The All-on-4 concept: how to approach the atrophic maxilla

In his lecture, Dr. Armando Lopes is addressing the approach to treat the atrophic maxilla with the All-on-4 concept. When approaching an atrophic maxilla, we do not only find a general sinus pneumatization, but also a maxilla with a huge amount of bone resorption. Some specific cases can still be rehabilitated the maxilla for example, with the All-on-4 case, and the distal implants, will be placed around the first premolar. The straight implant is than placed around the central and still the  All-on-4 standard procedure can be applied. But there are also even more challenging situations when in fact there is no room in the pre-maxilla area to place four standard implants, on those cases, the treatment of choice would be extra-maxilla anchorage with zygomatic implants, that means two standard implants in the front and two zygomatic implants in the back. This concept is called All-on-4 hybrid. Finally, there are also some cases where without any bone, these are called the empty maxillas. These cases are treated in just one single surgery and 4 zygomatic implants are placed, giving it the name of the All-on-4 extra-maxilla. Dr. Lopes considers these cases “the end of the line cases” in maxilla rehabilitation. Undoubtably these are the most challenging. 

He continues his lecture by showing how to they handle this type of situations and resorption in their daily practice, starting with the All-on-4 standard, also called the atrophic and high skilled situations. He shares a case of a patient with failing the dentition in the mandible, fully edentulous for many years in the maxilla, and we can see here that we will have a pneumatized sinus and a big resorption. This patient is using a denture for many years and is not happy with her current situation. These patients are depressed, they are not able to socialize, and they cannot eat properly, smile properly, and do their normal lives, Dr. Lopes points out. Treating clinicians have a big responsibility and big role in rehabilitating these patients. An important point to check is the gummy smile in these situations in the maxilla. Looking at the CBCT scan, we can see a very thin crest from canine to canine. This means that this is a borderline case where it is not exactly clear if zygomatic implants may be needed. When going into the surgery, you have to be ready for everything, Dr. Lopes says, as it is not clear if an All-on-4 standard will work or if extra-maxilla anchorage will be required. He starts with a crestal incision from one side to the other of the maxilla. He usually places the discharge incisions around the molar area. Then a full-thickness flap is raised as nice and good visibility is crucial for the success of these treatments. As the patient used to show some gum without the denture, he reduces the bone, before starting the All-on-4 surgical protocol. He continues the surgery by identifying the anterior wall of the sinus. Sometimes, the transparency of the sinus after raising the flap is a good indicator, sometimes a small lateral window in the sinus needs to created in order to probe and to feel where the interior of the sinus is and where the tilted implants should be placed. Dr. Lopes highlights that he always starts by placing the titled implants in these cases. Even in this challenging case with very thin bone, he was able to place the implants with good primary stability. He compensates for the angulation by using a 30° multi-unit abutment. Following this, he uses the All-on-4 guide to help with the best prosthetic position with the abutment. After, the anterior implants are placed, in this case using narrow implants suitable for a very atrophic maxilla. In this case, NobelSpeedy Groovy with a diameter of 3.3mm were used and achieved a goof primary stability. Following the protocol, the two straight implants also receive multi-unit abutments (straight) and the flap is sutured back. The prosthetic workflow starts by taking an impression. Applying the immediate function protocol, the patient will leave the clinic with a fixed bridge, an acrylic provisional for both arches. When looking at the post-op panoramic radiographs, we can see that the anatomy was used to the limits. The titled implants are very close to the anterior wall of the sinus, the anterior implants are in the front. Also the mandible poses a challenging case. As Dr. Lopes emphasizes, nowadays we are able to deliver the function, the esthetics and with this a new life for the patient with just a provisional bridge which the patient will use for four months at least. Then it will be replaced by a final bridge. Showing the pictures of the patient before and after the treatment, Dr. Lopes points out how the state of mind and self-esteem of the patient changed just a couple of weeks later. 

Dr. Lopes continues his lecture with a second case where zygomatic implants are used. This is a case of a young patient with an atrophic maxilla, who has been using a denture for years. Her teeth were extracted during her teenage years. And the result is now visible, 20 years later with a very atrophic maxilla. As he mentioned before, patients with dentures are not happy, they are not natural as they are always afraid someone will find out that they have removable dentures in their mouths. He shares that he starts the study of these cases by making of course a CBCT scan and intra-oral scan, and on the DTX studio implant software both scans are merged, and all the conditions are ready to study the case and check what kind of rehabilitation can be planned. In the shown case with a very atrophic maxilla, some bone around the canine pillar is present which allows for the placement of two standard implants. To achieve sufficient posterior support, zygomatic implants will be placed. This surgery was done under general anesthesia, today they typically do more and more cases under local anesthesia, shares Dr. Lopes. He continues by describing the incision, going more palatal and extract the molar in the back. In this type of cases, he usually starts placing the anterior implants first, as the success or the possibility or impossibility of placing the anterior implants will determine whether two or four zygomatic implants will be needed. Fortunately, he was able to place the two anterior implants. By following the planning, he could place two straight implants in the canine area, 4x10mm and place them a little bit more palatal to reach the buccal cortical in the jaw. He proceeds with the surgery, going for the extra-maxilla anchorage. Applying the extra-maxilla technique, a channel is designed on the external wall of the maxilla to have access to the zygomatic bone.  The Schneiderian membrane is easily and cautiously pushed to the side, the zygomatic bone is penetrated, and the bone is prepared for anchorage of the implants. The first drill, Dr. Lopes uses is the 2.9 drill, he points out this drill is the most important as this drill shows the bone density, direction, and length of the implant. The bone is prepared according to its density, followed by the implant placement. In this case, 42.5mm zygoma zero implants were placed. The same procedure is performed on the other side of the patient, with gently pushing the membrane, feeling the top of the maxillary sinus and start the preparation of the bone. In these cases, the implants are placed by-cortically, using all the advantages of the bone as there is typically 7-8 mm thickness of bone available. Typically, this is also dense bone so all will need to be prepared with the drilling sequence. The zygomatic implants are placed with slightly more than 50 Ncm, which allows for immediate loading. With this approach, today techniques and components are available that provide for immediate function in these cases as well. In the morning the surgery was performed and, in the afternoon, after the patient woke up, the denture was converted, and a bridge delivered. Dr. Lopes highlights that with the extra-maxilla technique, we can come out with the prosthetic screws in the center of the crest, providing a nice ergonomic and prosthetic outcome. He continues with a 6-month follow-up image, the moment the patient was ready for the final bridge. The biggest changes do not happen inside the mouth, but with the personality, the self-esteem, and the joy of life of someone who is not even 40 years old, and has the feeling of natural dentition back, he stresses. The cases are challenging but it is also very rewarding, according to Dr. Lopes. 

