Friday, 24 September 2010

Distally displaced premolars: A dental anomaly associated with palatally displaced canines, AmJO-DO Sept 2010

Dr Tiziano Baccetti, of Florence Italy, is one of the not so many, clinicians and researchers, that thrive to finding useful clinical tools for diagnosis. One of them is the widelly used cervical vertebrae maturation stage. The CVS as it is called, is a method of assesing where considering the growth spur, our orthodontic patients are, through the vertebrae that are visible on the lateral cephalogram, that we already have among our initial registrations.

Dr Baccetti comes with another suggestion, on the AmJO-DO of Sept 2010. The hypothesis of been able to early diagnose palatally displaced maxillary canines, from assessing the distal displacement of the second mandibular premolars. This is the link to the original article's abstract on the American Journal.


  • 2811 subjects of a mean age 9 years and 7 months plus minus 1 year.
  • Control Group: 500 subjects
  • Experimental Groups: 1 subgroup (experimental group 1) of at least 1 distally displaced second lower premolar (DDP) tooth germ, and 2nd subgroup of DDP and palatally displaced canine (PPC)
Comparison was done between each experimental group and the control group. Other factors noted was aplasia of wisdom teeth, aplasia or peg shaped upper laterals, premolars aplasia, contra-lateral mandibular premolar aplasia.

The distally displaced premolar on the lower was measured by those two angles as shown on the graph.

The second premolar of the lower has it's tooth germ developing normally, lying between the roots of the milk second molar. Normal eruption pattern will absorb both of the roots and exfoliate the milk molar while erupting. Deviated distal inclination will resorb the distal root or just part of it, retaining and in some cases stopping the eruption of the permanent tooth.

However the second premolar's inclination can be see radiographically beforetime, compared with the recognition-diagnosis of a palatally impacted canine.

That is the essence of the suggested method and of Dr Baccetti's study.

  • PDC prevalence on the DDP was statistically significant, the study suggests the use of panorama x-rays to asses DDP and early diagnose PDCs
  • Also among the sample, the DDP had a 22% of aplasia of the contralateral premolar on the mandible, although on the control group the percentage was 4%
  • Lastly on the DDP and PDC groups 21% was the prevalence of peg shaped maxillary laterals, however on the control group the percentage was only 6.4%
This study offers a large group of individuals and should be taken as such. The findings could be of use on the every day clinical life of the orthodontist, as to giving a hint to look or anticipate, palatally displaced canines, at patients with a distal inclination of the tooth germ of the second lower premolar.

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