (interquartile range [IQR]: 9.8) and 25.9 (IQR: 16.6) years, respectively. Pretreatment occlusion was assessed using the ABO Discrepancy Index. Posttreatment (T1) and 6-month retention (T2) occlusions were quantified using the ABO Objective Grading System (OGS) scores.ResultsThe braces group finished treatment significantly (P < .001) earlier (0.4 years) than the aligner group. The median DI scores for the aligner and braces groups were 4.5 and 7.0, respectively, which was a statistically significant (P = .015), but clinically insignificant, difference. There were no statistically significant between-group differences for the total OGS scores or any of the individual component scores at debond (T1) or after 6 months of retention (T2). During the posttreatment period, alignment and overjet worsened significantly in the aligner group, while buccolingual inclinations and occlusal relations improved. Over the same period, alignment worsened in the braces group and buccolingual inclinations improved. There was no statistically significant between-group difference in posttreatment changes of the total OGS scores.ConclusionsWhile patients with simple malocclusions require 4.8 months longer treatment times with aligners than traditional braces, the treatment and 6-month posttreatment occlusal outcomes are similar.     

Scanning electron microscopy evaluation of aligner fit on teeth

Objectives:The fitting of aligners on anchorage teeth is a crucial factor in clear aligner orthodontics. The purpose of this experimental study was to evaluate the fitting of two aligner systems, Invisalign and CA-Clear Aligner, using scanning electron microscopy (SEM).Materials and Methods:Passive aligners (Invisalign and CA-Clear Aligner) were adapted on resin casts obtained by stereolithography (STL) files of a patient, and then sectioned buccolingually. Upper and lower central incisors, upper and lower first premolars, and upper and lower first molars were the regions analyzed. Representative microphotographs of sections were taken with a scanning electron microscope (SEM); a total of 160 micrometric measurements were obtained and analyzed with ANOVA tests.Results:Invisalign provided an overall better fit on lower incisors (F = 11.48, P = .0095) and on lower molars (F = 19.93, P = .0012). Considering the different regions, Invisalign provided better fit at the gingival edge of the buccal aspect on lower incisors (F = 11.33, P = 0.0056) and at the gingival edge of the lingual aspect on upper premolars (F =5.34, P = 0.0047). On the upper molars, Invisalign provided better fit at the gingival edge of the buccal aspect, while CA-Clear Aligner provided better fit at the buccal maximum convexity, on the buccal cusp, on the occlusal groove and at the palatal cusp. On lower molars, Invisalign showed a more accurate fit at the buccal aspect points.Conclusions:Invisalign and CA-Clear Aligner exhibited comparable fit on anchorage teeth. Invisalign provided better fit at the gingival edges of aligners, while the CA-Clear Aligner provided better fit on complex occlusal surfaces.