Fundamentals of Treatment Planning. Lino Calvani
disease conditions and related health problems that involve both the young and the elderly worldwide, even today.51
Although there is a large body of scientific literature about them, clinical experience shows that in many instances CDs still remain very difficult to create and craft properly. However, if the literature is carefully studied and scientific engineering rules are strictly followed, the construction of CDs can result in a successful restoration. Experience shows that the obvious weakness in these prostheses is their mobility.52,53 In this respect, they must necessarily rely on the remaining available maxillary and mandibular primary and secondary bearing areas and on the characteristics of the hard and soft tissue comprising these areas. Their success also relies on a number of other biological, physical, chemical, and subjective factors that have been widely described in the literature. Regardless of whether they are created in an analog or digital manner, the nature of CDs makes these prostheses biomechanically lacking in terms of stability, retention, and support compared with other fixed prostheses. Nevertheless, many patients lack the economic resources for fixed implant treatments, and many in fact do live with CDs satisfactorily and sometimes more than satisfactorily, which compensates for their biologic limitations.52-70
In cases where up-to-date, three-dimensional (3D) digital technologies can be used to virtually plan the rehabilitation of edentulous cases with immediate implant-supported fixed prostheses, CDs can be used as excellent interim prostheses, as useful verification jigs, and as surgical guides to position implants properly to recreate final full-arch implant restorations.
In fact, when all anatomical dental reference points are lost, CDs are a precious source of anatomical information and can be used to recover most of these points in any edentulous mouth. In these cases, lip and cheek support, dental esthetics, phonetic and functional landmarks, and all occlusal parameters necessary to properly guide the oral rehabilitation with excellent approximation can be retrieved both in the mouth and on the working casts. This also depends on the knowledge and clinical skills of the clinician and the laboratory technician to replace the lost dentition with final fixed implant-supported prostheses.
Indeed, the advent of implants helped to improve this unstable situation. However, if structurally valid roots still remain in strategic positions in the mandible (ie, canines or first premolars), they can be reconstructed and utilized to support, retain, and stabilize any complete denture prosthesis. This possibility is cheaper than the use of implants, and biomechanical improvement can be better achieved by means of fixed attachments, as they may limit the number of biomechanical degrees of freedom to the mobility of the overlying CDs both at rest and during function. Certainly, the choice to save and use the roots is limited by a number of structural and biomechanical parameters that must be carefully evaluated during the first visit and during treatment planning.71-82
Mandibular implant overdentures can be obtained with two implants positioned in strategic positions. In these cases, the further use of bars or attachments as a means of anchoring may greatly enhance the stability, retention, and support of these types of prostheses.83-94 This combination has been defined as optimal and as the standard of care for mandibular CDs.95-97
In the maxilla, usually the greater extension and the quality of the bearing surface guarantee better support, stability, and retention. However, in the following instances implants might also be proposed to create maxillary implant overdentures: when the amount of alveolar ridge bone is poor; when the palate is particularly flat and induces instability; when the posterior palatal seal cannot be properly achieved and is not enough to aid the retention; and when the patient is suffering from xerostomia, which induces instability, inflammation, and poor retention of the denture base.30
Full-arch implant-retained fixed prostheses
These prostheses can be optimal in the restoration of all partial and fully edentulous cases. Limiting factors to this prosthetic choice may be the patient’s chief complaint restrictions, specific negative general health conditions, predictable increased clinical and technical costs, and local limiting factors such as the possible moderate to severe bone conditions that may not withstand further long and complex bone regeneration and implant treatment procedures.31-33,49,98 For more than three decades, this prosthetic tool has become the primary prosthodontic treatment option, offering the best quasi-natural improved restoration of complete edentulous arches with various types of fixed prostheses with the highest degree of success. Certainly, the most important rule for success in implant therapy is the presence of highly qualified and proficient prosthodontists and clinical and laboratory staff who perform all phases of the restoration, from the initial treatment planning phase, in a scientifically correct way.27,99-101 This professionalism is an ethical and practical must, because the challenge to plan and create implant prostheses always contains a large number of variables that are not always easy to keep under control unless one is knowledgeable and highly experienced.31,102 To this end, a description of many limitations and prerequisites for implant choices useful for brainstorming purposes as well as for the practice of treatment planning are reported in Chapter 10.
Bioinformatics and the digital prosthodontics paradigm shift
In the present era of computers, all areas of our lives are constantly becoming more and more digitized. We can only imagine what the reality will look like in 10 years’ time in the medical and dental medical professions as we attempt to grasp day by day just a small part of what thousands of extremely gifted scientists are creating. There are many impressive bioinformatic possibilities at present to store data and exploit in-office computer processing capabilities. Large databases are immediately available on the internet for the easy retrieval of precise information. This is changing the face of the dental medical profession forever, which is true for all dental specialist fields but perhaps more so for prosthodontics. The following section elaborates on a topic that was outlined in Chapter 1 and which is continually developing. The recent growth in digital technologies has introduced computer-aided implantology that has allowed for computer-aided prosthetic designing and planning and precise guided implant positioning.14,26,101,103,