DENTAL PROSTHETICS
Dental crowns and bridges
At the RepićDental Centre, we pay special attention to preserving the function of teeth and the biting and stomatognatic system. Upon detailed clinical examination and analysis of x-rays of the teeth and jaws, we are then able to propose an individual prosthetic treatment plan for each patient, in order to compensate for one or more missing teeth. Depending on the clinical findings and the patient's budget, missing teeth can be replaced using mobile or fixed prosthetic solutions.
Mobile prosthetic solutions (dentures) are best for patients with complete or partial toothlessness. There are several options for stabilizing the dentures in the mouth, such as: combined mobile/fixed dentures, telescopic crowns or implant-set prosthetics.
Fixed prosthetic solutions include veneers, crowns, bridges and implant-set bridges.
We use contemporary restorative materials that allow us to meet the patient’s aesthetic and functional requirements. We are able to offer a range of materials for fixed prosthetic work, including:
Metal-ceramic crowns and bridges
have a long tradition in dental prosthetics, and are considered the standard in fixed prosthetic therapy. This type of crown or bridge is the most common choice of patients, due to their affordable price and the long-lasting materials. The metal frame of the crown or bridge protects the load-bearing teeth, while the ceramic aesthetically mimics the missing teeth. The metal base of the prosthetic structure is most often an alloy of cobalt, chrome and nickel, dental gold or titanium. The ceramic structure is attached in layers to the metal structure, where the ceramic forms a strong bond with the metal.
Once the decision is made to use crowns or bridges, the dentist must first abrade the load-bearing tooth in order to ensure sufficient space for the prosthetic. The next step is taking the impression in order to make the prosthetic in the laboratory. In this step, the colour of the ceramic is selected in order to best mimic the natural teeth. After the prosthetic is made in the laboratory and tried in the dental clinic, the crown or bridge is first installed temporarily, and once the dentist confirms that the fit is right, it is permanently cemented onto the tooth.
Metal-ceramic prosthetic solutions are appropriate for the replacement of one or more lost teeth, either in the front or back of the jaw. When properly positioned, they have both the appropriate mechanical and aesthetic properties.
The main advantage of metal-ceramic crowns and bridges is their price, mechanical durability and long life. According to the literature, 90–95% of all metal-ceramic prosthetics last ten or more years in the mouth. They are somewhat less expensive than fully ceramic (metal-free) solutions.
Shortcomings of metal-ceramic crowns and bridges are the limited aesthetic possibilities in comparison with fully ceramic (metal-free) systems. The reason for this is that the metal base is a dark grey colour. Due to the colour of the metal under the ceramic layers, the penetration of light is hindered, and the tooth colour may not appear sufficiently natural. Patients often complain about the dark edge of the structure along the gumline at the edge of the crown. After a certain amount of time, the metals at the base of the crown may release ions, that they enter into the gums. However, careful preparation (abrasion) of the load-bearing tooth can help to reduce the appearance of these undesired effects.
Fully ceramic crowns and bridges (metal-free ceramic)
Crowns and bridges made completely of ceramic are the alternative to metal-ceramic prosthetics. They are also called “porcelain” teeth. The aesthetic demands of patients in recent years are increasing, and are often key in making the decision on which prosthetic restoration technique to use in replacing missing teeth. Fully ceramic crowns and bridges perfectly mimic the appearance of natural teeth, making them superior to metal-ceramic structures. Unlike metal-ceramic structures, where the metal base hinders the penetration and diffusion of light, which affects the colour of the tooth, crowns and bridges made exclusively of ceramic have exceptional aesthetic properties that closely mimic the natural appearance of teeth. For patients, the procedure of making ceramic crowns is similar to the procedure for metal-ceramic crowns: tooth abrasion (for the dentist to make room for the replacement) and taking the impression that is sent to the laboratory. Meanwhile, the colour of the future replacement that best suits the patient’s wishes and existing teeth is selected. Once the prosthetic is made, it is cemented onto the abraded teeth. While preparing for this type of replacement, abrasion is less extensive, and more of the healthy tooth tissue can be preserved. The computer-guided construction of these crowns and bridges ensures the perfect fit along the abraded tooth surface, making cleaning easier and reducing the accumulation of food between teeth and the gum inflammation that can result.
