A Clinical Case Treated With Invisalign

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A Clinical Case Treated with Clear AlignersBy Fernando César Torres, Renata Pilli Jóias, Fernanda Cepera, Luiz Renato Paranhos, Derek Sanders

F E A T U R E This article has been peer reviewed

Abstract: !ere are a wide variety of techniques, prescriptions and materials that can be used to correct malocclusions. Esthetic and discrete appliances have gained popularity in recent years and there seems to be a continual search for new materials that can provide similar orthodontic results. !is article will describe the relevant aspects of clear aligners and present clinical cases to document some of the applications of Invisalign®. Key words: removable orthodontic appliances, dental esthetics.

ntroduction and Literature Review!e e"ectiveness of orthodontic treatment using conventional fixed appliances has been described for years. In the early years of the

orthodontic profession, every tooth required banding. Bonding of brackets was introduced almost forty years ago and the search for esthetically pleasing appliances has evolved ever since. Esthetic treatment options include lingual brackets,1-2 polycarbonate and ceramic brackets1,3

and more recently, removable aligners.2-3 Drastic improvements in clear aligner treatment have taken place and the popularity of these appliances has steadily increased among many patients,4 especially adults who are often reluctant to wear fixed appliances.4-5 !e first report of an elastic and removable tooth positioning appliance, built from an individualized setup of plaster cast models, dates back to 1945.6 Since then, several di"erent types of removable appliances have been developed with the purpose of correctly positioning teeth in the dental arch.7-10 Among these appliances are the clear retainer8 and the Essix appliance,9 which have been associated with interproximal reduction. !ese appliances are considered to be tedious since periodic impressions and setups are required in order to produce new aligners. !e popularity of these appliances has continually decreased, since a considerable amount of time was required from the patient and orthodontist. !e Invisalign® system (Align Technology, Inc, Santa Clara, California, USA) was introduced in 1997 using software technology developed for treatment diagnosis and simulation. !e Invisalign® system quickly gained popularity as one of the most esthetic options for tooth movement. !e system is a sequence of clear aligners that are worn sequentially to gradually correct misaligned

teeth. Invisalign® combines CAD-CAM (computer-aided design and manufacturing) technology and uses 3-D images of the patient’s teeth which have been obtained from an addition silicone impression. Treatment is virtually simulated and the aligners required for treatment are personalized and manufactured in a series, at the same time.11-12 Invisalign® is currently the most popular among serial aligner treatment, which is most likely due to its accuracy and the ability to manufacture all aligners at once from a single mold.11-12 !ere is also a support system given to practitioners, which includes a computerized simulation of the correction of the malocclusion. !is virtual representation of tooth movement is a valuable tool that can be used to inform patients of how their teeth will look once finished with treatment. Invisalign® can be an interesting treatment alternative for the demands of many patients. A few aspects of this system will be discussed using literature resources and clinical cases.

Invisalign®!e Invisalign® system is produced by Align Technology Inc. (Santa Clara, CA, USA) and is based on 3-D technology using CAD-CAM. !e “aligner” is made of polyurethane and can be used to correct various types of malocclusions. It is designed not to employ wires or other metal accessories used in conventional fixed appliances. Only accredited clinicians can use this system. Once accredited, the practitioner selects the case to be treated, makes the diagnosis, treatment plans and sends to Align Technology a polyvinylsiloxane impression (addition silicone) using a metal tray (Figure 1) or a non-metal tray from Invisalign (it must be noted that the company suggests using only their plastic trays), a bite registration

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in maximum intercuspation, a panoramic radiograph, a lateral cephalometric radiograph, and extra- and intra-oral photographs. 4-5, 13

