Carl E. Misch, DDS, MDS, is clinical professor and director of oral implantology at Temple Dental School in the Department of Periodontology and Implant Dentistry. He is also director of the Misch International Implant Institute, which has trained more than 2,500 general and specialty dentists over the last 24 years. Dr. Misch is the co-chairman of the Board of Directors of the International Congress of Oral Implantologists, the world’s largest implant organization, and he has 13 Fellowships in dentistry, including Fellow of the American College of Dentists and the International College of Dentists. His 3 textbooks on implant dentistry (Contemporary Implant Dentistry, editions I and II, and Dental Implant Prosthetics), published by Mosby/Elsevier, are printed in many languages. He is also the co-inventor of the BioHorizons Dental Implant Systems.
Dentistry Today conducted an exclusive interview with Dr. Misch to hear his views on the role of the general dentist in implant treatment.
DT: What role should the general dentist have in implant dentistry?
Figure 1. A preoperative panoramic radiograph of a 60-year-old female with advanced atrophy in the maxilla and mandible.
Figure 2. A postoperative panoramic radiograph after bilateral sinus grafts and iliac crest bone grafts to the maxilla and mandible.
Dr. Misch: Implant dentistry evolved from general dentists. In the 1940s, Strock developed the concept of “ankylosis” for implants to replace a single tooth. Linkow is often considered the “Father of Implant Dentistry.” As a general dentist in 1965, he developed an implant practice that existed until 2001. During that time frame he lectured more than 4,000 times, published hundreds of articles, wrote 7 books, obtained more than 50 patents, and dedicated both his personal and professional life to implant dentistry.
General dentists placed the vast majority of implants in the United States until 1985. In fact, even today general dentists place the vast majority of implants around the world. The only 3 countries in which specialists place more implants than general dentists are the United States, Canada, and Australia.
Several implants have been developed by general dentists—including the Sterioss and Nobel Biocare root form implants by Hahn, the IMZ by Kirsch, and the Omni R by Tatum. Tatum also developed bone grafting for implants, including sinus grafts and bone spreading in the late 1970s.
This is not to say specialists did not contribute to implant dentistry. Prior to 1985, the staple implant was developed by Small, an oral surgeon. Gershkof and Golec (oral surgeons) taught the subperiosteal implant (invented by Dahl, a general dentist in Sweden). Golec also developed the HA coated cylinder implant in the 1980s. Niznick, a prosthodontist, invented the Core-Vent implant.
A Swedish orthopedist and bone researcher, Brånemark, galvanized the dental profession (especially the specialists) to accept implant dentistry in the mid-1980s. His team of specialty dentists expanded rapidly around the world and began to publish organized research and clinical studies unlike anything ever seen before in our history. Since that time, the specialists around the world have published 20 times more articles in the last 10 years than the entire dental community published prior to this time.
Today, the role of the general dentist has evolved into a very important part in providing implant restorations to patients. There are fundamental reasons why the GP is in the dominant position of patient care. Most often, the general dentist presents the initial treatment plan to replace a missing or hopeless tooth. The long-term relationship the GP has with the patient and his or her family makes the general dentist a primary confidant with the patient. A specialist rarely sees the patient in the long term—both in disease and health—and as a consequence, the patient trusts the general dentist. Therefore, the GP should initiate the discussion of implants to replace missing teeth.
Once the patient accepts the treatment concept to replace a missing tooth, a whole range of methodologies exist. The primary treating team members (other than the patient, who is always the most important member) range from a trained GP and laboratory technician to many interrelated specialties. For example, the team may include an oral surgeon able to augment atrophic ridges, an implantologist (GP with advanced training) to place the implants, a periodontist to develop the soft tissue, an orthodontist to arrange the remaining teeth and develop the implant site, and a prosthodontist for complex restorative cases.
When only one doctor provides all the implant-related treatment, either a GP with advanced training or a prosthodontist (with advanced training) can deliver all of the services required to treat the patient properly. The key is to refer the patient for a procedure when adequate training and experience are not present, whether the treating doctor is a GP or a specialist. For example, a specialist or a GP who cannot perform autologous iliac crest mandibular bone grafts to the implant site should not undertreat a patient with severe bone loss as a result of his or her inability. Instead, the clinician should refer these types of patients for proper care (Figures 1 to 6).
Figure 3. An intraoral view of the maxillary and mandibular implants after initial healing in the iliac bone graft.
Figure 4. The maxillary and mandibular fixed prostheses for this 60-year-old female patient.
DT: Can GPs be adequately trained to perform implant surgery?
Dr. Misch: Absolutely! Over the last 24 years of the Misch Implant Institute, I have trained more than 2,000 general dentists to perform root form surgery, membrane bone grafts, sinus grafts, and soft-tissue procedures. In addition, I have also trained almost 1,000 GPs to perform block bone grafts harvested from the mandibular ramus and/or symphysis.
