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PubMedDate not supplied

Some effects of disinfecting solutions on the properties of alginate impression material and dental stone.

The study investigated the effect of two disinfecting solutions on one brand of alginate impression material and dental stone. Control impressions were immersed in water for equivalent periods and the effect of storage of impressions after disinfection or control immersion in water was also investigated. There were no significant dimensional changes in impressions poured after one hour. All impressions stored for 16 hours before pouring showed significant dimensional changes. Mixing dental stone with one disinfectant caused a significant softening of the cast. It is strongly recommended that all impressions are thoroughly rinsed with water after disinfection to prevent incorporation of disinfectant in the cast.

Alginates↗
PubMed1988

Reversible hydrocolloid: the standard of excellence.

Reversible hydrocolloid is the oldest elastic dental impression material and, with the appropriate methodology, the advantages outweigh the disadvantages. Skill, care, and comprehension of the physical properties of the materials ensure success.

Agar↗
PubMed1990

Vinyl polysiloxane impression materials: a status report. Council on Dental Materials, Instruments, and Equipment.

Results of investigations of vinyl polysiloxanes indicate that they produce highly accurate impressions, have excellent elastic recovery, minimal permanent deformation, and adequate tear strength. A number of vinyl polysiloxanes are certified by the American Dental Association. All of these materials provide clinically acceptable results. Advantages of using the vinyl polysiloxanes include the ability of the impression to be poured up after 1 hour or 1 day, or for some products, after 1 week without significant loss of accuracy; the possibility of repouring the impression a second time and producing an accurate cast; the impression materials are available in several viscosities allowing flexibility in choosing an impression technique; and they can be immersed in recommended disinfectants without affecting the accuracy of the impression. The disadvantages of using the vinyl polysiloxanes include a difficulty in lengthening the working time of products without retarders and a high surface tension making it difficult to wet the impression when pouring up a stone cast. Hydrophilic materials appear to facilitate the casting of the impressions with stone. The automixing devices seem to provide convenience without sacrificing the quality of the impression and are currently available for several products. As with all elastomeric impression materials, proper handling is necessary to ensure the best results. The vinyl polysiloxanes seem to be an excellent choice of impression materials for many clinical situations.

American Dental Association↗
PubMed1982

Reproduction of details using dental stones and investment material in impressions of elastomers and waxes.

In the fabrication of crowns and inlays it is very important that all the details of the impression are exactly reproduced by the cast. These requirements prevail between elastomeric impression materials and dental stones as well as between waxes and investment materials. Inadequate filling of the details of the impression will result in rounded inner corners of the casting, which then may not properly seat on the prepared tooth. Two brands of elastomeric impression material, dental stone, wax, investment material and wetting agent were chosen to study the reproduction of details. A master model of stainless steel, shaped like a truncated cone with a convex top and 60 degrees threads, was used. The shape of this model made it possible to make microscopic measurements of the reproduced detail of the threads. No significant difference, by different prepouring treatment of the impressions was found in reproducing details with elastomeric impression materials and dental stones. All combinations of elastomeric impression materials and dental stones reproduced, however, significantly more details than combinations of waxes and investment materials. The relevance of transferring conclusions from the laboratory investigation to clinical conditions are discussed as well as the clinical value of reproducing details.

Calcium Sulfate↗
PubMed1996

Predictable impression procedures for complete dentures.

This article outlines those techniques and materials that will optimize the clinician's ability to obtain predictable complete denture impressions using the selected pressure philosophy. Fabrication of a custom tray is crucial to the ultimate outcome of exemplary impressions. Alternative methods for border molding the custom tray are presented.

Dental Impression Materials↗
PubMed1995

The effect of tray material and surface condition on the shear bond strength of impression materials.

