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Creative adjuncts for clear aligners, part 2: Intrusion, rotation, and extrusion
... Patients desire "braceless" correction of their smiles 10 and thus far, the efforts to give them what they want has led to continual advances and increasing number of applications and adjuncts for aligners in orthodontics. [11][12][13][14][15][16][17][18][19][20][21][22][23] Compliance, consequences, and quality of life with clear aligners If treatment with aligners was to be seen as completely successful, it was not enough to occasionally straighten some teeth just in the esthetic zone. Predictable, consistent, and completed results without adverse effects were requirements. ...
... Simply expecting teeth to move from start to a finished occlusion without a specific plan in-between for how these teeth will overcome obstacles (i.e., collisions, contact points, occlusal and muscular forces, insufficient force, or contacts from the plastic) is unrealistic at best. 9 One of the earliest adjuncts to help seat aligner trays, attempt to maintain "tracking," and increase occlusal forces to elicit tooth movement was the introduction of aligner "chewies" (Chewies Aligner Tray Seaters, Dentsply Raintree Essix, York, PA). 15,19 These plastic "cotton rolls" are prescribed for patients to use at least the first few days after changing to each new pair of aligners. Like the concept of a tooth positioner, the patient places the device in a site where teeth are not tracking (i. ...
... The patient then bites and holds onto the chewies repeatedly, over a few minutes of time daily, with their aligners in place. 15,19 The intent is to help seat the aligner on the teeth that are not tracking, slightly intrude the teeth adjacent to a tooth in question, and the added perturbations may help to accelerate the remodeling in that site to stimulate the tooth to move as prescribed. ...
... 15 6. Intrusion 15,16 Correction of deep overbite using clear aligners is a difficult task. With the use of mini-implants, it is possible to achieve intrusion of single as well as en-mass intrusion in deep bite and open bite cases (Figure 5 a, b). ...
... By engaging the elastic chain from the mini-implant into the buccal button and between the lingual buttons, couple force is applied which aids in its derotation (Figure 7 a,b). [15][16][17] ...
The control of anchorage is essential in orthodontic treatment of adult patients. Complex tooth movements in lingual appliances and aligners require anchorage planning. Mini-screws enable the orthodontists to have good control over tooth movement in all three dimensions, while preserving the patient’s aesthetics. This article describes various clinical cases performed through aligners and lingual appliances by using mini-implants.
... Bowman et al., in their study, highlight the challenges in correcting dental rotations with clear aligners, especially for severe cases [28]. They note the increased risk of relapse and the need for intricate control, which aligners might not always provide. ...
The implementation of Clear Aligner Therapy (CAT) in adult orthodontics exemplifies the integration of advanced technology in the dental healthcare sector. Representing a significant shift in modern orthodontics, CAT offers a convenient and aesthetic alternative to traditional fixed appliance treatments for mal-aligned dentition. This narrative review aims to explore the applicability of CAT, delineating its biomechanics, indications, contraindications, scope, limitations, and factors influencing long-term stability and successful outcomes. A comprehensive literature search was conducted using databases like Google Scholar, PubMed, Cereus, and the Cochrane Library. Articles were selected based on their relevance to clear aligners, without brand specificity, and covered a wide range of cases to establish CAT’s scope and limitations. This review includes individual case studies, systemic reviews, comparative analyses, case reports, finite element analyses, and prospective and retrospective analyses, all contributing to a nuanced understanding of CAT’s applicability and long-term treatment stability. The conclusion underscores CAT’s growing acceptance in orthodontics, including its application in challenging cases, and highlights key determinants that bolster its long-term efficacy.
... Nevertheless, clinicians may therefore seek to prescribe overcorrection or use anterior bite ramps or intermaxillary elastics to overcome the apparent limitation of posterior extrusion with CAT. 22 Alternatively, there was some indication that posterior intrusion may be a more dependable technique for achieving leveling with CAT. ...
Objectives:
To evaluate the predictability of the Invisalign appliance (Align Technology, Santa Clara, Calif) in leveling the maxillary curve of Spee (COS).
