I would like to make some personal observations on the Point/Counterpoint feature in the April issue (Zachrisson BU, Rosa M, Toreskog S. Congenitally missing maxillary lateral incisors: Canine substitution [Point/Counterpoint]. Am J Orthod Dentofacial Orthop 2011;139:434-4). I extend my compliments to Björn Zachrisson and his group for their invaluable contribution to the orthodontic literature for decades. Their remarkable esthetic results, shown in a 2007 article, were truly outstanding. My focus in this letter, however, is on oral health. After treating hundreds of patients with congenitally missing maxillary lateral incisors, both in my private practice and in the clinics at Harvard/Forsyth, I believe that opening space, not closing it at the agenesis sites, is the preferable option for several compelling reasons. First, the canine in the lateral incisor position is generally not only a poor esthetic option, but also I have found that the alveolus at that site cannot accommodate the labiolingual width of the canine in the long term. Therefore, I have observed that labial dehiscences often occur in time.

Moreover, I have observed that the concave surface of the maxillary first premolar in the canine position is vulnerable to periodontal breakdown when trauma from occlusion inevitably occurs during excursions, in spite of crown recontouring. A unique characteristic of the mesial surface of the maxillary first premolar is its concavity. This depressed area is variable. Most often, it is limited to the mesial portion of the cervical third, but some specimens exhibit an extension that can reach as far as the middle portion of the mesiobuccal line angle areas. This landmark is a relatively consistent way to distinguish the maxillary first premolar from the maxillary second premolar, which generally lacks this feature. Consequently, I have observed that a combination of plaque buildup at this site and the inability to floss this concavity has resulted in periodontal breakdown and subsequent loss of the premolar. Management of this occurrence presents a serious dilemma for the clinician.