Root resorption and submergence in retained deciduous second molars

The long term condition of retained deciduous second molars with no permanent successors, was studied. The children were examined once a year. Recordings included intraoral roentgenograms, dental casts and body height measurements. The rate of root resorption (mandibular molars only) and the occurrence of submergence were studied. Four stages of root resorption were defined and judged subjectively. The occurrence of submergence was diagnosed by the downward slope of the marginal bone contour toward the deciduous molar. Body height measurements were used to ascertain peak height velocity (PHV). On average, each resorption stage lasted about 4 years but the rate of root resorption varied considerably. No particular pattern of root resorption was found in relationship to sex, dental decay, submergence or age. The onset of submergence was not observed later than about one year after PHV. No relationship was found between the occurrence of submergence and sex, dental decay or the stage of root resorption. Submergence occurred more frequently in the mandible than in the maxilla.