Invisalign® treatment in the anterior region

Comparison of achieved and predicted crown movement in adults after 4 first premolar extraction treatment with Invisalign

INTRODUCTION

In this study, we compared achieved and predicted crown movements of maxillary and mandibular first molars, canines, and central incisors in adults after 4 first premolar extraction treatment with Invisalign.

METHODS

Seventeen adult patients who received 4 first premolar extraction treatment with Invisalign and completed the first series of aligners were included. Superimposition of pretreatment and actual posttreatment dental models was acquired using registrations of pretreatment and posttreatment craniofacial models on the basis of bone surfaces and registrations of craniofacial and dental models on the basis of dental crown surfaces, respectively. Superimposition of pretreatment and predicted posttreatment models was acquired from ClinCheck software. Achieved and predicted 3-dimensional crown movements of maxillary and mandibular first molars, canines, and central incisors were then compared using the paired t test.

RESULTS

Relative to predicted changes, first molars achieved greater mesial displacement, mesial tipping, and buccal inclination in both the maxilla and mandible, greater intrusion in the maxilla, and greater mesial-lingual rotation and less constriction in the mandible. Canines achieved greater distal tipping in both the maxilla and mandible, less retraction in the maxilla, and greater lingual inclination and extrusion in the mandible. Central incisors achieved greater distal tipping and lingual inclination and extrusion in both the maxilla and mandible and less retraction in the maxilla.

CONCLUSIONS

Tooth crown movements were not fully achieved as predicted following Invisalign treatment. Differences focused on mesial tipping, buccal inclination, mesial displacement, and intrusion of the first molars, as well as distal tipping, lingual inclination, insufficient retraction, and intrusion of the canines and central incisors.

Efficacy of Invisalign attachments: A retrospective study

INTRODUCTION

The purpose of this study was to compare the efficacy of Invisalign's (Align Technology, Santa Clara, Calif) optimized and conventional attachments on rotational and extrusive tooth movements.

METHODS

Initial, predicted, and achieved digital dental models from 100 orthodontic patients were exported from Invisalign's ClinCheck software as stereolithography files and subsequently imported into the Slicer CMF program (version 4.7.0; http://www.slicer.org) for superimpositions on posterior teeth with no planned movement. Rotational and extrusive measurements for both optimized and conventional attachments were made on 382 teeth from the superimposition of the initial and predicted models (predicted movement) and from the superimposed initial and achieved models (achieved movement). Predicted and achieved movements were compared along with movements of teeth with optimized and conventional attachments.

RESULTS

Differences between accuracies of tooth movements using optimized vs conventional attachments for both rotation and extrusion were neither statistically nor clinically significant. Mean predicted values were larger than mean achieved values for all attachment types and movements (P < 0.0001). For extrusion, the mean difference between predicted and achieved movements was clinically significant (0.40 mm and 0.62 mm for optimized and conventional attachments, respectively). Overall, the mean accuracy was 57.2%. Mean accuracy was 63.2% for rotation and 47.6% for extrusion. Interproximal reduction or spacing did not significantly affect accuracy.

CONCLUSIONS

Conventional attachment types may be just as effective as Invisalign's proprietary optimized attachments for rotations of canines and premolars and extrusion of incisors and canines. Clinicians should consider overcorrecting tooth movements, especially anterior tooth extrusion.

How efficient is customized lingual orthodontics? An assessment of treatment outcome

OBJECTIVE

To assess the efficacy of lingual orthodontics by comparing setups and post-treatment casts.

SETTING AND SAMPLE POPULATION

Thirty-two consecutive patients treated with a customized lingual orthodontic appliance were included in this retrospective study.

MATERIALS AND METHODS

Initial casts, post-treatment casts and setups were scanned, and the digital models produced were analysed in terms of overjet; overbite; molar and canine relationships; intercanine, interpremolar and intermolar distances; upper and lower arch lengths; midline deviation; bucco-lingual angulation of all teeth and mesio-distal angulation of anterior teeth. Comparisons between setups and post-treatment casts were performed via paired t tests. Relationships between the planned and actual correction were studied using regression analysis.

RESULTS

Statistically significant differences in bucco-lingual torque between setups and post-treatment casts were found for all upper teeth, except for central incisors. In the lower jaw, statistically significant differences in bucco-lingual torque were found between setups and post-treatment casts for the lower incisors and molars. No statistically significant differences in mesio-distal angulation of anterior teeth were found between setups and post-treatment casts. Upper and lower arch widths did not vary significantly between setups and final casts, except upper inter-second premolar and intermolar distances.

CONCLUSION

Customized lingual appliances offer efficient control of mesio-distal angulation of all anterior teeth. Significant differences in torque between setups and post-treatment casts were observed for upper lateral incisors, canines, premolars and molars, as well as lower incisors and molars. However, the torque difference was clinically significant (over three degrees) for upper second premolars and molars only.

