Bond strength of three porcelains to two forms of titanium using two firing atmospheres.

STATEMENT OF PROBLEM: Problems with casting and porcelain bonding are encountered when titanium is used in metal-porcelain restorations. The oxidation characteristics of titanium are the main problem. The bonding mechanisms in titanium-porcelain systems are complex and poorly understood. PURPOSE: An in vitro investigation was performed to evaluate the bonding characteristics of 3 titanium-porcelain systems in various firing conditions. MATERIAL AND METHODS: This study evaluated the bonding strength of 3 commercial titanium porcelains fired in a vacuum and in an argon atmosphere to cast and noncast commercially pure titanium, using a 3-point bending test according to DIN 13927 and SEM with energy-dispersive spectrometry analysis. The results were compared with an Ni-Cr alloy and a conventional porcelain that was chosen as a control. RESULTS: The Ni-Cr-conventional porcelain system fired in an argon atmosphere had significantly higher bond strength than the other systems (P<.001). In addition, the bond strength of the titanium-spark erosion-Noritake Ti22 combination, fired in an argon atmosphere, was significantly higher than the other titanium-porcelain groups, which had results similar to those obtained with the vacuum-fired, Ni-Cr-conventional porcelain and argon-fired titanium-cast-Noritake Ti22 groups. On the other hand, the bond strength of the titanium-TiBond and titanium-Vita Titankeramik groups was below the lower limit value in the DIN 13927 standard for the 3-point bending test (25 MPa). Although the results of the Duncan multiple range test showed that firing in an argon atmosphere did not affect the bond strength of the titanium-Vita Titankeramik groups, the titanium-spark erosion-TiBond group, or the titanium-cast-Noritake Ti22 group, argon firing improved the bond strengths of the Ni-Cr-conventional porcelain group, the titanium-cast-TiBond group, and the titanium-spark erosion-Noritake Ti22 porcelain group. It was also found that there were no significant differences between the bond strengths of cast and non-cast titanium groups; an exception was the titanium TiBond groups in which the porcelain was fired in a vacuum. CONCLUSION: The oxide layer produced on titanium was considered to have a potentially adverse effect on titanium-porcelain bonding. It was also concluded that matching the titanium-porcelain combination is the main determinant for optimal bonding. Firing in an argon atmosphere that limited the oxidation of titanium improved the titanium-porcelain bond in some of the groups.

Thermal cycling distortion of porcelain fused to metal fixed partial dentures.

STATEMENT OF PROBLEM: The initial fit of porcelain fused to metal restorations deteriorates during the firing cycle of porcelain. PURPOSE: This study evaluated thermal cycling distortion of 3-unit porcelain fused to metal frameworks at different firing stages. MATERIAL AND METHODS: A master model was designed to represent the 2 abutments of a 3-unit fixed partial denture replacing a missing mandibular molar. Standard techniques were used to fabricate 10 castings. Half of the copings were cast in a Ni-Cr alloy and the other half in a Pd-Cu alloy. Framework distortion was measured by means of inner fit changes, horizontal linear measurements of the framework length, and vertical fit changes of each retainer. Measurements were made (1) initially, (2) after degassing firing, and (3) after glaze firing. Differences between the firing cycles created distortion values of the retainers in 3 dimensions. Repeated measures ANOVA was used to analyze data statistically. RESULTS: Measured differences between the 2 firing stages ranged from -47 to 81.7 micrometer. For both alloy groups, retainers showed increase in vertical gap that implied poorer vertical fit after porcelain application. Mean values of inner fit change recorded for porcelain application firing were higher in magnitude than the values of metal-conditioning firing. In addition, no statistically significant differences were found among alloy types. CONCLUSIONS: A 3-dimensional distortion was observed both in Pd-Cu and Ni-Cr frameworks during porcelain firing cycle. The distortion seen after porcelain application firing was significantly greater than that seen after metal-conditioning firing. This result can be attributed to these factors, contamination of porcelain to the inner surface of metal coping and reduction in resilience of metal.

Distortion of metal-ceramic fixed partial dentures resulting from metal-conditioning firing.

The aim of this study was to investigate the distortion of metal-ceramic prostheses that occurs during metal-conditioning firing and to examine whether the distortion might be controlled by embedding the castings in an investment bulk and applying a prior heat treatment. The distortion of palladium-copper and nickel-chromium frameworks was evaluated by means of inner fit and horizontal linear measurements of the framework length. There was no statistically significant difference between palladium-copper and nickel-chromium frame-works in the changes in inner fit. In addition, there was no statistically significant difference between the invested test group and the control group in changes in fit. However, the mean deformation in framework length recorded for invested palladium-copper frameworks (-20.20 microns) was significantly smaller than that recorded for control palladium-copper frameworks (52.20 microns).

Shear strength of composite bonded porcelain-to-porcelain in a new repair system.

This study assesses the repair procedure for porcelain fracture and involves fitting and bonding a porcelain material over the original damaged crown. To simulate the situation, a test sample was designed to simulate composite bonded porcelain-to-porcelain. A total of 120 samples was prepared and the shear bond strengths were tested. Three composite resins, two porcelain combinations, and two storage-time intervals were used. Significant differences were found among the three types of composite resins. Porcelain combinations did not affect the results. Furthermore, the mean bond strength was higher at 45-day storage than at 90 days.

A matrix procedure for reproducing natural or carved tooth contours in porcelain laminate veneers.