Materials and methods:
A retrospective sample of adult subjects treated with the Invisalign appliance between 2013 and 2019 were selected. Patients were treated nonextraction in the maxillary arch and had either Angle Class I or II malocclusions with a minimum of 14 aligners with no bite ramps. Initial, predicted, and actual outcomes were analyzed with Geomagic Control X software (version 2017.0.3; 3D Systems, Cary, NC).
Results:
A sample of 53 cases satisfied inclusion/exclusion criteria. Paired t-tests demonstrated a significant difference between mean predicted and actual maxillary COS leveling with a shortfall of 0.11 mm (SD = 0.37; P = .033). Planned intrusion tended to be more accurate posteriorly with an overexpression of 117% for the first molars. Planned extrusion was the least accurate, with the mid-arch demonstrating expressions of -14% to -48%. These teeth intruded despite a prescribed extrusive movement.
Conclusions:
The Invisalign appliance did not accurately predict maxillary COS leveling. Planned intrusive movements were overcorrected, and planned extrusive movements were either undercorrected or resulted in intrusion. This effect was most apparent for the upper first molar, which expressed 117% and -48% of planned intrusion and extrusion, respectively.
... Clinicians can also take advantage of auxiliaries, such as miniscrews and bondable buttons, during clear aligner treatment. The use of miniscrew anchorage to extrude impacted upper canines or for intrusion 11 (Fig. 10) is a common example. Buttons with segmental elastic chains can be effective in correcting severely rotated teeth, such as premolars (Fig. 11). 2 In virtual treatment planning for such cases, it is important to compensate for undesirable side effects created by the segmental elastic chain on the anchorage teeth. ...
... Rotation, a challenging movement with Invisalign, 31,32 was also the first type of OTM examined. Creating a space with IPR for the rotated tooth may play a critical role. ...
... Using Chewies to exert intrusive forces on targeted posterior teeth can improve the predictability of this method. An article by Bowman et al [28] shows open bite cases successfully treated using these mechanisms. This concept of employing a combination of anterior extrusion and posterior intrusion to correct anterior open bites was also mentioned in Wheeler's article [29] . ...
Objective:The aim was to systematically search the literature and assess the available evidence regarding theclinical effectiveness of clear aligners in correcting anterior open bite. Materials and Methods:PubMed, PubMed Central, MEDLINE, Embase, National Library of Medicine, Cochrane Library, Web of Knowledge, and LILACS were searched electronically to identify all peer-reviewed articles till date potentially relevant to the review.The reference lists of all eligible articles were examined for additional studies. Additional manual search was also conducted in many orthodontic journals of interest, and unpublished articles were also searched for. To rate the methodological quality of the selected articles, a grading system described by the Swedish Council on Technology Assessment in Health Care was used. Results:Ten relevant articles were selected to be included in this systematic review. According to the SBU tool, among the selected studies, the methodological quality was moderate for four studies and limited for the others. Thus, conclusions with a limited level of evidence could be arrived at from the review process. The most recurrent sources of bias were related to the study design, lack of blinding procedure, the sample size, and the lack of control group. However, there was substantial consistency among studies that clear aligner therapy is a viable option to correct anterior open-bite. Conclusion:No definite conclusion could be derived due to the heterogeneity of the studies. Due to the limitations of this study, further clinical and experimental research is needed to statistically assess long-term stability of occlusion and skeletal relationships in treated open-bite cases.
... Early treatment indications for CAT include mild to moderate crowding or diastema, non-skeletal narrow arches, and mild relapse after fixed appliance therapy. 1 With advances in materials and the use of creative adjuncts, the range of treatable malocclusions has expanded to include anterior-posterior, vertical, and transverse corrections. [2][3][4][5][6] At present, increasing numbers of dentists are using the clear aligner in extraction cases, and some of them have reported satisfactory results in the literature. [7][8][9][10][11] However, vertical control remains a problem in extraction cases treated by CAT. ...
Objective:
To investigate the three-dimensional forces created by clear aligners on mandibular teeth during differential activation with en-masse retraction and/or intrusion in vitro.