Clear aligner orthodontic treatment: Angle Society of Europe consensus viewpoint

Orthodontics has witnessed not only an exponential rise in demand from adult patients but accompanying this, the emergence of alternate aesthetic treatment options to the more traditional fixed labial appliance. The concept of using clear aligners as a means of achieving tooth movement has increased in popularity among both patients and clinicians alike. However, the question over best research evidence as to their clinical effectiveness to treat a range of malocclusion traits remains elusive and controversial among the profession.In an attempt to offer the profession some clear guidance, The Angle Society of Europe reviewed and discussed the current published evidence (2005-2018) on their clinical use, during the annual meeting in January 2020, to help formulate a consensus viewpoint on the clinical applications.

Predicted and actual outcome of anterior intrusion with Invisalign assessed with cone-beam computed tomography

INTRODUCTION

The purpose of this study was to compare predicted anterior teeth intrusion measurements with the actual clinical intrusion measurements using cone-beam computed tomography. Understanding the precision of the software in anticipating changes may help practitioners predict the need for overcorrection.

METHODS

Twenty-two patients, with a mean age of 23.74 years, who underwent Invisalign (Align Technology, Santa Clara, Calif) clear aligners treatment for both arches only after having completed treatment with an initial series of aligners were included in this study. The pretreatment and posttreatment cone-beam computed tomography scans after the initial series were acquired by a single orthodontist practitioner. ClinCheck measurements were recorded with Align Technology. The long axis of the anterior tooth intrusion movement was measured in 142 teeth. A comparison between the predicted and actual measurements of anterior intrusion of the teeth was performed, and the intraclass correlation coefficients showed an almost perfect agreement in the linear measurements.

RESULTS

A statistically notable difference between the predicted and actual measurements of anterior intrusion. The predicted intrusion movement of the maxillary canines (P = 0.001), maxillary lateral incisors (P <0.0001), and maxillary central incisors (P <0.0001) significantly differed from the actual values. Similarly, the intrusion movement in the mandibular teeth seemed to be inaccurate, with significant differences in the mandibular canines (P <0.0001) and mandibular lateral and central incisors (P <0.0001).

CONCLUSIONS

The mean precision of true anterior intrusion with Invisalign clear aligners was 51.19%, and the mean amount of correction was 48.81%. The use of other supplementary methods of anterior teeth intrusion may be helpful to reduce the rate of midcourse corrections and refinements.

Quantitative assessment of interproximal tooth reduction performed as part of Invisalign® treatment in 10 orthodontic practices

Background

Interproximal reduction (IPR) is a treatment option for orthodontic space gain. The attainment of prescribed objectives in aligner treatment may require IPR that is accurately performed both qualitatively and quantitatively.

Objective

This study assesses the in vivo accuracy of IPR carried out in 10 orthodontic practices as a method of orthodontic space creation.

Methods

A comparison of proposed and achieved amounts of IPR completed (accuracy), the accuracy of IPR within and between upper and lower dental arches, and the accuracy of IPR within and between posterior and anterior arch segments were performed using 3-dimensional digital study models gained via Align’s® ClinCheck.

Results

The findings indicated that IPR was routinely underperformed by all practices studied. On average, the amount of IPR achieved represented only 44.0% of the total prescribed per tooth in the sample assessed, with a mean discrepancy of 0.16 mm per tooth. There were statistically significant differences only between the overall anterior and posterior groups (p < 0.01) and between maxillary anterior and maxillary posterior groups (p < 0.01); however, these were not clinically significant. Significant differences in IPR performance were noted between different orthodontic practices.

Conclusions

This study demonstrates that the clinical performance of IPR in 10 orthodontic practices consistently fails to achieve the prescribed amount often by large variations. The effect of this under-performance on clinical outcomes remains to be quantified.

Has Invisalign improved? A prospective follow-up study on the efficacy of tooth movement with Invisalign

INTRODUCTION

The purpose of this research was to provide an update on the accuracy of tooth movement with Invisalign (Align Technology, Santa Clara, Calif).

METHODS

This prospective clinical study included 38 patients treated with Invisalign Full or Invisalign Teen. All teeth, from the central incisor to the second molar, were measured on digital models created from intraoral scans. Predicted values were determined by superimposing the initial and final ClinCheck models, and achieved values were determined by superimposing the initial ClinCheck models and the digital models from the posttreatment scans. Individual teeth were superimposed with a best-fit analysis and measured using Compare software (version 8.1; GeoDigm, Falcon Heights, Minn). The types of tooth movements studied were a mesial-distal crown tip, buccal-lingual crown tip, extrusion, intrusion, and mesial-distal rotation.

RESULTS

The mean accuracy of Invisalign for all tooth movements was 50%. The highest overall accuracy was achieved with a buccal-lingual crown tip (56%), whereas the lowest overall accuracy occurred with rotation (46%). The accuracies for mesial rotation of the mandibular first molar (28%), distal rotation of the maxillary canine (37%), and intrusion of the mandibular incisors (35%) were particularly low.

