ABSTRACT
objective To observe the distribution of vitamin D receptor(VDR)gene polymorphisms in children of Han nationality and investigate the relationship between VDR gene polymorphisms and the susceptibility to children's dental fluorosis of Han nationality.Methods From October of 2008 to March of 2009,a case-control study was conducted among children between 8 and 12 years old with(n=101)and without(n=102)dental fluorosis using Dean method in Guandian countyside of Fengtai county in Anhui province.DNA was extracted from blood samples ofthese children.The Apa I,Bsm I,Fok I and raq I polymorphisms in the VDR gene were genotyped using polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP).The distribution of the genotypes in patients and the control group were analyzed. Results Different genotypes of the VDR gene existed in children of Han nationality with the highest distribution frequency of Aa, bb, Ff, TT, which respectively was 51.7% ( 105/203 ), 89.7% (182/203), 52.7% (107/203), 93.1% (189/203), followed by genotype distribution frequency of aa, Bb, FF, Tt, being 39.9% (81/203),7.9% (16/203),31.5% (64/203) ,6.9% (14/203), respectively. AA,BB, ff, tt distribution frequency was the lowest as follows, 8.4% ( 17/203 ), 2.4% (5/203), 15.8% (32/203),0 (0/203). The frequency distribution of VDR Apa I genotype was AA 7.9% (8/101), Aa 55.4% (56/101), aa 36.7%(37/101) in children with fluorosis, and AA 8.8% (9/102), Aa 48.0% (49/102), aa 43.3% (44/102) in children without fluorosis, respectively. There were no significant differences in the two groups(χ2= 1.13, P > 0.05).The frequency distribution of VDR Bsm I genotype was BB 3.0%(3/101), Bb 5.9%(6/101 ), bb 91.1% (92/101) in children with fluorosis, and BB 2.0% (2/102), Bb 9.8% (10/102), bb 88.2% (90/102) in children without fluorosis, respectively. There were no significant differences in the two groups(χ2 = 0.55, P > 0.05). The frequency distribution of VDR Fok I genotype was FF 28.7%(29/101), Ff 56.4% (57/101), ff 14.9%(15/101) in children with fluorosis, and FF 34.3% (35/102), Ff 49.0% (50/102), ff 16.7% (17/102) in children without fluorosis,respectively. There were no significant differences in the two groups(χ2 = 1.14, P > 0.05). The frequency distribution of VDR Taq I genotype was TT 93.1%(94/101), Tt 6.9%(7/101) in children with fluorosis, and TT 93.1% (95/102), Tt 6.9%(7/102) in children without fluorosis, respectively. The tt genotype was not found. There were no significant differences in the two groups (χ2 = 0.00, P > 0.05 ). Conclusions Different genotypes of the VDR gene existed in children of Han nationality. There were no correlation between VDR Apa I , Bsm I , Fok I , Taq I gene polymorphisms and children's dental fluorosis of Han nationality in this area.
ABSTRACT
<p><b>OBJECTIVE</b>To determine the root canal initial taper of mandibular second premolars of 13-23 year-old people by using Micro-CT.</p><p><b>METHODS</b>23 extracted, single root, human root canal of mandibular second premolars of 13-23 year-old people were selected. The teeth were embedded in resin. The resins were scanned using Micro-CT at a resolution of 10 microm. The photographs at each level of 1 mm perpendicular to the long axis of the tooth were chosen. Bucco-lingual (BL) and mesio-distal (MD) diameters of each canal were measured at cervical, middle and apical third of the canals. Finally the taper were calculated and analyzed.</p><p><b>RESULTS</b>The average taper of cervical, middle, and apical third of adolescents' root canals were 0.06, 0.08, 0.07 (mesio-distal direction) and 0.32, 0.21, 0.25 (bucco-lingual direction). The difference was not observed among thee level on mesiodistal direction about the canal taper by t-test (P > 0.05), but there was difference among three level on bucco-lingual direction about the canal taper by t-test (P < 0.05).</p><p><b>CONCLUSION</b>The change of bucco-lingual taper of mandibular second premolar of 13-23 year-old people is obvious, and the smallest taper is in middle third of the canal. The mesio-distal taper of the canals is smaller than the bucco-lingual taper and the change of mesio-distal taper isn't obvious.</p>