Dentistry – Method or material for testing – treating – restoring – or... – Anchor pin
Patent
1994-05-23
1996-01-09
Lucchesi, Nicholas D.
Dentistry
Method or material for testing, treating, restoring, or...
Anchor pin
A61C 504
Patent
active
054824656
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a dental pin assembly which comprises a dental pin for anchoring dental superstructures e.g. caps, veneers, onto a tooth, and a dental pin holder to facilitate the handling of the dental pin by the dental surgeon.
In particular, the present invention relates to dental pin assemblies in which the dental pin is a threaded pin and is for self-tapping insertion into the dentine of the tooth. Such pins commonly have a threaded portion which is releasably connected to a shank portion through a low shear neck portion. The threaded portion of the pin is inserted into the dentine to a pre-determined level at which a resistance to rotation is established, and any rotation against this resistance then provides sufficient torque to shear the pin at the neck portion. Shearing of the neck portion leaves a portion of the pin projecting from the surface of the dentine to which a dental superstructure can be secured.
Prior art threaded pins have had their threaded portions formed by precision machining, with further machining to provide the low shear neck portion. A significant disadvantage with machining to form the threaded portion of the pin is that a large amount of raw material is wasted, and since the materials used to make dental pins tend to be very expensive the cost of manufacturing pins by this process is very high.
The small dimensions of dental pins necessitate the use of a dental pin holder to facilitate handling and fitting of the pin into the dentine of the tooth. These holders typically comprise a cylindrical body which has a longitudinal central bore into which the shank of the dental pin is slid and subsequently secured therein. The central bore can be open at both ends or closed at one end depending upon type of method used to secure the shank within the bore.
The shank can be releasably or permanently secured within the bore, but permanent securement is preferred since releasable attachments used in the past have proved to come undone during fitting of the dental pin. A wide variety of methods for permanently securing the shank of the dental pin within the bore of the dental holder are known, examples of which are described in GB 1482681, EP 179599 and EP 56198.
The holder can be part of a standard dental hand-piece to be used manually by the dental surgeon, or more commonly the holder is for releasable attachment to an automated device capable of rotating the entire dental pin assembly.
Once the dental pin has been sheared at the neck portion as described above, both the shank and the holder are disposed of. It is therefore desirable that the holder be made of a relatively cheap material, and that the volume of the shank is as small as possible to reduce the ultimate cost of the dental pin assembly as a whole.
SUMMARY OF THE INVENTION
According to the present invention, a dental pin assembly comprises a dental pin holder and a dental pin, wherein receiving the dental pin and characterised in that substantially uniform diameter by rolling one end of the pin to form the threaded portion and by machining to form the shearable neck portion, and shank portion or the bore or both having been permanently distorted into interengagement while the shank portion is in the bore.
The present invention also provides a method for making the dental pin assembly described above, wherein the method comprises the steps of dentally acceptable wire of substantially uniform diameter, portion unrolled and substantially straight to form the shank portion of the pin, and shearable neck portion of the pin, and permanently securing the shank therein by distorting the shank portion or the bore or both into interengagement.
Rolling is a well known technique used to physically deform lengths of metal into threaded structures. Basically the process involves rolling a length of metal, the stock, between at least two rollers. The rollers bear onto the stock with considerable force and deform the metal crystalline structure, and this results in the formation of a thread. Rollin
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