Compositions: coating or plastic – Coating or plastic compositions – Dental
Patent
1997-04-02
1999-04-06
Reamer, James H.
Compositions: coating or plastic
Coating or plastic compositions
Dental
4332151, 433 78, 501 24, 501 25, 501 57, 501 58, 501 63, 501 72, C03C 3078
Patent
active
058912339
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/FI95/00539, filed Oct. 2, 1995.
The aim of this invention is to introduce a novel use of bioactive glass and new preparations comprising bioactive silica containing glass. The said preparations can be used for reinforcing a tooth and for closing the dentinal tubules in the dentine in order to reduce pain transmitted to the pulp as a consequence of open tubules.
BACKGROUND OF THE INVENTION
Dentine forms the frame of a tooth. It surrounds the pulp and is covered by enamel on the crown and cementum on the root. The cementum does not always meet the edge of the enamel at the cementum-enamel junction. In such cases, dentine, which is not protected by another type of hard tissue, is exposed at the neck of a tooth. In the young, this area is usually covered by gingiva which covers this particular zone of dentine and prevents its exposure to irritation from the oral cavity.
Dentine consists of an extracellular matrix, which is formed by odontoblasts lining the pulp cavity. When dentine is formed and it becomes thicker, each odontoblast leaves behind a cell extension i.e. an odontoblast process. These processes remain inside the developing tissue and form dentinal tubules, which extend from the enamel-dentine/cementum-dentine border into the pulp. When exposed, open dentinal tubules form a link between the dentine surface and the pulp.
The structure of dentine is shown in detail in FIG. 1.
Once the tooth has stopped growing, odontoblasts continue their function and form secondary dentine on the pulp side of the tooth. They also form hard tissue i.e. intratubular dentine which gradually closes the tubules around the receding odontoblast processes (FIG. 2.). The level of mineralisation of intratubular dentine is significantly higher than that of intertubular dentine. The mineralisation of dentinal tubules is a very slow but natural process, associated with the ageing of a tooth. The slow pace and unpredictability of the process are manifested as problems in various clinical situations.
The hydrodynamic pain transmission mechanism of exposed dentine can be described as follows:
Dentinal tubules are 1-2 .mu.m in diameter. When a section is cut perpendicular to the dentine surface, there are around 30 000-40 000 dentinal tubules per mm.sup.2. A dentinal tubule is filled with an odontoblast process, surrounded by fluid from the pulp. A very strong capillary force prevails in open and exposed dentinal tubules. Consequently, fluid mechanically removed from the opening of the tubule is quickly replaced by fluid flowing out from the pulp. Similarly, substances with strong osmotic pressure (e.g. sweet solutions) cause an outward flow of fluids in the tubule, which in turn, leads to transformations of the odontoblasts lining the pulp chamber and tissues surrounding ondontoblasts, thus activating the nerve endings. On the other hand, irritation transmitted to the pulp may be caused by the inward flow of the fluid in the dentinal tubule. In practice, the hydrodynamic mechanism refers to the fluid flow in a dentinal tubule caused by a stimulus and the resulting hydraulic vibration in the pulp. According to current opinion and experience, the closing of the tubule and the resulting complete or partial prevention of fluid flow would lead to a reduction or even elimination of nerve activation, sensed as pain regardless of the primary stimulus (1). The pain transmission mechanism is illustrated in FIG. 3.
The exposure of dentine and dentinal tubules leading to the pulp may be the result of caries. The hard tissue (enamel/cementum) protecting the dentine is destroyed during the decay process. The situation leads to the known painful symptoms associated with cavity formation. The pain results from irritation which is transmitted to the pulp nerve endings through the dentinal tubules. During the decay process, partial mineralisation of tubule contents is usually observed. This is a consequence of the high calcium and phosphate ion concentration caused by demineralisation processes of the enamel and de
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patent: 5735942 (1998-04-01), Litkowski et al.
Plastics That Don't Last, New Scandinavian Technology, Nov. 4, 1992.
Salonen Jukka
Tuominen Ulla
Yli-Urpo Antti
Bioxid Oy
Reamer James H.
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