Methods:
Six sets of clear aligners were designed for differential en-masse retraction and/or intrusion procedures in a first premolar extraction model. Group A0 was a control group with no activation. Groups A1-5 underwent different degrees of retractions and/or intrusions. Each group consisted of 10 aligners. Aligner forces were measured on a multi-axis force/ torque transducer measurement system in real-time.
Results:
In the en-masse retraction groups (A1 and A2), lingual and extrusive forces were observed on the incisors; the canines mainly received distal forces; intrusive forces were seen on the second premolars; and the molars received mesial forces. In the enmasse retraction and intrusion groups (A3, A4, and A5), incisors also received lingual and extrusive forces; canines received distal and intrusive forces; mesial and extrusive forces were seen on the second premolars; and the second molars received distal and intrusive forces. The vertical forces on the incisors did not differ significantly among groups A1, A3, and A5. However, the vertical forces on the second premolars reversed from intrusion in group A1 to extrusion in groups A3 and A5.
Conclusions:
With clear aligners, the "bowing effect" is seen during en-masse anterior teeth retraction and can be partially relieved by performing en-masse retraction accompanied by anterior teeth intrusion. Vertical control of incisors remained unsolved during en-masse retraction, even when intrusive activation was added to the anterior teeth.
... Much higher stresses on the PDLs and gingival surfaces of the attachments were detected on lateral incisors (Figs. 5 and 6). These results were in agreement with previous findings that upper lateral incisors commonly come off track during space closure, and horizontal bevelled attachments are recommended for better retention 33 . Higher stresses were also observed on the gingival surfaces of the attachments on the 1 st and 2 nd molars when more intrusion was placed on incisors (Fig. 6). ...
To evaluate tooth behaviours under various maxillary incisor retraction protocols for clear aligner therapy. A three-dimensional finite element model of maxillary dentition was constructed for first premolar extraction. A loading method was developed to mimic the mode of action of clear aligners for incisor en masse retraction. Three protocols with different amounts of retraction and intrusion on incisors were designed. Initial tooth displacements and stresses on periodontal ligaments were analysed with ANSYS software. The central (U1) and lateral (U2) incisors exhibited uncontrolled lingual tipping and extrusion upon 0.25 mm retraction. U1 exhibited translation movement, while U2 underwent less tipping during 0.2 mm retraction and 0.15 mm intrusion. Labial tipping and intrusion of U1 and bodily intrusion of U2 were observed during 0.1 mm of retraction and 0.23 mm of intrusion. With the additional intrusion on incisors, canine showed extrusion movement, and higher stresses on periodontal ligaments were shifted from U2 to canines. Incisors also exhibited different mesial-distal angulation in the three simulations, while posterior teeth all suffered mesial inclination. Incorporating intrusion displacement in clear aligners led to a tendency of lingual root movement during incisor retraction. The complexity of tooth movement should be recognized regarding clear aligner therapy.
... Anterior open bite can be closed successfully by extrusion of anterior teeth and/or intrusion of the buccal segment using aligners 9,10 . Deep overbite can also be reduced by incisor intrusion using skeletal anchorage and aligners 11 . Crossbite correction and extraction space closure are more challenging, but with the assistance of attachments and/or temporary anchorage devices, promising results have been achieved 12,13 . ...
Objectives: Assessment of sagittal jaw relationship is an important step in orthodontic diagnosis and treatment planning. The purpose of the present study was to assess the reliability and correlation of seven cephalometric parameters in assessment of sagittal jaw relationship for Sudanese orthodontic patients. Materials and methods: A total of 107 pretreatment cephalo-metric radiographs from the Orthodontic Department archive at the niversity of hartoum that fullled the inclusion criteria were included in the present study. Each radiograph was manually traced; ANB angle, Wits appraisal, APP-BPP distance , Beta angle, W angle, Yen angle and anteroposterior dysplasia indicator APD were identied. The sample was divided into Class I, II and III skeletal groups based on each measurement separately. Person's correlation analysis was performed to assess the reliability and correlation between the measurements among the various study groups (P value = 0.0 level of signicance. Results: W angle was the most reliable method to assess Class I skeletal group, as it showed signicant and correct correlations with all measurements except APP-BPP distance (P = 0.163). ANB angle and APP-BPP distance were the most reliable methods to assess Class II and III skeletal groups, respectively , as signicant and correct correlations with all measurements were recorded. Conclusions: W angle, ANB angle and APP-BPP distance complement each other as clinically appropriate methods for assessment of sagittal jaw relationship in Sudanese orthodontic patients.