CONCLUSIONS

There was a marked improvement in the overall accuracy; however, the strengths and weaknesses of tooth movement with Invisalign remained relatively the same.

OrthoAligner "NAM": A Case Series of Presurgical Infant Orthopedics (PSIO) Using Clear Aligners

Presurgical infant orthopedics (PSIO) is done to reduce the size of the cleft defect along with improving the arch alignment and nasolabial aesthetics in patients with cleft lip and palate, leading to an improvement of nasolabial aesthetics allowing for a tidier and more aesthetic reparative procedure and postsurgical scar. Since the 2000s, clear aligners have slowly and steadily treaded their way as an acceptable orthodontic modality, with their usage and acceptability increasing considerably over the past decade. Thus, from the knowledge gathered in its 10 years working with 3-dimensional (3-D) diagnosis, treatment planning, and 3-D Printing services, Compass 3D (Belo Horizonte, Brazil) developed the OrthoAligner NAM system. This case series highlights one of the world's first documented cases of PSIO treated with a series of clear aligners.

Biomechanical Effects of Different Auxiliary-Aligner Designs for the Extrusion of an Upper Central Incisor: A Finite Element Analysis

Aim

To evaluate the biomechanical effects of four different auxiliary-aligner combinations for the extrusion of a maxillary central incisor and to define the most effective design through finite element analysis (FEA).

Materials and Methods

A full maxillary arch (14 teeth) was modelled by combining two different imaging techniques: cone beam computed tomography and surface-structured light scan. The appliance and auxiliary element geometries were created by exploiting computer-aided design (CAD) procedures. The reconstructed digital models were imported within the finite element solver (Ansys® 17). For the extrusion movement, the authors compared the aligner without an attachment with three auxiliary-aligner designs: a rectangular palatal attachment, a rectangular buccal attachment, and an ellipsoid buccal attachment. The resulting force-moment (MF) system delivered by the aligner to the target tooth and the tooth displacement were calculated for each scenario.

Results

The maximum tooth displacement along the z-axis (0.07 mm) was obtained with the rectangular palatal attachment, while the minimum (0.02 mm) was obtained without any attachments. With the ellipsoid attachment, the highest undesired moments M_x and M_y were found. The rectangular palatal attachment showed the highest F_z (2.0 N) with the lowest undesired forces (F_x = 0.4 N; F_y = −0.2 N).

Conclusions

FEA demonstrated that the rectangular palatal attachment can improve the effectiveness of the appliance for the extrusion of an upper central incisor.

A systematic review of the accuracy and efficiency of dental movements with Invisalign®

We are currently living in an era where the use of computer-aided design/computer-aided manufacturing has allowed individualized orthodontic treatments, but has also incorporated enhanced digitalized technology that does not permit improvisation. The purpose of this systematic review was to analyze publications that assessed the accuracy and efficiency of the Invisalign® system. A systematic review was performed using a search strategy to identify articles that referenced Invisalign®, which were published between August 2007 and August 2017, and listed in the following databases: MEDLINE, Embase, Cochrane Library, Web of Knowledge, Google Scholar, and LILACS. Additionally, a manual search of clinical trials was performed in scientific journals and other databases. To rate the methodological quality of the articles, a grading system described by the Swedish Council on Technology Assessment in Health Care was used, in combination with the Cochrane tool for risk of bias assessment. We selected 20 articles that met the inclusion criteria and excluded 5 due to excess biases. The level of evidence was high. Although it is possible to treat malocclusions with plastic systems, the results are not as accurate as those achieved by treatment with fixed appliances.

Effects of Attachment of Plastic Aligner in Closing of Diastema of Maxillary Dentition by Finite Element Method

The aim of this study was to clarify the effect of attachment on tooth movement produced by a plastic aligner. Closing of a diastema, in which the maxillary right and left central incisors moved bodily, was simulated using a finite element method. Long-term orthodontic movements of the maxillary dentition were simulated by accumulating the initial displacement of teeth produced by elastic deformation of the periodontal ligament. The incisor tipped and rotated just after placement of the aligner irrespective of the attachment. After a sufficiently long time, the incisor was upright and moved bodily in the aligner with attachment, but the incisor remained tipped in the aligner without attachment. It was demonstrated that the attachment was effective for achieving bodily movement.

Clinical effectiveness of Invisalign® orthodontic treatment: a systematic review

BACKGROUND

Aim was to systematically search the literature and assess the available evidence regarding the clinical effectiveness of the Invisalign® system.

