Vol 5, No 3 (2008)
Proceeding Abstracts
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Objective: The purpose of this study was to evaluate the solubility of three luting cements in artificial saliva.
Materials and Methods: Twenty disks (10×4 mm) of polycarboxylate, zinc phosphate and glass ionomer cements were prepared according to manufactures’ instructions. After setting, they were desiccated and each ten specimens were immersed in artificial saliva with special pH (3 or 5), circulated with magnetic field for 10 days. Then disks were again desiccated and weighed. Solubility values were deduced from these different measures.
Results: For the two pH, solubility were significantly lower in glass ionomer luting ce-ment, and polycarboxylate showed the most weight loss of all the materials tested (P<0.05). The solubility values were more in acidic environment (P<0.05).
Conclusion: The pH of the environment strongly affected the solubility of the materials. Cement type also has significant effects on solubility values.
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Objective: This in vitro study evaluated the fracture strength and bending amount of twotypes of fiber reinforced composite (FRC) and cast metal frameworks used for fabrication of inlay fixed partial dentures (IFPDs).
Materials and Methods: Seventy-two extracted first maxillary premolars and molars (36 each) were embedded in acrylic resin to represent a missing of second maxillary premolar. FRC IFPDs were fabricated using Stick and Fiber-Braid fiber bundles and IFPDs using cast metal alloy (12 for each group). The specimens were stored for 2 weeks at 37°C(SD=1) in distilled water, thermocycled (5-55°C, x 2500) and statically loaded to fracture. The initial bending prior to fracture was evaluated. The data were analyzed using paired t-test and ANOVA test.
Results: The fracture strength was significantly higher in the FRC groups (P<0.05); also, the fracture strength was significantly higher in Stick group than Fiber-Braid group (P<0.05). The amount of bending was significantly greater in the FRC groups (P<0.05). The amount of difference in bending between the two groups of FRC was not statistically significant.
Conclusion: Within the limits of this in vitrostudy, the results suggest that the FRC IFPDs can be used as a conservative, esthetic alternative to the IFPDs with cast metal frameworks. The results of this study should be confirmed by long-term clinical investiga-tions.
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Objective: The main goal of this study was to evaluate stress distribution of endodonti-cally treated maxillary central incisors restored with glass fiber posts, composite resin cores, and crowns with different ferrule designs.
Materials and Methods: Four three-dimensional models of a maxillary central incisor were modeled in SolidWorks 2006. Tooth with no ferrule, tooth with a 2 mm circumferen-tial ferrule, tooth with a 2 mm beveled ferrule and tooth with a 0.5 mm circumferential ferrule. The teeth were restored with glass fiber posts, composite resin cores, and full ce-ramics crowns. Each model was loaded (1 N) on the palatal side at an angle of 45 degrees to tooth long axis. Von Mises stress findings along the inner surface of the root canals were assessed and compared.
Results: The Von Mises Stress at CEJ was the highest in the model without a ferrule when compared to the other models (without ferrule 0.0696, short ferrule 0.0492, cylindrical fer-rule 0.0248, and beveled ferrule 0.0387 MPa).
Conclusion: Endodontically treated maxillary central incisors with a ferrule length vary-ing between 0.5 mm and 2.0 mm exhibit lower stress distribution compared to those with-out a ferrule. Keeping a long ferrule is suggested to decrease the stress at the cervical area of restored teeth.
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Objective: The aim of this study was to investigate the existence of human T-lymphotropic virus type 1 (HTLV-1) in subgingival plaque of HTLV-1 seropositive pa-tients.
Materials and Methods: A total of 18 patients including 13 females and fivemales, with a mean age of 37 years participated in this descriptive study. Half of them were HTLV-1 carriers and the others were in HTLV-1 associated myelopathy tropical spastic paraparesia (HAM/TSP) stage.Subgingival dental plaque samples were taken using sterile paper points and examined to detect HTLV-1 using polymerase chain reaction (PCR).
Results: None of the carrier stage patients revealed HTLV-1 virus, while only one patient in the HAM/TSP group was found with the virus.
Conclusion: This study showed that the existence of HTLV-1 virus in subgingival plaque of patients suffering from HTLV-1 in carrier and HAM/TSP stages with healthy periodon-tium is rare. Studies with larger samples are recommended.
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Objective: The purpose of this study was to investigate the histological response to delib-erate perforation repaired using amalgam or MTA either immediately or with delay on cats’ molars.
