Innovative. Techniques with Clear Aligners. Success in Rotating or Extruding Canines by Dr. Perry Jones. 30 the Journal: volume 01- issue 01

Transcription

1 Innovative Techniques with Clear Aligners Success in Rotating or Extruding Canines by Dr. Perry Jones Problem: One of the difficulties faced by dentists who utilize Clear Aligner Treatments (CAT), such as Invisalign, is to successfully rotate and/or extrude teeth that have a rounded shape, especially canines. Canines, with their large surface area and concave proximal root surfaces, tend to offer a root morphology that is more resistant to rotation. Additionally, extrusion of any tooth has been a recognized challenge with clear aligner systems, because the V shaped aligner almost always has difficulty gripping the V shaped tooth; this difficulty is especially pronounced when a tooth has minimal interproximal undercuts, as is the case with most canine teeth. Invisalign advances, such as the latest G3 and G4 innovations have greatly improved the predictability of more complex movements. The development of optimized attachment shapes, certainly aid rotation and extrusion movements. These attachments are unique to the Invisalign system and offer a much improved force system that can more predictably execute clinical movements. Figure 1: The maxillary canine with an optimized attachment exhibits movement lag at the incisal edge as well as a misfit of the bonded attachment to aligner reservoir. Dr. Jones is a graduate of Virginia Commonwealth University School of Dentistry, where he now serves as Director of Continuing Education and Faculty Development, as well as Adjunct Faculty, Associate Professor, Department of Oral Maxillofacial Surgery. He is Director of the Virginia Academy of General Dentistry MasterTrack program, and is a Master of the Academy of General Dentistry. One of the very first GP Align Technology education speakers, Dr. Jones lectures extensively and has given some 300+ Invisalign and itero presentations. Currently, Dr. Jones serves as Director of Education for AACO, and maintains an active private practice in Richmond, VA. Figure 2: Occlusal view of the rotation movement lag. However, space, force, and time are the three key elements to tooth movement, and even with the use of Invisalign optimized attachments, tooth movement may lag and some movements may be most challenging to execute clinically. Fig.1-2 This article will offer an auxiliary method that will help clinicians predictably create space, create a properly directed and sufficient force, and, assuming patient compliance, time for desired tooth movement. Over the years, various helpful adjunct techniques have been suggested. One such proposed technique involves modifying 30 the Journal: volume 01- issue 01

2 Solution: This article will describe a technique that can succeed in simultaneously extruding and rotating stubborn canines. These stubborn canines often exhibit significant movement lag that can threaten successful completion of the case. Figure 3: Completed removal of the composite resin attachment material with a multi-fluted high speed carbide finishing bur. The basic concept is to create a model or cast of the arch with the lagging canine. Material is added to the model/cast to create space via a movement bubble. A bonded button is attached to the tooth to be moved. The thermoplastic appliance is then modified with thermoforming heated pliers that form an attachment dimple on the appliance, and elastic forces are applied with chain elastics or single loop elastics. The patient is given proper instructions for placement and removal of the chain elastic. Given a compliant patient, this technique will work with reasonable certainty and successfully rotate and extrude difficult teeth such as canines. Technique: 1. Carefully evaluate the available intraoral interproximal space with dental floss. Check the IPR values. If the contacts seem tight, perform 0.10mm of interproximal reduction by either using a slow-speed disc, or a diamond coated strip manually or mechanically. This author prefers using the slow-speed disc. Figure 4: Stone model with Triad gel material formed to create a movement bubble. Figure 5: The labial view of the canine tooth, treated with conventional etch-bonding technique. the clear aligner with a cut that creates a slit for an attachment hook, and placing a bonded button onto the tooth. Various force elastics are then placed between the aligner slit and the bonded button, to create forces that will successfully encourage tooth movement. Unfortunately, this technique is often unsuccessful for several reasons: 1. As the cut slit weakens the aligner, the cut area is often the point where the aligner fails and breaks. 2. The cut slit is often challenging to hold the elastic force, as the slit may bend/break and the slit may cut the elastic. 3. Further, the aligner has proximal plastic that offers resistance to the adjunct rotation forces and, therefore, the tooth resists rotation. 2. Remove any composite resin attachments from the lagging tooth and polish the tooth Fig Take an impression of the arch with either VPS or alginate. A digital itero scan is an option, and a refractory model made of a virtually unbreakable plastic material may be ordered. If VPS or alginate is used, a stone model is poured. 4. When set, the model is trimmed and cleaned. Dentsply Triad gel is used to cover the lagging canine. It is crucial to be absolutely certain to free the proximal areas and the incisal area, so as to allow for the needed extrusion and rotation movements of this canine. This step is very important as the movement bubble must create the space to allow the tooth to move Fig.4. The operative principle is to create space for movement. Add Triad clear gel to the labial, lingual, and incisal areas to create the movement bubble. 5. Using the above model or cast, a vacuum-formed suck down, of Essix ACE.040 thermoplastic material is completed. There are several important steps for success. The vacuum machine must be red hot before moving the element over the material to be heated. Use only ACE.040 thermoplastic material, and do not allow more than 3/8 inch material sag. The 3/8 inch sag value is about equal to the flange thickness of the material holder. These cautions are critical to appliance strength. Immediately quench the material with either a freeze spray or cold water. Remove the appliance from the cast/model and trim it, such that the thermoplastic material extends 2-3mm beyond the cemento-enamel junction of the teeth. 6. Using conventional bonding techniques Fig.5-6, a bonded button (available in the Align auxiliary kit), is bonded to the Academy for Clear Aligner Therapy 31