METHODS

Electronic database searches of published and unpublished literature were performed. The reference lists of all eligible articles were examined for additional studies. Reporting of this review was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Three RCTs, 8 prospective, and 11 retrospective studies were included. In general, the level of evidence was moderate and the risk of bias ranged from low to high, given the low risk of bias in included RCTs and the moderate (n = 13) or high (n = 6) risk of the other studies. The lack of standardized protocols and the high amount of clinical and methodological heterogeneity across the studies precluded a valid interpretation of the actual results through pooled estimates. However, there was substantial consistency among studies that the Invisalign® system is a viable alternative to conventional orthodontic therapy in the correction of mild to moderate malocclusions in non-growing patients that do not require extraction. Moreover, Invisalign® aligners can predictably level, tip, and derotate teeth (except for cuspids and premolars). On the other hand, limited efficacy was identified in arch expansion through bodily tooth movement, extraction space closure, corrections of occlusal contacts, and larger antero-posterior and vertical discrepancies.

CONCLUSIONS

Although this review included a considerable number of studies, no clear clinical recommendations can be made, based on solid scientific evidence, apart from non-extraction treatment of mild to moderate malocclusions in non-growing patients. Results should be interpreted with caution due to the high heterogeneity.

Accuracy of clear aligners: A retrospective study of patients who needed refinement

INTRODUCTION

The purpose of this study was to determine the accuracy of specific tooth movements with Invisalign (Align Technology, Santa Clara, Calif).

METHODS

The study sample included 20 Class I adult patients treated with Invisalign; they completed their first series of aligners and had to have a "refinement" series. Initial and predicted models were obtained from the initial ClinCheck (Align Technology). The starting point of the refinement ClinCheck was used to create the achieved models. Predicted and achieved models were superimposed over the initial ones on posterior teeth using the 3-dimensional Image Analysis open-source software Slicer CMF. Three hundred ninety-eight teeth were measured for vertical, horizontal, and rotational movements, and transverse widths were measured. The amount of predicted tooth movement was compared with the achieved amount for each movement.

RESULTS

Horizontal movements of all incisors seemed to be accurate, with small (0.20-0.25 mm) or insignificant differences between predicted and achieved amounts. Vertical movements and particularly intrusions of maxillary central incisors were found to be less accurate, with a median difference of 1.5 mm (P <0.001). All achieved rotations were significantly smaller than those predicted, with the maxillary canines exhibiting the greatest difference of 3.05° (P <0.001).

CONCLUSIONS

The most inaccurate movements identified in this study were intrusion of the incisors and rotation of the canines.

Relationships between facial divergence and DMD parameters

INTRODUCTION

The aim of this study was to examine the relationship between facial divergence and the parameters of dentomaxillary discrepancy (DMD), in particular crowding, the curve of Spee and the position of the incisors in the sagittal dimension.

MATERIAL AND METHODS

A total of 90 young adult patients was selected from among the Moroccan orthodontic population attending the dentofacial orthopedic department and satisfying the following inclusion criteria: complete permanent dentition and a skeletal class I pattern with no previous orthodontic treatment, no crossbite, no periodontal disease, no mandibular asymmetry and no condylodiscal disunion. On cephalometric tracings, measurements were made of angles FMA, Go-Gn/SN, Occ/SN in the vertical direction, and of the values I/NA et i/NB in the sagittal direction. The curve of Spee and dental crowding were assessed using the one-way ANOVA test and the Bonferroni post-hoc test. Correlation analysis was performed between divergence and the different variables measured, using SPSS software with a 0.05 significance threshold.

RESULTS

Patients recruited for the study had a mean age of 19.8±0.5 and were distributed as follows: 28 normodivergent, 31 hypodivergent and 31 hyperdivergent, 42 females and 48 males. Comparison showed that hypodivergent subjects had less crowding than hypo- or normodivergent individuals (P<0.05). Hypodivergent subjects had a more pronounced curve of Spee than the other two groups. This difference was not significant (P>0.05). Hyperdivergent subjects presented more labioversion and vestibular positioning of the incisors compared with the hypodivergent (P<0.05) and normodivergent (P<0.05) groups. Correlation analysis showed that crowding and the incisor positions in millimeters and in degrees were positively correlated to a moderate extent with facial divergence (r=0.3, r=0.5, r=0.4; P<0.05), while the curve of Spee was not (P>0.05). No correlation was found between age or sex and the DMD parameters (P>0.05).

How accurate is Invisalign in nonextraction cases? Are predicted tooth positions achieved?

OBJECTIVE

To evaluate the accuracy of Invisalign technology in achieving predicted tooth positions with respect to tooth type and direction of tooth movement.

MATERIALS AND METHODS

The posttreatment models of 30 patients who had nonextraction Invisalign treatment were digitally superimposed on their corresponding virtual treatment plan models using best-fit surface-based registration. The differences between actual treatment outcome and predicted outcome were computed and tested for statistical significance for each tooth type in mesial-distal, facial-lingual, and occlusal-gingival directions, as well as for tip, torque, and rotation. Differences larger than 0.5 mm for linear measurements and 2° for angular measurements were considered clinically relevant.

