Method and apparatus for determining the preload for screws for dental implant systems

Abstract

A method and apparatus are provided for determining the preload in a dental implant system. The preload is determined by transmitting a sonic impulse, which is preferably an ultrasonic impulse, at a predetermined frequency to the head of the implant screw through a transducer, which may be incorporated into the head of the screw, the head of a wand which generates the sonic impulse, or the transducer and pulse-generating instrumentation may be incorporated into a torque generating instrument used to tighten the screw. The preload is determined by measuring the delay between the first and second reflections through the preloaded screw to determine a preload value and comparing that value with a pre-established baseline value for the screw, and comparing the difference with a predetermined table of values to determine the preload on the screw.

1 . A method of determining the pre-load on a screw that secures a component to other components in a dental implant system comprising:
 Transmitting a sonic impulse at a predetermined frequency to the head of the screw through a transducer when the screw is in an unstressed condition;   Measuring a first delay between first and second reflections through the unstressed screw, and establishing a baseline value for the unstressed screw;   Applying a preload of a predetermined value to the screw to secure implant components together;   Transmitting a sonic impulse at a predetermined frequency to the head of the preloaded screw through a transducer;   Measuring a second delay between the first and second reflections through the preloaded screw to establish a preload value; and   Determining the difference between the first delay and the second delay to establish a difference between the baseline value and the preload value, and comparing the difference with a predetermined table of values to determine the preload on the screw.   
   
   
       2 . The method of  claim 1  wherein the sonic impulse is an ultrasonic impulse. 
   
   
       3 . The method of  claim 1  wherein the screw secures an abutment to an implant. 
   
   
       4 . The method of  claim 1  wherein the screw secures a dental prosthesis to an abutment. 
   
   
       5 . The method of  claim 1  wherein the screw secures a dental prosthesis directly to an implant. 
   
   
       6 . Apparatus for determining the preload on a screw in a dental implant system that includes at least one screw for securing components of the dental implant system together, wherein the dental implant system includes at least a fixture having one end adapted for osseointegration into a jawbone, the other end adapted to receive an abutment, and the abutment adapted to receive and support a dental prosthesis, the apparatus further comprising
 Means for applying a preload to the screw to secure at least some components of the implant system together;   Means for transmitting a sonic impulse at a predetermined frequency to the head of the screw;   Means for transmitting the sonic impulse through the screw and detecting first and second reflections of the pulses;   Means for measuring the delay between the first and second reflections through the preloaded screw to determine a preload value; and   Means for determining the difference in the delay between a pre-established baseline value for the screw and the preload value, and comparing the difference with a predetermined table of values to determine the preload on the screw.   
   
   
       7 . The apparatus of  claim 1  wherein the sonic impulse is an ultrasonic impulse. 
   
   
       8 . The apparatus of  claim 1  wherein the screw secures an abutment to an implant. 
   
   
       9 . The apparatus of  claim 1  wherein the screw secures a dental prosthesis to an abutment. 
   
   
       10 . The apparatus of  claim 1  wherein the screw secures a dental prosthesis directly to an implant. 
   
   
       11 . The apparatus of  claim 1  wherein the means for transmitting a sonic impulse is an apparatus that produces an ultrasonic impulse. 
   
   
       12 . The apparatus of  claim 1  wherein the means for transmitting the sonic impulse through the screw and detecting first and second reflections of the pulses is a transducer. 
   
   
       13 . The apparatus of  claim 12  wherein the transducer is affixed to the head of the screw. 
   
   
       14 . The apparatus of  claim 12  wherein the transducer is affixed to a wand, and the wand is in electronic communication with an electronic control and measurement circuit.