Mx & Md SPACE

CALCULATORs

DESCRIPTION

 Am I extracting? 🤔

The most crucial question in every treatment plan. We all know the those good old formulas that help you make the call:

For every 1 mm of incisor retraction/protrusion, we require/create 2 mm of space.

For every 1 mm of maxillary expansion, we create 0.7 mm of space.

Since there are so many factors to consider all at once, I have created the Maxillary and Mandibular Space Calculators to help you keep track of all your thoughts and feel confident that you’ll be able to correct any tooth size arch length discrepancies (TSALDs).

The calculator is divided into THREE sections:

Section I — Space Analysis

In the first section, you simply write down what you see:

  • Crowding

  • Spacing

  • Leeway space

This should be calculated in relation to the line of the arch that reflects your planned incisor position and arch shape. This assessment of crowding / spacing gives us our baseline TSALD.

Section II — Planned Incisor Position (PIP)

In the second section, plan where you want the incisors to finish in terms of A-P position of the incisal edge. I view this step as the KEY step for two important reasons:

  1. Incisor position drives aesthetic outcomes, which are of the utmost importance to our patients

  2. We must respect bony limits and ensure incisor roots remain safely contained within the alveolar housing to avoid periodontal complications

Consider using the N-A line to guide your planned incisor position (Creekmore, 1997):

L1s — on the N-A line

U1s — just ahead of the N-A line

The Class II div 1 patient in this example requires mild procilnation of the lower incisors, and a fair bit of retraction of the upper incisors to satisfy the above criteria.

Section III — Space CreatION

In the third section, you get to have some fun and play around with all the different ways you can create space to account for any TSALDs:

  1. Expansion / Uprighting

  2. Derotation

  3. Distalization

  4. Interproximal Reduction (IPR)

  5. Extraction

Keep playing until your “Total crowding / spacing” hits zero (or moves into the positives) indicating you have enough (or excess) space to carry out your incisor-driven treatment plan.

A few notes:

  • Sometimes, Space Creators 1 through 4 are not enough to resolve the TSALD and you must resort to the 5th option — extractions

    • If this is the case, jump over to the Extraction Calculator page to determine which extraction pattern will be most beneficial based on the current A-P relationship of the buccal segments

  • If you still cannot create enough space (e.g. extractions are contraindicated), you may have to adjust your PIP (e.g. less retraction) to minimize your space requirements

This SECTION Ends by displaying a total score

by combining sections 1-3

If your score = 0

  • You created exactly enough space to carry out your treatment plan

  • You have no residual space (i.e. 0mm)

  • You do NOT need to burn anchorage, and can skip to Section V

If your score is > 0

  • You created excess space

  • You have residual space left over

  • You MUST head to Section IV to burn anchorage (i.e. slip the molars forwards)

evidence-based

The formulas utilized by the calculators are based on my review of the literature and wisdom passed down by my instructors at the University of Toronto.

If you are curious about where the values come from, click the button below to see the main references I based these calculators on.

References

Now that you understand the theory behind the space calculators

Click on the Calculators below and start crunching the numbers!

MANDIBULAR SPACE CALCULATOR

MANDIBULAR SPACE CALCULATOR

MAXILLARY SPACE CALCULATOR

MAXILLARY SPACE CALCULATOR