Evaluation of Candida albicans biofilm formation on conventional and computer-aided-design/computer-aided manufacturing (CAD/CAM) denture base materials.

Background and Purpose: The human mouth mucosal surface is colonized by indigenous microflora, which normally maintains an ecological balance among different species. However, certain environmental or biological factors may disrupt this balance, leading to microbial diseases. Candida albicans biofilms are formed on indwelling medical devices and have an association with both oral and invasive candidiasis. This study aimed to compare the amount of adherent C. albicans and the biofilm formed on different denture base materials. The adhesion of C. albicans to denture base materials is widely recognized as the main reason for the development of denture stomatitis. Materials and Methods: In total, 56 polymethyl methacrylate (PMMA) acrylic resin disc-shaped samples were divided into four groups as follows: 1) chemically polymerized PMMA, 2) heat-polymerized PMMA, 3) computer-aided design and computer-aided manufacturing (CAD/CAM) PMMA in high polish, and 4) CAD/CAM resins in glazed form. The adherent cells and formation of C. albicans strains (562, 1905, 1912, and 1949) biofilm were measured by the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) method and use of a microplate reader. Moreover, morphological alterations of C. albicans cells were investigated using scanning electron microscopy (SEM). Results: The biofilm formation was significantly lower on CAD/CAM acrylic resins, compared to conventional denture base materials. The obtained results were confirmed by the SEM images of C. albicans biofilms. CAD/CAM PMMA-based polymers may be preferable to inhibit C. albicans biofilm formation and reduce Candida-associated denture stomatitis in long-term use. Conclusion: Based on the findings, the CAD/CAM technique can be used as an efficient technique for denture fabrication as it inhibits microbial accumulation, and consequently, microbial biofilm.

Comparative Evaluation of Physical and Mechanical Properties of Different Brands of Primary Molar Stainless-Steel Crowns: An In Vitro Study.

BACKGROUND: There is some cases of perforation and undesirable properties of some primary molars stainless steel crowns. AIM: The aim of this study was to compare the physical and mechanical properties of different commercial brands of these crowns. METHODS: In an in vitro study, 10 stainless steel tooth crowns of the second primary mandibular molars size 6 of 4 different commercial brands (a total of 280 crowns) were evaluated. These crowns were included KTR Pre-trimmed and Crimped Nichro Stainless Steel Primary Molar Crowns (KTR, China); 3M Stainless Steel Primary Molar Crowns (ESPE, St paul; USA); NuSmile SSC Pre-contoured (Inc, Houstone, TX; USA) and Kids crown (Shinghung, Seoul; Korea). Corrosion and galvanic corrosion, wear, microhardness, compressive strength, fatigue strength of crowns and weight percent of elements were investigated. RESULTS: The highest rate of microhardness, compressive and Fatigue strength of the crowns were made by Nu Smile > 3M > Kids Crown > KTR respectively. The highest rate of corrosion potential in corrosion and Galvanic corrosion tests was in KTR > Kids crowns > 3M > Nu smile respectively. The order of crown wear was KTR > Kids Crown > 3M > Nu Smile respectively. The highest amount of nickel element was found in the Nu Smile crown and the highest amount of chrome in the 3M crown with a significant difference with others (p < 0.001). The KTR and Kids crowns lacked molybdenum. CONCLUSION: The results showed that Nu Smile crown has better physical and mechanical properties than other evaluated crowns in this study.

Effect of untreated zirconium oxide nanofiller on the flexural strength and surface hardness of autopolymerized interim fixed restoration resins.

OBJECTIVE: Autopolymerized poly methyl methacrylate (PMMA) resin is commonly used for the construction of interim restorations; however, it has less than optimal mechanical properties. In this article, we evaluated the reinforcing effect of adding untreated zirconia nanoparticles on the flexural strength and surface hardness of this resin. METHODS: A total of 80 specimens were fabricated. Forty each were used for the flexural strength test and for the surface hardness test. The specimens were categorized into four groups of 10 specimens each as follows: pure PMMA, PMMA with 1%, PMMA with 2.5%, and PMMA with 5% weight of untreated zirconia nanofillers. The flexural strength of the specimens was evaluated by the three-point bending test, and the surface hardness was assessed by micro Vickers hardness test. The data obtained from these tests were statistically analyzed using one-way ANOVA and Tukey tests. In addition, the fracture surface characteristics were assessed using scanning electron microscopy. RESULTS: Flexural strength testing showed a significant increase in the group with 2.5% zirconia nanofillers, but not in the groups with 1% and 5% nanofillers. Surface hardness was also significantly increased in the groups with 2.5% and 5% nanofillers, but not in the 1% group. The SEM images showed a highly brittle fracture in the pure PMMA group and noticeably less brittle fracture in the group with PMMA with 2.5% weight of zirconia nanofillers. Several cracks and void were also observed in the group with 5% weight of nanofillers. CONCLUSION: Reinforcement of the autopolymerized acrylic resin with 2.5% weight of untreated zirconia nanofillers significantly increased its flexural strength and surface hardness. CLINICAL SIGNIFICANCE: The interim restorations play an important role in protection of hard and soft oral tissue and providing the critical function and esthetics before the final restoration replacing. Temporary restorations must have sufficient flexural strength to resist deformation during mastication force. Moreover, sufficient surface hardness is also necessary to resist abrasion. The color stability of materials is considered as an important clinical criterion, specifically in esthetics zone. Several materials have been applied to improve the flexural strength and surface hardness for representing clinical success. Zirconia nanoparticles show desirable features, such as high hardness, biocompatibility, and favorable color because of its white color. It seems that the addition of the nano zirconia to acrylic resins can be the appropriate method for improving interim restoration.

Assessment of vertical root fracture using cone-beam computed tomography.

PURPOSE: The aim of this study was to investigate the accuracy of cone-beam computed tomography (CBCT) in the diagnosis of vertical root fractures in a tooth with gutta-percha and prefabricated posts. MATERIALS AND METHODS: This study selected 96 extracted molar and premolar teeth of the mandible. These teeth were divided into six groups as follows: Groups A, B, and C consisted of teeth with vertical root fractures, and groups D, E, and F had teeth without vertical root fractures; groups A and D had teeth with gutta-percha and prefabricated posts; groups B and E had teeth with gutta-percha but without prefabricated posts, and groups C and F had teeth without gutta-percha or prefabricated posts. Then, the CBCT scans were obtained and examined by three oral and maxillofacial radiologists in order to determine the presence of vertical root fractures. The data were analyzed using IBM SPSS 20.0 (IBM Corp., Armonk, NY, USA). RESULTS: The kappa coefficient was 0.875±0.049. Groups A and D showed a sensitivity of 81% and a specificity of 100%; groups E and B, a sensitivity of 94% and a specificity of 100%; and groups C and F, a sensitivity of 88% and a specificity of 100%. CONCLUSION: The CBCT scans revealed a high accuracy in the diagnosis of vertical root fractures; the accuracy did not decrease in the presence of gutta-percha. The presence of prefabricated posts also had little effect on the accuracy of the system, which was, of course, not statistically significant.