How much expansion can we get with aligners? Is there a limit?
Answer: Expansion is a key topic in orthodontics, and understanding the limits and possibilities is essential. Here's a detailed explanation:
- Historical Context:
- Tooth Extractions: Historically, many orthodontic cases involved tooth extractions to create space. This approach has shifted over time.
- Pendulum Swing: Initially, the trend moved from frequent extractions to minimal or no extractions, focusing more on expanding arches to avoid changing facial profiles.
- Current Approach to Expansion:
- Balanced View: We aim to limit extractions while achieving necessary expansion to maintain the natural facial profile.
- Measuring Expansion:
- Upper Arch Width: The average width from first molar to first molar in the maxillary arch ranges from 36 to 40 millimeters. This measurement is taken at the gingival margin of the mesial lingual cusp.
- Diagnostic Tool: A Boley Gauge or a simple cotton roll, (approximately 37 millimeters in length), can be used chair-side to assess the distance between teeth numbers 3 and 14, measured at the gumline, if expansion is necessary. If the cotton roll fits snugly, expansion may be needed.
- Ideal Expansion Range:
- Target Width: We aim for an upper arch width between 36 and 40 millimeters. Specifically, a 38-millimeter mark is a common target, with flexibility to go up to 40 millimeters if necessary to resolve crowding. Exceeding 40 millimeters is generally avoided to stay within safe expansion limits.
- Lower Arch Considerations:
- Uprighting Molars: For the lower arch, expansion typically involves uprighting lingually inclined molars rather than true expansion, which increases arch length and helps resolve crowding.
- Visual Aids: Using grid lines in case reviews can visually demonstrate the space gained through molar uprighting.
- Practical Application with Candid Pro:
- Starting with Lower Arch: In Candid Pro treatments, the process often begins with the lower arch to determine the achievable expansion in the upper arch.
- Achieving Goals: This method helps achieve the average 36 to 40 millimeter upper arch width, ensuring effective and predictable treatment outcomes.
By understanding these parameters and using practical diagnostic tools, we can effectively plan and execute expansion in orthodontic treatments, minimizing the need for extractions and preserving facial profiles.