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Implant Q&A: An Interview with Dr. Michael McCracken


Michael McCracken, DDS, Ph.D and Bradley C. Bockhorst, DMD


Ongoing studies in edentulism have revealed disturbing correlations between tooth loss and farther-reaching systemic health issues such as gastrointestinal disorders, atherosclerosis or even cancer. In this video interview with accompanying article, prosthodontist and University of Alabama School of Dentistry professor Dr. Michael McCracken discusses the use of dental implants to stave off bone resorption, access to and affordability of implant treatment, and the advantages and limitations of various restorative options available today.

Michael McCracken, DDS, Ph.D

mccracken After completing dental school at the University of North Carolina at Chapel Hill and a prosthodontic residency at University of Alabama at Birmingham, Dr. Michael McCracken received a Ph.D in biomedical engineering for research related to growth factors and healing of implants in compromised hosts. Dr. McCracken is a professor in the department of general dental sciences at UAB School of Dentistry, where he has also served as associate dean for education, director of graduate prosthodontics, and director of the implant training program. He maintains an active research program within the university and a private practice focused on implant dentistry. He also lectures internationally. Contact him at

Bradley C. Bockhorst, DMD

bockhorstAfter receiving his dental degree from Washington University School of Dental Medicine, Dr. Bradley Bockhorst served as a Navy Dental Officer. Dr. Bockhorst is director of clinical technologies at Glidewell Laboratories, where he oversees Inclusive® Digital Implant Treatment Planning services and is editor-in-chief and clinical editor of Inclusive magazine. A member of the CDA, ADA, AO, ICOI and the AAID, Dr. Bockhorst lectures internationally on an array of dental implant topics. Contact him at 800-521-0576 or

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An Interview with Dr. Michael McCracken

Dr. Bradley Bockhorst: Today, Mike, I'd like to talk about one of the things that is near and dear to your heart: the health effects of edentulism. Why don't you go ahead and tell us a little bit about what you've been doing along that line, both at UAB School of Dentistry and professionally.

Dr. Michael McCracken: Thanks, Brad. It's nice to be here. We have been learning a lot about edentulism in the last 10 years or so. We are realizing how health can be affected by the oral state, and how somebody losing their teeth will lead to all kinds of systemic problems, such as atherosclerosis or cancer. People who have a denture, or who have a poor denture, take a lot more GI medicine. So we are looking at ways that we can treat that as a dental community. I think it's an exciting time to be in dentistry because now we have implants. Now we have options that we didn't have many years ago that we can offer to patients. Instead of telling them they have to have a denture, we can offer them some valuable alternatives.

BB: One of the challenges we face as dentists is that it's our obligation to communicate to our edentulous patients what is going on as far as bone loss. Maybe you can share your thoughts along that line.

MM: I think about that sometimes. We know that one of the leading lawsuits against dentists is the failure to diagnose periodontal disease. So a patient goes to their dentist whom they've gotten along well with for 20 years, and they've been going in every six months for their checkup. They've been doing what they think they should be doing on their side. Then one day the dentist walks in and says: "Well, I'm sorry. You have periodontal disease. And now you're going to have to lose these teeth, or you're going to have to have this surgery, or have these implants placed." Understandingly, the patient is upset by this and says: "Why didn't you ever tell me about periodontal disease? Why didn't you ever tell me I had this disease in my mouth?" They're upset, and this causes some problems.

Sometimes I wonder: Will we see that with the edentulous patient? Because now we have a similar situation. We have a patient who has been going to a dentist for 20 years. Maybe they come in every year or two for a checkup or a denture adjustment. And then all of a sudden they have problems with a mandibular fracture, or they have a situation where they can no longer successfully wear a lower denture, or they are experiencing something else related to bone loss. And maybe they're going to ask their dentist: "Why didn't you ever tell me about this bone loss? Why didn't you ever tell me this was going on? Why didn't you tell me about this disease?" Because now we can effectively treat that with implants.

BB: If dentists are not involved with implants, for whatever reason, do they have an obligation to offer them as an option to these patients to stop that potential bone loss?

MM: Absolutely. Clearly, whether you offer those services in your office, or you refer to a surgeon for implant placement, the option has to be offered to the patient. They just need to understand what's going on. We have some patients who learn the hard way the effects of bone loss. As an example, we had a lady who, after being edentulous for many, many years, had her mandible resorb and resorb, becoming the size of a pencil. She breaks her mandible as she is walking out to the pool — stepped too hard, hit her jaw, and now she has a fracture. It's a very difficult revision surgery — usually bilateral hip grafts — and quite a bit of hospital experience. A lot a money and a lot of morbidity come with that when, if somebody had just told her at the right time that they needed to put some implants in there to maintain her bone levels, she would've been much better off. Then it's not a hospital procedure; it's an in-office procedure — very simple. Instead of three days in the hospital, you have three hours in the dental chair.

