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Biomedical subjects

P Millstein

Publications and source records attributed to P Millstein.

9 recordsLinked to original sources
PubMed2001

Determining the accuracy of articulator interchangeability and hinge axis reproducibility.

STATEMENT OF PROBLEM: It has been reported that articulators are interchangeable, which means that a clinician should be able to use one articulator and send casts to a dental laboratory with the assurance that the casts will be remounted with positional accuracy on a similar articulator. PURPOSE: The purpose of the study was to determine whether mounted casts could be transferred from 1 articulator to another with positional accuracy and whether the hinge axis was reproducible in each of the articulators tested. MATERIAL AND METHODS: This study compared left and right second premolars and first molar occlusal contact areas with respective contact areas of like-mounted casts. Five calibrated Whip Mix 3040, 5 calibrated Girrbach Artex AL, and 5 calibrated KaVo Protar articulators were tested. Impact-resistant resin casts mounted in occlusion on 1 articulator were transferred to 4 like articulators. Each of the 5 articulators of each brand was opened and closed 10 times. Ten vinyl polysiloxane right and left posterior interocclusal records of the occluded casts were made for each articulator. The use of a computerized image analysis program provided quantitative measurements of light transmitted through the occlusal records. A Kruskal-Wallis test was used for each of the 4 independent variables of the study (molar differences, premolar differences, left differences, right differences). By using a calibrated grid, a numerical assessment of positional changes was made in millimeters. RESULTS: None of the articulator systems was found to be exact, and no single articulator was an exact duplicate of another (P<.01). The Whip Mix articulator showed greater deviation both in hinge axis repeatability and in articulator interchangeability than the KaVo. The Artex articulator provided the most consistent hinge axis repeatability and interchangeability of the 3 brands of articulators. CONCLUSION: The Artex brand reproduced dental cast positions more consistently than the other articulators tested.

Acrylic Resins↗
PubMed2001

An evaluation of occlusal contact marking indicators. A descriptive quantitative method.

BACKGROUND: Dentistry needs an accurate means of recording occlusal contacts. The authors undertook a study to evaluate the accuracy of occlusal contact marking indicators and the reproducibility of their results. METHODS: The authors recorded occlusal contact areas using occlusal indicators made of paper, film and silk. They studied 10 indicators by testing them on articulator-mounted, impact-resistant casts and measuring the surface area of the resultant contact marks made on impact using a video camera, a frame grabber and a computer-linked image analyzer. RESULTS: All indicators differed in surface area markings between and within groups. The indicator's thickness and color and the material from which it was made separately and interactively had an effect on the size of the markings. Measurements were evaluated at a P = .05 significance level. The authors used Bonferroni-adjusted cutoffs when computing post hoc pairwise comparisons. The data were grouped into four categories: descriptive statistics, comparison of indicators by surface area marked, indicator thickness and repeatability. CONCLUSIONS: Indicators vary, and their markings may not be repeatable even when they are used alike. Further study is required, as is the development of an indicator measuring standard. CLINICAL IMPLICATIONS: Indicators are used to determine occlusal disharmony and to establish occlusal harmony. Since the accuracy of the markings can be questioned, the interpretation of the markings may be correct but the accuracy of the markings themselves may be misleading.

Analysis of Variance↗
PubMed1998

Determining the accuracy of stock and custom tray impression/casts.

A study was conducted to evaluate the accuracy of casts made from stock tray and custom tray impressions using polysiloxane impression material. The results indicate that all casts distort but that impressions made from custom trays were more accurate and consistent in reproduction than were stock tray impressions.

Acrylic Resins↗
PubMedDate not supplied

Tube angulation effect on radiographic analysis of the implant-abutment interface.

The purpose of this study was to determine the maximum permissible x-ray tube angulation that can be used to verify the fit of an abutment. An implant and an abutment were assembled with an abutment screw. A variety of openings were created between the abutment and the implant. Radiographs were taken combining the different gaps with various x-ray tube angulations. The radiographs were randomly presented to 8 clinicians, who judged the interface as open or closed. The results indicate that a radiographic analysis of interface openings becomes subjective with tube angulations of more than 5 degrees.

Chi-Square Distribution↗
PubMedDate not supplied

A comparison of the accuracy of two removable die systems with intact working casts.

This study evaluated the reproducibility of die position using two removable die systems and two die stones. Poly(vinyl siloxane) impressions were made of a stainless steel, U-shaped arch with four evenly spaced abutments. Six groups were evaluated: Zeiser system/Fuji Rock; Zeiser system/Die Keen; solid cast/Fuji Rock; solid cast/Die Keen; Fuji Rock/Pindex; and Die Keen/Pindex. An optical comparator was used to measure the height of each abutment, the distance between the anterior abutments, and the distance between the posterior abutments. The Zeiser system with either Fuji Rock or Die Keen yielded the greatest accuracy. Die Keen exhibited more linear expansion than Fuji Rock, and solid casts had less distortion than the Pindex system.

Analysis of Variance↗
PubMedDate not supplied

The effect of alcoholic and nonalcoholic mouthwashes on heat-treated composite resin.

Studies show that mouthwashes containing alcohol soften the surface of composite resin restorations. The present study determined weight change over time in heat-treated composite resin soaked in alcohol and nonalcohol-containing mouthwashes. The results indicate that samples soaked in mouthwashes containing alcohol gained significantly more weight than samples soaked in nonalcoholic mouthwashes.

Absorption↗