Note: Descriptions are shown in the official language in which they were submitted.
106813~
The invention relates to a dental reinforcing pin for -
use in the anchoring of a superstructure to a tooth understruc-
ture.
In the restoration of a badly decayed tooth a super-
structure of amalgam or composite is built on to the sound den-
-. tine understructure of the tooth. Various dental reinforcing
pins have been used for anchoring the superstructure to the under-
structure.
It is known to employ a dental reinforcing pin compris-
ing at one end a threaded portion for self-tapping insertion in
a drilled hole in a tooth, the pin at the other end having a con-
necting portion provided with means for engagement with a manually
operated screw-driver. A reduced diameter neck is provided be-
tween the connecting portion and the threaded portion so that the
connecting portion will automatically shear off from the threaded
portion when the latter reaches the bottom of the hole. Such a
pin suffers from the disadvantage that due to the flange and
slot connection between the pin and the screw-driver there is
the danger that the pin will dislodge from the screw-driver dur-
ing the insertion and fall into the patient's mouth with perhaps
, serious consequences if swallowed. Such danger also occurs in
the modification of this pin in which the threaded portion is
in two sections joined by a further neck. Furthermore, in both
cases the insertion procedure is cumbersome.
It is also known to connect the above type of pin with ;a separate chuck which is then itself loaded in a dental hand-
piece for mechanical insertion of the thread portion. The flange
and slot connection between the chuck and the pin gives rise to
the same danger of the pin falling into the patient's mouth dur-
ing insertion and the insertion procedure is time-consuming.
~- It is a feature of the present invention to provide an
improved dental reinforcing pin which substantially overcomes the
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above mentioned disadvantages. -~
Accordingly, from a broad aspect, the present inven-
tion provides a dental reinforcing pin comprising a threaded
portion for self-tappin~ insertion in a bore formed in a tooth
under-structure, a connecting portion comprising a shank section,
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and a weakened portion intermediate the threaded portion and
one end of the shank section for permitting shearing and separa-
tion of the shank section from the threaded portion, said shank
section having a free end shaped to cooperate with locking means
on a dental hand-piece so that said pin can be locked to said
hand-piece.
The invention will now be described with reference to
the accompanying drawings which show a preferred form thereof
and wherein:
Figure 1 is a side elevation of a dental reinforcing
pin machined from stainless steel wire,
Figure 2 is an end elevation of the dental reinforcing
pin; and
Figure 3 is a side elevation of another embodiment of
the dental pin.
Referring now to Figures 1 and 2, the dental reinforc-
ing pin has a screw-threaded portion 10 at one end thereof. The
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threaded portion 10 may have an outside diameter of 0.76 mm and a
length of 4 mm. Formed integrally with the threaded portion 10
is a connecting portion 11 comprising an elongated circular-cylin-
drical shank 12. The diameter of the shank 12 is larger than that
of the threaded portion 10 and is such that the shank will be an
easy sliding fit in a standard dental hand-piece. The shank 12
is shaped at its free end, providing a segmental cut-away portion
13 and part-annular groove 14 so that the shank 12 can co-operate
with the latch mechanism of a latching-type dental hand-piece and
be locked thereby. The end of the connecting portion 11 adjacent
the threaded portion 10 is constituted by a frusto-conical por-
tion 15. Intermediate the threaded portion 10 and the connecting
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portion 11 is a reduced diameter portion or neck 16 having a
~, diameter less than the root diameter of the threaded portion 10
so as to provide a fracture or shear portion.
In operation, the carious matter is removed from the
surface of a broken-down tooth leaving a sound dentine understruc-
ture. A hole is drilled in the dentine in well-known manner with
a dental drill. The reinforcing pin is loaded in a latching- ~
type contra-angle dental hand-piece by sliding the shank 12 into ~ !`
the hand-piece and locking it with the latch on the hand-piece.
The threaded portion 10 and the frusto-conical portion 15 now
project clear of the barrel of the hand-piece. The hand-piece
drive, comprising an air motor or other known means, is now
operated, causing rotation of the dental pin. The reinforcing
pin is now aligned and engaged with the drilled hole, the frusto-
conical portion 15 aiding visibility. The reinforcing pin will
now advance in self-tapping manner in the drilled hole which has a
diameter slightly less than the thread diameter so that a good
anchorage is obtained by the inter-engagement of the thread on
the pin and the thread formed in the dentine. When the pin has
penetrated to the bottom or nearly the bottom of the hole so that
resistance is met to further movement, the neck 16 automatically
shears so that the connecting portion 12 is separated from the
threaded portion 10. The depth of the drilled hole can be chosen
so that when the shear-off point is reached, for example half the
length of the threaded portion 10 extends into the dentine and the
remainder projects from the tooth understructure. The connecting
portion 11 can now be released from the hand-piece and discarded.
Finally, the tooth is built up with an amalgam or composite supér-
structure around the threaded portion in known manner. :
It will be apparent that the reinforcing pin described
above is very safe in use in that the pin is securely locked to
` the hand-piece during the insertion and thus the danger of the pin
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falling into the patient's mouth is minimized. Furthermore, the
described pin enables the operation of inserting a threaded por-
tion in a tooth to be per~ormed quickly and easily.
Referring to Figure 3, a threaded portion comprises two
equal sections 20 and 21 joined by a neck 22. A neck 23 is pro-
vided intermediate the threaded section 20 and the connecting
portion 11. The neck 22 has a slightly smaller diameter than
that of the neck 23. The reinforcing pin is operated in the
same manner as the first described embodiment except that shear
will first occur at the relatively smaller diameter neck 22 so
that the connecting portion 11 together with the threaded section
20 separate from the threaded section 21. The hand-piece holding
securely the threaded section 20 can now be aligned with a second
drilled hole in a tooth. Operation of the hand-piece now causes
self~threading insertion of the pin in the second hole and when
the pin reaches the bottom of the hole, shear occurs at the neck
23 so that the connecting portion 11 separates from the threaded
section 20. By this means, threaded portions can be inserted in
two drilled holes without the need to re-load the hand-piece.
In another embodiment of the invention, part of the
connecting portion remote from the threaded portion is formed
from a material different from that of the threaded portion and
is moulded to the remainder of the pin to form an integral struc-
ture.
The free end of the connecting portion may be shaped in
a different way from that described above to co-operate with lock-
ing means on the hand-piece so that the dental pin is locked to
the hand-piece.
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