3 Innovative Techniques the labial of the lagging canine. The button should be placed slightly coronal to the gingival margin, in a position that optimizes the applied force. In this case, the button was placed to the mesial as the tooth rotation force was counterclockwise toward the distal. Light cure the adhesive and remove excess with scalers and/or finishing burs Fig.7. The Align kit includes buttons, etch, bonding liquid, and bracket adhesive. 7. Cut an ovoid slot in the labial of the thermoplastic appliance, such that it clears the bonded bracket and allows room for the bracket to rotate/extrude Fig The Rule of 3 s is applied to the elastic force system for both positioning the posterior buccal and lingual attachment dimples, as well for as determining the minimal movement force. If using a single loop elastic force, place a 1/8 inch x 8 oz. elastic over the labial button on the lagging canine Fig Using a hemostat, pull the loop to the distal and note where the elastic loop is stretched two more loops for a total of 3 loops Fig.10. Mark this area, as this is where you will want to place the attachment dimple described in the following step #s 10 and 11. In this case, the retention dimple was placed on the buccal of the first molar. 10. Using a purpose-made Essix Microramp plier, heat the prong end Fig.11 to about 200 degrees F. Note the heat source must be a butane flame. An inexpensive cooking Crème Brule torch Fig.12 is an excellent heat source. A thermocouple may be used to quantify the heated value, or, alternately, you may simply take a cold plier tip, apply a butane flame and count This gives an approximate value sufficient to heat and stretch the plastic. The idea is to create a dimple that extends from the inside to the outside of the thermoplastic. This dimple will be further modified to create an attachment point for the elastics Fig Using a sharp instrument, such as a 12B Bard-Parker scalpel blade, cut carefully at the base of the dimple on the side away from the lagging tooth. Cut about 1/2 of the ovoid diameter to create a retention hook. Fig The patient is instructed to wear the appliance and apply the elastic forces constantly, except when eating or when cleaning the teeth. Give the patient several long lengths of chain elastic or a bag of individual elastics such as 1/8 x 8 ounces. This clinician has had most success using chain elastic as the force system Fig The hooks can easily be preloaded on the movement appliance Fig.19, making it more convenient for the patient to stretch the chain elastic to place over the bonded button onto the lagging tooth. The patient is given inexpensive non-surgical grade small straight hemostats to take home and make application of the chain elastics easier. The intraoral occlusal view shows the appliance loaded for simultaneous rotation and extrusion Fig.20. Figure 6: Conventional bonding technique, light curing of the bonding agent. Figure 7: The attachment button is bonded in place in a manner that maximizes the force applied; in this case, to the mesial, because the force applied is to the distal. Figure 8: Small curved scissors used to modify the labial aspect of the thermoplastic appliance to create an ovoid cut-out and allow room for the bonded button. Figure 9: The rule of 3 is applied to stretch an elastic loop with a small hemostat to determine the location for the appliance retention dimple. 32 the Journal: volume 01- issue 01

4 Figure 10: The rule of 3 demonstrating the stretched elastic and the location of the heated plier retention dimple that was placed on the buccal of the first molar. Figure 14: Occlusal view of the retention dimple created with the MicroRamp heated pliers. Figure 11: Butane heat source, used to heat the prong end of the Microramp heated plier to about 200 degrees F. Figure 15: Occlusal view of dimple cut, created to allow for retention of the elastic force. Figure 12: Butane heat source: Crème Burle cooking torch. Figure 16: Occlusal view of the elastic in place, in the retention dimple hook. Figure 13: Heated plier used to create a dimple from the inside of the thermoplastic appliance to the outside. Figure 17: Preferred elastic force system of clear chain elastic with an extra tail to aid in elastic placement. the Academy for Clear Aligner Therapy 33

5 Innovative Techniques 14. In general, movement is successful after 3-4 months Fig If movement is successful, the patient may resume wearing the next aligner in sequence, and the movement appliance can be discarded. If there had been an attachment that, for purposes of this technique, had been removed (as per step #2), it may now be placed again, by ordering and utilizing a new attachment template from Align, for that specific stage. Or, instead, the original attachment template may be used for this purpose, by carefully cutting a custom single tooth template from the original attachment template. 15. Aligner wear, with the planned sequential Invisalign aligners, may now resume and continue until treatment is complete. Figure 20: Occlusal view with the thermoplastic movement appliance in place with simultaneous application of extrusion and rotation chain elastics. Summary The described adjunct/auxiliary technique can be used successfully to rotate and extrude rounded teeth such as canines, with reasonable certainty. The technique is inexpensive, does not require an outside lab, and is easy to create in-house, with commonly available materials and instruments. Given a sufficient and properly directed force, sufficient space, and patient compliance, canines that have been exhibiting movement lag can be either extruded or rotated successfully. Simultaneous rotation and extrusion can also be treated, as described, with excellent results. n Figure 21: Occlusal view of the lagging canine tooth, demonstrating the degree of rotation lag, prior to application of the forces created with the described thermoplastic movement appliance. Figure 18: Placement of elastics to execute simultaneous extrusion and rotation. Note the extra length loop of chain elastic that makes it easier for the patient to place the chain elastic. Figure 22: Occlusal view, after movements were completed with the described thermoplastic movement appliance. Figure 19: The appliance may be loaded with the chain elastics prior to placement in the patient s mouth. Note the lingual retention dimple created on the cuspid. An elastic stretched from the lingual rentention dimple of the cuspid to the attachment button on the buccal of the cuspid, will cause extrusion of this lagging tooth. 34 the Journal: volume 01- issue 01