In part 2 of a series, Dr. S. Jay Bowman continues his look at instruments that help increase the utility of aligners and expand the scope of appropriate applications
Contact points to accent aligners
The two accent pliers in the Clear Collection (i.e., The Horizontal and The Vertical) (Figures 1-2) were designed to enhance desired tooth movements by employing “contact points.” Although overcorrection is a critical aspect that is integral to aligner treatment planning, there are occasions when the virtual setup does not predictably produce the desired result. In fact, researchers have reported that a percentage of tooth movement prescribed for a setup is simply not translated from plastic into the dental results.1-4 The flexibility of plastic, the potential errors transmitted from inaccuracies of PVS or scanned “impressions” and creation of models, im- precisions in the vacuum process of fabricating aligners, and the fact that all teeth do not move to the same degree when exposed to forces exerted by the trays can all lead to incomplete correction.
To improve the predictability of desired tooth movement, The Vertical and The Horizontal pliers were designed to produce shallow impressions in the aligner plastic to contact specific surfaces of individual teeth. These indentations are intended to generate an enhanced “contact point” and/or to create a mechanical couple to move a tooth in a desired direction. These “accents” may help avoid another series of “refinement” aligners with their attendant additional scans/impressions and associated virtual setups — potentially reducing treatment delays and the “hassle factor.”
The control of rotations is often a challenge with clear aligners. The Vertical
(Figure 1) is an instrument designed specifically for enhancing the correction of rotated teeth with clear aligners or even during minor tooth movement when using simple, clear retainers. Rotating upper laterals and cuspids is often problematic,5,6 especially since aligners do not have a large surface area contact on laterals. Consequently, these incisors can get left behind, resulting in another form of “lag” or loss of tracking. The Vertical is used to produce an indentation at the mesial or distal of a specific tooth in the facial and/or lingual aspects of the aligner plastic. These indentations are made without heating the pliers and at a very shallow depth so as to not compromise the integrity of the plastic (Figure 1). The intent is to add contact points to accent the rotational couples that were prescribed when creating a virtual treatment setup. This certainly contributes to the concept of overcorrection that is key to correcting rotations with aligners.
The Vertical can also be used at the line angles of teeth to accent other types of tooth movement. For example, placing a vertical indent at the mesial of maxillary first molars (in the buccal and/or lingual plastic) will enhance molar distalization (Figure 1). When placed at the distal, the indent will assist molar protraction. Vertical indents at the embrasures of incisors or premolars will assist root paralleling, especially in extraction scenarios.
Another option is to use The Vertical to produce a very slight indent at the junction between the incisal or gingival surface of the plastic and a composite aligner attachment. This may enhance the sharpness of the conformation or contact between plastic and attachment to avoid loss of tracking noted as an “escaped attachment.” The Vertical can also be used to produce an indent in aligner plastic in the middle one-third of the facial or lingual of a tooth to give a mild nudge for in-and-out or labiolingual discrepancies, including minor tooth movement with clear retainers.
There are instances where we would like to accentuate root torque for specific teeth during clear aligner treatment. In other instances, there is a need to increase the retentiveness of aligners or clear retainers. The Horizontal (Figure 2) is an instrument designed to accent labial or lingual torque for individual teeth, and it can also be used to simply increase the retentiveness of clear aligners or retainers.
Either labial or lingual root torque can be a challenging aspect of tooth movement for clear aligners. This is typically due to the fact that the plastic is more flexible near the gingival margins, diminishing the required forces. The Horizontal can be used to produce an indentation on either the lingual, buccal or both sides of the aligner, anywhere along the aligner plastic to emphasize torque (Figures 2A-2B). Commonly, these “impressions” in the plastic are positioned at the gingival margin on the facial of an incisor to apply a contact point to emphasize lingual root torque. In contrast, the indent is placed on the lingual to enhance labial root torque.
Another option is to use The Horizontal to produce a very slight indent at the right angle junction between a rectangular aligner composite attachment and the facial surface of a tooth (Figures 2C-2E). This indent may enhance the sharpness of conformation or contact between the plastic and the attachment to reduce the risk of lost tracking during either intrusive or extrusive movements. The Horizontal can also be used to produce a mild force to address labiolingual discrepancies (like The Vertical) — pushing a tooth facially or lingually. Finally, the Horizontal can be utilized to place an indent at the undercut of the crown of a tooth near the gingival margin to enhance the retentiveness of aligners (Figure 2F).
Standardized clinical process
In order to streamline the process of integrating individualized enhancement for a series of aligners, a prescription form is used to note the specific sites where Clear Collection instruments will be applied to each tray (Figure 3). In preparation to address each aligner, the prescription is completed in anticipation of the specific procedures needed for the trays. Notes regarding any mechanics to be employed are added (e.g., Class II elastics, bootstrap elastic, chain for rotation, molar distalization, protraction, intrusion, extrusion, etc.). The prescription accompanies the aligners that are to be dispensed at the patient’s next appointment along with the necessary Clear Collection pliers needed. A copy or scan of the prescription is kept for reference in the patient’s chart. In this manner, clinical coordination and consistency are communicated clearly.
The Clear Collection can assist in the application of adjunctive forces to broaden the variety of malocclusion problems that may benefit from aligner treatments. Enhancing and accentuating chosen biomechanics helps reduce the known limitations of aligners and orthodontists’ occasional frustrations. In this manner, the clinician can more efficiently individualize treatment for each patient by altering the aligner trays in a series by adding appropriate forces to affect desired tooth movements. Specifically, The Hole Punch and The Tear Drop instruments facilitate the addition of elastic forces necessary for the correction of a significant number of malocclusions. Much like bending wires with orthodontic pliers, The Vertical and The Horizontal provide an added dimension for individualizing specific tooth movements in “real time” at the clinic chair.
The instruments in the Clear Collection help the orthodontist to better customize clear aligner treatments, enhance his/her desired biomechanics, and streamline the addition of adjunctive forces during the course of a series of aligners. For information on the use and applications of the Clear Collection, instructional videos are available on YouTube: https://www.youtube.com/watch?v=hrs2VfnImLY.
- Kravitz ND, Kusnoto B, BeGole E, Obrez A, Agran B. How well does Invisalign work? A prospective clinical study evaluating the efficacy of tooth movement with Invisalign. Am J Orthod Dentofacial Orthop. 2009;135(1):27-35.
- Krieger E, Seiferth J, Marinello I, Jung BA, Wriedt S, Jacobs C, Wehrbein H. Invisalign® treatment in the anterior region: were the predicted tooth movements achieved? J Orofac Orthop. 2012;73(5):365-376.
- Chisari JR, McGorray SP, Nair M, Wheeler TT. Variables affecting orthodontic tooth movement with clear aligners. Am J Orthod Dentofacial Orthop. 2014;145(4 suppl):S82-91.
- Tuncay O. Clinical Reports & Techniques. 2005;6(2):1.
- Nicozisis JL. Tripping the plastic fantastic. Orthodontic Products. 2013;Nov:28-34.
- Humber P. Rotating canines using the Invisalign system. Aesthetic Dentistry Today. 2013;7(1):30-34.