Bite - In

This issue of rewind looks into a new alternative to conventional Crown & Bridge optoins of Porcelain Fused to Metal. Dr. Ajay Kakar review one of the newer materials on the market i.e. the FibreKor/Sculpture system from Jeneric Pentron.

Metal Free Bridges - A Viable Alternative to Conventional Porcelain Fused to Metal

Dentistry has shown rapid changes in technology and thereby methodology. It is often quoted in many current seminars on restorative dentistry that G.V.Black has been laid to rest. It is quite true that the paradigm "Extension for Prevention" is no longer valid if the restorative material is going to be composites instead of Silver Amalgam. This is no way decreases the foundations of retorative dentistry laid down by G.V.Black. All knowledge is contextual and is applicable within a certain frame of reference. G.V.Blacks frame of reference did not have any materials with the capabilities of todays composites and hence he had to create rules which best served the interest of the patient with the limitations of the materials being used.

A similar situation is today evloving in the field of Fixed Prosthetics. In fact, I personally get the same feeling when I talk at any gathering about the possibility of fabricating a bridge without and metal, as when there would be talk about doing a posterior composite restoration. There would be a few ethuthiasts, a few middle of the road dentists and some die hard traditional skeptics. I do not per se lecture on the FibreKor/Sculpture system. I have found myself generally in the role of introducing the speaker and the FibreKor/Sculpture system to dental audiences on multiple occasions.

I usually begin by getting a response from the delegates about the quantity of PFM bridge work being done and overall satisfaction with the end result. Most responses point to the fact that a large volume of ceramic bridge work is being done in dental clinics. Even though overall satisfaction is pretty good, there are couple of very common complaint among all clinicians.

One of them is a lack of 100% fit of the metal trial at the first instance. I do not know where to attribute this problem to. Is the dentist not making a very accurate impression leading to mild inacuuracies or Is it an inherent problem of casting shrinkage, wax discrepancy, high technique sensitivity leading to mild inaccuracies or is it a combination of both? Whatever be the answer, I find that most clinicians find some or the other small problems in fit and accuracy which casues a repeat of the metal trial or an acceptance of mariginal discrepancy. The other major problem is that of time. Most quality labs are always busy. The entire job requires a metal trial, a bisque trial and then the final fit. Multiple visits spread over a number of days does tend to reduce patient motivation and general enthisiasm to get dental work done.

Today there is an alternative available for a large majority of crown and bridge work. This is the FibreKor/Sculpture system from Jeneric Pentron. This is one particluar product for which I find company claims being as close to truth as I have seen. To quote "FibreKor/Sculpture has the strenth of metal and the beauty of Porcelain". It is somewhat akin to eating the cake and having it to. Resin based ceramic material has been on the anvil for quite some time. What was required was a substructure which could substitute the metal component. As far as my knowldge goes, there are two companies currently actively marketing metal free resin based ceramic systems viz. FibreKor/Sculpture from Jeneric/Pentron and the Targis/Vectris system from Ivoclar. There are a few othe companies with similar product lines but not yet very actively promoting Bridges.

In concept both the materials are similar in that they have a resin base with a ceramic filler with photo initiators and heat initiators for polymerization. Both have glass based fibres as the substructures substituting the metal. The difference is in the processing method and a few given advantages that the FibreKor/Sculpture system has by way of a glazing facility and reduced laboratory processing time.

The FibreKor/Sculpture system consists of two kinds of materials. The FibreKor component is the glass fibres which are available in multiple shades in two widths. 6 mm and 3 mm. These fibres have to be cut to the required length as per the case and then have to be coalesced to form a main supporting bar for the pontic area and then additional fibres are added for reinforcement. These fibres are light polymerized and them tempered in a heat and vacumn cycle to get full strength. Once completely polymerized these fibres have a phenomenol strength. In fact the company issues what is called the FibreKor challenge. In anybody can break a bar of totally polymerized Fibrekor with their hands they ge tons of free stuff or something like that. I have personally tried and failed. The only results have been a few bruised fingers.

