Association between mandibular third molar formation and retromolar space.
OBJECTIVE
To assess the association between formation stages of the mandibular third molars and the space distal to the permanent molars (retromolar space).


METHODS
The material included pretreatment lateral cephalographs of 96 orthodontic patients (49 males, 47 females; 8-18 years old). The molar formation stage was assessed through the method of Nolla, which rates the degree of calcification on a scale of 10 stages. The retromolar space was measured from the most concave point of the anterior border of the ramus to the distal surface of the first molar (used because the second molars had not yet erupted in the younger patients). Statistical analyses included t-tests and analyses of variance for group differences and the Pearson product moment to gauge associations among variables.


RESULTS
The formation stage advanced with age, but wide standard deviations were noted. Similarly, the retromolar distance increased with age and was greatest between 10 and 12 years. The correlation between retromolar space and developmental stage was high (r  =  0.85). On average, an increase of 5 mm of retromolar space corresponds to a 1.8 stage in tooth maturation.


CONCLUSIONS
The correlation between third molar mineralization and available retromolar space essentially represents the association between one biologic age (dental formation) and another growth-related event (mandibular skeletal growth). The findings do not necessarily reflect successful emergence or nonimpaction of the molars. Longitudinal data are needed to determine such outcomes.
a  Clinical Associate, Division of Orthodontics and Dentofacial Orthopedics, American University of Beirut Medical Center, Beirut, Lebanon.
Saro S
SS
Ghougassian
Joseph G
JG
Ghafari
D000293:Adolescent; D000367:Age Factors; D002508:Cephalometry / Q000379:methods; D002648:Child; D003724:Dental Arch / Q000033:anatomy & histology* / Q000254:growth & development; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000033:anatomy & histology* / Q000254:growth & development; D008963:Molar / Q000033:anatomy & histology; D008964:Molar, Third / Q000254:growth & development*; D009805:Odontogenesis / Q000502:physiology*; D011862:Radiography, Panoramic; D012737:Sex Factors; D014074:Tooth Calcification / Q000502:physiology; D019228:Tooth Crown / Q000254:growth & development; D014092:Tooth Root / Q000254:growth & development
Dental age; Development; Retromolar space; Root formation; Third molar