This study compared the adhesive shear bond strength of three selected impression materials with that of thermoplastic and acrylic resin tray materials as a function of surface preparation. Polyether (Impregum), polyvinylsiloxane (Reprosil), and polysulfide (Permlastic) impression materials were evaluated on smooth, rough, and contaminated tray surfaces. Smooth surface samples were formed against glass and served as the control groups. Experimental groups consisted of samples contaminated with artificial saliva and rough surface samples that were abraded with 110 microns of Al203. A total of 126 samples were subdivided into 18 groups of seven specimens each. Each sample consisted of a 1 inch square, 3 mm thick mass of an impression material sandwiched between the prepared surfaces of a pair of resin plates. Each specimen was tested in a universal testing machine for adhesive shear bond strength. Data were analyzed with three-way analysis of variance and Scheffe's test. The results indicated that the thermoplastic resin material had better adhesive properties than the acrylic resin. For both tray materials mean adhesive shear bond strengths for Impregum and Reprosil were significantly greater than those of Permlastic. Tray surface contaminated with saliva decreased the adhesive shear strength at the tray adhesive impression interface.

Acrylic Resins↗
PubMed2002

Success with inlays/onlays: the seven essentials.

Direct restorative materials have revolutionized the industry over the last several years. They offer the convenience to the patient of a one-visit procedure and they decrease overhead in the dental practice. However, it is essential to remember that direct procedures are not always the treatment of choice. For this reason, we should not discount the need for--or the value of--indirect techniques and laboratory-based procedures, such as inlays and onlays. Fit, form, and function can be more predictable when a procedure involves the ultraprecise workings of the dental laboratory--if the impression-making and other focus areas are given their due significance. This article provides key information about and clinical tips for the seven main facets of inlay/onlay fabrications that will lead to clinical success: diagnosis, tooth preparation, tissue management, impression making, temporization, laboratory communications, and final fit/occlusion.

Cementation↗
PubMed1986

An investigation into the compatibility of some irreversible hydrocolloid impression materials and dental gypsum products. Part II. A refined discriminatory procedure.

Part I of this study considered the ability of alginate and gypsum combinations to reproduce a line on a test block. Part II describes a refined discriminatory procedure in the evaluation of the compatible combinations. Statistical analysis showed this procedure to be consistent, and that it could be expected to be repeatable. On the basis of this analysis, it was found that one alginate was clearly superior to all others, and that it was possible to distinguish a further group of combinations within the group that reproduced the 0.050 mm line. Surface treatment of the alginates by fixing solutions showed that none of the treated materials could be improved to the extent of equating them with the best of the naturally compatible combinations. It is recommended that manufacturers pay more strict adherence to the requirements of the ISO Standard with regard to the availability and recommendation of suitable compatible gypsum products, and also that perhaps the actual Standard should be modified to be more realistic in its demands, and more discriminatory in its evaluation procedure.

Alginates↗
PubMedDate not supplied

Materials for interocclusal records and their ability to reproduce a 3-dimensional jaw relationship.

PURPOSE: The purpose of this study was to determine if accuracy and dimensional stability of vinyl polysiloxanes and irreversible hydrocolloids stabilized by a tray used for fixed prosthodontics, removable partial, and complete denture cases are comparable to those of waxes and record rims and if storage time (24 hours or 6 days) affects dimensional stability of the tested materials. MATERIALS AND METHODS: Two waxes, two record rims, three vinyl polysiloxanes, and one irreversible hydrocolloid (alginate) were examined. Three pairs of master casts with measuring steel rods were mounted on an articulator (initial position). Five records were made of each material, and the upper cast was remounted after 24 hours or 6 days so that deviations from the initial position could be measured. RESULTS: Vinyl polysiloxanes reinforced by a stabilization tray were the most accurate materials able to reproduce a settled interocclusal position. Mounting casts (fixed prosthodontics cases) without records gave accuracy similar to wax records. Record rims used for removable partial and complete denture cases produced lesser accuracy than vinyl polysiloxanes and irreversible hydrocolloid stabilized by a tray. Accuracy was not significantly affected by storage time. CONCLUSION: The results show that accuracy of vinyl polysiloxanes and irreversible hydrocolloids reinforced by a tray is superior to that of record rims with regard to the complete denture case and is among the most accurate with regard to the removable partial denture case. For fixed prosthodontics, however, reinforcement is unnecessary.

