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When treating edentulous patients, the use of four implants to support full-arch fixed, fixed removable, or removable prostheses is a popular therapeutic option. Treatment planning, of course, begins by determining the types of prosthetic therapies that are possible, based on evaluations of the patient’s teeth, bone and soft tissues. For insights into clinical considerations for all-on-four treatment, Decisions in Dentistry asked Douglas W. Beals, DDS, MS, and Thomas A. Caspers, DDS, educators with expertise in oral and maxillofacial surgery and restorative dentistry, respectively, to share perspectives on what shapes the decision to choose this treatment approach.
Table 1. Factors Used to Determine Physical and Psychological Risk Assessment for Implant Therapy
- Patient’s psychological history
- Patient’s level of dental anxiety
- Difficulty of the surgical treatment plan
- Length of the planned surgery
- Whether the patient will require sedation; could it be accomplished in an outpatient setting?
- Patient’s history of drug, alcohol and/or tobacco use
- Updated list of patient’s medications
- Updated medical history
- Updated dental history
- Appropriate medical consultation when indicated
- Updated dental history
- Appropriate medical consultation when indicated
In terms of patient assessment and selection, where does the clinician start when planning implant-supported prosthetic therapy?
Douglas W. Beals, DDS, MS: Selection of the dental implant patient begins with his or her current and past dental, medical and surgical history, as well as other pertinent contributing factors. These factors affect treatment success and contribute to overall risk of rendering treatment. Once the restorative doctor has developed a preliminary treatment plan, the patient should be evaluated by a surgeon. The purpose of this evaluation is for the surgeon to develop the physical and psychological risk assessment (Table 1). This determines if the surgical portion of the proposed treatment can be accomplished in a safe and effective manner.
Next, a proper evaluation of the hard and soft tissues is required. The quantity and quality of each should be determined through proper radiographic and clinical examination. Cone beam computed tomography (CBCT) is considered by many as the gold standard for evaluating hard tissue during this phase. It allows practitioners to determine the morphology (i.e., quantity) of the maxillomandibular complex in three dimensions, which is required when planning a full-arch, implant-retained prosthesis. If the present morphology does not permit implant placement that will support long-term success, hard-tissue augmentation may be necessary. In most full-arch, implant-retained cases, bone removal is required to create space in the superior-inferior dimension for restorative materials. This is also planned utilizing CBCT in conjunction with implant planning software.
Similarly, the patient’s bone density (i.e., quality) is ascertained with CBCT scans. Lack of density due to osteoporosis or other factors may prevent the practitioner from obtaining the proper insertion torque so conversion and provisionalization may be completed at implant placement. In addition, keratinized tissue must be present in the proper amounts and locations. Long-term implant success is enhanced by attached keratinized gingiva. If this tissue is lacking or unattached, augmentation becomes necessary.
In a patient with a severely atrophic maxilla or mandible, treatment options differ for each location: Zygomatic implants may be employed in the maxilla, whereas in the mandible short implants may be an option.
Thomas A. Caspers, DDS: Besides determining if favorable skeletal occlusion, inter-arch space, and adequate hard and attached soft tissues are available, the assessment and planning phases of dental implant therapy should also explore the patient’s expectations. The clinical team needs to ensure that reasonable and realistic expectations are in place.
In cases involving the maxilla, lip dynamics and display of the prosthesis ridge interface are additional considerations during treatment planning and delivery.
What are the advantages and disadvantages of the all-on-four approach?
TAC: Patients with terminal dentitions and removable prostheses lend themselves to all-on-four treatment. The advantages to the patient are that it is rapid and provides a fixed solution closest to that of being dentate. The disadvantages are that is requires detailed interdisciplinary planning and some luck on the day of surgery for a successful conversion of the denture to the temporary fixed hybrid.
DWB: The fixed hybrid restoration is the option that will return the edentulous patient to a level of function that most closely approximates his or her lost dentition. This, and the idea that it is fixed and does not require removal by the patient, are what attracts most individuals to this treatment choice. Excellent esthetics are achievable if guidelines for proper patient selection are followed.
Implant success hinges on detailed and thorough interdisciplinary case planning. Beyond assessment and planning, the surgical treatment may be long and invasive — with associated risks and complications. Ultimately, the time and cost involved in dental implant therapy can be significant and, in some instances, prohibitive.
Have recent developments in technologies and materials had an impact on planning and long-term success of all-on-four treatment?
