Effect of Luting Cement Film Thickness on the Pull-Out Bond Strength of Endodontic Post Systems.

Optimal bond strength between the prefabricated post/dowel to the surrounding dentin is essential. The present study aimed to analyze and compare the effect of three different cement film thicknesses on the pull-out bond strength of three different prefabricated post systems. Extracted natural teeth (N = 90) with similar root dimensions were acquired. Teeth were mounted in resin blocks, endodontically treated, sectioned at cemento-enamel junction, divided into three groups (A: Parapost Fiber Lux plus; B: 3M ESPE Relyx fiber post; and C: Parapost XP), and stored. Uniform post spaces were prepared for the groups (A and C: Length = 8 mm, Width = 1.5 mm; B: Length = 8 mm, Width = 1.6 mm). Each group (N = 30) was further subdivided into three subgroups (n = 10) based on the size (4, 5, and 6) of the post and cemented with resin cement (MultiLink-N, Ivoclar Vivadent). After thermocycling, the specimens were subjected to a pull-out test using a universal testing machine, and tensile force was recorded (MPa). Digital microscopic evaluations were performed for modes of failure. ANOVA and Tukey-HSD tests were used for statistics. Significant differences were observed for each tested material (p = 0.000). The lowest and highest bond strength values were recorded for Group C (Titanium post) and Group A (000), respectively. Multiple comparisons showed significance (p < 0.05) among all the groups, except for space 1 and space 2 (p = 0.316) for Group A. Most of the failures occurred within the cement-dentin and post-cement interface (Adhesive failures, 73.5%). An increase in the luting cement film thickness results in the decrease in pull-out bond strength of prefabricated posts luted with resin cement, irrespective of the type/material/shape of the post. The serrated fiber posts showed the highest pull-out bond strength compared to the smooth surfaced fiber posts or serrated metal posts. Increased pull-out bond strengths were observed when appropriate post space was created with the same sized drill as the post size.

Association between ENAM polymorphisms and dental caries in children.

AIM: Dental enamel, the most rigid biological tissue of the tooth known to mankind, is the most integral and fundamental part of the tooth. Enamel matrixes compile 5% of Enamelin peptides and at the time of tooth development, they are considered to effect the formation and elongation of enamel crystallites. ENAM plays critical role in enamel formation. Any changes in ENAM may affect the thickness of enamel and may lead to dental caries. The present study is aimed to evaluate the association of ENAM gene polymorphisms and susceptibility of dental caries development risk. MATERIAL AND METHODS: The present study was carried out on 168 South Indian children, children's with dental caries were included in study. Written consent was taken from their parents/guardians. Additionally 193 healthy individuals were enrolled as controls. Sampling was done after dental examination of the individuals. Three ENAM gene single nucleotide polymorphisms (SNPs) were rs7671281, rs3796704 and rs12640848 was genotyped to check their role in susceptibility of dental caries development risk. RESULTS: Out of three SNPs rs7671281 showed statistically significant risk association with dental caries susceptibility in this ethnic population at heterozygous allele CT (OR: 1.939, p = .01865) and with minor allele T (OR: 1.451, p = .001292). SNP rs3796704 showed significant protective association with dental caries in Indian population at heterozygous allele GA (OR: 0.409, p = .0192) and with minor allele A (OR: 0.645, p = .00875). SNP rs12640848 showed significant protective association with dental caries in Indian population at heterozygous allele AG (OR: 3.041, p = .00642) and with minor allele G (OR: 1.478, p = .02184). Preliminary insilico analysis also showed that rs7671281 (Ile648Thr) amino acid change will cause the structural and functional changes in ENAM protein. CONCLUSIONS: In the present study significant association was observed between ENAM gene SNP rs7671281 and dental caries susceptibility in South Indian children. These results suggested that ENAM gene variants may contribute to dental caries in children.

Pathogenic features of Streptococcus mutans isolated from dental prosthesis patients and diagnosed cancer patients with dental prosthesis.

Though S. mutans, virulence, and pathogenesis are characterized, reports are limited to the status of its carriage and virulence in patients with oral cancer and prosthesis. In this present study, we investigated the pathogenic characteristics of twenty strains of S. mutans of healthy subjects, fifteen of prosthesis patients, and eleven from oral cancer. The putative virulence gene and other factors, such as the ability to adhere to the oral epithelial cells, production of glycan and lactic acid of these strains were examined. Few of representative isolates of each group were used to see their activity on oral cancer cell line using cell cytotoxicity assay. The isolation rate of S. mutans was significantly more in carcinoma than prosthesis patients and control health group. The production of glycan and latic acid was together high in those isolates derived from prosthesis patients and patients with cancer. Adherence ability of strains isolated from prosthesis patients and cancer patients with oral prosthesis were significantly higher, compared to one isolated from a healthy individual. From our study results, we conclude that prosthesis patients and cancer patients with prosthesis carried a high number of S. mutans in their oral cavities. SIGNIFICANCE AND IMPACT OF STUDY: This study report that prosthesis patients and cancer patients with prosthesis carried a high number of S. mutans in their oral cavities. However, the S mutans are commensals still they have the capability to raise the severity of disease condition due to their ability to produce glycan and lactic acid. In our study, we proved that the adherence to buccal epithelial cells was significantly increased in S. mutans isolates of prosthesis patients and cancer patients. These indicate that in prosthesis patients as well as in cancerous patient's microbes had more potential to cause infection and increase the severity.