Alginates↗
PubMed2002

The accuracy of dual-arch impressions: a pilot study.

STATEMENT OF PROBLEM: Dual-arch impression trays often are used for addition silicone final impressions of fixed prosthodontic preparations, but concerns about distortion of the impression are common because such trays lack rigidity. PURPOSE: This in vitro pilot study was designed to determine the accuracy of addition silicone impressions made with custom trays or made with either passive or stressed dual-arch trays. MATERIAL AND METHODS: Complete crown preparations of a mandibular molar, premolar, and incisor were made on a dentoform. These tooth preparations received flat, parallel indexes on the facial and lingual axial walls for accurate and reproducible positioning of a digital caliper. Gypsum dies were produced with an addition silicone impression material in either custom trays or dual-arch trays seated passively or with induced flexure (3 dies per tray group). The facio-lingual dimensions of the dies were measured with a digital caliper accurate to +/-5 microm and compared to the dimensions of the original preparations. Flexure in the latter group was induced by contact of the tray with a simulated torus, made of resin, in the lingual vestibule of the dentoform. Data were analyzed with 2-way analysis of variance and Tukey's multiple comparison test (alpha=.05). RESULTS: Dies fabricated with either the custom or passive dual-arch tray reproduced the facio-lingual dimensions of the preparations within a -27 to +13 microm range. Dies fabricated with the flexed dual-arch tray exhibited greater discrepancy, in the range of -47 to -67 microm relative to the preparations. Tray type was a significant factor (P=.002): the flexed tray group was significantly different than the other 2 groups, which did not differ from each other. CONCLUSION: Within the limitations of this pilot study, dual-arch impressions were comparable in accuracy to impressions made with custom trays. Accuracy was reduced, however, when the trays were flexed during closure of the arches.

Acrylic Resins↗
PubMed2003

Accuracy of open tray implant impressions: an in vitro comparison of stock versus custom trays.

STATEMENT OF PROBLEM: The accuracy of an implant fixture-level impression is affected by the type of impression tray used. PURPOSE: The purpose of this in vitro study was to investigate the accuracy of open tray implant impressions comparing polycarbonate stock impression trays and rigid custom-made impression trays to make implant fixture-level impressions. MATERIAL AND METHODS: Gold cylinder pairs, splinted by gold bars (reference frameworks) were constructed on an aluminum typodont. Polyether impressions were made of 2 pairs of Brånemark 3.75-mm diameter fixtures mounted in an aluminium typodont, with 3 stock impression trays, 3 close-fit custom trays, and 3 spaced custom impression trays, by use of an open tray technique. The casts produced were assessed for accuracy by attaching the reference frameworks with alternate single screws and measuring the vertical fit discrepancy of these reference frameworks to the analogs within the working cast using a traveling microscope. Comparison of gap dimensions by tray type was performed with a nonparametric Kruskal-Wallis analysis of variance (ANOVA) followed by pair-wise Mann-Whitney U tests. To adjust for multiple comparisons in the post-ANOVA contrasts (P<.02). Comparison of gap dimensions between anterior and posterior regions were performed with Mann-Whitney U tests (P <.05). RESULTS: The results showed that the mean fit accuracy, as measured by vertical fit discrepancy, of casts from the stock trays (23 +/- 20 microm) were statistically significantly less (P<.001) than the spaced custom trays (12 +/- 10 microm) or close fit custom trays (11 +/- 10 microm). The difference in median gap size for analogs with a 20-mm separation was 10 microm. CONCLUSION: Within the limits of this in vitro study, rigid custom trays produced significantly more accurate impressions than the polycarbonate stock trays. The stock trays used in this study could not produce accurate impressions consistently. For analogs with a 20-mm separation, there was a difference in medians of 10 microm in accuracy between the stock and custom trays.

Analysis of Variance↗