Spacing

What causes residual spaces in aligner cases?

One of the most frequent reasons for leftover or residual spaces is a tooth size discrepancy, specifically a Bolton tooth size discrepancy. In orthodontics, this refers to an incongruity between the sizes of the upper and lower teeth.

What is a Bolton tooth size discrepancy?

A Bolton tooth size discrepancy occurs when the mesiodistal widths of the upper teeth and the lower teeth do not match ideally. When these sizes are not congruent, it results in either spaces in one arch or crowding in the other.

How do we determine a Bolton tooth size discrepancy?

We measure the mesiodistal widths (the widths of the teeth from the front to the back) of all the upper teeth to get a total. We do the same for the lower teeth. If these totals are not in an ideal ratio, it leads to spacing or crowding issues.

How does this discrepancy manifest in a case?

For example, if there is too much tooth material in the lower arch compared to the upper arch, you may have a good class I occlusion with a normal overbite and overjet, but there will be residual spaces in the upper arch.

How can we solve these discrepancies?

There are two main methods to address these issues:

1. Interproximal Reduction (IPR):
   • Application: We apply IPR to the lower dentition to reduce the tooth material and balance the ratio.
   • Example: Using IPR to eliminate the spaces can results in a proper class I occlusion with normal overbite and overjet.
2. Restorations:
   • Bonding/Veneers/Crowns: The doctor can choose to add bonding, veneers, or crowns to the upper teeth to close the spaces.
   • Example: If spaces are distal to the canines, restorations can be placed there, or the canines can be moved back in contact with the first premolars, and restorations can be added to the laterals if they are small.

What if there is too much tooth material in the upper arch?

When there is excess tooth material in the upper arch compared to the lower arch, it results in extra overjet. In such cases:

• Option 1: Leave the extra overjet if it is not problematic for the patient.
• Option 2: Apply IPR to the upper teeth (usually between teeth 6 and 11) to reduce the overjet to a more normal range.

By understanding these common issues and their solutions, our doctors can effectively manage and plan treatments for their patients, ensuring optimal results with minimal residual spaces.