Fixed dental prostheses are fixed, unremovable prosthetic works cemented to the prepared and well-scraped teeth or supported by implants. Only a dentist can remove them. These can be inlays, crowns or bridges.
What is a dental crown and when do we use it? The crown is a prosthetic work that covers the whole clinical crown of the scraped tooth. After the scraping of the deteriorated tooth and after the realization of the impression the crown is prepared at the dental laboratory.
The crown is recommended in the following cases:
- In case the tooth has a large caries that cannot be restored anymore through filling or an inlay.
- At the final treatment of the endodontically treated teeth.
- In case of severe acquired or inherited discolorations, for ex. inadequate development of the enamle, endodontically treated tooth.
What is a dental bridge and when do we use it? The dental bridge is a fixed prosthetic work in the case of which the artificial teeth that replace missing teeth are fixed with cement to the well-prepared abutments (existing teeth, roots, implants).
The bridge is recommended in the following cases:
- in the case of a missing tooth if the realization of a dental implant is not reasonable
- in the case of more missing teeth
- in the case of aesthetic correction of more teeth
- in the case of weakened teeth in order to apply splints
Partial veneer metal-ceramic crown
The frame of the crown or the bridge is made of metal, a very hard and elastic material, so it resists the occlusal force of the molars. On the upper external part of the metal frame – that becomes visible when the patient smiles – the dental technician burns multiple ceramic layers that are similar to the original colour of the tooth, this way we get an aesthetic prosthesis. The metal frame is realized via laser sintering in order to get a perfect fitting, occlusion.
Full veneer metal-ceramic crown
This differs from the above-mentioned partial veneer metal-ceramic crown because in this case the whole surface of the metal frame is covered by a porcelain layer. This way the metal frame cannot be seen when the patient opens his/her mouth. Its aesthetic effect is more reduced than in the case of the pressed ceramic crown because the metal frame situated under the ceramic layer does not allow the light to enter, so it cannot enlighten so beautifully the gingival margin. So the margin of the crown remains in shadow and because of this sometimes at the margin of the crown appear greyish and bluish lines. At our office all the metal frame-supported prosthetic works are realized via laser sintering, the advantage of this being a precise marginal closure.
E.max pressed ceramic crown realized without a metal frame
There are some cases when the dental tissue becomes so deteriorated that its aesthetic restoration is possible only when we realize a crown. In the case of the front teeth the best solution for restoration is the pressed ceramic crown, also called Jacket crown. Aesthetically this resembles the most the original teeth. Its aesthetic effect is much better than that of the metal-ceramic crown. This allows the light to enter the surface of the tooth and to enlighten the gingival margin, so there are no bluish and greyish lines like in the case of the metal-ceramic crown. The only disadvantage of this is that it cannot be used for the realization of a complete prosthesis, in these cases we can make bridges from zirconium dioxide with a CNC machine, their aesthetic effect is not so good as that of the pressed ceramic, but they look better than the metal-ceramic crown.
Zirconia crowns, or better said crowns made of zirconium dioxide are the most popular. Zirconium belongs to metals, it is a very hard material. Zirconium dioxide is a type of ceramics but it has different characteristics than traditional porcelain. It is as hard as zirconium but its white colour made it possible to create aesthetic prosthetic works. Zirconium dioxide can be processed only through a new process, i.e. CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) technology that allows us to create some more precise prosthetic works because both the planning and the realization take place with the help of a computer.
- due to its translucency it has an exceptional aesthetic effect and the tooth seems to be natural
- as it does not contain metals, it does not cause allergic reactions
- it spares the gingiva, there are no dark gingival margins, it can be easily cleaned
- it does not conduct heat and cold as much as metal prostheses do
- it can be easily coloured
- it is extremely hard
- it has a long lifespan
Pressed ceramic inlays and veneers
Inlays are created in order to perform aesthetic corrections when on the front teeth appear caries, discolorations or injuries. In these cases we remove a very thin layer of enamel from the surface of the teeth and on the basis of the impression the dental technician prepares the ceramic inlays according to the patient’s wish.
A veneer is a type of tooth filling that replaces the missing dental tissue. This is made in a dental laboratory, it is personalized, so it will perfectly fit in the cavity remained after the cleaning of the caries. The difference between inlay and onlay veneers is that in the case of inlay the veneer fills only the dental cavity, onlay is used when the surface of the tooth has to be restored as well because the injury is too serious and inlay is not enough anymore.
When do you need veneers?
- in case the dental caries affects two or more surfaces
- in case the tooth is not adequate as far as its shape and masticatory function are regarded
- in case we replace old and large amalgam fillings
- in case of worn off or broken cusps
- when a cover-filling is made for the endodentically treated teeth
- at the restoration of the height of bite
What are their advantages?
- they assure a better marginal closure than the composite fillings
- they restore better the anatomical shape of the tooth
- they assure a perfect contact with neighbouring teeth
- they have an exceptional masticatory stability
- there is no need to scrape the teeth
Primary and secondary crown for the anchorage of telescopic prosthesis
It can happen that in the mandible remain only 2-3 teeth, on these cannot be realized a fixed prosthetic work. In these cases after the scraping of the existing teeth a primary metal crown made by laser sintering will be cemented on these teeth which – together with the secondary crown of the prosthesis – will contribute to the stabilization of the removable prosthesis.
The temporary crown is created at the office using a certain type of self-polymerizable acrylate.
The patient wears the temporary crown or bridge until the inflammation surrounding the soft tissues disappears, and these tissues will be stable enough to realize the definitive prosthesis.
In some cases this period can last even 2 months, but if we are not patient, shortly after the sticking of the definitive prosthesis the gingival margine will recess, the margin of the crown will be free and this will cause permanent aesthetic problems.
Why is the temporary crown necessary?
- it protects the prepared tooth stump against the mechanical impacts (mastication, cold-warm stimuli), teeth that are alive become very sensitive to different external stimuli
- it assures the aesthetic look, the patient doesn’t leave the office with missing teeth
- it maintains the masticatory function
- it maintains the needed space, it hinders the inclination of the neighbouring teeth
- it is useful for the maintenance of the health of the gums after scraping or extraction