TWO PATIENTS TREATED WITH INVISALIGN ® : CROWDING RESOLVED VIA EXPANSION AND AN ANTERIOR OPENBITE CASE WITH A DISCUSSION ON OVERCORRECTION

Treatment by:

Ross J. Miller DDS MS and Arthur Kamisugi DDS MS

Authors:

Ross J. Miller DDS MS and Mitra Derakhshan DDS MS

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ABSTRACT:

Invisalign® was introduced to the orthodontic community in 1999. Currently, Align Technology has over 60,000 patients using its product and has shipped over two million individual Aligners. For those doctors using Invisalign, this treatment method has opened the door for many adolescent and adult patients that decline fixed appliances. However, the doctor must be aware of the limitations of the system, which include rotating round teeth, extrusion of individual teeth and perfect translation. All these limitations can be overcome by good treatment planning and using small sectionals where needed.

INTRODUCTION:

We are assuming that the reader is familiar with the Invisalign process and ClinCheck, if not please refer to Align Technology’s web site www.invisalign.com. Presented here are two patients that were treated with Invisalign. One of which is a crowding case and the other an open bite case. Each of these cases illustrates something a little different. The first case incorporates expansion into both arches. The second utilized the posterior bite plane effect of the appliance itself as well as anterior retraction. Both illustrate the nature of this new technology in that we must look at ClinCheck carefully, overcorrect anterior rotations, and understand the effects of the appliance. They also show the interesting nature of virtual treatments applied with clear appliances. The doctor must have a good understanding of the biomechanical properties of these appliances in order to harness their potential for the treatment of doctor’s patients. Occlusal coverage appliances have certain properties that will affect each patient differently. The bite plane effect is valuable as part of the treatment of open bite patients. For deep bite cases it may be helpful for expanding or distalizing where the bite might have a tendency to open.

CASE 1: Upper and Lower Crowding Treated with Expansion

Chief Complaint: This 32 year 11 month old female presented with the chief complaint of lower anterior crowding and rotated upper teeth.

Initial Diagnosis: Class I malocclusion with upper and lower anterior crowding. Her lower midline is off to the left 1mm. She has an anterior crossbite on the lower left canine and upper left lateral. The upper laterals are severely rotated. She has a history of restorative treatment. (Fig 1-5)

Fig 1	Fig 2	Fig 3
Fig 4		Fig 5

History: No medical conditions and no history of orthodontic treatment.

Panograph (Fig 6): Her third molars were previously extracted and there was no apparent pathology. She did mention that upon eating hard food, she does experience clicking but there is no pain associated with the clicking.

Cephalograph (Fig 7): The patient’s head appears tipped downward in the ceph. Deviations from the accepted norms are that the upper incisors are retroclined.

Treatment Plan: The upper and lower crowding was resolved by upper and lower expansion followed by anterior interproximal reduction. Looking at her virtual treatment plan (Fig 8 and 9), the posterior teeth (4-7) were expanded first to create space, then the canines (3-3) were moved distally into the space created by the expansion. Lastly, the anterior teeth (2-2) were aligned. The upper lateral incisor rotations should have been overcorrected.

Case Summary:

Start Date: 6/20/01

Total aligners: 23 upper, 20 Lower

Retention Start Date: 5/2/02 upper 5/9/02 lower with Invisalign retainers.

Time to completion: 11 months active treatment.

Discussion: This patient was treated to completion to the satisfaction of the patient and the orthodontist. The upper and lower crowding was resolved and midlines coincident. (Fig 10-14). There could have been more mesial rotation of the upper lateral incisor for better anterior alignment. This may be due to the aligner lag and the difference between the virtual and biological treatment, which is overcome by virtual overcorrection to achieve the final, desired clinical result. Upper lateral incisor rotations do need overcorrection. It is also important to make sure that there is enough interproximal clearance for the tooth to rotate as was in this case. No significant changes are seen on the final panograph (Fig 15) A final cephalograph was not taken as there was not much anticipated change in the incisor position since the majority of crowding was to be resolve with expansion and then interproximal reduction.

CASE 2. Class I openbite with upper and lower proclination and spacing.

Chief Complaint: This 45yr 1mo female presented with a chief concern of spacing.

Initial Diagnosis: Class I malocclusion with an anterior openbite and upper and lower generalized anterior spacing. Her midlines are coincident. The photos indicate good oral hygiene with normal attached gingiva. Restorations are present in the posterior segments. There is some recession present on the lower central incisors as well as the upper first premolar and molars. (Fig 16-20)

History: No medical or dental contraindications to treatment.

Panograph: The roots on the lower incisors appear to be foreshortened, this is due to the initial excessive proclination of the lower incisors. As the panoramic radiograph was taken, the lower incisors were not within the central trough and they appear to be foreshortened due to their angulation. All other structures seem to be within normal limits. (Fig 21)

Cephalograph: The upper and lower incisors are protruded and proclined. There is an openbite and lip strain during closure that can be seen on the ceph. (Fig 22). The patient is bimaxillary prognathic.

Treatment Plan: The Class I occlusion was to be maintained. Upper and lower spaces were closed with retraction of the incisors. As the incisors were tipped back, this was to provide some relative extrusion and help close the openbite. The virtual treatment predications are shown below (Fig 23 and 24) and indicated the amount of movement or tip back of the incisors. In addition, to preserve anchorage, the virtual treatment plan did not move the posterior teeth.

Case Summary:

Total aligners: 28 upper, 31 lower

Time to completion: 16 months active treatment.

Discussion: The treatment objectives were met. The patient was happy with the treatment. The incisors were relatively extruded to help close the open bite Attachments were placed on the upper and lower canines to aid with retention as the incisors were being retracted and tipped back. In addition, due to the thickness of the aligners and the occlusal forces being placed on the aligners, there may have been a bite-plane effect that caused some posterior intrusion. Notice that this bite-plane effect may have occurred without planning for it on ClinCheck. This case illustrates a combination of bite plan effect and relative extrusion (extrusion as part of lingual crown tip) work well to close bites. From the frontal photo, a small black triangle space can be seen between the two lower central incisors. If one takes a look back at the virtual treatment plan, this same space can be seen. This reiterates the importance of re-viewing the virtual treatment plan carefully as well as overcorrecting for space closure. There was no final panograph or cephalograph taken.

CONCLUSION: Invisalign can work for a broad range of cases. There is a leaning curve associated with using the appliance and evaluating ClinCheck. Reviewing and evaluating ClinCheck has two components, reviewing the set-up as well as the staging. Not only is it imperative to view the end result of the final dentition, it is important to view how the teeth move from their initial to their final position. Consider what is the path of movement, is there adequate space for the teeth to move, is IPR needed? ClinCheck becomes your 3D diagnostic set-up and virtual prediction of treatment. The Aligners many not provide all the forces necessary when the case is set-up to ideal, over-correcting movement passed ideas on the virtual set-up, may lead to more ideal clinical results. This article clearly demonstrates 2 cases in which successful virtual treatment plan treated was carried out using Invisalign appliances. The greater your experience with Invisalign, the greater the number of patients you can serve in your practice and improve their outcomes.