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The problems of missing and ectopic second bicuspids

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Severely ectopic LR5 had to be removed. © 2018

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3 Facts for your consideration:
  • The “5’s”, or second bicuspids are statistically the third most-commonly congenitally anomalous teeth, misshapen, ectopic eruptive positions, and missing.  (The first two are wisdom teeth and upper laterals.)
  • The predecessor primary/baby tooth,  the “e” tooth, is typically 2-3 or more mm wider mesio-distally than the 5’s.  
This provides extra space in the arch between the 6 year molar which erupts distal to the “e”, and the lateral incisor, so that the 3’s, 4’s, and 5’s (permanent canine and first and second bicuspids) have space for eruption.
5 Things that can throw the system off:
  1. Missing permanent 5’s.
  2. One or more bicuspids in poor developmental/eruptive position
  3. Eruption sequence out of order, so space is lost early, OR held too long by a primary tooth, most often the “e”.
  4. Ectopic position after eruption, often rotations, sometimes as much as 90∘
  5. There is no space for lower 12-year molar eruption, and 5’s are crowded out.
  6. Profile is protrusive, and if all teeth remain in the arch, the protrusion is unesthetic.
For 5-eruptions to work well, the following 3 are necessary:
  1. All permanent teeth are present.
  2. All permanent teeth must be in relatively good eruptive position.
  3. The sequence of primary tooth exfoliation is ideally... 
    Upper: the “d” exfoliates and the 4 erupts the “e” exfoliates and the 5 erupts right away before the 6 year molar has a chance to mesialize the “c” exfoliates and the 3 erupts last
    Lower: the “c” exfoliates and the 3 erupts the “d” and “e” exfoliate about the same time and the 4 and 5 erupt without the 6-year molar having time to mesialize.

5 Things you do to reduce the risk of FIVEs not jiving. (Which will help provide better chance of the necessary factors above.)
  1. Clear the path (extract primary teeth that are in the path)... as early as the panoramic demonstrates an ectopic trajectory is obvious... ascertain LLA (lower lingual arch, Nance or upper lingual arch)... is in place to avoid any mesialization of the 6 year molars  (save the precious “e” space)
  2. Use a UAW (Utility Arch Wire) to create space
  3. If severely ectopic trajectory, removal may be needed at some point
  4. Utilize various orthodontic techniques to derotate a rotated bicuspid as soon as it erupts, before the interosseous and interdental fibers develop
  5. Include in a comprehensive orthodontic treatment plan, the removal of a bicuspid that will facilitate successful eruption and successful occlusion of other teeth, including the 12 year molars, or removal of bicuspids when it will facilitate the most beautiful profile.
You can reduce treatment time, reduce frustration for you and for your patient, and improve your finished results by utilizing the above treatments in your orthodontics.
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No space for 7’s and protrusive profile: plan to extract L5’s. © 2018 Dr Chris Baker.

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UAW’s to create arch length for 3,4,5’s. © 2018 Dr Chris Baker. All rights reserved.

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Unerupted L5; parents don’t want to remove now; hope for eruption. Completed ortho, removed braces… 5 is holding bone for implant. © 2018 Dr Chris Baker

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Dr Chris Baker

America's most-trusted teacher of orthodontic continuing education, Dr. Chris Baker has practiced and taught for more than 30 years, and is a current or former faculty member of three U.S. dental schools.  She is a pediatric dentist, author, blogger, dental practice consultant, and mentor.  Dr. Chris is also Past President and Senior Instructor of the American Orthodontic Society.  She is based in Texas, USA, but lectures around the world.

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