PubMed · 399397
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
D A Orkin. 1979. The endodontically treated tooth.. https://pubmed.ncbi.nlm.nih.gov/399397/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
This study determined the accuracy of fit of three-unit fixed partial dentures joined by an infrared soldering technique compared with one-piece fixed partial denture castings and individually cast crowns. Wax patterns of prepared Ivorine teeth, maxillary left central incisor and maxillary left canine, were injection molded; a plastic rod was used as a pontic. One group of patterns was cast as one-piece dentures; the other group was sectioned in the connector area, cast individually and then joined by infrared soldering. Castings were seated on their respective dies, embedded in epoxy resin, and sectioned. Gap distances between the casting and the die were measured at specified marginal sites with a profile projector. Results showed that the fit of infrared-soldered fixed partial dentures was significantly better than that of one-piece castings and was comparable with the fit of single crowns. The gap openings measured in all castings were within the range of clinical acceptability.
Recent studies have described microleakage under full crowns cemented with several different cements. This study tested three different types of crown margin preparations--a chamfer, a shoulder, and a shoulder plus a bevel to determine whether or not the margin preparation could affect microleakage. All crowns were cemented with zinc phosphate cement. The crowns were tested for leakage in thermocycled dye. All crowns demonstrated significant leakage following the path of the dentinal tubules into the pulp. This could possibly be one of the causes of pulpal inflammation and even pulpal death under full crowns.
PURPOSE: This study compared the stress distribution of three porcelain-fused-to-metal labial margins on a central incisor under simulated occlusal force. MATERIALS AND METHODS: The margin designs were rounded-shoulder, rounded-shoulder with a bevel, and a chamfer. RESULTS: Evaluation of mean equivalent Mises tensile stress did not show any difference at the cement-dentin and metal-cement interfaces of the three margins. The mean equivalent Mises tensile stress at the porcelain-metal interface was found to be significantly higher for rounded-shoulder when compared with the chamfer. There was no significant difference in the axial stresses along the three interfaces among the three margin designs. Statistically significant differences in radial stresses at some interfaces of the three margin designs were found. CONCLUSION: The change of cement thickness of the chamfer margin is significantly greater than that of either the rounded-shoulder or the bevelled-shoulder margin.