Minor movement, major change Minor orthodontic tooth repositioning is an important component of overall esthetic treatment.
Dr. Robert A. Lowe, DDS, FAGD, FICD, FADI, FACD
To read part 1 of Minor Movement, Major Change, click here.
In the first part of this article last month, I outlined some general concepts and applications of minor tooth movement along with tips for fabricating orthodontic appliances in the Dentsply Raintree Essix system. This month, I am presenting two specific cases.
By way of re-introduction, there are many clinical situations where malocclusion and
Robert A. Lowe, DDS,
FAGD, FICD, FADI, FACD, maintains a private practice in Charlotte, N.C. A Diplomate of the American Board of Esthetic Dentistry,
Dr. Lowe lectures
internationally and is
co-chair of Advanstar Dental Media’s continuing
education advisory board. He can be reached at
704-364-4711 or at
boblowedds@aol.com. misalignment require full mouth orthodontic correction by the dentist or dental specialist. On the other hand, there also are many situations where limited orthodontic treatment of a few misaligned teeth can improve the esthetic and functional result. Minor tooth movement, or esthetic tooth repositioning, is a simple technique to treat minor tooth misalignment involving four teeth or less, moving them over a total distance of up to three millimeters. The corrective movements of the misaligned teeth are accomplished using clear plastic aligners to tip, torque, and bodily move teeth into a more desirable position. Applications of this technique include: minor esthetic tooth alignment of the maxillary and/or mandibular incisor segments; tooth positioning for more ideal placement of porcelain laminate veneers, crowns, or implants; closing small diastemas or spaces; and positioning abutment teeth before bridge or implant placement.
Case 1
Diastema closure that opened between adjacent three-unit bridges four years after placement
This first case demonstrates the use of Essix Cosmetic Aligners to correct a post-reconstruction diastema that resulted from changes in occlusal patterns within the envelope of function. The patient in Figure 1 had adjacent three-unit bridges placed about five years before this photo was taken. It was noted that she had opened a space between teeth Nos. 8 and 9.
Articulation paper shows the contacts on the lingual surfaces support the facial positions of these teeth with a diastema present (Figure 2). To bring these teeth back to the original labial position, an Essix retainer was fabricated to palatally reposition the central incisors (Figure 3). The occlusal contacts on the lingual surfaces must be eliminated, creating room to use tipping force to correct the position of the labial surfaces. After 12 weeks of treatment, the maxillary central incisors again have proper proximal contact restored (Figure 4). It is critical to verify that the occlusion on the lingual surfaces has been equilibrated and polished to accommodate the corrected envelope of function. The retainer is made from Essix ACE 0.035 inch thick plastic to retain the post-operative tooth positions.
(1) A pre-operative facial view showing a diastema that has developed six years after cementation of two anterior three-unit bridges. (2) This lingual view shows how centric contacts have “pushed” the maxillary central incisors facially. (3) The Essix aligner in place putting labial force on the central incisors to reposition them back into the arch form. (4) A facial view of the restored proximal contact between teeth Nos. 8 and 9.
Case 2
Rotated central incisor adjacent to an implant-supported ceramic crown
Figures 5 and 6 show facial and lingual views, respectively, of a case restored with porcelain veneers on teeth Nos. 8 and 9 and an implant-borne ceramic crown on tooth No. 10.
About three years after original placement, the patient presented with a space between teeth Nos. 9 and 10 (Figure 7). The lingual view shows that the space is a result of a mesial rotation of the distal marginal ridge of the maxillary left central incisor (Figure 8). The implant supporting tooth No. 10 is osseointegrated, so it cannot move.
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Figure 9 shows an Essix appliance in place to first tip the maxillary left central incisor palatally. A few weeks into treatment, a tipping force was applied to the distofacial surface to rotate the distal surface in the palatal direction and close the space. Figure 10 shows the central incisor rotated back to place. Figure 11 shows a facial view of the finished case.
These cases show that minor tooth repositioning allows prosthetic tooth position corrections long after a case has been delivered, avoiding remakes. The Essix system demystifies minor tooth movement, a tremendous benefit to any restorative/cosmetic practice.
(5) A pre-operative view showing a porcelain veneer on tooth No. 9 adjacent to an implant-borne ceramic crown in the tooth No. 10 position. (6) The pre-operative incisal view. (7) After three years, a diastema exists between the veneer and the crown. (8) The central incisor has rotated mesially, opening the distal contact. (9) The Essix aligner rotates the tooth distally and closes the proximal space. (10) The lack of occlusal marks on the distal lingual surface of tooth No. 9 means there is space to rotate the tooth back into the arch form. (11) The closed diastema.
Mechanics of minor tooth movement
Movement of a tooth in the arch requires three conditions:
Space
There must be room for a tooth to move and a space for it to move into. The most common ways to create space are extraction and expansion. For minor tooth movement, however, less radical alternatives are just as effective, including:
Interproximal Reduction (IPR), shaving enamel with stainless steel strips in a movement similar to flossing, or cutting away enamel with slowspeed discs or burs.
Air-Rotor Stripping (ARS), high-speed stripping of the proximal surface of a tooth.
Protocol for both IPR and ARS call for enameloplasty of up to 1 mm from each tooth (½ mm per proximal tooth surface). Several adjacent teeth are stripped to gain up to 3 mm. Dentists generally adopt ARS and IPR readily because these procedures are similar to others they perform with a handpiece every day, but on a much more limited scale (like preparing a tooth for a crown).
Force
Pressure must be applied in the direction you want to move the tooth.
Brackets rarely are needed for minor tooth movement. In fact, the best starting point for moving teeth up to 3 mm is an Essix plastic retainer appliance created from a conventional pre-operative stone model using a thermoforming machine.
The force is provided simply by placing a bump (dimple) on the Essix appliance using one of 11 Hilliard Thermoplier Pliers (Dentsply Raintree Essix). Each are designed to make exactly the right size and shape of bump to create rotation, bodily movement, tipping, or torquing movement. Thermopliers position each bump with complete precision.
These tools are heated to the correct temperature to indent the appliance perfectly, so the plastic retains its shape and the bump maintains its force. The same plier then can increase the bump, applying additional force over time, without taking a new impression and restarting the process to fabricate a new appliance.
Time
Movement must be incremental over a number of weeks.
The Essix approach simply increases the force by increasing the depth of the bump as the tooth moves incrementally over time.
Every few weeks, the patient returns and the bump is made larger (deeper), again using Hilliard thermopliers. The desired tooth movement usually is achieved after three adjustments–about three to six months of wearing the appliance, depending upon patient compliance. One millimeter of movement per month is expected when the appliance is worn full-time except during eating. After the tooth (teeth) are moved to the desired position, location can be retained by making an Essix retainer from a model of the post-operative position.