RESULTS

Statistically significant differences (P < .05) between predicted and achieved tooth positions were found for all teeth except maxillary lateral incisors, canines, and first premolars. In general, anterior teeth were positioned more occlusally than predicted, rotation of rounded teeth was incomplete, and movement of posterior teeth in all dimensions was not fully achieved. However, except for excess posttreatment facial crown torque of maxillary second molars, these differences were not large enough to be clinically relevant.

CONCLUSIONS

Although Invisalign is generally able to achieve predicted tooth positions with high accuracy in nonextraction cases, some of the actual outcomes may differ from the predicted outcomes. Knowledge of dimensions in which the final tooth position is less consistent with the predicted position enables clinicians to build necessary compensations into the virtual treatment plan.

Advanced Aligner Orthodontics

Invisalign initially had limitations which have now been overcome. Advances in the quality of aligner materials, attachments and the introduction of a new force system, have expanded the range of treatment possibilities from severe crowding to more difficult extraction cases, open bite cases, and lower molar distalization cases.

Orthodontic aligners and root resorption: A systematic review

INTRODUCTION

Root resorption is one of the leading problems in orthodontic treatment. Most earlier studies have assessed the incidence and severity of root resorption following orthodontic treatment using fixed appliances as well as associated factors. However, few studies have assessed these parameters in the context of orthodontic treatment using thermoplastic splints or aligners. The aim of this systematic review was to assess the incidence and severity of root resorption following orthodontic treatment using aligners and associated factors. A comparative analysis was also made with fixed multi-bracket treatments.

MATERIALS AND METHODS

The data bases consulted were: Medline, Embase, EBSCO Host, Cochrane Library and Science Direct. Our search included meta-analyses, randomized and non-randomized controled trials, cohort studies and descriptive studies published before December 2015 and evidencing a connection with the incidence and severity of root resorption following orthodontic treatment using aligners alone or compared with fixed multi-bracket treatments.

RESULTS

Among the 93 selected references, only 3 studies met our selection criteria. The incidence of root resorption ranged between 0 and 46%, of which 6% were severe cases. Relative to fixed multi-bracket non-extraction treatments to correct the same malocclusions, the incidence of resorption ranged between 2% and 50%, of which 22% were severe cases. In both techniques, the incidence of resorption was higher for the maxillary incisors and was not influenced by either age or sex.

CONCLUSION

In malocclusion cases not requiring extractions, orthodontic aligner treatment is possibly associated with a lower incidence of resorption than fixed multi-bracket treatment. Further research encompassing extraction cases is needed to better assess the incidence and severity of root resorption following the use of these removable appliances.

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.

Patient survey on Invisalign® treatment comparing [corrected] the SmartTrack® material to the previously used [corrected] aligner material

OBJECTIVES

In 2013, a novel material SmartTrack^® was introduced to replace the previous material used for Invisalign^® aligners. We conducted this study to test how this transition was accepted by patients during ongoing Invisalign^® treatment.

METHODS

We surveyed a total of 72 patients (68 % women, 32 % men, mean age: 29.3 ± 9.2 years) who had worn the new material for a mean of 6 months. They completed a questionnaire with 25 items that compared both materials in terms of pain, pressure upon insertion, comfort, mucosal irritation, phonetics, discoloration, and taste.

RESULTS

On a numerical rating scale (NRS) ranging from 0 to 10, the new aligner material was rated by the respondents to cause significantly (p < 0.001) less maximum pain than the old material (2.8 vs. 3.8). Significant reductions were obtained for duration of pain (p < 0.001) and duration of pressure (2.5 vs. 1.9 days; p = 0.001) upon insertion of the aligners. Over 90 % of the respondents indicated less or equal pain during eating, felt that the new material offered a tighter fit, and provided more favorable ratings for impairment, durability, and discoloration. Improved comfort was reported by 50 % of the respondents.

CONCLUSIONS

The new material was favorably rated by the patients and showed significant reductions in pain intensity, pain duration, and pressure upon insertion. Important clinical parameters like overall comfort and impairment also were improved. The clinical effectiveness of the new material remains to be investigated.

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.

How effective is the Invisalign® system in expansion movement with Ex30' aligners?

OBJECTIVES

The aims of this study are to validate a new method for quantifying the predictability of expansion movement with the Invisalign® system and to determine whether there are statistically significant differences between planned expansion with ClinCheck® and actual clinical quantification using upper post-treatment model comparisons.

MATERIALS AND METHODS

A sample of 116 patients subjected to expansion with Invisalign® was studied. The following variables were measured at T1 and T2 on 3D models and ClinCheck®: canine gingival width, first premolar gingival width, second premolar gingival width, first molar gingival width, canine cuspid width, first premolar cuspid width, second premolar cuspid width, first molar cuspid width, canine depth, arch depth, first molar rotation, first right and left molar rotation, and first molar inclination.

