| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Clinical Section |
Private practice, Glenelg, Australia
Address for correspondence: Dr E. Ng, 17 Nile Street, Glenelg SA 5045, Australia. Email: eddie{at}ng-global.com
Received 9 April 2005; accepted 8 July 2005
 |
Abstract |
|---|
 Top Abstract IntroductionProcedureCase reportsDiscussionConclusionReferences |
|---|
Key words: Localized, resilient, aligners, thermoformed, active removable appliances
|
Introduction |
|---|
|
TopAbstractIntroductionProcedureCase reportsDiscussionConclusionReferences |
|---|
The main advantages of this treatment are:
It can be assumed that the appliance is easier to work with. It does not require any special intra-oral skills. One of the main disadvantages is the cost. It can be deduced that the high cost may be related to the large number of TARAs required in each case and, more importantly, to the royalty payable to the manufacturer. In this article, a new method is described and cases presented using TARAs fabricated without the use of computers. The aim of developing this method is to attempt to provide a more affordable alternative and further enhance the popularity of TARAs.
There have been several methods advocated in generating orthodontic force in TARAs. The Hilliard Tooth-moving Thermopliers (Raintree Essix Inc., Metairie, USA) uses heat to create localized deformations. Minor tooth movements have been achieved. Invisalign® uses computer-aided fabrication. A common feature of these methods is that orthodontic force is generated by recovery of the wall of the TARA from its deflected position. TARAs fabricated with soft blanks tend to be less effective.4 Using thicker blanks presents a different clinical problem in that the TARAs cannot then be fully seated unless the increments of change are very small. This is particularly evident when the point of applying the force is near the incisal edge or occlusal surface. Invisalign® overcomes this problem by issuing to the patient a series of many TARAs fabricated from a single impression using computer technology. Without the aid of computer, it would be impossible to fabricate so many TARAs at small incremental changes with such accuracy.5
Ideally, the orthodontic force should be sustained through distance and time, of a suitable magnitude and delivered at a point most suited to induce tooth movement in the desired direction.
A closer approximation to the ideal situation may be created by attaching a small amount of resilient material strategically in the TARA to generate orthodontic force. The material is compressed at insertion. It pushes the tooth along as it reverts to its original shape, along with recovery of the deflected wall. This allows sustained forces to be delivered over a longer distance and time. Furthermore, thicker and stiffer blanks can be used for thermoforming. Not only are the resultant TARAs more durable, they are also more retentive and afford better control of the anchor teeth. Such a material should be:
All of the above properties are present in Triad Resiline (Dentsply International Inc., York, USA). This is a urethane dimethacrylate-based material, designed as a light-cured denture soft-liner and it stays resilient for up to a year. It is bondable to acrylic material such as Rain-tree Essix A + plastic (Raintree Essix, Metairie, USA).
|
Procedure |
|---|
|
TopAbstractIntroductionProcedureCase reportsDiscussionConclusionReferences |
|---|
Model preparation
The model is trimmed to a size suitable for subsequent thermoforming. This step must be executed with care. Even minor damage to the cusp tips would greatly affect the fit of the TARA. The trimmed model is examined under magnification for defects. Comparison with the original study model is beneficial. Voids are filled with Triad Gel (Dentsply International Inc., York, USA). Spacers are placed on the model to create room for movement of the target tooth. Triad Denture Base Material (Dentsply International Inc., York, USA) is good for this purpose. It is translucent and allows easy gauging of the thickness of the applied layer. A small amount of Triad Gel is placed at the target tooth on the model to act as an adhesive. A small disc of Triad Denture Base Material is added, and manipulated by a small wax knife into the desired thickness and shape. The spacers are hardened by placing the model into a light-curing box, but if this is unavailable, a composite curing lamp can be used. In Figure 1, pieces of Triad Denture Base Material were placed on the distal aspects of UR3, UR4, UL4 and UL5 to provide room for distal movement of these teeth. The model was a working model of case 3.
|
Insertion
Retention and accuracy of fit are checked. Shortening of the walls reduces the retention, particularly in the embrasures. Too much retention makes it hard to remove the TARA; too little results in instability when the TARA is activated. The occlusion is checked and adjusted to achieve even contact in maximal intercuspation.
Activation
The area where the resilient lining is to be attached is degreased, a thin layer of Triad VLC Bonding Agent (Dentsply International Inc., York, USA) is applied and light-cured for 2 minutes. This is an important step because Triad Resiline does not adhere directly to Essix A + plastic. A suitable amount of Triad Resiline is placed at the target area and light-cured. This is a critical step. The position and amount of material greatly affects the outcome of the tooth movement. More detail is provided in the case reports. After the initial cure, Triad Air Barrier Coating (Dentsply International Inc., York, USA) is painted over the resilient lining and returned to the light-curing box for completion of curing. The last step prevents subsequent discolouration of the uncured air-inhibited layer on the surface of the resilient lining. Excess Triad Resiline is trimmed off using a cross-cut tungsten carbide acrylic bur until the TARA can be seated fully with moderately firm finger pressure. The patient should feel pressure, but no pain. Simultaneous activation of a number of teeth is possible.
