Converter assembly for threaded dental implants

A converter assembly for converting a dental implant having a threaded bore is shown having a cylindrical converter pin (22) with one end portion (24) threaded for reception in the threaded bore of the inplant. An opposite end portion (26) is formed with a locking taper which is receivable in a bore (34) of an abutment member (30) having a matching locking taper.

This application claims priority based on provisional application No. 
60/036,502 filed Jan. 28, 1998. 
BACKGROUND OF THE INVENTION 
This invention relates generally to restorative dentistry and more 
particularly to dental implant systems. A common type of dental implant 
system comprises a generally cylindrical body made of biocompatible 
material and is formed with an outer surface configuration selected to 
promote osseointegration. For example, a plurality of fins which extend 
radially outwardly from the side wall of the body or an external thread 
formed in the side wall. A bore extends through a crestal end of the body 
along the longitudinal axis of the cylindrical body with at least a 
portion of the bore having an internal thread adapted to threadingly 
receive a variety of threaded copings, screws or other threaded posts of a 
dental prosthesis system. 
One of the difficulties in using a threaded member to attach a prosthesis 
to the implant is the need for tight and lasting engagement of any 
threaded member received in the bore as well as the need for attaining a 
selected angular orientation, that is, the tooth simulating prosthesis 
must be positioned in a precise, given angular orientation. Any looseness 
between the components can eventually result in breakage due to the 
lateral forces placed on the components during chewing. 
Another type of dental implant system has a smooth circular bore formed 
with a locking taper for reception of a post of an abutment having a 
matching locking taper. A system of this type is described and claimed in 
U.S. Pat. No. 4,738,623, the subject matter of which is incorporated 
herein by this reference. This type of system has several inherent, 
distinct advantages over the threaded system described above including the 
ability to precisely position an abutment in any selected angular 
orientation and, once tapped into locking engagement, characterized in 
having complete absence of motion between the implant and the abutment 
member. This results in fewer implant failures. Yet another advantage of a 
locking taper system is that a locking taper connection forms a bacterial 
seal as opposed to a threaded system which inherently has a space between 
the male and female threads which can be accessed by bacteria. Thus the 
locking taper system results in better soft tissue health in tissue 
proximate to the implant site. 
It would be desirable, particularly in situations where a user of a 
threaded system who has had problems with implant failures involving 
breakage of the abutment member, to be able to convert from a threaded 
system to a locking taper system however, using presently available 
procedures and components, this requires removal of the threaded implant 
and replacement with a locking taper implant with a concomitant healing 
period of some months. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide apparatus for 
converting a threaded implant system having critical angular orientation 
requirements for the positioning of an abutment while at the same time 
providing a rigid attachment between the abutment and the implant to a 
system in which an abutment can be easily oriented and securely attached 
to the implant. It is another object to overcome the prior art limitations 
noted above. 
Briefly described, in accordance with the invention, an elongated converter 
pin is provided with an external threaded portion at one end portion and a 
locking taper at an opposite end portion. The length of the converter pin 
is selected so that the locking taper portion extends out of the threaded 
implant when the threaded portion of the converter pin is completely 
screwed into the threaded bore of the implant. An abutment component is 
provided with a bore formed with a matching locking taper extending into a 
base portion thereof. The converter pin is threaded into the implant bore, 
preferably cemented therein, and the abutment is positioned on the locking 
taper portion of the converter pin in an appropriate selected angular 
orientation and is then tapped into locking, immobile engagement. The 
abutment may be a tooth-simulating prothesis itself or, preferably, may 
have a non-circular outer, upper surface configuration suitable for 
mounting thereon a conventional tooth simulating crown or the like in a 
conventional manner. 
Additional objects, advantages and features of the novel and improved 
attachment system of this invention will be set forth in part in the 
description which follows and in part will be obvious from the description 
.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
A conventional dental implant 12 is shown comprising a generally 
cylindrical body made of biocompatible material having an outer surface 
configuration suitable for promoting osseointegration when placed in a 
prepared bore in the aveolar ridge of an individual. As shown, implant 12 
is formed with an external thread 14 for this purpose however other 
configurations could be employed, such as a plurality of fins or the like. 
A bore 16 is formed through the crestal end 18 of the implant and is 
provided with an internal thread 20 over at least a portion of its length 
for reception of any one of various threaded members, such as copings, or 
a screw or the like of an abutment for a dental prosthesis. 
According to the invention a converter pin 22 comprises an elongated 
cylindrical member, formed of suitable material such as titanium or 
titanium alloy, preferably the same material as that used for implant 12 
and abutment 30 to be described. The converter pin has a first end portion 
24 of an appropriate diameter and is formed with an external thread 
selected to be threadingly received in bore 16 of implant 12. Converter 
pin 22 has an opposite end portion 26 formed with a locking taper such as 
that described in U.S. Pat. No. 4,738,623 mentioned above. The length of 
the converter pin is selected so that locking taper portion 26 extends 
above crestal end 18 when the pin is screwed into bore 16. An abutment 
member 30 has a base portion 32, preferably formed as a segment of a 
spherical surface and formed with a bore 34 having a locking taper 
matching that of end portion 26 of pin 22. Abutment 30 is preferably 
formed with an anti-rotational outer upper surface 36 as by providing one 
or more flat surfaces 38 so that a dental crown or the like can be fixedly 
mounted thereon in a conventional manner. It will be appreciated that 
abutment 30 may be of various types and could even be a tooth-simulating 
prosthesis itself as long as it is provided with bore 34 having a locking 
taper matching that of the converter pin. 
Once threaded end portion 24 is screwed into bore 16 and, if desired, 
fixedly cemented therein, abutment 30 can be placed on end portion 26 with 
the angular position thereof adjusted to any selected orientation and then 
tapped into locking engagement with converter pin 20. 
Although the invention has been described with regard to specific preferred 
embodiments thereof, variations and modifications will become apparent to 
those skilled in the art. For example, end portion 26 of converter pin 22 
could be formed having a bore with a locking taper for reception of a 
mating male member having a corresponding taper. It is therefore the 
intention that the appended claims be interpreted as broadly as possible 
in view of the prior art to include all such variations and modifications.