The March 2011 cover article (Bonetti GA, Zanarini M, Parenti SI, Marini I, Gatto MR. Preventive treatment of ectopically erupting maxillary permanent canines by extraction of deciduous canines and first molars: a randomized clinical trial. Am J Orthod Dentofacial Orthop 2011;139:316-23) should have been welcomed news to all clinicians who want to simplify orthodontic treatment of palatally displaced canines. It proposed that extracting both the deciduous canine and its contiguous deciduous first molar will almost guarantee our chances of influencing improved self-eruption of “retained maxillary permanent canines positioned palatally or centrally in the alveolar crest.”
I eagerly dug into this promising study, which featured the “gold standard” randomized clinical trial methodology. Some disappointment soon followed. The methods of this study may have been first-rate, but the sample had some problems, I discovered. The original at-risk sample of 40 subjects was diagnosed with 70 unerupted, displaced canines. That implies a bilateral palatally displaced canine (PDC) occurrence rate of 75%, 2 to 3 times the frequency of bilateralism reported for PDC subjects in previous studies. In my opinion, this indicates a problematic palatal-canine sample. Perhaps many canines diagnosed as PDC were not actually PDC, but simply in age-appropriate unerupted positions. The sample’s age range of 8 to 13 years at initial observation may explain this aberration. McSherry and Richardson’s work informs us that, in children younger than 10 years, the maxillary canines normally appear palatal radiographically. Thus, many of the younger subjects in the Bonetti study sample may simply have had temporarily angled normally erupting canines, not retained or permanently displaced canines. Knowing this, we may reason that most of the pseudo-PDCs in the 2 experimental samples would have erupted satisfactorily with no extractions of deciduous teeth.
So, what should clinicians take from this small-sampled study that tells us to extract the deciduous first molar in addition to the customary extraction of the overlying deciduous canine in order to more reliably intercept “retained maxillary permanent canines”? Should randomized sampling methods and multiple statistical manipulations of data give us confidence in results despite flaws in sample quality and interpretation? When a study sample is prone to yield false positives, regardless of an admirable study design, I believe there is reason to be cautious with conclusions. All things considered, I submit that extraction of the maxillary deciduous canine alone is still the most prudent conservative interceptive standard of care we may recommend when we detect clear-cut palatal displacement of an unerupted maxillary canine in a child aged 10 years or older.