TAC: Cone beam imaging, digital design software, and three-dimensional (3D) printing and milling technologies have dramatically increased the precision of implant surgery. Use of these advanced techniques has resulted in shorter surgeries, more precise implant positioning and, ultimately, more accurate interim and final prostheses. In turn, this increases the predictability and long-term success of implant therapy.
DWB: Advances in implant design, materials, and surface characteristics have all positively impacted implant success. This is true as it relates to the fixed hybrid prosthesis and its supporting implants, as well.
Innovations in software that work harmoniously with 3D radiographic imaging allow practitioners to plan these cases with greater ease and accuracy than in the past. Numerous options now exist that permit multidisciplinary treatment planning with both practitioners and dental laboratories. The process has become more streamlined and accurate. Ultimately, all of these factors contribute to more accurate and predictable outcomes.
Long-term implant success is enhanced by attached keratinized gingiva
In cases that allow a choice, which factors might influence the decision to use a telescopic coping or screws to retain the prosthesis? Similarly, what circumstances would dictate the use of only one approach?
TAC: To large degree, this involves patient preference. Telescopic restorations are custom fabricated and picked up inside the prosthesis chairside. The copings (Figure 1) seat over the abutments and allow simplified removal and replacement of the prosthesis so it can easily be maintained by the patient and dental team. Compared to other retention methods, telescopic copings require less follow-up care and avoid additional fees, such as replacing screws at periodic recalls. However, if the patient is opposed to anything removable, then a screw-retained prosthesis would be indicated.
DWB: The choice of restorative approach is often multifactorial. The traditional hybrid prosthesis requires a defined amount of inter-arch space to accommodate the restorative materials. Other full-arch prosthetic options, such as CAD/CAM discs and blocks made of multi-directional, multi-layered interlacing of fiberglass and resin, can be retained with telescopic copings and require less inter-arch space. This is significant, as the amount of alveolar bone removal differs based on the amount of restorative material required.
Another consideration is that the cost of these options may differ, which could point the patient toward one or the other. And, clinically, the patient’s risk assessment may dictate that a less invasive option is required. In these cases, a CAD/CAM block prosthesis may be indicated over a hybrid design.
How can clinicians best avoid complications?
TAC: Proper case selection, along with ensuring adequate hard and soft tissues, will allow a prosthetic design that provides a passive appliance with balanced occlusal forces. Additionally, to ensure long-term success, the patient and dental team must perform regular maintenance of the implants and prosthesis.
Finally, it is important to set patients’ expectations so they understand they won’t have dentate problems any longer, but they can still experience wear and tear, and also develop implant and prosthetic issues without continued care and maintenance.
DWB: Proper patient selection through an exhaustive work-up is the best way to avoid or minimize complications. Treating practitioners must have a good working understanding of the principles that drive implant success. A lack of understanding of the fundamentals and/or failure to apply these principles will lead to poor outcomes.
Dentists who are interested in this treatment option should seek out qualified courses to gain the essential knowledge needed to provide successful implant therapy. They should also build a cohesive treatment team that consists of a restorative doctor, surgeon, and, in many cases, laboratory technician. The team members must be equally knowledgeable of the treatment process, and they must have effective communication and work well together in order to ensure optimal outcomes.
- Patients with terminal dentitions and removable prostheses lend themselves to all-on-four treatment.
- A thorough review of the patient’s dental, medical and surgical history, as well as a careful assessment of risk factors, and evaluation of the hard and soft tissues, are the foundation of successful implant treatment.
- In a patient with a severely atrophic maxilla or mandible, treatment options differ for each location: Zygomatic implants may be employed in the maxilla, whereas in the mandible short implants may be an option.
- The assessment and planning phases of dental implant therapy should also consider the patient’s expectations. The clinical team needs to ensure that realistic expectations are in place.
- A fixed hybrid restoration is the option that will return edentulous patients to a level of function that most closely approximates their lost dentition.
- Advances in implant design, materials, and surface characteristics have all positively impacted the success of implant therapy — as have innovations in digital dental technologies.
- Cone beam imaging, digital design software, and three-dimensional printing and milling technologies have dramatically increased the precision of implant surgery.
- Use of these advanced techniques has resulted in shorter surgeries, more precise implant positioning and, ultimately, more accurate interim and final prostheses.
- In turn, these innovations support the predictability and long-term success of dental implant therapy.
From Decisions in Dentistry. December 2021;7(11)12-14.