Redefining the envelope of discrepancy with temporary anchorage devices (TADs) refers to the use of mini-implants, miniplates, or miniscrews in orthodontics to expand the range of possible tooth movements and correct complex dental discrepancies. By strategically placing TADs in specific locations, orthodontists can create an augmented anchorage system that enables them to move teeth in ways that were previously not feasible. This expanded envelope of discrepancy allows for more efficient and effective treatment of complex malocclusions, including retraction of teeth, correction of severe crowding, open bites, deep bites, and cases with missing teeth. TADs allow orthodontists to have greater control over tooth movements, as they provide stable and reliable anchorage points. Orthodontists can tackle more challenging cases that were considered difficult or even impossible to treat. TADs minimize the dependence on patient cooperation since they provide additional anchorage independent of patient compliance. They can accelerate treatment by allowing orthodontists to move teeth more efficiently and effectively. Thus, treatment duration can be shortened, reducing the overall time patients spend in braces or aligners. Overall, redefining the envelope of discrepancy with TADs has significantly expanded the possibilities in orthodontic treatment, allowing for more precise and efficient correction of complex dental discrepancies.
Introduction:
Extrusion of maxillary lateral incisors during aligner treatment is a difficult movement to achieve accurately. Despite recommendations regarding attachment design, few studies and no prospective trials compare predictability among attachments. This study aimed to compare the efficacy between optimized and horizontal attachment designs for achieving maxillary lateral incisor extrusion during clear aligner treatment.
Methods:
The study included maxillary lateral incisors in 3 orthodontic practices requiring at least 0.3 mm of extrusion during the first series of 20-25 aligners in patients aged ≥16 years who were scheduled to begin clear aligner treatment (Invisalign; Align Technology, San Jose, Calif). Teeth were randomly assigned to receive optimized (O), rectangular horizontal nonbeveled (H), rectangular horizontal incisally-beveled (HIB), or rectangular horizontal gingivally-beveled (HGB) attachments. After the first series, a blinded evaluator measured extrusion using superimpositions with initial and predicted models. Linear models determined the difference in the predicted extrusion percentage achieved on the basis of attachment design. Other covariates were patient age, sex, number of trays, and self-reported compliance.
Results:
Forty patients (74 teeth) were enrolled, and 38 patients (71 teeth) completed the study. Intraexaminer and interexaminer reliability for extrusion measurements was high (intraclass correlation coefficient, 0.985 and 0.991, respectively). The achieved extrusion was significantly less than predicted (mean, 73%; P <0.0001). The average achieved extrusion was 62%, 79%, 78%, and 78% for O, H, HIB, and HGB attachments, respectively, with H significantly more effective than O (P = 0.0403). Horizontal attachments (H, HIB, and HGB combined) were significantly more effective than O attachments (P = 0.0060), with an average difference in achieved extrusion of 14% of the predicted amount (95% confidence interval, 4-23; estimated 76% vs 62%). Horizontal attachments were an estimated 22% more effective than O attachments for extruding maxillary lateral incisors.
Conclusions:
Horizontal attachments are more effective than O attachments for predicted maxillary lateral incisor extrusion between 0.3 and 2.5 mm. The 3 horizontal attachment designs evaluated performed similarly for achieving predicted extrusion.
Trial registration:
This randomized clinical trial was registered and reported at clinicaltrials.gov (NCT04968353).
Protocol:
The protocol was not published before trial commencement.
