Shielding effect of a customized intraoral mold including lead material in high-dose-rate 192-Ir brachytherapy for oral cavity cancer. (57/91)

A high-dose-rate (HDR) 192-Ir brachytherapy using a customized intraoral mold is effective for superficial oral cavity cancer, and the surrounding normal tissue is kept away from the radioactive source with gauze pads and/or mouth piece for reducing the dose on the normal tissues. In the Tokushima university hospital, the mold has a lead shield which utilizes the space prepared with sufficient border-molding by a specific dental technique using modeling compound. In HDR 192-Ir brachytherapy using a lead shielded customized intraoral mold, there are no reports measuring the absorbed dose. The purpose of the present study is to measure the absorbed dose and discuss the optimum thickness of lead in HDR 192-Ir brachytherapy using a customized intraoral mold with lead shield using a 1 cm thickness mimic mold. The thickness of lead in the mold could be changed by varying the arrangement of 0.1 cm thickness sheet of the acrylic resin plate and lead. The measured doses at the lateral surface of the mold with thermo-luminescence dosimeter were reduced to 1.12, 0.79, 0.57, 0.41, 0.31, 0.24 and 0.19 Gy and the ratios to the prescription dose were reduced to 56, 40, 29, 21, 16, 12 and 10 percent as lead thickness increased from 0 to 0.6 cm in 0.1 cm increments, respectively. A 0.3 cm thickness lead was considered to be required for a 1 cm thickness mold, and it was necessary to thicken the lead as much as possible with the constraint of limited space in the oral cavity, especially at the fornix vestibule.  (+info)

Effects of sulfur-based hemostatic agents and gingival retraction cords handled with latex gloves on the polymerization of polyvinyl siloxane impression materials. (58/91)

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Dimensional accuracy of 2 irreversible hydrocolloid alternative impression materials with immediate and delayed pouring. (59/91)

OBJECTIVE: To assess dimensional accuracy and stability of 2 irreversible hydrocolloid alternative impression materials with immediate and delayed pouring. METHODS: Two alternative impression materials, AlgiNot FS and Position Penta Quick, were compared with a traditional irreversible hydrocolloid, Jeltrate Plus antimicrobial alginate. Impressions were made of a metal model with 4 cylinders of known dimensions, with pouring performed immediately or after 4 hours of storage. A digital micrometer was used to measure cylinder diameter on the model and the poured casts. Dimensional changes were analyzed according to American National Standards Institute/American Dental Association (ANSI/ADA) Specification 19 (2004 version) (alpha=0.05). RESULTS: There were significant differences among the 3 materials, between the 2 pour times and as a function of storage time (multivariate analysis of variance, p<0.001). One-way analysis of variance revealed no significant differences between the 2 alternative impression materials, but changes for these materials differed significantly from those for the traditional impression material for immediate (p<0.05) and 4-hour (p<0.001) pouring. Linear dimensional changes for the 2 substitute materials were within the limits of the ANSI/ADA specification. CONCLUSIONS: With immediate pouring, both alternative impression materials exhibited minimal dimensional changes, which were maintained or reduced with 4-hour pouring. For both pouring times, these changes were less than 0.5%. CLINICAL SIGNIFICANCE: The minimal dimensional changes observed with these irreversible hydrocolloid alternative impression materials after 4 hours of storage may save chairside time and help to produce accurate results for procedures such as partial denture framework, surgical guides, and pediatric and orthodontic devices.  (+info)

Does the contact time of alginate with plaster cast influence its properties? (60/91)

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Effect of immersion disinfection of alginate impressions in sodium hypochlorite solution on the dimensional changes of stone models. (61/91)

This study investigated the effect of the immersion of alginate impressions in 0.5% sodium hypochlorite solution for 15 min on the dimensional changes of stone models designed to simulate a sectional form of a residual ridge. Five brands of alginate impression materials, which underwent various dimensional changes in water, were used. A stone model made with an impression that had not been immersed was prepared as a control. The immersion of two brands of alginate impressions that underwent small dimensional changes in water did not lead to serious deformation of the stone models, and the differences in the dimensional changes between the stone models produced with disinfected impressions and those of the control were less than 15 microm. In contrast, the immersions of three brands of alginate impressions that underwent comparatively large dimensional changes in water caused deformation of the stone models.  (+info)

Typodont versus live patient: predicting dental students' clinical performance. (62/91)

In this study, the authors evaluated the accuracy and precision of non-clinical testing for dental students' crown preparation proficiency on a manikin-mounted typodont as a predictor of performance on patients. Eighty-six seniors at Baylor College of Dentistry were evaluated by three calibrated senior faculty members from the general dentistry department. Four areas of interest were evaluated: occlusal reduction; axial reduction; margins, design, and finish line; and operative environment. Standardized grading scales were utilized to evaluate these preparation components. The kappa agreement statistic was used to assess agreement for the areas, which were then compiled to get an overall performance score. A Bland-Altman plot was generated and analyzed for agreement on overall performance between typodont and patient. Results of the analyses showed weak agreement between the two measurements for all four areas of interest with large variation in the differences. When the pairs of overall performance scores were compared, the Bland-Altman plot indicated that the typodont composite score was often larger than the patient composite score, especially for poorer performing students. The authors conclude that students' clinical performance on typodonts is a poor predictor of their clinical performance on patients since the students performed much worse on the clinical crown examination than on the typodont examination.  (+info)

Efficacy of various spray disinfectants on irreversible hydrocolloid impression materials: an in vitro study. (63/91)

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A comparative study to evaluate the discrepancy in condylar guidance values between two commercially available arcon and non-arcon articulators: a clinical study. (64/91)

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