By Joseph J. Massad, DDS
Welcome back! Today, I would like to address a question that I am repeatedly asked at many of my presentations … Are verification jigs really needed for successful implant-supported prostheses?
In a perfect world, every implant-retained stud attachment, bar, or fixed prosthesis would have a passive fit without introducing stress into any implants and their surrounding structures when being loaded while functioning. I will attempt to address this very important prosthetic reality in a three-part series to adequately deliver a practical protocol that has been very rewarding in my practice.
To begin part one, I will ask those of you who are interested to answer the following questions in order to be able to qualify an appropriate answer. Please email me with your reply at [email protected].
What type of appliance are you fabricating … Stud retained, bar retained, or fixed denture?
How many implants are involved and what is the span and spacing between them?
How do the implants line up three dimensionally as far as overall parallelism between each other?
Are you using an open or a closed impression tray technique?
What impression-making method are you utilizing ... Single entry or multiple layer entry?
Do you control the thickness of the impression material around intended surfaces?
Have you researched the accuracy of impression materials you are using or just accepted claims from the manufacturer?
Are you following the manufacturer's directions for use or using off label?
What viscosity or viscosities of material are you using and where?
What method and materials are you or your technician utilizing to fabricate the stone cast?
Do you know the coefficient of dimensional change of the cast materials?
Do you or your technician use a containment method to pour your cast?
What is the chemical makeup of the verification material you or your technician is presently utilizing in the fabrication of the verification jigs?
What method are you using to fabricate the verification jig … Single-stage build and cure or segmental connecting cure?
These questions and others have been studied over the years to eliminate error without a perfect solution.
From my experience (and in reviewing various articles and studies over the years), I have concluded that the very first step is to be in complete control of the impression process from the outset. Next month, I will discuss a protocol for a highly precise multiple implant impression utilizing a friendly calibratable method and a new enhanced impression polymer chemistry conducive to the multiple implant impression procedure. I will also qualify the various viscosities as to their intended impressioning surface use. The following month's issue will focus on a model casting procedure designed to further improve accuracy for an optimal passive prosthetic fit. Finally, I will conclude this series with the fabrication of a well thought out method of assembling a precise confirmation jig.
I hope to hear from you soon and remember to email me your answers to my questions so I can add them to my column in the next issue of Dental Economics.
See you next month. I hope my pleasure in dentistry will also be yours.
Joe Massad
Dr. Joe Massad may be reached by phone at (918) 749-5600 or by e-mail at [email protected].
To see Dr. Massad's video tips, visit www.DentalLibrary.com
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