Esthetic Orthodontic Treatment Using the Invisalign Appliance for Moderate to Complex Malocclusions

Abstract

In this report, three patients were treated with a new treatment protocol for Invisalign to demonstrate that a variety of complex malocclusions can be successfully treated using this protocol, including correction of moderate crowding, correction of moderate Class II division 1, and deep overbite. Previous studies of Invisalign showed significant limitations for more complex orthodontic treatment, although a few recent case reports have shown successfully completed moderate to difficult orthodontic malocclusions. One reason for the discrepancy is that the earlier studies were done during the first four years of the appliance development (now ten years of clinical use), when significant problems existed with accomplishing bodily movement, torquing of roots, extrusions, and rotations of premolars and canines. The new protocol included new methods for anterior/posterior corrections, showing on the computer the effect of elastics for Class II treatment simulated as a one-stage anterior/posterior movement at the end of treatment. Staging for interproximal reduction (IPR) is now automatically staged when there is better access to interproximal contacts to avoid IPR where significant overlap between teeth is present to avoid performing IPR on surfaces that may be damaged by instruments such as burs, strips, and disks when cut on a sharp angle. Staging for tooth movements is now also done to enable combination movements to occur simultaneously for each tooth with the tooth that needs to move the most (the lead tooth) determining the minimum number of stages required. All other teeth move at a slower rate than the lead tooth throughout the duration of treatment. Attachments are now placed in the middle of the crown automatically for rotation and automatically sized in proportion to the clinical crown. Use of 1 mm thick (buccal-lingual dimension) horizontal beveled rectangular attachments is standard on premolars for retention of aligners during intrusive movements, such as leveling the lower curve of Spee in deep overbite for extrusions and for control of the tooth long axis during torquing movements. Staging of tooth movements now track linear and rotational velocities of teeth separately with the number of treatment stages determined by the lead tooth based on its rotational or linear maximum velocities at no more than two degrees of rotation per stage. Simultaneous movements are done for all teeth providing visible space (approximately 0.05 mm) between teeth during movements past other teeth using expansion instead of IPR as a primary way to increase space available for correction of crowding.

Efficiency of Upper Arch Expansion with the Invisalign System

“…It has been reported that the expansion extent with Invisalign should be 2-4 mm. 17 Ali et al 7 indicated that the range of dental expansion should be limited to 2-3 mm in each quadrant to reduce the risk of gingival recession. In the current study, the prescribed amount of expansion for each participant was customized based on measurements of the dentition and CBCT to be within a safe range.…”

Computer aided modelling to simulate the biomechanical behaviour of customised orthodontic removable appliances

“…The system of forces and moments to correct malocclusions is generated by the difference between the appliance shape and the dentition geometries. A single template is able to perform only a small part (from 0.15 to 0.25 mm for translations and no more than 2 degrees for rotations) [1,3] of the complete tooth movement. Therefore, a full treatment consists of a set of templates with varying shapes from the initial anatomical geometry to the target tooth positions.…”

“…Even if RTA-based orthodontic treatments are becoming an effective solution for moderate to complex malocclusions [3], most of the technical literature is focused on case reports and system descriptions. There have been few evidence-based attempts to describe the RTA behaviour in delivering forces able to produce specific tooth movements.…”

The Use of Invisalign® System in the Management of the Orthodontic Treatment before and after Class III Surgical Approach

“…One of the most relevant problems, particularly with regard to adult patients, is represented by the need to undergo orthodontic therapy for several months. The aesthetic problem, associated to the worsening of oral hygiene conditions, may discourage many patients even before the beginning [ 2 ]. Invisalign system (Align Technology, Inc., San Josè, California, USA) could represent a suitable solution to solve such problematic [ 3 – 5 ].…”