RESULTS

Measurement error was tested, showing good precision for all variables. The paired test showed non-significant differences between the 3D model and ClinCheck® at T1 for all variables except first molar cuspid width and arch depth. Statistically significant differences were found for canine gingival width, first premolar gingival width, second premolar gingival width, first molar gingival width, canine cuspid width, first premolar cuspid width, second premolar cuspid width, first molar cuspid width, and canine depth when the 3D model and ClinCheck® were compared at T2.

CONCLUSIONS

Differences between the 3D model and ClinCheck® at T2 showed that planned expansion at the end of treatment is not predictable.

CLINICAL RELEVANCE

This is the first in vivo human study to quantify the predictability of expansion in patients with Invisalign® Ex30 material.

The predictability of transverse changes with Invisalign

OBJECTIVES

To investigate the predictability of arch expansion using Invisalign.

MATERIALS AND METHODS

Sixty-four adult white patients were selected to be part of this retrospective study. Pre- and posttreatment digital models created from an iTero scan were obtained from a single orthodontist practitioner. Digital models from Clincheck were also obtained from Align Technology. Linear values of upper and lower arch widths were measured for canines, premolars, and first molars at two different points: lingual gingival margins and cusp tips. A paired t-test was used to compare expansion planned on Clincheck with the posttreatment measurements. Variance ratio tests were used to determine if a larger change planned was associated with larger error.

RESULTS

For every maxillary measurement, there was a statistically significant difference between Clincheck and final outcome (P < .05), with prediction worsening toward the posterior region of the arch. For the lower arch measurements at the gingival margin, there was a statistically significant difference between the Clincheck planned expansion and the final outcome (P < .05). Points measured at the cusp tips of the lower arch teeth showed nonstatistically significant differences between Clincheck prediction and the final outcome (P > .05). Variance ratios for upper and lower arches were significant (P < .05).

CONCLUSIONS

The mean accuracy of expansion planned with Invisalign for the maxilla was 72.8%. The lower arch presented an overall accuracy of 87.7%. Clincheck overestimates expansion by body movement; more tipping is observed. Overcorrection of expansion in the posterior region of the maxillary arch seems appropriate.

Clear Aligners Generations and Orthodontic Tooth Movement

Clear aligner technology has evolved over the last 15 years, with these appliances continually being modified to increase the range of tooth movements that they can achieve. However, there is very little clinical research available to show how these appliances achieve their results. This article describes the different generations of clear aligners that are available and highlights their use. However, until more clinical research becomes available, aligners cannot be routinely prescribed as an effective alternative to fixed labial appliances.

Precision of implementing virtual setups for orthodontic treatment using CAD/CAM-fabricated custom archwires

OBJECTIVES

The SureSmile® process (OraMetrix®; Richardson, TX, USA) utilizes computer-aided design and computer-aided manufacturing (CAD/CAM). A virtual setup is created for treatment planning and chairside implementation using custom archwires fabricated by robots. The objective of this study was to determine the precision of this implementation.

METHODS

The setup models of 26 consecutive patients were compared to models of the final outcome. Using a virtual matching process, the planned and the achieved tooth positions were superimposed and the differences between them calculated along three translational planes and three rotational axes, thus, yielding six deviation values for each tooth.

RESULTS

The median deviations were 0.19-0.21 mm based on translational movements and 1.77°-3.04° based on rotational movements. The precision of implementing the setups decreased from anterior to posterior, with incisors showing the best outcomes.

CONCLUSION

Virtual setups can be implemented in a clinically successful fashion with custom archwires fabricated by CAD/CAM in accordance with the SureSmile® process.

Clear aligners generations and orthodontic tooth movement

Clear aligner technology has evolved over the last 15 years, with these appliances continually being modified to increase the range of tooth movements that they can achieve. However, there is very little clinical research available to show how these appliances achieve their results. This article describes the different generations of clear aligners that are available and highlights their use. However, until more clinical research becomes available, aligners cannot be routinely prescribed as an effective alternative to fixed labial appliances.

Changes in mandibular incisor position and arch form resulting from Invisalign correction of the crowded dentition treated nonextraction

OBJECTIVE

To investigate changes in mandibular incisor position resulting from Invisalign correction of the crowded dentition without extraction.

MATERIALS AND METHODS

A retrospective chart review was completed on 61 adult White patients. Patients were categorized into three groups based on the value of pretreatment crowding of the lower dentition: 20 mild (2.0-3.9 mm), 22 moderate (4.0-5.9 mm), and 19 severe (>6.0 mm). Cephalometric radiographs were measured to determine lower incisor changes. Interproximal reduction and changes in arch width were also measured. Statistical evaluation of T0 and T1 values using paired t-tests and analysis of covariance were applied to evaluate mean value changes.

RESULTS

Lower incisor position and angulation changes were statistically significant in the severe crowding group. There were no statistically significant differences in lower incisor position between the mild and moderate crowding groups. There was a statistically significant increase in buccal expansion in each of the three groups.

