Malposition of Unerupted Mandibular Second Premolar in Children with Palatally Displaced Canines

Abstract

Objective: To test the hypotheses that (1) the distal angulation of unerupted mandibular premolar (MnP2) is significantly greater in children with palatally displaced canines (PDC) than in those in a control sample; and (2) delayed tooth formation is significantly more frequent in children with both malposed MnP2 and PDC than in children with PDC only. Materials and Methods: We examined retrospectively panoramic radiographs from 43 patients with PDC who had no previous orthodontics. A control sample consisted of age-and sex-matched patients. The distal angle formed between the long axis of MnP2 and the tangent to the inferior border was measured. Dental age was evaluated using the Koch classification. Results: A significant difference was observed between the mean inclination of the right side MnP2 in the PDC group (75.4 degrees) and that of the control group (85.8 degrees). This difference was highly statistically significant (P Ͻ .0001). The same evaluation was carried out for the left side, with similar results. The average dental age was found to be delayed in patients who showed both abnormalities (malposed MnP2 and PDC) compared with patients who showed the PDC anomaly only. Conclusion: Both hypotheses are retained. Statistically, PDC and MnP2 malposition are significantly associated suggesting a common genetic etiology, despite taking place on opposite jaws. While the presence of PDC or MnP2 anomaly has been associated with a delay in tooth formation, we find the presence of both anomalies to show a more profound delay. Our findings suggest a delay in tooth formation as a possible common genetic mechanism for these 2 malposition anomalies. (Angle Orthod. 2009;79:796-799.)

Dental anomaly pattern (DAP): Agenesis of mandibular second premolar, distal angulation of its antimere and delayed tooth formation

“…PDC and MnP2 malposition have also been proven to be significantly related, suggesting a common genetic etiology, despite taking place on opposite jaws. 15,16 Agenesis of MnP2 and distally displaced premolars have been previously associated in other studies 4,20 ( Figure 3). The study that inspired us, by Shalish et al, 20 showed an almost 10u mean distal angle increase in the agenesic sample compared with an age-and sex-matched control group.…”

“…S. Peck,17 ,18 S. Peck and colleagues, 7,8,11,19 Baccetti,10,12 Baccetti and colleagues, 16 Garib and colleagues, 4 Shalish and colleagues, 5,15,20 and L. Peck and colleagues 13 are prominent among those who have contributed recently to an increased awareness of fundamental relationships among dental abnormalities.…”

“…3 Abnormal conditions such as tooth agenesis, microform teeth, delayed tooth development, palatally displaced canines, infraocclusion of deciduous molars, and MnP2 distal angulation have been found to occur together much more frequently than would be expected by chance alone. [4][5][6][7][8][9][10][11][12][13][14][15][16] Combinations of these occurrences were named dental anomaly patterns (DAPs) by Peck, 17 and they are found in nearly 25% of orthodontic patients.…”

Increased Occurrence of Dental Anomalies Associated with Infraocclusion of Deciduous Molars

“…The choice of this threshold was based on results of previous studies introducing this positional anomaly. [27][28][29][30][31] The standardized method for measuring MnP2-DA described by Shalish et al 27 was employed.…”

Mesiodistal inclination of the unerupted second premolar in the mandible of Japanese orthodontic patients with incisor agenesis

“…Shalish et al 2,17,18 noted that among populations of European ethnicities, significant distal inclination of the unerupted MnP2 is found not only in cases of unilateral MnP2 agenesis, but also among individuals having cleft lip/palate and palatally displaced canines.…”