title: Multiple lingual cusps trait on mandibular premolars and hypoconulid reduction trait on mandibular first molar in living Jordanian population. Intra- and inter-trait interactions.
abstract: The objective was to determine the expression and fluctuating asymmetry of two dental morphological traits in the living Jordanians: The lingual cusp number on the lower premolars (LP1 and LP2) and the hypoconulid (distal cusp) reduction on the lower first molar (LM1). In addition, both intra- trait and inter- trait interactions were analyzed. Three hundred school children (15.5 +/- 0.4 years) were involved. Impressions for the mandibular dental arches were taken, and dental casts were reproduced. The above-mentioned traits were observed. Paired sample t test and nonparametric correlation analysis were used for data analysis. Three-cusped LP1 was found in 11.40 % of the examined students, while the two-cusped LP1 was found in 88.60%. In comparison, the Three-cusped LP2 was found in 61.40% while the two-cusped LP2 was found in 38.60% of the observed subjects. The frequencies of the 4-cusped and 5-cusped LM1 were found to be 8.65% and 91.35%, respectively. Nonparametric correlation analysis revealed positive and statistically significant association between the expression of two lingual cusps on LP1 and on LP2 in both genders (p < 0.01), while there was no significant correlation between expression of two lingual cusps on either LP1 or LP2 and the hypoconulid loss on LM1 in both genders (p > 0.05). Bilateralism was highly significant in the tested traits in both genders (p < 0.001). This finding might be a sign of relatively low environmental stresses experienced by the living Jordanians and/or great ability of its individuals to buffer the adverse effects of such stresses on dental development. This study is a useful addition to the existing literature in that it examines a previously poorly characterized population and assists in placing the contemporary Jordanian population within the current framework of human population groups globally.
authors.affiliation: University of Jordan, Faculty of Dentistry, Department of Conservative Dentistry and Fixed Prosthodontics, Amman, Jordan. khraisat@lycos.com
authors.forename: Ameen
authors.initials: A
authors.lastname: Khraisat
authors.forename: Firas
authors.initials: F
authors.lastname: Alsoleihat
authors.forename: Karthikeyan
authors.initials: K
authors.lastname: Subramani
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Al-Rabab'ah
authors.forename: Mahmoud K
authors.initials: MK
authors.lastname: Al-Omiri
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Abu-Tahun
mesh_terms: D000293:Adolescent; D001641:Bicuspid / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D015994:Incidence; D007597:Jordan / Q000453:epidemiology; D008297:Male; D008334:Mandible / Q000033:anatomy & histology*; D015233:Models, Statistical; D009811:Odontometry / Q000706:statistics & numerical data*; D015995:Prevalence; D012727:Sex Characteristics; D019228:Tooth Crown / Q000033:anatomy & histology*