This fibre substructure is then built up with Sculpture. Sculpture is 80% ceramic filler in a PCDMA resin base. The ceramic filler is primarily Bairum Borosilicate. This material is available in a paste form and is applied over the fibre substructure to which it bonds. Sculpture is available in a complete shade range as per the Vita colors. Sculpture is available as opaceous and translucent material to provide a totaly flexibility in color masking. In additinon, incisal shades, gingival shades and a whole range of tints are available to create special effects. A very beautiful feature of Sculpture is that it can also bond to metal. If for any reason a metal substructre is created instead of the fibre substructure a metal coupler can be used followed by a layer of Sculpture powder to mask as well as bond to the metal. The subsequent layers can be make with the regular Sculpture paste. The powders for the metal substructure are also available in the entire Vita shade range.

Cure Lite Plus The equipment which comes in the entire unit consists of a light box called the "Cure Lite" which is meant for the primary light polymerization, a heat tempering oven to which is attached a vacumn pump, a spot curing light for initial adaptation of the fibres or to stabalize the Sculpture material, a pressure bowl which consists of a metal base and a transparent top into which nitrogen is introduced to eliminate the oxygen and give a complete cure to the glaze. In addition to the basic equipment the starter material consists of all shades of opaceous and translucent Sculpture, the stains, 6 & 3 mm fibre strips in five shades and a die sealer, separtor and spacer. The kit also has a set of three beautiful hand instruments and polishing pastes and brushes. All that you need in addition is a nitrogen cylinder for the glazing bowl.

The entire FibreKor/Sculpture unit is so small and sleek that it can be set up in a matter of minutes on any corner table and you are ready to fabricate an entire bridge. Generally a conventional three unit bridge takes about a hour and half to fabricate. I think it makes very good sense to install a unit in the clinic itself and eliminate the entire problem of lead time between tooth preperation and ultimate delivery of the product. On occasion in my clinic bridge preperations have been done in the morning and the final bridge bonded in the eventing. Phenomenol in terms of chair side time saved, no temps necessary and exceptionally good results. The material handling is extremely easy for any dentist who has done any form of composite work. The entire processd is simplified to a very large extent.

The system is not just limited to preparing crowns and bridges. The FibreKor/Sculpture unit can be optimally used to prepare excellent inlays, onlays and veneers. In fact, it is very difficult to discern any differences between the final finish of this product from conventional ceramics. On the other hand one major advantage of this product is that of a comparable to natural oppsoing tooth wear resistance. Ceramics have a very major disadvantge that it tends to wear down the opposing natural tooth. The opposing tooth wear of Sculpture is almost the same as that of natural enamel. Another major advantage is that of reduced toth preperation since there is no metal collar required nor is there any metal to be masked by a large layer of material. In quite a few cases where only a single tooth is missing the Encore bridge modification can be used. Even though it is beyond the scope of this article to describe the entire Encore preperation, (A complete presentation will be shortly available in one of the other sections) it basically consists of preperating inlay boxes on the abutment teeth and fabricating a bridge using the inlay boxes as supporting structures. This kind of preperation takes all of about 15 minutes and almost brings chair side time down to a near 20% of conventional bridges. Even the lab time gets cut down to about 70% of full coverage bridges.

A three unit bridge One of the only limitation of this system is that it can only be used in those cases wherein a single contiguous pontic area does not exceed 15 mm. The very few limitations of the system do not even comprise more than 20% cases regaularly seen in clinics. Even in such cases, metal substructures can be fabricated in an external lab and then the rest of the bridge completed in house. One of the last factors but not the most important factors is the economics of the system. The system is much more economical when compared on a per unit basis with ceramics and the basic investment cost is almost less than half of ceramics. The ease of use and all other benefits makes is a very attractive proposition to have the system in house and create prosthesis as desired and visualised by the clinician.

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