Funding:
This study was funded in part by the Alexander Fellowship of the Virginia Commonwealth University School of Dentistry, the Southern Association of Orthodontists, and the Virginia Orthodontic Education and Research Foundation. No funding source influenced the study design, the collection, analysis or interpretation of data, writing of the report, or the decision to submit the article for publication.
Hovedbudskap
For å gi pasientene våre best mulige resultater og opplevelse av behandling må behandlere som bruker alignere kjenne til fordeler og begrensninger i bruken av behandlingsmetoden.
Generell kjeveortopedisk viten, forståelse av okklusjon, respekt for de biologiske grenser hos den enkelte pasient og oppstilling av behandlingsmål må være på plass før start av behandling med alignere.
Utvelgelsen av pasienter er ytterst viktig for å respektere læringskurven og bli fortrolig med teknikken.
Simuleringer av behandlingsresultater før oppstart har flere problemer med presisjon av flere bevegelsestyper, hvilket må korrigeres for før behandlingsstart i de mer kompliserte pasienttilfellene.
objective: The present study aimed to assess the cephalo-metric changes in patients with a clinically proven anterior open bite after clear aligner treatment (Invisalign, Align Technology , San Jose, CA, USA). The amount of planned movement was also compared with the amount of movement that actually occurred, as measured on the radiographs. Materials and methods: This retrospective study included 30 patients (11 women, 19 men; mean age 20 years) with anterior open bite (bite depth < 0 mm) treated using Invisalign clear aligners in both arches. The patients received non-extraction treatment with a mean duration of 20 months. Twenty-one parameters (eight linear, twelve angular and one ratio) were evaluated on cephalometric radiographs taken prior to (T1) and after treatment (T2). The amount of planned movement and the actual movement that resulted from the treatment were also compared. results: Statistically significant molar intrusion occurred in the maxilla (0.66 to 0.83 mm) during treatment. Bite deepening was also statistically significant (mean 2.7 mm), but this was not the case for mandibular autorotation. Significant ex-trusions were recorded in the incisors (0.95 to 1.06 mm in the maxilla and 0.38 mm in the mandible). Significant changes in the interincisal angle (mean increase 10.84 degrees) were also recorded due to the significant oral inclin ation of both the maxillary (mean 4.73 degrees) and mandibular (mean 5.53 degrees) incisors. No significant changes to the occlusal plane were noted during treatment. For most movements, the difference between the planned and measured amount was not significant. Conclusion: Clear aligners can be used to treat less severe cases of open bite. The clinical effect of bite deepening is achieved through a combination of intrusion of the lateral segments and extrusion and oral inclination of the frontal segments. In particular, the resulting oral inclination was greater than planned; in general, however, significant changes to sagittal relationships due to mandibular autorotation probably cannot be expected, and significant improvement of facial aesthetics is therefore also unlikely.
A utilização de tecnologia digital é cada vez mais um importante recurso para tratamentos ortodônticos, nomeadamente através do sistema Invisalign®. A procura por tratamentos executados com elevada precisão e suportados por resultados mais previsíveis tem influenciado os avanços dessas mesmas tecnologias, nas quais o Diagnóstico Digital do Sorriso (DDS) tem um papel preponderante. Num caso clínico limite para esta técnica, a opção de um tratamento com o sistema Invisalign® tipo Lite torna-se um desafio, na medida em que se dispõe The use of digital technology is an increasingly important resource for orthodontic treatments, particularly through the Invisalign® system. The demand for high precision treatments and increasingly predictable results, has influenced advances in those technologies, where Digital Smile Diagnosis (DSD) also plays a leading role. In a limiting case for this technique, the Invisalign® Lite treatment option has become a challenge, considering that only 14 aligners are available in the initial phase and 14 additional aligners in the refinement phase. In SPODF 60 INTRODUÇÃO Tendo surgido em 1997, o sistema Invisalign ® teve como ob-jetivo fornecer um aparelho estético e mais confortável aos pacientes 1. Trata-se de um aparelho ortodôntico removível, que segun-do vários autores permite uma melhor higiene oral 2 , é mais estético 3 , menos doloroso e desconfortável 4 , e causa um im-pacto menor na saúde gengival 5. No entanto, há que ter em conta a cooperação do paciente 2 , assim como o maior custo associado 6. Têm sido introduzidas melhorias neste sistema de alinha-dores, que permitem de maneira geral, o controlo de toda a gama de movimentos dentários: intrusão, extrusão, rotação, inclinação simples, inclinação controlada, translação e mo-vimento da raiz 1. Estes aparelhos alinhadores possuem vantagens na corre-ção de mordidas abertas anteriores/interferências posterio-res na protrusão, ao permitir o controlo da dimensão vertical. A espessura do alinhador interoclusalmente cria uma inoclusão no setor posterior (efeito "bite-block"), facilitando assim o movimento intrusivo 7-10. Programas de software como o ClinCheck, permitem vi-sualizar os resultados apenas do ponto de vista da oclusão, mas atualmente, existem tecnologias que permitem exibir o resultado previsto/proposto, de acordo com a estética do paciente 11 .
