Cast Gold Crowns Research Articles

The Effect of Thermal Stress on the Marginal Seal of Cast Gold Full Crowns

An experiment was conducted to observe the effect of fluctuations in temperature on the marginal seal of full veneer cast gold crowns. Forty crowns were fabricated and allotted into two groups of 20 crowns each. One group was cemented with zinc phosphate and the other group, with zinc polycarboxylate cement. Ten crowns from each group were subjected to thermal stress of fluctuating temperatures (4 and 60 C) and the remaining ten crowns from each group were held at the constant temperature of 37 +/- 1 C. The experiment demonstrated the following results: --Microleakage was evident in all groups. --The degree of microleakage with zinc phosphate was less than with zinc polycarboxylate cement. --Contrary to the claim that zinc polycarboxylate cement adheres to enamel through chelation, we were unable to observe better results. The degree of penetration of dye in the tooth-cement interfaces of crowns cemented with zinc polycarboxylate was not less despite the remaining layers of enamel for bonding. The cause of microleakage with cast gold restorations is apparently multifactorial. Research should formulate a luting agent which forms a strong bond to gold alloy and tooth substrate and has a high tensile and shearing strength.

Removal time: a factor in the accuracy of irreversible hydrocolloid impressions

Controversy exists regarding the correct time of removal of an alginate impression from the mouth. To investigate the effect of time of removal on accuracy, a series of alginate impressions were made of the lower left quadrant of a subject having a cast gold crown with four reference marks on tooth no. 19. The impressions were removed from the mouth at 1-5, 2, 3, 4-5 and 7 min after the insertion of the tray. Accuracy of the impressions was assessed by comparing the distances between the reference marks in stone casts with standard measurements taken from the gold crown prior to cementation. Impressions removed at 1-5 and 7 min produced the greatest distortions buccolingually. For the mesio-distal lengths all time intervals produced casts which were larger than the standard. The reasons for these findings are discussed and possible explanations are presented.

冠装着後の実験的歯周炎に関する基礎的研究

This investigation was carried out to determine whether the cast gold crowns with different locations of the cervical margin cause or are associated with a marked difference in the periodontal conditions. The cervical position of each crown was built up according to the following system: 1) 1mm above, 2) even with and 3) 0.5mm below the gingival margin.Thirty-two teeth in 4 adult dogs were examined. The gingival state and oral hygiene were recorded according to the index systems (Loe, 1967). Pocket depths were calculated. The gingival exudate measurements had been also assessed using the orifice method (Egelberg et al, 1973).The animals were sacrificed at time intervals of 2, 4 and 16 weeks following the placement of the crowns. The blood vessel topography at the dento-gingival junction was studied, after perfusion with a carbon-gelatin mixture prior to the sacrifice (Egelberg, 1966). Bucco-lingual and horizontal serial sections 8 microns thick were made and stained with hematoxylin and eosin. The gingivae adjacent to the crowns were observed microscopically. The morphologic changes are described, based upon the clinical, the cellular inflammatory and the epithelial changes.The results indicate that in areas with crown margin below the gingival crest, more severe gingivitis was registered than in the another areas examined.

Histologic evaluation of vitreous carbon endosteal implants in occlusion in dogs.

A 6-7 month histologic study of vitreous carbon endosteal implants in occlusion was conducted in dogs to determine whether the shape of the implant has adverse effects on supporting tissues. Conical vitreous carbon implants were placed in fresh, second, and third premolar extraction sites, and the sites were allowed to heal for periods of 2 to 8 weeks prior to restoration with cast gold crowns. Gingival tissues healed routinely and showed inflammatory conditions similar to tissues adjacent to teeth, and normal sulculur depths were measured. Bone formation was observed within grooves in the implant surface, providing retention and stabilization, normal bone remodeling appeared to be occurring adjacent to the implant sites. No inflammatory responses, foreign body reactions, or infections were observed. Vitreous carbon appears well suited for application as an endosteal implant material.

Predictability of retentive values of dental cements

Four types of permanent cements were used to determine whether the laboratory tests of compressive and tensile strength were predictive of their retentive abilities when retaining cast gold crowns to natural teeth. The standard laboratory test for film thickness also was compared to the degree of nonseating of these cast restorations. The laboratory tests of compressive and tensile strength are not predictive of retentive ability when considering cements which have differing potentials for reacting with or on the tooth surface. The calculated film thicknesses on the axial walls of the cemented restorations in this study were of the same order of magnitude as those values in the laboratory tests. However, the degree and variance of nonseating of the clinical crowns were considerably greater.

Contouring abutment teeth with cast gold inlays for removable partial dentures

Although cast gold crown restorations are most often indicated for abutments in removable partial denture construction, certain conditions are more practically approached with cast gold inlays. The preparation must be designed to provide maximum retention for the inlay, while adequate protection of the abutment tooth and of the supporting structures is maintained.

Solving the problems of cementing the full veneer cast gold crown

Tests were performed to indicate the accuracy with which full crowns can be cemented on prepared teeth. Findings indicated that using both internal relief for cement, plus a vent for escape of cement permitted a minimal gingival discrepancy following cementation. This discrepancy may be compensated for by constructing the crown with a slight gingival overlap properly contoured and polished. A simple technique for venting, fabricating a prefitted pin, and the procedure for permanent sealing of the escape-way vent within the normal interim period of cementation was described.

Clinical comparison of cast gold crowns with acrylic and with fused porcelain veneer facings

Widespread use of the acrylic veneer crown in the past has been the result of the relatively simple fabricating technic required, the initial esthetic qualities of the material, and lack of a better mate­ rial. The porcelain veneer crown, in which porcelain is fused to gold, repre­ sents a step in the right direction. Fused porcelain is more esthetic than acrylic resin; it is more permanent and more resistant to wear. Both acrylic and por­ celain facings are difficult to repair.

