Charles M. Belting

Inherent structural defects of porcelain-fused-to-gold restorations: A preliminary report

kJ reation of esthetic restorations is a problem constantly confronted by dentists. Porcelain was introduced inany years ago as a solution to this problem and has appeared in dental restorations via myriad combinations and techniques. The Kichmond crown, for example, employed a porcelain facing swaged to a backing, subsequently soldered to form a gold lingual surface. These apparent solutions left mud1 to be desired, as did many “revolutionary” concepts for porcelain and gold restorations. The complete porcelain jacket (veneer) crown is one which became very popular and which is still used fairly extensively. The susceptibility of complete porcelain veneer crowns to fracture has led to development of porcelain-fused-togold restorations, which combine the physical properties of a gold alloy with the esthetic qualities of porcelain. Although this restoration is a solution to most of the problems, there are still some others to be solved. We will attempt to discover SOI~E of the causes for these failures. Manufacturers, as well as reports in the dental literature, make extensive claiuis regarding strength, bonding qualities, and esthetics of porcelain-fused-to-gold restorations. Most extant techniques stipulate specific brands and combinations of metal and porcelain to obtain optimum results. It is generally implied, and often directly stated, that a match in expansion and contraction coefficients of porcelain and gold precludes any substantial residual stresses in a finished crown. However, expansion coefficients match at only one temperature (approximately 700’ to 800” F.) , and a mismatch exists at all other temperatures. Resultant interface stresses have been demonstrated by Tuccillo and NielsenI, 2 These interface stresses may result in some of the weaknesses and adaptation failures which sometimes appear clinically.

The influence of extraction and replacement of teeth on hearing

Abstract Hearing thresholds were measured on a group of patients prior to the extraction of teeth and again at three-day, one-month, and two-month intervals following the extraction of their teeth. Subsequent to the insertion of complete dentures, threshold measurements also were made at 3-day, 1-month, and 2-month intervals. Tests indicated: (1) a slight, but consistent, improvement in hearing acuity at all frequencies following the complete removal of teeth, (2) a significant improvement of pre-existing hearing impairments at the higher frequencies following the replacement of missing teeth with complete dentures, and (3) that decibel measurements of the right and left ears of each individual did not differ significantly.