BB: Are there any studies or any research coming out of UAB School of Dentistry that are related to being able to maintain that bone level, or even in some cases potentially increase it?

MM: Yes. And we did see an increase in bone levels, surprisingly to me, in a study that was done by the periodontists at UAB, which was a prospective clinical trial, long-term, about eight years. And we restored these patients with five implants in the anterior mandible and a very traditional Brånemark style, with about 3 mm between the prosthesis and the edentulous ridge. We noticed over time — this was back in the nineties — that the tissue would proliferate and touch the bottom of the bridge. The periodontist thought we had better clean that up or take that down, so the patient would have access to clean. When they went in there to remove that soft tissue, it wasn't soft tissue; it was bone. So we measured that as part of this clinical trial, and we saw 1.5 mm, some patients 2 to 3 mm, of bone gain distal to the implant. So not only are we maintaining the bone between the implants, we are actually getting bone maintenance or a bone gain of up to 2 mm on average behind the implant. So as we are adding stress back to this system, the bone is responding by increasing in volume and density.

BB: That leads into one of your other primary interests: talking to patients about bone loss, and giving them solutions that are affordable. Maybe you can share with us a little bit about what you've done at the school as far as low-cost options for restoring these patients.

MM: Certainly. I do think that is critically important. If we believe that implants are important, as we do as a profession, then how can we help more of our patients get into implants? How can we assist our patients, let them experience implant dentistry and enjoy those benefits? At the school, we have developed a lowcost program that we have offered to our patients. Of course, keep in mind it's a dental school, and we have students working on these. But we have provided the two-implant overdenture, which is just a basic, entry-level implant prosthesis. We give them the two implants, the two dentures and the two attachments for around $1,500. Most people we find can get into that with a little bit of desire. Most patients are very satisfied with that price point, and we are able to help them maintain their bone, get rid of a complete denture and move into an implant-supported prosthesis.

BB: I believe you're also doing some ongoing work with 3 mm diameter implants?

MM: We are. To me, this is an interesting potential solution to some of the costs associated with traditional implant systems: single-piece overdenture implants. These are available generally in different sizes, around 3 mm or a little smaller. We wanted to make sure that this treatment modality was going to be successful for our patients. We did a clinical trial with about 45 patients, and we randomized those to two, three or four 3 mm diameter implants in the mandible. I was really surprised at the results. I'm generally conservative when it comes to loading protocols, time and so forth. Obviously, with a one-piece implant, you can't have delayed loading. So we had immediate loading at the time of placement, and we had a relatively small-diameter implant. Clinically, the results were excellent. I'm gaining much confidence in this treatment modality.

BB: I know the results haven't been published yet, but do you have a preference for the number of implants — two, three, four? Typically when we start getting into the smaller diameters, they're saying four implants in the symphysis. What is your take on this?

MM: That was the main question: Do you have to do four? Because if you're going for a low-cost alternative, it would be cheaper to do two. And, indeed, we found no difference between two or four implants, in terms of implant survival or bone loss around the implants. So two implants, in our study, worked very well.

BB: Some people call the 3.0 implants "hybrids" because they are getting close to that conventional diameter, as opposed to the very narrow implants — the true small diameters. Would you have a different approach if you went smaller than a 3.0?

MM: I've still been a little nervous about the smallerdiameter implants. I just haven't had a lot of clinical experience with them myself, coming from a more conventional approach with standard-diameter implants. But the results that we got from the 3.0 are encouraging me to try something a little bit more narrow, because there are times when that's very helpful. I mean, many patients have a narrow ridge, and you're faced with the clinical decision of, am I going to remove 6 or 7 mm of bone height so I can get sufficient width for my implant? Or am I going to simply place a small-diameter implant? I think maybe we'll be going more toward the direction of the smaller implants as we move forward with this.

BB: On the subject of bundling prices to get implant treatment to an affordable level for patients, you mentioned bundling two implants, two dentures and two attachments. Do you have something else if you're going to do four 3.0? Have you gotten into a bundle for that, or is that still a work in progress?

MM: For the students, it's still a work in progress. For my own practice, I think that is very exciting. I love what Glidewell has done with the package concept because it really simplifies things for me as a clinician to know: This is your cost, these are your implants, get the overdenture for that. Then I can translate that into a clinical situation with a patient who really wants to get implants, and who I really want to get into implants. It simplifies things for everybody. I definitely plan to pass those cost savings on to the patients.