CONCLUSIONS

Invisalign(®) treatment can successfully resolve mandibular arch crowding using a combination of buccal arch expansion, interproximal reduction, and lower incisor proclination. When there is <6 mm of crowding, lower incisor position remained relatively stable. The lower incisors proclined and protruded in the more severely crowded dentitions (>6 mm).

Integrated three-dimensional digital assessment of accuracy of anterior tooth movement using clear aligners

Objective

To assess the accuracy of anterior tooth movement using clear aligners in integrated three-dimensional digital models.

Methods

Cone-beam computed tomography was performed before and after treatment with clear aligners in 32 patients. Plaster casts were laser-scanned for virtual setup and aligner fabrication. Differences in predicted and achieved root and crown positions of anterior teeth were compared on superimposed maxillofacial digital images and virtual models and analyzed by Student's t-test.

Results

The mean discrepancies in maxillary and mandibular crown positions were 0.376 ± 0.041 mm and 0.398 ± 0.037 mm, respectively. Maxillary and mandibular root positions differed by 2.062 ± 0.128 mm and 1.941 ± 0.154 mm, respectively.

Conclusions

Crowns but not roots of anterior teeth can be moved to designated positions using clear aligners, because these appliances cause tooth movement by tilting motion.

Predicted and actual end-of-treatment occlusion produced with aligner therapy

OBJECTIVE

To compare three-dimensional (3D) ClinCheck™ models with the subjects' actual 3D posttreatment models using the American Board of Orthodontics Objective Grading System (OGS).

MATERIALS AND METHODS

This prospective, within-subject study included 27 consecutive cases treated with aligner therapy. The posttreatment plaster models taken immediately after treatment were scanned and converted to stereolithography (STL) files; the ClinCheck models were also converted to STL format. MeshLab software was used to measure the seven components of the OGS, including alignment, marginal ridges, buccolingual inclinations, occlusal contacts, occlusal relationships, overjet and interproximal contacts. An overall OGS deduction score was also calculated.

RESULTS

Compared with the posttreatment models, the ClinCheck models showed significantly (P  =  .016) fewer overall OGS point deductions (24 vs 15). These overall differences were due to significantly (P < .05) more deductions among the posttreatment models than the ClinCheck models for alignment (4.0 vs 1.0 deductions), buccolingual inclinations (4.0 vs 3.0 deductions), occlusal contacts (3.0 vs 2.0 deductions), and occlusal relations (4.0 vs 2.0 deductions).

CONCLUSION

The ClinCheck models do not accurately reflect the patients' final occlusion, as measured by the OGS, at the end of active treatment.

INFLUENCE OF FRICTION IN TRANSPARENT TOOTH CORRECTION TREATMENT: FINITE ELEMENT METHOD

Objective: The objective was to evaluate the effect of frictional forces on the canine's translation and rotation in transparent tooth correction treatment. Materials and Methods: Based on computed tomography (CT) images of the teeth and their supporting tissues, solid models were used to build finite-element models. One canine was simulated translation and rotation in the buccolingual direction by aligners with different friction coefficients. Results: The change of the canine's rotation centers and periodontal ligament (PDL) stress with an increase of the friction coefficient in the two movement types were obtained. Conclusions: Friction coefficient has little effect on the canine's translation movement. While in rotation cases, the small friction coefficient seems to be helpful to gain the body movement type.

Periodontal health during clear aligners treatment: a systematic review

BACKGROUND

Clear aligner treatment (CAT) has been cited as a safe and comfortable orthodontic procedure for adult patients. However, the available evidence is scarce.

OBJECTIVE

To perform a systematic review of the existing literature in order to assess periodontal health during CAT.

SEARCH METHODS AND SELECTION CRITERIA

Pubmed, Pubmed Central, National Library of Medicine's Medline, Embase, Cochrane Central Register of Controlled Clinical trials, Web of Knowledge, Scopus, Google Scholar, and LILACS were searched from January 1945 to September 2014 to identify all peer-reviewed papers potentially relevant to the review.

DATA COLLECTION AND ANALYSIS

After duplicate selection and extraction procedures, the risk of bias was assessed according to the Centre for Reviews and Dissemination criteria, and a 3-point grading system, as described by the Swedish Council on Technology Assessment in Health Care (SBU), was used to rate the methodological quality of the selected papers. A PICOS table was used for data extraction.

RESULTS

Five relevant articles were selected from the 1247 identified articles. The level of evidence was moderate for all the studies. A significant improvement of the periodontal health indexes was revealed, in particular when CAT was compared to fixed appliances. No periodontal CAT adverse effects were observed in the selected studies.

CONCLUSIONS

Periodontal health indexes were significantly improved during CAT. The results of this review should be interpreted with some caution because of the number, quality, and heterogeneity of the included studies.