A critical aspect of the orthodontic treatment is patient cooperation, especially in nonextraction treatment. The introduction of the use of miniscrews in orthodontics and the development of protocols integrated with the Bidimensional Technique (MGBM System) have overcome these difficulties, while maintaining high-quality treatment results. The treatment is divided into three phases and traditional anchoring systems, such as extraoral traction and elastics are replaced by miniscrews. This chapter describes the clinical steps highlighting the mechanotherapy used in the phases of the treatment.
A 35-year-old female patient with dentoalveolar open bite of 4 mm, molar Class I malocclusion, centered midlines, moderate crowding, and labial inclination of the lower incisor was treated with clear aligners to reduce protrusion and close the anterior open bite. The result showed that clear aligners were an effective method with which to correct this malocclusion. The treatment was complete after 18 months. The patient was satisfied with her new appearance and function. (Angle Orthod. 2013;83:913-919.)
Objective:
Based on our previous pilot study, the objective of this extended study was to compare (a) casts to their corresponding digital ClinCheck® models at baseline and (b) the tooth movement achieved at the end of aligner therapy (Invisalign®) to the predicted movement in the anterior region.
Materials and methods:
Pre- and post-treatment casts as well as initial and final ClinChecks® models of 50 patients (15-63 years of age) were analyzed. All patients were treated with Invisalign® (Align Technology, Santa Clara, CA, USA). Evaluated parameters were: upper/lower anterior arch length and intercanine distance, overjet, overbite, dental midline shift, and the irregularity index according to Little. The comparison achieved/predicted tooth movement was tested for equivalence [adjusted 98.57% confidence interval (- 1.00; + 1.00)].
Results:
Before treatment the anterior crowding, according to Little, was on average 5.39 mm (minimum 1.50 mm, maximum 14.50 mm) in the upper dentition and 5.96 mm (minimum 2.00 mm, maximum 11.50 mm) in the lower dentition. After treatment the values were reduced to 1.57 mm (minimum 0 mm, maximum 4.5 mm) in the maxilla and 0.82 mm (minimum 0 mm, maximum 2.50 mm) in the mandible. We found slight deviations between pretreatment casts and initialClinCheck® ranging on average from -0.08 mm (SD ± 0.29) for the overjet and up to -0.28 mm (SD ± 0.46) for the upper anterior arch length. The difference between achieved/predicted tooth movements ranged on average from 0.01 mm (SD ± 0.48) for the lower anterior arch length, up to 0.7 mm (SD ± 0.87) for the overbite. All parameters were significantly equivalent except for the overbite (-1.02; -0.39).
Conclusion:
Performed with aligners (Invisalign®), the resolvement of the partly severe anterior crowding was successfully accomplished. Resolving lower anterior crowding by protrusion of the anterior teeth (i.e., enlargement of the anterior arch length) seems well predictable. The initial ClinCheck® models provided high accuracy compared to the initial casts. The achieved tooth movement was in concordance with the predicted movement for all parameters, except for the overbite.