Moving on to the third and last case of his lecture, Dr. Lopes presents a case with even more resorption than the second case. The female patient is in her middle 30’s, so she is quite young and has been submitted already to several interventions with failures, bone grafting and implant repetition. She has at least made 6-7 attempts to have fixed teeth without success. So, she is presenting herself as a very sad and very sceptic patient to any treatment. At the same time, she is really unhappy and depressed because of her missing teeth and she cannot use a denture. In the last months before the treatment, she was not able to use dentures in the maxilla, so she is not living, she is only surviving. Looking at the intraoral view, we can see a very flat anatomy, looking at the CBCT scan we can easily realize that there is no bone at all in the maxilla and the only way to find some bone is the zygomatic bone. Evaluating the case in the DTX Studio implant software, Dr. Lopes decided to place four zygomatic implants. These kinds of surgeries are always challenging, these are more advanced surgery as they take place outside of the oral cavity, according to Dr. Lopes. As we are close to the orbit, we need to know exactly what we are doing. He plans the case with the software, and follows the same protocol as previously described, by pushing the membrane gently and avoid any sinus communication as much as possible. The implant channel needs to be prepared between the orbit and the posterior border of the maxilla to find a space to accommodate two zygomatic implants. According to Dr. Lopes the bone quality is usually good, type I bone, and comparable with the anterior mandible bone. Although in several cases there is less than 7mm of bone available to accommodate the implants. To achieve the basis for immediate function, we need to play with the drillings, says Dr. Lopes. Both implant sides are usually prepared by placing the most mesial implant first, so we don’t have to avoid any movements of the implants or something through the orbit.  In a second step the distal implants are placed in the zygomatic bone. On the left side of the shown case, Dr. Lopes was able to achieve the necessary primary stability with at least 50Ncms. On the right side the patient had some oral-antral communication due to previous interventions, so he had to be gentler as there was less bone support for the zygomatic implants. He starts again with the round bur, followed by the 2.9 drill, 3.5, 4.0 and 4.4 diameter drills. On the distal implant on the right side, the zygomatic bone was very short and the necessary and minimum primary stability for immediate function could not be achieved. When placing the implant, he could only achieve 30Ncms. Dr. Lopes explains that he decided to load only the other three implant. When the patient woke up, he was still able to provide her with a provisional bridge on top of three implants. The fourth implant was left to heal for at least 4 months. After four months the patient came back and received the final bridge on all four implants. Dr. Lopes continues the case description by showing follow-up photos after 10 days, still showing the healing phase of the gingiva around the implants. But the good prosthetic outcome is already visible, there is no palatal access, and the bridge was ergonomically designed. Additionally, the patient got a nice lip support, the correct occlusion, vertical dimension, and new self-esteem. 

Today, there is no doubt that sufficient support for the All-on-4 concept is available. Dr. Lopes shares some data for treatments of the mandible, showing a paper published in 2019 with a 19-year follow-up with All-on-4 in the mandible and contained 471 patients. In total, 1884 implants were placed and 18 years later the survival rate can be stated with 93%. Moving on to the maxilla the numbers look quite similar, with a 13-year follow-up the survival rate can be stated at 94.7%, with a sample size of 1072 patients. Talking about zygomatic implants and the All-on-4 hybrid technique, a publication from 2021, following 44 cases with 77 zygomatic implants versus 115 standard implants. After 2 years of follow-up, Dr. Lopes states that this type of approach with immediate function gives us a 98.7% survival rate. He emphasizes that there is more than evidence today, including systematic reviews, like the one from Patzelt (2013) summarizing 13 papers from clinicians worldwide, with 4804 implants followed and a 3-year survival rate of 99%. The simplified protocol, independently of the degree of resorption, can help to reduce the patient morbidity because of low incidence of complications and a minimal invasive surgical approach. Dr. Lopes summarizes this to one surgery on one day with fixed teeth, which reduces chair-time and provides more a better and more comfortable post-surgical period to the patients. He points out that this approach is ideal for edentulous patients and patients with failing dentition.