| Abstract|| |
Esthetics with porcelain fused to metal restoration in the anterior region can be adversely affected due to the inadequate teeth preparations and design of the prosthesis. We presented here a case report where esthetics was compromised due to darkening of the interdental papilla and marginal gingival and overcontoured restorations in relation to porcelain fused to metal restorations. Good esthetic results were obtained by using basic principles of tooth preparation and using collarless metal ceramic restorations.
Keywords: Collarless metal ceramic restoration, direct lift technique, subgingival margin, two-plane reduction, umbrella effect
|How to cite this article:|
Afroz S, Chand P. Collarless metal ceramic restorations to obscure the umbrella effect. Indian J Dent Res 2010;21:600-2
Porcelain fused to metal (PFM) crowns may sometimes be associated with grayish discoloration at the cervical third of the restoration due to thinness of porcelain in this area and in the adjacent tissues due to reflection of light meeting the opaque substrate of PFM restoration and thin gingival tissues.  This is an optical effect that is more noticeable when the upper lip is not retracted and has also been described in the literature as umbrella effect. 
|How to cite this URL:|
Afroz S, Chand P. Collarless metal ceramic restorations to obscure the umbrella effect. Indian J Dent Res [serial online] 2010 [cited 2014 Nov 21];21:600-2. Available from: http://www.ijdr.in/text.asp?2010/21/4/600/74228
The esthetics with porcelain fused to metal restorations may be increased by proper placement of the cervical finish line without encroaching on the biologic width (contributes to optimization of gingival health and the esthetic design of the prostheses), extended porcelain margin and use of translucent luting agent. ,, The margin of choice in esthetic situations in PFM restorations is a shoulder with porcelain labial margin. This design allows for an adequate thickness of ceramic material at the margin, which provides excellent esthetic result, and places glazed porcelain in the gingival sulcus. ,
| Case Report|| |
A female aged 21 years reported with the problem of darkening of the interdental papilla and marginal gingiva in association with her newly placed fixed dental prostheses [Figure 1]. She was treated by two 4-unit fixed dental prostheses to replace the missing right and left maxillary lateral incisors by some general practitioner. The dental history, as told by the patient, clinical and radiographic examination revealed that her maxillary lateral incisors were missing congenitally and her canines had erupted in the space of the lateral incisors, which had resulted in unsightly spacing between the canines and the premolars. The patient was not satisfied with the esthetic results of her previous restorations. On examination, it was found that the restorations were overcontoured in the cervical region and the zenith of the marginal gingival was not properly placed. The restorations lacked translucency and had a very chalky appearance [Figure 2]. When the restorations were removed, it was found that the teeth preparations were inadequate, with no definite margin preparations, and in the central and the canine teeth, there was a lack of two-plane reduction, which had resulted in overcontoured restorations in all the dimensions and nearly exposed pulp in the central incisors of both sides. The flat occlusal preparations of the first premolars had resulted in nearly exposed pulp [Figure 3].
Two PFM-fixed dental prosthesis with shoulder ceramic (on central incisor and canines) were planned to replace the missing teeth using central incisor, canine and first premolars as abutment bilaterally. Intentional root canal treatment of nearly exposed teeth was undertaken.
|Figure 3: Inadequate preparations showing lack of two-plane reduction on the anterior and flat occlusal plane preparation on premolars|
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The preparations were improved by performing a two-plane reduction, subgingival placement of shoulder margin, which was carried up to the proximal-lingual line angle, and a chamfer margin preparation lingually.
After a period of 2 weeks observation with the temporary restorations, when the patient was comfortable with the esthetics and function, the final impression was made and the new restorations were fabricated [Figure 4].
Lab procedure included the fabrication of metal substructure in the usual manner, the framework was shortened by 1.5 mm labially and opaque was applied and fired. The die was coated with cyanoacrylate resin, which acts as a sealant of porous stone. Porcelain release agent was coated to the shoulder of the prepared die as it results in easy separation of the restoration. The porcelain was condensed directly onto the die and opaque porcelain and fired. A second bake is usually necessary for better margin adaptation. 
| Discussion|| |
In this case, the patient presented with the umbrella effect where the darkening of the interdental papilla and marginal gingival was more evident when the lips were not retracted. When the lips are retracted (as during intraoral photography), the light can be directly distributed into the tissues and thus the apical extension of the framework does not affect the optical behavior of the crown. 
A single-plane preparation results in insufficient reduction in either the cervical or the incisal area. Here, the improper teeth preparation and improper margin preparation and placement were the main cause of opaque show thorough, the darkening of the gingiva and the overcontoured restorations.
The problem here was managed by improving the preparation, placing the margin subgingivally and reducing the framework labially for fabricating shoulder ceramic margin.
Properly contoured and well-adapted temporary restorations helped in improving the gingival health and finalizing the best esthetic outcome. 
The advantages of making a collarless metal ceramic restoration are improved esthetics and easy plaque removal when the gingival tissues are in contact with highly glazed porcelain as compared to highly polished metal.  Disadvantages are difficulties during fabrication, where marginal adaptation is not as good as that of cast metal, chances of fracture of unsupported margin during evaluation or cementation, extra lab steps that require more time and, therefore, are more costly.  However, in a study on the evaluation of fit of metal ceramic margin designs, porcelain-butt margins (labial shoulder ceramic) had demonstrated a better marginal fit than featheredge metal margins (marginal ceramic supported by feather edge metal) and, thus, had given clinicians evidence to prefer the use of porcelain-butt margins.  Fracture during function is not a problem because labial margins are not subjected to high tensile stresses. ,
Removal of 1.5 mm of the labial framework is optimum as it does not decrease the fracture resistance of the restoration. Greater the metal reduction better will be the esthetic result;  however, the procedure becomes more technically demanding. Some authorities recommend the use of a 360 o porcelain margin as, according to them, it theoretically permits improved light transmission and improved esthetics. This approach complicates the lab phase of fabrication and provides, at best, minimal benefit. ,
Various techniques are described to make collarless restorations: platinum foil matrix, direct lift or cyanoacrylate resin and porcelain wax. The direct lift technique has the advantage of being less time consuming, less technically demanding and less costly than the cyanoacrylate resin technique.
| Conclusion|| |
Desirable esthetics can be achieved by collarless metal ceramic restoration. In this patient, the optical phenomenon of umbrella effect was prevented by using shoulder porcelain. It is cheaper and stronger, being more conservative, having greater longevity and being an esthetically acceptable alternative to all ceramic restorations. Also, an all-ceramic restoration with the opaque alumionous core may show a similar optical phenomenon.
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Prosthodontics, Career Post Graduate Institute of Dental Sciences and Hospital, Lucknow
[Figure 1], [Figure 2], [Figure 3], [Figure 4]