A.V. Grinev, PhD med., assistant of Therapeutic dentistry cathedra of I.M. Sechenov First Medical University
The first mentioning about pins was made by Pfaff in 1756, and the use of intra-channel pins as support of artificial crowns has probably longer history than channel sealing. The upper part of the tooth after endodontic treatment is often too short to allow normal crown fixation. In such circumstances heavily destroyed tooth can be restored only with the help of pin construction for its further orthopedic restoration (6). At present there is a large number of methods of production and use of pin constructions. While choosing one of them it is necessary to take into account the state of the tooth, its root anatomy, the type of planned restoration. In addition, esthetic requirements also play important role. These requirements to pins and materials of tooth core rebuilding have become more rigid with the appearance of transparent full-ceramic restorations.
With the appearance in 1990 of pins made of carbon fiber (4) dentists received an alternative to cast tabs or metal anchor pins due to the fact that the elasticity module of glass-fiber pins is much closer to that of tooth dentine as compared to the same parameter of metal pins (2). The important difference between more rigid metal pins and flexible pins made on the basis of resin consists in the way how the pressure from restoration to the tooth is transferred. When flexible pins are used all pressure is localized in the cervical area of the root, at the border between the crown and the tooth, while rigid pins transfer pressure to the root channel (1). Long functional unity between the root, the pin and the crown area of restoration is dependent on the cohesion of the pin structure with dentine of the root channel. Intra-channel pins traditionally may be fixed in the channel with the use of zinc-phosphate, glass ionomer or composite cement. Independently of pins used one may note current trend in adhesion fixation. Dual-cure composite cements used for fixation, unlike zinc-phosphate and glass ionomer cements, are well suited for cyclical pressure (13, 9), form better cohesion with dentine (10, 11), are poorly soluble (3, 12) and according to some data even promote strengthening of the root by binding it with the glass-fiber pin (14). The wide use of anchor pins made of carbon fiber (or glass-fiber pins) contributed to the working-out and introduction of the whole class of composite materials for the restoration of the crown tooth area – core-composite materials, which have not only high physical – mechanical characteristics and biological compatibility, but also good esthetic qualities. In addition, the use of these materials makes the process of restoration of destroyed crown tooth area much easier. Thus a modern technological chain of direct restoration of de-pulped teeth has been set up, which consists of three components: standard glass-fiber pin, composite cement for pin fixation in the root channel and core-composite material for the restoration of destroyed crown tooth area. Each link in this chain traditionally has its drawbacks which multiplying under certain circumstances may in the end leads to a failure. For example, quite often after endodontic treatment the sectional view of the root channel is not ideally circular (5). De facto, while trying to install the traditional glass-fiber pin in such channel one has to prepare the channel in order to reach ideal circular section, which leads to the loss of significant volume of tissue, or to put thick layer of cement in order to fill the space between badly adjusted pin and the walls of the root channel. Such situation may lead to cement break-up (7). In order to solve this problem one may use so-called anatomic pins: glass-fiber pins covered with a layer of light-cure composite (Anatomic Post ànd Core, RTD), which allows to make the pin’s form correspond to individual anatomy while they are put in the root channel (8). However, this in the end also leads to the tooth core rebuilding becoming more complicated and more expensive. Thus it becomes obvious that this procedure should be simplified through the introduction of a universal material combining the adhesive strength of composite cements and their manipulative features with physical and mechanical characteristics of composite restorative materials.
This problem might have been solved through the introduction of first Russian-made composite low-modulus self-cure material for tooth core rebuilding «FlowCor» (JSC «StomaDent»).
The creators of this material combined in it the positive features of composite cements and composite restorative materials.
As a result the new material has such characteristics as high adhesion to hard tooth tissues and materials of pin structures, on the one hand, and excellent physical and mechanical qualities, on the other hand. In addition, «FlowCor» has high plasticity which allows to place it in the root channel without difficulty. This combination allows to use this material simultaneously for the fixation of anchor pin in the root channel and for the restoration of upper crown area of the tooth.
In this way the process of restoring crown tooth area becomes much easier and cheaper, and besides, such restoration becomes more monolith and as a result, has higher strength.
Taking into account all the above the appearance of «FlowCor» material (JSC «StomaDent») can make the process of direct restoration of teeth crowns after endodontic treatment much easier and cheaper and at the same tine it may increase service life of these restorations.
Clinical case of tooth core rebuilding by «FlowCor» and of restoration of vestibular tooth part by «UniRest» material
Clinical case of tooth core rebuilding by «FlowCor» to prepare for metal-ceramic structure
List of sources
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