Topics covered

• Types of malocclusion: crowding, spacing, midline misalignment, overjet, overbite, open bite
• Tooth movements:  tipping, torquing, translation, rotation, intrusion, extrusion
• Treatment methods: distalization, mesialization, lingualization, expansion

These are approximate guidelines only. Teeth don’t always move in predictable ways. A number of factors (including anatomy and patient compliance) can significantly affect the duration and effectiveness of treatment. Even cases within our recommended parameters cannot always be treated successfully. There are no guarantees in clear aligner therapy. Some cases may require more than the allotted number of aligners.

When you evaluate the difficulty of a case, always consider the whole mouth and all treatment goals.

Download a printable guide here.

Types of malocclusion

Tooth movements

Treatment methods

Most cases will require some kind of adjustment to the overall arch form. These arch movements usually fall into four main categories:

• Distalization
• Mesialization
• Lingualization
• Expansion

The overall movement of an arch is determined by the types of movements made by the individual teeth in that arch.

For instance, in a case where the upper incisors are crowded, you might tip the upper incisors by 1 mm. This would expand each of the upper quadrants by approximately 1 mm, thereby adding a total of about 2 mm of space to the upper arch. This is just a rough calculation.

The overall amount of arch movement expected in each quadrant can give you a rough indication of how difficult a case may be.

The above illustration shows some general guidelines.

Of course, every patient is different - so, as always, your results may vary.