The 35-year-old male patient was treated at the University of the Pacific, San Francisco U.S.A., as part of an on-going study investigating the feasibility of the Invisalign System of tooth movement. The study called for 40 subjects, 10 with minor, 15 with moderate and 15 with severe tooth deviation. This patient fell into the "moderate" degree-of-difficulty category, due to the position of the maxillary incisors. Treatment time with the initial series of aligners was 14 months. Treatment objectives were met, with the exception of adequate anterior overbite.
In this study, we examined the impacts of age, sex, root length, bone levels, and bone quality on orthodontic tooth movement.
Clear aligners were programmed to move 1 central incisor 1 mm over the course of 8 weeks. Thirty subjects, ages 19 to 64, were enrolled, and measurements were made on digital models (percentage of tooth movement goal achieved). Morphometric features and bone quality were assessed with cone-beam computed tomography. Data from this study were combined with data from 2 similar studies to increase the power for some analyses.
The mean percentage of tooth movement goal achieved was 57% overall. Linear regression modeling indicated a cubic relationship between age and tooth movement, with a decreasing rate of movement from ages 18 to 35 years, a slightly increasing rate from ages 35 to 50, and a decreasing rate from ages 50 to 70. The final decreasing trend was not apparent for women. As would be expected, the correlation was significant between the percentage of the goal achieved and the cone-beam computed tomography superimposed linear measures of tooth movement. A significant negative correlation was found between tooth movement and the measurement apex to the center of rotation, but bone quality, as measured by fractal dimension, was not correlated with movement.
The relationship between age and tooth movement is complex and might differ for male and female patients. Limited correlations with cone-beam computed tomography morphology and rate of tooth movement were detected.
It is not necessary or desirable to treat every case of malocclusion that is presented. Many, if not most, of these children of 3 to 6 years can be safely put under observation in order that the tendency of growth can be noted. A fair percentage will be seen to improve as Nature seeks to correct some earlier period of retarded growth. Others may require the correction of a habit which is obstructing the normal course of development. Still others, such as the cases shown here, require slight mechanical corrections before normal function can be established and the forces of normal occlusion can exert their influence. Practically all of these cases suffer from low and improperly balanced muscle tone, and myofunctional therapy is used both during treatment and afterward to overcome this deficiency. As the span of attention is short in these younger cases, appointments must be kept brief and appliances simple; however, if these conditions are observed, the preschool children will be found to be among our most cooperative patients.
The purpose of this prospective clinical study was to evaluate the efficacy of tooth movement with removable polyurethane aligners (Invisalign, Align Technology, Santa Clara, Calif).
The study sample included 37 patients treated with Anterior Invisalign. Four hundred one anterior teeth (198 maxillary and 203 mandibular) were measured on the virtual Treat models. The virtual model of the predicted tooth position was superimposed over the virtual model of the achieved tooth position, created from the posttreatment impression, and the 2 models were superimposed over their stationary posterior teeth by using ToothMeasure, Invisalign's proprietary superimposition software. The amount of tooth movement predicted was compared with the amount achieved after treatment. The types of movements studied were expansion, constriction, intrusion, extrusion, mesiodistal tip, labiolingual tip, and rotation.
The mean accuracy of tooth movement with Invisalign was 41%. The most accurate movement was lingual constriction (47.1%), and the least accurate movement was extrusion (29.6%)- specifically, extrusion of the maxillary (18.3%) and mandibular (24.5%) central incisors, followed by mesiodistal tipping of the mandibular canines (26.9%). The accuracy of canine rotation was significantly lower than that of all other teeth, with the exception of the maxillary lateral incisors. At rotational movements greater than 15 degrees, the accuracy of rotation for the maxillary canines fell significantly. Lingual crown tip was significantly more accurate than labial crown tip, particularly for the maxillary incisors. There was no statistical difference in accuracy between maxillary and mandibular teeth of the same tooth type for any movements studied.
We still have much to learn regarding the biomechanics and efficacy of the Invisalign system. A better understanding of Invisalign's ability to move teeth might help the clinician select suitable patients for treatment, guide the proper sequencing of movement, and reduce the need for case refinement.
Am J Orthod Dentofacial Orthop 2002;122:310-6
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