Wide area of dentistry science, making use of laboratory made dental fillings, veneers, and tooth coating with crowns and bridges.
In contrast to plastic photopolymeric obturations made in office, this process includes producing of complete filling in dental laboratory, which is made by silicone imprint taken of patients mouth. This helps production and increase control, therefore this mechanisms are suitable for more serious dental problems – three or more missing tooth walls. Another advantage of this process is reduced polymeric shrinkage, which if occurs in mouth, can lead to holes between the tooth and the filling, and permanent over sensitivity. These fillings are placed by glass ionomeric, resin and resin ionomeric concretes.
We use white or base alloys – same as in producing the metal frame for model moulded prostheses, metal ceramic prostheses and bridges. They excel in solidity, where white alloys are more suitable for mouths. One disadvantage is aesthetics, where compromise can be made if used at back side of the mouth. This is a method by choice, because it allows: predictable result – the design is more durable; severely damaged teeth recovery – under gum roots, which are partly build with the metal frame; perfect match between tooth surface and metal etc.
The most modern treatment by ceramic indirect obturations, which are placed on model with special brushes or the so called press-ceramic – made of wax that is cast in a furnace.
Photo composite - bonding
These are special precise designs taking place between filling and crown. Typical for these items is minimum grinding of teeth, which mostly grazes only enamel – depth 0,3 – 0,6 мм. They are moulded by imprint in laboratory and perfectly represent color and characteristics of surrounding teeth. Could be made over the gum, because this constructions rely on the so called "lense effect" (contact lenses have thin transparent edges and are invisible once placed on eyes). This modern methods takes place in situations where crown coating is not necessary, but a visual defect correction – colorings, gaps between teeth, damaged shape and size, non aesthetic restorations. This procedure is quite labour-intensive and high-tech, but the final result often exceeds expectations.
Direct pins designs
These are methods of restoration of highly damaged/broken teeth and roots, by metal pin in root canal and gum stump of plastic material. The pin is placed after accurately calculated expansion, and stumps is made of chemo- or photo composite material, often by the means of cellulose iodine die. On top of it can already be placed crown or bridge as a final touch of a restored tooth.
These are indirect pin designs, made by accurate silicone imprinted model, by dentist. This process requires both parts to be single-piece mould by white or base alloy, which matches with future metal ceramic framework. These designs are method of choice for restoration of broken teeth before coating with crowns.
Special pinlays which are placed under aesthetic restorations – ceramic crowns, in order for metal to not be visible and light could pass trough without a problem.
These items are in use in cases where damages of hard tissue of teeth are so big that can not be restored by conventional or laboratory fillings. They are the most common method of fixed prosthodontics – does not build plaque or calculus; prevent hard tissue of teeth from caries in susceptible patients; they act as a splint. At first sight massive grinding can be seen as a disadvantage – between 1 and 2 mm depending on grind place and design type, but it only looks this way to an unacquainted with the matter eye. Most important detail of crowns is type of grinding. There are two methods – non-threshold and threshold.
Non-threshold crowns are an old method, widely popular till the half of the past century, because of its inaccuracy. In this method teeth are grinded at an angle which causes severe injures of gums and bones, and then leads to imprint defects. Dental specialists have no information where the edge of the crown is, which leads to chronic injures again of gums and bones in result of construction sinking. This shortens its functionality and worsens the condition of grinded teeth as time goes. Aesthetics also suffers because of missing space for ceramics in cervix next to the gum. Such crown lasts approximately 5, maximum 10 years, then it stays in the mouth which is unhealthy
In threshold crowns treatment all these disadvantages are overcome by creating threshold in the tooth over the gum or under. That is why gum aesthetics do not suffer in time, because the edge of the crown lays on the threshold. In laboratories, dentists receive accurate information with the help of modern imprint equipment – А-silicones. Imprints are taken by one or two phases, while before extracting restorative material, dentists remove retraction cord, which secure place for the thin material. This is a very precise procedure – if crowns do not fit perfectly, they are produced again (at the expense of dentists). This method of grinding is the only possible one for ceramic and zircon crowns and bridges. Mentioned above factors and many such secure functional durability of approximately 15-20 to 40 and more years.