Efficacy of clear aligners in controlling orthodontic tooth movement: a systematic review

OBJECTIVE

To assess the scientific evidence related to the efficacy of clear aligner treatment (CAT) in controlling orthodontic tooth movement.

MATERIALS AND METHODS

PubMed, PMC, NLM, Embase, Cochrane Central Register of Controlled Clinical Trials, Web of Knowledge, Scopus, Google Scholar, and LILACs were searched from January 2000 to June 2014 to identify all peer-reviewed articles potentially relevant to the review. Methodological shortcomings were highlighted and the quality of the studies was ranked using the Cochrane Tool for Risk of Bias Assessment.

RESULTS

Eleven relevant articles were selected (two Randomized Clinical Trials (RCT), five prospective non-randomized, four retrospective non-randomized), and the risk of bias was moderate for six studies and unclear for the others. The amount of mean intrusion reported was 0.72 mm. Extrusion was the most difficult movement to control (30% of accuracy), followed by rotation. Upper molar distalization revealed the highest predictability (88%) when a bodily movement of at least 1.5 mm was prescribed. A decrease of the Little's Index (mandibular arch: 5 mm; maxillary arch: 4 mm) was observed in aligning arches.

CONCLUSIONS

CAT aligns and levels the arches; it is effective in controlling anterior intrusion but not anterior extrusion; it is effective in controlling posterior buccolingual inclination but not anterior buccolingual inclination; it is effective in controlling upper molar bodily movements of about 1.5 mm; and it is not effective in controlling rotation of rounded teeth in particular. However, the results of this review should be interpreted with caution because of the number, quality, and heterogeneity of the studies.

Control of lower incisor inclination with a completely customized lingual appliance for dentoalveolar compensation of class III malocclusion

OBJECTIVE

Bracket slots and orthodontic archwires offering high dimensional precision are needed for fully customized lingual appliances. We aimed to investigate whether high-precision appliances of this type enable dentoalveolar compensation of class III malocclusion so that lower incisor inclination at the end of treatment will closely match the anticipated situation as defined in a pretreatment setup.

MATERIALS AND METHODS

This retrospective study included a total of 34 consecutive patients who had worn a fully customized lingual appliance to achieve dentoalveolar compensation for class III malocclusion by intermaxillary elastics, or proximal enamel reduction, or extraction of teeth in one or both jaws. Casts fabricated at different points in time were three-dimensionally scanned to analyze how precisely the lower incisor inclinations envisioned in the setup were implemented in clinical practice.

RESULTS

Aside from minor deviations of ±3.75°, the lower incisor inclinations were clinically implemented as planned even in patients with major sagittal discrepancies.

CONCLUSION

Treatment goals predefined in a setup of dentoalveolar compensation for class III malocclusion can be very precisely achieved via a customized lingual appliance. Correct planning can prevent undesirable lingual tipping of the lower incisors. This finding should not encourage a more liberal use of dentoalveolar compensation, but it should heighten clinicians' awareness of how essential it is to sufficiently consider the individual anatomy of the dentoalveolar complex during treatment planning.

Apical root resorption during orthodontic treatment with aligners? A retrospective radiometric study

Introduction

Objective of this study was to investigate the incidence and severity of apical root resorptions (ARR) during orthodontic treatment with aligners.

Materials and methods

The sample comprised 100 patients (17–75 years of age) with a class I occlusion and anterior crowding before treatment, treated exclusively with aligners (Invisalign®, Align Technologies, Santa Clara, CA, USA). The following teeth were assessed: upper and lower anterior teeth and first molars. Root and crown lengths of a total of 1600 teeth were measured twice in pre- and post-treatment panoramic radiographs. Afterwards, relative changes of the root length during treatment were calculated by a root-crown-ratio taking pre- and post-treatment root and crown lengths into consideration. A reduction of this ratio was considered as a shortening of the initial root length. Additionally, tooth movements of the front teeth were assessed by lateral cephalograms and the 3-dimensonal set up of each patient.

Results

All patients had a reduction of the pre-treatment root length with a minimum of two teeth. On average 7.36 teeth per patient were affected. 54% of 1600 measured teeth showed no measurable root reduction. A reduction of >0%-10% of the pre-treatment root length was found in 27.75%, a distinct reduction of >10%-20% in 11.94%. 6.31% of all teeth were affected with a considerable reduction of >20%. We found no statistically significant correlation between relative root length changes and the individual tooth, gender, age or sagittal and vertical orthodontic tooth movement; except for extrusion of upper front teeth, which was considered as not clinical relevant due to the small amount of mean 4% ARR.

Conclusions

The present study is the first analyzing ARR in patients with a fully implemented orthodontic treatment with aligners (i.e. resolving anterior crowding). The variety was high and no clinical relevant influence factor could be detected. A minimum of two teeth with a root length reduction was found in every patient. On average, 7.36 teeth per patient were affected.