Clinical Success in Invisalign Orthodontic Treatment

Richard Bouchez

• Publisher: Quintessence International Editeur
• Year: 2019
• ISBN:
  9782912550880
• Edition: 1
• Topic: Medicina
• Subtopic: Ortodonzia

In the established tradition of the Clinical Success series, this succinct and easy-to-read book provides practitioners with a solid foundation for daily clinical use of the Invisalign system. The author introduces the reader to essentials of Invisalign treatment, from the basic biomechanics of thermoformed plastic aligners to the the Clin-Check 3D simulation treatment planning software, which allows the clinician to program in advance the velocity and direction of tooth movements; amount and frequency of force; anchorage; and available space necessary for the planned movements. Clinical results of various treatment types are shown using Invisalign system alone and in conjunction with other orthodontic treatments. This book is ideal for any orthodontist who wants to use the Invisalign system to achieve an optimal treatment outcome.

The Invisalign Concept

Fig 1-1 (a to c) Aligners are easy to insert, comfortable, and minimally visible.

What Is Invisalign?

• Invisalign is a minimally visible method for moving teeth without band, wire, or bracket.

• Invisalign therapy consists of a series of clear aligners that are worn to gradually move teeth (Fig 1-1).

• An Invisalign aligner is a custom-made, removable, comfortable dental retainer made from thermoformed medical polycarbonate, which is inert and compatible with human saliva. (See following section for details on thermoforming.)

• Each aligner is worn approximately 22 hours a day over a 2-week period for a total of over 300 hours. This leaves 2 hours a day for eating and toothbrushing.

• Aligners are replaced every other week on average to allow for gentle tooth movement over time according to the clinician’s diagnosis and treatment plan.

• Treatment duration, which can range from 3 to 30 months, and cost depend on the extent of tooth malpositioning and malocclusion.

The Science of Invisalign Aligners: Thermoforming

Thermoforming is the art of shaping thermoplastic materials with heat. Chemically, plastics consist of polymers that are made up of numerous monomers, which are organic molecules with nuclei that contain one carbon atom. Examples of natural polymers include proteins, rubber, collagen, and cellulose. The behavior of plastics mostly depends on the type of structure developed by polymerization of constituent monomers. To optimize their behavior, additives can be used to modify physical and chemical properties, and reinforcements can be added to modify mechanical properties.

In orthodontics, plastic materials in the form of soft, resilient round or square sheets (Fig 1-2) possessing excellent modeling properties are often used. These materials are inert, unaltered by saliva, and resistant to daily cleaning detergents. In addition, they are transparent, nontoxic, odorless, and tasteless.

Scheu et al proposed the first thermoforming machine to synthesize orthodontic appliances in 1966. Currently, two types of thermoforming machines, the Ministar and Biostar (Scheu Dental) (Fig 1-3), are available. Based on the principles of Scheu et al, Align Technology developed a large-scale, custom-made thermoforming system, which continues to undergo development and improvement (Fig 1-4).

Fig 1-2 Thermoformable plastic sheets used clinically.

Fig 1-3 Biostar series IV.

Fig 1-4a Thermoforming.

Fig 1-4b Automated sculptor of aligners.

Development of Align Technology

Design for the thermoforming system began in April 1997 when two MBA students from Stanford University, Zia Chishti and Kelsey Wirth, with the aid of a computer specialist, founded Align Technology in a garage in Palo Alto, California.

Chishti, who had suffered a relapse of mandibular incisor crowding after undergoing fixed orthodontic treatment, was required to wear a retainer to realign his mandibular anterior teeth. Disappointed by the relative slowness and limited progress of the relapse correction, Chishti conceived a revolutionary treatment concept: moving teeth with multiple appliances, whereby each tooth movement would be progressively conceptualized in three dimensions and virtually simulated by computer-assisted design software.

Appliances would be mechanically fabricated under computer control through a stereolithographic process to create resin models for each stage of desired tooth movement. These models would then be combined with thermoformed polycarbonate sheets, which would allow for mass-produced, custom-made aligners for orthodontic treatment.

This new concept for orthodontic treatment combined orthodontic principles of tooth movement, 21st century three-dimensional (3D) computer-aided design/computer-assisted manufacture (CAD/CAM) technology, and computer-assisted, mass-prototyping industrial processes, ultimately leading to the development of the Align Technology company and the current Invisalign treatment concept and techniques.

This new system gained clearance from the Food and Drug Administration in 1998. It was presented at the American Association of Orthodontists conference in 1999 and arrived in Europe in 2001. By broadening the range of applications, Invisalign has introduced a new method of orthodontic therapy.

Fig 1-5 When a tooth is missing (a), a pontic can be incorporated into the aligner (b).

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