PREVALENCE OF TOOTH AGENESIS AND PEG-SHAPED MAXILLARY LATERAL INCISORASSOCIATED WITH PALATALLY DISPLACED CANINE (PDC) ANOMALY

Fifty-eight nonsyndromic North American white orthodontic patients wit h palatal displacement of one or both maxillary canine teeth were stud ied for associated tooth agenesis and peg-shaped maxillary lateral inc isors, Agenesis of permanent teeth was identified by x-ray film analys is, Conical crown-size reduction (peg-shape anomaly) of the maxillary lateral incisor (12) was determined by direct observation. Increases i n absence of third molars and second premolars associated with the pal atally displaced canine (PDC) anomaly were statistically very highly s ignificant compared with normative data for tooth-agenesis prevalence, In contrast, the prevalence of 12 agenesis in the PDC sample showed n o difference statistically compared with reference values, Reasons for this posterior site-specific suppression of tooth formation are not c lear, The 12 peg-shape anomaly exceeded a 10-fold elevation in express ion in the PDC sample, a very highly significant increase from normal prevalence, The findings are consistent with a hypothesis that the ano malies of tooth agenesis, tooth-size reduction, and PDC are biologic c ovariables in a complex of genetically related dental disturbances.