Prosthetic laboratory influence on the vertical misfit at the implant/UCLA abutment interface.
(25/91)
An inadequate fit at the abutment/implant interface can generate mechanical and biological problems. The laboratorial stages could induce misfit in such interface when the castable UCLA abutment type is used. The purpose of this study was to comparatively evaluate the performance of three prosthetic laboratories (Labs A, B and C) by vertical fit analysis of castable UCLA abutments on the casting and soldering stages of the same prosthesis. Four fixed prostheses were built by each laboratory using castable UCLA abutments. The evaluation was made by scanning electron microscopy under 500x magnification in the mesial and distal regions of each element of the prosthesis, totalizing 24 measurements per laboratory. The results were analyzed statistically by Kruskal-Wallis test (p<0.05). In the casting process, the values presented by the laboratories differed significantly to each other (p=0.004). After soldering, the values presented by the laboratories showed no significant difference (p=0.948). It may be concluded that the fit values obtained in the casting stage of UCLA abutments can be influenced when processed by different laboratories, and that conventional soldering itself increased the degree of framework misfit, regardless of which laboratory made it. (+info)
In vitro antimicrobial activity of irreversible hydrocolloid impressions against 12 oral microorganisms.
(26/91)
This study evaluated in vitro the antimicrobial activity of irreversible hydrocolloids (one containing an antimicrobial agent) prepared with water or with a 0.2% chlorhexidine digluconate solution against 12 strains of the oral microbiota. Twenty specimens (0.5x1.0 cm) for each group (1. Jeltrate mixed with water; 2. Jeltrate mixed with 0.2% chlorhexidine digluconate solution; 3. Greengel mixed with water; 4. Greengel mixed with 0.2% chlorhexidine digluconate solution) were prepared under sterile conditions and placed in culture media inoculated with the indicator strains. After incubation in aerobiosis or microaerophilia, inhibition of the microbial growth was measured and the results were interpreted. The normal adherence curve revealed a non-normal distribution of the data, so the non-parametric Friedman Test was performed (p<0.05). The antimicrobial activity of the groups was classified in the following order: 1, 3, 4, and 2. The results suggest that the method of preparing irreversible hydrocolloids with a 0.2% digluconate chlorhexidine solution is more effective than the incorporation of an antimicrobial agent in the powder to reduce cross-contamination caused by impressions. (+info)
Antibacterial and antifungal properties of polyether impression materials.
(27/91)
The aim of this study was to evaluate the antibacterial and antifungal properties of polyether impression materials using the agar diffusion test. Three different types of polyether impression materials (P2, Penta Soft and Penta) were tested to determine their ability to inhibit the growth of Enterococcus faecalis, Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. The areas of inhibition zones were measured visually with a 0.1-mm incremental Boley gauge. In all groups, none of the samples of the P2 polyether impression material exhibited antibacterial or antifungal activity against any of the microorganisms. All Penta Soft and Penta samples exhibited antibacterial activity against E. faecalis and S. aureus, and only Penta samples exhibited antifungal effect against C. albicans, which decreased progressively as the setting time of the material increased. (+info)
A study on measuring occlusal contact area using silicone impression materials: an application of this method to the bite force measurement system using the pressure-sensitive sheet.
(28/91)
The aim of this study was to establish an objective and quantitative method of measuring occlusal contact areas. To this end, bite records were taken with a silicone impression material and a light transmission device was used to read the silicone impression material. To examine the effectiveness of this novel method, the occlusal contact area of the silicone impression material and its thickness limit of readable range were measured. Results of this study suggested that easy and highly accurate measurements of occlusal contact area could be obtained by selecting an optimal applied voltage of the light transmission device and an appropriate color of the silicone impression material. (+info)
Marginal and internal fit of all-ceramic crowns fabricated with two different CAD/CAM systems.
(29/91)
This study evaluated the accuracy of marginal and internal fit between the all-ceramic crowns manufactured by a conventional double-layer computer-aided design/computer-aided manufacturing (CAD/CAM) system and a single-layer system. Ten standardized crowns were fabricated from each of these two systems: conventional double-layer CAD/CAM system (Procera) and a single-layer system (Cerec 3D). The copings and completed crowns were seated on the abutments by a special device that facilitated uniform loading, and the marginal discrepancies were measured. Internal gaps were also measured using a low-viscosity silicone material. Marginal discrepancies of Procera copings were significantly smaller than those of Procera crowns and Cerec 3D crowns (p < 0.05), but Procera crowns and Cerec 3D crowns did not differ significantly from each other (p > 0.05). On internal gaps, Cerec 3D crowns showed significantly larger internal gaps than Procera copings and crowns (p < 0.05). Within the limitations of this study, the single-layer system demonstrated acceptable marginal and internal fit. (+info)
A study to determine whether the anterior and posterior vibrating lines can be distinguished as two separate lines of flexion by unbiased observers: a pilot study.
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CONTEXT: By convention, the posterior palatal seal area is located on the palate between the anterior and posterior vibrating lines. However, there are opposing views on whether the anterior and posterior vibrating lines can be distinguished as two separate lines of flexion. AIMS: The study was carried out to determine whether the anterior and posterior vibrating lines can be distinguished as two separate lines of flexion by unbiased observers. A second part of the study was formulated to evaluate whether the palpatory method correlated with the nose-blowing method in locating the anterior line of flexion. MATERIALS AND METHODS: Twenty-three dental undergraduate clinical students were selected as observers. Twenty-three edentulous patients were randomly selected. The students were asked to record the anterior and posterior vibrating line on one patient each using two differently colored marking pencils. Also, the anterior vibrating line was marked by the palpatory method (using T burnisher) using a third colored marking pencil. The marked lines were then transferred onto the previously made impression of modeling plastic. RESULTS: Of the 23 recorders used in the study, 19 could locate separate anterior and posterior lines of flexion. In 4 cases, the anterior and posterior lines of flexion coincided and were not distinct. In 20 cases, the palpatory method produced a line anterior to the line located by the Valsalva maneuver. CONCLUSIONS: The anterior and posterior vibrating lines could be located by the undergraduate students as two separate lines of flexion when the appropriate action was elicited for each of them; and the palpatory method produced a line slightly anterior to the anterior vibrating line located by the Valsalva maneuver. (+info)
Effect of conventional and experimental gingival retraction solutions on the tensile strength and inhibition of polymerization of four types of impression materials.
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