BB: I understand that outside of the dental school, you are getting involved in a community clinic. Do you want to share a little bit of why you got involved with that and what your plans are with it?

MM: Sure. We set up a community clinic outside of Birmingham. We're associated with a drug-addiction recovery program down there, but we're also open for community patients who don't have much access to care. And I have to say, it is one of the most rewarding things I do — even with being a teacher, which is rewarding in itself. To help people who don't have other avenues for dental work is extremely exciting. It's a big volunteer effort from a number of organizations down there involved with that. But we're planning on offering them the best dentistry we can, and that's definitely going to include implants.

BB: That ties right into bundled pricing, where you can offer services at very affordable prices.

MM: That's right. We have a lot of edentulous folks in Alabama — sixth highest in the States is our ranking now, I believe. So we have plenty of people needing implant overdentures.

BB: Do you know what the percentage is?

MM: For our seniors, age 65 and over, it's more than 30 percent now in Alabama that are edentulous. And that's fairly consistent with other states.

BB: We've talked a lot about restoring the lower edentulous ridge. What do you typically do in the maxilla?

MM: The maxilla is a little more of a challenge. The bone is less dense, of course, and the implants are less predictable in the maxilla. I've always been an advocate of multiple implants tied together — be it with a bar, be it with a fixed prosthesis. But lately I've had success with individual implants and a cobalt chromium framework to give structure to the prosthesis, so that we have some form of cross-arch stabilization and some splinting from that rigid metal framework. So in the maxilla, now I'm moving more toward four implants with attachments using that metal substructure.

BB: If you go that route — four implants and a cast framework — are you going palate-less, or are you still doing complete palatal coverage?

MM: I have to say I'm about fifty-fifty on it. Occasionally I'll take the palate out. I think that's pushing the limits a little bit. I certainly see that it works in some patients, but I try to talk the patients into a palate.

BB: Another study coming?

MM: That would be a great study — six implants, no worries.

BB: Is there anything else exciting going on at the school or for you personally?

MM: Tough question. I was walking through Glidewell Laboratories, and I'm really excited about the milled BioTemps® that are coming out now. They look beautiful. I've always been thrilled with BioTemps, the pricing and the esthetics, especially long-term. As a prosthodontist I have patients' cases for 12, 15 months waiting for grafting or whatever, and the BioTemps have held up really well for me. I like the milled approach they're taking now. It just seems to be a neat technological advancement.

BB: Yes. Everything is going CAD/CAM. It provides a more predictable, consistent result.

MM: I think it won't be too long from now when I can just take a scan of the arch, not even have to make a cast, and you guys can send me a BioTemps full arch.

BB: Yes, that's coming. Let's step back a minute and talk about your thoughts on cone-beam scanning, on using it as a diagnostic tool for those edentulous patients. Do you do it just for diagnostic purposes? Do you head toward guided surgery? When would you use a guide versus doing a flap?

MM: For me, I find that a flap is useful in many of my surgical approaches. That may be because I need to manipulate the soft tissue. I may need a grafting in a certain situation. We may need to thicken the soft tissue. So, for a variety of reasons, I find that I'm laying a lot of flaps. For the perfect patient with abundant bone and abundant keratinized tissue, there's nothing easier than a guided surgery. With a placement, to have the confidence and predictability of knowing the anatomy, you can't beat that, knowing that your implant is going to come out in the right spot.

BB: At the school, are you guys routinely CT scanning those patients?

MM: Routinely? No. For me, if the patient has abundant bone, I don't really need to scan. If the patient has very inadequate bone, sometimes I don't need to scan to tell. I know I need to graft. It's the patients in the middle, certainly large cases, where CBCT is a great help — especially for the patients where you really don't know what your approach is going to be. Do we need to graft? Can we place the implant and graft simultaneously? Many of these questions are answered with a cone-beam scan.

BB: We talked about the health effects of edentulism and keeping patients informed of implants as an option, particularly implants and prosthetics on top of them as an affordable option. Do you have any final thoughts or comments on this?

MM: I think we should be using the fixed prosthesis more. I see a lot of people who are very comfortable with the two-implant overdenture, the four-implant overdenture. I think the fixed prosthesis, a traditional Brånemark hybrid prosthesis, is one of the best things we can do for folks, and I'd love it if we were doing a lot more.

BB: How many implants do you usually like to do for your hybrids?

MM: Traditionally, I like five, but I'm very comfortable with four. They can be straight. They don't have to be tilted. The literature clearly supports four implants in the anterior mandible. And, just recently, I read an article that showed good success on three. So maybe we are even pushing the limit in that direction as well. But I think four or five implants is very reasonable.

BB: OK, great. So what do they say in 'Bama?

MM: Roll Tide.

BB: There you go.

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