Torque Ratchet Tool Particularly Useful With Endosseous Dental Implants

This invention relates generally to surgical and prosthetic tools used to deliver and assemble screws and abutments into dental implants and related components and particularly to precalibrated dental torque ratchet wrenches.

The invention addresses problems associated with the delivery and assembly of abutments screws into dental implants and related components using a conventional torque ratchet wrench. Most dental implants currently used are manufactured with a bore having an internal machine screw thread to accept and retain an abutment or prosthetic screw. However, due to the intrinsic nature of a thread design, if components are not assembled with the system's required tunctional torsional preload, the abutment or screw will loosen from the implant. Once loose, the abutment or screw is at risk of failure as all the functional loads end up being applied directly to the thread itself.

To prevent such thread attachment from coming loose, the prosthetic restoration is assembled into the implant with a torsional preload to resist the opening of the assembled joint during normal functional loading, i.e. chewing. This assembly is accomplished by using a torsional screw driver or wrench. As a means to regulate the applied preload of the assembled joint, the industry has developed several, spring actuated, mechanical break-a-way neck hand held torque wrenches. In addition to providing the assembled implant/prosthetic joint with the correct pre-load for eliminating joint separation, these break-a-way torque wrenches are used to prevent stripping or fracturing of the screw thread or overloading the implant during assembly.

Although these tools meet the stated functional requirements, continuous wear of the internal moving parts of the break-a-way head, due to their mechanical design, causes such tools to drift out of calibration over time and use. In fact, information accompanying most of the vailable tools state that the tools must be recalibrated at least once a year as part of the maintenance program for the tools. Since these tools use a mechanical spring to apply the desired application of torque, sterilizing the tools with steam autoclaving has lead to corrosive binding ot the break-a-way neck. Once locked, these wrenches are unable to control the application torque applying the preload. Furthermore, based on the predetermined application preload needed to prevent opening of the assembled implant/prosthesis joint, an uncontrolled variation in the application torque may lead to fracture or failure of the prosthesis. These conditions give rise to concerns for these tool's long term replacement costs, dependable function over time, sterility requirements and overall reliability.

An object of the present invention is to provide a tool which overcomes the above noted deticiencies in the prior art at a reasonable cost to the industry. Another object of the invention is to provide a torsion application tool that consistently applies the desired predefined application torque. It is a further object of the invention to provide a tool that is not subject to constant recalibration requirements or sterility issues and one which can be used predictably over time. it is a further object of the invention to provide a tool which meets the size requirements for use in oral cavities.

Briefly, in accordance with the present invention, a torque ratchet tool, having a pivot arm driver handle, houses a precalibrated disposable insert which transfers an applied force to consistently deliver a predetermined torque application and correctly preload the prosthetic attachment to the implant. Each disposable insert is manufactured from a plastic material that has been machined to a specific dimensional size and fractures at a predefined application torque. The invention solves the problems of calibration requirements and allows the users to effectively apply the predetermined seating torque in a sterile, cost effective, simple, easy to use and functionally reliable manner. Additionally, if the pre-defined application torque is not necessary, a solid metal insert can be used and the tool will function as a straight ratchet tool. These and other objects and features will become apparent from the following description taken together with the accompanying drawings in which like reference numerals refer to like parts throughout the several views.

FIG. 1 is a top plan view of a torque ratchet tool made in accordance with the invention,

FIG. 2 is a front elevational view of the FIG. 1 tool, with a portion shown in cross section,

FIG. 3 is a bottom plan view of the FIG. 1 tool,

FIG. 4a is top plan view of a precalibrated insert usable with the FIGS. 1-3 tool,

FIG. 4b is a side elevational of the FIG. 4a insert,

FIG. 4c is a front elevational view of the FIG. 4a insert and

FIG. 4d is a top plan view of a nonfrangible insert useful in the FIGS. 1-3 tool,

FIG. 5 is front elevational view of a driving tool useful with the FIGS. 1-3 tool,

FIG. 6 is a top plan view of a standard ball bearing driver ratchet head used in the FIGS. 1-3 tool and shown in greater detail than in FIGS. 1-3,

FIG. 7 is a front elevational view, partly in cross section of the FIG. 6 ratchet head,

FIG. 8 is a blown apart elevational view of the FIG. 7 ratchet head, and

FIG. 9 is a top plan view of separate portions of the pivot arm driver handle shown in FIGS. 1-3.

