Cover denture: design, advantages and disadvantages
Human teeth, unlike other organs and tissues, can not recover, and sooner or later, almost everyone faces the need for their prosthetics.To replace the defects of the rows, either removable dentures or non-removable devices are used.Modern high-tech materials make it possible to produce functional and exceptionally reliable orthopedic constructions of different types.
Removable structures are divided into partial and complete.The first are set if one or more teeth in the row are stored.The latter are necessary for complete adentia, i.e., the absence of teeth.Table of contents: What is covered removable dentures?Indications for the manufacture of cover prostheses Contra-indications Advantages and disadvantages of cover prostheses Materials used in production:
It is impossible to unequivocally answer the frequently asked question: which dentures are better?All types of dentures have their own indications and contraindications, undoubted advantages and obvious shortcomings.
What is covered removable dentures?
Covering models are new generation removable dentures.They are called so, because they cover the remaining teeth( or implants) from the sides, as if "swirling" them.Models consist of several parts - covering the crest of the alveolar process of the basis, fixing elements, as well as teeth from polymeric materials.An indispensable condition for choosing a surfaced prosthesis is the presence of the roots of individual teeth or implants, which can serve as a support.
Important: The choice of design type depends on the functional state of the remaining units of the dentition.With considerable mobility and pronounced atrophy of the bone of the alveoli, removal can be indicated, followed by the manufacture of a complete prosthesis.
Complete denture prostheses are shown with adentia( no teeth).To fix them, several implants must be pre-implanted.
Partial models are shown when individual roots are stored.
Note : many dentists reasonably believe that for implant prostheses it is advisable to use implants as a support."Native" teeth will not last long.
Special reinforcing meshes or clasp skeletons can be used to increase strength in structures.It should be noted that the latter greatly increase the overall weight of the prosthesis.
Indications for the manufacture of cover prostheses
Indications for the manufacture of orthopedic structures of this type are:
- abrasion abrasion;
- need to remove the supragingival part( crown) of the tooth;
- fracture of the crown;
- dryness of the oral mucosa( xerostomia);
- marked emetic reflex in the patient;
- atrophy of the jaw bone( with preserved roots);
- availability of contraindications to other types of prosthetics.
Unfortunately, there are a number of contraindications that do not allow the use of a partial or full cover denture.
- lack of root parts of the teeth and the impossibility of installing implants;
- poor blood clotting;
- pathology of the cardiovascular system;
- of the nervous system.
Advantages and disadvantages of cover prostheses
Cover prostheses are virtually an alternative option for pathological abrasion of tooth enamel.The unique structure of this category provides a uniform distribution of load between the supports( implants or preserved roots), which minimizes discomfort during adaptation to the prosthesis.In this case, the pressure on the mucous membranes of the gums is minimal, which prevents their inflammation and atrophy.
Installation of the construction does not require a preliminary build-up of bone tissue, which significantly reduces the time of orthopedic treatment.These types of dentures provide a uniform load when chewing, close to the physiological, which stops the process of resorption( loss) of the bone tissue of the alveolar processes.As a result, cover models have to be changed much less frequently.
It should also be noted that the period of habituation to new dentures in most cases is very short.The structure of the basis( reduction of its boundaries on the upper jaw) makes it possible to use such models even for those patients who have a strong gag reflex.Also it is possible to note reliability of fixation of dentures of covering type and their high aesthetic qualities.
The minuses of these models are their relatively high cost, as well as the need for regular implementation of preventive cleaning of the prosthesis.It can also be noted that it takes quite a long time to design a patient that is ideally suited to the patient.
Materials used in the manufacture of
The quality and cost of the materials used in the manufacture of cover prostheses depends.
The universal material has not yet been created, therefore several designs are often present in one design.
Acrylic cover trims
Acrylic is a kind of polymer material( plastic).It is excellent for the production of orthopedic structures, since it is characterized by a high degree of strength.Acrylic does not deform with time, so that only a single support in the form of an implant can be sufficient for the prosthesis.The undoubted advantage of this polymer is its low cost.