Produced by white or base alloys and are used for restorations at back areas, or where there is not enough space for grinding of hard tissues of teeth – because of depth concern, close proximity of nerves and tooth surface. That is why these crowns can be part of a metal ceramic bridge, in which the back root is metal crown, and the rest of the teeth in front are covered with ceramics for better aesthetics.
Most used crowns in dentistry. They consist of metal stump (substructure) made by white or base alloy, same as metal crowns, but over this stump is placed chemically integrated ceramic substructure. The chemical bond between these two parts is performed by metal acid layer. Isolation of metal is possible because of the placement of glaze. Which make for aesthetic look of the design, because of the placed ceramics which perfectly represents the natural color and shape of teeth.
Photo composite crowns
In cases of long term temporary treatments or financial reasons, in which patients prefer more durable aesthetics treatment. They are produced in laboratory by imprinted model as photopolymeric fillings. Can be worn about 10-15 years.
These crowns are produced by plastic in office environment or in laboratory. They can be used for temporary crowns to preserve: grinded teeth"s position, gum"s position, vital teeth, aesthetics and mouth"s natural look. Usually are made within the same appointment and patients leave with “their” teeth. They are placed by temporary concrete till their replacement with permanent crowns.
The most modern method of teeth coating, especially suitable for visible areas. There is no metal frame which repeatedly increases their aesthetics. This is the standard for quality in dentistry in 21st century, which can not be reached by any other design.
Press-ceramics – ceramic crown is mould in the same way as metal one, by wax model of the teeth.It is possible for individual additional surface adjustments of color to be made with a brush. · Layer - laid on ceramics – crowns are shaped with thin brush. Here, no surface coloring is required. – it is within the tooth.
Ceramic crowns with zircon oxide so called "zircon crowns"
These constructions do not differ in durability from metal ceramics, which is possible because of the zircon frame.It has ceramic matte color (non-transparency), which combined with its quality, make this method a preferable choice for back areas. Zircon oxide ceramics is the most labour-intensive method in fixed prosthodontics. The basic structure of every zircon ceramic crown is made by CAD-CAM technology – computer generated frame of zircon, instead of classic metal, on which dentists manually apply the ceramics with a brush.
At first sight dental bridges look like the actual number of crowns one next to each other. In reality they have many differences with crowns, as the biggest one starts from their indications – they restore damaged parts of teeth, while bridges restore number of missing teeth. Bridges always lay on double sided bearing, therefore back teeth are so important and should not be easily extracted. Supporting teeth are made as if for single crowns, but their axes have to match. That is why after tooth extraction it is not advisable to wait more than a month – neighbour and opposite teeth migrate, grow and incline, and would not be good support in future.In these cases in help comes orthodontic replacement (additional cost) or the bridge is made of number of articulated parts. The middle part (missing teeth) touches the gum and plays a role of a natural tooth (only if bones are not infected in previous extraction or a lot time has been passed – then the place is sunken and in order to achieve aesthetic look a additional bone plastic is needed). This part can be hygiene friendly made, to allow brush and other cleaning devices to reach the area, but this is only possible in back areas of oral cavities. Bridges can be:
Metal - ceramic
Ceramic bridges with zircon oxide so called "zircone bridges" or "ceramic bridges"
The frame here must be durable, so it is made of zircon oxide (laboratory, outside of Bulgaria, working again by CAD-CAM technology).This material is the same as one in production of artificial diamonds, it is aesthetic - pale yellow and matte, and its durability of metal framework. On top of it is the ceramic laid on in layer manner
Metal bridges with external photo composite
Solid temporary constructions (up to 5-10 and more years) with satisfactory aesthetic effect (upper teeth).If made completely of photopolymer, it has short lifespan, but it is more aesthetic.
Production is made of plastic, but could be also attached on metal frame if designs are longer. This variation is also temporary solution and is failed method “blend” (or “Ц+Б”) if used long period of time - patients are relatively satisfied by the looks, but with time passing, plastic material starts to absorb liquids, change color and intoxicates gums. This construction can be build in dental office environment, but if necessary can be made in dental laboratory.
Made of plastic,but could be also attached on metal frame if designs are longer. This variation is also temporary solution and is failed method “blend” (or “Ц+Б”) if used long period of time - patients are relatively satisfied by the looks, but with time passing, plastic material starts to absorb liquids, change color and intoxicates gums. This construction can be build in dental office environment, but if necessary can be made in dental laboratory.