By Joseph J. Massad, DDS
Welcome back! This month's tip involves a method of utilizing a new implant impression coping that has been thread timed. This allows the prosthetic lab technician to correct angle alignment when stud abutments are being utilized. With the U.S. economy in flux, we have seen an increase in stud abutment restorations being chosen over the higher cost of bar-retained prostheses. In most cases, in order to place multiple stud type abutments relatively parallel, the dentist was required to perform chairside angle correcting, either with a screw-retained or a cementable, pre-angled selection.
The new thread-timed implant level closed impression copings now allow dentists a choice to align at chair time – which may be more costly – or to send the impression to a lab to have the correction performed. Each practitioner must decide which process is best for both quality efficiency and cost. Also, each practitioner must take into account those frustrating times when a chairside procedure has gone south and both the dentist and the patient are unhappy.
In Figures 1a and 1b, the patient decided on the lower cost of a stud abutment overdenture due to financial concerns. With the number of implants along with the amount of angulation between the implants, it was necessary to utilize an angling abutment system
to improve the parallelization. Figure 2a shows the most common angles attached to alignment angles to be cemented into the open cylindrical abutment seen in Figure 2b. In Figure 3a, the male angles are inserted into the abutment. Figure 3b depicts angles that have been rotated to an optimal position. Figure 4 was done chairside, which is tedious and not necessarily financially feasible. Figure 5
displays the thread-timed impression copings (Sterngold, Attleboro, MA) numbered and then placed into the implants. The final impression is shown in Figure 6 and sent to the lab where a soft tissue model was made as part of the pour-up procedure so the
correct sulcus heights could be chosen. This was followed by aligning the male angles to be cemented and delivered back to the dentist to be inserted in one step into the mouth (Figure 7). Dentists now have additional options to consider.