Construction of cast-gold crowns and fixed partial dentures by use of gold bands

A procedure is described which permits the appearance, fit, occlusion, and proximal contacts of crowns to be checked accurately prior to casting. This technique eliminates the complicated systems of recording jaw relationships and using copper-tube impressions and transfer copings. This method enables the dentist to carry out his own laboratory procedures satisfactorily.

Pits on inner surfaces of cast gold crowns

A total of over 500 castings were made with the hygroscopic water-added technique. In these castings studies were made of the sprue gauge, length, and direction, single or double sprues, pressure of casting machine, amount of gold, and flaring of the sprues as they affect the appearance of pits and voids on the inner surface of gold crowns. It was found that, in general, pits and voids would appear more often in bicuspid full crowns than in other types of single castings. Increasing the casting pressure, amount of gold, and sprue diameter (up to a certain point) and employing proper sprue direction and length tend to reduce the number or eliminate completely these pits. Flaring of the sprue is as important as any other factor just mentioned. Flaring of the sprue may act in the same way as placing a small reservoir very close to the wax pattern, and/or it may facilitate the flow of molten gold into the cavity. In either case it will help to eliminate some of the pits and voids that appear on the inner surface of gold castings. Since this laboratory study was made, extensive clinical experience in the University of Michigan, School of Dentistry clinic, by junior and senior dental students, gives further support to the results obtained from this investigation.

Increasing the vertical dimension of occlusion

A procedure for creating a balanced occlusion with cast gold crowns has been described. The procedure has several advantages. 1. When the gold skeleton crowns have been placed in the mouth and centric relation has been obtained, it is equivalent to having located the anatomic hinge axis of the mandible accurately. There is no fear that an error will develop when it is transferred to the articulator. 2. When the interfering spots on the gold skeleton crowns have been ground so the anterior teeth can come into edge to edge contact in right and left and forward mandibular positions, the dictates of the jaw movements have been carried out, and the precise degree of the vertical opening necessary has been established. 3. If there is a functional irregularity on one or both sides, the physiologic movement (including the Bennett movement) will have been accounted for because the data was obtained in the mouth which is the perfect articulator—the one no man can duplicate. 4. When the voids in the occlusal surfaces of the gold skeleton castings are filled with casting wax and chewed in, the small spines that jut into the voids permit the maintenance of the steepness of cusps and facilitate the final carvings of the occlusal surfaces when removed from the mouth. When the gold occlusal surfaces are cast directly to the gold skeleton crowns, the crowns are completed, as is the problem of the increase of the vertical dimension of occlusion. It is to be hoped that the simplicity of this method will be a stimulant for the practice of a much neglected phase of dentistry.

Porcelain veneers fused to cast gold crowns

Porcelain veneers fused to cast gold crowns

A study of adaptation of veneers to cast gold crowns

The adaptation of various veneer materials to gold was compared by studying the penetration of radioisotopes between the veneers and the cast gold crown. The veneer materials evaluated were silicate, acrylic resin, porcelain cemented with zinc phosphate cement, and 2 baked-on porcelain techniques. By this test, the porcelain materials fused to the gold, particularly when fired in air, appeared to be quite superior to the other materials studied. Even though the adaptation of these materials is reduced when they are fired in vacuum, the rate and degree of infiltration was markedly less than with the acrylic resins, cemented porcelain, or silicate veneers.

The acrylic-faced cast gold crown

Because of the adaptability of acrylic material, its application has been vastly broadened, particularly in its use as a processed facing in the anterior cast gold crown. A method has been outlined to provide adequate and safe retention of the acrylic in the window of a cast gold crown. New techniques have been offered to assure improved esthetic results by: (1) the use of oxyphosphate of zinc cement powder mixed with acrylic powder as a masking material; (2) the introduction of flash gold-plating hard cast alloys to provide a suitable color reflection background for the translucent acrylic material. Variation of the gold background can supply a range of colors by reproducing a gray, yellow, or red modification of any set of acrylic powders used. The opaque medium of cement furnishes a guide for the roentgenographic interpretation of acrylic margin in relation to tooth structure. Technical difficulties inherent in the finishing and cementation procedures have been discussed. The need for understanding and clarifying the vulnerability of this material, in regard to the daily routine of tooth brushing as well as abnormal tooth habits, has been stressed.

An Esthetic Three Quarter Veneer Crown: Modification of Standard Technic

Th e three quarter veneer gold crown is recommended particularly in the construction of anterior restorations used as crown and bridge retainers, where appearance as well as maximum reten­ tion is a major consideration. The pur­ pose of this article is to describe a new approach to this type of preparation. The retention attained by the use of the three quarter veneer gold crown is com­ parable to that of a full cast crown, pro­ vided there is sufficient natural tooth structure remaining so that the proper preparation can be developed. The abutment in question must have enough tooth structure to permit the de­ velopment of proximal grooves of ade­ quate length as well as of proximal re­ tentive walls and planes of adequate depth to assure stability. Experience and judgment are essential in order to de­ termine whether the retentive walls are of sufficient strength to resist the forces which tend to displace such attachments. The three quarter veneer gold crown also can be employed if decay of the proximal walls of the tooth is accom­ panied by loss of the incisal angle or if the incisal region is weak. The three quarter cast gold crown is not recommended if the decay has in­ cluded a considerable portion of the labial surface or if large regions of the lingual or proximal surfaces are involved with caries. I prefer in such cases to pre­ pare full crowns (cast or porcelain) or full cast crowns with veneer facings of porcelain or acrylic resin.