Can crown-root ratio predict premolar eruption?

Introduction: The purpose of this study was to establish a method to prospectively predict the eruption of mandibular second premolars with panoramic radiographs. This technique could be used clinically to optimize the timing of comprehensive treatment, detect abnormalities of development and eruption, or effectively estimate eruption timing and determine the need for early intervention because of caries or defects of the deciduous dentition. Methods: Three hundred one white children from an orthodontic practice in Alaska between the ages of 6 and 16 years were examined and monitored with serial panoramic radiographs until all premolars had erupted. Eruption of the mandibular second premolar was predicted at the first examination based on the panoramic radiograph. When the mandibular second premolar erupted, a researcher measured the crown length to crown-plus-root length ratio on the radiograph using the Simpson and Kunos scale, and the prospectively predicted timing of eruption was compared with the actual timing. Results and conclusions: The Simpson and Kunos scale allowed a rapid assessment for predicting the time of eruption of mandibular second premolars. The mean age of eruption of the mandibular second premolar in these children was 12.5 years.