!e impressions are scanned (destructive scanning) and a 3-D version of the patient’s dental arches and occlusion are created in the computer, so corrections can be made virtually, using CAD (Computer-Aided Design). !e virtual file (ClinCheck) (Figure 2) is sent for verification by the practitioner, who may require changes before approving the step-by-step protocol developed for treatment. Once the ClinCheck is approved, the CAM (Computer-Aided Manufacturing) phase using stereolithography begins, in order to produce the models for manufacturing the patient’s aligners (Figure 3). !e company guarantees slow tooth movement (linear movement: 0.25mm/month; angular movement: 2º/month) without occlusal or interproximal interference.14 !erefore, the number of aligners for each case depends on the complexity of necessary movements, resulting in variable treatment costs. !e practitioner receives all aligners approximately 45 days after approving the ClinCheck. It is important to remind the patient that it is not possible to interrupt treatment and use the same aligners at a later time.15

Invisalign® (see example at Figure 4) is indicated for the treatment of mild to moderate crowding (1-6 mm), mild to moderate spacing (1-6 mm), dental crossbites (non-skeletal) and relapse from previous orthodontic treatment.16 More complex treatment involving extractions, distal movement, deep bites and periodontal cases have been reported in literature. 4-5,14 !is is probably due to improvements in the system, which now allows for the simultaneous movement of all teeth. Attachments can be used to give more retention to the aligners during correction of the curve of Spee, for extrusion, rotation, translation, and torque control.4

Replacing the aligners every two weeks is the most e#cient form of treatment and causes less sensitivity when aligners are changed.15,17 !e aligners should be removed only during meals and for oral hygiene, and should be worn at least 20 hours a day.14 Aligners should be cleaned using a toothbrush and toothpaste. For post-treatment retention, the last aligner may be worn in the upper arch, with a 3x3 retainer in the lower arch.

Clinical Case A 26-year-old female presented with a Class I malocclusion and an orthognathic profile. She was in the permanent dentition with retroclined maxillary central incisors, moderate overbite, spacing distal to the maxillary canines and mild crowding in the mandibular arch (Figure 5). Her primary concern was the alignment of her maxillary incisors and she refused to have fixed appliances. !e treatment objectives using Invisalign® were to align her front teeth, close space in the maxillary arch and alleviate crowding in the mandibular arch (see treatment results simulation in Figure 6). !e occlusal

Figure 1

Figure 2

Figure 3

Figure 4

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goals were to maintain the Class I buccal segments, obtain a normal overbite and overjet and achieve a functional occlusion. Invisalign® treatment involved 24 upper and 10 lower aligners. Attachments were placed on several teeth to achieve a more predictable tooth movement using aligners. !e patient wanted to reduce treatment time as much as possible and was instructed to change the aligners every 10 days instead of 14 days. After 8 months of initial treatment, a Case Refinement with 7 more aligners was needed to finish the maxillary arch. Once treatment was completed (Figure 7), a bonded lingual fixed retainer was placed on the maxillary incisors to prevent relapse. For retention, the patient was given a maxillary hawley wrap around and a mandibular modified spring aligner. !e patient was instructed to wear the removable appliances full time for 6 months and nighttime thereafter.

Discussion and ConclusionSome authors have questioned whether the results obtained over the course of treatment with aligners were the same as the virtual simulation in ClinCheck, however virtual images have shown to be approximately the same as the patient’s final occlusion.12

!e aligners have demonstrated excellent results in anterior alignment and good improvement in occlusion, transverse relationships and overbite correction. It is also possible to notice a reasonable improvement in midline position and overjet.17-18 Invisalign® can be quite e"ective in correcting deep bites and mild crossbites by facilitating anterior intrusion while discluding the posterior teeth. Patients with bruxism are good candidates for this treatment, as the aligners prevent occlusal wear and reduce pain in facial muscles and joints. Patients with extensive restorations and/or prostheses can benefit as well, as bonding orthodontic accessories can be more di#cult.4 Some articles suggest the possibility of combining Invisalign®19 with orthognathic surgery.

