Variations in the sequence of emergence of canines and premolars : relation to dental arch anatomy and impact on clinical decisions and outcome

Abstract

Background: Sequence of emergence of teeth is important for treatment timing and success. Variations in eruption sequence have been reported in the literature, especially between the permanent canine (3) and second premolar (5) in the maxilla, and the permanent canine (3) and first premolar (4) in the mandible. Hypothesis: Variations in the emergence sequence specifically when 5 erupts before 3 in the maxilla and when 4 erupts before 3 in the mandible is related to crowding within the arch. Aim: to determine the relation between space availability (Arch Circumference Discrepancy) within the arch and the sequences of emergence of 3-5 in the maxilla and 3-4 in the mandible. Materials and Methods: This is a retrospective blinded study conducted on the pretreatment records of 235 patients (98 boys, 137 girls; ages: 11.39 and 11.20 years) treated at the Division of Orthodontics and Dentofacial Orthopedics Clinic at the American University of Beirut Medical Center. Patients included in the study had at least one of the following teeth in active process of eruption: maxillary 3 and 5 and-or mandibular 3 and 4. Patients with missing teeth, previous orthodontic treatment and-or craniofacial anomalies were excluded. Evaluation of pretreatment records included: (a) dental cast to record sequence of eruption: Seq1 (3-5) or Seq2 (5-3) in the maxilla and Seq3 (3-4) or Seq4 (4-3) in the mandible; ACD; total, anterior and posterior arch length; arch width at the level of the inter-molar and inter-canine distances; and dental emergence age, (b) panoramic radiograph to assess dental formation, (c) lateral cephalogram to evaluate the sagittal jaw relationships and inclination of maxillary and mandibular incisors, (d) hand wrist radiograph to assess the bone age of the subjects and determine its concordance with chronologic and dental ages. Results: More crowding occurred with Seq2 than Seq1 in the maxilla, but there was not statistically significant difference (SSD). In the mandible, more space was available for Seq3 than Seq4 an