Materials and Methods: Twenty-eight molar teeth from four cats were used in this ex-perimental randomized study. After preparing the access cavity, the floor of pulp cham-bers were deliberately perforated with a round bur No. 5. The teeth were randomly divided into four groups of seven. In groups one and two,the perforation was immediately sealed with amalgam and MTA, respectively. In groups three and four, the perforations were leftexposed to saliva for six weeks and then sealed with amalgam or MTA. The animals were sacrificed four months later and the specimens processed. The samples were blindly exam-ined for inflammatory reaction and healing process under light microscope. The data were analyzed with Mann-Whitney U and Fisher exact tests.
Results: The type of the materials used has no significant effect on the severity of in-flammation; while, immediate or delayed repair of furcal perforation has, and immediate application of, MTA produced less inflammation than that of amalgam (P<0.05). No dif-ferences were found in vasodilatation, abscess formation or healing process between the immediate and the delayed repair groups (P=0.13).
Conclusion: MTA is a more suitable material than amalgam for perforation repair, par-ticularly when used immediately after perforation.
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Objective: The aim of this in vitrostudy was to evaluate the effect of the type of solvent in silane solution on microtensile bond strength of fiber posts to composite resin cores af-ter application of 24% hydrogen peroxide.
Materials and Methods: Eighteen white fiber posts, immersed in 24% hydrogen peroxide were divided into three groups (n=6). In the group A post surfaces were silanized with an ethanol based solution, in group B with an acetone based solution, in the group C with and un-diluted methacryloxytrimethoxysilane (as the control group). The cores were built up using flowable composite. Microtensile bond strength test and evaluations using stereomi-croscope were performed on the samples and the data were analyzed using one-way ANOVA and Tukey HSD tests.
Results: A significant difference was observed between the amounts of microtensile bond strength of fiber poststo composite cores in the groups A and B, and the ones in group C (P<0.05). There was no such difference between groups A and B (P>0.05).
Conclusion: The type of solvent in silane solution has no effect on microtensile bond strength between fiber post andcomposite resin core after application of 24% Hydrogen Peroxide.
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Objective: The purpose of the present study was to assess the microleakage of composite restorations with and without a cervical amalgam base and to compare the results of dif-ferent composites and bonding agents.
Materials and Methods: One hundred and twenty mesio-occlusal (MO) and disto-occlusal (DO) Class II cavities were prepared on sixty extracted permanent premolar teeth. The teeth were randomly divided into four groups of 30 and restored as follows:
In group A, the mesio-occlusal cavity (MO), Scotchbond multi purpose plus + Z250 and in the disto-occlusal (DO) cavity, Prompt-L-Pop + Z250 were applied. As for group B, in the MO and DO cavities, Clearfil SE Bond + Clearfil APX, and varnish + amalgam (In box) + Clearfil SE Bond + Clearfil APX were used respectivelywhile in group C; the teeth were restored with amalgam and varnish mesio-occlusally and with amalgam only disto-occlusally. As for group D, varnish + amalgam (in box) + Scotchbond multi purpose plus + Z250 were applied mesio-occlusally and Varnish + Amalgam (in box) + Prompt–L–Pop + Z250 disto-occlusally.
Marginal leakage was assessed by the degree of dye penetration into various sections of the restored teeth. Chi-square and Fisher's exact tests were used for data analysis.Results: Microleakage in gingival margin was more than that in occlusal margin (P<0.05) and microleakage of combined amalgam-composite restorations was significantly lower than that of conventional composite and amalgam restorations.
Conclusion: Marginal microleakage decreased by using amalgam at the base of the box in Class II composite restorations.
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Objective: In a cavity prepared through endodontic surgery, application of a material to provide apical seal and prevent bacterial and tissue exudates is of great importance. The purpose of this study was to compare the sealing ability of Biocalex with white MTA, gray MTA, and amalgam as root-end fillings.
Materials and Methods: Sixty-six single-rooted extracted human teeth were cleaned, shaped, and obturated with gutta-percha. The root apices were resected and 3 mm deep retrograde cavity was prepared. The teeth were assigned randomly into four groups of 15 teeth each and retrofilled with Biocalex, gray MTA, white MTA, and amalgam. Six teeth served as positive and negative controls. All root surfaces, except the ending part, were covered with two layers of nail polish. The roots were then stored in 2% methylene blue for 72 hours and embedded in polyester resin. The teeth were sectioned buccolingually and maximum extent of dye penetration was evaluated through a stereomicroscope. Statis-tical analysis was carried out by one way ANOVA and Tukey test.
Results: Biocalex showed significantly less leakage compared to the other three materials P<0.05. White MTA showed significantly lower amount of leakage as Compared to gray MTA and amalgam P<0.05.
Conclusion: The findings of this study showed that retrograde filling with Biocalex can achieve proper sealing ability and this material can be used as an alternative for MTA and amalgam.
