Aligners are thin, clear plastic appliances that fit very closely over the teeth. Designed to slowly move the teeth when worn every day, they are similar to the Essix retainer, which is used to maintain (but not move) the position of teeth following orthodontic treatment.


Wearing Invisalign aligners

Aligners move teeth in tiny, incremental steps. A series of aligners is made to perfectly fit onto the teeth, with each aligner in the series being slightly different from the next. All aligners are worn virtually full time for two weeks before moving on to the next set in the series.

• Aligners must be worn for at least 22 hours every day, and they should only be removed for eating and cleaning. Wearing them less than 22 hours a day will only lead to a poor result.
• They do not really affect your speech because they fit so closely to your teeth.
• They are clear and virtually invisible but can be noticed if someone enters your personal space. Few work colleagues will notice that you are wearing aligners.
• Normally only three to four aligners are made at a time. If more movement is required another impression is taken to construct more aligners.

Aligners are made of clear food grade plastic with varying degrees of thickness and flexibility. A sheet of this plastic is heated over a model of your teeth, then hot vacuum molded onto the model. The plastic is trimmed to cover the area required and the edges are smoothed. Invisalign aligners are trimmed back to the gum edge but aligners from other manufacturers may vary.

Invisalign aligners are constructed with the aid of a computer and use very precise three dimensional models of your teeth. The basis of these 3D models is a virtual model of your teeth stored in the computer, while the 3D models themselves are produced via an interaction of lasers and polymer gel. A series of slightly different models are made (progressing from your start position to the finished position) and an aligner is constructed using each model.

Aligners have been used for about 70 years but their popularity truly soared after the introduction of Invisalign in 1999. Several competing aligner systems are now available, but Invisalign is the only one that uses CAD/CAM technology. All other alignment systems are laboratory-based.

• Invisalign is the Rolls-Royce of the aligner world. Its patented technology for using computerised simulations to produce aligners gives the Invisalign system several significant advantages, including reliable fit and the ability to produce a longer series of aligners. It also has certain disadvantages, including being inappropriate for minor treatments. Its cost is higher, and some cases may require a second phase of treatment.
• Kesling is the generic name for all laboratory-constructed aligners, named after Dr. Kesling, an avid proponent of aligners in the UK. All aligners are variations on his concept. Most good orthodontic laboratories can provide Kesling aligners, which are suitable for a series of three to four aligners at most. Additional Kesling aligners require a new impression to be taken.
• Clear Step is a laboratory-based aligner system which uses a patented technique to minimize construction and maximize accuracy. Clear Step requires repeated new impressions to be taken during the treatment phase. The major competitor of Invisalign in the UK, Clear Step requires careful treatment planning.
• Simpli 5 is a laboratory-based aligner system which, although based in the USA, aims for a rapid aligner turnaround time of two to three weeks.
• Orthoclear is a laboratory-based aligner system based in Germany.
• 6 month Smiles is a relatively new laboratory-based system from the USA which is not currently used by many practitioners in the UK.

Aligner with false tooth to disguise space prior to an implant

In 1945, Dr. Kesling pioneered the use of tooth positioning appliances (early aligners) as part of the final stage of some types of orthodontic work. Dr. Kesling's positioners were able to move the teeth in minor ways but they could also be used retain tooth alignment after fixed appliances were removed. Dr. Kesling correctly predicted that specific major tooth movements could be achieved through a series of progressive aligners – the premise underlying several alignment systems used today.

“Invisible retainers” were introduced in 1971, and progressive alignment using clear aligners came into use a bit later. The technique was based on Dr. Kesling's proposal but was quite time-consuming as a new set of impressions was required at almost every visit.

The introduction of Invisalign in 1999 was a breakthrough, fulfilling Dr. Kesling's proposal that aligner systems could be used for complete and more complex treatments.

Invisalign eliminates the need to create a new model for each new aligner. Using computer-aided design and computer-aided manufacturing (CAD-CAM) technology as well as laboratory techniques, Invisalign permits us to create a series of aligners that can move the teeth in small increments of about 0.25 to 0.3 mm.