Figure 5

Figure 7

Figure 6

Figure 8

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Many cases can be treated using only aligners, with treatment times ranging from six months to one year. In some situations, such as in cases requiring premolar extractions, the combination of complementing techniques becomes necessary20 since obtaining translation, extrusion, torque and root inclination movements are di#cult with clear aligners alone.5 !ere are many advantages of the Invisalign® system when compared to other orthodontic techniques such as improved esthetics, ease of use, greater comfort, improved hygiene, and being able to view the ClinCheck®. Patients are rarely disappointed with their treatment results21 since they have already viewed and approved their ClinCheck®. !ere are several disadvantages to removable aligners, such as the inability to achieve root movement and extrusion and Invisalign® treatment is not indicated for all cases.5

When compared to conventional fixed-appliance treatment, aligners caused less pain and had less negative impacts on patients’ lives during the first week of use. However, there was a higher relapse rate23 in the post-treatment period.22 Aligners cause less plaque buildup than conventional appliances, but periodontal conditions are similar for both appliance types.24 With regard to root damage, a study25 compared a given type of removable aligner with fixed orthodontic appliances, and demonstrated using micro-computed tomography that root resorption was similar for both groups, possibly due to the light forces (25g) being used to move the teeth. Forces are considered light when they move teeth without causing painful sensitivity for more than 3 days. New materials continue to revolutionize modern orthodontics by reducing treatment and chair time, minimizing discomfort and optimizing esthetics.5 !e Invisalign® system o"ers the practitioner and the patient a peek into the future since results can be viewed before starting treatment. !e practitioner must be aware that using the system requires a learning curve and clinical experience is traditionally acquired with the evolution of cases. In order to ensure a predictable treatment outcome, the practitioner should closely follow the case selection criteria.22

It is essential to keep in mind that Invisalign® is yet another treatment modality that can be used for tooth movement. Compared to traditional fixed appliances, Invisalign® is a removable technique that can provide improved esthetics, increased comfort, reduced chair time and better oral hygiene.26

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and supervision for permanent retention. J Clin Orthod 1993;27:37-45.

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15. Bollen AM, Huang G, King G, Hujoel P, Ma T. Activation time and material sti"ness of sequential removable orthodontic appliances. Part 1: ability to complete treatment. Am J Orthod Dentofac Orthop 2003;124(5):496-501.

16. Turpin DL. Clinical trials needed to answer questions about invisalign. Am J Orthod Dentofac Orthop 2005;127 (editorial):157-8.

17. Clements KM, Bollen AM, Huang GH, King G, Hujoel P, Ma T. Activation time and material sti"ness of sequencial removable orthodontic appliances. Part 2: dental improvements. Am J Orthod Dentofac Orthop 2003;124(5):502-8.

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19. Womack WR. Four-premolar extraction treatment with Invisalign. J Clin Orthod 2006;40(8):493-500.

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21. Honn M, Goz, G. A premolar extraction case using the invisalign system. J Orof Orthop 2006;67:385-94.

22. Miller KB, McGorray SP, Womack R, Quintero JC, Perelmuter M, Gibson J, Dolan TA, Wheeler TT. A comparison of treatment impacts between invisalign aligner and fixed appliance therapy during the first week of treatment. Am J Orthod Dentofac Orthop 2007;131(3):302.e1-302.e9.

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23. Kuncio D, Maganzini A, Shelton C, Freeman K. Invisalign and tradicional orthodontic treatment postretention outcomes compared using the American board of orthodontics objective grading system. Angle Orthod 2007;77(5):864-9.

24. Miethke R, Vogt S. A comparison of the periodontal health of patients during treatment with the invisalign system and with fixed orthodontic appliances. J Orofac Orthod 2005;66:219-229.

25. Barbagallo LJ, Jones AS, Petocz P, Darendeliler MA. Physical properties of root cementum: part 10. Comparison of the e"ects of invisible removable thermoplastic appliances with light and heavy orthodontic forces on premolar cementum. A microcumputed-tomography study. Am J Orthod Dentofac Orthop 2008;133(2):218-27.

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