It is important for anyone learning about implant surgery to have an extended, supervised training program during their learning curve. This is necessary for both specialists and general dentists. In fact, several dental schools over the years have used the Misch Implant Institute to train graduate residents from periodontics, oral surgery, and prosthodontics programs in the fundamental and advanced concepts of implant surgery and bone grafting. Temple Dental School currently co-sponsors all the Misch Institute Programs, and all the faculty are professors within the Periodontal and Implant Department at the school. All graduates (residents, GPs, and specialists) receive a certificate from Temple Dental School and the Misch Implant Institute.
Several programs are available to extend the training of the profession in a supervised, hands-on experience. This is especially required in advanced bone grafting procedures. Do not begin your training by going to an implant meeting with 50 lecturers, each presenting for 30 minutes. Each person shows his or her best cases, and very little knowledge is gained for the beginner in the field. These meetings are designed for experienced colleagues who can separate the wheat from the chaff. Do not take an implant manufacturer one-day course; it is designed to sell you a product. These courses are best for experienced dentists who are changing the system they use and take manufacturer courses to understand the subtle differences in one product compared to another.
Do get involved. Do take a structured course over an extended period. I suggest a program where primarily one person does most of the lectures in order to provide a consistent approach. When you first learn to cook, and you hear one person, you learn a particular cuisine and style that works. If you are a beginner and hear one person talk about Chinese food, the next person presents Italian, the next person explains French cuisine, and the next person Mexican—all in 3 days—you still can’t cook a meal.
An extended program designed to start with the science of implant dentistry, which gradually progresses to complex full-arch treatment, is a major benefit. When I started the Misch Institute 24 years ago, the program had 5 different sessions, each 3 days long, and covered implant surgery, sinus grafting, and implant prosthetics. Today, the field has progressed so far that we have 9 different 3-day surgical programs for treatment planning, bone grafting (membrane, sinus grafts, and block bone grafts), implant surgery, soft-tissue surgery, implant surgical complications, and hands-on supervised patient surgeries. Also, 3 additional, 3-day programs in implant prosthetics present treatment planning, fixed implant prosthetics, and removable implant prosthetics. A general dentist or specialist may choose to take only a few of the programs or enroll in all of them.
There are many ways to get to the top of the mountain. Some paths are easier than others. An experienced guide, with a history of teaching, can get you to the top of the mountain faster and easier. The most important thing is to get started. The journey never starts when you get ready to get ready. Begin today.
Figure 5. A post delivery panoramic radiograph of the iliac crest bone grafts and final prostheses.
Figure 6. A high smile line of the female patient after rehabilitation with bone grafts, implants, and fixed prostheses.
DT: Are implant prostheses restored differently than natural teeth?
Dr. Misch: Definitely! Several concepts and techniques in implant prostheses are different than those for natural teeth. For example, it is not unusual to have an implant prosthesis replace several teeth and also reproduce the soft tissue. Gingival pink porcelain is often used to replace multiple missing teeth in the maxillary implant prosthesis.
The most common complications for natural tooth restorations are decay and endodontic-related problems. Implants do not decay and do not need endodontics. As a result, implant restorations have a higher long-term survival rate. However, prosthetic complications that do not cause prosthetic or implant failure are more common with implant prostheses. These complications include abutment screw loosening, porcelain fracture, uncemented prostheses, crestal bone loss around the implant, and difficulty in aesthetics related to the soft-tissue contours. In order to reduce these complications, biomechanics (rather than bacteria) must be addressed both in the treatment plan and the final prosthesis.
The crown contour of posterior teeth is often modified to direct the occlusal forces over the implant body. The buccal contour of the mandibular posterior teeth and the lingual contour of the maxillary posterior teeth are not in the “aesthetic zone” of an implant restoration. By reducing these regions, the occlusal forces are directed along the axis of the implant, which also reduces the risk of porcelain fracture and prosthetic screw loosening.
Natural teeth exhibit greater movement than implants when placed under an occlusal load. This actually makes the implant more vulnerable to biomechanical stress. Therefore, in a partially edentulous patient, the timing of occlusal load permits the natural teeth to occlude prior to the implant-supported crowns. The initial occlusal contact on teeth causes them to be depressed or move laterally prior to the implant receiving the load.
The metal framework under a porcelain-to-metal restoration should be extended under the marginal ridges of an implant prosthesis. The implant has a higher impact force, and the designed framework places the porcelain under compressive force rather than shear.
Individual crowns on teeth reduce the risk of decay or endodontic complications. However, implants do not decay. Therefore, the restorations are usually splinted together rather than left as independent units. The splinted implant crowns reduce the force to the abutment screws and decrease loosening. In addition, the restoration may be more easily removed if the implants require treatment in the future. The interproximal area is easy access for the position of a crown remover when the implants are splinted together. In addition, the marginal ridges have metal below them when the implants are splinted together. This reduces the risk of porcelain fracture. There is less stress to the implant crestal bone when they are splinted together. Less stress reduces the incidence of crestal bone loss.
The Misch Implant Institute has a 9-day implant prosthetic program that presents many concepts unique to implant restorations. My book Dental Implant Prosthetics, published by Mosby/Elsevier, covers most of these concepts. Many complications can be completely eliminated, while others may be dramatically reduced, with proper training.