Progression
The patient is instructed to wear the TARA all the time except for eating, drinking and performing oral hygiene. After 7–14 days the patient is recalled and more resilient lining can be added by the same procedure. A new TARA is fabricated every 2–4 weeks requiring a new impression. Sometimes tooth morphology may not be conducive to force application in a certain direction. In this situation, small pieces of composite filling material are temporarily attached to the tooth to create more favourable engagement areas.
|
Case reports |
|---|
|
TopAbstractIntroductionProcedureCase reportsDiscussionConclusionReferences |
|---|
).
|
), and UR2 and UL2 were built up with composite (Figure 2c). In this case, tipping was discouraged by using the incisal edges as guides against the straight inner walls of the TARAs. Very small pieces of resilient lining were attached successively to engage the distal surfaces of UR1 and UL1 in order to push the teeth mesially together. Each increment was approximately 1 mm thick and placed as apically as possibly. A piece of composite was attached to the disto-buccal aspect of UR1 to provide a larger engagement area. This was removed when treatment was completed. The result appeared to be tipping and possibly some bodily movement.
Case 2
A Chinese male, aged 23 years presented with a Class I malocclusion with lingually instanding LL2 and LR2 (Figure 3a).
|
). Distal movement and mesial movement were achieved in a similar fashion to case 1. Alignment was accomplished by engaging the lingual surfaces of each tooth at two points; one above the cingulum and the other near the gingiva. Satisfactory tooth alignment was achieved in a relatively short time.
Case 3
A Chinese female, aged 23 years presented with crowded anteriors, quite severely rotated UR1 and Class I buccal segments (Figure 4a). Expansion of the upper arch with proclination of the upper incisors was considered inappropriate in this case. The teeth were barrel-shaped with thick enamel at the contact points, making them suitable for substantial IPR.
|
shows the accumulated spaces mesial to the canines. This case is near completion and included in this article to demonstrate the ability of this method to correct rotations (Figure 4c). Unfortunately, however, the patient moved away before treatment could be completed.
|
Discussion |
|---|
|
TopAbstractIntroductionProcedureCase reportsDiscussionConclusionReferences |
|---|
A relatively large increment of movement was achieved for each TARA through successive addition of the resilient lining. Adhesion of Triad Resiline to the Essix A + plastic was excellent. No delamination was observed in any of the applications involved in the cases presented. The magnitude of forces generated by the resilient lining appeared well matched to the requirement for efficient tooth movement.
Substantial tooth movement was observed in as short a time as 7 days. The longest time that a TARA was used was 30 days. In cases treated by Invisalign® in other studies, the number of TARAs used ranged from 11 to 43 per arch and the treatment times ranged from 11 to 21 months.6–9 The corresponding figures for cases in this report are: 4–9 TARAs per arch and 3–8.5 months. However, it should be stressed that case 1 only involved closing a central diastema and case 3 was close to completion, but not completed. TARAs with resilient lining appeared to be effective in performing a number of tooth movements to treat a range of mild to moderate Class I malocclusions, and may prove to be an expedient and inexpensive method to treat relapse cases. Compared with other TARAs, there may be substantial cost savings, partly due to the lack of need for royalty payments. A less obvious advantage of TARAs with resilient lining may be the flexibility in changing the treatment plan. There is no wastage when changing treatment plan during treatment because the TARAs are made one at a time. Although it seemed labour intensive over a short time, a lot of the procedures could be delegated to staff. More studies are required to examine the capability and cost effectiveness.
Further investigation into combining TARAs with resilient lining and computer fabrication should also be carried out. It is envisaged that the computer creates a precise path of movement, acting like an orthodontic bracket in guiding the tooth along, while the resilient lining provides the driving force. Such a hybrid system may be able to perform more complex tooth movements and used to treat a broader range of cases.
|
Conclusion |
|---|
|
TopAbstractIntroductionProcedureCase reportsDiscussionConclusionReferences |
|---|
|
References |
|---|
|
TopAbstractIntroductionProcedureCase reportsDiscussionConclusionReferences |
|---|
2 Lingerbrink JC, King G, Bollen AM, et al. Quality of life comparison between clear removable and conventional orthodontics. J Dent Res 2002; 81: 463.
3 Boyd R. Dental health: Invisalign treats broader range of patients with malocclusions. Hlth Med Week Atlanta February 4, 2002: 13.
4 Bollen AM, Huang G, King G, et al. Activation time and material stiffness of sequential removable orthodontic appliances. Part 1: Ability to complete treatment. Am J Orthod Dentofac Orthop 2003; 124: 496–501.[Medline]
5 Wong BH. Invisalign A to Z. Am J Orthod Dentofac Orthop 2002; 121: 540–1.[CrossRef][Medline]
6 Vlaskalic V, Boyd R. Orthodontic treatment of a mildly crowded malocclusion using the Invisalign system. Aust Orthod J 2001; 17: 41–46.[Medline]
7 Bishop A, Womack R, Derakhshan M. An esthetic and removable orthodontic treatment option for patients: Invisalign. Dent Assist 2002; 71: 14–17.
8 Miller RJ, Duong TT, Derakhshan M. Lower incisor extraction treatment with the Invisalign system. J Clin Orthod 2002: 36: 95–102.[Medline]
9 Chenin DA, Trosien AH, Fong PF, et al. Orthodontic treatment with a series of removable appliances. J Am Dent Assoc 2003; 134: 1232–9.
This article has been cited by other articles:
|
|
 |
|
  P. Singh, S. Ash, and E. Mizrahi The Quatro appliance: a removable aligner with a changeable labial bow J. Orthod., December 1, 2007; 34(4): 229 - 232. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
