RESUMO
Objective To study the distribution of ameloblastin(AMBN) gene polymorphism in coal-fire caused fluorosis (CFCF) in Chongqing municipality and the relationship between AMBN gene polymorphism and the susceptibility to dental fluorosis.Methods Under a case-control study,100 children aged 8-12 and 30 adults with dental fluorosis were enrolled in Wushan and Fengjie counties of Chongqing from December 2010 to February 2011.Another 100 children aged 8-12 and 30 adults with non-dental fluorosis were chosen as internal control groups together with 50 childrenand 30 adults without dental fluorosis were selected as external control groups in the non-epidemic area of Yubei district.DNA was extracted from peripheral blood sample of these people.Genotype of AMBN gene 7 extron 538_540delGGA,10 extron 657A＞G and 13 extron 986C＞T loci were detected using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)technique.Results The rates of 7 extron 538_540delGGA loci among case,internal and external control groups were as follows:GGA/GGA-/-61.2％ (74/121),78.5％ (102/130),74.3％ (52/70) ;GGA/-:24.0％ (29/121),15.4％ (20/130),22.9％ (16/70) ;-/-:14.8％ (18/121),6.1％ (8/130),2.8％ (2/70),the difference was statistically significant (x2=14.353,P＜0.05).The AA appeared to be 86.8％(105/121),93.1％(121/130),91.4％(64/70) and AG were 13.2％(16/121),6.9％(9/130),8.6％ (6/70),with difference not statistically significant (x2=2.972,P＞0.05).CC appeared as 81.0％ (98/121),90.0％(117/130),87.1％(61/70) while CT as 19.0％(23/121),10.0％(13/130),12.9％(9/70),with difference not statistically significant (x2=4.319,P＞0.05).In comparing with the two control groups,the frequency of GGA/GGA was decreasing (x2 values were 8.957,3.405,respectively,P＜0.05) while the frequency of-/-was increasing (x2 values were 5.134,6.833,respectively,P＜0.05).Results from the univariate analysis showed that the individuals who were carrying-/-genotype had an increased risk of suffering from fluorosis (OR values were 2.7,5.9,respectively,P＜0.05).When compared with the internal control group,the CT genotype of case group showed an increase (x2=4.139,P＜0.05) while individuals that carrying CT genotype had an increased risk of suffering from fluorosis (OR=2.1,P＜0.05),in epidemic-area.Conclusion Our results showed that the 7 extron 538_540delGGA and the 13 extron 986C＞T loci polymorphism in AMBN gene might serve as the susceptibility factors causing the coal-fired fluorosis.