DT: When implants replace multiple missing teeth, what is the most important aspect of treatment?
Dr. Misch: As mentioned earlier, the vast majority of complications in implant dentistry are related to biomechanics. The complications include early loading implant failure, crestal bone loss, abutment screw loosening, porcelain or acrylic veneer fracture, and uncemented restorations. Therefore, the treatment plan should evaluate key implant positions and implant number based upon biomechanics, not the existing bone volume.
There are 3 general rules based upon biomechanics for key implant positions related to implant treatment planning for multiple missing adjacent teeth: no cantilever, no 3 adjacent pontics, and the canine and first molar rule. I’ll discuss each of these rules.
Regarding the “no cantilever” rule, cantilevers are force magnifiers. It is not unusual for bone volume to be reduced in the posterior regions of the mouth. As a result, past methods to replace posterior teeth included anterior implants, in front of the mental foramen or maxillary sinus, and posterior cantilevers. This is a biomechanical compromise that often leads to complications.
The posterior regions of the mouth have higher bite forces. A molar region has a bite force 5 times greater than the anterior regions. The worst region to design a cantilever is in the posterior region, where the forces are greater. The natural teeth are not cantilevered from the anterior; instead, 3 roots and larger diameter teeth are in the posterior region.
A cantilever in the posterior region can multiply the bite force by 2 to 5 times, depending upon the length of the cantilever and the distance between the anterior and most distal implant (called the anterior-posterior [A-P] distance). In the mandible, an anterior-posterior distance between implants is often less than 10 mm. A cantilever length of 20 mm (to the distal of the first molar) will increase the force by 2 times to the most anterior implants and 2.5 times to the most distal implants. Since the bite force is 5 times greater in the posterior, the total increase in posterior bite force with a cantilever gives a force 10 times greater to the anterior implants. Therefore, cantilevers should be eliminated whenever possible, especially in the posterior regions.
Regarding the “no 3 adjacent pontics” rule, when 3 adjacent pontics are used in implant dentistry, the 2 adjacent implants must distribute the force of 5 teeth. This dramatically increases the biomechanical risks. In addition, a span of 3 pontics flexes the metal in the prosthesis 27 times more than 1 pontic, and 19 times more than 2 pontics. The increased flexure increases uncemented restorations, abutment screw loosening, and porcelain fracture.
Regarding the “canine and first molar rule,” the canine and first molar are particularly important positions within an arch. The natural teeth with the greatest root surface area are the canines and the first molars. Therefore, when either of these 2 teeth are missing, an implant in the site is an important position to decrease biomechanical risks.
When a larger diameter implant cannot be placed in the first molar region because of inadequate bone width, 2 regular size implants are suggested. Hence, where the bite force is the highest, more surface area is used to distribute the load (just like natural teeth).
DT: What implant organization can a general dentist join for continued support in this field?
Dr. Misch: The largest implant organization composed primarily of general dentists around the world is the International Congress of Oral Implantologists (ICOI). More than 90 countries are represented in this organization, and at least 5 implant programs are held every year around the world at various times. The official publication of the ICOI, Implant Dentistry, is primarily directed at the general dentist and provides a wide range of current research, clinical studies, and techniques. The ICOI also has created a branch of the organization for laboratory technicians and staff members (receptionists, chairsides, and hygienists). There is a certifying program for doctors in the form of Fellowship, Mastership, and Diplomate. The ICOI Web sites icoi.org or dentalimplants.com have separate sections for patients and the profession. The ICOI can be reached for further questions or membership at (888) 449-4264 or (973) 783-6300.
DT: What is the future related to the growth of patients treated with implants?
Dr. Misch: The US population will increase 49% by 2030. A large percentage of this increase is in the population above the age of 50 years. The first tooth lost today in the US is after the age of 35 years, and the older the patient, the higher the prevalence of tooth loss. The total sales of implants to dentists in 1975 was $1 million. In 1985 the total sales was $100 million. Today the sales of implants to dentists is more than $1 billion.
Although the percentage of completely edentulous patients is decreasing, the actual number of completely edentulous patients is increasing! Currently, 18 million people in the US have no teeth, and another 12 million people are missing all of their maxillary teeth (with at least some mandibular teeth remaining). This accounts for 20% of the US adult population. In addition, 50 million people are missing posterior teeth in 1 to 4 quadrants. Since implants are often used to stabilize or eliminate removable prostheses, the demand for implants will become greater and greater in the future.
Single-tooth replacement with an implant has the highest success rate in all of prosthetics, regardless of the method. Several dental schools now teach undergraduate dentists how to surgically place and restore a posterior single tooth with an implant. In fact, studies at Tufts and San Antonio dental schools demonstrated predoctoral dental students can place implants with a 5-year survival rate of almost 100%. Implant dentistry is becoming the primary method to replace teeth, rather than using implants as a last resort.
For more information about the Misch International Implant Institute visit misch.com or call (248) 642-3199.