Genetic causes vs guidance theory for palatal displacement of canines

Orthodontics, the premiere dental speciality, is plagued with controversies that cannot be settled totally by scientific evidence. Even so, it is a rarity in contemporary orthodontic literature to witness head-on clashes like the exchange between Drs Peck and Becker in the “Readers’ Forum” in February 2016.

This is not the first time these stalwarts have presented diagonally opposing views. In response to the 1994 article by Peck et al in The Angle Orthodontist , “The palatally displaced canine as a dental anomaly of genetic origin,” Becker argued the alternative theory of guidance; his view was published side by side with the response of Peck et al in The Angle Orthodontist in 1995.

Except for some of the language used, it was a treat to read the recent exchange. The letter and authors’ response made me return to the once casually read review article by Becker and Chaushu that was the subject of the recent exchange. As an orthodontist and a lawyer, I like to read arguments pertaining to controversial topics in orthodontics (I love “Point/Counterpoint” in the AJO-DO ). But, even after 20 years, the keystone controversy of genetics vs guidance is not resolved. The debate is truly unworthy at this juncture because the “all-encompassing” etiology suggested by Dr Becker includes both. The causal link between peg-shaped lateral incisors and palatally displaced canines is not totally out of place. From the fragments of the upper jaw of an Etruscan adolescent of the sixth century bc , Baccetti et al reported the presence of a palatally erupted canine along with a peg-shaped lateral incisor and aplasia of the premolars in which genetic as well as mechanical guidance has been acknowledged. Peck, in his commentary to this article, ruled out the possibility of mechanical guidance and upheld the role of genetics. The real issue can be tapered to whether a multifactorial view with guidance predominates, as expressed by Becker, or whether the “black-box” concept of heredity is the cause of palatally displaced canines. The explanation of Becker and Chaushu, that “determination of the eruption path of the palatal canine is for the most part not under genetic control,” may be true, but the genome of the canine will decide whether to take that path or not, substantiating Dr Peck. In a recent article in the AJO-DO , Carlson mentioned that we are in the genomic era of “precision orthodontics”; let us hope to identify the key gene involved in palatally displaced canines; until then, both win.

I truly agree with the opening paragraph of the response letter of Dr Becker, that the case can be argued in a more professional way. Here I am reminded of the famous quote by Dr Martin Dewey, first editor of the AJO-DO , in the context of the great extraction debate, “Science knows no friends.”

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Apr 4, 2017 | Posted by in Orthodontics | Comments Off on Genetic causes vs guidance theory for palatal displacement of canines
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