The technological development of new materials enables excellent mechanical properties of metal-free ceramic structures, without losing any aesthetic function. In terms of mechanical properties and the duration of these structures, fully ceramic crowns and bridges are comparable to metal-ceramic systems. According to the literature, 91–97% of metal-free ceramic replacements last for five or longer years.
Metal-free ceramics can be used to replace one or more lost teeth. Newer materials for completely ceramic fixed prosthetic replacements are made up of leucite reinforced lithium-disilicate ceramic, leucite or lithium-disilicate reinforced glass-ceramic and oxide ceramics such as aluminium-oxide ceramics and zirconium-oxide ceramics. The price of metal-free ceramic crowns and bridges is somewhat higher than metal-ceramic replacements, due to the more complex procedures involved in the clinic and in the laboratory.
Zirconia ceramic crowns and bridges
Zirconia (Zirconium dioxide) ceramic is a type of metal-free ceramic that is becoming more widely used in dental prosthetics due to its exceptional aesthetic and functional properties, especially for building fixed prosthetic replacements (crowns and bridges) at the front and back of the jaw. This material belongs to the group of the oxide ceramics and has a high resistance to breakage, wear and high temperatures, and against corrosion. Zirconia has been widely used in medicine and dentistry for more than 50 years. This material is used to make the femoral head in orthopaedics, while in dentistry, in addition to prosthetics, it is also used to build endodontic posts, orthodontic brackets and implant abutments.
The base of the crown or bridge is made of zirconium dioxide, and ceramic layers are baked onto this. They are white in colour and do not appear along the edge of the replacement. Zirconium dioxide is a biocompatible material that does not cause an allergic reaction. It poorly conducts electricity and heat, thereby making teeth less sensitive. There are numerous outstanding qualities of zirconia ceramic structures: premium quality aesthetics, exceptional purity, biocompatibility, less abrasion of natural teeth required due to the high strength of the material (thickness of only 0.4 mm ensures sufficient strength). Due to its high strength and hardness, zirconia ceramic structures can be machine made from factory-built blocks. Thanks to computer-aided construction, the crown or bridge made from zirconia ceramic sits precisely on the abraded edge of the tooth, making it easier to maintain oral hygiene and reducing the possibilities of gum inflammation.
In terms of its aesthetic properties, this type of material is an excellent choice as it perfectly mimics the natural transparency and colour of teeth, and the high strength compares to the strength of the strongest metals. The mechanical properties of zirconia ceramic are comparable to metal-ceramic replacements, while they better mimic the natural appearance of teeth. The final colour of the prosthetic is determined by the thickness of the ceramic, thickness and colour of the cement and colour of the abutment. Due to its high strength, it is also possible to create very thin prosthetic replacements out of this material (with a thickness of the base construction of just 0.3 mm in the front of the jaw and 0.6 mm in side segments), thereby ensuring translucence and aesthetics of the material. It is suitable for use in both the front and back parts of the jaw, and can be used to create large prosthetic restorations to compensate for a larger number of missing teeth.
The price of zirconia ceramic crowns and bridges is somewhat higher than metal-ceramic crowns and bridges, due to the more complex construction procedure in the clinic and the laboratory. The abrasion, taking the impression and cementing of the final prosthetic must be absolutely precise, in order to the prosthetic replacement (crown or bridge) to fit exactly against the abraded tooth.
Glass-ceramic
Glass-ceramic is a type of completely ceramic material that is used to make prosthetic replacements. The high aesthetic demands of patients who are becoming increasingly educated about these procedures are not met by those prosthetic materials used in the past. The intensive development of material technology has led to the creation of sufficiently strong glass-ceramic materials with exceptional aesthetic features. Glass-ceramic, like any material, has its limitations, and one should be familiar with them in order to obtain the best possible effect.