With reference to FIGS. 1-3 a torque ratchet, in the form of a driver head and handle 8 is made up of a standard ball bearing driver ratchet head 10, a pivot arm driver handle 12, and a plastic disposable break-a-way insert 14 (FIGS. 4a-4c). Ratchet head 10, shown in greater detail in FIGS. 6-8, comprises an outer casing 16, an internal ratchet square driver ring 18, ball bearings 18a and an assembly inner casing 20. Incorporated into the inner drive ring 18 of the ratchet head is an internal driver square 18b that is formed in the inner drive ring and accepts the standard square driving tool 24 for screwing down, or unthreading, an abutment or prosthetic screw. Also incorporated in the inner drive ring 18 is a tool holding and driving spring 26 used to snap over and secure the standard square driver tool 24. An internally formed square 10a and a tapped cross hole 10b are located in the center of the assembled ratchet head 10 as a means for attaching head to pivot arm driver handle 12.

The pivot arm driver handle 12 is made up of two independent components, the main driver arm 30 and the ratchet head attachment arm handle 32. A pair of spaced ears 30a and contiguous ear seats 30b (see FIG. 2) are formed at a distal end of driver arm 30 which interdigitate with a complimentary pair of spaced ears 32a and contiguous ear seats 32b formed at a distal end of arm handle 32. These two independent ratchet arm handle components are securely assembled using two press fit fixation pins 34 pivotably received through respective bores 30c in ears 30a and press fit in respective bores 32c in ears 32a. The main driver handle 30 is machined with a medium knurl 30d and a defined radius groove 30e for easy functional use. A half center groove or recess 30f, 32f, respectively, is formed intermediate to the ears and ear seats of each respective pair of driver arm 30 and arm handle 32 to form an insert receiving chamber 12a (FIG. 2). The assembly of these two handle components, 30 and 32, with the press fit fixation pins 34 allow the assembled ratchet arm handle 30 to pivot freely, relative to attachment arm handle 32, in a singular 60 degree angular clockwise direction limited by the interaction of stop surfaces 30g, 32g as seen in FIG. 1. At the opposite end of the ratchet head attachment arm handle 32 is a machined square 32h that locates and snaps into the mating broached square 10a of the assembled ratchet head 10. This defined snap connection 32h and 10a together with the tapped cross hole 10b on the assembled ratchet head 10 allow a user to remove the pivot arm driver handle 12 and use the ratchet head as a finger driver.

The assembled torque ratchet wrench handle has been designed to deliver a precalibrated application torque by inserting a plastic, disposable break-a-way insert 14 into the assembled chamber 12a of the pivot arm handle. Insert 14 is machined with a selected, defined center groove 14a that is specific to the required application torque. Once the defined torque is reached by the ratchet tool, the insert 14 will fracture at its reduced depth center 14a and the main driver handle 30 will break-a-way and rotate freely up to 60 degrees in the clockwise direction as seen in FIG. 1.

A selected color pigment can be given to each plastic insert as a means of identifying the defined torque application. To guarantee that the plastic insert 14 delivers the precise application torque, the assembled grooved area 12a is machined with a defined stop 30i, 32i respectively, to center the insert 14 in the assembled pivot arm area. If a predefined application torque is not necessary, a solid metal insert 14', shown in FIG. 1d, can be used and the tool will fimction as a straight ratchet wrench.

The invention may take on other various forms without departing from the spirit or essential character thereof and the disclosed embodiment is meant to be illustrative and not limiting, the scope of the invention being indicated by the appended claims.