Implant Placement Q&A
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Frequently Asked questions
Q. What is the approximate distance from the inferior border of the mandible once the Sendax MDI is seated? Do I want the longest implant I can get in place without contacting the cortical bone on the inferior border? Or, do I want to be half or three-quarters the distance?
Secondly, is there any significance to the RPM’s of the bur when penetrating the cortical plate and drilling into the cancellous space? I use intraosseous anesthesia regularly and am familiar with gulary and with the feel of perforating the plate, but I am aware that most implant systems want a very slow rotation with a high-torque motor. Will a typical air-driven slow speed hand piece be okay, or do I need an electric motor with controlled speed?
A. Several good questions. First of all, there is no exact specific length or distance recommended. Rather, the basic guideline should be to take advantage of as much available patient bone as possible. You are aware, however, especially in the anterior mandible, the deep symphyeal bone can be very dense and hard to penetrate. In that event, you would be better off not trying to overdo the length issue and use a shorter MDI mini-implant rather than trying to shoot for the inferior border of the cortex. All you need is a crestal cortical penetration (using either a moderately high speed drill to break through or a slower speed drill if it can penetrate readily) down deep enough only to provide a good starter opening to introduce the self-tapping implant. Then, auto-advance it as you turn it into the medullary (cancellous) bone.
While the point is made constantly not to over-instrument the patient’s bone, it is also essential to remember that you must get a good initial penetration (at the right angulation of course) for the starter opening to work effectively. Also, even if the starter penetration is accomplished at a higher speed, it is only done for a few seconds with water spray at a very narrow width so little initial bone damage is likely to occur. If you then follow the placement sequence protocol with the finger driver, winged thumb wrench and finally the ratchet wrench for the final depth, the length of the mini-implant is less important than its stability and solidity. Once the implant is solidly placed, it is a mistake to over-ratchet it in dense, type I bone. It is much better to settle for a shorter implant with the abutment head consistent with the crestal level.
Q. I have one primary question: How do I determine the amount or length of bone that is available or what length implant I would want to use? I do not have a Panorex, but have access to one through my local orthodontist. Would you please explain how I could take X-rays and make this evaluation for maxilla and mandibular arches. Also, could you expand on what parameters you use to judge the quality of bone. I am looking forward to using the system a lot. I am already advertising for patients.
A. You have raised many pertinent questions that relate to both conventional implants and our MDI’s. All types of X-rays are useful guidelines as to bone quality (density), quantity and height, but I must say a Panoramic unit is essential if you do implant therapy, whether or not it’s your own by purchase or rental, for maximum visualization ability. CT scans, tomograms, lateral plates, etc. can also be useful, but keep in mind that these methodologies are all approximations. Therefore, none of them give you a truly foolproof answer. Consequently, my best advice is to gain experience in estimation by doing the MDI procedures and taking evaluation X-rays to check your progress and making mid-course corrections as needed to maximize utilization of available medullary and cortical bone without encroaching on any vulnerable structures, such as neurovascular bundle, mental foramen, labial, buccal and lingual plates of bone and floor of sinus or nasal cavities. The best learning tool is experience doing the procedure and carefully monitoring the results. You’ll be surprised and gratified by how rapidly you’ll master the learning curve that is essentially simple but still embodies some interesting and occasionally challenging elements.