Film thickness measurements of a paint-on die spacer.
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Chemical Phenomena↗
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Results for “DENTAL MODELS”
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Matrices in metal ceramics.
Restoration of the severely debilitated dentition continues to be challenging for the restorative dentist. The advantages of determining the treatment position, fabrication of a diagnostic wax-up, and the use of matrices for making provisional and final restorations has been described. This article reviews the past stages in the restorative process regarding matrices and their use. A new technique is suggested that greatly simplifies the most time-consuming steps for the dentist and technician. This system allows for control of vertical dimension, esthetics, and the maintenance of occlusal position and detail. A technique for making porcelain occlusal restorations is described.
Dental Articulators↗
Detail reproduction of soft tissue: a comparison of impression materials.
The extent to which an impression material reproduces detail is influenced by factors such as viscosity, wettability, handling properties, and voids. This clinical study compared the ability of several impression materials to register soft tissue without creating voids and produce detailed gypsum casts. Thirty impressions of the hard palate of a single subject were made by use of a custom-cast metal framework serving as an impression tray. Six impression materials commonly used in clinical practice were tested. Die stone casts made from the impressions were evaluated and ranked by five judges. Polyether and hydrophilic addition silicone were judged best in terms of detail reproduction and zinc oxide-eugenol and polysulfide low-viscosity materials were judged worst in this regard. Impression voids were minimized with low-viscosity polysulfide and zinc oxide-eugenol when compared with addition silicones (low and medium viscosities).
Calcium Sulfate↗
The fungicidal effect of ultraviolet light on impression materials.
The effects of ultraviolet (UV) light on fungi and impression materials were tested. UV light (250 microW/cm2) killed most Candida organisms (10(3) cells/ml) within 5 minutes. UV light (8000 microW/cm2) killed most C. albicans (10(7) cells/ml) within 2 minutes of exposure. The effect of UV light on dimensional change and surface roughness of impression materials (irreversible hydrocolloid, agar, and silicone rubber) was tested. The results showed that neither dimensional change nor surface roughness of the impression materials were affected. The results of this study indicate that UV light disinfects impression materials that are contaminated with Candida organisms.
Agar↗
A comparative analysis of the accuracy of implant transfer techniques.
Four different implant transfer techniques using two master cast systems (solid cast and Zeiser system) were evaluated and compared with respect to the accuracy with which abutment positions were reproduced. A stainless steel experimental analogue with two anterior and two posterior fixtures and abutments was fabricated. Polyether impressions (14 each) were made by use of four techniques, (I) nonsplinted, (II) splinted with dental floss and acrylic resin, (III) splinted with orthodontic wire and acrylic resin, and (IV) splinted with acrylic resin alone. The fourteen impressions of each technique were divided into two equal groups: group 1, solid cast system, and group 2, Zeiser system. The abutments of each master cast were measured vertically and horizontally with a profile projector. Statistical analysis indicated no significant difference between the splinted and nonsplinted techniques. The Zeiser system provided more accurate interabutment relationships for the posterior region than the solid cast system.
Acrylic Resins↗
Segmental framework matrix: master cast verification, corrected cast guide, and analog transfer template for implant-supported prostheses.
A procedure is presented whereby a sectioned acrylic resin framework pattern for an implant-supported prosthesis is used for multiple purposes. It captures the three-dimensional spacial relationship of a dental implant. It acts as an analog transfer template, corrected cast guide, and a rigid scaffolding for the actual sculpting of the framework pattern.
Acrylic Resins↗
A matrix procedure for reproducing natural or carved tooth contours in porcelain laminate veneers.
A procedure is described for making porcelain laminate veneers by using a preformed acrylic resin matrix to reproduce the original tooth form and surface texture. The procedure can be modified to allow alterations to the original contours by adding wax to, or carving, a preliminary cast. A silicone impression is made of either the teeth preoperatively or the altered cast and is used to construct a translucent heat-cured acrylic resin matrix. The matrix is fitted to the working cast and used to condense the porcelain for veneers. A patient's restorations are used to illustrate the procedure.
Acrylic Resins↗
An accurate impression method for implant prosthesis fabrication.
The long-term success of an implant prosthesis depends not only on the development of osseointegration, but also on the maintenance of osseointegration after the prosthetic phase. To achieve this, a passive superstructure must be fabricated. Errors that result from the impression transfer method of implant position during the impression procedures often made it necessary to section and solder metal frameworks repeatedly. This article presents a modified impression technique intended to deal with the problems of more traditional impressions with the aim of achieving a more accurate master cast.
