The International Journal of Prosthodontics, 01/1993

There is an increasing awareness of the importance of cross-infection control in dental clinics and laboratories. This study evaluates the effects of various disinfecting solutions on the surface hardness of an acrylic resin denture base material. Hardness was measured as resistance to indentation following the method specified by the British Standards Institute. The results demonstrated that immersion of denture base acrylic resin in disinfecting solution for up to 24 hours resulted in no significant effect on hardness values.

This paper describes a laboratory procedure lot use in periodontal and implant prostheses wherein an artificial removable gingiva, which reproduces the patient's gingival architecture, is fabricated on the working cast. This procedure allows the technician to achieve better crown contour and cervical adaptation of the prosthesis and facilitates ceramic procedures.

Influence of the Dimensions of Implant Superstructure on Peri-Implant Bone Loss

Previous studies on the fit of complete crowns have neglected to assess the internal adaptation of castings prior to cementation. Theoretical arguments and laboratory studies have failed to clarify which is the most desirable finish-line configuration in terms of marginal fit. This study evaluated axial and marginal fit of crowns made for three tooth preparations that had different labial finish-line configurations: shoulder, shoulder-bevel, and chamfer. The crowns were not cemented, but were sectioned and examined on their respective dies. There were no significant differences (P ? .05) among groups for marginal or axial gaps. Crown fit was not influenced by any of the three finish lines tested, and castings with well-fitting margins exhibited measurable axial wall space.

As a result of desiccation, conventionally prepared fresh dental specimens, examined with the scanning electron microscope (SEM), exhibit obvious artifactual effects that may include one or more of the following: distortion, fracture, separation of structures, and chemical interactions. Cryo-SEM techniques reduce or eliminate these artifacts and present reliable images while requiring less time to perform than do conventional methods.

This investigation examined the influence of the fabrication technique on the marginal fit of porcelain veneers. Ceramic veneer restorations were made with both feldspathic porcelain and cast glass ceramic materials for the labial surface of a maxillary central incisor. The feldspathic porcelain veneers were made by using both the platinum foil and refractory die techniques, and the cast ceramic veneers were fabricated in thicknesses of 0.5 mm and 1.0 mm. The fit of each veneer was measured before and after sectioning. The marginal openings for the intact veneers increased in the following order: platinum foil, refractory die, cast ceramic (0.5 mm), and cast ceramic (1.0 mm). A similar trend was observed for the sectioned specimens where the technique of fabrication (P .001) and the site of measurement (P .05) were found to have a significant effect on the fit of the veneers.

This study examined the effect of a soft denture liner on the distribution of stresses in the denture-supporting structures, Dentures without a liner and with three configurations of a soft liner were simulated by using a two-dimensional viscoelastic finite-element stress analysis. The stress intensity at functional force-bearing stress decreased when a soft denture liner was used. However, the stresses in the bone increased remarkably up to 3.0 seconds after leading Because of the time-dependent effect of stresses applied to soft denture liners, denture patients who clench or brux may not benefit as greatly from soft denture liners. The study indicates that viscoelastic finite-element analysis is helpful for evaluating soft denture liners. Soft denture liners appear to be useful for improving the stress distribution in the supporting structures under dentures.

Whenever possible, the minor connector of a removable partial denture is located in the interdental embrasure. Recent evidence suggests that gingival attachment loss is more probable on the proximal aspect, thus minor connectors located in embrasures cover susceptible sites. A rationale and design are presented for locating the minor con hector on the lingual aspect of the abutment tooth rather than in the interproximal area.

The tensile bond strength of Panavia EX to a high-noble alloy prepared by abrasive spraying and tin plating was measured Two different intraoperatory tin plating systems were compared. Disk-shaped specimens were cast in type III gold, abrasive sprayed with aluminum oxide, and divided into three groups of 30 specimens each. Specimens in one group were tin plated by using a Kura Ace Mini unit, those in the second group were tin plated by using a Micro Tin unit, and those in the third group were not tin plated and served as the control group. Disks within each group were luted to each other with Panavia EX. The specimens were thermocycled and tested in tension. There was no significant difference between the two tin plated groups; however, the luting bond of both experimental groups was significantly stronger than was that of the control (P .05).

The diametral strengths of magnesia-core crowns made with different body porcelains, Will-Ceram, Crystar, Ceramco II, and Vita VMK 68, were measured. The results were compared to the diametral strengths of aluminous-core crowns and Renaissance crowns. A one-way analysis of variance showed that there were no significant differences in the strengths of magnesia-core crowns or the aluminous-core crowns, but the Renaissance crown strengths were significantly lower.

This article describes a technique for fabricating interlocking custom tracheostoma vents for use in patients with bidirectional tracheostomas or tracheostoma fistulas secondary to tracheostenosis. The interlocking nature of the tracheostoma vents allows easy placement and removal from a tracheostoma or tracheostoma fistulas that would not be possible with a single tracheostoma vent A 5 x 10-mm opening in the inferior portion of the prosthesis allows the patient with intact vocal cords to phonate by occluding the opening of the prosthesis and forcing air through the prosthesis into the subglottal area. The rigid acrylic resin of the prosthesis maintains the patency of the tracheostoma or tracheostoma fistula while a resilient material in the peristomal area reduces the pressure and potential irritation. The steps involved in the fabrication of the dual interlocking custom tracheostoma vents are easy and require no elaborate laboratory equipment.