Gunnar Ryge

Reprint of Criteria for the clinical evaluation of dental restorative materials

Rating scales were developed for several factors that were considered relevant to the problem of clinically evaluating dental restorative materials. Examiners were trained to use the rating scales, and their performance was evaluated in field trials. Data analysis of examiner performance was used to revise the written criteria, and to train the examiners in making consistent judgments of dental restorations. Criteria were adopted when field testing indicated that examiners were able to duplicate their own judgments and judgments of other examiners at a predetermined level of acceptability. Further experience with the rating scales in actual clinical studies led to the consolidation of anterior and posterior criteria, which had been developed separately, and to the deletion of certain rating scales which failed to yield useful information. The rating scales which were finally adopted are for color match, cavo-survace marginal discoloration, anatomic form, marginal adaptation, and caries.

Studies on Dental Aerobiology: I. Bacterial Aerosols Generated during Dental Procedures:

A controlled environment operatory and specially designed human aerosol test chamber were used to study characteristics of bacterial aerosols generated from a patients mouth during dental procedures and by common naso-oral activities. Some dental procedures generated aerosols with bacterial concentrations that exceeded those produced during coughing or sneezing and that were considered potential health hazards.

Studies on Dental Aerobiology: IV. Bacterial Contamination of Water Delivered by Dental Units

Water sprays from a dental handpiece and air-water syringe were evaluated for bacterial content. Bacterial concentrations that far exceeded limits permissible for public water supplies were observed. A simple method for reducing bacterial contamination in water lines for dental equipment is presented.

Quality of extensive fixed prosthodontics after five years

A group of 150 patients who had received extensive restorative treatment 5 years prior to this study was selected at random from the Swedish Dental Insurance System records in Malmo. Of the 133 respondents to a questionnaire, 109 participated in a clinical evaluation of 891 restorations including 498 crowns, 232 pontics, 6 removable partial dentures, and 155 adjacent or opposing metallic restorations. The clinical evaluation was performed by two trained examiners by means of the CDA quality evaluation for dental care. Ninety percent of the crowns and pontics, 80% of the adjacent or opposing metallic restorations, and all six partial dentures were rated satisfactory. Twenty-three percent of the crowns, 49% of the pontics, 17% of the adjacent or opposing restorations, and half the partial dentures rated in the range of excellence. Not acceptable ratings for crowns included 3.4% T ratings and 6.6% V ratings. For pontics, the corresponding percents were 9.5% and 0.4%, respectively. T ratings were in most cases indicative of overcontouring, whereas V ratings for crowns were usually given because of secondary caries. Marginal periodontitis was mainly associated with not acceptable ratings but was also observed in connection with satisfactory restorations. Only 2% of the restorations had been lost during the 5-year period after insertion.

Studies on Dental Aerobiology: II. Microbial Splatter Discharged from the Oral Cavity of Dental Patients

The distribution and bacterial content of splatter particles emanating from a patients mouth during dental procedures was studied in a controlled environment operatory. Levels of contamination far exceeding those produced by common oral activities were observed. Suction and preoperative oral hygiene procedures are not effective in reducing contamination from bacterial splatters, and the modification of certain procedures and the use of protective shields or glasses is advised.

Study of Bond Strength of Dental Porcelain Fused to Metal

SYNOPSIS IN INTERLINGUA UN STUDIO DEL FORTIA ADHESIVE DE PORCELLANA DENTAL FUSIONATE A METALLO.-Pro evalutar le effecto del atmosphera in le furno super le fortia ligatori, 12 specimens pro tests del fortia tensil de metallo describite in Specification No. 14 del ADA esseva preparate con un strato uniforme de material ceramic fusionate al barra. In 3 del specimens le material ceramic esseva fusionate in aere, in 3 in un vacuo, in 3 in oxygeno, e in 3 le nude metallo passava a transverso le cyclo de ignition. Le specimens manipulate sub oxygeno produceva le plus alte valores de fortia ligatori, e le specimens manipulate in vacuo produceva le valores le plus basse.

Hardening of High-Fusing Gold Alloys

SYNOPSIS IN INTERLINGUA INDURAMENTO DE ALLIGATOS DE AURO A ELEVATE PUNCTO DE FUSION.—Esseva studiate le effecto indurante producite per le addition systematic de metallos vil (ferro, stanno, e indium) a alligatos de auro e palladium e de auro e platinum. Funditos specimen de iste alligatos esseva subjicite a duo cyclos de tractamento thermal: (1) refrigidation ab 1800 F (= 1060 C) e (2) invetulation ante le frigidation, durante 30 minutas a un serie de temperaturas inter 850 e 1600 F (=450 e 870 C). Le valores de duressa Brinell esseva registrate, e le microstructura esseva studiate post le tractamento thermal. Le addition del metallos vil al alligatos de auro e platinum (sed non de auro e palladium) resultava in un augmento significative del duressa in le condition invetulate. Evidentia de un precipitation o de un formation subgranular esseva obtenite in omne le systemas de auro e platinum in condition hyper-inventulate.

The contour meter: An apparatus for comparison of mucosal surface contour of impressions, models, and dentures

Abstract The contour meter is described, and problems in connection with the positioning procedure and the correction factors for recording of points on inclined surfaces are discussed. Experimental errors affecting the reproducibility of recordings have been studied, and limits of accuracy for the contour meter are given.

Diagnostic significance of intratissue contrast in bitewing radiographs

Abstract A double-blind means of quantitating the ability of dentists to recognize proximal radiolucencies in bitewing radiographs has been employed to test the hypothesis that the diagnostic quality of bitewing radiographs is maximized when the contrast, or density gradient registered within the image of dental enamel, is maximized. The data confirm independent predictions based on this hypothesis and emphasize the significance of contrast when assessing the diagnostic potential of any radiographic procedure in which subtle changes must be detected within a single tissue.

Contact angles of drops of enamels on metals

A LTHOTJGH the area of enamel-metal dental restorations has seen the introduction of several new materials in the past ten years, relatively little has been published concerning their nature and properties. l-13 Generally, an enamel-metal system in dentistry consists of a vitreous material that is fused to a gold-platinum casting to produce veneered crowns, jacket crowns, and fixed partial dentures. An important aspect of this system is the adhesion between the enamel and the metal structure ; without true adhesion, the restoration will fail. Adhesion depends upon several factors, but the most important of these is the degree of attraction between the elementary particles of the enamel and the metal. Mechanical tests have been applied to test the strength of the interface between the enamel and metal. Shell and Nielsen1 applied a pull-through shear test, and Custer, Asgar, and Peyton2 employed a beam test for bond strength. O’brien and Ryge3 have reported on the wetting forces between one molten enamel and several materials. Substances have been suggested that are called “bonding agents” to be used in joining these enamels and metals. Although complete information is not available, these “bonding agents” contain compounds or colloidal dispersions of gold in an organic base. Manufacturers recommend that the metal to receive the enamel be coated with a layer of such a material and fired. During the firing operation, a layer of gold is deposited on the surface of the alloy. It was the purpose of this study to determine the degree of wetting by contact angle measurements between several commercial enamels and various metals. These data, in addition to other information, may be used to estimate the strength of the wetting forces involved in the .adhesion between these materials.