Dental Casting Technique↗
A procedure for reorienting a cast on a surveyor.
The tilt of a cast must be recorded so that it can be easily transmitted to the dental technician, who should then be able to transfer the original tilt from the master cast directly to any necessary duplicate casts. A procedure is presented that can easily record and transfer the tilt with the help of an impression made with a custom-made U-shaped universal tray.
Dental Impression Technique↗
Improved occlusal surface detail with the vacuum-formed matrix.
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Acrylic Resins↗
A quick method for boxing complete denture elastomeric impressions.
Rubber base impressions must be poured immediately for maximum accuracy. A method of boxing is presented that uses a previously formed thermoplastic box for pouring the complete denture rubber base impressions in a few minutes.
Dental Impression Technique↗
Surface properties and castability of elastomeric impression materials after plasma cleaning.
The wettability of impression materials is an important requirement for accurate reproduction of intraoral structures. The aims of this study were to evaluate the effect of plasma cleaning on critical surface tension and die stone castability of five silicone impression materials. Critical surface tension was calculated using a contact angle analysis according to Zisman (1964), before and after plasma cleaning. Die stone casts were produced from impressions of a master die and the area extension of the reproduction was measured planimetrically. The results showed a general increase in the critical surface tension and in the polar force component of the composite free energy for materials treated with plasma cleaning. An improvement in castability of all materials was also noted.
Analysis of Variance↗
An adaptive finite-element approach for the analysis of dental restorations.
The present paper deals with the problem of stresses generated during the setting process of polymer tooth fillings. A finite element procedure capable of accurately predicting the stresses along an interface between two different materials is presented. Adaptation of the finite element mesh is carried out based on a simple error estimator. The procedure is tested against benchmark problems and then applied to polymer tooth fillings. The results of the study are relevant in understanding and improving the behaviour of dental restorations.
Dental Cavity Preparation↗
Preparation of void-free casts from vinyl polysiloxane impressions.
PURPOSE: To investigate two techniques to produce void-free casts from vinyl polysiloxane impressions. MATERIALS AND METHODS: Thirty casts prepared using a conventional technique were compared with 30 casts prepared using a technique involving syringing of stone in terms of numbers of surface voids. RESULTS: Significantly fewer surface voids were observed in the casts prepared using syringing technique. CONCLUSION: The syringing technique investigated is considered to have advantages over the conventional technique for the production of casts from vinyl polysiloxane impressions.
Air↗
Dental rolls: a suitable model for practising tendon repair techniques.
Surgical training has changed significantly in the United Kingdom in last decade. A simulator for practising various tendon repairing techniques is presented. It has been designed for the use of junior trainees in Hand surgery dealing with the routine hand trauma cases and can be assembled quickly and cheaply.
Humans↗
Custom-made removable implant analogs for soft-tissue casts.
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Dental Implants↗
Tests of validity of indices of occlusion.
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Child↗
A novel method for the three-dimensional (3-D) analysis of orthodontic tooth movement-calculation of rotation about and translation along the finite helical axis.
The purpose of this study was to establish a novel method for evaluating orthodontic tooth movement in three-dimensional (3-D) space. The present system consisted of the following procedures at a given treatment period: (1) 3-D tooth positions were measured with a 3-D surface-scanning system using a slit laser beam; (2) the 3-D shape data were registered automatically at the maxillary first molars, and the coordinate systems were normalized; (3) the rotation matrix and translation vector were calculated from the automatic registration of the two position data for a given tooth; (4) the finite helical axes of teeth were calculated as the locus of zero rotational displacement; and (5) tooth movement was presented as rotation about and translation along the finite helical axis. To test this system, a male patient (age 22 yr 2 months) with Angle Class III malocclusion and moderate crowding of the anterior teeth, who had been treated using a standard multi-bracket appliance, was used as a model case in this study. Impressions for a dental cast model were taken at five phases; immediately before and after application of the appliance, and 10 days, 1 month and 2 months after beginning treatment. The results demonstrated that the present analytical method can more simply describe the movement of a given tooth by rotation about and translation along the finite helical axis, and provides quantitative visual 3-D information on complicated tooth movement during orthodontic treatment.
Adult↗