A procedure is described for making porcelain laminate veneers by using a preformed acrylic resin matrix to reproduce the original tooth form and surface texture. The procedure can be modified to allow alterations to the original contours by adding wax to, or carving, a preliminary cast. A silicone impression is made of either the teeth preoperatively or the altered cast and is used to construct a translucent heat-cured acrylic resin matrix. The matrix is fitted to the working cast and used to condense the porcelain for veneers. A patient's restorations are used to illustrate the procedure.

[The application of an overdenture with a modified Dolder bar joint]. / Modifiye Dolder bar baglantili bir "overdenture" uygulamasi.

In this article, a modified Dolder bar attachment application is presented in two cases. The egg-shaped bars are casted in chromium-cobalt metal alloy and the retention loops are made of clasp wire in "omega" shape. The bar attachment has some advantages like being easy to fabricate and having lower cost. The laboratory made modified Dolder bar attachment we used with overdentures provided additional retention for the dentures, minimized the horizontal and vertical movements of the dentures and also strengthened the abutment teeth by splinting. As a conclusion we have tried to show that this attachment can be an alternative to use with overdentures.

[An alternative moulding technique in porcelain fabrication]. / Porselen yapiminda alternatif bir kaliplama teknigi.

In this article a moulding technique for porcelain work that can be used especially in full-mouth and multiple unit restorations, is presented. Through this technique, condensation of porcelain can be achieved properly and the firing shrinkage can be hold in a minimum level. The occlusal form can be controlled in the mouth by a provisional acrilic bridge. A multiple pieced acrilic mould is prepared from the impression taken on the provisional acrilic bridge and is used for building up the full-mouth restoration. It is concluded that this technique can be an alternative which enables us to achieve accurate occlusal form and well condensed porcelain structure.

[Thermal compatibility of metal-porcelain system]. / Metal-prselen sisteminde isisal uyumluluk.

The bonding of metal and porcelain through a firing process is rather a complex phenomenon. Besides the factors that act in bonding, the thermal properties of both materials also affect this mechanism. Different expansion and contraction behaviours of porcelain and metal cause some interface stresses. It is observed that the major objectives of the researches are to measure and determine these stresses and expose the variables affecting them. Porcelain glass transition temperature is one of the variables that the studies have focused on.

[Thermal expansion of dental alloys and porcelains]. / Dental alasim ve porselenlerin isisal genlesmeleri.

Thermal behaviour of metal and porcelain against heat is an important factor in metal-porcelain bonding. For this reason thermal compatibility and the thermal expansion of metal and porcelain are some of the important subjects to be studied carefully. In this study, by means of dilatometric measurements, we determined the thermal expansion coefficients of metal alloy (Ivotect P) and porcelain (ITS-HTE, Ivoclar) which we use in routine practice. As a result we found that the porcelain has a nonlinear expansion as oppose to metal alloy and also the firing conditions affect the thermal expansion. In addition we observed that the thermal expansion coefficient of metal alloy had changed very little in repeated castings.

[Comparison of brush and moulding techniques in condensation of porcelain work, through shrinkage, compression strength and SEM images]. / Firça yöntemi ve kalipla sikistirilarak kondanse edilen porselen örneklerin büzülme, baski direnci ve SEM görüntülerinin karsilastirilmasi.

A general character of porcelain is the firing shrinkage which creates some problems in the fabrication of porcelain restorations. To overcome this matter, a well condensation which increases the strength of porcelain and decreases the shrinkage, is recommended. Taking this point into consideration, a moulding system is developed and it is found that pressing the porcelain in a mould, minimized the shrinkage, strengthened the structure and increased the compression strength. As a result we can say that this technique has important advantages in porcelain work.

[Effect of different thermal properties and different pontic frame designs to breaking strength of metal-porcelain bridges]. / Metal destekli porselen koprulerde farkli isisal özelliklerin ve degisik govde tasarimlarinin porselenin kirilma direncine etkisi.

Bonding of two different materials, like porcelain and metal, is affected by many factors during the firing process. Thermal compatibility is one of the prerequisites in metal-porcelain bonding. Plus, the geometric differences are also accepted as an effect in thermal compatibility. In this study it is observed that the metal framework designs that we used had no effect on the strength of porcelain; however the thermal compatibility of metal and porcelain had an important effect. Besides, it is also witnessed that in metal-porcelain restorations, structures in similar strengths are achieved with hollow type pontic designs as with solid type, if they are prepared in proper conditions.

[Marginal fit of porcelain-fused-to-metal crowns: a comparative study of metal and porcelain butt margin]. / Metal destekli porselen kronlarda, metalve basamak porseleni marjinal uyumlarinin karsilastirilmasi.

Marginal openings and shoulder fit of porcelain butt margins and metal butt margins of porcelain fused-to-metal crowns have been investigated. Crown restorations were constructed directly onto the prepared teeth with 1 mm. square shoulder. Marginal openings and shoulder fit of labial surface and the cross-section of shoulder area then observed using optical microscope. Marginal fit was found better in porcelain fused-to-metal crowns with porcelain butt margin and also practically invisible neutrally-coloured join between crown and prepared tooth, was achieved with shoulder porcelain.

[A laboratory made attachment application that can be used in overdentures]. / "Overdenture" protezlerde kullanilabilecek laboratuvar yapimi bir tutucu uygulamasi.

Stabilization and retention of most of the mandibular full dentures constitute a serious problem for patients and dentists. In order to achieve a satisfactory level of retention and stabilization, we should try to save even the last remaining teeth in the mouth and use them as abutments for overdentures. In this article an overdenture application in which a laboratory made semi-precision attachment is used, presented in three cases. This attachment is spherical shaped stud attachment and has a female part made of clasp wire. The attachment is cheaper and easier to fabricate and it provides sufficient retention and stabilization for the dentures.