Cons of designs from such plastic is their fragility and low aesthetic characteristics( hard basil acrylic imitates soft tissues of the oral cavity badly).The material is fairly porous, which requires frequent and thorough cleaning of the structures.For the production of inexpensive artificial teeth, it fits as well as possible, but the basis is recommended to be made of nylon.
Nylon Coverings Elastic nylon bases of the overlying dentures are very similar to the real mucosa;They repeat the shade and texture of these soft tissues.The structures of this polymer are very flexible;While they are not completely deformed.The strength of the material makes it possible to wear such prostheses for many years.By the degree of elasticity, nylon is even compared with silicone( a kind of artificial rubber).
It should also be noted that cases of allergic reactions to this polymer are extremely rare.Prostheses with nylon bases are not afraid of accidental falls, which distinguishes them from acrylic models.
The disadvantage can be considered unless a relatively high price.
Of the durable metal( in particular - titanium) alloys, individual elements of prostheses are used, which are necessary for fixing or increasing the rigidity of structures.For the production of bases and even artificial teeth of removable prostheses, metal is completely unsuitable.
Types of fixation of cover prostheses
Telescopic crowns, beams and retainers can be mounted on the supporting teeth( roots).The choice of design depends on the functional state of the unit of the dentition and the number of supports used to fix the prosthesis.
Fixation of removable prostheses of the covering type is often carried out by means of a root attachment - a locking fastening from two metal fragments( matrix and patrician).Such systems are considered the most reliable.The indication for the use of attachments is the atrophy of the bone tissue of the alveoli not more than half the length of the root.
The principle of magnetic fixation, as the name implies, is based on the magnetic attraction of fragments of the orthopedic structure.
Telescopic( i.e., removable) crown at the same time allows to restore the shape of the supragingival part of the tooth and to ensure a firm fixing of the covering structure.Such crowns, which are part of the prosthesis, are worn on prepared stumps of teeth.To ensure reliable fixation, special adhesive compositions have been developed.
Magnetic retainers and crowns are necessary if the bone tissue of the alveoli is resorbed by more than ½ the length of the root.
Very widely used are fastening elements, such as clamps.They can be made of the same material as the base or are metal hooks that are rigidly mounted in the base.These fastenings fit the supporting tooth in the cervical region.Clamping is very reliable, and the design itself is relatively simple to manufacture, but the hooks are noticeable, that is, the aesthetics obviously suffer.To make these elements less visible, they often resort to coloring them in pink or white.
Implants are rodlets with thread( "screws"), which are implanted in the bone tissue of the jaws.The technology of their installation is perfected, which minimizes the probability of rejection.
A beam construction of two or more implants connected after engrafting with a metal arc can be used to fix the overlying prosthesis.This design provides a very large support area for the basis.
Push-button implants are less complicated.On the upper part of the implanted rod there is a ball, and on the covering prosthesis there is a "mating part" in the form of a groove with a metal ring around the circumference.
Important: and can be used as a support for a single overlying prosthesis and retained own teeth and implants.The degree of their mobility is significantly different, since the amortization of the native tooth is provided by the ligament apparatus, and the titanium rod after implantation is held rigidly in the bone.
Innovative technology "all-on-four" is widely used in the manufacture of modern covering dentures, which involves fixing the entire artificial row on four implant supports.
Some features of preparation for prosthetics
In some cases, patients during the preparation for prosthetics can be shown surgical intervention - gingivectomy.The operation that is performed in the clinic, usually under local anesthesia, involves the elimination of pathological periodontal pockets, which makes it possible to increase the length of the supragingival part of the tooth.According to the indications, the bridle or connective tissue strands of the mucosa may also be removed.
Timely prosthesis allows to prevent or at least suspend atrophy of bone tissue and a number of pathological changes from the chewing and mimic muscles.
Plisov Vladimir, dentist