Glass-ceramic is created through the controlled crystallization of glass. There are several types of glass-ceramic that differ by their properties: IPS Empressceramic (leucite reinforced glass-ceramic), IPS Empress 2 ceramic (ceramic with a lithium disilicate core, stronger and more resilient than the former type) and IPS E.Maxceramicwhich has a similar structure to IPS Empress 2 ceramic (lithium disilicate core) but is must stronger than the two previous types of glass-ceramic.
E.Max Press or Empress crowns and bridges are fully ceramic crowns and bridges constructed of lithium disilicate ceramic. The high translucency of lithium disilicate ceramics enables exceptional aesthetics and is particularly indicated for prosthetic restoration in the aesthetic zone of the jaw (area visible while smiling). It is stronger than other types of glass-ceramic and is indicatorid for prosthetic work in the front part of the jaw, for individual crowns or three-tooth bridges ending at the second bicuspid tooth, and for individual crowns in the front or rear part of the tooth arch, veneers and indirectly laid fillings (inlay, onlay). E.Max ceramics are produced in a wide range of colours and therefore are able to closely mimic the natural appearance of teeth.
Three factors will influence the final colour of the prosthetic: colour of the abraded tooth base, colour of the cement and colour of the crown. In some cases, the use of lithium disilicate ceramic is not simple, due to the differing colours of the abraded tooth base that might appear through the crown material. However, by knowing the properties of the material and the preparation techniques, such issues can be resolved to the mutual satisfaction of the patient and the dentist. A combination of different colours and cement transparency can be adjusted to achieve the same colour as the crown, even when the colour of the abraded teeth is not uniform. After the final cementing of the crown onto the abraded teeth, the connections between the crown and the tooth are then polished, in order to make maintaining oral hygiene easier.
To achieve a functional and aesthetically pleasing result, it is important to properly determine the indications for this type of prosthetic. The mechanical properties of the E.Max crowns is slightly lower than zirconia ceramic, and these types of prosthetic replacements are not recommended for large prosthetic work in the back section of the mouth. They are best applied for individual crowns or three-tooth bridges in the front of the tooth arch up until the second bicuspid, and for individual crowns in the front of back of the tooth arch; for veneers and indirectly made fillings (inlays, onlays).
FAQ
That is a difficult question to answer. The duration of crowns of all types of materials, in Croatia and abroad, for a 10-year period is from 85–95%, which is considered successful prosthetic work. However, numerous factors will influence the duration of prosthetic work, such as regular check-ups and maintaining oral hygiene, the condition of the load-bearing tooth and the gums, the proper selection of the prosthetic for a specific case, and the proper construction of the prosthetic. Due to all these factors, the duration will vary from patient to patient.
Patients occasionally incorrectly assume that their teeth are protected by the “covers”, i.e. crowns and bridges, and that oral hygiene therefore does not need to be intensive. This couldn’t be further from the truth. Through diligent oral hygiene and regular check-ups at the dentist, patients can significantly contribute to the long life of the prosthetic in the mouth, and the health of the rest of the teeth in the oral cavity.
Crowns and bridges should brushed the same way as natural teeth – from the right upper quadrant to the left upper quadrant, and the left lower quadrant to the right lower quadrant. It is necessary to cover all surfaces of the teeth and replacements, for a total duration of three minutes. A circular motion of brushing is recommended, and the final brush stroke should be from “red to white”, or from gums to teeth, in order to prevent the retraction of the gums after fixed prosthetic therapy. Numerous aids are available to facilitate the hygiene of prosthetic work, such as interdental floss, electric toothbrushes, oral water showers, interdental brushes. Plaque detectors are sold widely and give information about the quality of brushing. We will be happy to teach you how to properly maintain oral hygiene in order to extend the life of your replacements, to our mutual satisfaction.
