Biologically driven innovations for immediate and long-term success - rehabilitation of atrophic jaws with tilted implants

Prof. Christoph Hämmerle kicks off this three-part series on biologically driven innovations for immediate and long-term success by taking us on a journey through the evolution of dental implantology. The journey begins with the discovery of osseointegration by Per-Ingvar Brånemark in 1952, which occurred just by chance. After 13 years of development, it became available to the first patient, and after almost 30 years, the Brånemark system became available to patients worldwide. The ability to anchor a prosthesis to dental implants revolutionized care for patients with missing teeth.

Reflecting on many more innovations that have brought benefits to patients, ceramic restorations were first introduced in 1989, and with the aid of computerized fabrication methods, they have been developed into a standard treatment option widely used in daily practice. The evolution of micro-rough implant surfaces was a significant innovation contributing to the development of immediate function and minimally invasive treatments, with fewer and, where indicated, shorter implants. These innovations bring many patient benefits. Further innovation in digital technologies throughout the workflow from implant planning to placement, and recently introduced optimized surfaces and a new surgical approach. Patients benefit from the predictability of computerized planning and placement and from improved tissue integration.

The All-on-4 treatment concept combines all the critical elements of a successful implant therapy—first, digitalization, including planning, static guided or navigated surgery, and the integrated workflow. Second, improved implant integration in the hard and soft tissues. And third, improved prosthetic procedures and materials for optimal function and esthetics.  Prof. Hämmerle welcomes renowned expert speaker Prof. Enrico Agliardi to discuss the treatment of patients with atrophic jaws with tilted implants without grafting.

When facing a compromised edentulous patient, which treatment protocols are available, and how do you select the optimal one for your patient? Prof. Agliardi details how to use the level of residual bone to determine the available options and the optimal treatment protocol, whether it is the 6-8 implants, All-on-4, tilted implants, whether trans-sinus or trans-crestal approaches, or whether zygomatic implants would be best. Tilted implants become necessary when you do not have the minimum 10 mm of bone required in the molar region. The level of severity of atrophy determines the treatment options in each case.

The All-on-4 treatment concept was invented by Prof. Paulo Malo and first published in 2003 for the mandible (1) and in 2005 for the maxilla (2). What are the fundamental principles of All-on-4? They are complete maxillary or mandibular rehabilitation with only 4 implants: 2 straight and 2 tilted at 30 to 45 degrees. Another principle is reducing the posterior cantilever distally and, in some cases, a negative cantilever to improve the survival of the restoration,  The All-on-4 treatment concept can be performed free hand, with guided or with navigated surgery. A key benefit for patients: it can be performed without bone grafting, a decision that is taken on a case-by-case basis considering the best interests of the patient.

Examining the success of a treatment with the All-on-4, a systematic review and meta-analysis in press shows a 94% implant survival and 99.5% prosthetic survival rates after 20 years of follow-up with almost 12,000 implants placed (3). All-on-4 can be considered a proven solution for patients. Importantly, All-on-4  is not simply positioning two implants straight and two implants axially; it is a surgical protocol that must be followed step-by-step to achieve success.

Prof. Agliardi illustrates the full protocol of the All-on-4 treatment concept, from evaluation and planning, the surgical procedure, and provisionalization to the final restoration and maintenance protocol, step-by-step with detailed images. The complicated edentulous patient presents with the chief complaint: pain during masticatory function and unstable compromised teeth. He carefully evaluates occlusion, function, laterality, and aesthetics using extra-oral or facial scanning and intra-oral examination. In the presented patient case, Prof. Agliardi is faced with a high smile line, “gummy smile”. The main challenge of this is the transition line between the prosthetic pink gingiva and the gingiva of the patient, which needs to be hidden behind the lip. Prof. Agliardi demonstrates the planning of the ridge regularization to correct the gummy smile. After presenting the surgical protocol with a novel implant system (N1, Nobel Biocare), Prof. Agliardi evaluates the patient during try-in with the acrylic provisional restoration to improve the final restoration. At try-in of the final zirconia prosthesis, he verifies the esthetic, occlusion, and function both in static and dynamic before it is sent back to the lab for ceramic stratification.

Is an All-on-4 restoration difficult to maintain? Prof. Agliardi sheds any doubts on this, demonstrating how the restoration must be designed to ensure cleanability.  He recommends professional hygiene and maintenance visits for patients at 6 months after final restoration with the prosthesis in place using floss and brushes, and after one year, removing the prosthesis to perform professional hygiene with special attention to cleaning the multi-unit abutments and polishing the prosthesis- A monthly professional hygiene schedule is recommended for patients with a history of poor oral hygiene.

In summary, Prof Agliardi delivers three main take-home messages to achieve success with All-on-4. One, perform a thorough evaluation according to your treatment algorithm and keep the prosthetic outcome or goal in mind. Two, follow the full All-on-4 surgical protocol closely; it is more than just angled and straight implants. And three, when you use a rigid structure like the zirconia prosthesis, control everything, not only in a static position but also in a dynamic position.  

REferences

1. Maló P, Rangert B, Nobre M. "All-on-Four" immediate-function concept with Brånemark System implants for completely edentulous mandibles: a retrospective clinical study. Clin Implant Dent Relat Res. 2003;5 Suppl 1:2-9. doi: 10.1111/j.1708-8208.2003.tb00010.x. PMID: 12691645.
    
2. Maló P, Rangert B, Nobre M. All-on-4 immediate-function concept with Brånemark System implants for completely edentulous maxillae: a 1-year retrospective clinical study. Clin Implant Dent Relat Res. 2005;7 Suppl 1:S88-94. doi: 10.1111/j.1708-8208.2005.tb00080.x. PMID: 16137093.
    
3. Del Fabbro M, Pozzi A, Romeo D, Nobre MDA, Agliardi E, Long-term outcomes of fixed full-arch rehabilitations supported by tilted and axially placed implants. A Systematic review and meta-analysis. JOMI (In Press),