RESUMEN
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.
RESUMEN
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.
