EXAMINE THE PIT AND FISSURE SEALANT RETENT ON RATE OF FIRST  
  PERMANENT MOLARS IN PRATOM 2 AND 3 STUDENTS AFTER 
  APPLICATION   PROGRAM FOR 1 AND 2 YEARS IN SOMITTRAPAPH 140th , 
  SCHOOL OF PUBLIC,   SOPISAI DISTRICT, NONG KAI PROVINCE. (NO. 001)

                  A descriptive study has been done to evaluate the sealant application program in Somittrapaph 140^th, School of public, Sopisai District, Nong Kai Province. The Ministry of Public Health advocated this sealant application program to prevent occlusal caries. Dental sealant was placed by dental nurses on first permanent molars of Pratom 1 (first grade) students in 1996 and 1997 under the mobile clinic setting. Forty Pratom 2 (second grade) students (160 teeth) and thirty-four Pratom 3 (third graded) students (136 teeth) whose teeth had sealant placed for 1 and 2 years respectively were examined for the sealant retention rates. 39.17% and 29.31% of all teeth had sealant retained in good condition after 1 and 2 years respectively. 41.53% of teeth required sealant replacement and 24.15% had caries associated with sealant. This finding suggested that the sealant program in this school had low 1 and 2 years success rates; and the program, therefore, should be further evaluate for the cost-effectiveness.

Mahidol Dental Journal 2000 Vol.20(1) ;47-54.

  IMMUNOHISTOCHEMICAL LOCALLIZATION OF CYTOKERATIN AND PCNA
  DESMOPLASTIC AMELOBLASTOMA. ( NO. 002)

                  Desmoplastic ameloblastoma is histologically characterized by extensive stromal collagenization or desmoplasia. In this study, anti-cytokeratin as well as anti-PCNA, were used to detect the expression of these proteins in the desmoplastic ameloblastoma. Six cases of desmoplastic ameloblastoma were used. All specimens were obtained from Okayama University Dental Hospital. The monoclonal anti-cytokeratin No.8, and 19, anti-cytokeratin squamous epithelium (SE-K), anti-PCNA were used in this study. The tumor islands varied in shape and size and in some areas they were compressed by the desmoplastic stroma resulting in narrow strands or cords which appeared as sheets. The tumor islands lacked the peripheral palisading of columnar cells and were rimmed with cuboidal or flattened cells. Central parts of the nests often showed squamous metaplasia and scattered foci of keratinazation. The tumor nests showed the different patterns of response to anti-cytokeratin antibodies. In some of the tumor nests, all tumor cells were positive to antibodies of CK-8, and 19, but had the limited area of staining in the central area with the SE-K antibodies. However, some of the tumor nests show the positive staining in the localized, periphery area with CK 8, 19 antibodies. The staining periphery tumor cells are cuboidal and columnar cell shape while the non-positive staining tumor cells are stellate-shape. Some of peripheral cells of tumor nest were positively detected while the stroma part of connective tissue were strongly stained with PCNA. We noted the intense of PCNA staining of the stroma around the tumor nest. These results suggests desmoplastic ameloblastoma composed many different tumor cell types, and have high proliferating activity in the desmoplastic stroma.

  IN VITRO ANTIBACTERIAL EFFECT OF DENTAL VARNISHES (NO. 003)

                  The purpose of the present study was to evaluate and compare the antibacterial properties of different concentrations of a chlorhexidine varnish prepared at Faculty of Dentistry, Mahidol University (range 5-40%), 1% chlorhexidine/thymol varnish (Cervitec®), 0.1% fluoride varnish (Fluor Protector®) and 2.26% fluoride varnish (Duraphat®). Agar diffusion method was used to test the antibacterial effect against clinical strain of Streptococcus mutans including KPSK2 reference strain. After 48 hours incubation, zones of bacterial inhibition of these varnishes were measured in millimeters and compared with the negative control (alcohol). The chlorhexidine varnish demonstrated excellent activity against the bacterial tested (p<0.01) and revealed bacterial inhibition in a dose-response manner. No significant difference was found between the concentrations (p>0.05). The antibacterial effects of 1% chlorhexidine/thymol varnish and 2.26% fluoride varnish were comparable, however, less than that noted with chlorhexidine varnish. While 0.1% fluoride varnish slightly inhibited the growth of Streptococcus mutans but no significant difference was found when compared with the control (p>0.05). The reference strain and clinical strains (tested bacterial strains) were similarly inhibited. These in vitro results indicated that 5-40% chlorhexidine varnish, 1% chlorhexidine/thymol varnish and 2.26% fluoride varnish were effective in inhibiting the growth of Streptococcus mutans while 0.1% fluoride varnish was not.